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325 Controller

1. 2 5 2 3 7 IE rese e Too 2 6 2 3 8 Heat Sinking L eads inet RR eed de Ede oe eed d 2 6 2 3 9 Thermal 2 6 24 HEATER SELECTION AND 5 nennen nennen enter enne 2 6 2 4 1 Heater Resistance and Power needed deese de dre eee aede ie nee Eee ere nes 2 6 2 4 2 Heater Location a E ee ee 2 7 2 4 3 a Jd cp 2 7 2 4 4 azione 2 7 2 5 CONSIDERATIONS FOR GOOD CONTROL seen 2 7 2 5 1 Thermal 7 2 7 2 5 2 Thermal Lag EN 2 7 2 5 3 anata Mei bate A Ae AE MAUR el ae e a 2 7 2 5 4 dei petet toco ee ines adhoc dedere le oet ce erede 2 8 2 5 5 SystemiNonlinearity gs B ee e Rodda A Genes iren ix e COP EUR e gesta 2 8 2 6 TREE 2 8 2 6 1 Proportional etr eI E Pee Wine 2 8 2 6 2 Integral gu ee nee a Ae 2 9 2 6 3 DOT RE 2 9 2 6 4 Manual Heater Power MHP 2 9 2 7 MANUAL Rm 2 11 2 7 1 Setting Heater Range
2. 0 000K Proportional P 50 0 Integral T sss 20 0 Derivative 0 00 Manual 0 000 Operation 4 27 Lake Shore Model 325 Temperature Controller User s Manual This Page Intentionally Left Blank 4 28 Operation Lake Shore Model 325 Temperature Controller User s Manual CHAPTER 5 ADVANCED OPERATION 5 0 GENERAL This chapter provides information on the advanced operation of the Model 325 temperature controller 5 1 CURVE NUMBERS AND STORAGE The Model 325 has 20 standard curve locations numbered 1 through 20 At present not all locations are occupied by curves the others are reserved for future updates Ifa standard curve location is in use the curve can be viewed using the edit operation Standard curves cannot be changed by the user and reserved locations are not available for user curves The Model 325 has 15 user curve locations numbered 21 through 35 Each location can hold from 2 to 200 data pairs breakpoints including a value in sensor units and a corresponding value in kelvin Using fewer than 200 breakpoints will not increase the number of available curve locations SoftCal generated curves are stored in user curve locations 5 1 1 Curve Header Parameters Each curve has parameters that are used for identification and to allow the instrument to use the curve effe
3. 3 5 3 4 7 Lowering Measurement dun 3 6 3 5 THERMOCOUPLE SENSOR INPUTS 3 6 3 5 1 Sensor Input Terminals teet Een tpi 3 6 3 5 2 Thermocouple enne nnns 3 7 3 5 3 Grounding and Shielding 2 122r iret Ln ede dice dele tud ee dep e dene ne Done 3 7 3 6 HEATER OUTPUT SETUP coh tent Ee te eere a tei tee et leet e de 3 7 3 6 1 Loop 1 Output x daca bo ha Alan SESS aer pese ius 3 7 3 6 2 Loop 1 Heater Output Connector deciden deter ER ie 3 7 3 6 3 Loop 1 Heater Output Wiring eiie cite qne ete ple ERU eda ier 3 7 3 6 4 Eoop 1 Heater Output NoOlse 1 1 tette E 3 8 3 6 5 Loop 2 O Utpul e ipe Sen A Ve ec VE Re Ee Lp eee e Pr pet Me 3 8 3 6 6 Loop 2 Output Resistance 1 o cer 3 8 3 6 7 Loop 2 Output Connector 5 nui etri tueri I Ea 3 8 3 6 8 1 00 2 epe 3 8 3 6 9 Boosting the Output 3 8 3 7 INITIAL SETUP AND SYSTEM CHECKOUT 3 9 4 OPERATION ueteri 4 1 4 0 GENERAL ieri in sin en E
4. Table D 1 Curve 02 DT 670 Silicon Diode sees Table D 2 Curve 03 amp 04 DT 500 D E1 Silicon Table D 3 Curve 06 amp 07 PT 100 1000 Platinum Table D 4 Curve 08 RX 102A 1 2022 4 0 000 000000000 Table D 5 Curve 09 RX 202A 22 0 4 00 00 Table D 6 Curve 12 Type Thermocouple sse Table D 7 Curve 13 Type E Thermocouple sse Table D 8 Curve 14 Type T Thermocouple sse Table D 9 Curve 15 Chromel AuFe 0 03 Thermocouple Table D 10 Curve 16 Chromel AuFe 0 07 Thermocouple Table D 11 Table D 1 Lake Shore DT 470 Silicon Diode Curve 10 per Temp K Volts Temp K Volts picis Temp K Volts 1 475 0 0 09062 30 170 0 0 82405 59 031 0 1 10476 2 470 0 0 10191 31 160 0 0 84651 60 030 0 1 10702 3 465 0 0 11356 32 150 0 0 86874 61 029 0 1 10945 4 460 0 0 12547 33 145 0 0 87976 62 028 0 1 11212 5 455 0 0 13759 34 140 0 0 89072 63 027 0 1 11517 6 450 0 0 14985 35 135 0 0 90161 64 026 0 1 11896 7 445 0 0 16221 36 130 0 0 91243 65 025 0 1 12463 8 440 0 0 17464 37 125 0 0 92317 66 024 0 1 13598 9 435 0 0 18710 38 120 0 0 93383 67 023 0 1 15558 10 430 0 0 19961 39 115 0 0 94440 68 022 0 1 17705 11 420 0 0 22463 40 110 0 0 95487 69 021 0
5. sns s 2 11 2 7 2 Tuning ireieoeu rl 2 11 2 7 3 Regen 2 12 2 74 TUNING EDI EE 2 12 2 8 AUTOTUNIN G EM 2 12 2 9 ZONEPTUNINQG E EET e eate Eth db eii ne 2 13 Table of Contents Lake Shore Model 325 Temperature Controller User s Manual TABLE OF CONTENTS Continued Chapter Section Title Page 3 INSTALLAT ON Peso 3 1 3 0 GENERAL 5 e niteat ea itis e bei eei UU eet 3 1 3 1 INSPECTION AND 7 3 1 3 2 REAR PANEL DEFINITION 0 20 tee eee 3 2 3 3 LINE INPUT ASSEMBLY ana nee aie ee 3 3 3 3 1 Line Voge 3 3 3 3 2 Line aeaa pai o aaeineiiaeaiiy 3 3 3 3 3 lue iae mp S 3 3 3 3 4 POWer SWIGCh e eter tac ERREUR REED 3 3 3 4 DIODE RESISTOR SENSOR 5 3 4 3 4 1 Sensor Input Connector and PINOUT nene nennen nnne enne 3 4 3 4 2 Sensor bead Cable nerd d Reti ee iE e t lier et 3 4 3 4 3 Grounding and Shielding Sensor Leads sse eene rennen 3 5 3 4 4 oensor Pol rity art ertet edet eti tee 3 5 3 4 5 Four Lead Sensor Measuremient ires ette teret epit 3 5 3 4 6 Two Lead Sensor Measurement tonitru
6. nte 8 16 8 12 6 Calibration Specific Interface 8 17 APPENDIX A GLOSSARY OF A 1 APPENDIX B TEMPERATURE SCALES 5 sanan ceti deca reed B 1 APPENDIX C HANDLING OF LIQUID HELIUM AND nnne nnne nnne nnn nnne nnn C 1 APPENDIX D CURVE TABLES tee ate ete ee etes eie D 1 Table of Contents Figure No 1 1 1 2 2 1 2 2 2 3 3 1 3 2 3 3 3 4 4 1 4 2 4 3 4 4 5 1 5 2 6 1 6 2 6 3 6 4 6 5 6 6 7 1 7 2 7 3 7 4 8 1 8 2 8 3 8 4 8 5 8 6 8 7 8 8 B 1 C 1 Lake Shore Model 325 Temperature Controller User s Manual LIST OF ILLUSTRATIONS Title Page Model 325 Front VIew ee P ea alien 1 1 Model 325 Rear Panel 2 e icio a Henne de Lo diera 1 2 Silicon Diode Sensor Calibrations and 2 3 Typical Sensor Installation In A Mechanical Refrigerator essen eee 2 5 Examples of et aer 2 10 Model 325 Rear Panel ee ee e e A e eoque ee 3 2 Line Iniput Assetnbly a ie Hee eve deerit 3 3 Diode Resistor Input 22
7. Input Returned Remarks RST Input Remarks SRE Input Format Remarks Example SRE Input Returned Format STB Input Returned Format Remarks Lake Shore Model 325 Temperature Controller User s Manual Operation Complete Command OPC term Generates an Operation Complete event in the Event Status Register upon completion of all pending selected device operations Send it as the last command in a command string Operation Complete Query OPC term 1 term Places a 1 in the controller output queue upon completion of all pending selected device operations Send as the last command a command string Wofthe same as Reset Instrument Command RST term Sets controller parameters to power up settings Service Request Enable Register Command SRE lt bit weighting gt term nnn Each bit has a bit weighting and represents the enable disable mask of the corresponding status flag bit in the Status Byte Register To enable a status flag bit send the command SRE with the sum of the bit weighting for each desired bit Refer to Section 6 1 4 2 for a list of status flags To enable status flags 4 5 and 7 send the command SRE 208 term 208 is the sum of the bit weighting for each bit Bit Bit Weighting Event Name 4 16 MAV 5 64 ESB 7 128 OSB 208 Service Request Enable Register Query SRE term lt bit weighting gt term n
8. Range Voltage Reference Output Reference Voltage Known To Cal Command Type Number Silicon Diode 2 5 VDC 0 00010 VDC 0 GaAlAs Diode 7 5 VDC 0 00040 VDC 1 Service 8 13 Lake Shore Model 325 Temperature Controller User s Manual 8 12 2 4 Resistive Input Ranges Calibration Purpose To determine the input offset and gain errors when the input is configured for the resistive ranges and provide offset and gain calibration constants back to the Model 325 This step will calibrate all resistive ranges with reversing both on and off Process 1 Configure the input for the resistive range to be calibrated 2 Reset the calibration constants to their default values using the CAL Z and CALG commands EXAMPLE Input A Range 100Q Plat 250 Reversal Off Zero Offset Command CALZ A 2 0 Gain Command CALG A 2 1 3 Short all four terminals I V of the input together do not tie the terminals to ground Via the interface obtain the input reading using the CALREAD command and record this number 5 Program the offset calibration by negating the value read in the previous step and providing it using the CALZ command EXAMPLE Input A Range 100Q Plat 250 Reversal Off CALREAD Reading 000 003 Calibration Command CALZ A 2 0 003 6 From Table 8 2 select the calibration resistor for the range being calibrated and use the DMM in 4 lead resistance measurement mode to measure
9. NOTE Ifany problems appear immediately press the Heater Off key If any error messages are displayed The refer to Section 8 11 for details Model 325 should now be controlling the temperature in the experimental setup at the setpoint temperature Once this initial checkout procedure is successfully completed the unit is ready for normal operation We recommend all users thoroughly read Chapter 4 Operation before attempting to use the Model 325 in an actual experiment or application 3 10 Installation Lake Shore Model 325 Temperature Controller User s Manual CHAPTER 4 OPERATION 4 0 GENERAL This chapter provides instructions for the general operating features of the Model 325 Temperature Controller Advanced operation is in Chapter 5 Computer interface instructions are in Chapter 6 41 FRONT PANEL DESCRIPTION This section provides a description of the front panel controls and indicators for the Model 325 4 1 1 Keypad Definitions An abbreviated description of each key is provided as follows A more detailed description of each function is provided in subsequent sections See Figure 4 1 AutoTune Allows selection of closed loop tuning mode AutoTune PID PI P Manual PID or Zone for the currently selected loop Refer to Section 4 9 Loop Toggles the front panel display and key functions between Loop 1 and 2 Operates with Control Setup Setpoint PID MHP Zone Settings AutoTune Heater Range and Heate
10. fe n he 4 24 4 14 HEATER RESISTANCE SETTING wy rene ea Ege dn ee Ret e eee ets 4 24 4 15 LOCKING AND UNLOCKING THE 4 25 4 16 REMOTE FOGAL 5 pensat ree cette ect tate EH IR das ee duod 4 25 4 17 4 25 4 18 DEFAULT VALUES zr rere 4 26 5 ADVANCED 2 5 1 5 0 GENERAL 5 1 5 1 CURVE NUMBERS AND 5 5 1 5 1 1 Curve Header Parameters 5 1 5 1 2 Curve Breakpoints roe greet peteret pere prex ve 5 1 5 2 FRONT PANEL CURVE ENTRY OPERATIONS sese enne nennen enne rennen 5 3 5 2 1 Edit CUVE 5 3 5 2 1 1 Thermocouple Curve 5 5 5 2 2 5 ciate a AA RELIER T aa a 5 5 5 2 3 COPY aE E E A T 5 6 5 3 lemen MEE 5 6 5 3 1 SoftCal With Silicon Diode 5 7 5 3 2 SoftCal Accuracy With Silicon Diode 5 7 5 3 3 SoftCal With Platinum 5 5 8 5 3 4 SoftCal Accuracy With Platinum Sensors eene nennen 5 8 5 3 5 So
11. Apiezon N Grease 25 g Tube General purpose grease well suited for cryogenic use because of its low viscosity It is often used as a means of thermally anchoring cryogenic sensors as well as lubricating joints and o rings Contains high molecular weight polymeric hydrocarbon additive that GAN 25 Pats 5 gives it a tenacious rubbery consistency allowing the grease to form a cushion between mating surfaces Melting point is 316 43 be removed using Xylene with an isopropyl alcohol rinse Accessories included with a new Model 325 7 2 Options and Accessories Lake Shore Model 325 Temperature Controller User s Manual Accessories Continued Description of Accessories Continued 25 Q Cartridge Heater The heater features precision wound nickel chromium resistance wire magnesium oxide insulation two solid pins non magnetic package and has UL and CSA component HTR 25 recognition The heater is 25 6 35 mm 0 25 in diameter by 25 4 mm 1 in long The 25 rating is in dead air With proper heat sinking the cartridge heater can handle many times this dead air power rating is in dead air With proper heat sinking the cartridge heater can handle many times this dead air power rating 325 Model 325 Temperature Controller User s Manual Half Rack Mounting Kit for One Model 325 Temperature Controller Half length mounting RM 1 2 panel and mounting ears to attach
12. Use the A or V key to select 25 or 50 Q Press the Enter key to save changes and return to the normal display 4 24 Operation Lake Shore Model 325 Temperature Controller User s Manual 4 15 LOCKING AND UNLOCKING THE KEYPAD The keypad lock feature prevents accidental changes to parameter values When the keypad is locked some parameter values may be viewed but most cannot be changed from the front panel Heater Off is the only keypad function that remains active when the keypad is locked A 3 digit keypad lock code locks and unlocks the keypad The factory default code is 123 The code can be changed only through the computer interface If instrument parameters are reset to default values the lock code resets also The instrument cannot reset from the front panel with the keypad locked To lock the keypad press and hold the Enter key for 10 seconds to display the screen shown as follows Use the numeric keypad to enter the 3 digit lock code The keypad locks and the normal display appears Changes attempted to any parameters result in brief display of the LOCKED message To unlock the keypad press and hold the Enter key for 10 seconds to display the screen shown as follows Use the numeric keypad to enter the 3 digit lock code The keypad unlocks and the normal display again appears All Model 325 parameters are now accessible 4 16 REMOTE LOCAL Local refers to operating the Mode
13. 13 8 12 3 Diode Sensor Input Calibration 1 mA Excitation Current The instrument uses the calibration constants determined in the Diode Input Ranges Calibration Section 8 12 2 3 for the diode ranges that use 1 mA excitation Therefore no additional calibration is necessary NOTE Standard diode curves and typical sensor performance Table 1 2 are calculated using 10 uA excitation Sensor temperature response characteristics will be altered if 1 mA excitation is selected 8 12 4 Thermocouple Sensor Input Calibration Overview Each thermocouple sensor input requires calibration The sensor inputs contain multiple gain stages to accommodate the various thermocouple sensors the Model 325 supports The input circuitry is not adjusted during calibration Instead precision voltages are supplied to each input and mathematical calibration constants are calculated and programmed into the Model 325 Constants are stored to compensate for both input offset and gain errors Thermocouple inputs do not use the current source Calibration Process 8 9 4 1 Sensor Input Calibration Setup Allow the Model 325 to warm up for at least 1 hour with shorts placed across all thermocouple sensor inputs If calibrating a dual thermocouple Model 325 leave a short across the input not currently being calibrated If the other input 1s diode resistor place 100 resistor on the input CAUTION All thermocouple connections must be tigh
14. 6 24 MODE Query Local Remote Mode 6 30 XTST Self Test Query xtti 6 25 MOUT Control Loop MHP Output Cmd 6 31 KWAI Wait To Continue Cmd 6 25 MOUT Control Loop MHP Output Query 6 31 CMODE Control Loop Mode 6 25 PID Control Loop PID Values Cmd 6 31 CMODE Control Loop Mode Query 6 25 PID Control Loop PID Values Query 6 31 CRDG Celsius Reading Query 6 25 RAMP Control Loop Ramp 6 31 CRVDEL Delete User Curve Cmd 6 25 RAMP Control Loop Ramp Query 6 32 CRVHDR Curve Header 6 26 RAMPST Control Loop Ramp Status Query 6 32 CRVHDR Curve Header 6 26 RANGE Heater Range 6 32 CRVPT Curve Data Point Cmd 6 26 RANGE Heater Range 6 32 CRVPT Curve Data Point 6 26 RDGST Input Status 6 32 CSET Control Loop Parameter Cmd 6 27 REV Input Firmware Revision Query 6 33 CSET Control Loop Parameter Query 6 27 SCAL Generate SoftCal Curve Cmd 6 33 DFLT Factory Defaults 6 27 SETP Control Loop Setp
15. Figure 2 3 Examples of PID Control 2 10 Cooling System Design Lake Shore Model 325 Temperature Controller User s Manual 2 7 MANUAL TUNING There has been a lot written about tuning closed loop control systems and specifically PID control loops This section does not attempt to compete with control theory experts It describes a few basic rules of thumb to help less experienced users get started This technique will not solve every problem but it has worked for many others in the field This section assumes the user has worked through the operation sections of this manual has a good temperature reading from the sensor chosen as a control sensor and is operating Loop 1 It is also a good idea to begin at the center of the temperature range of the cooling system not close to its highest or lowest temperature AutoTune Section 2 8 is another good place to begin and do not forget the power of trial and error 2 7 1 Setting Heater Range Setting an appropriate heater output range is an important first part of the tuning process The heater range should allow enough heater power to comfortably overcome the cooling power of the cooling system If the heater range will not provide enough power the load will not be able to reach the setpoint temperature If the range is set too high the load may have very large temperature changes that take a long time to settle out Delicate loads can even be damaged by too much power Often there is li
16. Send CLS CLS clears both registers Power on instrument Enable Registers Standard Event Status Enable Register Operation Event Enable Register Service Request Enable Register Write 0 to the enable register ESE 0 clears Standard Event Status Enable register Power on instrument Status Byte There are no commands that directly clear the Status Byte as the bits are non latching to clear individual summary bits clear the event register that corresponds to the summary bit sending CLS will clear all event registers which in turn clears the status byte If bit 5 ESB of the Status Byte is set send ESR to read the Standard Event Status Register and bit 5 will clear Power on instrument Remote Operation 6 5 Lake Shore Model 325 Temperature Controller User s Manual 6 1 4 2 Status Register Sets As shown in Figure 6 1 there are two register sets in the status system of the Model 325 Standard Event Status Register and Operation Event Register 6 1 4 2 1 Standard Event Status Register Set The Standard Event Status Register reports the following interface related instrument events power on detected command syntax errors command execution errors query errors operation complete Any or all of these events may be reported in the standard event summary bit through the enable register see Figure 6 2 The Standard Event Status Enable command ESE programs the enab
17. Control Input Input A SP Units Temp K Control Mode Closed Power 0 Disable Setpoint Ramp Off Heater Output Display Current Display Format Display Location 1 Input A Temp K Display Location 2 Input B Temp K Display Location 3 Setpoint Display Location 4 Heater Output Heater Heater Range Off Input Setup Diode Resistor Configuration Input Type Silicon Diode CUIV Cs oet eure DT 470 Input Setup Thermocouple Configuration Input Type Thermocouple 25mV ine Room Comp On Room Cal Cleared Interface eem 9600 IEEE Address 12 IEEE Terminators CR LF Keypad Locking y Unlocked Lock Code 123 Loop Selected Loop Loop 1 PID Manual Heater Power MHP Output Proportional P 50 0 Integral 1 20 0 Derivative 0 0 MHP 0 000 Remote Local Remote Local Local Setpoint Setpoint Value 0 000K Tuning Tuning Manual PID Zone Settings All Zones Setpoint
18. Installation 3 7 Lake Shore Model 325 Temperature Controller User s Manual Loop 1 Heater Output Wiring continued There is a chassis ground point at the rear panel of the instrument for shielding the heater cable The cable shield can be tied to this point using a 4 spade or ring connector The shield should not be connected at the opposite end of the cable and should never be tied to the heater output leads For best noise performance do not connect the resistive heater or its leads to ground Also avoid connecting heater leads to sensor leads or any other instrument inputs or outputs 3 6 4 Loop 1 Heater Output Noise The heater output circuitry in the Model 325 must be capable of sourcing 25 W of power This type of circuitry can generate some electrical noise The Model 325 was designed to generate as little noise as possible but even noise that is a small percentage of the output voltage or current can be too much when sensitive measurements are being made near by If the Model 325 heater leads are too noisy and the above wiring techniques do not help Lake Shore offers the Model 3003 Heater Output Conditioner that may help Refer to Section 7 4 3 6 5 Loop 2 Output The Model 325 has a second control loop called Loop 2 Loop 2 is an auxiliary control loop with the capability of powering a small sample heater or controlling a larger programmable heater power supply Loop 2 has a different output from Loop 1 it uses analog voltage
19. The Model 325 will display the heater output as either percent of full scale current or percent of full scale power for the heater range selected This parameter affects the heater output display and the scale of the Manual Heater Power MHP output parameter for Loop 1 The MHP Output scale is always the same as the control output display To change control output units press the Control Setup key and press Enter until the following display appears Use the A or V key to toggle between Heater Out Power and Current Press the Enter key 4 8 MANUAL TUNING Closed Loop PID Control In manual PID mode the controller will accept user entered Proportional Integral and Derivative parameters to provide three term PID control Manual heater power output can be set manually in open loop and closed loop control modes For details on PID tuning refer to Section 2 7 To place the controller in Manual PID tuning mode press the Auto Tune key and press the or key until you see the following display Press the Enter key The controller is now in Manual PID mode 4 8 1 Manually Setting Proportional P The proportional parameter also called gain is the P part of the PID control equation It has a range of 0 to 1000 with a resolution of 0 1 Enter a value greater than zero for P when using closed loop control To set Proportional press the P key You will see the following display The Proportional
20. User s Manual Model 325 Temperature Controller Local Range 8 Heater qa Zone terface x on 4 5 6 x 1 2 3 4 325 Temperature Controller Set 5 2 d akeShore Lake Shore Cryotronics Inc 575 McCorkle Blvd Westerville Ohio 43082 8888 USA E mail addresses sales lakeshore com service lakeshore com Visit our website at www lakeshore com Fax 614 891 1392 Telephone 614 891 2243 Methods and apparatus disclosed and described herein have been developed solely on company funds of Lake Shore Cryotronics Inc No government or other contractual support or relationship whatsoever has existed which in any way affects or mitigates proprietary rights of Lake Shore Cryotronics Inc in these developments Methods and apparatus disclosed herein may be subject to U S Patents existing or applied for Lake Shore Cryotronics Inc reserves the right to add improve modify or withdraw functions design modifications or products at any time without notice Lake Shore shall not be liable for errors contained herein or for incidental or consequential damages in connection with furnishing performance or use of this material Revision 1 4 P N 119 041 15 February 2011 Lake Shore Model 335 Temperature Controller User s Manual LIMITED WARRANTY STATEMENT WARRANTY PERIOD ONE 1 YEAR 1 Lake Shore warrants that this Lake Shore product the Product will be free from defect
21. V V of the input together do not tie the terminals to ground Via the interface obtain the input reading using the CALREAD command and record this number Program the offset calibration by negating the value read in the previous step and providing it using the CALZ command EXAMPLE Input A Range GaAlAs Diode CALREAD Reading 0 00005 Calibration Command CALZ A 1 0 00005 Disconnect the V terminal from the others and connect to the positive output of the voltage reference Connect the voltage reference negative output to the V I and I terminals Set the voltage reference to provide the calibration voltage shown in Table 8 1 Using the DMM measure the voltage to the tolerance shown in Table 8 1 Via the interface obtain the input reading using the CALREAD command and record this number Program the gain calibration by dividing the measured value of the reference voltage by the value read in the previous step and provide the result using the CALG command Note that the gain calibration constant will always be within 5 of 1 00000 EXAMPLE Input A Range GaAlAs Diode Measured Value of Reference Voltage 7 50002 VDC CALREAD Reading 7 49852 Constant Calculation 7 50002 7 49852 1 00020 Calibration Command CALG A 1 1 00020 10 Send the CALSAVE command to save the constants in the EEPROM 11 Perform calibration on both diode ranges Table 8 1 Calibration Table for Diode Ranges
22. s Manual Table D 9 Type T Copper vs Copper Nickel Thermocouple Curve bm mV Temp K Pu mV Temp K m mV Temp K 1 6 257510 3 15 56 5 424100 84 00 111 0 623032 289 00 2 6 257060 3 56 57 5 380600 86 50 112 0 843856 294 50 3 6 256520 4 00 58 5 336260 89 00 113 1 067190 300 00 4 6 255810 4 50 59 5 291080 91 50 114 1 293090 305 50 5 6 254950 5 04 60 5 245070 94 00 115 1 521570 311 00 6 6 253920 5 62 61 5 188800 97 00 116 1 752660 316 50 J 6 252780 6 20 62 5 131290 100 00 117 1 986340 322 00 8 6 251380 6 85 63 5 072630 103 00 118 2 222600 327 50 9 6 249730 7 55 64 5 012780 106 00 119 2 461410 333 00 10 6 247810 8 30 65 4 951770 109 00 120 2 702740 338 50 11 6 245590 9 10 66 4 889610 112 00 121 2 946550 344 00 12 6 243040 9 95 67 4 826300 115 00 122 3 192800 349 50 13 6 240300 10 80 68 4 761840 118 00 123 3 441440 355 00 14 6 237210 11 70 69 4 696250 121 00 124 3 715300 361 00 15 6 233710 12 65 70 4 629530 124 00 125 3 991980 367 00 16 6 229800 13 65 71 4 561670 127 00 126 4 271300 373 00 17 6 225630 14 65 72 4 492700 130 00 127 4 553250 379 00 18 6 221000 15 70 73 4 422610 133 00 128 4 837770 385 00 19 6 215860 16 80 74 4 351390 136 00 129 5 148790 391 50 20 6 210430 17 90 75 4 266950 139 50 130 5 462770 398 00 21 6 204430 19 05 76 4 180930 143 00 131 5 779560 404 50 22 6 198680 20 10 77 4 093440 146 50 132 6 099160 411 00 23 6 191780 21 30 78 4 004430 150 00 133 6 421500 417 50 24 6 184530 2
23. will clear the message available bit The bits of the Status Byte Register are described as follows Operation Summary OSB Bit 7 Set summary bit indicates that an enabled operation event has occurred Request Service R QS Master Summary Status MSS Bit 6 This bit is set when a summary bit and the summary bits corresponding enable bit in the Service Request Enable Register are set Once set the user may read and clear the bit in two different ways which is why it is referred to as both the 5 and the MSS bit When this bit goes from low to high the Service Request hardware line on the bus is set this is the RQS function of the bit Refer to Section 6 1 4 3 3 In addition the status of the bit may be read with the STB query which returns the binary weighted sum of all bits in the Status Byte this is the MSS function of the bit Performing a serial poll will automatically clear the RQS function but not the MSS function A STB will read the status of the MSS bit along with all of the summary bits but also will not clear it To clear the MSS bit either clear the event register that set the summary bit or disable the summary bit in the Service Request Enable Register Event Summary ESB Bit 5 Set summary bit indicates that an enabled standard event has occurred Message Available M AV Bit 4 Set summary bit indicates that a message is available in the output buffer Remote Operation 6 7 Lake Shore
24. 179 67 117 59 340 206 67 171 67 113 15 339 67 206 48 170 112 22 333 67 203 15 169 67 112 04 330 201 11 166 110 329 67 200 93 160 106 67 328 200 159 67 106 48 320 195 56 153 67 103 15 319 67 195 37 150 101 11 315 67 193 15 149 67 100 93 310 190 148 100 309 67 189 82 140 95 96 300 184 44 139 67 95 37 299 67 184 26 135 67 93 15 297 67 183 15 130 90 2 Temperature Scales Lake Shore Model 325 Temperature Controller User s Manual APPENDIX C HANDLING LIQUID HELIUM AND NITROGEN C1 0 GENERAL Use of liquid helium LHe and liquid nitrogen LN is often associated with the Model 325 temperature controller Although not explosive there a number of safety considerations to keep in mind in the handling of LHe and LN gt C2 0 PROPERTIES LHe and LN are colorless odorless and tasteless gases Gaseous nitrogen makes up about 78 percent of the Earth s atmosphere while helium comprises only about 5 ppm Most helium 18 recovered from natural gas deposits Once collected and isolated the gases will liquefy when properly cooled A quick comparison between LHe and LN is provided in Table C 1 Table C 1 Comparison of Liquid Helium and Liquid Nitrogen PROPERTY LIQUID HELIUM LIQUID NITROGEN Boiling Point at 1 atm in 77 Thermal Conductivity Gas w cm K 0 013 Latent Heat of Vaporization Btu L 152 Liquid Density Ib L 0 78 C3 0 HANDLING CRYOGENIC STORAG
25. 6 34422 33 1 80 4 55845 137 5 127 8 15226 473 5 174 43 6853 1335 5 34 6 33408 34 5 81 4 48056 140 5 128 8 75291 488 5 175 44 2394 1350 35 6 3235 35 9 82 4 38814 144 129 9 25576 501 176 44 7721 1364 36 6 3117 374 83 4 29393 147 5 130 9 74087 513 177 45 3024 1378 37 6 29939 38 9 84 4 19806 151 131 10 2285 525 178 45 8114 1391 5 38 6 2866 40 4 85 4 10051 154 5 132 10 7186 537 179 46 3182 1405 39 6 27241 42 86 4 00133 158 133 11 2317 549 5 180 46 8038 1418 40 6 25768 43 6 87 3 90053 161 5 134 11 7883 563 181 47 2873 1431 41 6 24239 45 2 88 3 79815 165 135 12 3888 577 5 182 47 7684 1444 42 6 22656 46 8 89 3 6942 168 5 136 13 054 593 5 183 48 2287 1456 5 43 6 21019 48 4 90 3 58873 172 137 13 7844 611 184 48 6868 1469 44 6 19115 50 2 91 3 46638 176 138 14 5592 629 5 185 49 1426 1481 5 45 6 17142 52 92 3 34204 180 139 15 3786 649 186 49 5779 1493 5 46 6 15103 53 8 93 3 21584 184 140 16 2428 669 5 187 50 0111 1505 5 47 6 12998 55 6 94 3 08778 188 141 17 1518 691 D 6 Curve Tables Lake Shore Model 325 Temperature Controller User s Manual Table D 8 Type E Nickel Chromium vs Copper Nickel Thermocouple Curve p mV Temp K Som mV Temp K Soin mV Temp K 1 9 834960 3 15 55 8 713010 77 50 109 0 701295 285 00 2 9 834220 3 59 56 8 646710 80 00 110 1 061410 291 00 3 9 833370 4 04 57 8 578890 82 50 111 1 424820 297 00 4 9 832260 4 56 58 8 509590 85 00 112 1 791560 303 00 5 9 83
26. Begin this part of the tuning process with the system controlling in proportional only mode Use the oscillation period of the load that was measured above in seconds Divide 1000 by the period to get the integral setting Enter the integral setting into the Model 325 and watch the load temperature approach the setpoint If the temperature does not stabilize and begins to oscillate around the setpoint the integral setting is too high and should be reduced by one half If the temperature is stable but never reaches the setpoint the integral setting is too low and should be doubled To verify the integral setting make a few small 2 to 5 degree changes in setpoint and watch the load temperature react Trial and error can help improve the integral setting by optimizing for experimental needs Faster integrals for example get to the setpoint more quickly at the expense of greater overshoot In most systems setpoint changes that raise the temperature act differently than changes that lower the temperature If it was not possible to measure the oscillation period of the load during proportional setting start with an integral setting of 20 If the load becomes unstable reduce the setting by half If the load is stable make a series of small two to five degree changes in the setpoint and watch the load react Continue to increase the integral setting until the desired response is achieved 2 7 44 Tuning Derivative If an experiment requires frequent ch
27. EHS C k c DE CR Come Come 69 fase 011 ru BB glatte m p E El m P 325 8 7 bmp Figure 8 8 Location Of Internal Components Service 8 10 Lake Shore Model 325 Temperature Controller User s Manual 8 12 CALIBRATION PROCEDURE The Model 325 requires calibration of both of the sensor inputs and loop 2 heater output to operate within specification None of the other circuits require calibration The sensor inputs may be configured as diode resistor or thermocouple and the calibration process differs for each This procedure contains instructions for both input types Refer to Section 8 12 6 for details on calibration specific interface commands 8 12 1 Equipment Required for Calibration PC and Interface PC with software loaded which provides serial command line communication Example program in Section 6 2 7 is ideal for this purpose DE 9 to DE 9 cable Pin to pin connections on all 9 pins Female connectors on both ends DE 9 null modem adapter Test and Measurement Equipment Digital multimeter DMM with minimum of 6 digits resolution DMM DC voltage and 4 lead resistance specifications to be equivalent to or better than HP 34584 specifications Precision reference providing up to 7 5 V with 1 mV resolution for diode resistor input calibration Precision reference providing up to 50 mV with 1 resolution for thermocouple input calibration
28. False End Sub Routine to handle Timer interrupt Turn off timer Remote Operation 6 19 Lake Shore Model 325 Temperature Controller User s Manual 6 2 7 2 Program Operation Once the program is running try the following commands and observe the response of the instrument Input from the user is shown in bold and terminators are added by the program The word term indicates the required terminators included with the response ENTER COMMAND IDN Identification query Instrument will return a string identifying itself RESPONSE LSCI MODEL325 1234567 1 0 1 0 term ENTER COMMAND KRDG Temperature reading in kelvin query Instrument will return a string with the present temperature reading RESPONSE 273 15 term ENTER COMMAND RANGE 0 Heater range command Instrument will turn off the heater No response will be sent ENTER COMMAND RANGE Heater range query Instrument will return a string with the present heater range setting RESPONSE O term ENTER COMMAND RANGE 1 RANGE Heater range command followed by a query Instrument will change to heater Low setting then return a string RESPONSE 1 term with the present setting The following are additional notes on using either serial interface program e Ifyou enter a correctly spelled query without a nothing will be returned Incorrectly spelled commands and queries a
29. Floating point values have varying resolution depending on the type of command or query issued Remote Operation 6 21 Lake Shore Model 325 Temperature Controller User s Manual Table 6 9 Command Summary Command Function Page Command Function Page CLS Clear Interface Cmd 6 23 IEEE IEEE Interface Parameter Query 6 29 KESE Event Status Enable 6 23 INCRV Input Curve Number Cmd 6 29 KESE Event Status Enable Query 6 23 INCRV Input Curve Number Query 6 29 ESR Event Status Register Query 6 23 INTYPE Input Type Parameter Cmd 6 29 KIDN Identification 6 23 INTYPE Input Type Parameter Query 6 29 Operation Complete Cmd 6 24 KEYST Keypad Status Query 6 30 Operation Complete Query 6 24 KRDG Kelvin Reading Query 6 30 KRST Reset Instrument Cmd 6 24 LOCK Front Panel Keyboard Lock Cmd 6 30 5 Service Request Enable Cmd 6 24 LOCK Front Panel Keyboard Lock Query 6 30 5 Service Request Enable Query 6 24 MODE Set Local Remote Mode 6 30 5 Status Byte
30. For this example we will enter 77 K Press the Enter key NOTE IfPoint3 is not being used press the Enter key with both settings at their default value to complete the SoftCal calibration Use the numerical keypad to enter the measured data point at or near room temperature 305 K Temperatures outside the range of 200 350 K are not permitted For this example we will enter 0 51583 Press the Enter key The cursor will jump to the temperature reading Again use numerical keypad to enter the temperature at which the measurement was taken For this example we will enter 302 5 K Press the Enter key The new curve is automatically generated and you will return to the normal display You can check the new curve using the Edit Curve instructions in Section 5 2 1 The curve is not automatically assigned to either input so the new curve must be assigned to an input by the user 5 10 Advanced Operation Lake Shore Model 325 Temperature Controller User s Manual CHAPTER 6 COMPUTER INTERFACE OPERATION 6 0 GENERAL This chapter provides operational instructions for the computer interface for the Lake Shore Model 325 temperature controller Either of the two computer interfaces provided with the Model 325 permit remote operation The first is the IEEE 488 interface described in Section 6 1 The second is the serial interface described in Section 6 2 The two interfaces share a common set of commands detailed in Section 6 3 On
31. Setpoint Heater Range Off Low High Setpoint Heater Range Off Low High Setpoint Heater Range Off Low High Setpoint Heater Range Off Low High Figure 4 4 Record of Zone Settings C 325 4 4 bmp Operation 4 21 Lake Shore Model 325 Temperature Controller User s Manual 4 11 SETPOINT The control setpoint is the desired load temperature expressed in temperature or sensor units Use sensor units if no temperature response curve is selected for the sensor input used as the control channel The control setpoint has its own units parameter Set with the Control Setup key in Section 4 7 Control channel readings can display in any units Display units need not match setpoint units NOTE Ifa curve is not assigned to the control input control reverts to sensor units and the setpoint is set to the most current reading When changing setpoint units while the control loop is active the Model 325 converts the control setpoint to the new control units for minimal disruption in control output Setpoint resolution depends on sensor type and setpoint units With setpoint expressed in temperature setpoint resolution is 0 001 degree for setpoints below 100 and 0 01 for setpoints between 100 and 1000 In sensor units the setpoint resolution matches the display resolution for the sensor input type given in the specifications Section 1 2 The instrument allows a large setpoint range to
32. Stycast Epoxy 2850 Catalyst 9 20 packets 2 g each Stycast is a common highly versatile ES 2 20 nonconductive epoxy resin system for cryogenic use The primary use for Stycast is for vacuum feedthroughs or permanent thermal anchors Stycast is an alternative to Apiezon N Grease when permanent sensor mountings are desired Indium Solder Disks Quantity 10 Indium is a semi precious non ferrous metal softer than lead and extremely malleable and ductile It stays soft and workable down to cryogenic temperatures ID 10 XX Indium can be used to create solder bumps for microelectronic chip attachments and also as gaskets for pressure and vacuum sealing purposes 10 10 31 Indium Disks are 0 312 diameter 0 005 in 0 10 56 Indium Disks are 0 562 diameter x 0 005 in Indium Foil Sheets Quantity 5 When used as a washer between DT 470 CU silicon diode or other IF 5 temperature sensors and refrigerator cold stages indium foil increases the thermal contact area and prevents the sensor from detaching due to vibration It also may be used as a sealing gasket for covers flanges and windows in cryogenic applications Each sheet 1s 0 005 x 2 x 2 in Apiezon Grease 25 g Tube It is designed for general purposes where operating temperatures GAH 25 necessitate the use of a relatively high melting point grease Melting point is 523 250 C Can be removed using Xylene with an isopropyl alcohol rinse
33. When a command is issued the computer is acting as talker and the instrument as listener The format is lt command mnemonic gt lt space gt lt parameter data gt lt terminators gt Command mnemonics and parameter data necessary for each one is described in Section 6 3 Terminators must be sent with every message string A query string is issued by the computer and instructs the instrument which response to send Queries are issued similar to commands with the computer acting as talker and the instrument as listener The query format is Xquery mnemonic gt lt gt lt space gt lt parameter data gt lt terminators gt Query mnemonics are often the same as commands with the addition of a question mark Parameter data is often unnecessary when sending queries Query mnemonics and parameter data if necessary is described in Section 6 3 Terminators must be sent with every message string Issuing a query does not initiate a response from the instrument A response string is sent by the instrument only when it is addressed as a talker and the computer becomes the listener The instrument will respond only to the last query it receives The response can be a reading value status report or the present value of a parameter Response data formats are listed along with the associated queries in Section 6 3 6 1 4 Status System 6 1 4 1 Overview The Model 325 implements a status system compliant to the IEEE 488 2 1992 stan
34. Your use of the Product is entirely at your own risk Some countries states and provinces do not allow the exclusion of liability for incidental or consequential damages so the above limitation may not apply to you LIMITED WARRANTY STATEMENT Continued 9 EXCEPT TO THE EXTENT ALLOWED BY APPLICABLE LAW THE TERMS OF THIS LIMITED WARRANTY STATEMENT DO NOT EXCLUDE RESTRICT OR MODIFY AND ARE IN ADDITION TO THE MANDATORY STATUTORY RIGHTS APPLICABLE TO THE SALE OF THE PRODUCT TO YOU CERTIFICATION Lake Shore certifies that this product has been inspected and tested in accordance with its published specifications and that this product met its published specifications at the time of shipment The accuracy and calibration of this product at the time of shipment are traceable to the United States National Institute of Standards and Technology NIST formerly known as the National Bureau of Standards NBS FIRMWARE LIMITATIONS Lake Shore has worked to ensure that the Model 325 firmware is as free of errors as possible and that the results you obtain from the instrument are accurate and reliable However as with any computer based software the possibility of errors exists In any important research as when using any laboratory equipment results should be carefully examined and rechecked before final conclusions are drawn Neither Lake Shore nor anyone else involved in the creation or production of this firmware can pay for loss of ti
35. excessive temperature and spread of fire from the instrument Environmental conditions outside of the conditions below may pose a hazard to the operator and surrounding area Indoor use Altitude to 2000 m Temperature for safe operation 5 C to 40 C Maximum relative humidity 80 for temperature up to 31 C decreasing linearly to 50 at 40 C Power supply voltage fluctuations not to exceed 10 of the nominal voltage Overvoltage category II Pollution degree 2 1 8 Introduction Lake Shore Model 325 Temperature Controller User s Manual Safety Summary Continued Ground the Instrument To minimize shock hazard the instrument is equipped with a three conductor AC power cable Plug the power cable into an approved three contact electrical outlet or use a three contact adapter with the grounding wire green firmly connected to an electrical ground safety ground at the power outlet The power jack and mating plug of the power cable meet Underwriters Laboratories UL and International Electrotechnical Commission IEC safety standards Ventilation The instrument has ventilation holes in its side covers Do not block these holes when the instrument is operating Do Not Operate in an Explosive Atmosphere Do not operate the instrument in the presence of flammable gases or fumes Operation of any electrical instrument in such an environment constitutes a definite safety hazard Keep Away trom Live Cir
36. interfacing parts or other supplies not furnished by Lake Shore d unauthorized modification or misuse e operation outside of the published specifications or f improper site preparation or maintenance 6 TO THE EXTENT ALLOWED BY APPLICABLE LAW THE ABOVE WARRANTIES ARE EXCLUSIVE AND NO OTHER WARRANTY OR CONDITION WHETHER WRITTEN OR ORAL IS EXPRESSED OR IMPLIED LAKE SHORE SPECIFICALLY DISCLAIMS ANY IMPLIED WARRANTIES OR CONDITIONS OF MERCHANTABILITY SATISFACTORY QUALITY AND OR FITNESS FOR A PARTICULAR PURPOSE WITH RESPECT TO THE PRODUCT Some countries states or provinces do not allow limitations on an implied warranty so the above limitation or exclusion might not apply to you This warranty gives you specific legal rights and you might also have other rights that vary from country to country state to state or province to province 7 TO THE EXTENT ALLOWED BY APPLICABLE LAW THE REMEDIES IN THIS WARRANTY STATEMENT ARE YOUR SOLE AND EXCLUSIVE REMEDIES 8 EXCEPT TO THE EXTENT PROHIBITED BY APPLICABLE LAW IN NO EVENT WILL LAKE SHORE OR ANY OF ITS SUBSIDIARIES AFFILIATES OR SUPPLIERS BE LIABLE FOR DIRECT SPECIAL INCIDENTAL CONSEQUENTIAL OR OTHER DAMAGES INCLUDING LOST PROFIT LOST DATA OR DOWNTIME COSTS ARISING OUT OF THE USE INABILITY TO USE OR RESULT OF USE OF THE PRODUCT WHETHER BASED IN WARRANTY CONTRACT TORT OR OTHER LEGAL THEORY AND WHETHER OR NOT LAKE SHORE HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES
37. made of e g carbon glass germanium platinum or rhodium iron resolution The degree to which nearly equal values of a quantity can be discriminated display resolution The resolution of the physical display of an instrument This is not always the same as the measurement resolution of the instrument Decimal display resolution specified as 7 digits has 10 possible display values A resolution of 7 and one half digits has 2 x 10 possible values measurement resolution The ability of an instrument to resolve a measured quantity For digital instrumentation this is often defined by the analog to digital converter being used A n bit converter can resolve one part in 2 The smallest signal change that can be measured is the full scale input divided by 2 for any given range Resolution should not be confused with accuracy RhFe Rhodium iron Rhodium alloyed with less than one atomic percent iron is used to make the Lake Shore RF family of sensors Rhodium iron is a spin fluctuation alloy that has a significant temperature coefficient of resistance below 20 K where most metals rapidly lose sensitivity root mean square RMS The square root of the time average of the square of a quantity for a periodic quantity the average is taken over one complete cycle Also known as effective value room temperature compensation Thermocouples are a differential measurement device Their signal represents the difference in temperature between their ends
38. panel the user should immediately press the Heater Range key to verify that the proper loop is displayed and the heater shows Off 4 14 HEATER RESISTANCE SETTING The Model 325 Loop 1 and Loop 2 heater outputs are designed to accommodate two common heater resistance values 25 and 50 In order to achieve full output power and stable temperature control over the full output range 0 100 the heater resistance setting must be set properly for both control loops For Loop 1 the heater resistance setting controls the heater output compliance voltage 50 setting 36 V nominal 25 setting 25 V nominal Loop 1 was designed to provide 0 1 A of output current for heaters up to 20 lower than the nominal heater resistance when the proper heater resistance setting is used For Loop 2 the heater resistance setting controls the heater output full scale voltage 50 setting 10 V 25 setting 5 V If the heater resistance setting is not set properly limiting could occur which could result in temperature control instability An exception occurs when using a heater greater than the heater resistance setting on Loop 2 In this situation the maximum heater power is lowered as the heater resistance increases but control over the full output range will not be limited To set the heater resistance for the currently displayed loop press the Control Setup key then press the Enter key until you see the following display
39. 0 2 term Control Loop 1 zone 1 is valid to 25 0 K with P 10 I 7 20 D 0 and a heater range of 2 6 34 Remote Operation 20 Input Format Returned Format Lake Shore Model 325 Temperature Controller User s Manual Control Loop Zone Table Parameter Query ZONE lt loop gt lt zone gt term n nn lt loop gt lt zone gt Specifies which loop to query or 2 Specifies which zone in the table to query Valid entries 1 10 top value P value I value D value lt mout value range term nnnnnn nnnnnn nnnnnn nnnnnn nnnnnn n Refer to command for description Remote Operation 6 35 Lake Shore Model 325 Temperature Controller User s Manual This Page Intentionally Left Blank 6 36 Remote Operation Lake Shore Model 325 Temperature Controller User s Manual CHAPTER 7 OPTIONS AND ACCESSORIES 7 0 GENERAL This chapter provides information on the models options and accessories available for the Model 325 temperature controller 7 1 MODELS The list of Model 325 model numbers is provided as follows Model Description of Models Standard Temperature Controller Includes all features Model numbers as follows 395 325 Two diode resistor inputs 325 T1 One diode resistor one thermocouple input 325 T2 Two thermocouple inputs Power Configurations The instrument is co
40. 1 19645 12 410 0 0 24964 41 105 0 0 96524 70 019 5 1 22321 13 400 0 0 27456 42 100 0 0 97550 71 017 0 1 26685 14 395 0 0 28701 43 095 0 0 98564 72 015 0 1 30404 15 380 0 0 32417 44 090 0 0 99565 73 013 5 1 33438 16 365 0 0 36111 45 085 0 1 00552 74 012 5 1 35642 17 345 0 0 41005 46 080 0 1 01525 75 011 5 1 38012 18 330 0 0 44647 47 075 0 1 02482 76 010 5 1 40605 19 325 0 0 45860 48 070 0 1 03425 77 009 5 1 43474 20 305 0 0 50691 49 065 0 1 04353 78 008 5 1 46684 21 300 0 0 51892 50 058 0 1 05630 79 007 5 1 50258 22 285 0 0 55494 51 052 0 1 06702 80 005 2 1 59075 23 265 0 0 60275 52 046 0 1 07750 81 004 2 1 62622 24 250 0 0 63842 53 040 0 1 08781 82 003 4 1 65156 25 235 0 0 67389 54 039 0 1 08953 83 002 6 1 67398 26 220 0 0 70909 55 036 0 1 09489 84 002 1 1 68585 27 205 0 0 74400 56 034 0 1 09864 85 001 7 1 69367 28 190 0 0 77857 57 033 0 1 10060 86 001 4 1 69818 29 180 0 0 80139 58 032 0 1 10263 Curve Tables Lake Shore Model 325 Temperature Controller User s Manual Table D 2 Standard DT 670 Diode Curve wies v sessi 7 ew 0 090570 1 01064 1 19475 0 110239 1 02125 1 24208 0 136555 1 03167 1 26122 0 179181 1 04189 1 27811 0 265393 5 1 05192 1 29430 0 349522 1 06277 1 31070 0 452797 1 07472 1 32727 0 513393 1 09110 1 34506 0 563128 5 1 09602 1 36423 0 607845 1 10014 1 38361 0 648723 1 10393 1 40454 0 686936 1 10702 1
41. 1070 HT 15 K to 420 K2 gt 28 lt 19 Cernox CX 1080 HT 50 K to 420 K2 gt 28 lt 19 Negative Temperature Germanium GR 200A B 1000 2 2 K to 100 K3 Not Recommended Coefficient NTC RTDs Germanium GR 200A B 1500 2 6 K to 100 K Not Recommended Germanium GR 200A B 2500 3 1 K to 100 K 3 Not Recommended Carbon Glass CGR 1 500 4Kto 325 K T gt 2Kto lt 19T Carbon Glass CGR 1 1000 5 K to 325 K T gt 2Kto lt 19T Carbon Glass CGR 1 2000 6 K to 325 K4 T gt 2Kto lt 19T Rox RX 102A 1 4K to 40 K4 T gt 2Kto lt 10T Type K 9006 006 3 2 K to 1505 K Not Recommended Thermocouples Type E 9006 004 3 2 K to 934 K Not Recommended Chromel AuFe 0 07 9006 002 1 2 K to 610 K Not Recommended Single excitation current may limit the low temperature range of NTC resistors Non HT version maximum temperature 325 Low temperature limited by input resistance range Low temperature specified with self heating error lt 5 mK Low temperature specified with self heating error lt 12 mK Silicon diodes are the best choice for general cryogenic use from 1 4 K to above room temperature Diodes are economical to use because they follow a standard curve and are interchangeable in many applications They are not suitable for use in ionizing radiation or magnetic fields Cernox thin film RTDs offer high sensitivity and low magnetic field induced errors over the 2 K to 420 K temperature range Cernox sensors require calibration Platinum RT Ds offer high uniform
42. 152 29 7714 988 5 12 6 44774 10 35 59 5 78268 80 106 1 12444 244 153 30 5011 1006 13 6 44601 11 15 60 5 74084 82 5 107 0 91675 249 5 154 31 2074 1023 14 6 44403 12 61 5 69792 85 108 0 70686 255 155 31 8905 1039 5 15 6 44189 12 85 62 5 6539 87 5 109 0 47553 261 156 32 571 1056 16 6 43947 13 75 63 5 60879 90 110 0 22228 267 5 157 33 2489 1072 5 17 6 43672 14 7 64 5 5626 92 5 111 0 053112 274 5 158 33 9038 1088 5 18 6 43378 15 65 65 5 51535 95 112 0 350783 282 159 34 5561 1104 5 19 6 43065 16 6 66 5 46705 97 5 113 0 651006 289 5 160 35 2059 1120 5 20 6 42714 17 6 67 5 4177 100 114 0 973714 297 5 161 35 8532 1136 5 21 6 42321 18 65 68 5 36731 102 5 115 1 31919 306 162 36 4979 1152 5 22 6 41905 19 7 69 5 3159 105 116 1 70801 315 5 163 37 14 1168 5 23 6 41442 20 8 70 5 26348 107 5 117 2 14052 326 164 37 7596 1184 24 6 40952 21 9 71 5 19928 110 5 118 2 69954 339 5 165 38 3767 1199 5 25 6 40435 23 72 5 13359 113 5 119 3 75883 365 166 38 9915 1215 26 6 39841 24 2 73 5 06651 116 5 120 4 29687 378 167 39 6038 1230 5 27 6 39214 25 4 74 4 99801 119 5 121 4 74986 389 168 40 2136 1246 28 6 38554 26 6 75 4 92813 122 5 122 5 17977 399 5 169 40 821 1261 5 29 6 37863 27 8 76 4 85687 125 5 123 5 60705 410 170 41 4063 1276 5 30 6 37077 29 1 77 4 78426 128 5 124 6 03172 420 5 171 41 9893 1291 5 31 6 36253 30 4 78 4 71031 131 5 125 6 49428 432 172 42 5699 1306 5 32 6 35391 31 7 79 4 63503 134 5 126 7 09465 447 173 43 1288 1321 33
43. 2 1 TEMPERATURE SENSOR 2 1 2 1 1 Temperature led 2 1 2 1 2 Sensor Serisitivity 5 uer ote tp ia 2 1 2 1 3 Environmental Conditlons terni rettet ttt eene ccr int eaa come Een Er 2 1 2 1 4 Measurement Accuracy sssssssssssssssssssseeeeter enhn nenetrnt lien hh tente sisi sien nere 2 2 2 1 5 Sensor Package nece ete REP eec eer bt tert ie ERE Ern 2 2 2 2 CALIBRATED SENSORS Senteinde idoni dee Eee deae eene de dnte Ede 2 2 2 2 1 Traditional Calibration 2 2 2 2 2 SOU GA MH 2 2 2 2 3 Standard CUIVes tiic 420 2 3 2 2 4 Cal uve 1M 2 4 2 3 SENSOR INSTALLATION 5 e nieve eevee 2 4 2 3 1 Mounting Materials eee ee sone ipee d Te Ya eoa ce ee teeter ee el 2 4 2 3 2 Sensor LOCATON LL i 2 4 2 3 3 Ur role Ponti 2 4 2 3 4 Contact Area eo ere RUPEE ERR ERU EET ER CER Pa te mmo e 2 4 2 3 5 one t CERTE RECEPERUNT ER Gr tat tr bm 2 5 2 3 6 Lead
44. 4 701810 481 50 20 4 435090 54 80 54 1 114900 222 50 88 4 947390 492 00 21 4 370520 58 60 55 0 940599 230 50 89 5 636410 521 50 22 4 303610 62 50 56 0 754604 239 00 90 5 870300 531 50 23 4 234290 66 50 57 0 556906 248 00 91 6 547630 560 50 24 4 164270 70 50 58 0 358437 257 00 92 6 711600 567 50 25 4 093560 74 50 59 0 170179 265 50 93 6 781410 570 50 26 4 022170 78 50 60 0 041150 275 00 94 6 931500 577 00 27 3 950100 82 50 61 0 152699 280 00 95 7 001360 580 00 28 3 877360 86 50 62 0 163149 280 50 96 7 166710 587 00 29 3 803960 90 50 63 0 374937 290 00 97 7 260420 591 00 30 3 729910 94 50 64 0 542973 297 50 98 7 412010 597 50 31 3 655230 98 50 65 0 598604 300 00 99 7 529070 602 50 32 3 579930 102 50 66 0 774384 308 00 100 7 657460 608 00 33 3 504020 106 50 67 0 840638 311 00 101 7 704410 610 00 34 3 427530 110 50 68 1 126350 324 00 D 10 Curve Tables
45. 4n x 10 H m magnetic hysteresis The property of a magnetic material where the magnetic induction B for a given magnetic field strength H depends upon the past history of the samples magnetization magnetic induction B See magnetic flux density magnetic moment m This is the fundamental magnetic property measured with DC magnetic measurements systems such as a vibrating sample magnetometer extraction magnetometer SQUID magnetometer etc The exact technical definition relates to the torque exerted on a magnetized sample when placed in a magnetic field Note that the moment is a total attribute of a sample and alone does not necessarily supply sufficient information in understanding material properties A small highly magnetic sample can have exactly the same moment as a larger weakly magnetic sample see Magnetization Measured in SI units as A m and cgs units as emu 1 emu 10 A n magnetic units Units used in measuring magnetic quantities Includes ampere turn gauss gilbert line of force maxwell oersted and unit magnetic pole magnetization M This is a material specific property defined as the magnetic moment m per unit volume V M m V Measured SI units as A m and in cgs units as emu cm 1 emu cm 10 A m Since the mass of a sample is generally much easier to determine than the volume magnetization is often alternately expressed as a mass magnetization defined as the moment per unit mass material saf
46. 5 entere eite nitri neue ed erreur metuat dete EE 3 4 Thermocouple Input Definition and Common Connector Polarities see 3 6 1 325 Front Panel e 4 1 Display Deflpition 2 e eee Ie e Pe dero de E D us 4 3 Display Format Definition 4 4 Record OF Zone Settings imn e EAR Ue deus 4 20 SoftCal Temperature Ranges for Silicon Diode Sensors esee enm 5 7 SoftCal Temperature Ranges for Platinum 5 8 Model 325 Status System oii To cei esee deest oe dne 6 4 standard Event Status Register oreet e eese peine 6 6 Operation Event Register arien eter erf Oe beta fh ne quie sede te IR eU oe feu ee deoa 6 7 Status Byte Register and Service Request Enable 6 8 GPIB Settirig Configuraltlori trt t et ER dacs Ede E enisi 6 11 DEV 12 Device Template enne 6 11 Model 325 Sensor and Heater Cable Assembly sse eene eene nnne 7 4 Model 3003 Heater Output 7 4 Model RM 1 2 Rack Mount Kit eese ce
47. 7 1 7 1 MODELS 7 1 7 2 OPTIONS isos 7 1 7 3 ACCESSORIES genet ape ta eie ta ia idea bet 7 2 7 4 MODEL 3003 HEATER OUTPUT 7 4 CM Ucet 8 1 8 0 oie eee ehe tuoi meam ied 8 1 8 1 CONTACTING LAKE SHORE 5 8 1 8 2 RETURNING PRODUCTS TO LAKE 8 1 8 3 FUSE DRAWER foo ui deine Ee Te dela nahn oa a E et ee SER o hehe 8 2 8 4 LINE VOLTAGE SELECTION iere et e En n ee Ip DEBER e peto Ie DE Gene in ities 8 2 8 5 FUSE REPLEAGEMBENT ete dnce mem eS 8 3 8 6 ELECIROSTATIG DISGHARQGE 1 eere ree EFIE Ro rue Sie sitet Ri 8 3 8 6 1 Identification of Electrostatic Discharge Sensitive 8 3 8 6 2 Handling Electrostatic Discharge Sensitive 8 3 8 7 REAR PANEL CONNECTOR 8 4 8 7 1 Serial Iriterface Cable WANG 4 8 6 8 7 2 IEEE 488 Interface 8 7 8 8 TOP OF ENC
48. 8 NC A _ 8 DCD in 6 DSR in 4 DTR out 6 DSR Model 325 to PC Interface using Null Modem Adapter Model 325 DE 9P Null Modem Adapter PC DE 9P 5 GND gt 5 GND 2 RD in TTT 3 TD out 3 TD out fF 2 RD in 1 NC 5 4 DTR out 6 DSR in 1 DCD in 4 DTR out 6 DSR in 7 DTR tied to 4 8 CTS in 8 NC A _7 RTS out 9 ING NOTE Same as null modem cable design except PC CTS is provided from the Model 325 on DTR 8 6 Service Lake Shore Model 325 Temperature Controller User s Manual 8 7 2 IEEE 488 Interface Connector Connect to the IEEE 488 Interface connector on the Model 325 rear with cables specified in the IEEE 488 1978 standard document The cable has 24 conductors with an outer shield The connectors are 24 way Amphenol 57 Series or equivalent with piggyback receptacles to allow daisy chaining in multiple device systems The connectors are secured in the receptacles by two captive locking screws with metric threads The total length of cable allowed in a system is 2 m for each device on the bus or 20 m maximum The Model 325 can drive a bus of up to 10 devices A connector extender is required to use the IEEE 488 interface and relay
49. A summary of all the commands is provided in Table 6 9 All the commands are detailed in Section 6 3 1 which is presented alphabetical order Sample Command Format Command name Form of the command input _ Syntax of user parameter input See Key below Definition of first parameter Definition of second parameter Sample Query Format Query name Form of the query input Syntax of user parameter input See Key below Definition of returned parameter Syntax of returned parameter Brief description of command Input Curve Number Command INCRV input curve number gt term a nn input Specify input A or B curve number Specify input curve 0 1 20 std curves 21 36 user curves Commands may additionally include Remarks and Examples INCRV Input Format Returned Format Brief description of query Input Curve Number Query INCRV lt input gt term a input curve number term nn Specify input A or B The initial Format definition is omitted for queries that do not require parameter input Key Begins common interface command Required to identify queries aa String of alphanumeric characters mn String of number characters that may include a decimal point term Terminator characters lt gt Indicated a parameter field many command specific state Parameter field with only On Off or Enable Disable states value
50. Calibration Cables Diode resistor calibration cable 1 required if single or dual diode resistor unit Dual Banana Plugs 6 Pin DIN 240 Connector Plug e Thermocouple calibration cable 1 required if single or dual thermocouple unit To Voltage Standard T Dual Banana 4 Ring Terminals To DMM Service 8 11 Lake Shore Model 325 Temperature Controller User s Manual Equipment Required for Calibration Continued Resistor Standards Resistor standards with the following nominal values if standards are not available 0 25 W 25 ppm C metal film resistors can be used they should have connectors attached to mate with two dual banana plugs for 4 lead measurement 0Q short 10 Q 100 Q 5000 1 5 100 Miscellaneous Dummy loads for warm up each for diode resistor inputs 6 pin DIN 240 connectors plug with 100 resistors configured for 4 lead measurement calibration cable with 100 kQ standard can be used Short length of uninsulated wire 1 each for thermocouple inputs 8 12 2 Diode Resistor Sensor Input Calibration NOTE thermocouple input calibration procedure in provided in Section 8 12 3 Overview Each sensor input requires calibration Sensor inputs contain a current source that can supply 10 uA or 1 mA of current only the 10 pA current sources are calibrated They are calibrated by adjusting pots on the Model 325 main board The sensor inputs contain mul
51. Gain Command CALG V 1 1 2 Connect the 100 kQ resistor to the loop 2 heater output Connect the positive lead of the DMM to the Loop 2 heater output positive terminal the negative lead is connected to the Loop 2 output negative terminal 8 16 Service Lake Shore Model 325 Temperature Controller User s Manual Loop 2 Voltage Output Calibration Continued 3 Set Loop 2 output to open loop operation and set manual output of 0 Read the output voltage with the DMM to a tolerance of 0 0001 VDC and record as Zero Offset ZO 4 Set Loop 2 manual output to 100 Read the output voltage with the DMM to a tolerance of 40 0010 and record as Full Scale FS 5 Calculate the gain factor by dividing 10 by the full output span gain factor 10 FS ZO 6 Program the offset calibration by negating the Zero Offset value read in step 3 and providing it using the CALZ command EXAMPLE Zero Offset DMM Reading 0 0231 Calibration Command CALZ V 1 0 0231 7 Program the gain calibration factor using the CALG command EXAMPLE Zero Offset DMM Reading 0 0231 Full Scale DMM Reading 10 0432 Gain Factor Calculation 10 10 0432 0 0231 0 99341 Calibration Command CALG V 1 0 99341 9 Send the CALSAVE command to save the constants in the EEPROM 8 12 6 Calibration Specific Interface Commands CALG Gain Calibration Constant Command Input CALG lt input gt lt type
52. Input Format Example SETP Input Format Returned Format SRDG Input Format Returned Format Remarks Lake Shore Model 325 Temperature Controller User s Manual Generate SoftCal Curve Command SCAL lt std gt lt dest gt lt SN gt lt 1 value gt lt 01 value gt lt T2 value gt lt U2 value gt lt T3 value gt lt U3 value gt term n nn aaaaaaaaaa nnnnn tnnnnn nnnnn tnnnnn tnnnnn tnnnnn lt std gt Specifies the standard curve to generate a SoftCal from Valid entries 1 6 7 lt dest gt Specifies the user curve to store the SoftCal curve Valid entries 21 35 lt SN gt Specifies the curve serial number Limited to 10 characters lt value Specifies first temperature point UI value Specifies first sensor units point lt T2 value gt Specifies second temperature point lt U2 value gt Specifies second sensor units point lt T3 value gt Specifies third temperature point lt U3 value gt Specifies third sensor units point Generates a SoftCal curve Refer to Section 5 3 SCAL 1 21 1234567890 4 2 1 6260 77 32 1 0205 300 0 0 5189 term Generates a three point SoftCal curve from standard curve 1 and saves it in user curve 21 Control Setpoint Command SETP lt loop gt lt value gt term n nnnnnn loop value SETP 1 122 5 term Control Loop 1 setpoint is now 122 5 based on its units Specifies which loop
53. Intentionally Left Blank Introduction Lake Shore Model 325 Temperature Controller User s Manual CHAPTER 2 COOLING SYSTEM DESIGN 2 0 GENERAL Selecting the proper cryostat or cooling source is probably the most important decision in designing a temperature control system The cooling source defines minimum temperature cool down time and cooling power Information on choosing a cooling source is beyond the scope of this manual This chapter provides information on how to get the best temperature measurement and control from cooling sources with proper setup including sensor and heater installation 2 4 TEMPERATURE SENSOR SELECTION This section attempts to answer some of the basic questions concerning temperature sensor selection Additional useful information on temperature sensor selection is available in the Lake Shore Temperature Measurement and Control Catalog The catalog has a large reference section that includes sensor characteristics and sensor selection criteria 2 1 1 Temperature Range Several important sensor parameters must be considered when choosing a sensor The first is temperature range The experimental temperature range must be known when choosing a sensor Some sensors can be damaged by temperatures that are either too high or too low Manufacturer recommendations should always be followed Sensor sensitivity is also dependent on temperature and can limit the useful range of a sensor It is important not to sp
54. Lake Shore Model 325 Temperature Controller User s Manual Table 6 7 Serial Interface Program Control Properties Current Name Property New Value Labell Name IbIExitProgram Caption Type exit to end program Label2 Name IblCommand Caption Command Label3 Name IbIResponse Caption Response Textl Name txtCommand Text lt blank gt Text2 Name txtResponse Text lt blank gt Command1 Name cmdSend Caption Send Default True Forml Name frmSerial Caption Serial Interface Program Timerl Enabled False Interval 10 12 Add code provided in Table 6 8 a Inthe Code Editor window under the Object dropdown list select General Add the statement Public gSend as Boolean b Double click on cmdSend Add code segment under Private Sub cmdSend_Click as shown in Table 6 8 c Inthe Code Editor window under the Object dropdown list select Form Make sure the Procedure dropdown list is set at Load The Code window should have written the segment of code Private Sub Form Load Add the code to this subroutine as shown in Table 6 8 d Double click on the Timer control Add code segment under Private Sub Timerl Timer as shown in Table 6 8 e Make adjustments to code if different com port settings are being used 13 Save the program 14 Run the program Serial Interface Program Iof x the window to the Type exit to end program right 15 Type in a command Command or query in t
55. OVLD1 Sensor A Overload NRDG New Sensor Reading OVLD2 Sensor B Overload Figure_6 1 bmp Figure 6 1 Model 325 Status System 6 4 Remote Operation Lake Shore Model 325 Temperature Controller User s Manual 6 1 4 1 4 Status Byte Register The Status Byte register typically referred to as the Status Byte is a non latching read only register that contains all of the summary bits from the register sets The status of the summary bits are controlled from the register sets as explained above The Status Byte also contains the Request for Service RQS Master Summary Status MSS bit This bit is used to control the Service Request hardware line on the bus and to report if any of the summary bits are set via the STB command The status of the RQS MSS bit is controlled by the summary bits and the Service Request Enable Register 6 1 4 1 5 Service Request Enable Register The Service Request Enable Register determines which summary bits in the Status Byte will set the RQS MSS bit of the Status Byte The user may write to or read from the Service Request Enable Register Each Status Byte summary bit is logically ANDed to the corresponding enable bit of the Service Request Enable Register When a Service Request Enable Register bit is set by the user and the corresponding summary bit is set in the Status Byte the RQS MSS bit of the Status Byte will be set which in turn sets the Service Request hardware line on the bus 6 1 4 1 6 R
56. PT 1000 30 800 Table D 4 08 RX 102A AA NTC RTD Rox RX 102A 0 05 40K Table D 5 09 RX 202A AA NTC RTD Rox RX 202A 0 05 40 Table D 6 10 Reserved 11 Reserved 12 Type K Thermo 25mV and 50mV Type K 3 1645K Table D 7 13 Type E Thermo 25mV and 50mV Type E 3 1274 Table D 8 14 Type T Thermo 25mV and 50mV Type T 3 670K Table D 9 15 AuFe 0 03 Thermo 25mV and 50mV AuFe 0 03 3 5 500 Table D 10 16 AuFe 0 07 Thermo 25mV and 50mV AuFe 0 0796 3 15 610K Table D 11 17 Reserved 18 Reserved 19 Reserved 20 Reserved 21 35 User Curves No longer sold by Lake Shore 4 5 1 Diode Sensor Curve Selection Once the input is setup for the Silicon or Gallium Aluminum Arsenide diode Section 4 4 1 you may choose a temperature curve standard curve numbers through 4 being relevant choices You are also given the choice of None You may also choose from any appropriate User Curves stored in Curve Numbers 21 through 36 Data points for standard diode curves are detailed in Tables D 1 through D 3 in Appendix D Press the Input Setup key Press the Enter key until you see the curve selection screen shown below Use the A or V key to cycle through the sensor curves until the desired curve is displayed Press the Enter key then the Escape key to return to the normal display Operation 4 11 Lake Shore Model 325 Temperature Controller User s Manu
57. Setting selections always include the Select for AW display a sample of which is shown below Data Entry Allows the user to enter number data using the data entry keys Data entry keys include the numbers 0 9 and decimal point Proportional control parameter is an example of a parameter that requires data entry During a data entry sequence use the data entry keys to enter the number value press the Enter key to accept the new data and advance to the next setting Press the Escape key once to clear the entry twice to return to the normal display Most data entry operations are combined with other settings and grouped under a function key Temperature or sensor unit parameters have the same setting resolution as the display resolution for their corresponding readings Data entry always includes the Enter for display a sample of which is shown below 4 1 4 Display Definition In normal operation the 2 row by 20 character LCD display is divided into four user configurable areas that can provide temperature readings setpoint display and heater status Other information is displayed when using the various functions on the keypad See Figure 4 2 Display Location 1 Display Location 2 Input A Source Input A Source Input B K Kelvin Input B Same choices as None No Display C Celsius None No Display Display Location 1 Sensor V mV or Q Input Reading Source Displ
58. Shore P N 106 233 NOTE Pin3 should not be used for new installations However to match existing Model 321 Model 330 or Model 340 connector wiring the definition of Pin 3 may be changed with a jumper See Figure 8 8 for jumper location To provide compatibility with sensor input connectors that have been wired for Lake Shore Models 321 330 or 340 Temperature Controllers Jumper 4 for Input A and Jumper 7 for Input B are used to select the function of Pin 3 of the connectors The Model 321 and the Model 330 each provide a constant 1 mA sensor excitation current on Pin 3 and 10 pA current on Pin 5 The Model 340 provides both 1 mA and 10 pA excitation current on Pin 5 and connects Pin 3 to sensor ground reference If the sensor being used was wired for use with a Model 321 or a Model 330 the jumper should be placed in the 321 330 position factory default This provides the output current selected via the front panel input setup function on both Pins 5 and 3 If the sensor was wired for use with a Model 340 the jumper should be placed in the 340 position This provides the output current on Pin 5 only and connect Pin 3 to sensor ground reference R V V A Pin Symbol Description Current 2 V Voltage 3 A 1 mA Model 321 330 Configuration Shield Model 340 Configuration 4 V Voltage 5 I Current 6 None Shield Figure 3 3 Diode Resistor Input Connector 3 4 2 Se
59. V Platinum 100 PT 100 Q Q K 800 Positive 0 001 Q Platinum 1000 PT 100 Q Q K 800 Positive 0 01 Q Rhodium Iron RF 100 Q 325 Positive 0 001 Q Carbon Glass CGR 1 1000 Q logQ K 325 Negative 0 00001 logQ Cernox CX 1030 Q logQ K 325 Negative 0 00001 logQ Germanium GR 200A 100 Q logQ K 325 Negative 0 00001 logQ Rox RX 102A Q logQ K 40 Negative 0 00001 logQ Type K 9006 005 mV mV K 1500 Positive 0 0001 mV Type E 9006 003 mV mV K 930 Positive 0 0001 mV Type T 9006 007 mV mV K 673 Positive 0 0001 mV Au Fe 0 0396 No Longer Sold mV mV K 500 Positive 0 0001 mV Au Fe 0 0796 9006 001 mV mV K 610 Positive 0 0001 mV 5 2 Advanced Operation Lake Shore Model 325 Temperature Controller User s Manual Curve Breakpoints Continued Setting resolution is also six digits in sensor units The curve format parameter defines the range and resolution in sensor units as shown in Table 5 2 The sensor type determines the practical setting resolution Table 5 2 lists recommended sensor units resolutions For most sensors additional resolution is ignored The breakpoints should be entered with the sensor units value increasing as point number increases There should not be any breakpoint locations left blank in the middle of a curve The search routine in the Model 325 interprets a blank breakpoint as the end of the curve 5 2 FRONT PANEL CURVE ENTRY OPERATIONS There are three operations associated wit
60. a multiplier Integral reset acts on the area of error with respect to time and can eliminate control offset or droop Derivative rate acts on the rate of change in error to dampen the system reducing overshoot quench A condition where the superconducting magnet goes normal i e becomes non superconductive When this happens the magnet becomes resistive heat is generated liquid cryogen is boiled off and the magnet power supply is shut down due to the sudden increase in current demand relief valve A type of pressure relief device which is designed to relieve excessive pressure and to re close and reseal to prevent further flow of gas from the cylinder after reseating pressure has been achieved remanence The remaining magnetic induction in a magnetic material when the material is first saturated and then the applied field is reduced to zero The remanence would be the upper limit to values for the remanent induction Note that no strict convention exists for the use of remanent induction and remanence and in some contexts the two terms may be used interchangeably remanent induction The remaining magnetic induction in a magnetic material after an applied field is reduced to zero Also see remanence repeatability The closeness of agreement among repeated measurements of the same variable under the same conditions resistance temperature detector RTD Resistive sensors whose electrical resistance is a known function of the temperature
61. a nonvolatile memory Options and Accessories 7 1 Lake Shore Model 325 Temperature Controller User s Manual 7 3 ACCESSORIES Accessories are devices that perform a secondary duty as an aid or refinement to the primary unit Refer to the Lake Shore Temperature Measurement and Control Catalog for details A list of accessories available for the Model 325 is as follows Mode Description of Accessories 106 009 Heater Output Connector Dual banana jack for heater output G 106 233 Sensor Input Mating Connector 6 pin DIN plug for diode resistor input 2 included 106 735 Terminal Block Mating Connector 2 pin terminal block for Loop 2 Model 325 Sensor Heater Cable Assembly 10 Feet Cable assembly for 2 diode resistor sensors and Loop 1 heater Approximately 3 m 10 ft long See Figure 7 1 G 112 326 Model 325 Sensor Heater Cable Assembly 20 Feet Cable assembly for 2 diode resistor sensors G 112 325 and Loop 1 heater Approximately 6 m 20 ft long See Figure 7 1 115 006 Detachable 120 VAC Line Cord 3003 Heater Output Conditioner The heater output conditioner is a passive filter that further reduces the already low heater output noise of the Model 325 Refer to Section 7 4 and see Figure 7 2 6201 IEEE 488 Cable 1 m 3 ft long IEEE 488 GPIB computer interface cable assembly CAL 325 a CERT Instrument recalibration with certificate 1 Instrument recalibration with certificate and data
62. a variety of temperature sensors sold by Lake Shore and other manufacturers An appropriate sensor type must be selected for each of the two inputs If the exact sensor model is not shown use the sensor input performance chart in Table 4 1 to choose an input type with similar range and excitation For additional details on sensors refer to the Lake Shore Temperature Measurement and Control Catalog or visit our website at www lakeshore com Table 4 1 Sensor Input Types Display Message a de Excitation Sensor Type S ms Coefficient Lake Shore Sensors Silicon Diode 25V 10 uA Silicon Diode Negative DT 4XX DT 500 07 670 Series GaAlAs Diode 75V 10pA ee ore Negative TG 120 Series 2500 ima DS GK Postive E TOO Senes RF 800 Rhodium Iron 1000 Plat 500 5000 1 mA 100 Q Platinum RTD gt 675 K 10000 Plat 5000 Q 1mA 1000 Q Platinum RTD QIK Positive Negative Temperature log vetro Parvon lass 1 i TM NTC RTD 7500 Q 10 uA Coefficient NTC RTD RIK Negative Germanidm Rox and Thermox Thermo 25mV 25 mV NA Thermocouple Chromel AuFe 0 07 Positive Type E Chromel Constantan Thermo 50mV 50 mV NA Thermocouple Type K Chromel Alumel Type T Copper Constantan Refer to the Lake Shore Temperature Measurement and Control Catalog for details on Lake Shore temperature sensors 4 41 Diode Sensor Input Setup 10 pA Excitation Current Di
63. accommodate a variety of sensors and units With setpoint expressed in sensor units setpoint range is unlimited The user must determine suitability of a setpoint value In temperature units a safety feature limits the setpoint value to help prevent load damage The setpoint limit in the temperature response curve sets maximum safe temperature in kelvin for the sensor package It can be verified by using the Curve Entry key The setpoint is limited to a value less than or equal to the limit If the setpoint value changes from the number entered when Enter is pressed it is likely the setpoint exceeds the above limit or is inappropriate for the sensor type Once control setup parameters are configured Section 4 7 and the active control loop is selected Section 4 6 1 the desired temperature setpoint is entered by pressing the Setpoint key The setpoint is entered using the numeric keypad which includes the numbers 0 9 and decimal point Press the Enter key to accept the new setpoint or press the Escape key to cancel If the display format is configured to show the setpoint Section 4 3 you will see something resembling the following for a normal display 4 22 Operation Lake Shore Model 325 Temperature Controller User s Manual 4 12 RAMP The Model 325 generates a smooth setpoint ramp when the setpoint units are expressed in temperature The user can set ramp rate in degrees per minute with a
64. and M 0 interchangeability Ability to exchange one sensor or device with another of the same type without a significant change in output or response international system of units SI A universal coherent system of units in which the following seven units are considered basic meter kilogram second ampere kelvin mole and candela The International System of Units or Syst me International d Unit s 51 was promulgated in 1960 by the Eleventh General Conference on Weights and Measures For definition spelling and protocols ee Reference 3 for a short convenient guide interpolation table A table listing the output and sensitivity of a sensor at regular or defined points which may be different from the points at which calibration data was taken intrinsic coercivity The magnetic field strength H required to reduce the magnetization M or intrinsic induction in a magnetic material to zero intrinsic induction The contribution of the magnetic material B to the total magnetic induction B SD cgs 5 68 International Practical Temperature Scale of 1968 Also abbreviated as 7s isolated neutral system A system that has no intentional connection to ground except through indicating measuring or protective devices of very high impedance TS 90 International Temperature Scale of 1990 Also abbreviated as 799 This scale was designed to bring into as close a coincidence with thermodynamic t
65. and the TM or symbol Alumel and Chromel are trademarks of Concept Alloys LLC Apiezon is a trademark of M amp I Materials Ltd CalCurve Cernox Duo Twist Quad Lead Quad Twist Rox and SoftCal are trademarks of Lake Shore Cryotronics Inc Cryogloves is a trademark of Tempshield LabVIEW and NI 488 2 are trademarks of National Instruments MS DOS and Windows are trademarks of Microsoft Corp PC XT AT and PS 2 are trademarks of IBM Stycast is a trademark of Emerson amp Cummings Copyright 2006 2011 by Lake Shore Cryotronics Inc All rights reserved No portion of this manual may be reproduced stored in a retrieval system or transmitted in any form or by any means electronic mechanical photocopying recording or otherwise without the express written permission of Lake Shore Lake Shore Model 325 Temperature Controller User s Manual DECLARATION OF CONFORMITY We Lake Shore Cryotronics Inc 575 McCorkle Blvd Westerville OH 43082 8888 USA hereby declare that the equipment specified conforms to the following Directives and Standards Application of Council Directives sss 73 23 EEC 89 336 E EC Standards to which Conformity is declared EN61010 1 2001 Overvoltage 11 Pollution Degree 2 EN61326 A2 2001 Class A Annex B Model Number 325 j Ed Maloof Prin
66. annunciator blinks to indicate the instrument is gathering data This process takes from 1 to 17 minutes depending on the system reaction time The control channel annunciator stops blinking when calculations are complete and new parameter values have been stored The annunciator will also stop blinking if the algorithm is unable to complete Possible reasons include setpoint change too small manual control parameter changed during tuning heater not turned on or control sensor curve not selected If the controller is not tuned satisfactorily on the first attempt make several small 2 degree setpoint changes to see if better parameter values are calculated To select an AutoTune mode press the AutoT une key and press the A V or AutoTune key to cycle the display to AutoTune PID You will see the following display Use the A or V key to cycle between Auto PID Auto PI and Auto P Press the Enter key The controller is now in AutoTuning mode 4 10 ZONE SETTINGS Closed Loop Control Mode The Model 325 allows the user to establish up to 10 custom contiguous temperature zones where the controller will automatically use pre programmed PID values and heater ranges Zone control can be active for both control loops at the same time The user should configure the zones using 01 as the lowest to 10 as the highest zone Zone boundaries are always specified in kelvin K The bottom of the first zone is always 0 K therefore only the upp
67. appears correct but is not the E most accurate Cathode 7 Anode 3 4 5 Four Lead Sensor Measurement All sensors including both two lead and four lead can be measured with a four lead technique The purpose of a four lead measurement is to eliminate the effect of lead resistance on the measurement If it is not taken out lead resistance is a direct error when measuring a sensor In a four lead measurement current leads and voltage leads are run separately up to the sensor With separate leads there is little current i Four Lead in the voltage leads so their resistance does not enter into the Diode measurement Resistance in the current leads will not change the y measurement as long as the voltage compliance of the current source is not reached When two lead sensors are used in four lead measurements the short leads on the sensor have an insignificant resistance Four Lead Platinum 3 4 6 Two Lead Sensor Measurement There are times when crowding in a cryogenic system forces users to read sensors in a two lead configuration because there are not enough feedthroughs or room for lead wires If this is the case plus voltage to plus current and minus voltage to minus current leads are attached at the back of the instrument or at the vacuum feedthrough The error in a resistive measurement is the resistance of the lead wire run with current and voltage together If the leads contribute 2 or 3 Q to a 10
68. body is a solid liquid or gas Thermometers are used to measure temperature The temperature scale is based on the temperature at which ice liquid water and water vapor are all in equilibrium This temperature is called the triple point of water and is assigned the value 0 C 32 F and 273 15 K These three temperature scales are defined as follows Celsius Abbreviation C A temperature scale that registers the freezing point of water as 0 C and the boiling point as 100 C under normal atmospheric pressure Formerly known as Centigrade Originally devised by Anders Celsius 1701 1744 a Swedish astronomer Fahrenheit Abbreviation F A temperature scale that registers the freezing point of water as 32 F and the boiling point as 212 F under normal atmospheric pressure Originally devised by Gabriel Fahrenheit 1686 1736 a German physicist residing in Holland developed use of mercury in thermometry Kelvin Abbreviation K An absolute scale of temperature the zero point of which is approximately 273 15 C Scale units are equal in magnitude to Celsius degrees Originally devised by Lord Kelvin William Thompson 1824 1907 a British physicist mathematician and inventor B2 0 COMPARISON The three temperature scales are graphically compared in Figure B 1 Boiling point of water 373 15 100 C 212 F Freezing point of water 273 15 0 C 32 F Absolute zero OK 273 15 C 459 67 F kelvin Celsius Fahr
69. brackets 3 Use 5 64 hex key to remove four screws attaching top panel to unit 4 Use 5 64 hex key to loosen two rear screws attaching bottom panel to unit 5 Carefully remove the back bezel by sliding it straight back away from the unit 6 Slide the top panel back and remove it from the unit INSTALLATION Slide the top panel forward in the track provided on each side of the unit Carefully replace the back bezel by sliding it straight into the unit Use 5 64 hex key to install four screws attaching top panel to unit Use 5 64 hex key to tighten two rear screws attaching bottom panel to unit If required reattach 19 inch rack mounting brackets Av duo ns Connect power cord to rear of unit and set power switch to On 1 8 9 FIRMWARE REPLACEMENT There are two integrated circuits ICs that may potentially require replacement The location of the ICs is shown in Figure 8 8 Input Microcontroller U1 1 Contains software that configures the inputs takes readings and performs control functions Has a sticker on top labeled M325IF HEX and a version number e Main Firmware Erasable Programmable Read Only Memory EPROM 048 Contains the user interface software Has a sticker on top labeled M325F HEX and date Use the following procedure to replace either of these ICs 1 Follow the top of enclosure REMOVAL procedure in Section 8 8 2 Locate the IC on the main circuit board See Figure 8 8 Note orientation
70. but are sent in response to a query A leading is not required but a leading required 6 1 6 Troubleshooting New Installation 1 Check instrument address 2 Always send terminators 3 Send entire message string at one time including terminators 4 Send only one simple command at a time until communication is established 5 Besure to spell commands correctly and use proper syntax 6 Attempt both Talk and Listen functions If one works but not the other the hardware connection is working so look at syntax terminators and command format 7 one message is received after resetting the interface check the repeat addressing setting It should be enabled Old Installation No Longer Working 1 Power instrument off then on again to see if it is a soft failure 2 Power computer off then on again to see if the IEEE card is locked up 3 Verify that the address has not been changed on the instrument during a memory reset 4 Check all cable connections Intermittent Lockups 1 Check cable connections and length 2 Increase delay between all commands to 50 ms to make sure instrument is not being overloaded 6 14 Remote Operation Lake Shore Model 325 Temperature Controller User s Manual 6 2 SERIAL INTERFACE OVERVIEW The serial interface used in the Model 325 is commonly referred to as an RS 232C interface RS 232C is a standard of the Electronics Industries Association EIA tha
71. display Use the A or V key to cycle through the following data sources Temp Temp Sensor For this example select Temp K then press the Enter key NOTE The sensor reading of the instrument can always be displayed in sensor units If a temperature response curve is selected for an input its readings may also be displayed in temperature With the settings from the previous example Display Location 1 will resemble the following The process is the same for the other three display locations However additional choices are provided for Display Location 3 and 4 being Setpoint and Heater Out respectively In the following example we will setup Display Location 3 to show the setpoint Press the Display Format key Use the A or V key to increment or decrement through Display Locations 1 through 4 For this example select Display Location 3 then press the Enter key You will see the following display Use the A or V key to cycle between Input A Input B Setpoint or None For this example select Setpoint then press the Enter key With the settings from the previous example and assuming you setup Display Location 1 detailed above the display will resemble the following To change the setpoint units refer to Control Setup Section 4 7 Operation 4 5 Lake Shore Model 325 Temperature Controller User s Manual 44 INPUT SETUP The Model 325 supports
72. drawer holding the line voltage selector and fuse Uu paroi Remove existing fuse s Replace with proper Slow Blow time delay fuse ratings as follows 100 120 V 1 6AT250 V 5x20 mm 220 240 V 1 6AT250 V 5x20 mm Re assemble line input assembly in reverse order Verify voltage indicator in the line input assembly window Connect instrument power cord c Turn power switch On I 8 6 ELECTROSTATIC DISCHARGE Electrostatic Discharge ESD may damage electronic parts assemblies and equipment ESD is a transfer of electrostatic charge between bodies at different electrostatic potentials caused by direct contact or induced by an electrostatic field The low energy source that most commonly destroys Electrostatic Discharge Sensitive ESDS devices is the human body which generates and retains static electricity Simply walking across a carpet in low humidity may generate up to 35 000 V of static electricity Current technology trends toward greater complexity increased packaging density and thinner dielectrics between active elements which results in electronic devices with even more ESD sensitivity Some electronic parts are more ESDS than others ESD levels of only a few hundred volts may damage electronic components such as semiconductors thick and thin film resistors and piezoelectric crystals during testing handling repair or assembly Discharge voltages below 4000 V cannot be seen felt or he
73. feedback control system where there is an unbroken path of analog processing between the feedback device sensor and control actuator heater analog output A voltage output from an instrument that is proportional to its input For example from a digital voltmeter the output voltage is generated by a digital to analog converter so it has a discrete number of voltage levels anode The terminal that is positive with respect to the other terminal when the diode is biased in the forward direction Anode gt Cathode asphyxiant gas A gas which has little or no positive toxic effect but which can bring about unconsciousness and death by displacing air and thus depriving an organism of oxygen AutoTuning In Lake Shore temperature controllers the AutoTuning algorithm automatically determines the proper settings for Gain Proportional Reset Integral and Rate Derivative by observing the time response of the system upon changes in setpoint B Symbol for magnetic flux density See Magnetic Flux Density bar Unit of pressure equal to 10 pascal or 0 98697 standard atmosphere baud A unit of signaling speed equal to the number of discrete conditions or signal events per second or the reciprocal of the time of the shortest signal element in a character bel B A dimensionless unit expressing the ration of two powers or intensities or the ratio of a power to a reference power such that the number of bels is the commo
74. gain limit is entered using the numeric keypad which includes the numbers 0 9 and decimal point Proportional has a range of 0 to 1000 with a default of 50 Press the Enter key to save changes and return to the normal display 4 16 Operation Lake Shore Model 325 Temperature Controller User s Manual 4 8 2 Manually Setting Integral The integral parameter also called reset 1s the I part of the PID control equation It has a range of 0 to 1000 with a resolution of 0 1 Setting I to zero turns the reset function off The I setting is related to seconds by For example a reset number setting of 20 corresponds to a time constant of 50 seconds A system will normally take several time constants to settle into the setpoint The 50 second time constant if correct for the system being controlled would result in a system that stabilizes at a new setpoint in between 5 and 10 minutes To set Integral press the key You will see the following display The Integral reset is entered using the numeric keypad which includes the numbers 0 9 and decimal point Integral has a range of 0 to 1000 with a default of 20 Press the Enter key to save changes and return to the normal display 4 8 3 Manually Setting Derivative D The derivative parameter sometimes called rate is the D part of the PID control equation The rate time constant should normally be somewhere between 1 4 and 1 8 the integral time in se
75. gt lt value gt term Format a nn Ennnnnnn input Specifies which input or Loop 2 output the gain calibration constant will be provided to Valid entries are A or B for inputs and V for the Loop 2 output type Specifies the input sensor type Valid entries are 0 Silicon Diode or Loop 1 Heater not used 6 Thermo 25mV 1 GaAlAs Diode or Loop 2 Heater 7 Thermo 50mV 2 1000 Plat 250 Reversal Off 10 100Q Plat 250 Reversal On 3 100Q Plat 500 Reversal Off 11 1000 Plat 500 Reversal On 4 1000Q Plat Reversal Off 12 1000Q Plat Reversal On 5 NTC RTD Reversal Off 13 NTC RTD Reversal On lt value gt Gain calibration constant value Remarks Provides the gain calibration constant for the selected input or Loop 2 output CALG Gain Calibration Constant Query Input CALG lt input gt lt type gt term Format a nn lt input gt A B or V lt type gt 0 7 or 10 13 Returned lt value gt term Format nnnnnnn Refer to command for description Service 8 17 Lake Shore Model 325 Temperature Controller User s Manual CALREAD Six Digit Input Reading Query Input CALREAD lt input gt term Format a lt input gt AorB Returned lt value gt term Format xn nnnnn Remarks Returns 6 digit value of selected input reading Used for CALZ and CALG functions CALSAVE Calibration Save Command Input CALSAVE term Remarks Saves all CALZ and CALG calibr
76. heating of the area Similar to sensor lead wire the entire length of the heater wire should be in good thermal contact with the load to allow for thermal transfer Heat sinking also protects the wire from over heating and burning out Resistive heater wire is also wound into cartridge heaters Cartridge heaters are more convenient but are bulky and more difficult to place on small loads A typical cartridge is 0 25 inch in diameter and 1 inch long The cartridge should be snugly held in a hole in the load or clamped to a flat surface Heat sinking for good thermal contact is again important Foil heaters are thin layers of resistive material adhered to or screened on to electrically insulating sheets There are a variety of shapes and sizes The proper size heater can evenly heat a flat surface or around a round load The entire active area should be in good thermal contact with the load not only for maximum heating effect but to keep spots in the heater from over heating and burning out 2 4 4 Heater Wiring When wiring inside a vacuum shroud we recommend using 30 AWG copper wire for heater leads Too much heat can leak in when larger wire is used Heat sinking similar to that used for the sensor leads should be included so that any heat leaking in does not warm the load when the heater is not running The lead wires should be twisted to minimize noise coupling between the heater and other leads in the system When wiring outside the vacuum shr
77. in 3 RD in 2 RD in 3 Transmit Data TD out 4 RTS out 3 TD out 4 Data Terminal Ready out 5 CTS in 4 DTR out 5 Ground GND 6 DSR in 5 GND 6 Data Set Ready DSR in 7 GND 6 DSR in 7 Data Terminal Ready out tied to 4 8 DCD in 7 RTS out 8 No Connection 20 DTR out 8 CTS in 9 No Connection 22 Ring in in 9 Ring in in Figure 8 6 RS 232 Connector Details Service 8 5 Lake Shore Model 325 Temperature Controller User s Manual 8 7 1 Serial Interface Cable Wiring The following are suggested cable wiring diagrams for connecting the Model 325 serial interface to various customer personal computers PCs Model 325 to PC Serial Interface PC with DE 9P Model 325 DE 9P Standard Null Modem Cable DE 9S to DE 9S PC DE 9P 5 GND lt gt 5 GND 2 RD in 4 25 3 3 TD out MM 2 2RD in 4 DTR out DSR in 6 DSR in 4 DTR out 1 ee 7 RTS out 7 tied to 4 8 CTS in 8 NC DCD in Model 325 to PC Serial Interface PC with DB 25P Model 325 DE 9P Standard Null Modem Cable DE 98 to DB 25S PC DB 25P 5 GND 7 2 RD in _ 2 3 TD out 3 RD in 1 NC a 4 RTS out 7 DTR tied to 4 5 CTS in
78. is no buffer to adsorb small changes in the system Without buffering small disturbances can very quickly create large temperature changes In some systems it is necessary to add a small amount of thermal mass such as a copper block in order to improve control stability 2 5 5 System Nonlinearity Because of nonlinearities in the control system a system controlling well at one temperature may not control well at another temperature While nonlinearities exist in all temperature control systems they are most evident at cryogenic temperatures When the operating temperature changes the behavior of the control loop the controller must be retuned As an example a thermal mass acts differently at different temperatures The specific heat of the load material is a major factor in thermal mass and the specific heat of materials like copper change as much as three orders of magnitude when cooled from 100 K to 10 K Changes in cooling power and sensor sensitivity are also sources of nonlinearity The cooling power of most cooling sources also changes with load temperature This is very important when operating at temperatures near the highest or lowest temperature that a system can reach Nonlinearities within a few degrees of these high and low temperatures make it very difficult to configure them for stable control If difficulty is encountered it is recommended to gain experience with the system at temperatures several degrees away from the limit and gradua
79. message displays there may be a problem with the line power or the instrument Individual messages in a reading location normally indicate that input setup is required 4 3 DISPLAY FORMAT AND SOURCE UNITS SELECTION In the normal display the display is divided into four user configurable areas that can provide temperature readings setpoint display and heater status Figure 4 3 illustrates the display location numbering and available selections for each location To change Setpoint units and select Heater Out Power or Current refer to the description of Control Setup in Section 4 7 Display Location 1 Display Location 2 Input A Input A Input B Input B None None Display Location 3 Display Location 4 Input A Input A Input B Input B Setpoint Heater Out None None C 325 4 3 bmp Figure 4 3 Display Format Definition To configure a display location press the Display Format key to display the following screen Use the A or V key to increment or decrement through Display Locations 1 through 4 For this example select Display Location 1 then press the Enter key You will see the following display 4 4 Operation Lake Shore Model 325 Temperature Controller User s Manual Display Format And Source Units Selection Continued Use the A or V key to cycle between Input A Input B or None For this example select Input A then press the Enter key You will see the following
80. next display The Proportional P value is entered using the numeric keypad which includes the numbers 0 9 and decimal point Proportional has a range of 0 to 1000 with a default of 50 Press the Enter key to accept the new setting You will see the next display The Integral I value is entered using the numeric keypad which includes the numbers 0 9 and decimal point Integral has a range of 0 to 1000 with a default of 20 Press the Enter key to accept the new setting You will see the next display The Derivative D value is entered using the numeric keypad which includes the numbers 0 9 and decimal point Derivative has a range of 0 to 200 percent with a default of 0 Press the Enter key to accept the new setting You will see the next display The MHP Output setting is entered using the numeric keypad which includes the numbers 0 9 and decimal point Manual heater has a range of 0 to 100 percent with a default of 0 Press the Enter key to accept the new heater setting Assuming the zone is controlling using Loop 1 you will see the next display Use the A or V key to select the Heater Range High Low or Off Press the Enter key to accept the new heater range and return to the normal display If you are controlling using Loop 2 the last heater range setting 1s omitted This completes the setting of Zone 01 Repeat the process for the
81. of 25 W A smaller resistance of 40 at the 50 setting allows about 20 W of power while a larger resistance of 60 is limited by compliance voltage to about 21 W The Model 325 is designed to limit the internal power dissipation as a measure of self protection This internal power limit will not allow the output current to rise once the power limit is reached The resistor chosen as a heater must be able to withstand the power being dissipated in it Pre packaged resistors have a power specification that is usually given for the resistor in free air This power may need to be derated if used in a vacuum where convection cooling cannot take place and it is not adequately heat sinked to a cooled surface 2 6 Cooling System Design Lake Shore Model 325 Temperature Controller User s Manual 2 4 2 Heater Location For best temperature measurement accuracy the heater should be located so that heat flow between the cooling power and heater is minimized For best control the heater should be in close thermal contact with the cooling power Geometry of the load can make one or both of these difficult to achieve That is why there are several heater shapes and sizes 2 4 3 Heater Types Resistive wire like nichrome is the most flexible type of heater available The wire can be purchased with electrical insulation and has a predictable resistance per given length This type of heater wire can be wrapped around a cooling load to give balanced even
82. of existing IC CAUTION The ICs are Electrostatic Discharge Sensitive ESDS devices Wear shock proof wrist straps resistor limited to 5 mA to prevent injury to service personnel and to avoid inducing an Electrostatic Discharge ESD into the device 3 Use IC puller to remove existing IC from the socket 4 Noting orientation of new IC use an IC insertion tool to place new device into socket A E Match notch on 4 Device IC to notch Typical IC in socket 5 Follow the top of enclosure MS7ALLAT OW procedure in Section 8 8 8 8 Service Lake Shore Model 325 Temperature Controller User s Manual 8 10 JUMPERS There are five jumpers located on the main circuit board of the Model 325 See Figure 8 8 for the location of the jumpers reference designators JMP1 through JMP5 CAUTION Only JMP2 and JMP4 should be changed by the user Please consult with Lake Shore before changing any of the other jumpers Reference m Designator Silkscreen Default Description RUN TEST RUN Used for diagnostic purposes only Set at factory to reflect configuration of Input A where 321 330 321 330 1 mA excitation current on Pin 3 of the IMS 340 connector and 340 Pin 3 connected to shield Refer to Section 3 4 1 JMP3 D R u Set at factory to reflect configuration of Input A where TC DI RE diode resistor and TC thermocouple Set at factory to reflect configuration of Input B where 321 3
83. or minus and a key for entry ofa decimal point Refer to Section 4 1 3 4 4 2 Annunciators Display annunciators are listed as follows Sensor Input A Ku Temperature in kelvin Sensor units of ohms B or B Sensor Input B Cute Temperature in degrees Celsius Sensor units of millivolts Setpoint 5 Sensor units of volts Rus Remote If a displayed sensor input channel 18 being used to control the currently selected Loop the display annunciator for that sensor input will be underlined Refer to Section 4 4 4 1 3 General Keypad Operation There are three basic keypad operations Direct Operation Setting Selection and Data Entry Direct Operation The key function occurs as soon as the key is pressed e g Loop Heater Off and Remote Local Setting Selection Allows the user to select from a list of values During a selection sequence the A or V key are used to select a parameter value After a selection is made the Enter key is pressed to make the change and advance to the next setting or the Escape key is pressed to return to the normal display without changing the present setting The instrument retains any values entered prior to pressing the Escape key Some selections are made immediately after pressing a 4 2 Operation Lake Shore Model 325 Temperature Controller User s Manual General Keypad Operation Continued function key like Heater Range Most are part of a string of settings
84. performance from any precision instrument follow the grounding and shielding instructions in the User s Manual In addition the installer of the Model 325 should consider the following Shield measurement and computer interface cables Leave no unused or unterminated cables attached to the instrument Make cable runs as short and direct as possible Higher radiated emissions is possible with long cables Do not tightly bundle cables that carry different types of signals Lake Shore Model 325 Temperature Controller User s Manual TABLE OF CONTENTS Chapter Section Title Page 1 INTRODUCTION re 1 1 1 0 PRODUCT DESCRIPTIONS Rec E RED S 1 1 1 1 SENSOR SELECTION 2 reiecit litt bete e A een eben 1 4 1 2 1 6 1 3 SAFETY SUMMARY itt te ip rtc re Fre ao usar Eo qu RR Rue 1 8 1 4 SAFETY SYMBOLS 1 m 1 9 2 COOLING SYSTEM 2 1 2 0 bi ge see e eec 2 1
85. placeholder so that the CRVHDR command parameters match the CRVHDR query parameters The temperature coefficient is determined by the first two points in the curve CRVHDR Curve Header Query Input Format Returned Format CRVPT Input Format Remarks Example CRVPT Input Format Returned Format Remarks CRVHDR curve term nn curve Valid entries 1 36 lt name gt SN format limit value lt coefficient gt term aaaaaaaaaaaaaaa aaaaaaaaaa n tnnn nnn n Refer to command for description Curve Data Point Command CRVPT curve index units value temp value gt term nn nnn nnnnnnn nnnnnnn curve lt index gt lt units value gt Specifies which curve to configure Valid entries 21 35 Specifies the points index in the curve Valid entries 1 200 Specifies sensor units for this point to 6 digits temp value gt Specifies the corresponding temperature in kelvin for this point to 6 digits Configures a user curve data point CRVPT 21 2 0 10191 470 000 N term Sets User Curve 21 second data point to 0 10191 sensor units and 470 000 K Curve Data Point Query CRVPT lt curve gt lt index gt term nn nnn curve Specifies which curve to query 1 35 index Specifies the points index in the curve 1 200 units value temp value gt term nnnnnnn nnnnnnn Refer to command for description R
86. potential between two points of a conductor carrying a constant current of one ampere when the power dissipated between these points is equal to one watt volt ampere VA The SI unit of apparent power The volt ampere is the apparent power at the points of entry of a single phase two wire system when the product of the RMS value in amperes of the current by the RMS value in volts of the voltage is equal to one watt W The SI unit of power The watt is the power required to do work at the rate of 1 joule per second References 1 Sybil P Parker Editor McGraw Hill Dictionary of Scientific and Technical Terms Fifth Edition New York McGraw Hill 1994 IBSN 0 07 113584 7 2 Christopher J Booth Editor 7 76 New EEE Standard Dictionary of Electrical and Electronic Terms IEEE Std 100 1992 Fifth Edition New York Institute of Electrical and Electronics Engineers 1993 IBSN 1 55937 240 0 3 Nelson Robert A Guide For Metric Practice Page BG7 8 Physics Today Eleventh Annual Buyer s Guide August 1994 ISSN 0031 9228 coden PHTOAD A 6 Glossary of Terminology Lake Shore Model 325 Temperature Controller User s Manual APPENDIX B TEMPERATURE SCALES B1 0 DEFINITION Temperature is a fundamental unit of measurement that describes the kinetic and potential energies of the atoms and molecules of bodies When the energies and velocities of the molecules in a body are increased the temperature is increased whether the
87. resistor to the Model 325 input using proper 4 lead connection techniques configure the DMM to read VDC and attach to the resistor 4 Adjust the current source calibration pot R97 for Input A and R103 for Input on the Model 325 main board until the DMM reads exactly the value calculated in Step 2 to 0 00002 VDC 5 l mA current source verification Configure the input for the 1000 Plat 250 range Accurately determine the value of the 1 resistor using the DMM Determine the verification value by multiplying the actual resistance of the 1 KQ Iresistor by 1 mA 7 Attach the 1 resistor to the Model 325 input using proper 4 lead connection techniques configure the DMM to read VDC and attach to the resistor 8 Verify the voltage across to resistor to be within 0 3 of the value calculated in Step 6 8 12 Service Lake Shore Model 325 Temperature Controller User s Manual 8 12 2 3 Diode Input Ranges Calibration Purpose To determine the input offset and gain errors when the input is configured for the diode ranges and provide offset and gain calibration constants back to the Model 325 Process 1 2 Configure the input for the diode range to be calibrated Reset the calibration constants to their default values using the CALZ and CALG commands EXAMPLE Input A Range GaAlAs Diode Zero Offset Command CALZ A 1 0 Gain Command CALG A 1 1 Short all four terminals I I
88. sample yielding a true internal field Hint given by Hin H DM where is the volume magnetization and D is the demagnetization factor D is dependent on the sample geometry and orientation with respect to the field deviation The difference between the actual value of a controlled variable and the desired value corresponding to the setpoint Dewar flask A vessel having double walls the space between being evacuated to prevent the transfer of heat and the surfaces facing the vacuum being heat reflective used to hold liquid gases and to study low temperature phenomena Invented by Sir James Dewar 1842 1923 a Scottish physical chemist differential permeability The slope of a B versus curve dB dH differential susceptibility The slope of a M versus curve xa dM dH dimensionless sensitivity Sensitivity of a physical quantity to a stimulus expressed in dimensionless terms The dimensionless temperature sensitivity of a resistance temperature sensor is expressed as Sg T R dR dT which is also equal to the slope of R versus T on a log log plot that is S4 d InR d InT Note that the absolute temperature in kelvin must be used in these expressions drift instrument An undesired but relatively slow change in output over a period of time with a fixed reference input 016 drift is usually expressed in percent of the maximum rated value of the variable being measured electromagnet A device in which a magnet
89. setpoint the controller gradually increases heating power If the feedback information is slow the controller puts too much heat into the system before it is told to reduce heat The excess heat causes a temperature overshoot which degrades control stability The best way to improve thermal lag is to pay close attention to thermal conductivity both in the parts used and their junctions 2 5 3 Two Sensor Approach There is a conflict between the best sensor location for measurement accuracy and the best sensor location for control For measurement accuracy the sensor should be very near the sample being measured which is away from the heating and cooling sources to reduce heat flow across the sample and thermal gradients The best control stability is achieved when the feedback sensor is near both the heater and cooling source to reduce thermal lag If both control stability and measurement accuracy are critical it may be necessary to use two sensors one for each function Many temperature controllers including the Model 325 have two sensor inputs for this reason Cooling System Design 2 7 Lake Shore Model 325 Temperature Controller User s Manual 2 5 4 Thermal Mass Cryogenic designers understandably want to keep the thermal mass of the load as small as possible so the system can cool quickly and improve cycle time Small mass can also have the advantage of reduced thermal gradients Controlling very small mass is difficult because there
90. setpoint ramping press the Control Setup key then press the Enter key until you see the following display Use the A or W key to select Setpoint Ramp On Press the Enter key You will see the following The ramp rate is entered using the numeric keypad which includes the numbers 0 9 and decimal point The user can set ramp rate in degrees per minute with a range of 0 to 100 and a resolution of 0 1 Ramp rate will be in the same units specified for the setpoint Press the Enter key Any subsequent change in setpoint will ramp at the specified rate If you wish to pause a ramp press the Setpoint key then immediately press the Enter key This stops the ramp at the current setpoint but leaves the ramping function activated Then to continue the ramp enter a new setpoint To turn the ramping feature off press the Control Setup key then press the Enter key until you see the following screen Use the A or V key to select Setpoint Ramp Off Press the Enter key then the Escape key The Ramp LED will turn off Operation 4 23 Lake Shore Model 325 Temperature Controller User s Manual 4 13 HEATER RANGE AND HEATER OFF The heater output for Loop 1 is a well regulated variable DC current source while the heater output for Loop 2 is a variable DC voltage source Both heater outputs are optically isolated from the sensor input circuits to reduce interference and ground loops The heater output for
91. setting the unit to defaults Displayed Field Command DISPFLD lt field gt lt item gt lt source gt term n n n lt field gt Specifies field to configure 1 4 lt item gt Specifies item to display in the field 0 Off 1 Input A 2 Input B 3 Setpoint 4 Heater Output source IfItem is 1 or 2 specifies input data to display Valid entries 1 kelvin 2 Celsius 3 sensor units DISPFLD 2 1 1 term Displays kelvin reading for Input A in display field 2 Displayed Field Query DISPFLD lt field gt term n field Specifies field to query 1 4 lt item gt lt source gt term n n Refer to command for description Remote Operation 6 27 FILTER Input Format Example FILTER Input Format Returned Format HTR Input Returned Format HTRRES Input Format HTRRES Input Returned Format IEEE Input Format Example Lake Shore Model 325 Temperature Controller User s Manual Input Filter Parameter Command FILTER lt input gt lt off on gt lt points gt lt window gt term a n nn nn lt input gt Specifies input to configure A or B lt off on gt Specifies whether the filter function is 0 Off or 1 On lt points gt Specifies how many data points the filtering function uses Valid range 2 to 64 lt window gt Specifies what percent of full scale reading limits the filtering function Reading changes greater than this per
92. the first time make a few small 2 to 5 degree changes in setpoint and let the Model 325 go until the control channel annunciator stops blinking In many cases AutoTune is able to arrive at a better set of control settings There are situations where AutoTune is not the answer The algorithm can be fooled when cooling systems are very fast very slow have a large thermal lag or have a nonlinear relationship between heater power and load temperature If a load can reach a new setpoint in under 10 seconds with an appropriate I setting 7500 the cooling system is too fast for AutoTuning Systems with a very small thermal mass can be this fast Adding mass is a solution but is unappealing to users who need the speed for fast cycle times Manual tuning is not difficult on these systems because new settings be tested very quickly Some systems are too slow for the AutoTune algorithm Any system that takes more than 15 minutes to stabilize at a new setpoint is too slow with an appropriate I setting lt 5 Thermal lag can be improved by using the sensor and heater installation techniques discussed above Lag times up to a few seconds should be expected much larger lags can be a problem System nonlinearity is a problem for both AutoTune and manual tuning It is most commonly noticed when controlling near the maximum or minimum temperature of a temperature control system It is not uncommon however for a user to buy a cryogenic cooling system spec
93. 0920 5 12 59 8 438800 87 50 113 2 161610 309 00 6 9 829330 5 72 60 8 366570 90 00 114 2 534960 315 00 7 9 827470 6 35 61 8 292900 92 50 115 2 943070 321 50 8 9 825370 7 00 62 8 217810 95 00 116 3 355100 328 00 9 9 822890 7 70 63 8 141330 97 50 117 3 770870 334 50 10 9 820010 8 45 64 8 047780 100 50 118 4 190420 341 00 11 9 816880 9 20 65 7 952190 103 50 119 4 613650 347 50 12 9 813290 10 00 66 7 854690 106 50 120 5 040520 354 00 13 9 809180 10 85 67 7 755260 109 50 121 5 470960 360 50 14 9 804510 11 75 68 7 653960 112 50 122 5 938380 367 50 15 9 799510 12 65 69 7 550790 115 50 123 6 409870 374 50 16 9 793900 13 60 70 7 445790 118 50 124 6 885210 381 50 17 9 787610 14 60 71 7 338970 121 50 125 7 364360 388 50 18 9 780590 15 65 72 7 230370 124 50 126 7 881760 396 00 19 9 773150 16 70 73 7 120010 127 50 127 8 403380 403 50 20 9 764910 17 80 74 6 989110 131 00 128 8 928940 411 00 21 9 755820 18 95 75 6 855790 134 50 129 9 493760 419 00 22 9 746230 20 10 76 6 720200 138 00 130 10 0629 427 00 23 9 735700 21 30 72 6 582330 141 50 131 10 6361 435 00 24 9 724650 22 50 78 6 442220 145 00 132 11 2494 443 50 25 9 713080 23 70 79 6 299900 148 50 133 11 867 452 00 26 9 699960 25 00 80 6 155400 152 00 134 12 5253 461 00 27 9 686220 26 30 81 6 008740 155 50 135 13 188 470 00 28 9 671890 27 60 82 5 859960 159 00 136 13 892 479 50 29 9 655790 29 00 83 5 687430 163 00 137 14 6005 489 00 30 9 638980 30 40 84 5 512090 16
94. 10 Up 18 03 8 11 Loop 19 04 9 12 1 20 Enter 05 Escape 13 2 21 no key pressed since power up 06 Heater Off 14 3 99 multiple keys pressed simultaneously 07 4 15 Down 8 18 Lake Shore Model 325 Temperature Controller User s Manual APPENDIX A GLOSSARY OF TERMINOLOGY absolute zero The temperature of 273 16 C or 459 69 F or 0 thought to be the temperature at which molecular motion vanishes and a body would have no heat energy Alumel M An aluminum nickel alloy of which the negative lead of a Type thermocouple is composed ambient temperature The temperature of the surrounding medium such as gas or liquid which comes into contact with the 1 apparatus ampere The constant current that if maintained in two straight parallel conductors of infinite length of negligible circular cross section and placed one meter apart in a vacuum would produce between these conductors a force equal to 2 x 107 newton per meter of length This is one of the base units of the SI ampere turn A MKS unit of magnetomotive force equal to the magnetomotive force around a path linking one turn of a conducting loop carrying a current of one ampere or 1 26 gilberts ampere meter A m The SI unit for magnetic field strength 1 ampere meter 47 1000 oersted 0 01257 oersted analog controller A
95. 2 17 15 56 3 47357 3 85 89 3 98609 0 233 24 3 38672 16 60 57 3 47726 3 68 90 4 05672 0 190 25 3 38829 16 05 58 3 48122 3 51 91 4 14042 0 153 26 3 38993 15 50 59 3 48524 3 35 92 4 24807 0 120 27 3 39165 14 95 60 3 48955 3 19 93 4 40832 0 088 28 3 39345 14 40 61 3 49421 3 03 94 4 57858 0 067 29 3 39516 13 90 62 3 49894 2 88 95 4 76196 0 055 30 3 39695 13 40 63 3 50406 2 73 96 4 79575 0 051 31 3 39882 12 90 64 3 50962 2 58 97 4 81870 0 050 32 3 40079 12 40 65 3 51528 2 44 33 3 40286 11 90 66 3 52145 2 30 Curve Tables Lake Shore Model 325 Temperature Controller User s Manual Table D 7 Type K Nickel Chromium vs Nickel Aluminum Thermocouple Curve T om Oe eee ose 1 6 45774 3 15 48 6 10828 57 4 95 2 95792 192 142 18 1482 714 5 2 6 45733 3 68 49 6 08343 594 96 2 82629 196 143 19 2959 741 5 3 6 45688 4 2 50 6 05645 61 5 97 2 6762 200 5 144 20 8082 TTT 4 6 45632 4 78 51 6 02997 63 5 98 2 52392 205 145 23 1752 832 5 5 6 45565 5 4 52 6 00271 65 5 99 2 36961 209 5 146 24 5166 864 6 6 45494 6 53 5 97469 67 5 100 2 21329 214 147 25 6001 889 5 7 6 4541 6 65 54 5 94591 69 5 101 2 05503 218 5 148 26 5536 912 8 6 4531 7 35 55 5 91637 71 5 102 1 87703 223 5 149 27 4199 932 5 9 6 45201 8 05 56 5 8861 73 5 103 1 69672 228 5 150 28 2413 952 10 6 45073 8 8 57 5 85508 75 5 104 1 51427 233 5 151 29 0181 970 5 11 6 44934 9 55 58 5 82334 77 5 105 1 32972 238 5
96. 2 50 79 3 913940 153 50 134 6 746540 424 00 25 6 176930 23 70 80 3 821970 157 00 135 7 099510 431 00 26 6 168310 25 00 81 3 728520 160 50 136 7 455590 438 00 27 6 159280 26 30 82 3 633620 164 00 137 7 814630 445 00 28 6 149830 27 60 83 3 537260 167 50 138 8 176630 452 00 29 6 139220 29 00 84 3 439460 171 00 139 8 541540 459 00 30 6 128130 30 40 85 3 340240 174 50 140 8 909320 466 00 31 6 116580 31 80 86 3 239610 178 00 141 9 306450 473 50 32 6 103700 33 30 87 3 122930 182 00 142 9 706830 481 00 33 6 090300 34 80 88 3 004370 186 00 143 10 1103 488 50 34 6 075460 36 40 89 2 884040 190 00 144 10 5169 496 00 35 6 060040 38 00 90 2 761910 194 00 145 10 9264 503 50 36 6 044070 39 60 91 2 638010 198 00 146 11 3664 511 50 37 6 025470 41 40 92 2 512340 202 00 147 11 8098 519 50 38 6 006200 43 20 93 2 384920 206 00 148 12 2564 5271 50 39 5 986280 45 00 94 2 255770 210 00 149 12 7342 536 00 40 5 965730 46 80 95 2 124900 214 00 150 13 2155 544 50 41 5 942210 48 80 96 1 992320 218 00 151 13 7 553 00 42 5 917930 50 80 97 1 858060 222 00 152 14 1879 561 50 43 5 892970 52 80 98 1 705090 226 50 153 14 7079 570 50 44 5 864730 55 00 99 1 549970 231 00 154 15 2314 579 50 45 5 835680 57 20 100 1 392820 235 50 155 15 7583 588 50 46 5 805860 59 40 101 1 233640 240 00 156 16 2887 5971 50 47 5 776670 61 50 102 1 072450 244 50 157 16 8224 606 50 48 5 741100 64 00 103 0 909257 249 00 158 17 3594 615 50 49 5 704560 66 50 104 0 7
97. 2 59940 29 001 4 2 59840 001 4 2 65910 D 2 Curve Tables Lake Shore Model 325 Temperature Controller User s Manual Table D 4 Lake Shore PT 100 1000 Platinum RTD Curves Break PT 100 PT 1000 point Temp K Ohms Q Temp K Ohms Q 1 030 0 3 820 030 0 38 20 2 032 0 4 235 032 0 42 35 3 036 0 5 146 036 0 51 46 4 038 0 5 650 038 0 56 50 5 040 0 6 170 040 0 61 70 6 042 0 6 726 042 0 67 26 7 046 0 7 909 046 0 79 09 8 052 0 9 924 052 0 99 24 9 058 0 12 180 058 0 121 80 10 065 0 15 015 065 0 150 15 11 075 0 19 223 075 0 192 23 12 085 0 23 525 085 0 235 25 13 105 0 32 081 105 0 320 81 14 140 0 46 648 140 0 466 48 15 180 0 62 980 180 0 629 80 16 210 0 75 044 210 0 750 44 17 270 0 98 784 270 0 987 84 18 315 0 116 270 315 0 1162 70 19 355 0 131 616 355 0 1316 16 20 400 0 148 652 400 0 1486 52 21 445 0 165 466 445 0 1654 66 22 490 0 182 035 490 0 1820 35 23 535 0 198 386 535 0 1983 86 24 585 0 216 256 585 0 2162 56 25 630 0 232 106 630 0 2321 06 26 675 0 247 712 675 0 2477 12 27 715 0 261 391 715 0 2613 91 28 760 0 276 566 760 0 2765 66 29 800 0 289 830 800 0 2898 30 Curve Tables Lake Shore Model 325 Temperature Controller User s Manual Table D 5 Lake Shore RX 102A Rox Curve Break Temp Break Temp Break Temp point 00 point oe K point 980 1 3 02081 40 0 36 3 05186 13 50 71 3 17838 2 96 2 3 02133 38 8 37 3 05322 13 10 72 3 18540 2 81 3 3 02184 37 7 3
98. 30 321 330 1 mA excitation current on Pin 3 of the IMS 340 sem connector and 340 Pin 3 connected to shield Refer to Section 3 4 1 5 D R o Set at factory to reflect configuration of Input B where TC DI RE diode resistor and TC thermocouple 8 11 ERROR MESSAGES The following are error message that may be displayed by the Model 325 during operation Message Description Di sabl Input is turned off Ho Curve Input has no curve 5 Over Input is at or over full scale sensor units 5 Under Input is at or under negative full scale sensor units T uer Input at or over the high end of the curve T Under Input at or under the low end ofthe curve Cannot Communicate with Inrut Processor The main microprocessor has lost communication with the sensor input microprocessor Defective Defective NOVRAM Contact Lake Shore Invalid HOVRAM Invalid data or contents in NOVRAM Press and hold the Escape key for 20 seconds to initialize NOVRAM Refer to Section 4 18 Service 8 9 Lake Shore Model 325 Temperature Controller User s Manual JMP2 JMP3 o Chee 155 ae Jod l uio cad Er 16725 Ls EH om 227 Go guo g m wu 2s 88 ca ZR gu zn JMP4 JMP5 wid AT zia c U48 JMP1 II
99. 36 475 5 28 2 95269 120 59 4 28662 481 29 2 78168 130 60 4 64037 498 30 2 60639 140 61 4 68168 500 31 2 42737 150 This thermocouple is longer sold by Lake Shore Curve Tables D 9 Lake Shore Model 325 Temperature Controller User s Manual Table D 11 Chromel AuFe0 07 Thermocouple Curve p ee ae a ae 1 5 279520 3 15 35 3 340820 115 00 69 1 313400 332 50 2 5 272030 3 78 36 3 253410 119 50 70 1 511140 341 50 3 5 263500 4 46 37 3 165360 124 00 71 1 709250 350 50 4 5 253730 5 20 38 3 076690 128 50 72 1 928940 360 50 5 5 242690 6 00 39 2 977480 133 50 73 2 127070 369 50 6 5 229730 6 90 40 2 877550 138 50 74 2 324710 378 50 7 5 214770 7 90 41 2 776950 143 50 75 2 523070 387 50 8 5 196980 9 05 42 2 675700 148 50 76 2 643480 393 00 9 5 176250 10 35 43 2 563610 154 00 74 2 708890 396 00 10 5 150910 11 90 44 2 450770 159 50 78 2 764030 398 50 11 5 116700 13 95 45 2 337230 165 00 79 2 797580 400 00 12 5 049770 17 90 46 2 223010 170 50 80 2 950200 406 50 13 5 002120 20 70 47 2 097700 176 50 81 3 008310 409 00 14 4 938000 24 50 48 1 971630 182 50 82 3 031200 410 00 15 4 876180 28 20 49 1 844890 188 50 83 3 218040 418 00 16 4 801670 32 70 50 1 706840 195 00 84 3 300110 421 50 17 4 648620 42 00 51 1 568040 201 50 85 4 000810 451 50 18 4 569170 46 80 52 1 428520 208 00 86 4 246390 462 00 19 4 499080 51 00 53 1 277520 215 00 87
100. 42732 0 722511 1 10974 3 1 45206 0 755487 1 11204 1 48578 0 786992 1 11414 1 53523 0 817025 1 11628 1 56684 0 844538 11853 1 58358 0 869583 12090 1 59690 0 893230 12340 1 60756 0 914469 12589 1 62125 0 934356 12913 1 62945 0 952903 13494 1 63516 0 970134 14495 1 63943 0 986073 16297 1 64261 0 998925 1 17651 1 64430 3 gt _ 1 1 1 1 1 1 1 1 Table D 3 Lake Shore DT 500 Series Silicon Diode Curves longer in production Break DT 500 D Curve DT 500 E1 Curve point Temp K Volts Temp K Volts 1 365 0 0 19083 330 0 0 28930 2 345 0 0 24739 305 0 0 36220 3 305 0 0 36397 285 0 0 41860 4 285 0 0 42019 265 0 0 47220 5 265 0 0 47403 240 0 0 53770 6 240 0 0 53960 220 0 0 59260 7 220 0 0 59455 170 0 0 73440 8 170 0 0 73582 130 0 0 84490 9 130 0 0 84606 100 0 0 92570 10 090 0 0 95327 075 0 0 99110 11 070 0 1 00460 060 0 1 02840 12 055 0 1 04070 040 0 1 07460 13 040 0 1 07460 036 0 1 08480 14 034 0 1 09020 034 0 1 09090 15 032 0 1 09700 032 0 1 09810 16 030 0 1 10580 030 0 1 10800 17 029 0 1 11160 029 0 1 11500 18 028 0 1 11900 028 0 1 12390 19 027 0 1 13080 027 0 1 13650 20 026 0 1 14860 026 0 1 15590 21 025 0 1 17200 025 0 1 18770 22 023 0 1 25070 024 0 1 23570 23 021 0 1 35050 022 0 1 32570 24 017 0 1 63590 018 0 1 65270 25 015 0 1 76100 013 0 1 96320 26 013 0 1 90660 009 0 2 17840 27 009 0 2 11720 004 0 2 53640 28 003 0 2 53660 003 0
101. 44065 253 50 159 17 9297 625 00 50 5 667130 69 00 105 0 576893 258 00 160 18 5037 634 50 51 5 628800 71 50 106 0 407776 262 50 161 19 1116 644 50 52 5 589590 74 00 107 0 217705 267 50 162 19 7538 655 00 53 5 549510 76 50 108 0 025325 272 50 163 20 4611 666 50 54 5 508560 79 00 109 0 188573 278 00 164 20 8627 673 00 55 5 466760 81 50 110 0 404639 283 50 D 8 Curve Tables Lake Shore Model 325 Temperature Controller User s Manual Table D 10 Chromel AuFe0 03 Thermocouple Curve Breakpoint mV Temp K Breakpoint mV Temp K 1 4 6667 3 5 32 2 24537 160 2 4 62838 6 35 33 2 06041 170 3 4 60347 8 15 34 1 86182 180 5 4 4 58043 9 75 35 1 66004 191 5 4 53965 12 5 36 1 47556 200 5 6 4 47226 16 95 37 1 0904 220 7 4 43743 19 3 38 0 73397 237 5 8 4 39529 22 2 39 0 68333 240 9 4 34147 26 40 0 3517 256 10 4 29859 29 1 41 0 2385 261 5 11 4 26887 31 3 42 0 078749 277 12 4 22608 34 5 43 0 139668 280 13 4 2018 36 3 44 0 426646 294 5 14 4 02151 49 8 45 0 546628 300 5 15 3 94549 55 4 46 0 858608 316 16 3 87498 60 5 47 0 938667 320 17 3 80464 65 5 48 1 3456 340 18 3 73301 70 5 49 1 7279 358 5 19 3 65274 76 50 1 76905 360 5 20 3 5937 80 51 2 20705 381 5 21 3 51113 85 5 52 2 51124 396 22 3 45023 89 5 53 2 69878 405 23 3 43451 90 5 54 2 94808 417 24 3 37842 94 55 3 13562 426 25 3 35469 95 5 56 3 43707 440 5 26 3 28237 100 57 3 85513 460 5 27 3 11919 110 58 4 171
102. 5 68 3 16002 3 42 103 4 54568 0 066 34 3 04936 14 30 69 3 16593 3 26 104 4 79803 0 050 35 3 05058 13 90 70 3 17191 3 11 D 4 Curve Tables Lake Shore Model 325 Temperature Controller User s Manual Table D 6 Lake Shore RX 202A Rox Curve Break Temp Break Temp Break Temp point on 0 point ge K point ign a 1 3 35085 40 0 34 3 40482 11 45 67 3 52772 2 17 2 3 35222 38 5 35 3 40688 11 00 68 3 53459 2 04 3 3 35346 37 2 36 3 40905 10 55 69 3 54157 1 92 4 3 35476 35 9 37 3 41134 10 10 70 3 54923 1 80 5 3 35612 34 6 38 3 41377 9 65 71 3 55775 1 68 6 3 35755 33 3 39 3 41606 9 25 72 3 56646 1 57 7 3 35894 32 1 40 3 41848 8 85 73 3 57616 1 46 8 3 36039 30 9 41 3 42105 8 45 74 3 58708 1 35 9 3 36192 29 7 42 3 42380 8 05 75 3 59830 1 25 10 3 36340 28 6 43 3 42637 7 70 76 3 61092 1 150 11 3 36495 27 5 44 3 42910 7 35 77 3 62451 1 055 12 3 36659 26 4 45 3 43202 7 00 78 3 63912 0 965 13 3 36831 25 3 46 3 43515 6 65 79 3 65489 0 880 14 3 37014 24 2 47 3 43853 6 30 80 3 67206 0 800 15 3 37191 23 2 48 3 44230 5 94 81 3 69095 0 725 16 3 37377 22 2 49 3 44593 5 62 82 3 71460 0 645 17 3 37575 21 2 50 3 44984 5 30 83 3 73889 0 575 18 3 37785 20 2 51 3 45355 5 02 84 3 76599 0 510 19 3 37942 19 50 52 3 45734 4 76 85 3 79703 0 448 20 3 38081 18 90 53 3 46180 4 48 86 3 83269 0 390 21 3 38226 18 30 54 3 46632 4 22 87 3 87369 0 336 22 3 38377 17 70 55 3 47012 4 02 88 3 92642 0 281 23 3 3852
103. 7 00 138 15 3507 499 00 31 9 621500 31 80 85 5 334130 171 00 139 16 1432 509 50 32 9 602020 33 30 86 5 153520 175 00 140 16 9403 520 00 33 9 581740 34 80 87 4 970330 179 00 141 17 7798 531 00 34 9 560710 36 30 88 4 784590 183 00 142 18 6624 542 50 35 9 537440 37 90 89 4 596330 187 00 143 19 5881 554 50 36 9 513290 39 50 90 4 405600 191 00 144 20 5573 567 00 37 9 486720 41 20 91 4 212440 195 00 145 21 5702 580 00 38 9 457560 43 00 92 3 992330 199 50 146 22 627 593 50 39 9 427340 44 80 93 3 769140 204 00 147 23 7279 607 50 40 9 396080 46 60 94 3 543070 208 50 148 24 873 622 00 41 9 363810 48 40 95 3 314120 213 00 149 26 0623 637 00 42 9 330540 50 20 96 3 082340 217 50 150 27 3356 653 00 43 9 296270 52 00 97 2 847790 222 00 151 28 6935 670 00 44 9 257090 54 00 98 2 610520 226 50 152 30 1761 688 50 45 9 216690 56 00 99 2 343820 231 50 153 31 8242 709 00 46 9 175140 58 00 100 2 073770 236 50 154 33 7187 732 50 47 9 132450 60 00 101 1 800570 241 50 155 36 1028 762 00 48 9 088620 62 00 102 1 524210 246 50 156 41 8502 833 00 49 9 043710 64 00 103 1 244740 251 50 157 44 2747 863 00 50 8 997710 66 00 104 0 962207 256 50 158 46 2907 888 00 51 8 950650 68 00 105 0 676647 261 50 159 48 1007 910 50 52 8 902530 70 00 106 0 359204 267 00 160 49 8256 932 00 53 8 840980 72 50 107 0 009079 273 00 161 51 5056 953 00 54 8 777760 75 00 108 0 344505 279 00 Curve Tables D 7 Lake Shore Model 325 Temperature Controller User
104. 8 3 05466 12 70 73 3 19253 2 67 4 3 02237 36 6 39 3 05618 12 30 74 3 20027 2 53 5 3 02294 35 5 40 3 05780 11 90 75 3 20875 2 39 6 3 02353 34 4 41 3 05952 11 50 76 3 21736 2 26 7 3 02411 33 4 42 3 06135 11 10 77 3 22675 2 13 8 3 02472 32 4 43 3 06330 10 70 78 3 23707 2 00 9 3 02537 31 4 44 3 06537 10 30 79 3 24842 1 87 10 3 02605 30 4 45 3 06760 9 90 80 3 26000 1 75 11 3 02679 29 4 46 3 06968 9 55 81 3 27169 1 64 12 3 02749 28 5 47 3 07190 9 20 82 3 28462 1 53 13 3 02823 27 6 48 3 07428 8 85 83 3 29779 1 43 14 3 02903 26 7 49 3 07685 8 50 84 3 31256 1 33 15 3 02988 25 8 50 3 07922 8 20 85 3 32938 1 23 16 3 03078 24 9 51 3 08175 7 90 86 3 34846 1 130 17 3 03176 24 0 52 3 08447 7 60 87 3 37196 1 020 18 3 03280 23 1 53 3 08786 7 25 88 3 39220 0 935 19 3 03393 22 2 54 3 09150 6 90 89 3 41621 0 850 20 3 03500 21 4 55 3 09485 6 60 90 3 44351 0 765 21 3 03615 20 6 56 3 09791 6 35 91 3 47148 0 690 22 3 03716 19 95 57 3 10191 6 05 92 3 50420 0 615 23 3 03797 19 45 58 3 10638 5 74 93 3 54057 0 545 24 3 03882 18 95 59 3 11078 5 46 94 3 58493 0 474 25 3 03971 18 45 60 3 11558 5 18 95 3 63222 0 412 26 3 04065 17 95 61 3 12085 4 90 96 3 68615 0 354 27 3 04164 17 45 62 3 12622 4 64 97 3 75456 0 295 28 3 04258 17 00 63 3 13211 4 38 98 3 82865 0 245 29 3 04357 16 55 64 3 13861 4 12 99 3 91348 0 201 30 3 04460 16 10 65 3 14411 3 92 100 4 01514 0 162 31 3 04569 15 65 66 3 14913 3 75 101 4 14432 0 127 32 3 04685 15 20 67 3 15454 3 58 102 4 34126 0 091 33 3 04807 14 7
105. AINED SERVICE PERSONNEL INPUTA INPUT B LOOP2 HEATER OUT HI LO N 100 120 220 240 10 6 Voltage 100 120 1 6 250 5 20 50 60 Hz 150 220 240 1 6 250 5 20 IEEE 488 INTERFACE F 325 3 l wmf Description Details D Loop 1 Heater Out Banana Jack and Ground Screw Terminal Section 3 6 Figure 8 4 5 232 DTE 9 pin D Style Connector Section 6 2 1 Figure 8 6 Q Line Input Assembly Section 3 3 Figure 8 2 IEEE 488 INTERFACE Connector Section 8 7 2 Figure 8 7 d 2 Sections 3 4 3 5 Figure 8 3 and 3 4 Loop 2 Heater Section 3 6 Figure 8 5 Figure 3 1 Model 325 Rear Panel 3 2 Installation Lake Shore Model 325 Temperature Controller User s Manual 3 3 LINE INPUT ASSEMBLY This section describes how to properly connect the Model 325 to line power Please follow these instructions carefully to ensure proper operation of the instrument and the safety of operators Line Cord Power Switch Fuse Input O Off l On Drawer N 100 120 220 240 V 10 6 Voltage 50 60 Hz 85 220 240V 1 6AT250V 5 20 100 120 1 6AT250V 5x20mm F 325 3 2 wmf Figure 3 2 Line Input Assembly 3 3 1 Line Voltage Model 325 has four different AC line voltages configurations so that it can be operated from line pow
106. Advanced Operation Lake Shore Model 325 Temperature Controller User s Manual 5 3 4 SoftCal with Silicon Diode Sensors Lake Shore silicon diode sensors incorporate remarkably uniform sensing elements that exhibit precise monotonic and repeatable temperature response For example the Lake Shore DT 470 Series of silicon diode sensors has a repeatable temperature response from 2 K to 475 K These sensors closely follow the Standard Curve 10 response and routinely interchange with one another SoftCal is an inexpensive way to improve the accuracy of an already predictable sensor NOTE Standard Curve 10 is the name of the temperature response curve not its location inside the Model 325 Standard Curve 10 is stored in curve location number 1 in the Model 325 A unique characteristic of DT 400 Series diodes is that their temperature responses pass through 28 K at almost exactly the same voltage This improves SoftCal algorithm operation by providing an extra calibration data point It also explains why SoftCal calibration specifications are divided into two temperature ranges above and below 28 K See Figure 5 1 Point 1 Calibration data point at or near the boiling point of helium 4 2 K Temperatures outside 2 K to 10 K are not allowed This data point improves between the calibration data point and 28 K Points 2 and 3 improve temperatures above 28 K Point 2 Calibration data point at or near the boiling point of nitrogen 77 35 K Temper
107. An ice bath is often used to reference the measurement end to 0 Celsius so most curves are normalized to that temperature Room temperature compensation replaces an ice bath by monitoring the temperature of the thermocouple terminals and normalizing the reading mathematically RS 232C Bi directional computer serial interface standard defined by the Electronic Industries Association EIA The interface is single ended and non addressable Glossary of Terminology A 5 Lake Shore Model 325 Temperature Controller User s Manual Seebeck effect The development of a voltage due to differences in temperature between two junctions of dissimilar metals in the same circuit self heating Heating of a device due to dissipation of power resulting from the excitation applied to the device The output signal from a sensor increases with excitation level but so does the self heating and the associated temperature measurement error sensitivity The ratio of the response or change induced in the output to a stimulus or change in the input Temperature sensitivity of a resistance temperature detector is expressed as S dR dT setpoint The value selected to be maintained by an automatic controller serial interface A computer interface where information is transferred one bit at a time rather than one byte character at a time as in a parallel interface RS 232C is the most common serial interface SI Syst me International d Unit s See Internationa
108. E DEWARS Cryogenic containers Dewars must be operated in accordance with the manufacturer instructions Safety instructions will also be posted on the side of each Dewar Cryogenic Dewars must be kept in a well ventilated place where they are protected from the weather and away from any sources of heat A typical cryogenic Dewar is shown in Figure C 1 NON MAGNETIC LIQUID HELIUM KEEP UPRIGHT Dewar bmp Figure C 1 Typical Cryogenic Storage Dewar Handling LHe and LN C 1 Lake Shore Model 325 Temperature Controller User s Manual C4 0 LIQUID HELIUM AND NITROGEN SAFETY PRECAUTIONS Transferring LHe and LN and operation of the storage Dewar controls should be in accordance with the manufacturer supplier s instructions During this transfer it is important that all safety precautions written on the storage Dewar and recommended by the manufacturer be followed WARNING Liquid helium and liquid nitrogen are potential asphyxiants and can cause rapid suffocation without warning Store and use in area with adequate ventilation DO NOT vent container in confined spaces DO NOT enter confined spaces where gas may be present unless area has been well ventilated If inhaled remove to fresh air If not breathing give artificial respiration If breathing is difficult give oxygen Get medical help WARNING Liquid helium and liquid nitrogen can cause severe frostbite to the eyes or skin DO NOT touch fro
109. IT B 450 term If the temperature of the sensor on Input B exceeds 450 K all control outputs will be turned off Temperature Limit Query Firmware Version 1 5 and Later TLIMIT lt input gt term a input Specifies which input to query A or B lt limit value gt term nnnn Control Tuning Status Query TUNEST lt tuning status gt term n 0 no active tuning 1 active tuning The tuning status will return active 1 if either Loop 1 or Loop 2 is actively tuning Control Loop Zone Table Parameter Command ZONE lt loop gt lt zone gt lt setpoint limit gt lt P value gt lt I value gt lt D value gt lt mout value gt lt range gt term n nn tnnnnnn nnnnnn tnnnnnn nnnnnn tnnnnnn n term lt loop gt Specifies which loop to configure 1 or 2 lt zone gt Specifies which zone in the table to configure Valid entries are 1 10 lt setpoint limit gt Specifies the setpoint limit of this zone lt P value gt Specifies the P for this zone 0 1 to 1000 lt I value gt Specifies the I for this zone 0 1 to 1000 lt D value gt Specifies the D for this zone 0 to 200 lt mout value Specifies the manual output for this zone 0 to 100 lt range gt Specifies the heater range for this zone if loop 1 Valid entries 0 2 If loop 2 then range 1 and cannot be changed Configures the control loop zone parameters Refer to Section 2 9 ZONE 1 1 25 0 10 20 0
110. K 300K 0 8978 V 2 85 mVIK 7 mK 60 mK 92 mK 14 mK 475 K 0 3778 V 3 15 mV K 6 4 mK 38 mK 88 mK 12 8 mK 1000 PT 103 with 30K 3 660 Q 0 191 QIK 10 5 mK 23 mK 33 mK 21 mK Platinum 1 4J calibration 77K 20 38 Q 0 423 4 8 mK 15 mK 27 mK 06 mK 2 300K 110350 0 387 5 2 mK 39 mK 62 mK 10 4 mK 500K 185 668 Q 0 378 QIK 5 3 mK 60 mK 106 mK 10 6 mK Cernox CX 1050 SD 4 2K 350720 1120 8 QIK 36 uK 1 4 mK 6 4 mK 72 uK HT with 4M 77K 205670 24116 9K 16 6 mK 76 mK 92 mK 33 2 mK calibration 594670 0 1727 OK 232 mK 717 mK 757 mK 464 mK 420K 45 0300 0 0829 QIK 483 mK 1 42 1 49K 966 mK Germanium GR 200A 1000 2K 6674 Q 9930 QIK 4 uK 10 3 mK 4 3 mK 8 uK with 1 4D 4 2K 1054 526 QIK 76 uK 1 mK 5 mK 152 uK 10K 1090 384 QIK 1mK 344 mK 394 mK 32 mK 100 K 2257 Q 0 018 O K 222K 5 61 5 626 K 4 44 K Carbon CGR 1 2000 4 2K 2260 2060 QIK 20 uK 0 5 mK 4 5 mK 40 uK Glass with 4L 77K 21650 0 157 255 mK 692 mK 717 mK 510 mK calibration XOK 11999 0 018 OK 2 667 K 47K 471K 35 344 Thermo Type K 75K 5862 9 uV 15 6 uV K 26 mK 10 25 52 mK couple 300K 10753 406 10 mK 0 038 K4 Calibration not 420 mK 50 600K 13325uV 417yVK 10 mK 0 184 K ies 20 mK 1505K 49998 3 uV 36 006 uV K 12 mK 0 73K4 24 mK Typical sensor sensitivities were taken from representative calibrations for the sensor listed Control stability of th
111. LOSURE REMOVE AND REPLACE 8 8 8 9 FIRMWARE AND NOVRAM 8 8 8 10 JUMPERS ion on tert eife oe neta Sis 8 11 ERROR MESSAGES viii ide teet bie Die Hoe tun 8 12 CALIBRATION PROCEDJURE 3 a e 8 12 1 Equipment Required for Calibration 8 12 2 Diode Resistor Sensor Input 8 12 8 12 2 1 Sensor Input Calibration Setup and Serial Communication Verification 8 12 8 12 2 2 10 pA Current Source Calibration and 1 mA Current Source Verification 8 12 8 12 2 3 Diode Input Ranges 8 13 8 12 2 4 Resistive Input Ranges 8 14 8 12 3 Diode Sensor Input Calibration 1 mA Excitation 8 15 8 12 4 Thermocouple Sensor Input 8 15 8 12 4 1 Sensor Input Calibration Setup seen nennen ennemis 8 15 8 12 4 2 Thermocouple Input Ranges 8 15 8 12 5 Loop 2 Heater Calibration 2 iie dete ri eene COPI ee RIAM ER 8 16 8 12 5 1 Loop 2 Voltage Output
112. Model 325 Temperature Controller User s Manual 6 1 4 3 2 Service Request Enable Register The Service Request Enable Register is programmed by the user and determines which summary bits of the Status Byte may set bit 6 RQS MSS to generate a Service Request Enable bits are logically ANDed with the corresponding summary bits see Figure 6 4 Whenever a summary bit is set by an event register and its corresponding enable bit is set by the user bit 6 will set to generate a service request The Service Request Enable command SRE programs the Service Request Enable Register and the query command SRE reads it Reading the Service Request Enable Register will not clear it The register may be cleared by the user by sending SRE 0 From Operation Event Register From Standard Event Status Register From Output Buffer Status Byte Register STB Not Not Used Used Generate service request SRQ Reset by serial poll Read by STB Service Request Enable Register RQS MSS 7 6 5 4 13 21 1 0 128 64 32 16 8 4 2 1 Decimal SRE SRE Not Not Not Not OSB Not Used ESB Usea usea Used Used Name Figure 6 4 bmp Figure 6 4 Status Byte Register and Service Request Enable Register 6 1 4 3 3 Using Service Request SRQ and Serial Poll When a Status Byte summary bit or bit is enabled by the Service Request Enable Register and goe
113. P value can increase the time and number of attempts required to tune There are three AutoTune modes available They result in slightly different system characteristics Auto PI is recommended for most applications Auto P Sets only the P parameter value I and D are set to 0 no matter what the initial values are This mode is recommended for systems that have very long lag times or nonlinearity that prevents stable PI control Expect some overshoot or undershoot of the setpoint and stable temperature control below the setpoint value Auto Sets values for both P and I parameters D is set to zero This mode is recommended for stable control at a constant temperature It may take slightly longer to stabilize after setpoint change than Auto PID Expect some overshoot or undershoot of the setpoint and stable temperature control at the setpoint value Auto PID Sets values for P I and D parameters D is always set to 10096 This mode is recommended when setpoint changes are frequent but temperature is allowed to stabilize between changes Stability at setpoint may be worse than Auto PI in noisy systems Expect slightly less overshoot or undershoot than the other modes and control at the setpoint value 4 18 Operation Lake Shore Model 325 Temperature Controller User s Manual AutoTune Continued Once AutoTune mode is selected no activity takes place until the setpoint is changed at least 0 5 K At that time the control channel
114. Program Operation eR 6 14 6 1 6 ro bleshooting eerte me etiem ober een 6 14 Table of Contents Lake Shore Model 325 Temperature Controller User s Manual TABLE OF CONTENTS Continued Chapter Section Title Page 6 2 SERIAL INTERFACE OVERVIEW tetto cles eet 6 15 6 2 1 eene pei de 6 15 6 2 2 Hardware Suppott 2 e e ER dee e p iid 6 15 6 2 3 Character Format ee e et p viet LR es 6 16 6 2 4 553 06 51 685 2 2 duces 6 16 6 2 5 Message Flow Control iaeia 6 16 6 2 6 Changing Baud Rate ise ot 6 17 6 2 7 Serial Interface Example 6 17 6 2 7 1 Visual Basic Serial Interface Program 6 17 6 2 7 2 Program Operation Lc 6 20 6 2 8 Troubleshooting 5 7 Ashes 6 20 6 3 COMMAND SUMMARY dede EDU 6 21 6 3 1 Interface Commands Alphabetical eem 6 23 7 OPTIONS AND ACCESSORIES tere iere etate rne e ir cauaa iuo 7 1 7 0 GENERAL 4 eee eee RO eee Med ERAN
115. Q load for optimal cryocooler control flexibility Designed with ease of use functionality and value in mind the Model 325 is ideal for general purpose laboratory and industrial temperature measurement and control applications Sensor Inputs The Model 325 temperature controller features two inputs with a high resolution 24 bit analog to digital converter and separate current sources for each input Constant current excitation allows temperature to be measured and controlled down to 2 0 K using appropriate Cernox RTDs or down to 1 4 K using silicon diodes Thermocouples allow for temperature measurement and control above 1 500 K Sensors are optically isolated from other instrument functions for quiet and repeatable sensor measurements The Model 325 also uses current reversal to eliminate thermal EMF errors in resistance sensors Sensor data from each input is updated up to ten times per second with display outputs twice each second Standard temperature response curves for silicon diodes platinum RTDs ruthenium oxide RTDs and many thermocouples are included Up to fifteen 200 point CalCurves for Lake Shore calibrated temperature sensors or user curves can be stored into non volatile memory A built in SoftCal algorithm can be used to generate curves for silicon diodes and platinum RTDs for storage as user curves The Lake Shore curve handler software program allows sensor curves to be easily loaded and manipulated Sensor inputs for the Mo
116. Refer to Section 5 3 2 2 Cooling System Design Lake Shore Model 325 Temperature Controller User s Manual 2 2 3 Standard Curves Some types of sensors behave in a very predictable manner and a standard temperature response curve can be created for them Standard curves are a convenient and inexpensive way to get reasonable temperature accuracy Sensors that have a standard curve are often used when interchangeability is important Some individual sensors are selected for their ability to match a published standard curve and sold at a premium but in general these sensors do not provide the accuracy of a calibrated sensor For convenience the Model 325 has several standard curves included in firmware Lake Shore Silicon Diode Temperature Sensor Regarding accuracy there are 3 things that can be done with a temperature sensor Standard sensors are interchange able within published tolerance bands Below is a list of Standard Curve 10 DT 470 Tolerance Accuracy Bands 305 K 305 375 11 1 of Temp 1 of Temp Temperatures down to 1 4 K only with a Precision Calibrated Sensor To increase accuracy perform a SoftCal with the controller and sensor After sensor calibration the custom sensor curve replaces the standard Curve 10 A CalCurve can be generated for either SoftCal or the SoftCal Calibration A Lake Shore SoftCal applies only to Silicon Diodes A 2 point SoftCal takes dat
117. ST Input Format Returned Format Remarks Lake Shore Model 325 Temperature Controller User s Manual Control Setpoint Ramp Parameter Query RAMP lt loop gt n lt loop gt Specifies which loop to query or 2 lt off on gt lt rate value gt term n nnnnn Refer to command for description Control Setpoint Ramp Status Query RAMPST lt loop gt term n lt loop gt Specifies which loop to query 1 or 2 lt ramp status gt term n ramp status gt 0 Not ramping 1 Setpoint is ramping Heater Range Command RANGE lt loop gt lt range gt term n n lt loop gt Specifies loop to configure 1 or 2 lt range gt For loop 1 0 Off 1 Low 2 5 W 2 High 25 W For loop 2 0 Off 1 On Heater Range Query RANGE lt loop gt term n lt loop gt Specifies which loop to query 1 or 2 lt range gt term n Refer to command for description Input Reading Status Query RDGST lt input gt term a lt input gt Specifies which input to query A or B lt status bit weighting gt term nnn The integer returned represents the sum of the bit weighting of the input status flag bits A 000 response indicates a valid reading is present Bit Bit Weighting Status Indicator 0 1 invalid reading 4 16 temp underrange 5 32 temp overrange 6 64 sensor units zero 7 128 sensor units overrange 6 32 Remote Operation SCAL Input Format Remarks Example SETP
118. Section 8 2 Items Included with Model 325 Temperature Controller 1 Model 325 Instrument Model 325 User s Manual Sensor input mating connector 6 pin DIN Heater output connector dual banana for Loop 1 Heater Out Terminal block mating connector 2 pin terminal block for Loop 2 Heater Out Line Power Cord N e Line Power Cord for Alternative Voltage Included only when purchased with VAC 120 ALL power option Installation 3 1 Lake Shore Model 325 Temperature Controller User s Manual 3 2 REAR PANEL DEFINITION This section provides a description of the Model 325 rear panel connections The rear panel consists of the line input assembly RS 232 Connector INPUT A and B Sensor Input Connectors IEEE 488 INTERFACE Connector and LOOP and 2 HEATER OUT Connectors Please read the entire chapter before performing the initial setup and system checkout procedure in Section 3 7 Rear panel connector pin out details are provided in Section 8 7 CAUTION Verify AC line voltage shown in the fuse holder window is appropriate for the intended AC power input Also remove and verify the proper fuse is installed before plugging in and turning on the instrument CAUTION Always turn off the instrument before making any rear panel connections This is especially critical when making sensor to instrument connections LOOP 1 HEATER OUT RS 232 DTE WARNING NO USER SERVICEABLE PARTS INSIDE REFER SERVICING TO TR
119. Shore Model 325 Temperature Controller User s Manual 2 2 4 CalCurve The CalCurve service provides the user with a convenient way get the temperature response curve from Lake Shore calibrated sensors into instruments like the Model 325 It can be performed at the factory when calibrated sensors and instruments are ordered together The factory installed CalCurve option is Model 8001 325 and should be ordered with the calibrated sensor A CalCurve can be done in the field when additional or replacement sensors are installed Customers that have a PC compatible computer with RS 232C or IEEE 488 interface can load the curve into the instrument using one of the computer interfaces The Model 8000 CalCurve is offered on CD or via e mail free of charge at time of order to any customer who orders a calibrated sensor See Section 7 2 for details 2 3 SENSOR INSTALLATION This section highlights some of the important elements of proper sensor installation For more detailed information Lake Shore sensors are shipped with installation instructions that cover that specific sensor type and package The Lake Shore Temperature Measurement and Control Catalog includes an installation section as well To further help users properly install sensors Lake Shore offers a line of cryogenic accessories Many of the materials discussed are available through Lake Shore and can be ordered with sensors or instruments 2 31 Mounting Materials Choosing appropriate m
120. a closed circuit when actuator is in the free unenergized position normally open N O A term used for switches and relay contacts Provides an open circuit when actuator is in the free unenergized position oersted Oe The cgs unit for the magnetic field strength H 1 oersted 10741 ampere meter 4 79 58 ampere meter ohm The SI unit of resistance and of impedance The ohm is the resistance of a conductor such that a constant current of one ampere in it produces a voltage of one volt between its ends open loop A control system in which the system outputs are controlled by system inputs only and no account is taken of actual system output pascal Pa The SI unit of pressure equal to 1 N m Equal to 1 45 x 10 psi 1 0197 x 105 kg cm 7 5 10 torr 4 191 x 10 inches of water or 1 x 10 bar permeability Material parameter which is the ratio of the magnetic induction B to the magnetic field strength H u Also see Initial Permeability and Differential Permeability 4 Glossary of Terminology Lake Shore Model 325 Temperature Controller User s Manual platinum Pt A common temperature sensing material fabricated from pure platinum to make the Lake Shore PT family of resistance temperature sensor elements polynomial fit A mathematical equation used to fit calibration data Polynomials are constructed of finite sums of terms of the form 4jX where 4 is the i fit coefficient and X is some funct
121. a domestic power cord is included with all other instruments unless otherwise specified when ordered Always plug the power cord into a properly grounded receptacle to ensure safe instrument operation The delicate nature of measurements being taken with this instrument may necessitate additional grounding including ground strapping of the instrument chassis In these cases the operators safety should remain the highest priority and low impedance from the instrument chassis to safety ground should always be maintained 3 3 4 Power Switch The power switch is part of the line input assembly on the rear panel of the Model 325 and turns line power to the instrument On and Off When the circle is depressed power is Off When the line is depressed power is On Installation 3 3 Lake Shore Model 325 Temperature Controller User s Manual 3 4 DIODE RESISTOR SENSOR INPUTS This section details how to connect diode and resistor sensors to the Model 325 inputs Refer to Section 4 4 to configure the inputs The optional thermocouple input is described in Section 3 5 3 41 Sensor Input Connector and Pinout The input connectors are 6 pin DIN 45322 sockets The sensor output pins are defined in Figure 3 3 Two mating connectors 6 pin DIN plugs are included in the connector kit shipped with the instrument These are common connectors so additional mating connectors can be purchased from local electronics suppliers They can also be ordered from Lake
122. a points at 77 35 K and 305 K A 3 point SoftCal takes data points at 4 2 K 77 35 K and 305 K Typical 2 Point Accuracy 1 0K 2 K to lt 30 0 25K 30Kto 60K 0 15K 60Kto 345K 0 25K 345Kto lt 375 1 0K 375 K to 475 Typical 3 Point Accuracy 05 2 K to lt 30 0 25K 30K to 60K 0 15 K 60K to lt 345 K 0 225 345 K to lt 375 K 14 0 375 K to 475 K Enter voltages at the 2 or 3 data points into SoftCal capable controllers A calibration report comes with the sensor Precision Calibration Lake Shore precision calibrates most sensor types by taking up to 99 data points concentrated in areas of interest Typical silicon diode calibration accuracy is listed below Temp Typical Maximum 10K 12mK 20mK 10K 12 20 20 15mK 25 30K 25mK 45mK 50K 30 55mK 100K 25mK 50mK 300K 25 50 340K 100 mK 480K 100 mK A curve is fitted to these points A detailed report including Raw Temperature Data Polynomial Fits and Interpolation Tables comes with the sensor User calculates break points and manually enters data into the controller CalCurve Or Precision Calibration 8001 325 Factory downloads CalCurve breakpoint pairs into instrument 8000 Users download CalCurve breakpoint pairs in ASCII format from a CD C 325 2 1 bmp Figure 2 1 Silicon Diode Sensor Calibrations and CalCurve Cooling System Design 2 3 Lake
123. abVIEW driver contact Lake Shore for availability Serial interface Electrical format RS 232C Baud rates 9600 19200 38400 57600 Connector 9 pin D style DTE configuration Reading rate To 10 rdg s on each input General Ambient temperature 15 C to 35 C at rated accuracy 5 C to 40 C at reduced accuracy Power requirement 100 120 220 240 VAC 6 10 50 or 60 Hz 85 VA Size 216 mm W x 89 mm H 368 mm D 8 5 in x 3 5 in x 14 5 in half rack Weight 4 0 kg 8 8 Ib Approval CE mark contact Lake Shore for availability Ordering Information Standard Temperature Controllers all features included Part Number Description Input configuration cannot be changed in the field 325 Two diode RTD inputs 325 One diode RTD one thermocouple input 325 T2 Two thermocouple inputs Refer to Chapter 7 of this manual for a complete description of Model 325 options and accessories Specitications subject to change without notice 13 SAFETY SUMMARY Observe these general safety precautions during all phases of instrument operation service and repair Failure to comply with these precautions or with specific warnings elsewhere in this manual violates safety standards of design manufacture and intended instrument use Lake Shore Cryotronics Inc assumes no liability for Customer failure to comply with these requirements The Model 325 protects the operator and surrounding area from electric shock or burn mechanical hazards
124. ading the sensor signal and error in calculating a temperature using a temperature response curve Error results from the sensor being compared to a calibration standard and the temperature response of a sensor will shift with time and with repeated thermal cycling from very cold temperatures to room temperature Instrument and sensor makers specify these errors but there are things a user can do to maintain good accuracy For example choose a sensor that has good sensitivity in the most critical temperature range as sensitivity can minimize the effect of most error sources Install the sensor properly following guidelines in Section 2 3 Have the sensor and instrument periodically recalibrated or in some other way null the time dependent errors Use a sensor calibration that is appropriate for the accuracy requirement 2 1 5 Sensor Package Many types of sensors can be purchased in different packages Some types of sensors can even be purchased as bare chips without any package A sensor package generally determines its size thermal and electrical contact to the outside and sometimes limits temperature range When different packages are available for a sensor the user should consider the mounting surface for the sensor and how leads will be heat sinked when choosing 2 2 CALIBRATED SENSORS There can sometimes be confusion in the difficult task of choosing the right sensor getting it calibrated translating the calibration data into a temperatur
125. al 4 5 2 Resistor Sensor Curve Selection Once the input is setup for the Platinum Rhodium Iron or various NTC RTD sensors Section 4 4 3 you may choose temperature curve Standard curve numbers 6 and 7 being relevant to Platinum or curves 8 and 9 being relevant to Rox sensors You are also given the choice of None You may also choose from any appropriate User Curves stored in Curve Numbers 21 through 35 Data points for resistor curves are detailed in Tables D 4 through D 6 in Appendix D Press the Input Setup key Press the Enter key until you see the curve selection screen shown below Use the A or V key to cycle through the sensor curves until the desired curve is displayed Press the Enter key then the Escape key to return to the normal display 4 5 3 Thermocouple Sensor Curve Selection The following thermocouple screens are only displayed when the Model 325 hardware is configured at the factory with one or two thermocouple sensor inputs being Model 325 or T2 Once the input is setup for the thermocouple input voltage Section 4 4 4 you may choose a temperature curve Press the Input Setup key Standard curve numbers 12 through 16 being relevant You are also given the choice of None You may also choose from any appropriate User Curves stored in Curve Numbers 21 through 35 Data points for thermocouple curves are detailed in Tables D 7 through D 11 in Appendix D Press the Enter key until you see t
126. al should be retained for reshipment If not available a minimum of three inches of shock adsorbent packing material should be placed snugly on all sides of the instrument in a sturdy corrugated cardboard box The RA number should be included in the mailing label or written prominently on the outside of the box copy of the customer contact information and RA number should be included inside the box Consult Lake Shore with questions regarding shipping and packing instructions Service 8 1 Lake Shore Model 325 Temperature Controller User s Manual 8 3 FUSE DRAWER The fuse drawer supplied with the Model 325 holds the instrument line fuses and line voltage selection module The drawer holds two 5 x 20 mm time delay fuses It requires two good fuses of the same rating to operate safely Refer to Section 8 5 for details Fuse 120 Front View Side View Rear View Dual Fuse Configuration Dual_Fuse bmp Figure 8 1 Fuse Drawer 8 4 LINE VOLTAGE SELECTION Use the following procedure to change the instrument line voltage selector Verify the fuse value whenever line voltage is changed WARNING avoid potentially lethal shocks turn off controller and disconnect it from AC power before performing these procedures Identify the line input assembly on the instrument rear panel See Figure 8 2 Turn the line power switch OFF O Remove the instrument power cord With a small screwdriver release the drawer holding the
127. amp 500 mK from 325 to 1400 mK at 480 DIN Class A or Class B tolerance Three point SoftCal calibrations are performed at liquid nitrogen 77 35 K room temperature 305 K and high temperature 480 Accuracy for the PT 102 PT 103 or PT 111 platinum sensor is 250 mK from 70 to 325 and 250 mK from 325 K to 480 K 5 8 Advanced Operation Lake Shore Model 325 Temperature Controller User s Manual 5 3 5 SoftCal Calibration Curve Creation Once the calibration data points have been obtained you may create a SoftCal calibration This example illustrates SoftCal of a DT 470 diode Press the Curve Entry key Press the or V key until you see the following display Press the Enter key You can press the Escape key any time during this routine to return to the normal display Use the A or key to cycle through the sensor type you wish to SoftCal DT 470 PT 100 and PT 1000 Once the sensor type is selected press the Enter key You will see the following message NOTE copy routine allows you to overwrite an existing user curve Please ensure the curve number you are writing to is correct before proceeding with curve copy Use the A or V key to select the user curve location where the SoftCal curve will be stored You can choose any of the user curve locations 21 through 35 Press the Enter key You will see the following message Us
128. an one sensor prevents the sensor excitation current sources from operating Shielding the sensor lead cable is important to keep external noise from entering the measurement A shield is most effective when it is near the measurement potential so the Model 336 offers a shield at measurement common The shield of the sensor cable should be connected to the shield pin of the input connector The shields should not be connected to earth ground on the instrument chassis One shield should be connected to the cryostat s ground as long as it is near earth ground Connecting at more than one point will cause a ground loop which adds noise to the measurement NOTE The shells of the input connectors are at the same potential as the shield pin on the Model 336 Older Lake Shore controllers are not configured this way 3 4 4 Sensor Polarity Lake Shore sensors are shipped with instructions that indicate which sensor DT 470 SD leads are which It is important to follow these instructions for plus and minus Diode Sensor Leads leads polarity as well as voltage and current when applicable Diode sensors do not operate in the wrong polarity They look like an open circuit to the instrument Two lead resistors can operate with any lead arrangement and the sensor instructions may not specify Four lead resistors can be more dependent on lead arrangement Follow any specified lead assignment for four lead o Qo resistors Mixing leads could give a reading that
129. anana jack on the rear panel of the instrument is used for connecting HEATER OUT wires to the Loop 1 heater A standard dual banana plug mating connector is HI LO included in the connector kit shipped with the instrument This is a common jack and additional mating connectors can be purchased from local electronic suppliers or from Lake Shore P N 106 009 The heater is connected between the HI and LO terminals The ground terminal is reserved for shielding the heater leads when necessary 3 6 3 Loop 1 Heater Output Wiring Heater output current is what determines the size gauge of wire needed to connect the heater The maximum current that can be sourced from the Loop 1 heater output is A When less current is needed to power a cooling system it can be limited with range settings When setting up a temperature control system the lead wire for the heater must be capable of carrying a continuous current that is greater than the maximum current Wire manufactures recommend 30 AWG or larger wire to carry 1 A of current but there is little advantage in using wire smaller than 20 to 22 AWG outside the cryostat Inside the cryostat smaller gauge wire is often desirable It is recommended to use twisted heater leads Large changes in heater current can induce noise in measurement leads and twisting reduces the effect It is also recommended to run heater leads in a separate cable from the measurement leads to further reduce interaction
130. ange 2250 2500 Heater load for max power 250 500 Ranges 1 Heater noise lt 1 kHz 50 uV 0 01 of output Grounding Output referenced to chassis ground Heater connector Detachable terminal block Safety limits Curve temperature power up heater off short circuit protection Front Panel Display Number of reading displays Display units Reading source Display update rate Temperature display resolution Sensor units display resolution Other displays Setpoint setting resolution Heater output display Heater output resolution Display annunciators Keypad Front panel features 2 line x 20 character liquid crystal display with 5 5 mm high characters 1104 V nV Q Temperature sensor units 2 rdg s 0 001 from 0 to 99 999 0 01 from 100 to 999 99 0 1 above 1000 Sensor dependent to 5 digits Setpoint heater range and heater output user selected Same as display resolution actual resolution is sensor dependent Numeric display in percent of full scale for power or current 1 Control Input Remote Autotune 20 key membrane numeric and specific functions Front panel curve entry keypad lock out Introduction 1 7 Lake Shore Model 325 Temperature Controller User s Manual Specifications Continued nterface IEEE 488 2 interface Features SH1 T5 L4 SR1 DTO CO E1 Reading rate To 10 rdg s on each input Software support L
131. anges in setpoint or data taking between changes in the setpoint derivative should be considered See Figure 2 3 e A derivative setting of zero off is recommended when the control system is seldom changed and data is taken when the load is at steady state The derivative setting is entered into the Model 325 as a percentage of the integral time constant The setting range is 0 200 where 100 I seconds Start with a setting of 50 to 100 Again do not be afraid to make some small setpoint changes halving or doubling this setting to watch the affect Expect positive setpoint changes to react differently from negative setpoint changes 2 8 AUTOTUNING Choosing appropriate PID control settings can be tedious Systems can take several minutes to complete a setpoint change making it difficult to watch the display for oscillation periods and signs of instability With the AutoTune feature the Model 325 automates the tuning process by measuring system characteristics and along with some assumptions about typical cryogenic systems computes setting values for P I and D AutoTune works only with one control loop at a time and does not set the manual heater power output or heater range Setting an inappropriate heater range is potentially dangerous to some loads so the Model 325 does not automate that step of the tuning process When the AutoTune mode is selected the Model 325 evaluates the control loop similar to the manual tuning section
132. arameter values it helps use the values more efficiently Refer to Sections 2 7 and 4 10 for details 4 14 Operation Lake Shore Model 325 Temperature Controller User s Manual 4 7 CONTROL SETUP After the Input Setup has been completed Section 4 4 and Loop is selected Section 4 6 1 the user can begin to setup temperature control parameters Control input is the sensor input that is used for control feedback in closed loop control Either Input A or B can be assigned to either Loop 1 or 2 It is not recommended to assign both loops to one input Control input is ignored when using open loop control mode To change control input press the Control Setup key and the following screen will appear Use the A or V key to toggle between Input A and Press the Enter key to accept the setting and continue with additional selections You can press the Escape key any time to exit the routine The control setpoint can be displayed and set in temperature or sensor units Changing setpoint units does not change operation of the controller only the way the setpoint is displayed and entered A valid curve must be assigned to the control input to use temperature units To change setpoint units press the Control Setup key and press Enter until the following display appears Use the A or V key to cycle through the following setpoint units Temp K Temp and Sensor where K kelvin C degrees Celsius and Sensor
133. ard 8 6 1 Identification of Electrostatic Discharge Sensitive Components The following are various industry symbols used to label components as ESDS Q mad 2 8 6 2 Handling Electrostatic Discharge Sensitive Components Observe all precautions necessary to prevent damage to ESDS components before attempting installation Bring the device and everything that contacts it to ground potential by providing a conductive surface and discharge paths As a minimum observe these precautions 1 De energize or disconnect all power and signal sources and loads used with unit 2 Place unit on a grounded conductive work surface 3 Ground technician through a conductive wrist strap or other device using 1 MQ series resistor to protect operator Service 8 3 Lake Shore Model 325 Temperature Controller User s Manual Handling Electrostatic Discharge Sensitive Components Continued 4 6 Ground any tools such as soldering equipment that will contact unit Contact with operator s hands provides a sufficient ground for tools that are otherwise electrically isolated Place ESDS devices and assemblies removed from a unit on a conductive work surface or in a conductive container An operator inserting or removing a device or assembly from a container must maintain contact with a conductive portion of the container Use only plastic bags approved for storage of ESD material Do not handle ESDS devices unnecessarily or remove from t
134. ating Lake Shore Coaxial Cable Lake Shore sells the following types of coaxial cable CC Ultra Miniature Coaxial Cable SR Semi Rigid Coaxial Cable CRYC CryoCable Accessories included with a new Model 325 Options and Accessories 7 3 Lake Shore Model 325 Temperature Controller User s Manual BLK GREEN Figure 7 1 Model 325 Sensor and Heater Cable Assembly 10 ft P N G 112 325 20 ft P N G 112 326 P 325 7 1 bmp 7 4 MODEL 3003 HEATER OUTPUT CONDITIONER The Lake Shore Model 3003 heater output conditioner is a passive filter that reduces the already low noise present in the heater output of the Model 325 The Model 3003 connects between the heater output terminals on the rear panel of a controller and a resistive heater See Figure 7 2 Specifications are as follows Max Current 2A Max Voltage 60 V Attenuation 50 or 60 Hz line frequency 20 dB 100 Hz and above line frequency harmonics 40 dB Enclosure Size 144 mm wide 72 mm long x 165 mm deep 5 7 x 2 8 x 6 5 in Weight 1 6 kg 3 5 Ib The Model 3003 is a passive filter and requires no external power supply The High and Low terminals on the controller must be connected to the High and Low terminals marked From Controller on the Model 3003 The binding posts or a dual banana plug can be used to connect to the Model 3003 Precautions must be taken to ensure the High an
135. atinum 250 7 Thermocouple 50 mV 3 100 Q platinum 500 8 2 5V 1mA 4 1000 platinum 9 7 5V 1 mA compensation Specifies input compensation where 0 off and 1 on Reversal for thermal compensation if input 1s resistive room temperature compensation if input is thermocouple Always 0 if input is a diode INTYPE A 0 0 term Sets Input A sensor type to silicon diode Input Type Parameter Query INTYPE input term a lt input gt Specifies input to query A or B sensor type lt compensation gt term n n Refer to command for description Remote Operation 6 29 Lake Shore Model 325 Temperature Controller User s Manual KEYST Key Press Query Input KEYST term Returned lt code gt term Format nn Remarks Returns a number descriptor of the last key pressed since the last KEYST Returns 21 after initial power up Returns 00 if no key pressed since last query KRDG Kelvin Reading Query Input KRDG lt input gt term Format a lt input gt Specifies which input to query A or B Returned lt kelvin value gt term Format nnnnnn Remarks Also see the RDGST command LOCK Front Panel Keyboard Lock Command Input LOCK lt state gt lt code gt term Format n nnn state 0 Unlocked 1 Locked lt code gt Specifies lock out code Valid entries are 000 999 Remarks Locks out all front panel entries Example LOCK 1 123 term Enables keypad lock and se
136. ation constants to the EEPROM CALZ Zero Offset Calibration Constant Command Input CALZ input type value term Format a nn tnnnnnnn lt input gt Specifies which input or Loop 2 output the zero offset calibration constant will be provided to Valid entries are A or B for inputs and V for the Loop 2 output lt type gt Specifies the input sensor type Valid entries are 0 Silicon Diode or Loop 1 Heater not used 6 Thermo 25mV 1 GaAlAs Diode or Loop 2 Output 7 Thermo 50mV 2 1000 Plat 250 Reversal Off 10 100Q Plat 250 Reversal On 3 100Q Plat 500 Reversal Off 11 100Q Plat 500 Reversal On 4 1000Q Plat Reversal Off 12 10000 Plat Reversal On 5 NTC RTD Reversal Off 13 NTC RTD Reversal On lt value gt Zero offset calibration constant value Remarks Provides the zero offset calibration constant for the selected input or Loop 2 output CALZ Zero Offset Calibration Constant Query Input CALZ lt input gt lt type gt term Format a nn lt input gt A B or V lt type gt 0 7or 10 13 Returned lt value gt term Format nnnnnnn Refer to command for description KEYST Last Key Press Query Input KEYST term Returned lt code gt term Format Remarks Code returned indicates the last key that was pressed according to the table below 00 no key pressed since last query 08 5 16 Set Point 01 Heater Range 09 6 17 0 02 7
137. atures outside 50 K to 100 K are not allowed This data point improves accuracy between 28 K and 100 K Points 2 and 3 together improve accuracy to room temperature and above Point 3 Calibration data point near room temperature 305 K Temperatures outside the range of 200 K to 350 K are not allowed SoftCal Point 1 SoftCal Point 2 SoftCal Point 3 Liquid Helium Liquid Nitrogen Room Temperature Boiling Point Boiling Point Point 4 2K 77 35 305 Y Y Y e e RN 0 25 50 75 100 125 150 175 200 225 250 275 300 325 350 2 10 50 100 200 325 Acceptable Temperature Range for Silicon Diode SoftCal Inputs C 325 5 1 bmp Figure 5 1 SoftCal Temperature Ranges for Silicon Diode Sensors 5 3 2 SoftCal Accuracy with Silicon Diode Sensors A SoftCal calibration is only as good as the accuracy of the calibration points The accuracies listed for SoftCal assume 0 01 K for 4 2 K liquid helium 0 05 K for 77 35 K liquid nitrogen and 305 K room temperature points Users performing the SoftCal with Lake Shore instruments should note that the boiling point of liquid cryogen though accurate is affected by atmospheric pressure Use calibrated standard sensors if possible One point SoftCal calibrations for applications under 30 K are performed at liquid helium 4 2 K temperature Accuracy for the DT 470 SD 13 diode is 0 5 K from 2 K to lt 30 K with no accuracy change above 30 K Two point SoftCal ca
138. ay Location 3 Source Display Location 4 Source Input A Same choices Input A Same choices as Input B Display Location 1 Input B Display Location 1 Setpoint Units _ Heater Out Heater Output Loop 1 None No Display K Kelvin None Display 0 Off Heater Off C Celsius XX Low 2 5 W Heater Range Sensor V mV or 9 XX High 25 W Heater Range i or Setpoint Units and Heater Out Current or Power settings are Heater Output Loop 2 under the Control Setup key All remaining selections in this Off L2 Heater Off illustration are made under the Display Format key L2 Heater On 1 W C 325 4 2 bmp Figure 4 2 Display Definition Operation 4 3 Lake Shore Model 325 Temperature Controller User s Manual 4 2 TURNING POWER After verifying line voltage Section 3 3 plug the instrument end of the line cord included with the connector kit into the power and fuse assembly receptacle on the instrument rear Plug the opposite end of the line cord into a properly grounded three prong receptacle Place the power switch located next to the line cord receptacle to the On I position The instrument initiates the following power up sequence the instrument alarm sounds once the display shows the following startup message The normal reading display appears If the instrument does not complete the sequence or if a general error
139. ble 5 1 Typical parameters for common sensors are listed in Table 5 2 Read this section completely and gather all necessary data before beginning the process NOTE Ifthe curve you wish to enter has similar parameters to an existing curve first copy the similar curve as described in Section 5 2 3 to a new location then edit the curve to the desired parameters To enter a new user curve or edit an existing user curve press the Curve Entry key Press the or V key until you see the following display Press the Enter key Press the Escape key any time during this routine to return to the normal display Use the A or V key to cycle through the various curves Curve numbers 21 through 35 are used to copy or create new curves You can also view but not modify the standard curve numbers 01 through 20 from here For this example we will enter a new curve in location 21 Press the Enter key Advanced Operation 5 3 Lake Shore Model 325 Temperature Controller User s Manual Edit Curve Continued Use the numerical keypad to enter the applicable sensor serial number to a maximum of 10 digits For this example we will enter 0123456789 Press the Enter key Use the A or V key to cycle through the curve formats V K Q K log Q K mV K where V K volts per kelvin ohms per kelvin log Q K logarithm of the resistance per kelvin and mV K millivolts per kelvin For this exa
140. centage reset the filter Valid range 1 to 10 FILTER B 1 10 2 term Filter input B data through 10 readings with 2 of full scale window Input Filter Parameter Query FILTER lt input gt term a lt input gt Specifies input to query A or B lt off on gt points lt window gt term n nn nn Refer to command for description Heater Output Query HTR lt loop gt term heater value gt term Tnnn n heater value Loop 1 or Loop 2 heater output in percent 96 of current or power depending on setting Refer to CSET command Heater Resistance Setting command HTRRES lt loop gt lt setting gt term n n lt loop gt Specifies loop to configure 1 or 2 lt setting gt Heater Resistance Setting 1 25 Q 2 50 Q Heater Resistance Setting Query HTRRES lt loop gt term lt setting gt term n Refer to command for description IEEE 488 Interface Parameter Command IEEE lt terminator gt lt EOI enable gt lt address gt term n n nn lt terminator gt Specifies the terminator Valid entries 0 lt CR gt lt LF gt 1 lt LF gt lt CR gt 2 lt LF gt 3 no terminator must have EOI enabled lt enable gt Sets EOI mode 0 enabled 1 disabled lt address gt Specifies the IEEE address 1 30 Address 0 and 31 are reserved IEEE 0 0 4 term After receipt of the current terminator the instrument uses EOI mode uses lt CR gt lt LF gt as the new terminator and re
141. ceptacle for the instrument power cord e Consider ground strapping the instrument chassis to other instruments or computers 3 5 THERMOCOUPLE SENSOR INPUTS Model 325 TX Only The information in this section is for a Model 325 configured at the factory with one or two thermocouple sensor inputs being Model 325 or T2 Sensor connection is important when using thermocouples because the measured signal is small Many measurement errors can be avoided with proper sensor installation CAUTION Do not leave thermocouple inputs unconnected Short inputs when not in use 3 5 4 Sensor Input Terminals Attach sensor leads to the screws on the off white ceramic terminal blocks Each block has two screw terminals one positive on the I V side of the connector one negative on the I V side of the connector See Figure 3 4 The current and voltage references silkscreened on the back panel are for the diode resistor connectors For thermocouples the positive wire goes to the left side terminal and the negative wire to the right side terminal Remove all insulation then tighten the screws on the thermocouple wires Keep the ceramic terminal blocks away from heat sources including sunlight and shield them from fans or room drafts Thermocouple N Thermocouple Positive Terminal _ D D Negative Terminal V Common Thermocouple Polarities Positive Negative Type K Nickel Chr
142. cgs system of units A system in which the basic units are the centimeter gram and second Chebychev polynomials A family of orthogonal polynomials that solve Chebychev s differential equation Chebychev differential equation A special case of Gauss hypergeometric second order differential equation 1 x f x xf x nf x 0 Chromel A chromium nickel alloy of which the positive lead of Type E and thermocouples is composed closed loop See feedback control system Glossary of Terminology A 1 Lake Shore Model 325 Temperature Controller User s Manual coercive force coercive field The magnetic field strength H required to reduce the magnetic induction B in a magnetic material to zero coercivity Generally used to designate the magnetic field strength H required to reduce the magnetic induction B in a magnetic material to zero from saturation The coercivity would be the upper limit to the coercive force Constantan A copper nickel alloy of which the negative lead of Type E J and T thermocouples are composed cryogenic Refers to the field of low temperatures usually 130 F or below as defined by 173 300 f of Title 49 of the Code of Federal Regulations cryogenic fluid A liquid that boils at temperatures of less than about 110 K at atmospheric pressure such as hydrogen helium nitrogen oxygen air or methane Also known as cryogen cryostat An apparatus used to provide low temp
143. circuit or equipment is connected to the earth or to some conducting body of relatively large extent that serves in place of the earth Note It is used for establishing and maintaining the potential of the earth or of the conducting body or approximately that potential on conductors connected to it and for conducting ground current to and from the earth or of the conducting body H Symbol for magnetic field strength See Magnetic Field Strength Hall effect The generation of an electric potential perpendicular to both an electric current flowing along a thin conducting material and an external magnetic field applied at right angles to the current Named for Edwin H Hall 1855 1938 an American physicist hazard communication standard CS The OSHA standard cited in 29 CFR 1910 1200 requiring communication of risks from hazardous substances to workers in regulated facilities hertz Hz A unit of frequency equal to one cycle per second hysteresis The dependence of the state of a system on its previous history generally in the form of a lagging of a physical effect behind its cause Also see magnetic hysteresis l E E E 488 An instrumentation bus with hardware and programming standards designed to simplify instrument interfacing The addressable parallel bus specification is defined by the IEEE initial permeability The permeability determined at H 0 and B 0 initial susceptibility The susceptibility determined at 0
144. conds if used at all As a convenience to the operator the Model 325 Derivative time constant is expressed in percent of 4 the integral time The range is between 0 and 200 Start with settings of 096 5096 or 10096 and determine which setting gives you the type of control you desire Do not be surprised if the setting you prefer is 0 Note that by using a percent of integral time derivative scales automatically with changes in the integral value and does not have to be revisited frequently To set Derivative press the D key You will see the following display The Derivative rate is entered using the numeric keypad which includes the numbers 0 9 and decimal point Derivative has a range of 0 to 200 percent with a default of 0 Press the Enter key to save changes and return to the normal display Operation 4 17 Lake Shore Model 325 Temperature Controller User s Manual 4 8 4 Setting Manual Heater Power MHP Output Manual Heater Power MHP output is a manual setting of control output It can function in two different ways depending on control mode In open loop control mode the MHP output is the only output to the load The user can directly set control output from the front panel or over computer interface In closed loop control mode the MHP output is added directly to the output of the PID control equation In effect the control equation operates about the MHP output setting Manual heater power out
145. ctively The parameters must be set correctly before a curve can be used for temperature conversion or temperature control Curve Number 1 35 Name Defaults to the name User Curve for front panel entry When entering a user curve over the computer interface a curve name of up to 15 characters can be entered Serial Number Up to a 10 character sensor serial number Both numbers and letters can be entered over computer interface only numbers can be entered from the front panel Format The format parameter tells the instrument what breakpoint data format to expect Different sensor types require different formats Formats for Lake Shore sensors are V K Volts vs kelvin for diode sensors Resistance vs kelvin for platinum RTD sensors Log Q K Log resistance vs kelvin for NTC resistive sensors mV K Millivolts vs kelvin for thermocouple sensors Limit Enter a temperature limit in kelvin for the curve Default is 375 K Enter a setting of 9999 K if no limit is needed Temperature Coefficient The unit derives the temperature coefficient from the first two breakpoints The user does not enter this setting If it is not correct check for proper entry of those points A positive coefficient P indicates that the sensor signal increases with increasing temperature A negative coefficient N indicates that the sensor signal decreases with increasing temperature 5 1 2 Curve Breakpoints Temperature response data of a calibrated senso
146. cuits Operating personnel must not remove instrument covers Refer component replacement and internal adjustments to qualified maintenance personnel Do not replace components with power cable connected To avoid injuries always disconnect power and discharge circuits before touching them Do Not Substitute Parts or Modify Instrument Do not install substitute parts or perform any unauthorized modification to the instrument Return the instrument to an authorized Lake Shore Cryotronics Inc representative for service and repair to ensure that safety features are maintained Cleaning Do not submerge instrument Clean only with a damp cloth and mild detergent Exterior only 1 4 SAFETY SYMBOLS Direct current power line Equipment protected throughout by double insulation or reinforced insulation equivalent to Class II of IEC 536 see Annex H Caution High voltages danger of electric shock Background color Yellow Symbol and outline Black Alternating current power line Alternating or direct current power line Three phase alternating current power line Earth ground terminal Caution or Warning See instrument documentation Background color Yellow Symbol and outline Black Protective conductor terminal gt e uU Frame or chassis terminal On supply Off supply Fuse O Or ede Introduction 1 9 Lake Shore Model 325 Temperature Controller User s Manual This Page
147. d It helps describe the dominant time constant of the load which is used in setting integral If all has gone well the appropriate proportional setting is one ha fof the value required for sustained oscillation See Figure 2 3 b Cooling System Design 2 11 Lake Shore Model 325 Temperature Controller User s Manual Tuning Proportional Continued If the load does not oscillate in a controlled manner the heater range could be set too low A constant heater reading of 100 on the display would be an indication of a low range setting The heater range could also be too high indicated by rapid changes in the load temperature or heater output with a proportional setting of less than 5 There are a few systems that will stabilize and not oscillate with a very high proportional setting and a proper heater range setting For these systems setting a proportional setting of one half of the highest setting is the best choice 2 7 3 Tuning Integral When the proportional setting is chosen and the integral is set to zero off the Model 325 controls the load temperature below the setpoint Setting the integral allows the Model 325 control algorithm to gradually eliminate the difference in temperature by integrating the error over time See Figure 2 3 d An integral setting that is too low causes the load to take too long to reach the setpoint An integral setting that is too high creates instability and can cause the load temperature to oscillate
148. d Low terminals are not reversed A diode the Model 3003 shorts the heater output if the polarity of the terminals is reversed The High and Low terminals marked 70 Heater on the Model 3003 should be attached to a resistive heater used for temperature control The binding posts or a dual banana plug can be used to connect to the Model 3003 The ground terminals on the Model 3003 continue the shield if the heater cable is shielded FROM CONTROLLER CAUTION THIS HI TERMINAL HI MU CONNECTED TO HI TERMINAL OF THE CONTROLLER e L akeShore 3003 Heater Output Conditioner F 325 7 3 bmp Figure 7 2 Model 3003 Heater Output Conditioner 7 4 Options and Accessories Lake Shore Model 325 Temperature Controller User s Manual 2 P T i Refer to Customer must use 5 64 in 2 mm hex key to remove four existing screws from sides of instrument NOTE Unit on right side mounting shown Unit on left side also possible NO Item Description P N Qty 6 1 Rack Mount Ear 107 440 1 2 Rack Mount Support 107 442 1 3 Rack Mount Panel 107 432 1 4 Rack Mount Handle 107 051 01 2 5 Screw 6 32 x 1 2 in 0 035 4 FHMS Phillips 6 Screw 8 32 x 3 8 0 081 6 FHMS Phillips P 325 7 4 jpg Figure 7 3 Model RM 1 2 Rack Mount Kit Options and Accessories 7 5 Lake Shore Model 325 Temperature Controller User s Manual Refer to Installation 4 di Procedure wx Installa
149. d condition 6 6 Remote Operation Lake Shore Model 325 Temperature Controller User s Manual Operation 7 To T8 T4 T3 T2 LT 728 64 32 16 8 4 2 1 Decima OPST NRDG RAMP4 RAMP2 ovLb1 ov p2 Name operation 7 6 5 4 2 T1 9 st Event 128 6 32 16 8 4 2 1 Decima Register Not N OPSTR NRDG RAMP1 RAMP2 OvLD1 ovLD2 Name L1 l and clears the register To Operation Event Summary Bit OSB of Operation Event i7 6 5 4 3 2 1 0 st Status Byte Register Enable Register 128 64 32 16 8 4 2 1 Decima See Figure 6 1 Figure 6 3 Operation Event Register Figure 6 3 bmp 6 1 4 3 Status Byte and Service Request SRQ As shown in Figure 6 1 the Status Byte Register receives the summary bits from the two status register sets and the message available summary bit from the output buffer The status byte is used to generate a service request SRQ The selection of summary bits that will generate an SRQ is controlled by the Service Request Enable Register 6 1 4 3 1 Status Byte Register The summary messages from the event registers and output buffer set or clear the summary bits of the Status Byte Register see Figure 6 4 These summary bits are not latched Clearing an event register will clear the corresponding summary bit in the Status Byte Register Reading all messages in the output buffer including any pending queries
150. d load This reduces radiation transfer to the sample space 2 4 HEATER SELECTION AND INSTALLATION There is a variety of resistive heaters that can be used as the controlled heating source for temperature control The mostly metal alloys like nichrome are usually wire or foil Shapes and sizes vary to permit installation into different systems 2 41 Heater Resistance and Power Cryogenic cooling systems have a wide range of cooling power The resistive heater must be able to provide sufficient heating power to warm the system The Model 325 can supply up to 25 W of power to a heater if the heater resistance is appropriate The Model 325 heater output current source has a maximum output of 1 A at the 25 setting or 0 71 A at the 50 setting Even though the Model 325 main heater output is a current source it has a voltage limit called the compliance voltage which is set to either 25 V or 35 4 V when the heater resistance is set to 25 O or 50 O respectively This compliance voltage also limits maximum power Max Power W at 25 O Setting Max Power W at 50 O Setting e Q5 vy 35 4 VY Voltage Limit 1 Resistance Resistance Current Limit 1 AY x Resistance 0 71 x Resistance Both limits are in place at the same time so the smaller of the two computations gives the maximum power available to the heater A heater of 50 at the 50 Q setting allows the instrument to provide its maximum power
151. dard The status system provides a method of recording and reporting instrument information and is typically used to control the Service Request SRQ interrupt line A diagram of the status system is shown in Figure 6 1 The status system is made up of register sets the Status Byte register and the Service Request Enable register Each register set consists of three types of registers condition event and enable 6 1 4 1 1 Condition Registers Each register set except the Standard Event Register set includes a condition register as shown in Figure 6 1 The condition register constantly monitors the instrument status The data bits are real time and are not latched or buffered The register is read only 6 1 4 1 2 Event Registers Each register set includes an event register as shown in Figure 6 1 Bits in the event register correspond to various system events and latch when the event occurs When an event bit is set subsequent events corresponding to that bit are ignored Set bits remain latched until the register is cleared by a query command such as ESR or a CLS command The register is read only Remote Operation 6 3 Lake Shore Model 325 Temperature Controller User s Manual 6 1 4 1 3 Enable Registers Each register set includes an enable register as shown in Figure 6 1 An enable register determines which bits in the corresponding event register will set the summary bit for the register set in the Status Byte The user may writ
152. de ede ee dde ede pete deis 4 10 4 5 1 Diode Sensor Curve Selection sarimie bend respete eed iier oven debs eo ede ea iaia 4 11 4 5 2 Resistor Sensor Curve Selection 2 dette ipie tide nd esa 4 12 4 5 3 Thermocouple Sensor Curve 4 12 4 5 4 gli MIR 4 12 ii Table of Contents Lake Shore Model 325 Temperature Controller User s Manual TABLE OF CONTENTS Continued Chapter Section Title Page 4 6 4 13 4 6 1 Control LOOPS x La dee geile 4 13 4 6 2 Control Modes rte t ete eret toten utut 4 14 4 6 3 Tuning Modes rere e a en p e e HR er e 4 14 4 7 E 4 15 4 8 MAN VAE 4 16 4 8 1 Manually Setting Proportional P 2 4 16 4 8 2 Manually Setting Integral I 4 17 4 8 3 Manually Setting Derivative D sse 4 17 4 8 4 Setting Manual Heater Power MHP eene eere 4 18 4 9 AUTOTUNE Closed Loop PID 4 18 4 10 ZONE SETTINGS Closed Loop Control eene 4 19 4 11 SETPOINT n D M E EE 4 22 4 12 owe tas ue hu etae mper enc 4 23 4 13 HEATER RANGE HEATER OFF tete be
153. del 325 are factory configured and compatible with either diodes RTDs or thermocouple sensors Your choice of two diode RTD inputs one diode RTD input and one thermocouple input or two thermocouple inputs must be specified at time of order and cannot be reconfigured in the field Software selects appropriate excitation current and signal gain levels when the sensor type is entered via the instrument front panel 4 LakeShore woe 0 e Loo M 1 2 3 ture 4 325 Temperature Controler Set MHP Saar Point 325 Front bmp Figure 1 1 Model 325 Front View Introduction 1 1 Lake Shore Model 325 Temperature Controller User s Manual Product Description Continued Temperature Control The Model 325 temperature controller offers two independent proportional integral derivative PID control loops A PID algorithm calculates control output based on temperature setpoint and feedback from the control sensor Wide tuning parameters accommodate most cryogenic cooling systems and many small high temperature ovens A high resolution digital to analog converter generates a smooth control output The user can set the PID values or the AutoTuning feature of the Model 325 can automate the tuning process Control loop 1 heater output for the Model 325 is well regulated variable DC current source The output can provide up to 25 W of continuous power to 50 or 25 heater load and includes a lower ra
154. described in Section 2 7 One difference is that the Model 325 does not initiate changes to control settings or setpoint for the purpose of tuning t only gathers data and changes control settings after the user changes the setpoint Unexpected or unwanted disturbances to the control system can ruin experimental data being taken by the user 2 12 Cooling System Design Lake Shore Model 325 Temperature Controller User s Manual AutoTuning Continued When the user selects a new setpoint the Model 325 logs the change in temperature at the load and the change in heater output that was required to make the load temperature change The old control settings are used while data is being logged so a good initial guess of settings can improve the efficiency of the AutoTune feature Once the load temperature is at or near the new setpoint the Model 325 looks at the logged data to calculate the best P I and D settings values Those values are then loaded and used as the control parameters so the control loop can stabilize at the new setpoint AutoTune does not function during a ramp because the dominant time constant of the load is disguised by the ramp rate The control channel annunciator blinks to indicate that tuning data is being logged The control channel annunciator stops blinking when the tuning process is complete The control channel annunciator will not blink again until the user changes the setpoint If AutoTune does not give desired results
155. e and heat sources Even in a well controlled system unwanted heat sources like thermal radiation and heat conducting through mounting structures can cause gradients For best accuracy sensors should be positioned near the sample so that little or no heat flows between the sample and sensor This may not however be the best location for temperature control as discussed below 2 3 3 Thermal Conductivity The ability of heat to flow through a material is called thermal conductivity Good thermal conductivity is important in any part of a cryogenic system that is intended to be the same temperature Copper and aluminum are examples of metals that have good thermal conductivity while stainless steel does not Non metallic electrically insulating materials like alumina oxide and similar ceramics have good thermal conductivity while G 10 epoxy impregnated fiberglass does not Sensor packages cooling loads and sample holders should have good thermal conductivity to reduce temperature gradients Surprisingly the connections between thermally conductive mounting surfaces often have very poor thermal conductivity 2 3 4 Contact Area Thermal contact area greatly affects thermal conduction because a larger area has more opportunity to transfer heat Even when the size of a sensor package is fixed thermal contact area can be improved with the use of a gasket material A soft gasket material forms into the rough mating surface to increase the area of the t
156. e electronics only in an ideal thermal system Non HT version maximum temperature 325 Accuracy specification does not include errors from room temperature compensation Introduction 1 5 Lake Shore Model 325 Temperature Controller User s Manual 1 2 SPECIFICATIONS Input Specifications Sensor A Electronic Measurement Electronic Temperature a pen d Temperature Control Coefficient 9 at 25 C Coefficient Stability Negative 0Vto2 5V 10 pA 0 05 23 100 0 4 uV Soho of rdg of rdg C 20 uV Diode 2 80 pV 20 Negative 0Vto7 5V 10 pA 0 05 23 100 pV 10 pV 0 01 of rdg 0 0005 of rdg C Positive 000500 1 mAs 10 ones MTM apro 240 Posit 0 04 Q 0 2 MQ ositive 00105000 Q 1 100 mQ 20 mo 0 02 of rdg 0 0005 of rdg 2C 40 mQ NTC RTD Negative 0097800 10pA2005 10m2 somo 0006 ofrdgyec 80me 2 1 uV 0 2 uV gt Positive 25 mV NA 1 uV 0 4 0 05 of rdg 0 0015 of rdg C 0 8 uV ermocouple m FTV 02 uV e Positive 1H u 0 05 of rdg 0 0015 ofrdgrc 2080 Control stability of the electronics only in ideal thermal system Current source error has negligible effect on measurement accuracy Diode input excitation can be set to 1 mA Current source error is removed during calibration 5 Accuracy specification does not include errors fro
157. e response curve that the Model 325 can understand then getting the curve loaded into the instrument Lake Shore provides a variety of calibration and curve loading services to fit different accuracy requirements and budgets 2 2 4 Traditional Calibration Calibration is done by comparing a sensor with an unknown temperature response to an accepted standard Lake Shore temperature standards are traceable to the U S National Institute of Standards and Testing NIST or the National Physical Laboratory in Great Britain These standards allow Lake Shore to calibrate sensors from 50 mK to above room temperature Calibrated sensors are more expensive than uncalibrated sensors of the same type because of the labor and capitol equipment used in the process This type of calibration provides the most accurate temperature sensors available from Lake Shore Errors from sensor calibration are almost always smaller than the error contributed by the Model 325 The Lake Shore Temperature Measurement and Control Catalog has complete accuracy specifications for calibrated sensors Calibrated sensors include the measured test data printed and plotted the coefficients of a Chebychev polynomial that has been fitted to the data and two tables of data points to be used as interpolation tables Both interpolation tables are optimized to allow accurate temperature conversion The smaller table called a breakpoint interpolation table is sized to fit into instruments like
158. e the Model 325 in closed loop control mode with manual PID tuning then turn integral derivative and manual output settings off Enter a setpoint several degrees above the cooling systems lowest temperature Enter a low proportional setting of approximately 5 or 10 and then enter the appropriate heater range as described above The heater display should show a value greater than zero and less than 100 The load temperature should stabilize at a temperature below the setpoint If the load temperature and heater meter swing rapidly the heater range may be set too high and should be reduced Very slow changes in load temperature that could be described as drifting are an indication of a proportional setting that is too low which is addressed in the next step Gradually increase the proportional setting by doubling it each time At each new setting allow time for the temperature of the load to stabilize As the proportional setting is increased there should be a setting which the load temperature begins a sustained and predictable oscillation rising and falling in a consistent period of time See Figure 2 3 a The goal is to find the proportional value in which the oscillation begins do not turn the setting so high that temperature and heater output changes become violent Record the proportional setting and the amount of time it takes for the load change from one temperature peak to the next The time is called the oscillation period of the loa
159. e the numerical keypad to enter the applicable sensor serial number to a maximum of 10 digits For this example we will enter 0123456789 Press the Enter key NOTE IfPoint 1 is not being used press the Enter key with both settings at their default value and advance to Point 2 Advanced Operation 5 9 Lake Shore Model 325 Temperature Controller User s Manual SoftCal Calibration Curve Creation Continued Use the numerical keypad to enter the measured data point at or near the boiling point of helium 4 2 K Temperatures outside the range of 2 10 K are not permitted The message Invalid Point Please Reenter is displayed if either point is outside the acceptable range For this example we will enter 1 62999 Press the Enter key The cursor will jump to the temperature reading Again use numerical keypad to enter the temperature the measurement was taken at For this example we will enter 4 18 K Press the Enter key NOTE If Point 2 is not being used press the Enter key with both settings at their default value and advance to Point 3 Use the numerical keypad to enter the measured data point at or near the boiling point of nitrogen 77 35 K Temperatures outside the range of 50 100 K are not permitted For this example we will enter 1 02111 Press the Enter key The cursor will jump to the temperature reading Again use numerical keypad to enter the temperature the measurement was taken at
160. e to or read from an enable register Each event register bit is logically ANDed to the corresponding enable bit of the enable register When an enable register bit is set by the user and the corresponding bit is set in the event register the output summary of the register will be set which in turn sets the summary bit of the Status Byte register oie na Status Register Not cue exe Not ave Not oec N ESR Used Used Used Output Buffer Standard Event Status Enable 7 6 5 4 3 2 1 0 Bit ee pes en oe a wan m ESE ESE Used Used Used ame PON Power On zz CME Command Error EXE Execution Error QYE 7 Query Error OPC Operation Complete Status e z 6e 5 4 3 2 1 0 RQS Generate service request Reset by serial poll MSS Read by STB aeta EB e Tsape Enable piss Not Not Not Not Operation OSB Operation Summary Bit Condition 7 6 5 4 3 2 1 si RQS Service Request Register Not 2 Master summary status BI odere reoc fewer fewwzfonorfouns Name ES Event Status Summary Bi MAV Message Available Summary Bit Event UM Register NRDG RAMP1 RAMP2 ov p1 ov o2 Name OPSTR na Bit Name ee het ES Register i reefa ponen ns tme OPSTE RAMP1 Loop 1 Ramp Done COM Processor Communication Error RAMP2 Loop 2 Ramp Done CAL Calibration Error
161. e user must be careful to build a robust system and account for the voltage range and power up state of the control output 3 6 9 Boosting Output Power There are temperature control systems that require more power than the Model 325 can provide An auxiliary DC power supply can be used to boost the output of the Model 325 Programmable power supplies are available that use a low current programming voltage as an input to control a high current voltage output Loop 2 provides an ideal programming voltage for an auxiliary power supply The only drawback with using the Loop 2 output to program an auxiliary supply is that it has only one heater range Although the heater resistance setting for Loop 2 does provide two different voltage scaling options 25 Q setting 0 to 5 V 50 Q setting 0 to 10 V the output resolution of each setting is the same The heater output for Loop 1 has two ranges Using the Low range will improve resolution but the Loop 1 output is in current not voltage To use Loop 1 to program a larger power supply a programming resistor be placed across the heater output to produce a programming voltage The programming voltage is related to output current by Vorogram Fiprogram x loutput 3 8 Installation Lake Shore Model 325 Temperature Controller User s Manual Boosting Output Power Continued The resistor must be chosen to convert a full scale current from the highest heater output range being used to the fu
162. eading Registers Any register in the status system may be read using the appropriate query command Some registers clear when read others do not Refer to Section 6 1 4 1 8 The response to a query will be a decimal value that corresponds to the binary weighted sum of all bits in the register Table 6 1 The actual query commands are described later in this section Table 6 1 Binary Weighting of an 8 Bit Register Position B7 B6 BS B4 B3 B2 Decimal 128 64 32 16 8 4 Weighting 27 2 27 e 25 2 BO 2 1 21 20 Example If bits 0 2 and 4 are set a query of the register will return a decimal value of 21 1 4 16 6 1 4 1 7 Programming Registers The only registers that may be programmed by the user are the enable registers All other registers in the status system are read only registers To program an enable register send a decimal value that corresponds to the desired binary weighted sum of all bits in the register refer to Table 6 1 The actual commands are described later in this section 6 1 4 1 8 Clearing Registers The methods to clear each register are detailed in Table 6 2 Table 6 2 Register Clear Methods Register Method Example Condition Registers None registers are not latched Event Registers Standard Event Status Register Operation Event Register Query the event register ESR clears Standard Event Status register
163. eat sinking is to cool the leads to a temperature as close to the sensor as possible This can be accomplished by putting a significant length of lead wire in thermal contact with every cooled surface between room temperature and the sensor Lead wires can be adhered to cold surfaces with varnish over a thin electrical insulator like cigarette paper They can also be wound onto a bobbin that is firmly attached to the cold surface Some sensor packages include a heat sink bobbin and wrapped lead wires to simplify heat sinking 2 3 9 Thermal Radiation Thermal black body radiation is one of the ways heat is transferred Warm surfaces radiate heat to cold surfaces even through a vacuum The difference in temperature between the surfaces is one thing that determines how much heat is transferred Thermal radiation causes thermal gradients and reduces measurement accuracy Many cooling systems include a radiation shield The purpose of the shield is to surround the load sample and sensor with a surface that is at or near their temperature to minimize radiation The shield is exposed to the room temperature surface of the vacuum shroud on its outer surface so some cooling power must be directed to the shield to keep it near the load temperature If the cooling system does not include an integrated radiation shield or one cannot be easily made one alternative is to wrap several layers of super insulation aluminized mylar loosely between the vacuum shroud an
164. eater Zone Settings AutoTune and Heater Range Operation 4 13 Lake Shore Model 325 Temperature Controller User s Manual Control Loops Continued Table 4 3 Comparison of Control Loops 1 and 2 4 6 2 Control Modes The Model 325 offers two control modes closed loop and open loop To select a control mode refer to Section 4 7 Closed Loop Control Closed loop control often called feedback control is the control mode most often associated with temperature controllers In this mode the controller attempts to keep the load at exactly the user entered setpoint temperature To do this it uses feedback from the control sensor to calculate and actively adjust the control output or heater setting The Model 325 uses a control algorithm called PID that refers to the three terms used to tune the controller for each unique system Manual heater power output can also be used during closed loop control Closed loop control is available for both control loops and offers several methods of tuning Open Loop Control Open loop control is less complicated than closed loop control but is also less powerful Open loop control mode allows the user to directly set the manual heater power output for Loop 1 and Loop 2 using only the Manual Heater Power MHP parameter During Open Loop control only the heater range and MHP Output parameters are active the setpoint control sensor and PID parameters are ignored This type of control guarantees constant po
165. ecify a range larger than necessary If an experiment is being done at liquid helium temperature a very high sensitivity is needed for good measurement resolution at that temperature That same resolution may not be required to monitor warm up to room temperature Two different sensors may be required to tightly cover the range from helium to room temperature but lowering the resolution requirement on warm up may allow a less expensive one sensor solution Another thing to consider when choosing a temperature sensor is that instruments like the Model 325 are not able to read some sensors over their entire temperature range Lake Shore sells calibrated sensors that operate down to 50 millikelvin mK but the Model 325 is limited to above 1 kelvin K in its standard configuration 2 1 2 Sensor Sensitivity Temperature sensor sensitivity is a measure of how much a sensor signal changes when the temperature changes It is an important sensor characteristic because so many measurement parameters are related to it Resolution accuracy noise floor and even control stability depend on sensitivity Many sensors have different sensitivities at different temperatures For example a platinum sensor has good sensitivity at higher temperatures but has limited use below 30 K because its sensitivity drops sharply It is difficult to determine if a sensor has adequate sensitivity over the experimental temperature range This manual has specifications Section 1 2 t
166. efore applying power to the Temperature Controller Damage to the sensor may occur if connected with power on 4 Verify your sensor installation in the liquid nitrogen environment Then plug the control sensor connector in INPUT A and the sample sensor connector in INPUT B Details of sensor hardware connections are detailed in Section 3 4 5 Connect the heater to the banana jacks labeled HEATER OUTPUT A 50 Q heater allows the maximum power output of 25 W if the heater resistance setting is set to 50 O A 25 O heater allows the maximum power output of 25 W ifthe heater resistance setting is set to 25 O Details of heater installation are in Sections 2 4 and 3 6 6 Ensure any other rear panel connections are connected before applying power to the unit This includes the RS 232 Section 6 2 1 and IEEE 488 Section 8 7 2 connectors 7 Plug line cord into receptacle 8 Turn the power switch to the on I position The front panel will briefly display the following 9 The typical display shown below will now appear The front panel display is divided into four areas The default display settings place the Sensor A reading in the upper left the Sensor B reading in the upper right the Setpoint in the lower left and the heater output of Loop 1 in percent in the lower right All temperature readings are in kelvin Each of these display areas is individually configurable by pressing the Display Format key and follow
167. egister Not Not Not _ ESE ESE oe Name Figure 6 2 Standard Event Status Register Figure_6 2 bmp 6 1 4 2 2 Operation Event Register Set The Operation Event Register reports the following interface related instrument events ramp done new reading overload Any or all of these events may be reported in the operation event summary bit through the enable register see Figure 6 3 The Operation Event Enable command OPSTE programs the enable register and the query command OPSTE reads it OPSTR reads and clears the Operation Event Register OPST reads the Operation Condition register The used bits of the Operation Event Register are described as follows Processor Communication Error COM Bit 7 This bit is set when the main processor cannot communicate with the sensor input processor Calibration Error CAL Bit 6 This bit is set if the instrument is not calibrated or the calibration data has been corrupted New Sensor Reading NRDG Bi Loop 1 Ramp Done RAMP1 Bi Loop 2 Ramp Done RAMP2 Bi Sensor Overload A OVLD1 Bit Sensor Overload B OVLD2 Bit 0 t 4 This bit is set when there is a new sensor reading t 3 This bit is set when a loop 1 setpoint ramp is completed t 2 This bit is set when a loop 2 setpoint ramp is completed This bit is set when the sensor A reading is in the overload condition 9 WM This bit is set when the sensor B reading is in the overloa
168. ei bs eve 4 1 4 1 FRONT PANEL DESCRIPTION regere ei ignit 4 1 4 1 1 Keypad Definitions 2 2t etre 4 1 4 1 2 Annurnclators anre ode de ere ae m eS 4 2 4 1 3 General Keypad Operation nennen nennen 4 2 4 1 4 Display Detinition MEE 4 3 4 2 TURNING ROWER QN ini ate pas oat RO P et Re 4 4 4 3 DISPLAY FORMAT AND SOURCE UNITS 6 4 4 4 4 SECO rec etti te ti ML Ld deo cades 4 6 4 4 1 Diode Sensor Input Setup 10 pA Excitation 4 6 4 4 2 Diode Sensor Input Setup 1 mA Excitation 4 6 4 4 3 Resistor Sensor Input Setup eiae nan erento eee ree Ee ene inde ege dee 4 7 4 4 3 1 Thermal EMF Compensation nirna iee a aa innen etate desee a nte ted nnne 4 8 4 4 4 Thermocouple Sensor Input 4 8 4 4 4 1 Room Temperature 4 9 4 4 4 2 Room Temperature Calibration 4 9 4 4 5 Temperature Limit For Firmware Version 1 5 and Later 4 10 4 5 CURVE SELEGTION 5 deir lene de Ie Here E
169. emperatures as the best estimates in 1989 allowed kelvin K The unit of temperature on the Kelvin Scale It is one of the base units of SI The word degree and its symbol are omitted from this unit See Temperature Scale for conversions Kelvin Scale The Kelvin Thermodynamic Temperature Scale is the basis for all international scales including the ITS 90 It is fixed at two points the absolute zero of temperature 0 K and the triple point of water 273 16 K the equilibrium temperature that pure water reaches in the presence of ice and its own vapor line regulation The maximum steady state amount that the output voltage or current changes as result of a specified change in input line voltage usually for a step change between 105 125 or 210 250 volts unless otherwise specified line voltage The RMS voltage of the primary power source to an instrument liquid helium LHe Used for low temperature and superconductivity research minimum purity 99 998956 Boiling point at 1 atm 4 2 K Latent heat of vaporization 2 6 kilojoules per liter Liquid density 0 125 kilograms per liter EPA Hazard Categories Immediate Acute Health and Sudden Release of Pressure Hazards DOT Name Helium Refrigerated Liquid DOT Label Nonflammable Gas DOT Class Nonflammable Gas DOT ID No UN 1963 Glossary of Terminology A 3 Lake Shore Model 325 Temperature Controller User s Manual liquid nitrogen Also used for low tem
170. enheit Figure B 1 Temperature Scale Comparison B3 0 CONVERSIONS To convert Fahrenheit to Celsius subtract 32 from F then divide by 1 8 or C F 32 1 8 To convert Celsius to Fahrenheit multiply C by 1 8 then add 32 or F 1 8 x C 32 To convert Fahrenheit to kelvin first convert F to C then add 273 15 To convert Celsius to kelvin add 273 15 Temperature Scales B 1 Lake Shore Model 325 Temperature Controller User s Manual Table B 1 Temperature Conversion Table 459 67 273 15 292 180 454 270 290 178 89 450 267 78 289 67 178 71 449 67 267 59 280 173 33 441 67 263 15 279 67 173 15 440 262 22 274 170 439 67 262 04 270 167 78 436 260 269 67 167 59 430 256 67 261 67 163 15 429 67 256 48 260 162 22 423 67 253 15 259 67 162 04 420 251 11 256 160 419 67 250 93 250 156 67 418 00 250 249 67 156 48 410 245 56 243 67 153 15 409 67 245 37 240 151 11 405 67 243 15 239 67 150 93 400 240 238 150 399 67 239 82 230 145 56 390 234 44 229 67 145 37 389 67 234 26 225 67 143 15 387 67 233 15 220 140 382 230 219 67 139 82 380 228 89 210 134 44 379 67 228 71 209 67 134 26 370 223 33 207 67 133 15 369 67 223 15 202 130 364 220 200 128 89 360 217 78 199 67 128 71 359 67 217 59 190 123 33 351 67 213 15 189 67 123 15 350 212 22 184 120 349 67 212 04 180 117 78 346 210
171. ents GPIB Interface e 9 80 Network adapters DEV12 Attributes 9 19 Ports COM amp LPT Interface r Termination Methods Timeouts 8 08 System devices areo SendEOlatendot Write 1 2 Terminate Read on EOS 10sec zi GPIB Address Serial Poll Primary Set EDI with EOS on Write i 1 12 n Properties Refresh R 8 bit EOS Compare Secondary NONE fio EOS Byte Readdress VB_GPIB_2 bmp Figure 6 6 DEV 12 Device Template Configuration Remote Operation Visual Basic IEEE 488 Interface Program Setup Continued Lake Shore Model 325 Temperature Controller User s Manual 7 Inthe Properties window the i IEEE Interface Program of XI dropdown list to select between the different controls of the current project 8 Set the properties of the controls as defined in Table 6 4 9 Save the program Mog Table 6 4 IEEE 488 Interface Program Control Properties Current Name Property New Value Labell Name IbIExitProgram Caption Type exit to end program Label2 Name IblCommand Caption Command Label3 Name IbIResponse Caption Response Textl Name txtCommand Text lt blank gt Text2 Name txtResponse Text lt blank gt Command1 Name cmdSend Caption Send Default True Form Name frmIEEE Caption IEEE Interface Program 10 Add code provided in Table 6 5 a Inthe Code Editor window under the Object d
172. er anywhere in the world The nominal voltage and voltage range of each configuration is shown below The recommended setting for 230 V operation is 240 V Nominal Minimum Maximum 100 V 90 V 106 V 120V 108 V 127 V 220V 198 V 233 V 240V 216V 254 V Verify that the AC line voltage indicator in the fuse drawer window shows the appropriate AC line voltage before turning the instrument on The instrument may be damaged if turned on with the wrong voltage selected Instructions for changing the line voltage configuration are given in Section 8 4 3 3 2 Line Fuse and Fuse Holder The line fuse is an important safety feature of the Model 325 If a fuse ever fails it is important to replace it with the value and type indicated on the rear panel for the line voltage setting The letter T on the fuse rating indicates that the instrument requires a time delay or slow blow fuse Fuse values should be verified any time line voltage configuration is changed Instructions for changing and verifying a line fuse are given in Section 8 5 3 3 3 Power Cord The Model 325 includes a 3 conductor power cord that mates with the 320 C14 line cord receptacle Line voltage is present on the two outside conductors and the center conductor is a safety ground The safety ground attaches to the instrument chassis and protects the user in case of a component failure A CE approved power cord is included with instruments shipped to Europe
173. er limit is required for all subsequent zones Make a copy of Figure 4 4 to plan your zones Once all zone parameters have been programmed the controller must be placed in zone tuning mode To do this press the AutoTune key Use the A or W key to select Zone Then press Enter to accept the new tuning mode Once zone is turned on the instrument will update the control settings each time the setpoint is changed to a new zone If the settings are changed manually the controller will use the new setting while it 1s in the same zone and update to the zone table settings when the setpoint is changed to a value outside that zone To enter parameter values into the zone table press the Zone Settings key You will see the following display Use the or V key to cycle through the ten zones Once the desired zone is displayed press the Enter key You will see the next display The upper setpoint limit is entered using the numeric keypad which includes the numbers 0 9 and decimal point During numeric entry you can press the Escape key one time to clear the entry and a second time to exit to the normal display NOTE The default setting for all the zone setpoints is zero 0 The Model 325 will not search for additional Zones once it encounters a setpoint of zero Operation 4 19 Lake Shore Model 325 Temperature Controller User s Manual Press the Enter key to accept the new upper limit You will see the
174. erature calibration is used to calibrate the built in compensation and is recommended when a thermocouple is first installed or any time a thermocouple 1s changed Factory calibration of the instrument is accurate to within approximately 1 K Differences in thermocouple wire and installation technique create errors greater than the instrument errors Therefore the best accuracy is achieved by calibrating with the thermocouple actually being used because it eliminates all sources of error If that is not possible use a thermocouple made from the same wire For less demanding applications a short across the input terminals will suffice If the Model 325 is configured as dual thermocouple unit calibrate both inputs even if they use the same type of thermocouple An appropriate curve must be selected and room temperature compensation must be turned on before calibration can be started There are three options for room temperature calibration Cleared The previous room temperature calibration value is cleared and no adjustment will be made to the temperature value provided by the internal temperature sensor when compensation is on No Use the room temperature calibration value determined the last time the room temperature calibration procedure was performed e Yes Perform the room temperature calibration procedure that follows Calibration Procedure 1 Attach a thermocouple sensor or direct short across the input terminals of the the
175. erature environments in which operations may be carried out under controlled conditions cryotronics The branch of electronics that deals with the design construction and use of cryogenic devices Curie temperature Tc Temperature at which a magnetized sample is completely demagnetized due to thermal agitation Named for Pierre Curie 1859 1906 a French chemist current source A type of power supply that supplies a constant current through a variable load resistance by automatically varying its compliance voltage A single specification given as compliance voltage means the output current is within specification when the compliance voltage is between zero and the specified voltage curve A set of data that defines the temperature response of a temperature sensor It is used to convert the signal from the sensor to temperature Curve 10 The voltage vs temperature characteristic followed by all DT 400 Series silicon diode temperature sensors degree An incremental value in the temperature scale there are 100 degrees between the ice point and the boiling point of water in the Celsius scale and 180 degrees between the same two points in the Fahrenheit scale demagnetization When a sample is exposed to an applied field H poles are induced on the surface of the sample Some of the returned flux from these poles is inside of the sample This returned flux tends to decrease the net magnetic field strength internal to the
176. ermal EMF voltage that is present in the same polarity regardless of current direction To turn reversal on or off press the Input Setup key and press the Enter key until the following display appears Resistor sensors have the additional choice of turning current reversal On or Off with the default being On If turned On the Model 325 will automatically reverse the polarity Press the Enter key Proceed to Section 4 5 2 to select a temperature curve or press the Escape key to return to the normal display 4 44 Thermocouple Sensor Input Setup Model 325 TX only The following thermocouple screens are only displayed when the Model 325 hardware is configured at the factory with one or two thermocouple sensor inputs being Model 325 T1 or T2 The user has the choice of two different input voltage ranges 25 mV and 50 mV The 25 mV range is recommended for cryogenic applications or higher temperatures less than 500 K Since thermocouple voltage can exceed 25 mV on some thermocouple types the 50 mV range is recommended for temperatures above 500 K The voltage range for Inputs A and B is set independently To setup a thermocouple sensor input press the Input Setup key The first screen appears as follows Use the A or V key to toggle between Input A and B Press the Enter key Use the A or V key to cycle through the sensor types shown in Table 4 1 with Thermo 25mV and Thermo 50mV bei
177. ers the flexibility to support curve SoftCal and zone entry Curve entry may be performed accurately and to full resolution via the display and keypad as well as computer interface Introduction 1 3 Lake Shore Model 325 Temperature Controller User s Manual 131 SENSOR SELECTION Table 1 1 Sensor Temperature Range Model Useful Range Magnetic Field Use Silicon Diode DT 670 SD 1 4 K to 500 K T gt 60K amp B lt 3T Silicon Diode DT 670E BR 30 K to 500 K T gt 60K amp B lt 3T Silicon Diode DT 414 1 4 K to 375 T gt 60K amp B lt 3T Silicon Diode DT 421 1 4 K to 325 K T gt 60K amp B lt 3T Diodes Silicon Diode DT 470 SD 1 4 K to 500 K T gt 60K amp B lt 3T Silicon Diode DT 471 SD 10 K to 500 K T gt 60K amp B lt 3T GaAlAs Diode TG 120 P 1 4 K to 325 K T gt 42K amp B lt 5T GaAlAs Diode TG 120 PL 1 4 K to 325 K T gt 42K amp B lt 5T GaAlAs Diode TG 120 SD 1 4 K to 500 K T gt 42K amp B lt 5T 100 Q Platinum 102 3 14 K to 873 K gt 40 amp lt 2 5 Positive Temperature 100 Q Platinum PT 111 14 K to 673 K T gt 40K amp B lt 2 5T Coefficient PTC RTDs Rhodium lron RF 800 4 1 4 K to 500 K T gt 77K amp B lt 8T Rhodium lron RF 100T U 1 4 K to 325 T gt 77K amp B lt 8T Cernox 1010 2 K to 325 K4 gt 28 lt 19 Cernox CX 1030 HT 3 5 K to 420 K 5 gt 28 lt 19 Cernox CX 1050 HT 4K to 420 25 gt 28 lt 19 Cernox CX
178. eturns a standard or user curve data point 6 26 Remote Operation CSET Input Format Example CSET Input Format Returned Format DFLT Input Remarks DISPFLD Input Format Example DISPFLD Input Format Returned Format Lake Shore Model 325 Temperature Controller User s Manual Control Loop Parameter Command CSET lt loop gt lt input gt lt units gt lt powerup enable gt lt current power gt term n a n n n lt loop gt Specifies which loop to configure 1 or 2 lt input gt Specifies which input to control from A or B lt units gt Specifies setpoint units Valid entries 1 kelvin 2 Celsius 3 sensor units lt powerup enable gt Specifies whether the control loop is on or off after power up where 0 powerup enable off and 1 powerup enable on lt current power gt Specifies whether the heater output displays in current or power Valid entries 1 current or 2 power CSET 1 A 1 1 term Control Loop 1 controls off of Input A with setpoint in kelvin Control Loop Parameter Query CSET lt loop gt term n lt loop gt Specifies which loop to query or 2 lt input gt lt units gt lt powerup enable gt lt current power gt term a n n n Refer to command for description Factory Defaults Command DFLT 99 term Sets all configuration values to factory defaults and resets the instrument The 99 is included to prevent accidentally
179. ety data sheet MSDS OSHA Form 20 contains descriptive information on hazardous chemicals under the OSHA Hazard Communication Standard HCS These data sheets also provide precautionary information on the safe handling of the gas as well as emergency and first aid procedures MKSA System of Units A system in which the basic units are the meter kilogram and second and the ampere is a derived unit defined by assigning the magnitude 4 x 10 to the rationalized magnetic constant sometimes called the permeability of space negative temperature coefficient N T C Refers to the sign of the temperature sensitivity For example the resistance ofa NTC sensor decreases with increasing temperature National Institute of Standards and Technology NIST Government agency located in Gaithersburg Maryland and Boulder Colorado that defines measurement standards in the United States noise electrical Unwanted electrical signals that produce undesirable effects in circuits of control systems in which they occur normalized sensitivity For resistors signal sensitivity dR dT is geometry dependent i e dR dT scales directly with consequently very often this sensitivity is normalized by dividing by the measured resistance to give a sensitivity sz in percent change per kelvin sr 100 R dR dT where T is the temperature in kelvin and R is the resistance in ohms normally closed N C A term used for switches and relay contacts Provides
180. f tuning parameters for the control system that can then be entered as zones Once the parameters are chosen AutoTune is turned off and zone tuning takes over Zone tuning has advantages over AutoTune during normal operation When a new setpoint 1s set the zone tuning automatically sets the appropriate control parameters for the destination Approach to the new setpoint 1s controlled with the best parameters AutoTune on the other hand 1s not able to learn enough about the system to change the control parameters until after the temperature gets near or to the new setpoint Approach to the new setpoint is controlled with the old parameters because they are the best available Cooling System Design 2 13 Lake Shore Model 325 Temperature Controller User s Manual This Page Intentionally Left Blank 2 14 Cooling System Design Lake Shore Model 325 Temperature Controller User s Manual CHAPTER 3 INSTALLATION 3 0 GENERAL This chapter provides general installation instructions for the Model 325 Temperature Controller Please read this entire chapter before installing the instrument and powering it on to ensure the best possible performance and maintain operator safety For instrument operating instructions refer to Chapter 4 and Chapter 5 For computer interface installation and operation refer to Chapter 6 3 4 INSPECTION AND UNPACKING Inspect shipping containers for external damage before opening them Photograph any container t
181. face but 70f the controller The related controller command is RST Event Status Enable Register Command ESE lt bit weighting gt term nnn Each bit is assigned a bit weighting and represents the enable disable mask of the corresponding event flag bit in the Standard Event Status Register To enable an event flag bit send the command ESE with the sum of the bit weighting for each desired bit Refer to Section 6 1 4 2 for a list of event flags To enable event flags 0 4 and 7 send the command 145 term 145 is the sum of the bit weighting for each bit Bit Bit Weighting Event Name 0 OPC 4 16 EXE 7 128 PON 145 Event Status Enable Register Query KESE term lt bit weighting gt term nnn Refer to Section 6 1 4 2 for a list of event flags Standard Event Status Register Query ESR term lt bit weighting gt nnn The integer returned represents the sum of the bit weighting of the event flag bits in the Standard Event Status Register Refer to Section 6 1 4 2 for a list of event flags Identification Query term lt manufacturer gt lt model gt lt serial gt lt firmware version gt term aaaa aaaaaaaa aaaaaaa n n n n manufacture Manufacturer ID model Instrument model number lt serial gt Serial number lt firmware version gt Instrument firmware version main firmware input firmware LSCI MODEL325 1234567 1 0 1 0 Remote Operation 6 23 OPC Input Remarks
182. facturer distributor The MSDS will specify the symptoms of overexposure and the first aid to be used A typical summary of these instructions is provided as follows If symptoms of asphyxia such as headache drowsiness dizziness excitation excess salivation vomiting or unconsciousness are observed remove the victim to fresh air If breathing is difficult give oxygen If breathing has stopped give artificial respiration Call a physician immediately If exposure to cryogenic liquids or cold gases occurs restore tissue to normal body temperature 98 6 F as rapidly as possible then protect the injured tissue from further damage and infection Call a physician immediately Rapid warming of the affected parts is best achieved by bathing it in warm water The water temperature should not exceed 105 F 40 C and under no circumstances should the frozen part be rubbed either before or after rewarming If the eyes are involved flush them thoroughly with warm water for at least 15 minutes In case of massive exposure remove clothing while showering with warm water The patient should not drink alcohol or smoke Keep warm and rest Call a physician immediately C2 Handling LHe and LN D1 0 GENERAL Lake Shore Model 325 Temperature Controller User s Manual APPENDIX D CURVE TABLES Standard curve tables included in the Model 325 temperature controller are as follows Curve 01 DT 470 Silicon
183. files Perform L2 1x p General GPIB Settings View devices by type View devices by coi B Computer y AT GPIB TNT Plug and Play 91 28 CDROM 9 Disk drives ISA Serial Number 004D7FA0 Display adapters Floppy disk controllers Interface Name Termination Methods 5 Hard disk controllers Pio Send EOI at end of Write Keyboard H Monitor r GPIB Address Terminate Read on EDS 7 Mouse Primary National Instruments GPIB Interfaces 0 v Set EOL wih EOS on Wie AT GPIB TNT Plug and Play 8 bit EOS Compare Network adapters Secondary xi Y Ports COM amp LPT NONE fio EOS Byt NONE H System devices 1 0 Timeout 10sec E Properties Refresh Remove System Controller VB_GPIB_I bmp Figure 6 5 GPIB Setting Configuration System Properties General Device Manager Hardware Profiles Performance 1 View devices by type National Instruments GPIB Interfaces Properties 21x Computer General Device Templates 8 28 CDROM 4 6 Disk drives National Instruments GPIB Interfaces 9 Display adapters Floppy disk controllers 5 Hard disk controllers Device Name 9 3 Keyboard Monitor Mouse National Instrum
184. ftCal Calibration Curve 5 9 6 COMPUTER INTERFACE 6 1 6 0 GENERA e tn Ule bete be tem E ES 6 1 6 1 IEEE 488 INTERFACE ree tei esi RR dde de Pe ee eua 6 1 6 1 1 IEEE 488 Interface Parameters rie eee Lei tee ee o dere ees 6 1 6 1 2 Remote Local Operation crees meni treinta ei erkennen ean nde ku sr 6 2 6 1 3 IEEE 488 Command Str ctUre iueenn iic contenere enne Po Ht er sacre 6 2 6 1 3 1 Bus Control nennen nennen 6 2 6 1 3 2 Commori COmimarids rre rete Peine Rr nre TE 6 3 6 1 3 3 Device Specific Commands cre iieri ete Te dede Eve deg 6 3 6 1 3 4 Message Strings s eo iet end Sid oath Ta ER ee ie eei ire Ene SEE 6 1 4 SICIUCESN ICD x I 6 1 4 1 OVervVIBW i ce e Me DP Mee A 6 1 4 2 Status Register Sets 6 1 4 3 Status Byte and Service Request 5 6 7 6 1 5 IEEE Interface Example Programs iie eer ee tenete i 6 10 6 1 5 1 IEEE 488 Interface Board Installation for Visual Basic Program 6 10 6 1 5 2 Visual Basic IEEE 488 Interface Program 6 10 6 1 5 3
185. g try the following commands and observe the response of the instrument Input from the user is shown in bold and terminators are added by the program The word term indicates the required terminators included with the response ENTER COMMAND IDN Identification query Instrument will return a string identifying itself RESPONSE LSCI MODEL325 1234567 1 0 1 0 term ENTER COMMAND KRDG Temperature reading in kelvin query Instrument will return a string with the present temperature reading RESPONSE 273 15 term ENTER COMMAND RANGE 1 0 Heater range command Instrument will turn off the Loop 1 heater No response will be sent ENTER COMMAND RANGE 1 Heater range query Instrument will return a string with the present Loop heater range setting RESPONSE O term ENTER COMMAND RANGE 1 1 RANGE 1 Heater range command followed by a query Instrument will change to Loop heater Low setting then return a string RESPONSE 1 term with the present setting The following are additional notes on using either IEEE 488 Interface program Ifyou enter a correctly spelled query without a nothing will be returned Incorrectly spelled commands and queries are ignored Commands and queries and should have a space separating the command and associated parameters Leading zeros and zeros following a decimal point are not needed in a command string
186. grams not included with the instrument the concepts illustrated apply to most applications 6 2 7 1 Visual Basic Serial Interface Program Setup The serial interface program works with Visual Basic 6 0 VB6 on an IBM PC or compatible with a Pentium class processor A Pentium 90 or higher is recommended running Windows 95 or better with a serial interface It uses the COMI communications port at 9600 baud Use the following procedure to develop the serial interface program in Visual Basic Start VB6 Choose Standard EXE and select Open Resize form window to desired size On the Project Menu click Components to bring up a list of additional controls available in VB6 Scroll through the controls and select Microsoft Comm Control 6 0 Select OK In the toolbar at the left of the screen the Comm Control will have appeared as a telephone icon ee eos D Select the Comm control and add it to the form 7 Add controls to form a Add three Label controls to the form b Add two TextBox controls to the form Add CommandButton control to the form d Add one Timer control to the form 8 View Menu select Properties Window 9 Inthe Properties window use the Serial Interface Program Iof x dropdown list to select between the different controls of the current project 10 Set the properties of the controls as defined in Table 6 7 11 Save the program VB Serial Lbmp Remote Operation 6 17
187. h front panel curve entry Edit curve Copy curve Erase curve as detailed below Edit allows the user to see any curve and enter or edit a curve at any Refer t ti 24 user curve location Standard curves cannot be changed S Edit Curve Erase allows the user to delete a curve from any user curve location Refer t ti 2 2 Standard curves cannot be erased Erase Curve Copy allows the user to copy a curve from any location to any user f OT 1 Refer to Section 5 2 3 curve location Curves cannot be copied into standard curve locations Copy Curve Allows creation of a new temperature curve from a standard curve and known data points entered by the user ae SoftCal To begin a curve operation press the Curve Entry key and the above selections appear Press the Next Setting key until the desired operation is highlighted and press the Enter key A curve screen appears with the curve number highlighted Change to the desired curve number with the up or down arrow key then press the Enter key to begin the desired curve operation 5 2 1 Edit Curve The Edit Curve operation 1s used to enter a new curve or edit an existing user curve Only user curves 21 to 35 can be changed Standard curves can only be viewed with the edit operation Entering the identification parameters associated with the curve is as important as entering the breakpoints Curve header parameters are listed in Ta
188. hat has significant damage before opening it If there is visible damage to the contents of the container contact the shipping company and Lake Shore immediately preferably within 5 days of receipt of goods Keep all damaged shipping materials and contents until instructed to either return or discard them Open the shipping container and keep the container and shipping materials until all contents have been accounted for Check off each item on the packing list as it is unpacked Instruments themselves may be shipped as several parts The items included with the Model 325 are listed below Contact Lake Shore immediately if there is a shortage of parts or accessories Lake Shore is not responsible for any missing items if not notified within 60 days of shipment Inspect all items for both visible and hidden damage that occurred during shipment If damage is found contact Lake Shore immediately for instructions on how to file a proper insurance claim Lake Shore products are insured against damage during shipment but a timely claim must be filed before Lake Shore will take further action Procedures vary slightly with shipping companies Keep all shipping materials and damaged contents until instructed to either return or discard them If the instrument must be returned for recalibration replacement or repair a Return Authorization RA number must be obtained from a factory representative before it is returned The Lake Shore RA procedure is given in
189. hat include sensor sensitivity translated into temperature resolution and accuracy at different points This is typical sensor response and can be used as a guide when choosing a sensor to be used with the Model 325 2 1 3 Environmental Conditions The experimental environment is also important when choosing a sensor Environmental factors such as high vacuum magnetic field corrosive chemicals or even radiation can limit the use of some types of sensors Lake Shore has devoted much time to developing sensor packages that withstand the temperatures vacuum levels and bonding materials found in typical cryogenic cooling systems Experiments done in magnetic fields are becoming very common Field dependence of temperature sensors 1s an important selection criteria for sensors used in these experiments This manual briefly qualifies the field dependence of most common sensors in the specifications Section 1 2 Detailed field dependence tables are included in the Lake Shore Temperature Measurement and Control Catalog When available specific data on other environmental factors is also included in the catalog Cooling System Design 2 1 Lake Shore Model 325 Temperature Controller User s Manual 2 1 4 Measurement Accuracy Temperature measurements have several sources of error that reduce accuracy Be sure to account for errors induced by both the sensor and the instrumentation when computing accuracy The instrument has measurement error in re
190. he Command box as described in Section 6 2 7 3 16 Press Enter or VB mp select the Send button with the mouse to send command 17 Type Exit and press Enter to quit 6 18 Remote Operation Lake Shore Model 325 Temperature Controller User s Manual Table 6 8 Visual Basic Serial Interface Program Public gSend As Boolean Global used for Send button state Private Sub cmdSend Click gSend True End Sub Routine to handle Send button press Set Flag to True Private Sub Form Load Dim strReturn As String Dim strHold As String Dim Term As String Dim ZeroCount As Integer Dim strCommand As String frmSerial Show Term Chr 13 amp Chr 10 ZeroCount 0 strReturn strHold If frmSerial MSComml PortOpen True Then frmSerial MSComml PortOpen False End If frmSerial MSComml CommPort 1 frmSerial MSComml Settings 9600 0 7 1 frmSerial MSComml InputLen 1 frmSerial MSComml PortOpen True Do Do DoEvents Loop Until gSend True gSend False strCommand frmSerial txtCommand Text strReturn strCommand UCase strCommand If strCommand EXIT Then End End If frmSerial MSComml Output strCommand amp Term If InStr strCommand lt gt 0 Then While ZeroCount 20 And strHold Chr 10 If frmSerial MSComml InBufferCount 0 Then frmSerial Timerl Enabled True Do DoEvents Main code section Used to return response Tem
191. he curve selection screen shown below Use the A or V key to cycle through the sensor curves until the desired curve is displayed Press the Enter key then the Escape key to return to the normal display 4 5 4 Filter The reading filter applies exponential smoothing to the sensor input readings If the filter is turned on for a sensor input all reading values for that input are filtered The filter is a running average so it does not change the update rate of an input Filtered readings are used for displayed readings only not for control functions The number of filter points determines how much smoothing is done One filter point corresponds to one new reading on that input A larger number of points does more smoothing but also slows the instruments response to real changes in temperature The default number of filter points is 8 which settles in approximately 50 readings or 5 seconds The filter window is a limit for restarting the filter If a single reading is different from the filter value by more than the limit the instrument will assume the change was intentional and restart the filter Filter window is set in percent of full scale range To configure a filter press the Input Setup key The first screen appears as follows Use the A or V key to toggle between Input A and B Press the Enter key until the following display appears 4 12 Operation Lake Shore Model 325 Temperature Controlle
192. he packages until actually used or tested 8 7 REAR PANEL CONNECTOR DEFINITIONS The sensor input heater output RS 232 and IEEE 488 connectors are defined in Figures 8 3 through 8 7 For thermocouple connector details refer to Figure 3 4 5 Ne C 325 3 3 bmp Description Current Voltage 1 mA Model 321 330 Configuration Shield Model 340 Configuration Refer to Section 8 10 for jumper settings that determine the output of this pin and to Section 3 4 1 for a general explanation Voltage Current Shield Figure 8 3 Sensor INPUT A and B Connector Details LOOP 1 HEATER OUT heater_out bmp Description HI Banana LO Banana Ground Screw Terminal Figure 8 4 Loop 1 Heater Output Connector Details 8 4 Service Lake Shore Model 325 Temperature Controller User s Manual Slides into slot at rear of Model 325 Use screwdriver to X 2 lock or unlock wires Terminal Block Connector Lake Shore P N 106 735 Insert wire into slot C 325 8 4 bmp Pin Description 1 Loop 2 Output Hi 2 Loop 2 Output Lo Figure 8 5 Loop 2 Heater Output Terminal Block RS 232 DTE F 325 8 5 bmp Model 325 Temperature Controller Typical Computers DE 9P DTE DB 25P DTE DE 9P DTE Pin Description Pin Description Pin Description 1 No Connection 2 TD out 1 DCD in 2 Receive Data RD
193. ibration data points can be used If using one point the algorithm shifts the entire curve up or down to meet the single point If using two points the algorithm has enough information to tilt the curve achieving good accuracy between the data points The third point extends the improved accuracy to span all three points Point 1 Calibration data point at or near the boiling point of nitrogen 77 35 K Temperatures outside 50 K to 100 K are not allowed Point 2 Calibration data point near room temperature 305 K Temperatures outside 200 K to 350 K are not allowed Point 3 Calibration data point at a higher temperature 480 K Temperatures outside 400 K to 600 K are not allowed 5 3 4 SoftCal Accuracy with Platinum Sensors A SoftCal calibration is only as good as the accuracy of the calibration points The accuracies listed for SoftCal assume 0 05 K for 77 35 K liquid nitrogen and 305 room temperature points Users performing the SoftCal with Lake Shore instruments should note that the boiling point of liquid cryogen though accurate is affected by atmospheric pressure Use calibrated standard sensors 1f possible One point SoftCal calibrations with platinum sensors have no specified accuracy Two point SoftCal calibrations for applications above 70 K are performed at liquid nitrogen 77 35 K and room temperature 305 K Accuracy for the PT 102 PT 103 or PT 111 platinum sensor is as follows 250 mK from 70 K to 325 K
194. ic field is generated as the result of electrical current passing through a helical conducting coil It can be configured as an iron free solenoid in which the field is produced along the axis of the coil or an iron cored structure in which the field is produced in an air gap between pole faces The coil can be water cooled copper or aluminum or superconductive electrostatic discharge ESD A transfer of electrostatic charge between bodies at different electrostatic potentials caused by direct contact or induced by an electrostatic field error Any discrepancy between a computed observed or measured quantity and the true specified or theoretically correct value or condition excitation Either an AC or DC input to a sensor used to produce an output signal Common excitations include constant current constant voltage or constant power Fahrenheit F Scale A temperature scale that registers the freezing point of water as 32 F and the boiling point as 212 F under normal atmospheric pressure See Temperature for conversions feedback control system A system in which the value of some output quantity is controlled by feeding back the value of the controlled quantity and using it to manipulate an input quantity so as to bring the value of the controlled quantity closer to a desired value Also known as closed loop control system four lead measurement technique where one pair of excitation leads and an independent pair of measurement
195. ice A multiline command asserts a group of signal lines All devices equipped to implement such commands do so simultaneously upon command transmission These commands transmit with the Attention ATN line asserted low The Model 325 recognizes two multiline commands LLO Local Lockout Prevents the use of instrument front panel controls DCL Device Clear Clears Model 325 interface activity and puts it into a bus idle state Finally addressed bus control commands are multiline commands that must include the Model 325 listen address before the instrument responds Only the addressed device responds to these commands The Model 325 recognizes three of the addressed bus control commands SDC Selective Device Clear The SDC command performs essentially the same function as DCL command except that only the addressed device responds GTL Go To Local The GTL command is used to remove instruments from the remote mode With some instruments GTL also unlocks front panel controls if they were previously locked out with the LLO command SPE Serial Poll Enable and SPD Serial Poll Disable Serial polling accesses the Service Request Status Byte Register This status register contains important operational information from the unit requesting service The SPD command ends the polling sequence 6 2 Remote Operation Lake Shore Model 325 Temperature Controller User s Manual 6 1 3 2 Common Commands Common Commands a
196. ies loop to configure 1 or 2 lt P value The value for control loop Proportional gain 0 1 to 1000 lt I value gt The value for control loop Integral reset 0 1 to 1000 lt D value gt The value for control loop Derivative rate 0 to 200 Setting resolution is less than 6 digits indicated PID 1 10 50 term Control Loop 1 P is 10 and I is 50 Control Loop PID Values Query PID lt loop gt term n lt loop gt lt P value gt lt I value gt lt D value gt term Specifies which loop to query or 2 nnnnnn nnnnnn nnnnnn Refer to command for description Control Setpoint Ramp Parameter Command RAMP lt loop gt lt off on gt lt rate value gt term n n tnnnnn lt loop gt Specifies which loop to configure 1 or 2 lt off on gt Specifies whether ramping is 0 Off or 1 On lt rate value gt Specifies setpoint ramp rate in kelvin per minute from 0 0 to 100 The rate is always positive but will respond to ramps up or down A ramp setting of 0 0 will cause the instrument to respond as if the ramp is off i e setpoint changes will be immediate RAMP 1 1 10 5 term When Control Loop setpoint is changed ramp the current setpoint to the target setpoint at 10 5 K minute Remote Operation 6 31 RAMP Input Format Returned Format RAMPST Input Format Returned Format RANGE Input Format RANGE Input Format Returned Format RDG
197. ifically to operate near its minimum temperature If this 1s the case try to tune the system at 5 degrees above the minimum temperature and gradually reduce the setpoint manually adjusting the control settings with each step Any time the mechanical cooling action of a cryogenic refrigerator can be seen as periodic temperature fluctuations the mass is too small or temperature too low to AutoTune 2 9 ZONE TUNING Once the PID tuning parameters have been chosen for a given setpoint the whole process may have to be done again for other setpoints significantly far away that have different tuning needs Trying to remember when to use which set of tuning parameters can be frustrating The Model 325 has a Zone feature as one of its tuning modes that can help To use the Zone feature the user must determine the best tuning parameters for each part of the temperature range of interest The parameters are then entered into the Model 325 where up to ten zones can be defined with different P I D heater range and manual heater settings A setpoint setting is assigned as the maximum temperature for that zone The minimum temperature for a zone is the setpoint for the previous zone 0 is the starting point for the first zone When Zone tuning is on each time the setpoint changes appropriate control parameters are chosen automatically Control parameters can be determined manually or by using the AutoTune feature AutoTune is a good way to determine a set o
198. indicates that the measured thermocouple input is over or under the 50 mV range 5 2 2 Erase Curve User curves that are no longer needed may be erased Erase Curve sets all identification parameters to default and blanks all breakpoint values To erase an existing user curve press the Curve Entry key Press the or V key until you see the following display Press the Enter key You can press the Escape key any time during this routine to return to the normal display Use the A or V key to cycle through the various user curve numbers 21 through 35 Y ou cannot erase the standard curve numbers 01 through 20 Once the user curve number is selected press the Enter key You will see the following message Press the Escape key to cancel or the Enter key to erase the selected user curve You now return to the normal display Advanced Operation 5 5 Lake Shore Model 325 Temperature Controller User s Manual 5 2 8 Copy Curve Temperature curves can be copied from one location inside the Model 325 to another This is a good way to make small changes to an existing curve Curve copy may also be necessary if the user needs the same curve with two different temperature limits or needs to extend the range of a standard curve The curve that is copied from is always preserved NOTE The copy routine allows you to overwrite an existing user curve Please ensure the curve number you are writing to i
199. ing the instructions in Section 4 3 Installation 3 0 Lake Shore Model 325 Temperature Controller User s Manual Initial Setup and System Checkout Procedure Continued NOTE For rated accuracy the instrument should warm up for at least 30 minutes 10 11 12 13 The default input settings are Silicon Diodes on Inputs A and B with Input A controlling using the Curve 01 DT 470 These settings can be verified by pressing the Input Setup key and following the instructions in Section 4 4 The default control mode is Manual PID where the Proportional Integral and Derivative PID settings are entered by the user The default settings are P 50 I 20 and D 0 These settings can be verified and or adjusted by pressing the PID MHP key and following the instructions in Section 4 8 For an experiment running at liquid nitrogen temperature a setpoint of 77 K is good for testing purposes Press the Setpoint key Press the 7 key twice then press the Enter key Details of setpoint setting are discussed in Section 4 11 The default setting for the heater is Off To turn the heater on press the Heater Range key Press the A or V key until Low is displayed Press the Enter key Depending on your actual setup you may need to apply more current to the heater which is accomplished by selecting the High range Details of heater settings are discussed in Section 4 13
200. iode current for Input A 1 mA must be selected for the special sensor input to be available for Input A Press the Enter key Use the A or V key to toggle between 10 uA and 1 mA to select the diode current for Input B 1 mA must be selected for the special sensor input to be available for Input B Press the Enter key To setup the diode input using 1 mA excitation press the Input Setup key The first screen appears as follows Use the A or V key to toggle between Input A and B Press the Enter key Use the A or V key to cycle through the sensor types shown in Table 4 1 with 2 5V ImA and 7 5V ImA being the relevant choices Press the Enter key Proceed to Section 4 5 1 to select a temperature curve or press the Escape key to return to the normal display 4 4 3 Resistor Sensor Input Setup Resistor sensors include the Platinum Rhodium Iron and various NTC RTD sensors e g Cernox Thermox detailed in Table 4 1 More detailed specifications are provided in Table 1 2 Input range is fixed to type of sensor The excitation current applied by the Model 325 is determined by the user selection of Negative Temperature Coefficient NTC 10 LA or Positive Temperature Coefficient PTC 1 mA To setup a resistor sensor input press the Input Setup key The first screen appears as follows Use the or V key to toggle between Input A and B Press the Enter key U
201. ion of the dependent variable positive temperature coefficient Refers to the sign of the temperature sensitivity For example the resistance of a PTC sensor increases with increasing temperature pounds per square inch psi A unit of pressure 1 psi 6 89473 kPa Variations include psi absolute psia measured relative to vacuum zero pressure where one atmosphere pressure equals 14 696 psia and psi gauge psig where gauge measured relative to atmospheric or some other reference pressure precision Careful measurement under controlled conditions that can be repeated with similar results See repeatability Also means that small differences can be detected and measured with confidence See resolution prefixes SI prefixes used throughout this manual are as follows Factor Prefix Symbol Factor Prefix Symbol 10 yotta Y 107 deci d 10 zetta Z 10 centi c 1018 107 milli m 1055 peta P 10 micro u 10 tera T 10 nano n 10 giga G 10772 106 mega M 107 femto f 10 kilo k 10718 atto a 10 hecto h 107 zepto Z 10 deka da 10 yocto y probe A long thin body containing a sensing element that can be inserted into a system in order to make measurements Typically the measurement is localized to the region near the tip of the probe proportional integral derivative PID A control function where output is related to the error signal in three ways Proportional gain acts on the instantaneous error as
202. kQ reading the error can probably be tolerated When measuring voltage for diode sensors the error in voltage can be calculated as the lead resistance times the current typically 10 pA For example a 10 Q lead resistance times 10 uA results in a 0 1 mV error in voltage Given the sensitivity of a silicon diode at 4 2 K the error Two Lead in temperature would be only 3 mK At 77 K the sensitivity of a silicon diode is Diode lower so the error would be close to 50 mK Again this may not be a problem for every user V Installation 3 5 Lake Shore Model 325 Temperature Controller User s Manual 3 4 7 Lowering Measurement Noise Good instrument hardware setup technique is one of the least expensive ways to reduce measurement noise The suggestions fall into two categories 1 Do not let noise from the outside enter into the measurement and 2 Let the instrument isolation and other hardware features work to their best advantage Here are some further suggestions e Use 4 lead measurement whenever possible e Do not connect sensor leads to chassis or earth ground e Use twisted shielded cable outside the cooling system e Attach the shield pin on the sensor connector to the cable shield Do not attach more than 1 cable shield at the other end of the cable e Run different inputs and outputs in their own shielded cable e Use twisted wire inside the cooling system e Use similar technique for heater leads e Use a grounded re
203. l RS 232C I O DTE Line input assembly O Loop 2 Heater output Sensor input connectors IEEE 488 interface Figure 1 2 Model 325 Rear Panel Connections 1 2 Introduction Lake Shore Model 325 Temperature Controller User s Manual Contigurable Display The Model 325 offers a bright easy to read LCD display that simultaneously displays up to four readings Display data includes input and source annunciators for each reading All four display locations can be configured by the user Data from either input can be assigned to any of the four locations and the user s choice of temperature or sensor units can be displayed Heater range and control output as current or power can be continuously displayed for immediate feedback on control operation The channel A or B indicator is underlined to indicate which channel is being controlled by the displayed control loop Normal Default Display Configuration The display provides four reading locations Readings from each input and the control setpoint can be expressed in any combination of temperature or sensor units with heater output expressed as a percent of full scale current or power Flexible Configuration Reading locations can be configured by the user to meet application needs The character preceding the reading indicates input A or B or setpoint S The character following the reading indicates measurement units Curve Entry The Model 325 display off
204. l 325 from the front panel Remote refers to operating the controller via the IEEE 488 Interface The keypad is disabled during remote operation The mode of operation can be changed by pressing the Remote Local key When in remote mode an R will be displayed in the rightmost character on the top line of the LCD display When in local mode the character will be blank 4 17 INTERFACE The Interface key serves two functions set the serial interface baud rate and set the IEEE 488 interface address and terminators To set the serial interface baud rate press the Interface key Use the A or V key to cycle through the choices of 9600 19200 38400 57600 baud The default baud rate is 9600 Press the Enter key to accept the changes or the Escape key to keep the existing setting and return to the normal display Operation 4 25 Lake Shore Model 325 Temperature Controller User s Manual Interface Continued To set the IEEE 488 interface address and terminators press the Interface key then press the Enter key until you see the following screen Use the or V key to increment or decrement the IEEE address to the desired number The default address is 12 Press the Enter key to accept the changes or the Escape key to keep the existing setting and return to the normal display Press the Enter key again to see the following screen Use the A or V key to cycle through the following
205. l System of Units silicon diode Temperature sensor based on the forward voltage drop at constant current through a pn semiconductor junction formed in crystalline silicon SoftCal n Lake Shore instruments SoftCalTM is used to improve the accuracy of a DT 400 Series silicon diode temperature sensor This reduces the error between the sensor and the standard Curve 10 used by the instrument to convert input voltage from the diode to a corresponding temperature stability The ability of an instrument or sensor to maintain a constant output given a constant input strain relief A predetermined amount of slack to relieve tension in component or lead wires Also called stress relief superconducting magnet An electromagnet whose coils are made of a type II superconductor with a high transition temperature and extremely high critical field such as niobium tin Nb3Sn it is capable of generating magnetic fields of 100 000 oersteds and more with no steady power dissipation See electromagnet susceptance In electrical terms susceptance is defined as the reciprocal of reactance and the imaginary part of the complex representation of admittance suscept ibility conduct ance susceptibility x Parameter giving an indication of the response of a material to an applied magnetic field The susceptibility is the ratio of the magnetization M to the applied field H y In both SI units and cgs units the volume susceptibility is dime
206. le register and the query command ESE reads it ESR reads and clears the Standard Event Status Register The used bits of the Standard Event Register are described as follows Power On PON Bit 7 This bit is set to indicate an instrument off on transition Command Error CME Bit 5 This bit is set if a command error has been detected since the last reading This means that the instrument could not interpret the command due to a syntax error an unrecognized header unrecognized terminators or an unsupported command Execution Error EXE Bit 4 This bit is set if an execution error has been detected This occurs when the instrument is instructed to do something not within its capabilities Query Error QYE Bit 2 This bit indicated a query error It occurs rarely and involves loss of data because the output queue is full Operation Complete OPC Bit 0 When OPC is sent this bit will be set when the instrument has completed all pending operations The operation of this bit is not related to the OPC command which is a separate interface feature Refer to Section 6 1 4 3 6 for more information SENS Bal HEIC EC ERE EE Status Register 128 64 32 16 8 4 2 1 Decima ESR ron J ove pe ve es Name ESR reads and clears the register To Event Summary standard Eve 7 6 5 4 3 T 2 T3 0 e bna Status Enable 5g 64 32 16 8 4 2 1 Decima R
207. leads are used to measure a sensor This method reduces the effect of lead resistance on the measurement GaAlAs Gallium aluminum arsenide semiconducting material used to make the special Lake Shore TG family of diode temperature sensors gamma A cgs unit of low level flux density where 100 000 gamma equals one oersted or 1 gamma equals 10 oersted A 2 Glossary of Terminology Lake Shore Model 325 Temperature Controller User s Manual gauss G The cgs unit for magnetic flux density B 1 gauss 10 tesla Named for Karl Fredrich Gauss 1777 1855 a German mathematician astronomer and physicist gaussian system units A system in which centimeter gram second units are used for electric and magnetic qualities general purpose interface bus GPIB Another term for the IEEE 488 bus germanium Ge A common temperature sensing material fabricated from doped germanium to make the Lake Shore GR family of resistance temperature sensor elements gilbert Gb A cgs electromagnetic unit of the magnetomotive force required to produce one maxwell of magnetic flux in a magnetic circuit of unit reluctance One gilbert is equal to 10 47 ampere turn Named for William Gilbert 1540 1603 an English physicist hypothesized that the earth is a magnet gilbert per centimeter Practical cgs unit of magnet intensity Gilberts per cm are the same as oersteds ground A conducting connection whether intentional or accidental by which an electric
208. libration setting value 4 4 5 Temperature Limit Firmware Version 1 5 and Later The temperature limit feature provides a means of protecting your equipment from damage by shutting down all control outputs when the assigned temperature limit is exceeded on any sensor input The feature is available for both of the sensor inputs A temperature limit of 0 K default value turns this feature off This feature was added in firmware version 1 5 If you need a firmware update contact service section 8 1 Section 4 18 provides the procedure to check your firmware version To configure a temperature limit press the Input Setup key The first screen appears as follows Use the A or V key to toggle between Input A and B Press the Enter key until the following display appears The temperature limit is entered using the numeric keypad which includes the numbers 0 9 The user can set temperature limit in kelvin with a range of 0 to 2999 and a resolution of 1 The feature is turned off when a temperature limit of 0 K is entered Press the Enter key to save the value 4 5 CURVE SELECTION The Model 325 supports a variety of temperature sensors sold by Lake Shore and other manufacturers After the appropriate sensor type is selected for each of the two inputs Section 4 4 an appropriate curve may be selected for each input The 325 can use curves from several sources Standard curves are included with every instrument and numbe
209. librations for applications above 30 K are performed at liquid nitrogen 77 35 K and room temperature 305 K Accuracy for the DT 470 SD 13 diode sensor is as follows 1 0K 2K to lt 30 no change below 30 40 25K 30K to lt 60K 0 15 60K to lt 345 0 25 345 to lt 375K 10 375 0 475 Three point SoftCal calibrations are performed at helium 4 2 liquid nitrogen 77 35 and room temperature 305 K Accuracy for the DT 470 SD 13 diode sensor is as follows 0 5 2K to lt 30 40 25K 30K to lt 60 K 0 25 345 lt 375 40 15K 60K to lt 345 FLOR lt gt Mond Advanced Operation 5 7 Lake Shore Model 325 Temperature Controller User s Manual 5 3 3 SoftCal with Platinum Sensors The platinum sensor is a well accepted temperature standard because of its consistent and repeatable temperature response above 30 K SoftCal gives platinum sensors better accuracy than their nominal matching to the DIN 43760 curve SoftCal Point 1 SoftCal Point 2 SoftCal Point 3 Liquid Nitrogen Room Temperature High Temperature Boiling Point Point Point 77 35 305 480 a 0 50 100 150 200 250 300 350 400 450 500 550 600 650 50 100 K 200 325K 400 600 K Acceptable Temperature Range for Platinum SoftCal Inputs C 325 5 2 bmp Figure 5 2 SoftCal Temperature Ranges for Platinum Sensors One two or three cal
210. line voltage selector and fuse Slide out the removable plastic fuse holder from the drawer Rotate the fuse holder until the proper voltage indicator shows through the window Verify the proper fuse value Re assemble the line input assembly in the reverse order 9 90 Sy Verify the voltage indicator in the window of the line input assembly Connect the instrument power Turn the line power switch On 1 Line Cord Power Switch Screwdriver Fuse Input O Off On Slot Drawer N 100 120 220 240 V 10 6 Voltage 100 120 1 6 250 5 20 50 60 Hz 85 220 240 1 6 250 5 20 F 325 8 2 wmf Figure 8 2 Power Fuse Access 8 2 Service Lake Shore Model 325 Temperature Controller User s Manual 8 5 FUSE REPLACEMENT Use the following procedure to remove and replace a line fuse WARNING avoid potentially lethal shocks turn off controller and disconnect it from AC power before performing these procedures CAUTION For continued protection against fire hazard replace only with the same fuse type and rating specified for the line for the line voltage selected NOTE Test fuse with an ohmmeter Do not rely on visual inspection of fuse Locate line input assembly on the instrument rear panel See Figure 8 2 Turn power switch Off O Remove instrument power cord With a small screwdriver release the
211. ll scale programming voltage of the auxiliary supply For example if the auxiliary supply has a full scale programming voltage of 10 V and the maximum current for the highest heater output range being used is 0 3 A the programming resistor should be 10 V 0 3 A 33 O The programming resistor must be rated for the power being dissipated in it which is 2 Power output x Fiprogram or 3 W The Low heater output range can be selected to reduce the power dissipated in the programming resistor 37 INITIAL SETUP AND SYSTEM CHECKOUT PROCEDURE The following is an initial instrument setup and checkout procedure The intent is to verify basic operation of the unit before beginning use for measurements The procedure assumes a setup with two Lake Shore DT 470 Silicon diode Sensors one control loop a single 50 heater all readings in kelvin and running in a liquid nitrogen environment CAUTION Check power source for proper voltage before connecting the line cord to the Model 325 Also check the line voltage setting on the window in the fuse drawer Damage to unit may occur if connected to improper voltage 1 Check power source for proper voltage The Model 325 operates with 100 120 220 or 240 6 10 AC input voltage 2 Check window in fuse drawer for proper voltage setting If incorrect refer to Section 8 4 3 Ensure the power switch is in the off O position CAUTION The sensor must be connected to the rear of the unit b
212. lly approach it in small steps Keep an eye on temperature sensitivity Sensitivity not only affects control stability but it also contributes to the overall control system gain The large changes in sensitivity that make some sensors so useful may make it necessary to retune the control loop more often 2 6 PID CONTROL For closed loop operation the Model 325 temperature controller uses a algorithm called PID control The control equation for the PID algorithm has three variable terms proportional P integral T and derivative D See Figure 2 3 Changing these variables for best control of a system 1s called tuning The PID equation in the Model 325 is where the error e is defined as e Setpoint Feedback Reading Proportional is discussed in Section 2 6 1 Integral is discussed in Section 2 6 2 Derivative 1s discussed in Section 2 6 3 Finally the manual heater output is discussed in Section 2 6 4 2 6 1 Proportional P The Proportional term also called gain must have a value greater than zero for the control loop to operate The value of the proportional term 18 multiplied by the error e which is defined as the difference between the setpoint and feedback temperatures to generate the proportional contribution to the output Output P Pe If proportional is acting alone with no integral there must always be an error or the output will go to zero A great deal must be known about the load sensor and controller to c
213. loy like phosphor bronze is much better than copper wire Thin wire insulation is preferred and twisted wire should be used to reduce the effect of RF noise if it is present The wire used on the room temperature side of the vacuum boundary is not critical so copper cable is normally used To Room Temperature Vacuum Shroud Refrigerator Expander Vacuum Space Radiation Shield Dental Floss Tie Down Thermal Anchor 0 Bobbin Cryogenic Tape Refrigerator Second Stage Thermal Anchor Cryogenic Wire Bobbin small diameter large AWG Cold Stage and Sensor Sample Holder Drawi Heater Not To Scale uring not shown Optical Window If Required P 325 2 2 bmp Figure 2 2 Typical Sensor Installation In A Mechanical Refrigerator Cooling System Design 2 5 Lake Shore Model 325 Temperature Controller User s Manual 2 3 7 Lead Soldering When additional wire is soldered to short sensor leads care must be taken not to overheat the sensor A heat sink such as a metal wire clamp or alligator clip will heat sink the leads and protect the sensor Leads should be tinned before bonding to reduce the time that heat is applied to the sensor lead Solder flux should be cleaned after soldering to prevent corrosion 2 8 8 Heat Sinking Leads Sensor leads can be a significant source of error if they are not properly heat sinked Heat will transfer down even small leads and alter the sensor reading The goal of h
214. ly one of the interfaces can be used at a time 6 1 IEEE 488 INTERFACE The IEEE 488 interface is an instrumentation bus with hardware and programming standards that simplify instrument interfacing The Model 325 IEEE 488 interface complies with the IEEE 488 2 1987 standard and incorporates its functional electrical and mechanical specifications unless otherwise specified in this manual instruments on the interface bus perform one or more of the interface functions of TALKER LISTENER or BUS CONTROLLER A TALKER transmits data onto the bus to other devices A LISTENER receives data from other devices through the bus The BUS CONTROLLER designates to the devices on the bus which function to perform The Model 325 performs the functions of TALKER and LISTENER but cannot be a BUS CONTROLLER The BUS CONTROLLER is the digital computer that tells the Model 325 which functions to perform Below are Model 325 IEEE 488 interface capabilities e SH1 Source handshake capability e RL1 Complete remote local capability e DC1 Full device clear capability e DTO No device trigger capability e CO No system controller capability T5 Basic TALKER serial poll capability talk only unaddressed to talk 1f addressed to listen 14 Basic LISTENER unaddressed to listen if addressed to talk e 581 Service request capability AH1 Acceptor handshake capability e PPO No parallel poll capability e Et Open collector electronics Instrument
215. m room temperature compensation Thermometry Number of inputs Input configuration Isolation A D resolution Input accuracy Measurement resolution Max update rate User curves SoftCal Filter 2 Each input is factory configured for either diode RTD or thermocouple Sensor inputs optically isolated from other circuits but not each other 24 bit Sensor dependent refer to Input Specifications table Sensor dependent refer to Input Specifications table 10 rdg s on each input except 5 rdg s on input A when configured as thermocouple Room for 15 200 point CalCurves or user curves Improves accuracy of DT 470 diode to 4 of platinum RTDs to 4 Averages 2 to 64 input readings Sensor Input Configuration 0 25 K from 30 to 375 Improves accuracy 0 25 from 70 to 325 Stored as user curves Diode RTD Thermocouple Measurement type 4 lead differential 2 lead room temperature compensated Excitation Constant current with current reversal for RTDs NA Supported sensors Diodes Silicon GaAlAs RTDs 100 Platinum 1000 Platinum Germanium Carbon Glass Cernox and Rox Most thermocouple types Standard curves DT 470 DT 500D DT 670 PT 100 PT 1000 RX 102A RX 202A Type E Type K Type T AuFe 0 07 vs Cr AuFe 0 03 vs Cr Input connector 6 pin DIN Ceramic isothermal block 1 6 Introduction Specificatio
216. me inconvenience loss of use of the product or property damage caused by this product or its failure to work or any other incidental or consequential damages Use of our product implies that you understand the Lake Shore license agreement and statement of limited warranty FIRMWARE LICENSE AGREEMENT The firmware in this instrument is protected by United States copyright law and international treaty provisions To maintain the warranty the code contained in the firmware must not be modified Any changes made to the code is at the user s risk Lake Shore will assume no responsibility for damage or errors incurred as result of any changes made to the firmware Under the terms of this agreement you may only use the Model 325 firmware as physically installed in the instrument Archival copies are strictly forbidden You may not decompile disassemble or reverse engineer the firmware If you suspect there are problems with the firmware return the instrument to Lake Shore for repair under the terms of the Limited Warranty specified above Any unauthorized duplication or use of the Model 325 firmware in whole or in part in print or in any other storage and retrieval system is forbidden TRADEMARK ACKNOWLEDGMENT Many manufacturers and sellers claim designations used to distinguish their products as trademarks Where those designations appear in this manual and Lake Shore was aware of a trademark claim they appear with initial capital letters
217. mple we will select V K Press the Enter key Use the numerical keypad to enter a setpoint limit in kelvin appropriate for the sensor being used For this example we will enter 475 00K Press the Enter key The temperature coefficient positive or negative of the curve is displayed The coefficient 15 calculated from the first two points of the curve and cannot be changed Press the Enter key Now that the curve identification parameters are entered it is time to enter curve breakpoints The cursor initially blinks on the curve breakpoint number When the cursor is in this position use the A or V key to scroll through the breakpoints in the curve Press the Enter key to modify the current breakpoint Use the numerical keypad to enter the applicable sensor value For this example we will enter 0 09062V then press the Enter key The cursor will jump to the temperature reading Again use numerical keypad to enter the applicable temperature in kelvin For this example we will enter 475 0K Press the Enter key Use the numerical keypad to enter the remaining voltage and temperature points After entering the final point in the curve press the Enter key then the Escape key You will return to the normal display To add a new breakpoint to an existing curve go to the end of the curve data and enter the new sensor reading and temperature Press the Enter key then the Escape key The ne
218. n 4 8 3 Manual Heater Allows adjustment of the Manual Heater Power setting Refer to Section 4 8 4 Input Setup Allows selection of sensor input type and curve Refer to Section 4 4 for sensor input setup and Section 4 5 for curve selection Curve Entry Allows entry of up to fifteen 200 point CalCurves or user curves and SoftCal Refer to Chapter 5 Advanced Operation Section 5 2 Front Panel Curve Entry Operations Display Format Allows the user to configure the display and select the units or other source of the readings Refer to Sections 4 1 4 and 4 3 Remote Local Sets remote or local operation Remote refers to operation is via IEEE 488 Interface Local refers to operation via the front panel Refer to Section 4 16 Interface Sets the baud rate of the serial interface and IEEE 488 address and terminators Refer to Section 4 17 A Serves two functions chooses between parameters during setting operations and to increment a numerical parameter value v Serves two functions chooses between parameters during setting operations and decrements numerical parameter value Escape Terminates a setting function without changing the existing parameter value Press and hold to reset instrument to default values Refer to Section 4 18 Enter Completes setting functions and returns to normal operation Press and hold to lock or unlock keypad Refer to Section 4 15 0 9 Used for entry of numeric data Includes a key to toggle plus
219. n logarithm of this ratio bifilar windings A winding consisting of two insulated wires side by side with currents traveling through them in opposite directions boiling point The temperature at which a substance in the liquid phase transforms to the gaseous phase commonly refers to the boiling point at sea level and standard atmospheric pressure CalCurve service The service of storing a mathematical representation of a calibration curve on an EEPROM or installed in a Lake Shore instrument Previously called Precision Option calibrate To determine by measurement or comparison with a standard the correct value of each scale reading on a meter or other device or the correct value for each setting of a control knob cathode The terminal from which forward current flows to the external circuit Anode gt Cathode Carbon Glass A temperature sensing material fabricated from a carbon impregnated glass matrix used to make the Lake Shore CGR family of sensors Celsius C Scale A temperature scale that registers the freezing point of water as 0 C and the boiling point as 100 C under normal atmospheric pressure Celsius degrees are purely derived units calculated from the Kelvin Thermodynamic Scale Formerly known as centigrade See Temperature for conversions Cernox A Lake Shore resistance temperature detector based on a ceramic oxy nitride resistance material C GR Carbon glass resistor
220. nfigured at the factory for customer selected power as follows VAC 100 Instrument configured for 100 VAC with U S power cord VAC 120 Instrument configured for 120 VAC with U S power cord VAC 220 Instrument configured for 220 VAC with universal European line cord VAC 240 Instrument configured for 240 VAC with universal European line cord VAC 120 ALL Instrument configured for 120 VAC with U S power cord and universal European line cord and fuses for 220 240 VAC setting 7 2 OPTIONS The list of Model 325 options 1s provided as follows Description of Options CalCurve on CD or E Mail The Model 8000 CalCurve is offered on CD or via e mail free of charge at time of order to any customer who orders a calibrated sensor The Model 8000 consists of calibration breakpoint interpolation data stored in ASCII format Also included is a PC executable program to load the data into a Lake Shore Instrument via IEEE 488 or RS 232 interface Once loaded the instrument uses the data to calculate and display temperature The following information is included raw data coefficients interpolation table instrument breakpoints LSCurves exe DOS based program and Readme txt describing the file formats CalCurve Factory Installed Provides users with a convenient method of storing sensor 8001 325 calibrations within Lake Shore Instruments Calibration data breakpoint interpolation table for a specific sensor is stored into
221. ng the relevant choices Press the Enter key Proceed to Section 4 4 4 1 to select a room temperature compensation or press the Escape key to return to the normal display 4 8 Operation Lake Shore Model 325 Temperature Controller User s Manual 4 4 4 1 Room Temperature Compensation Room temperature compensation is required to give accurate temperature measurements with thermocouple sensors It corrects for the temperature difference between the instrument thermal block and the curve normalization temperature of 0 C An external ice bath is the most accurate form of compensation but is often inconvenient The Model 325 has built in room temperature compensation that is adequate for most applications The built in compensation can be turned on or off by the user It operates with any thermocouple type that has an appropriate temperature response curve loaded Room temperature compensation is not meaningful for sensor units measurements NOTE temperature compensation should be calibrated as part of every installation To turn room temperature compensation on or off press the Input Setup and press Enter until the following display appears Use the or key to turn room temperature compensation on or off then press the Enter key The default setting is On If curve is set to None the room temperature compensation selection is automatically turned off 4 4 4 2 Room Temperature Calibration Procedure Room temp
222. nge for systems with less cooling power Control loop 2 heater output is a single range variable DC voltage source The output can source up to 0 2 A providing 2 W of heater power at the 50 Q setting or 1 W at the 25 Q setting When not being used for temperature control the loop 2 heater output can be used as a manually controlled voltage source The output voltage can vary from 0 to 10 V on the 50 O setting or 0 to 5 V on the 25 Q setting Both heater outputs are referenced to chassis ground The setpoint ramp feature allows smooth continuous setpoint changes and can also make the approach to setpoint more predictable The zone feature can automatically change control parameter values for operation over a large temperature range Ten different temperature zones can be loaded into the instrument which will select the next appropriate value on setpoint change nterface The Model 325 includes both parallel IEEE 488 and serial RS 232C computer interfaces In addition to data gathering nearly every function of the instrument can be controlled via computer interface Sensor curves can also be entered and manipulated through either interface using the Lake Shore curve handler software program o CHEATER our RS 232 DTE WARNIN d sm NO USER SUNG amp LakeS ore PARTS INSIDE REFER SERVICING TO TRAINED SERVICE PERSONNEL INPUTA INPUTB HEATER no Loop 1 Heater output Seria
223. nn Refer to Section 6 1 4 2 for a list of status flags Status Byte Query STB term lt bit weighting gt term nnn Acts like a serial poll but does not reset the register to all zeros The integer returned represents the sum of the bit weighting of the status flag bits that are set in the Status Byte Register Refer to Section 6 1 4 2 for a list of status flags 6 24 Remote Operation TST Input Returned Format Remarks WAI Input Remarks CMODE Input Format Example CMODE Input Format Returned Format CRDG Input Format Returned Format Remarks CRVDEL Input Format Example Lake Shore Model 325 Temperature Controller User s Manual Self Test Query TST term lt status gt term n lt status gt 0 no errors found 1 errors found The Model 325 reports status based on test done at power up Wait to Continue Command KWAI term This command is not supported in the Model 325 Control Loop Mode Command CMODE lt loop gt lt mode gt term nan loop Specifies which loop to configure 1 or 2 mode Specifies the control mode Valid entries 1 Manual PID 2 Zone 3 Open Loop 4 AutoTune PID 5 AutoTune PI 6 AutoTune P CMODE 1 4 term Control Loop 1 uses PID AutoTuning Control Loop Mode Query CMODE lt loop gt term n loop Specifies which loop to query 1 or 2 lt mode gt term n Refer
224. noise if one of the thermocouples is grounded Grounding both thermocouples is not recommended The instrument does not offer a shield connection on the terminal block Twisting the thermocouple wires helps reject noise If shielding 18 necessary extend the shield from the oven or cryostat to cover the thermocouple wire but do not attach the shield to the instrument 3 6 HEATER OUTPUT SETUP The following section covers the heater wiring from the vacuum shroud to the instrument for both control loop outputs Specifications are detailed in Section 1 2 For help on choosing and installing an appropriate resistive heater refer to Section 2 4 3 6 4 Loop 1 Output Of the two Model 325 control loops Loop 1 1s considered the primary loop because it is capable of driving 25 W of heater power The heater output for Loop 1 is a traditional control output for a cryogenic temperature controller It is a variable DC current source with software settable ranges and limits The heater is configurable for optimization using either a 25 or a 50 heater resistance At the 25 setting the maximum heater output current is 1 A and the compliance voltage is 25 V At the 50 O setting the maximum heater output current is 0 71 A and the compliance voltage is 35 4 V Heater power is applied in one of two ranges Low or High At the Low range setting the Loop 1 heater will output 1096 of the High range power 3 6 2 Loop 1 Heater Output Connector LOOP 1 A dual b
225. ns Continued Control Control loops 2 Control type Tuning Control stability PID control settings Proportional Gain Integral Reset Derivative Rate Manual output Zone control Setpoint ramping Loop 1 Heater Output Lake Shore Model 325 Temperature Controller User s Manual Closed loop digital PID with manual heater output or open loop Autotune one loop at a time PID PID zones Sensor dependent refer to Input Specifications table 0 to 1000 with 0 1 setting resolution 1 to 1000 1000 s with 0 1 setting resolution 1 to 200 with 1 resolution 0 to 100 with 0 01 setting resolution 10 temperature zones with P I D manual heater out and heater range 0 1 K min to 100 K min Type Variable DC current source D A resolution 16 bit 25 Q Setting 50 Q Setting Max power 25 W 25 W Max current 1A 071 Voltage compliance min 25V 35 4V Heater load range 200 to 25 0 400 to 50 QO Heater load for max power 250 500 Ranges 2 2 5 W 25 W Heater noise lt 1 kHz 1 pA 0 01 of output Grounding Output referenced to chassis ground Heater connector Dual banana Safety limits Curve temperature power up heater off short circuit protection Loop 2 Heater Output Type Variable DC voltage source D A resolution 16 bit 25 Q Setting 50 Setting Max power 1W 2W Max voltage 5 10 Current compliance min 0 2A 0 2A Heater load r
226. nsionless parameter Multiply the cgs susceptibility by 47 to yield the SI susceptibility See also Initial Susceptibility and Differential Susceptibility As in the case of magnetization the susceptibility is often seen expressed as a mass susceptibility or a molar susceptibility depending upon how M is expressed temperature coefficient measurement The measurement accuracy of an instrument is affected by changes in ambient temperature The error is specified as an amount of change usually in percent for every one degree change in ambient temperature tesla T The SI unit for magnetic flux density B 1 tesla 10 gauss thermal emf An electromotive force arising from a difference in temperature at two points along a circuit as in the Seebeck effect thermocouple A pair of dissimilar conductors so joined at two points that an electromotive force is developed by the thermoelectric effects when the junctions are at different temperatures tolerance The range between allowable maximum and minimum values torr Unit of pressure 1 torr 1 mm of mercury 1 atmosphere 760 torr two lead Measurement technique where one pair of leads is used for both excitation and measurement of a sensor This method will not reduce the effect of lead resistance on the measurement unit magnetic pole A pole with a strength such that when it is placed 1 cm away from a like pole the force between the two is 1 dyne volt V The difference of electric
227. nsor Lead Cable The sensor lead cable used outside the cooling system can be much different from what is used inside Between the instrument and vacuum shroud error and noise pick up not heat leak need to be minimized Larger conductor 22 to 28 AWG stranded copper wire is recommended because it has low resistance yet remains flexible when several wires are bundled in a cable The arrangement of wires in a cable is also important For best results voltage leads V and should be twisted together and current leads I and should be twisted together The twisted pairs of voltage and current leads should then be covered with a braided or foil shield that is connected to the shield pin of the instrument This type of cable is available through local electronics suppliers Instrument specifications are given assuming 10 feet of sensor cable Longer cables 100 feet or more can be used but environmental conditions may degrade accuracy and noise specifications Refer to Section 2 3 6 for information about wiring inside the cryostat 3 4 Installation Lake Shore Model 325 Temperature Controller User s Manual 3 4 3 Grounding and Shielding Sensor Leads The sensor inputs are isolated from earth ground to reduce the amount of earth ground referenced noise that is present on the measurement leads Connecting sensor leads to earth ground on the chassis of the instrument or in the cooling system will defeat that isolation Grounding leads on more th
228. nt with Data Communications Equipment DCE wiring can be connected to the instrument with a straight through cable As an example Pin 3 of the DTE connector holds the transmit line and Pin 3 of the DCE connector holds the receive line so the functions complement Itis likely both pieces of equipment are wired in the DTE configuration In this case Pin 3 on one DTE connector used for transmit must be wired to Pin 2 on the other used for receive Cables that swap the complementing lines are called null modem cables and must be used between two DTE wired devices Null modem adapters are also available for use with straight through cables Section 8 7 1 illustrates suggested cables that can be used between the instrument and common computers The instrument uses drivers to generate the transmission voltage levels required by the RS 232C standard These voltages are considered safe under normal operating conditions because of their relatively low voltage and current limits The drivers are designed to work with cables up to 50 feet in length 6 2 2 Hardware Support The Model 325 interface hardware supports the following features Asynchronous timing 1s used for the individual bit data within a character This timing requires start and stop bits as part of each character so the transmitter and receiver can resynchronize between each character Half duplex transmission allows the Table 6 6 Serial Interface Specifications instrument to be eithe
229. nter tenen neenon aderant 7 5 Model RM 2 Dual Rack Mount 7 6 IP e 8 2 Power Fuse ACCess inen eeeinen iei 8 2 Sensor INPUT A and B Connector Details 8 4 HEATER OUTPUT Connector Details oriente ipee e Ie E ie e tree eee ere 8 4 RELAYS and ANALOG OUTPUT Terminal 8 5 R 232 Connector Details tenente pine e E aa e ut Inge Rn Ee Euer Edo 8 5 IEEE 488 Rear Panel Connector 1 ende denken tns 8 7 Location of Internal Componerts 1 rettet 8 10 Temperature Scale Comparison et nnde nhe ntt Rente B 1 Typical Cryogenic Storage C 1 Table of Contents Lake Shore Model 325 Temperature Controller User s Manual LIST OF TABLES Table No Title Page 1 1 nS 1 4 1 2 2 1 5 4 1 sens
230. ocouple 8 16 B 1 Temperat re Conversion Table current emet ue da RE pre EV B 2 C 1 Comparison of Liquid Helium and Liquid emen C 1 D 1 DT 470 Silicon Diode Curve Curve 10 D 1 D 2 DT 670 Silicon Diode Curve Ee as die ee s D 2 D 3 DT 500 Series Silicon Diode D 2 D 4 PT 100 1000 Platinum RTD D 3 D 5 RX 102A ROX ioo E Ee AG bene ren OSEE code E een dme ded D 4 D 6 RX 202A ROX M CUNE quem D 5 D 7 Type K Thermocouple etit eee D 6 D 8 E Thermocouple Curve a a r E ae a aaae a Ar a a a a ae a Aana EAs AE A Eoo NEEE iraia eaP iS D 7 D 9 Type T Th rmocouple Curve fcc canes ree a e etic ees D 8 D 10 Chromel AuFe 0 03 Thermocouple D 9 D 11 Chromel AuFe 0 07 Thermocouple D 10 vi Table of Contents Lake Shore Model 325 Temperature Controller User s Manual CHAPTER 1 INTRODUCTION 1 0 PRODUCT DESCRIPTION The Model 325 dual channel temperature controller is capable of supporting nearly any diode RTD or thermocouple temperature sensor Two independent PID control loops with heater outputs of 25 W and 2 W are configured to drive either a 50 Q or 25
231. ode sensors include the Silicon and Gallium Aluminum Arsenide GaAlAs detailed in Table 4 1 More detailed specifications are provided in Section 1 2 Input ranges are fixed to 0 2 5 V for silicon diodes and 0 7 5 V for GaAlAs diodes Both use a sensor excitation current of 10 pA To setup a diode sensor input press the Input Setup key The first screen appears as follows Use the or V key to toggle between Input A and B Press the Enter key Use the A or V key to cycle through the sensor types shown in Table 4 1 with Silicon Diode and GaAlAs Diode being the relevant choices Press the Enter key Proceed to Section 4 5 1 to select a temperature curve or press the Escape key to return to the normal display 4 4 Diode Sensor Input Setup 1 mA Excitation Current As an alternative to the standard diode input configuration listed in Section 4 4 1 the user may select 1 mA excitation while the input configuration matches the diode input setup as detailed in Table 4 1 Input ranges are fixed to 0 2 5 V and 0 7 5 V 4 6 Operation Lake Shore Model 325 Temperature Controller User s Manual Diode Sensor Input Setup 1 mA Excitation Current Continued To access the alternative setup the diode current must be set to 1 mA Press and hold the Input Setup key for 10 seconds to display the screen shown as follows Use the A or V key to toggle between 10 uA and 1 mA to select the d
232. oint 6 33 DISPFLD Displayed Field Cmd 6 27 SETP Control Loop Setpoint Query 6 33 DISPFLD Displayed Field Query 6 27 SRDG Sensor Units Reading Query 6 33 FILTER Input Filter Parameter Cmd 6 28 TEMP Room Temp Comp Temp Query 6 34 FILTER Input Filter Parameter Query 6 28 TLIMIT Temperature Limit Command 6 34 HTR Heater Output Query 6 28 TLIMIT Temperature Limit Query 6 34 HTRRES Heater Resistance Setting 6 28 TUNEST Control Loop 1 Tuning Query 6 34 HTRRES Heater Resistance Setting Query 6 28 ZONE Control Loop Zone Table 6 34 IEEE IEEE Interface Parameter Cmd 6 28 ZONE Control Loop Zone Table Query 6 35 6 22 Remote Operation 6 3 1 CLS Input Remarks Input Format Remarks Example Input Returned Format ESR Input Returned Format Remarks 10 Input Returned Format Example Lake Shore Model 325 Temperature Controller User s Manual Interface Commands Alphabetical Listing Clear Interface Command CLS term Clears the bits in the Status Byte Register and Standard Event Status Register and terminates all pending operations Clears the inter
233. omium vs Nickel Aluminum Chromel YEL Alumel RED Type E Nickel Chromium vs Copper Nickel Chromel PUR Constantan RED Type T Copper vs Copper Nickel Copper BLU Constantan RED Chromel AuFe 0 03 Chromel Gold Chromel AuFe 0 07 Chromel Gold Figure 3 4 Thermocouple Input Definition and Common Connector Polarities 3 6 Installation Lake Shore Model 325 Temperature Controller User s Manual 3 5 2 Thermocouple Installation Thermocouples are commonly used in high temperature applications Cryogenic use of thermocouples offers some unique challenges A general installation guideline is provided in Section 2 3 Consider the following when using thermocouples at low temperatures Thermocouple wire is generally more thermally conductive than other sensor lead wire Smaller gauge wire and more heat sinking may be needed to prevent leads from heating the sample e Attaching lead wires and passing through vacuum tight connectors are often necessary in cryogenic systems Remember the thermocouple wire the sensor any time it joins or contacts other metal there is potential for error Temperature verification and calibration of room temperature compensation is difficult after the sensor is installed When possible keep a piece of scrap wire from each installation for future use 3 5 3 Grounding and Shielding For lowest measurement noise do not ground thermocouple sensors The instrument operates with more
234. ompute a proportional setting P Most often the proportional setting 1s determined by trial and error The proportional setting is part of the overall control loop gain and so are the heater range and cooling power The proportional setting will need to change if either of these change 2 8 Cooling System Design Lake Shore Model 325 Temperature Controller User s Manual 2 6 2 Integral I In the control loop the integral term also called reset looks at error over time to build the integral contribution to the output By adding the integral to proportional contributions the error that is necessary in a proportional only system can be eliminated When the error is at zero controlling at the setpoint the output is held constant by the integral contribution The integral setting is more predictable than the gain setting It is related to the dominant time constant of the load As discussed in Section 2 7 3 measuring this time constant allows a reasonable calculation of the integral setting In the Model 325 the integral term is not set in seconds like some other systems The integral setting can be derived by dividing 1000 by the integral seconds setting 1000 Iseconas 2 6 3 Derivative D The derivative term also called rate acts on the change in error with time to make its contribution to the output By reacting to a fast changing error signal the derivative can work to boost the output when the setpoint changes quickl
235. one Model 325 to a 483 mm 19 in rack mount space See Figure 7 3 Dual Mounting Shelf for Two Model 325 Temperature Controllers Mounting shelf to attach any RM 2 two 5 25 in tall half rack instruments side by side on a 483 mm 19 in rack mount shelf See Figure 7 4 IMI 7031 Varnish formerly GE 7031 Varnish 1 pint can IMI 7031 Insulating Varnish and Adhesive possesses electrical and bonding properties which when combined with its chemical resistance and good saturating properties make it an excellent material for cryogenic temperatures VGE 7031 As an adhesive IMI 7031 bonds a variety of materials has fast tack time and may be air dried or baked It is also an electrically insulating adhesive at cryogenic temperatures and is often used as a calorimeter cement When soaked into cigarette paper it makes a good high thermal conductivity low electrical conductivity heat sinking layer Maximum operating temperature 423 K 150 C Lake Shore Cryogenic Wire Lake Shore sells the following types of cryogenic wire DT Duo Twist MN Single Strand MW Manganin NC Nichrome Heater Wire ND Heavy Duty QL Quad Lead and QT Quad Twist 50 Cartridge Heater The heater features precision wound nickel chromium resistance wire magnesium oxide insulation two solid pins non magnetic package and has UL and CSA component HTR 50 recognition The heater is 50 Q 6 35 mm 0 25 in diameter by 25 4 mm 1 in long The 50 r
236. or Input Types sine ee eee needa nd eerie 4 6 4 2 Sensor CUMVES wie i ashen teehee cvi P e nd pe E Ie Lee coe e at Reese edet E Pene awed 4 10 4 3 Comparison of Control Loops 1 2 4 13 4 4 Defatilt VAlUGS EDL 4 26 5 1 C rve Header Parameters ea cio Eri re Eee s RE la E 5 2 5 2 Recommended Curve Parameters eee Ea trn Enn pena de 5 2 6 1 Binary Weighting of an 8 Bit nennen enne nennen 6 5 6 2 Register Clear Methods 1 23 rio eie esie ee ruban Le ek e ae 6 5 6 3 Programming Example to Generate an 5 6 9 6 4 IEEE 488 Interface Program Control Properties 6 12 6 5 Visual Basic IEEE 488 Interface 6 13 6 6 Serial Interface Specifications 2 erne esinen t tenes Ere at eg ne Va ere sv ea EE Ere inge b 6 15 6 7 Serial Interface Program Control 6 18 6 8 Visual Basic Serial Interface 6 19 6 9 Command Sumrmary 2 ee a ei ger i Veto pec d ee eee E ees 6 22 8 1 Calibration Table for Diode 8 13 8 2 Calibration Table for Resistive 8 15 8 3 Calibration Table for Therm
237. oud larger gage copper cable can be used and twisting is still recommended 2 5 CONSIDERATION FOR GOOD CONTROL Most of the techniques discussed above to improve cryogenic temperature accuracy apply to control as well There is an obvious exception in sensor location A compromise is suggested below in Section 2 5 3 Two Sensor Approach 2 5 1 Thermal Conductivity Good thermal conductivity is important in any part of a cryogenic system that is intended to be at the same temperature Most systems begin with materials that have good conductivity themselves but as sensors heaters sample holders etc are added to an ever more crowded space the junctions between parts are often overlooked In order for control to work well junctions between the elements of the control loop must be in close thermal contact and have good thermal conductivity Gasket materials should always be used along with reasonable pressure 2 5 2 Thermal Lag Poor thermal conductivity causes thermal gradients that reduce accuracy and also cause thermal lag that make it difficult for controllers to do their job Thermal lag is the time it takes for a change in heating or cooling power to propagate through the load and get to the feedback sensor Because the feedback sensor is the only thing that lets the controller know what is happening in the system slow information to the sensor slows the response time For example if the temperature at the load drops slightly below the
238. ounting materials is very important in a cryogenic environment The high vacuum used to insulate cryostats is one source of problems Materials used in these applications should have a low vapor pressure so they do not evaporate or out gas and spoil the vacuum insulation Metals and ceramics do not have this problem but greases and varnishes must be checked Another source of problems is the wide extremes in temperature most sensors are exposed to The linear expansion coefficient of materials becomes important when temperature changes are so large Never try to permanently bond materials with linear expansion coefficients that differ by more than three A flexible mounting scheme should be used or the parts will break apart potentially damaging them The thermal expansion or contraction of rigid clamps or holders could crush fragile samples or sensors that do not have the same coefficient Thermal conductivity is a property of materials that can change with temperature Do not assume that a heat sink grease that works well at room temperature and above will do the same job at low temperatures 2 32 Sensor Location Finding a good place to mount a sensor in an already crowded cryostat is never easy There are fewer problems if the entire load and sample holder are at the same temperature Unfortunately this not the case in many systems Temperature gradients differences in temperature exist because there is seldom perfect balance between the cooling sourc
239. output as its actuator It is a variable DC voltage source with an output range from 0 V to 10 V The output can source up to 200 mA of current providing a maximum of 2 W with a 50 Q heater at the 50 setting The output voltage range is 0 V to 5 V when set to the 25 setting providing a maximum power of 1 W into a 25 heater 3 6 6 Loop 2 Output Resistance The power delivered by the Loop 2 output is calculated as P V Rheater The output is rated for no more than 200 mA of current and has a built in current limit For the maximum of 2 W output power use a 50 Q resistive heater with a power rating greater than 2 W A 25 Q heater can be used to provide 1 W of power The 25 Q setting for Loop 2 changes the output voltage range to allow for control over the entire range of output Using a 25 Q heater at the 50 Q setting would still provide 1 W of power but the maximum power will be reached at a setting of about 50 at which point the 200 mA current limit will begin to limit output power and could cause temperature control instability 3 6 7 Loop 2 Output Connector The connector for the Loop 2 output is a 2 pin detachable terminal block See Figure 8 5 Twisted pair of small gauge wire is recommended 3 6 8 Loop 2 Heater Protection The output is short protected so the instrument is not harmed if the heater resistance is too small It is not recommended because control over the full output voltage range is lost when in power limit mode Th
240. perature and superconductivity research and for its refrigeration properties such as in freezing tissue cultures minimum purity 99 998 O 8 ppm max Boiling point at 1 atm 77 4 K Latent heat of vaporization 160 kilojoules per liter Liquid density 0 81 kilograms per liter EPA Hazard Categories Immediate Acute Health and Sudden Release of Pressure Hazards DOT Name Nitrogen Refrigerated Liquid DOT Label Nonflammable Gas DOT Class Nonflammable Gas DOT ID No UN 1977 load regulation A steady state decrease of the value of the specified variable resulting from a specified increase in load generally from no load to full load unless otherwise specified M Symbol for magnetization See magnetization magnetic air gap The air space or non magnetic portion of a magnetic circuit magnetic field strength H The magnetizing force generated by currents and magnetic poles For most applications the magnetic field strength can be thought of as the applied field generated for example by a superconducting magnet The magnetic field strength is not a property of materials Measure in SI units of A m or cgs units of oersted magnetic flux density B Also referred to as magnetic induction This is the net magnetic response of a medium to an applied field H The relationship is given by the following equation B M for SI and B 42M for cgs where magnetic field strength M magnetization and permeability of free space
241. porary character space Terminators Counter used for Timing out Data string sent to instrument Show main window Terminators lt CR gt lt LF gt Initialize counter Clear return string Clear holding string Close serial port to change settings Example of Comm 1 Example of 9600 Baud Parity Data Stop Read one character at a time Open port Wait loop Give up processor to other events Loop until Send button pressed Set Flag as false Get Command Clear response display Set all characters to upper case Get out on EXIT Send command to instrument Check to see if query Wait for response Add 1 to timeout if no character Wait for 10 millisecond timer Loop Until frmSerial Timerl Enabled False ZeroCount ZeroCount 1 Else ZeroCount 0 strHold frmSerial MSComml Input strReturn strReturn strHold End If Wend If strReturn Then strReturn Mid strReturn 1 InStr strReturn Else strReturn No Response End If frmSerial txtResponse Text strReturn strHold ZeroCount 0 End If Loop End Sub Timeout at 2 seconds Reset timeout for each character Read in one character Add next character to string Get characters until terminators Check if string empty Term 1 Strip terminators Send No Response Put response in textbox on main form Reset holding string Reset timeout counter Private Sub Timerl Timer frmSerial Timerl Enabled
242. put setting is in percent of full scale Percent of full scale is defined as percent of full scale current or power on the selected heater range Manual heater power output setting range is 0 to 100 with a resolution of 0 001 To enter a MHP Output setting press the Manual Heater key The following display appears The MHP Output setting is entered using the numeric keypad which includes the numbers 0 9 and decimal point Press the Enter key then the Escape key to return to the normal display 4 9 AUTOTUNE Closed Loop PID Control The Model 325 automates the tuning process of typical cryogenic systems with the AutoTune feature For additional information about the algorithm refer to Section 2 8 Before initiating AutoTune the cooling system must be set up properly with control sensor and heater making it capable of closed loop control AutoTune works only with one control loop at a time and does not set the manual heater power output or heater range The control sensor must have a valid temperature response curve assigned to it An appropriate heater range must also be determined as described in Section 2 7 1 Choosing good initial control parameters by experimenting with Manual PID tuning can speed up the AutoTune process If no initial parameters are known start with the default values of P 50 and I 20 It is better to set an initial P value that causes the system to be more active than desired Starting with a low
243. query format is lt query mnemonic gt lt gt lt space gt lt parameter data gt lt terminators gt Query mnemonics are often the same as commands with the addition of a question mark Parameter data is often unnecessary when sending queries Query mnemonics and parameter data if necessary is described in Section 6 3 Terminators must be sent with every message string The computer should expect a response very soon after a query is sent A response string is the instruments response or answer to a query string The instrument will respond only to the last query it receives The response can be a reading value status report or the present value of a parameter Response data formats are listed along with the associated queries in Section 6 3 The response is sent as soon as possible after the instrument receives the query Typically it takes 10 ms for the instrument to begin the response Some responses take longer 6 2 5 Message Flow Control Itis important to remember that the user program is in charge of the serial communication at all times The instrument cannot initiate communication determine which device should be transmitting at a given time or guarantee timing between messages All of this is the responsibility of the user program When issuing commands only the user program should Properly format and transmit the command including terminators as one string Guarantee that no other communication is started for 50 ms after the las
244. r 9 Program the gain calibration by dividing the measured value of the reference voltage by the value read in the previous step and provide the result using the CALG command Note that the gain calibration constant will always be within 5 of 1 00000 EXAMPLE Input A Range Thermo 25mV Measured Value of Reference Voltage 25 0032 mV DC CALREAD Reading 24 9867 Constant Calculation 25 0032 24 9867 1 00066 Calibration Command CALG A 6 1 00066 10 Send the CALSAVE command to save the constants in the EEPROM 11 Perform calibration on both thermocouple ranges 12 Repeat for second input if thermocouple Table 8 3 Calibration Table for Thermocouple Ranges Range Voltage Reference Reference Voltage Cal Command Output Known to Type Number Thermo 25mV 25 mV DC 0 0070 mV DC 6 Thermo 50mV 50 mV DC 0 0130 mV DC 7 8 12 5 Loop 2 Heater Calibration Overview The Model 325 has a second control loop output which requires calibration Zero offset and gain errors are calibrated out by programming offset and gain constants to the instrument Calibration Process 8 12 5 1 Loop 2 Voltage Output Calibration Purpose To determine the Loop 2 output offset and gain errors and provide offset and gain calibration constants back to the Model 325 Process 1 Reset the calibration constants to their default values using the CALZ and CALG commands EXAMPLE Zero Offset Command CALZ V 1 0
245. r Off Refer to Section 4 6 1 Heater Range For Loop 1 allows selection of High 25 W or Low 2 5 W heater range For Loop 2 allows selection of Heater On Off Refer to Section 4 13 Heater Off Turns the heater off for Loop 1 or turns the control output off for Loop 2 Refer to Section 4 13 Control Setup Allows selection of control input setpoint units closed or open loop control mode power up enable display of heater output units setpoint ramp enable ramp rate for the currently selected loop and heater resistance Refer to Section 4 7 for control setup and Section 4 12 for ramp feature Setpoint Allows entry of control setpoint for the currently selected loop Refer to Section 4 11 A discussion of the ramp feature 1s provided in Section 4 12 Zone Settings Allows entry of up to 10 temperature control zones of customer entered PID settings and Heater Ranges for the currently selected loop Refer to Section 4 10 325 Front bmp Figure 4 1 Model 325 Front Panel Operation 4 1 Lake Shore Model 325 Temperature Controller User s Manual Keypad Definitions Continued P Allows manual adjustment of the Proportional control parameter for the currently selected loop Refer to Section 4 8 1 Allows manual adjustment of the Integral control parameter for the currently selected loop Refer to Section 4 8 2 D Allows manual adjustment of the Derivative control parameter for the currently selected loop Refer to Sectio
246. r User s Manual Filter Continued Use the A or V key to toggle between Filter On and Off If you select Off the routine will end and return you to the normal display If you select On the routine will continue with the following Use the A or V key to increment or decrement the Filter Points from 02 through 64 with 08 being the default Press the Enter key You will see the following display Use the A or V key to increment or decrement the Filter Window from 01 through 10 with 01 being the default Press the Enter key You will return to the normal display 4 6 TEMPERATURE CONTROL There are many steps involved in setting up a temperature control loop Chapter 2 of this manual describes the principals of closed loop feedback control Chapter 3 describes necessary hardware installation The following sections of this chapter describe how to operate the control features and set control parameters Each control parameter should be considered before enabling a control loop or the instrument may not be able to perform the most simple control functions A good starting point is deciding which control loop to use whether to operate in open or closed control mode and which tuning mode is best for the application Other parameters fall into place once these have been chosen 4 6 4 Control Loops The Model 325 is capable of running two simultaneous control loops Their capabilities are compared in Table 4 3 As
247. r a transmitter or a p receiver of data but not both at the same time Connector Type 9 pin D style connector plug Communication speeds of 9600 19200 Connector Wiring DTE 37000 pa vidare supported The baud Voltage Levels EIA RS 232C specified rate is the only interface parameter that can be d Transmission Distance 50 ft maximum changed by the user eee Timing Format Asynchronous Hardware handshaking is not supported by the Transmission Mode Half duplex instrument Handshaking is often used to Baud Rate 9600 19200 38400 57600 guarantee that data message strings do not Handshake Software timing collide and that no data is transmitted before Character Bits 1 start 7 data 1 parity 1 stop the receiver is ready In this instrument Parity Odd appropriate software timing substitutes for CR 0DH LF 0AH Dardwate handshaking User programe must Command Rate 20 commands per second maximum take full responsibility for flow control and timing as described in Section 6 2 5 Remote Operation 6 15 Lake Shore Model 325 Temperature Controller User s Manual 6 2 3 Character Format A character is the smallest piece of information that can be transmitted by the interface Each character is 10 bits long and contains data bits bits for character timing and an error detection bit The instrument uses 7 bits for data in the ASCII format One start bit and one stop bit are necessary to synch
248. r must be reduced to a table of breakpoints before entering it into the instrument Each breakpoint consists of one value in sensor units and one temperature value in kelvin Linear interpolation is used by the instrument to calculate temperature between breakpoints From 2 to 200 breakpoints can be entered as a curve The instrument will show an error message on the display if the sensor input is outside the range of the breakpoints No special endpoints are required Sensor units are defined by the format setting in Table 5 2 Breakpoint setting resolution is six digits in temperature Most temperature values are entered with 0 001 resolution Temperature values of 1000 K and greater can be entered to 0 01 resolution Temperature values below 10 K can be entered with 0 0001 resolution Temperature range for curve entry is 1500 K Advanced Operation 5 1 Lake Shore Model 325 Temperature Controller User s Manual Table 5 1 Curve Header Parameters The curve name cannot be changed from the front panel Curve names can only be entered over the Name computer interface up to 15 characters The default curve name is User xx where xx is the curve number Identify specific sensors with serial numbers of up to 10 characters The serial number field accepts Serial Num both numbers and letters but the instrument front panel enters only numbers To enter both numbers and lette
249. range of 0 to 100 and a resolution of 0 1 Once the ramp feature is turned on its action is initiated by a setpoint change When a new setpoint is entered the instrument changes the setpoint temperature from the old value to the new value at the ramp rate A positive ramp rate is always entered it is used by the instrument for up and down ramps in temperature The ramping feature is useful by itself but it is even more powerful when used with other features Setpoint ramps are often used with zone control mode As temperature is ramped through different temperature zones control parameters are automatically selected for best control Ramps can be initiated and status read back using a computer interface During computer controlled experiments the instrument generates the setpoint ramp while the computer is busy taking necessary data AutoTune does not function during a setpoint ramp The ramp rate disguises the reaction of the cooling system and no valid tuning data can be taken NOTE When an incomplete ramp is shut off the setpoint will remain on the most current setting i e the reading will not jump to the end of the ramp NOTE Ifthe input type or input curve is changed while a ramp is in progress both ramping and the heater are turned off NOTE IfRamp is on and the setpoint is set to sensor units the ramping function will remain on but when another setpoint is entered the setpoint goes directly to the new setpoint value To enable
250. re addressed commands that create commonalty between instruments on the bus All instruments that comply with the IEEE 488 1987 standard share these commands and their format Common commands all begin with an asterisk They generally relate to bus and instrument status and identification Common query commands end with a question mark Model 325 common commands are detailed in Section 6 3 and summarized in Table 6 9 6 1 3 3 Device Specific Commands Device specific commands are addressed commands The Model 325 supports a variety of device specific commands to program instruments remotely from a digital computer and to transfer measurements to the computer Most device specific commands perform functions also performed from the front panel Model 325 device specific commands are detailed in Section 6 3 and summarized in Table 6 9 6 1 3 4 Message Strings A message string is a group of characters assembled to perform an interface function There are three types of message strings commands queries and responses The computer issues command and query strings through user programs the instrument issues responses Two or more command strings or queries can be chained together in one communication but they must be separated by a semi colon The total communication string must not exceed 255 characters in length A command string is issued by the computer and instructs the instrument to perform a function or change a parameter setting
251. re ignored Commands and queries and should have a space separating the command and associated parameters Leading zeros and zeros following a decimal point are not needed in a command string but they will be sent in response to a query A leading is not required but a leading required 6 2 8 Troubleshooting New Installation 1 Check instrument baud rate 2 Make sure transmit TD signal line from the instrument is routed to receive RD on the computer and vice versa Use a null modem adapter if not 3 Always send terminators 4 Sendentire message string at one time including terminators Many terminal emulation programs do not 5 Sendonly one simple command at a time until communication is established 6 Besure to spell commands correctly and use proper syntax Old Installation No Longer Working 1 Power instrument off then on again to see if it is a soft failure 2 Power computer off then on again to see if communication port is locked up 3 Verify that baud rate has not been changed on the instrument during a memory reset 4 Check all cable connections Intermittent Lockups 1 Check cable connections and length 2 Increase delay between all commands to 100 ms to make sure instrument is not being overloaded 6 20 Remote Operation Lake Shore Model 325 Temperature Controller User s Manual 6 3 COMMAND SUMMARY This section provides a listing of the IEEE 488 and serial interface commands
252. red 1 20 User curves numbered 21 35 are loaded when a sensor does not match a standard curve CalCurve options are stored as user curves SoftCal calibrations are stored as user curves or user can enter their own curves from the front panel Section 5 2 or computer interface Chapter 6 The complete list of sensor curves built in to the Model 325 is provided in Table 4 2 During normal operation only the curves related to the input type you have selected are displayed If the curve you wish to select does not appear in the selection sequence make sure the curve format matches the recommended format for the input type selected Refer to Table 4 1 NOTE sensor reading of the instrument can always be displayed in sensor units If a temperature response curve is selected for an input its readings may also be displayed in temperature 4 10 Operation Lake Shore Model 325 Temperature Controller User s Manual Table 4 2 Sensor Curves Curve Display Sensor Model Temperature For Data Points Number Type Number Range Refer To 01 DT 470 Silicon Diode DT 470 14 475 Table D 1 02 DT 670 Silicon Diode DT 670 14 500 Table D 2 03 DT 500 D Silicon Diode DT 500 D 1 4 365K Table D 3 04 DT 500 E1 Silicon Diode DT 500 E1 11 330 Table D 3 05 Reserved 1000 Plat 250 06 100 1000 Plat 500 100 30 800 Table D 4 07 PT 1000 1000Q Plat
253. ring a pending operation Remote Operation 6 9 Lake Shore Model 325 Temperature Controller User s Manual 6 1 5 IEEE Interface Example Program A Visual Basic program is included to illustrate the IEEE 488 communication functions of the instrument Instructions for setting up the IEEE 488 board is included in Section 6 1 5 1 Refer to Section 6 1 5 2 for instructions on how to setup the program The Visual Basic code is provided in Table 6 2 A description of program operation is provided in Section 6 1 5 3 While the hardware and software required to produce and implement these programs 1s not included with the instrument the concepts illustrated apply to most applications 6 1 5 1 IEEE 488 Interface Board Installation for Visual Basic Program This procedure works for plug and play General Purpose Interface Board GPIB hardware and software for Windows 98 95 This example uses the AT GPIB TNT GPIB card Install the GPIB plug and play software and hardware using National Instruments instructions 2 Verify that the following files have been installed to the Windows System folder a gpib 32 dll b gpib dll c gpib32ft dll Files b and c will support 16 bit Windows GPIB applications if any are being used 3 Locate the following files and make note of their location These files will be used during the development process of a Visual Basic program a Niglobal bas b Vbib 32 bas NOTE Ifthe files in Steps 2 and 3 are not installed on
254. rmocouple input See Figure 3 4 for polarity 2 Place the instrument away from drafts If calibrating using a short place an accurate room temperature thermometer near the terminal block 3 Allow the instrument to warm up for at least hour without moving or handling the sensor 4 Ifcalibrating with a short skip to step 6 otherwise insert the thermocouple into the ice bath liquid nitrogen helium Dewar or other know fixed temperature The temperature should be close to the measurement temperature that requires best accuracy 5 Read the displayed temperature If the temperature display is not as expected check to be sure that the thermocouple is making good thermal contact If possible add a thermal mass to the end of the thermocouple 6 Press the Input Setup key and press the Enter key until the Room Cal screen appears Press the or W key until the selection appears then press the Enter key Operation 4 9 Lake Shore Model 325 Temperature Controller User s Manual Room Temperature Calibration Procedure Continued 7 The current temperature reading is displayed in kelvin Enter the true temperature that the thermocouple should read If input is shorted then enter the actual room temperature measured by the thermometer Press the Enter key to save the value 8 To verify calibration check that the temperature reading for the calibrated input matches the room temperature ca
255. ronize consecutive characters Parity is a method of error detection One parity bit configured for odd parity is included in each character ASCII letter and number characters are used most often as character data Punctuation characters are used as delimiters to separate different commands or pieces of data Two special ASCII characters carriage return CR and line feed LF are used to indicate the end of a message string 6 24 Message Strings A message string is a group of characters assembled to perform an interface function There are three types of message strings commands queries and responses The computer issues command and query strings through user programs the instrument issues responses Two or more command strings can be chained together in one communication but they must be separated by a semi colon Only one query is permitted per communication but it can be chained to the end of a command The total communication string must not exceed 64 characters in length A command string is issued by the computer and instructs the instrument to perform a function or change a parameter setting The format is lt command mnemonic gt lt space gt lt parameter data gt lt terminators gt Command mnemonics and parameter data necessary for each one is described in Section 6 3 Terminators must be sent with every message string query string is issued by the computer and instructs the instrument to send a response The
256. ropdown list select General Add the statement Public gSend as Boolean b Double Click on cmdSend Add code segment under Private Sub cmdSend Click as shown in Table 6 5 c Inthe Code Editor window under the Object dropdown list select Form Make sure the Procedure dropdown list is set at Load The Code window should have written the segment of code Private Sub Form Load Add the code to this subroutine as shown in Table 6 5 2 12 Run the program The program Type exit to end program should resemble the window to the Command right 13 Type ina Response command or query in the Command box as described in Section 6 1 5 5 14 Press Enter or select the Send button with the mouse to send command 15 Type Exit and press Enter to quit 6 12 Remote Operation Lake Shore Model 325 Temperature Controller User s Manual Table 6 5 Visual Basic IEEE 488 Interface Program Public gSend As Boolean Global used for Send button state Private Sub cmdSend Click gSend True End Sub Routine to handle Send button press Set Flag to True Private Sub Form Load Dim strReturn As String Dim term As String Dim strCommand As String Dim intDevice As Integer frmIEEE Show term Chr 13 amp Chr 10 strReturn Call ibdev 0 12 0 T10s 1 amp H140A intDevice Main code section Used to return response Terminators Data string sent to instrument Device number used with IEEE Sho
257. rs enter curves over computer interface The default is blank The instrument must know the data format of the curve breakpoints Different sensor types use different data formats The sensor inputs require one of the formats below The range and resolution specified are not always available at the same time Practical range and resolution depend on the sensor type Curve Sensor Units Sensor Units Format Format Description Full Scale Range Maximum Resolution V K Volts vs kelvin 10 V 0 00001 V Q K Resistance vs kelvin 10 K Q 0 001 Q log Log resistance vs kelvin 4 log Q 0 00001 log Q mV K Millivolts vs kelvin 100 mV 0 0001 mV A setpoint temperature limit can be included with every curve When controlling in temperature the SP Limit setpoint cannot exceed the limit entered with the curve for the control sensor The default is 375 K Set to 9999 K if no limit 1s required The instrument derives the temperature coefficient from the first two breakpoints If it is set Coeff improperly check the first two breakpoints A positive coefficient indicates the sensor signal increases with increasing temperature A negative coefficient indicates the sensor signal decreases with increasing temperature Table 5 2 Recommended Curve Parameters Typical Lake Limit Recommended Sensor Type Shore Model Units Format K Coefficient Resolution Silicon Diode DT 470 V V K 475 Negative 0 00001 V GaAlAs Diode TG 120 V V K 325 Negative 0 00001
258. s are connected to the IEEE 488 bus by a 24 conductor connector cable as specified by the standard Refer to Section 8 7 2 Cables can be purchased from Lake Shore or other electronic suppliers Cable lengths are limited to 2 m for each device and 20 m for the entire bus The Model 325 can drive a bus with up to 10 loads If more instruments or cable length 15 required a bus expander must be used 6 1 1 Changing IEEE 488 Interface Parameters Two interface parameters address and terminators must be set from the front panel before communication with the instrument can be established Other interface parameters can be set with device specific commands using the interface Section 6 3 Press the Interface key The first screen is for selecting the serial interface baud rate and can be skipped by pressing the Enter key The address screen is then displayed as follows Remote Operation 6 1 Lake Shore Model 325 Temperature Controller User s Manual Changing IEEE 488 Interface Parameters Continued Press the or V keys to increment or decrement the IEEE address to the desired number Valid addresses 1 through 30 Default is 12 Press Enter to accept new number or Escape to retain the existing number Pressing Enter displays the Terminators screen Press the V keys to cycle through the following terminator choices CR LF LF CR LF and EOI The default is Cr Lf To accept changes or the curren
259. s correct before proceeding with curve copy To copy a curve press the Curve Entry key Press the or W key until you see the following display Press the Enter key You can press the Escape key any time during this routine to return to the normal display Use the A or key to select the curve number 01 through 35 to copy from Once the curve number is selected press the Enter key You will see the following message Use the A or V key to select the curve number 21 through 35 to copy to Press the Enter key to copy the curve You now return to the normal display 5 3 SOFTCAL The Model 325 allows the user to perform inexpensive sensor calibrations with a set of algorithms called SoftCal The two SoftCal algorithms in the Model 325 work with DT 400 Series silicon diode sensors and platinum sensors They create a new temperature response curve from the standard curve and known data points entered by the user The new curve loads into one of the user curve locations 21 through 35 in the instrument The following sections describe the data points needed from the user and the expected accuracy of the resulting curves Both DT 400 Series and platinum SoftCal algorithms require a standard curve that 1s already present in the Model 325 When the user enters the type of sensor being calibrated the correct standard curve must be selected When calibration is complete the user must assign the new curve
260. s from 0 to 1 bit 6 RQS MSS of the status byte will be set This will send a service request SRQ interrupt message to the bus controller The user program may then direct the bus controller to serial Poll the instruments on the bus to identify which one requested service the one with bit 6 set in its status byte Serial polling will automatically clear RQS of the Status Byte Register This allows subsequent serial polls to monitor bit 6 for an SRQ occurrence generated by other event types After a serial poll the same event or any event that uses the same Status Byte summary bit will not cause another SRQ unless the event register that caused the first SRQ has been cleared typically by a query of the event register The serial poll does not clear MSS The MSS bit stays set until all enabled Status Byte summary bits are cleared typically by a query of the associated event register refer to Section 6 1 4 3 4 The programming example in Table 6 3 initiates an SRQ when a command error is detected by the instrument 6 8 Remote Operation Lake Shore Model 325 Temperature Controller User s Manual Table 6 3 Programming Example to Generate an SRQ Command or Operation Description ESR Read and clear the Standard Event Status Register ESE 32 Enable the Command Error CME bit in the Standard Event Status Register SRE 32 Enable the Event Summary Bit ESB to set the RQS ABC Send improper command to in
261. s in materials and workmanship for the Warranty Period specified above the Warranty Period If Lake Shore receives notice of any such defects during the Warranty Period and the Product is shipped freight prepaid Lake Shore will at its option either repair or replace the Product if it is so defective without charge to the owner for parts service labor or associated customary return shipping cost Any such replacement for the Product may be either new or equivalent in performance to new Replacement or repaired parts will be warranted for only the unexpired portion of the original warranty or 90 days whichever is greater 2 Lake Shore warrants the Product only if it has been sold by an authorized Lake Shore employee sales representative dealer or original equipment manufacturer OEM 3 The Product may contain remanufactured parts equivalent to new in performance or may have been subject to incidental use 4 The Warranty Period begins on the date of delivery of the Product or later on the date of installation of the Product if the Product is installed by Lake Shore provided that if you schedule or delay the Lake Shore installation for more than 30 days after delivery the Warranty Period begins on the 31st day after delivery 5 This limited warranty does not apply to defects in the Product resulting from a improper or inadequate maintenance repair or calibration b fuses software and non rechargeable batteries c software
262. se the A or V key to cycle through the sensor types shown in Table 4 1 with 1000 Plat 250 1000 Plat 500 10000 Plat and NTC RTD being the relevant choices Press the Enter key Operation 4 7 Lake Shore Model 325 Temperature Controller User s Manual 4 4 3 1 Thermal EMF Compensation To keep power low and avoid sensor self heating the sensor excitation is kept low There are two major problems that occur when measuring the resulting small DC voltages The first is external noise entering the measurement through the sensor leads which is discussed with sensor setup The second problem is the presence of thermal EMF voltages sometimes called thermocouple voltages in the lead wiring Thermal EMF voltages appear whenever there is a temperature gradient across a piece of voltage lead Thermal EMF voltages must exist because the sensor is almost never the same temperature as the instrument They can be minimized by careful wiring making sure the voltage leads are symmetrical in the type of metal used and how they are joined and by keeping unnecessary heat sources away from the leads Even in a well designed system thermal EMF voltages can be an appreciable part of a low voltage sensor measurement The Model 325 can help with a thermal correction algorithm The instrument will automatically reverse the polarity of the current source every other reading The average of the positive and negative sensor readings will cancel the th
263. sensitivity from 30 to over 800 With excellent reproducibility they are useful as thermometry standards They follow a standard curve above 70 K and are interchangeable in many applications 1 4 Introduction Lake Shore Model 325 Temperature Controller User s Manual Table 1 2 Typical Sensor Performance Temperature 7 Electronic Measurement Electronic including Example Lake Nominal Typical Sensor Resolution Accuracy Electronic ol Shore Sensor Pod Sensitivity Temperature Temperature Accuracy Stability S Voltage Equivalents Equivalents CalCurve and erature Calibrated Silicon Diode DT 670 SD 13 1 4K 1 644 V 12 49 0 8 mK 13 mK 25 mK 1 6 mK with 1 4H 77K 1 028 V 1 73 mVIK 5 8 mK 76 mK 98 mK 11 6 mK calibration 300K 0 5597 V 2 3 mV K 4 4 mK 47 mK 79 mK 8 8 mK 500 K 0 0907 V 2 12 mV K 4 8 mK 40 mK 90 mK 9 6 mK Silicon Diode DT 470 SD 13 14K 1 6981 V 13 1 mV K 0 8 mK 13 mK 25 mK 1 6 mK with 1 4H 77K 1 0203 V 1 92 mV K 5 2 mK 69 mK 91 mK 10 4 mK calibration 300K 05189V 2 4 mVIK 4 2mK 45 mK 77 mK 84 mK 475 K 0 0906 V 2 22 mVIK 4 6 mK 39 mK 89 mK 9 2 mK GaAlAs TG 120 SD 1 4K 5 391 V 97 5 mV K 0 2 mK 7 mK 19 mK 0 4 mK Diode with 1 4H 77K 1 422 V 1 24 mVIK 16 2 mK 180 mK 202 mK 32 4 m
264. shown there the primary difference between the two loops is their control output Loop 1 Loop 1 the primary control loop is the traditional control loop for a cryogenic temperature controller It includes the largest set of hardware and software features making it very flexible and easy to use Loop 1 uses the heater output as its control output The heater output is a well regulated 25 W DC output with two power ranges This provides quiet stable control for a broad range of temperature control systems in a fully integrated package Loop 2 Loop 2 the auxiliary control loop shares most of the operational features of loop 1 but uses the 2W 10 V output as its control output By itself Loop 2 is capable of driving a sample heater or other low power load It is also suited to drive the programming input of a voltage programmable power supply In combination the controller and supply can be used to control large loads at high temperatures The keypad and display operate on one loop at a time To toggle display and keypad operation between Loop 1 and Loop 2 press the Loop key brief display message indicates which control loop has been selected You can determine which loop is active by looking at the heater output display Loop 1 has Low or High in the heater display Loop 2 has 1 27 in the heater display Also when you select any of the following parameters the active loop number will be displayed Control Setup Setpoint P I D Manual H
265. site www lakeshore com Lake Shore Cryotronics Inc EE Instrument Service Department Monae 575 McCorkle Blvd Westerville OH USA 43082 8888 sales lakeshore com Sales Poma Aadress service lakeshore com Instrument Service Teleohone 614 891 2244 Sales oM 614 891 2243 ext 131 Instrument Service pus 614 818 1600 Sales 614 818 1609 Instrument Service Web Service Request http www lakeshore com sup serf html Instrument Service When contacting Lake Shore please provide your name and complete contact information including e mail address if possible It is often helpful to include the instrument model number and serial number located on the rear panel of the instrument as well as the firmware revision information as described in Section 4 18 8 2 RETURNING PRODUCTS TO LAKE SHORE If it is necessary to return the Model 325 or accessories for recalibration repair or replacement a Return Authorization RA number must be obtained from a factory representative or from the Lake Shore web site NOTE Please do not return a product to Lake Shore without an RA number The following information must be provided to Lake Shore in order to obtain an RA number Instrument model and serial number User name company address phone number and e mail address Malfunction symptoms aoe eee Description of the system in which the product is used If possible the original packing materi
266. sponds to address 4 6 28 Remote Operation IEEE Input Returned Format INCRV Input Format Remarks Example INCRV Input Format Returned Format INTYPE Input Format Example INTYPE Input Format Returned Format Lake Shore Model 325 Temperature Controller User s Manual IEEE 488 Interface Parameter Query IEEE term lt terminator gt lt EOI enable gt lt address gt term n n nn Refer to command for description Input Curve Number Command INCRV lt input gt lt curve number gt term a nn lt input gt Specifies which input to configure A or B lt number gt Specifies which curve the input uses If specified curve parameters do not match the input the curve number defaults to 0 Valid entries 0 none 1 20 standard curves 21 35 user curves Specifies the curve an input uses for temperature conversion INCRV A 23 term Input A uses User Curve 23 for temperature conversion Input Curve Number Query INCRV input term a input Specifies which input to query A or B curve number gt term nn Refer to command for description Input Type Parameter Command INTYPE input sensor type lt compensation gt term ann lt input gt Specifies input to configure A or B lt sensor type gt Specifies input sensor type Valid entries 0 Silicon diode 5 NTCRTD 1 GaAlAs diode 6 Thermocouple 25 mV 2 100 Q pl
267. sted pipes or valves In case of frostbite consult a physician at once If a physician is not readily available warm the affected areas with water that is near body temperature The two most important safety aspects to consider when handling LHe and LN are adequate ventilation and eye and skin protection Although helium and nitrogen gases are non toxic they are dangerous in that they replace the air in a normal breathing atmosphere Liquid products are of an even greater threat since a small amount of liquid evaporates to create a large amount of gas Therefore it is imperative that cryogenic Dewars be stored and the MTD system be operated in open and well ventilated areas Persons transferring LHe and LN should make every effort to protect eyes and skin from accidental contact with liquid or the cold gas issuing from it Protect your eyes with full face shield or chemical splash goggles Safety glasses even with side shields are not adequate Always wear special cryogenic gloves Tempshield Cryo Gloves or equivalent when handling anything that is or may have been in contact with the liquid or cold gas or with cold pipes or equipment Long sleeve shirts and cuffless trousers that are of sufficient length to prevent liquid from entering the shoes are recommended C5 0 RECOMMENDED FIRST AID Every site that stores and uses LHe and LN should have an appropriate Material Safety Data Sheet MSDS present The MSDS may be obtained from the manu
268. strument to generate a command error Monitor bus Monitor the bus until the Service Request interrupt SRQ is sent Initiate Serial Poll Serial Poll the bus to determine which instrument sent the interrupt and clear the RQS bit in the Status Byte ESR Read and clear the Standard Event Status Register allowing an SRQ to be generated on another command error 6 1 4 3 4 Using Status Byte Query STB The Status Byte Query STB command is similar to a Serial Poll except it is processed like any other instrument command The STB command returns the same result as a Serial Poll except that the Status Byte bit 6 RQS MSS is not cleared In this case bit 6 is considered the MSS bit Using the STB command does not clear any bits in the Status Byte Register 6 1 4 3 5 Using the Message Available MAV bit Status Byte summary bit 4 indicates that data is available to read into your bus controller This message may be used to synchronize information exchange with the bus controller The bus controller can for example send a query command to the Model 325 and then wait for to set If the bit has been enabled to initiate an SRQ the user s program can direct the bus controller to look for the SRQ leaving the bus available for other use The MAV bit will be clear whenever the output buffer is empty 6 1 4 3 6 Using Operation Complete OPC and Operation Complete Query OPC The Operation Complete OPC and Opera
269. subsequent zones 4 20 Operation Zone 10 Zone 09 Zone 08 Zone 07 Zone 06 Zone 05 Zone 04 Zone 03 Proportional 0 1 1000 Lake Shore Model 325 Temperature Controller User s Manual Zone Setting WorkSheet Integral 0 1 1000 Derivative 0 200 MHP Output 0 100 Proportional 0 1 1000 Integral 0 1 1000 Derivative 0 200 MHP Output 0 100 Proportional 0 1 1000 Proportional 0 1 1000 Integral 0 1 1000 Integral 0 1 1000 Derivative 0 200 Derivative 0 200 MHP Output 0 100 MHP Output 0 100 Proportional 0 1 1000 Integral 0 1 1000 Derivative 0 200 MHP Output 0 100 Proportional 0 1 1000 Integral 0 1 1000 Derivative 0 200 MHP Output 0 100 Proportional 0 1 1000 Proportional 0 1 1000 Proportional 0 1 1000 Integral 0 1 1000 Integral 0 1 1000 Integral 0 1 1000 Derivative 0 200 Derivative 0 200 Derivative 0 200 MHP Output 0 100 MHP Output 0 100 MHP Output 0 100 Proportional 0 1 1000 Integral 0 1 1000 Derivative 0 200 MHP Output 0 100945 Setpoint Heater Range Off Low High Setpoint Heater Range Off Low High Setpoint Heater Range Off Low High Setpoint Heater Range Off Low High Setpoint Heater Range Off Low High Setpoint Heater Range Off Low High
270. t and direct with no unnecessary jumpers or connections 8 12 4 Thermocouple Input Ranges Calibration Purpose To determine the input offset and gain errors when the input is configured for the thermocouple ranges and provide offset and gain calibration constants back to the Model 325 Process 1 Configure the input for the thermocouple range to be calibrated Turn Room Cal off 2 Reset the calibration constants to their default values using the CALZ and CALG commands EXAMPLE Input A Range Thermo 25mV Zero Offset Command CALZ A 6 0 Gain Command CALG A 6 1 3 Short the V and V terminals together do not tie the terminals to ground 4 Via the interface obtain the input reading using the C ALR EAD command and record this number Service 8 15 Lake Shore Model 325 Temperature Controller User s Manual Thermocouple Input Ranges Calibration Continued 5 Program the offset calibration by negating the value read in the previous step and providing it using the CALZ command EXAMPLE Input A Range Thermo 25mV CALREAD Reading 00 0122 Calibration Command CALZ A 6 0 0122 6 Connect input to standard and DMM with cable described in Section 8 12 1 7 Set the voltage reference to provide the calibration voltage shown in Table 8 3 Using the DMM measure the voltage to the tolerance shown in Table 8 3 Via the interface obtain the input reading using the CALREAD command and record this numbe
271. t character is transmitted Notinitiate communication more than 20 times per second When issuing queries or queries and commands together the user program should Properly format and transmit the query including terminators as one string Prepare to receive a response immediately Receive the entire response from the instrument including the terminators Guarantee that no other communication is started during the response or for 50 ms after it completes Notinitiate communication more than 20 times per second Failure to follow these simple rules will result in inability to establish communication with the instrument or intermittent failures in communication 6 16 Remote Operation Lake Shore Model 325 Temperature Controller User s Manual 6 2 6 Changing Baud Rate To use the Serial Interface you must first set the baud rate Press Interface key to display the following screen Press the A or V key to cycle through the choices of 9600 19200 38400 57600 baud Press the Enter key to accept the new number 6 2 7 Serial Interface Example Program A Visual Basic program is included to illustrate the serial communication functions of the instrument Refer to Section 6 2 7 1 for instructions on how to setup the program The Visual Basic code is provided in Table 6 8 A description of program operation is provided in Section 6 2 7 2 While the hardware and software required to produce and implement these pro
272. t describes one of the most common interfaces between computers and electronic equipment The RS 232C standard is quite flexible and allows many different configurations However any two devices claiming RS 232C compatibility cannot necessarily be plugged together without interface setup The remainder of this section briefly describes the key features of a serial interface that are supported by the instrument A customer supplied computer with similarly configured interface port is required to enable communication 6 2 1 Physical Connection The Model 325 has a 9 pin D subminiature plug on the rear panel for serial communication The original RS 232C standard specifies 25 pins but both 9 and 25 pin connectors are commonly used in the computer industry Many third party cables exist for connecting the instrument to computers with either 9 or 25 pin connectors Section 8 7 1 gives the most common pin assignments for 9 and 25 pin connectors Please note that not all pins or functions are supported by the Model 325 The instrument serial connector is the plug half of a mating pair and must be matched with a socket on the cable If a cable has the correct wiring configuration but also has a plug end a gender changer can be used to mate two plug ends together The letters DTE near the interface connector stand for Data Terminal Equipment and indicate the pin connection of the directional pins such as transmit data TD and receive data RD Equipme
273. ted Name Vice President of Engineering Position Lake Shore Model 325 Temperature Controller User s Manual Electromagnetic Compatibility EMC for the Model 325 Temperature Controller Electromagnetic Compatibility EMC of electronic equipment is a growing concern worldwide Emissions of and immunity to electromagnetic interference is now part of the design and manufacture of most electronics To qualify for the CE Mark the Model 325 meets or exceeds the requirements of the European EMC Directive 89 336 EEC as a CLASS A product A Class A product is allowed to radiate more RF than a Class B product and must include the following warning WARNING This is a Class A product In a domestic environment this product may cause radio interference in which case the user may be required to take adequate measures The instrument was tested under normal operating conditions with sensor and interface cables attached If the installation and operating instructions in the User s Manual are followed there should be no degradation in EMC performance This instrument is not intended for use in close proximity to RF Transmitters such as two way radios and cell phones Exposure to RF interference greater than that found in a typical laboratory environment may disturb the sensitive measurement circuitry of the instrument Pay special attention to instrument cabling Improperly installed cabling may defeat even the best EMC protection For the best
274. terminal block at the same time Figure 8 7 shows the IEEE 488 interface connector pin location and signal names as viewed from the Model 325 rear panel IEEE 488 INTERFACE C 325 8 6 bmp DESCRIPTION Data Input Output Line 1 Data Input Output Line 2 Data Input Output Line 3 Data Input Output Line 4 End Or Identify Data Valid Not Ready For Data NDAC Not Data Accepted IFC Interface Clear SRQ Service Request ATN Attention SHIELD Cable Shield DIO 5 Data Input Output Line 5 DIO 6 Data Input Output Line 6 DIO 7 Data Input Output Line 7 DIO 8 Data Input Output Line 8 Remote Enable Ground Wire Twisted pair with DAV Ground Wire Twisted pair with NRFD Ground Wire Twisted pair with NDAC Ground Wire Twisted pair with IFC Ground Wire Twisted pair with SRQ Ground Wire Twisted pair with ATN Logic Ground mADNAWNE N 13 N NNN ee RRR Re N AR Figure 8 7 IEEE 488 Rear Panel Connector Details Service 8 7 Lake Shore Model 325 Temperature Controller User s Manual 8 8 TOP OF ENCLOSURE REMOVE AND REPLACE PROCEDURE WARNING To avoid potentially lethal shocks turn off controller and disconnect it from AC power line before performing this procedure Only qualified personnel should perform this procedure REMOVAL 1 Set power switch to Off O and disconnect power cord from rear of unit 2 Ifattached remove 19 inch rack mounting
275. terminator choices Cr Lf Lf Cr Lf or EOI where Cr Carriage Return Lf Line Feed and EOI End Or Identify The default terminator is Cr Lf Press the Enter key to accept the changes and continue to the next screen or the Escape key to keep the existing setting and return to the normal display 4 18 DEFAULT VALUES It is sometimes necessary to reset instrument parameter values or clear out the contents of curve memory Both are all stored in nonvolatile memory called NOVRAM but they can be cleared individually Instrument calibration is not affected except for Room Temperature Calibration which should be redone after parameters are set to default values or any time the thermocouple curve is changed To reset the Model 325 parameters to factory default values press and hold the Escape key until the screen shown below appears Use the A or V key to select Yes or No to reset the NOVRAM Select Yes to reset all Model 325 parameters to the defaults listed in Table 4 5 Press the Enter key The second screen appears as follows Use the A or V key to select Yes or No to clear the user curves in locations 21 35 stored in the Model 325 Standard curves in locations 1 20 are unaffected Press the Enter key The instrument performs the operation then returns to the normal display 4 26 Operation Lake Shore Model 325 Temperature Controller User s Manual Table 4 4 Default Values Control Setup
276. the Model 325 where it is called a temperature response curve Getting a curve into a Model 325 may require a CalCurve described below or hand entering through the instrument front panel It is important to look at instrument specifications before ordering calibrated sensors A calibrated sensor is required when a sensor does not follow a standard curve fthe user wishes to display in temperature Otherwise the Model 325 will operate in sensor units like ohms or volts The Model 325 may not work over the full temperature range of some sensors The standard inputs are limited to operation above 1 K even with sensors that can be calibrated to 50 mK 2 2 2 SoftCal SoftCal is a good solution for applications that do not require the accuracy of a traditional calibration The SoftCal algorithm uses the well behaved nature of sensors that follow a standard curve to improve the accuracy of individual sensors A few known temperature points are required to perform SoftCal Lake Shore sells SoftCal calibrated sensors that include both the large interpolation table and the smaller breakpoint interpolation table A CalCurve may be required to get the breakpoint table into a Model 325 where it is called a temperature response curve Refer to Section 2 2 4 The Model 325 can also perform a SoftCal calibration The user must provide one two or three known temperature reference points The range and accuracy of the calibration is based on these points
277. the main control loop Loop 1 can provide up to 25 W of continuous power to a resistive heater load and includes a low range for systems with less cooling power while the Loop 2 heater output can provide up to 2 W of continuous power Both Loop 1 and Loop 2 Heater outputs are short circuit protected to prevent instrument damage if the heater load is accidentally shorted NOTE During normal operation if the input type or input curve is changed for the control input the heater will automatically shut off Specifications of the heater outputs are provided in Section 1 2 Specifications Heater theory of operation is provided in Section 2 4 Heater Selection and Installation Various Heater installation considerations are provided in Section 3 6 Heater Output Setup Once control setup parameters are configured Section 4 7 and the active control loop is selected Section 4 6 1 the desired heater range is selected by pressing the Heater Range key Use the A or V key to cycle through Loop 1 Heater settings Off Low and High Once the desired heater setting is displayed press the Enter key You will return to the normal display Use the A or V key to toggle between Loop 2 Heater settings Off and On Once the desired heater setting is displayed press the Enter key You will return to the normal display To immediately turn the heater off press the Heater Off key If the Heater Range is not being displayed on the front
278. the value of the resistor to the tolerance shown 7 Attach the calibration resistor to the Model 325 sensor input Be sure to connect the resistor using proper 4 lead connection techniques Via the interface obtain the input reading using the CALREAD command and record this number Program the gain calibration by dividing the actual resistance of the calibration resistor by the value read in the previous step and provide the result using the CALG command Note that the gain calibration constant will always be within 5 of 1 00000 EXAMPLE Input A Range 100Q Plat 250 Reversal Off Measured Value of Calibration Resistor 100 0250Q CALREAD Reading 100 145 Constant Calculation 100 0250 100 145 0 99880 Calibration Command CALG A 2 0 99880 10 Send the CALSAVE command to save the constants in the EEPROM 11 Repeat the resistive input ranges calibration for all resistive ranges with reversal on and off 12 Repeat all of Section 8 12 2 for second input if diode resistor 8 14 Service Lake Shore Model 325 Temperature Controller User s Manual Table 8 2 Calibration Table for Resistive Ranges CONES ee 100 Plat 250 100 Q 0 0070 Q Off 2 100 Q Plat 250 100 Q 0 0070 Q On 10 100 Q Plat 500 500 Q 0 0270 Q Off 3 100 Q Plat 500 500 Q 0 0270 Q On 11 1000 Q Plat 5 0 520 Q Off 4 1000 Plat 5 0 520 Q 12 NTC RTD 5 0 520 Q Off 5 NTC RTD 5 0 520 Q
279. tion Complete Query OPC are both used to indicate when pending device operations complete However the commands operate with two distinct methods The OPC command is used in conjunction with bit 0 OPC of the Standard Event Status Register If OPC is sent as the last command in a command sequence bit 0 will be set when the instrument completes the operation that was initiated by the command sequence Additional commands may be sent between the instrument and the bus controller while waiting for the initial pending operation to complete A typical use of this function would be to enable the OPC bit to generate an SRQ and include the OPC command when programming the instrument The bus controller could then be instructed to look for an SRQ allowing additional communication with the instrument while the initial process executes The OPC query has no interaction with bit 0 OPC of the Standard Event Status Register If the OPC query is sent at the end of a command sequence the bus will be held until the instrument completes the operation that was initiated by the command sequence Additional commands except RST should not be sent until the operation is complete as erratic operation will occur Once the sequence is complete a 1 will be placed in the output buffer This function 1s typically used to signal a completed operation without monitoring the SRQ It is also used when it is important to prevent any additional communication on the bus du
280. tion Procedure 1 Use 5 64 in 2 mm hex key to remove two 6 32 x 1 4 black button head screws from side of instrument 2 Place Instrument on shelf 3 Use 5 64 in 2 mm hex key to reinstall two 6 32 x 1 4 black button head screws through side of rack into corresponding holes in the side of the instrument C 325 7 5 bmp Figure 7 4 Model RM 2 Dual Rack Mount Shelf 7 6 Options and Accessories Lake Shore Model 325 Temperature Controller User s Manual CHAPTER 8 SERVICE 8 0 GENERAL This chapter provides basic service information for the Model 325 temperature controller Customer service of the product is limited to the information presented in this chapter Factory trained service personnel should be consulted if the instrument requires repair 8 1 CONTACTING LAKE SHORE CRYOTRONICS Ifa Lake Shore product was purchased through a dealer or representative please use that resource for prompt sales or service information When contacting Lake Shore directly please specify the name of a department 1f do not know the name of an individual Questions regarding product applications price availability and shipments should be directed to sales Questions regarding instrument calibration or repair should be directed to instrument service Do not return a product to Lake Shore without an RA number Refer to Section 8 2 Contact information may change periodically but current contact information can always be found on the Lake Shore web
281. tiple gain stages to accommodate the various sensors the Model 325 supports The input circuitry is not adjusted during calibration Instead precision voltages and resistors are attached to each input and mathematical calibration constants are calculated and programmed into the Model 325 Constants are stored to compensate for both input offset and gain errors Calibration Process 8 12 2 1 Sensor Input Calibration Setup and Serial Communication Verification Allow the Model 325 to warm up for at least 1 hour with 100 kQ resistors attached to all inputs configured as diode resistor and all thermocouple inputs shorted Connect the Model 325 to the PC via the serial port Verify serial communication by sending the IDN command and receiving the proper response from the Model 325 If the input not being calibrated is diode resistor leave a 100 kQ resistor attached If the other input is a thermocouple leave a short across the input 8 12 22 10 pA Current Source Calibration and 1 mA Current Source Verification Purpose To calibrate the 10 pA current source to be within the specified tolerance and verify operation of the 1 mA current source Process 1 Configure the input for the silicon diode range 2 Accurately determine the value of the 100 kQ resistor using the DMM Determine the calibration value by multiplying the actual resistance of 100 resistor by 10 uA Example 100 050 x 10 x 10 1 00050 V 3 Attach the 100
282. tly displayed setting push Enter To cancel changes push Escape 6 1 2 Remote Local Operation Normal operations from the keypad are referred to as local operations The Model 325 can also be configured for remote operations via the IEEE 488 interface or the Local key The Local key will toggle between remote and local operation During remote operations the remote annunciator will be displayed in the top right of the LCD display and operations from the keypad will be disabled 6 1 3 IEEE 488 Command Structure The Model 325 supports several command types These commands are divided into three groups 1 Bus Control Refer to Section 6 1 3 1 a Universal 1 Uniline 2 Multiline b Addressed Bus Control 2 Common Refer to Section 6 1 3 2 3 Device Specific Refer to Section 6 1 3 3 4 Message Strings Refer to Section 6 1 3 4 6 1 3 1 Bus Control Commands A universal command addresses all devices on the bus Universal commands include uniline and multiline commands A uniline command message asserts only a single signal line The Model 325 recognizes two of these messages from the BUS CONTROLLER Remote REN and Interface Clear IFC The Model 325 sends one uniline command Service Request SR Q REN Remote Puts the Model 325 into remote mode Interface Clear Stops current operation on the bus SRQ Service Request Tells the bus controller that the Model 325 needs interface serv
283. to an input The Model 325 does not automatically assign the newly generated curve to either input Calibration data points must be entered into the Model 325 These calibration points are normally measured at easily obtained temperatures like the boiling point of cryogens Each algorithm operates with one two or three calibration points The range of improved accuracy increases with more points There are two ways to get SoftCal calibration data points D The user can record the response of an unknown sensor at well controlled temperatures or Q The user can purchase a SoftCal calibrated sensor from Lake Shore There are advantages to both methods User When the user can provide stable calibration temperatures with the sensor installed SoftCal calibration eliminates errors in the sensor measurement as well as the sensor Thermal gradients instrument accuracy and other measurement errors can be significant to some users Calibration can be no better than user supplied data Q Purchased Lake Shore sensors with SoftCal calibration include a set of calibration points in the calibration report The SoftCal calibration points are generated in a controlled calibration facility at Lake Shore for best accuracy The calibration points can be entered into the Model 325 so it can generate a curve If the CalCurve service is purchased with the calibrated sensor the curve 1s also generated at the factory and can be entered like any other curve 5 6
284. to command for description Celsius Reading Query CRDG lt input gt term a lt input gt AorB lt temp value gt term annnnnn Also see the RDGST command Curve Delete Command CRVDEL lt curve gt term nn lt curve gt Specifies a user curve to delete Valid entries 21 35 CRVDEL 21 term Deletes User Curve 21 Remote Operation 6 25 CRVHDR Input Format Remarks Example Lake Shore Model 325 Temperature Controller User s Manual Curve Header Command CRVHDR lt curve gt lt name gt lt SN gt lt format gt lt limit value gt lt coefficient gt term nn aaaaaaaaaaaaaaa aaaaaaaaaa n cnnn nnn n curve Specifies which curve to configure Valid entries 21 35 lt name gt Specifies curve name Limited to 15 characters lt SN gt Specifies the curve serial number Limited to 10 characters lt format gt Specifies the curve data format Valid entries 1 mV K 2 V K 3 4 log Q K lt limit value gt Specifies the curve temperature limit in kelvin coefficient Specifies the curves temperature coefficient Valid entries 1 negative 2 positive Configures the user curve header CRVHDR 21 DT 470 00011134 2 325 0 1 term Configures User Curve 21 with a name of DT 470 serial number of 00011134 data format of volts versus kelvin upper temperature limit of 325 K The coefficient parameter does not actually set the temperature coefficient It is only a
285. to configure The value for the setpoint in whatever units the setpoint is using Control Setpoint Query SETP lt loop gt term n lt loop gt Specifies which loop to query or 2 lt value gt term nnnnnn Sensor Units Input Reading Query SRDG lt input gt term a lt input gt Specifies which input to query A or B lt sensor units value gt term annnnnn Also see the RDGST command Remote Operation 6 33 Input TEMP Returned Format Remarks TLIMIT Input Format Remarks Example TLIMIT Input Format Returned Format TUNEST Input Returned Format Remarks ZONE Input Format Remarks Example Lake Shore Model 325 Temperature Controller User s Manual Thermocouple Junction Temperature Query lt junction temperature gt term nnnnnnn Temperature is in kelvin This query returns the temperature of the ceramic thermocouple block used in the room temperature compensation calculation Temperature Limit Command Firmware Version 1 5 and Later TLIMIT input lt limit gt term a nnnn input Specifies which input to configure A or B lt limit value gt The temperature limit in Kelvin for which to shut down all control outputs when exceeded A temperature limit of zero turns the temperature limit feature off for the given sensor input A temperature limit setting of 0 K turns the temperature limit feature off TLIM
286. ts the code to 123 LOCK Front Panel Keyboard Lock Query Input LOCK term Returned lt state gt lt code gt term Format n nnn Refer to command for description MODE Remote Interface Mode Command Input MODE mode term Format n mode 0 local 1 remote 2 remote with local lockout Example MODE 2 term Places the Model 325 into remote mode with local lockout MODE Remote Interface Mode Query Input MODE term Returned lt mode gt term Format n Refer to command for description 6 30 Remote Operation MOUT Input Format Example MOUT Input Format Returned Format PID Input Format Remarks Example PID Input Format Returned Format RAMP Input Format Example Lake Shore Model 325 Temperature Controller User s Manual Control Loop Manual Heater Power MHP Output Command MOUT lt loop gt lt value gt term n nnnnnn term lt loop gt Specifies loop to configure or 2 lt value gt Specifies value for manual output MOUT 1 22 45 term Control Loop 1 manual heater output is 22 45 Control Loop Manual Heater Power MHP Output Query MOUT lt loop gt term n lt loop gt Specifies which loop to query 1 or 2 value tnnnnnn term Refer to command for description Control Loop PID Values Command PID loop lt P value I value D value gt term n cnnnnnn c nnnnnn nnnnnn loop Specif
287. ttle information on the cooling power of the cooling system at the desired setpoint If this is the case try the following Allow the load to cool completely with the heater off Set manual heater power output to 50 while in Open Loop control mode Turn the heater to the lowest range and write down the temperature rise if any Select the next highest heater range and continue the process until the load warms up to room temperature Do not leave the system unattended the heater may have to be turned off manually to prevent overheating If the load never reaches room temperature some adjustment may be needed in heater resistance or load The list of heater range versus load temperature is a good reference for selection the proper heater range It is common for systems to require two or more heater ranges for good control over their full temperature Lower heater ranges are normally needed for lower temperature The Model 325 is of no use controlling at or below the temperature reached when the heater was off Many systems can be tuned to control within a degree or two above that temperature 2 7 2 Tuning Proportional The proportional setting 1s so closely tied to heater range that they can be thought of as fine and course adjustments of the same setting An appropriate heater range must be known before moving on to the proportional setting Begin this part of the tuning process by letting the cooling system cool and stabilize with the heater off Plac
288. volts V millivolts mV or ohms Q Press the Enter key The Model 325 has two control modes Closed Loop and Open Loop Closed Loop control often called feedback control is described in Section 2 6 of this manual During closed loop control operation the Control Input Setpoint Heater Range PID and Manual Heater Power MHP output parameters are active Open loop control mode allows the user to directly set the heater output for Loop 1 or Loop 2 with the MHP Output parameter During Open Loop control only the heater range and MHP Output parameters are active To change Control Mode press the Control Setup key and press Enter until the following display appears Use the A or V key to toggle between open and closed loop control Press the Enter key The Power Up setting refers to how the control output will respond after the instrument is powered down Power Up Enable means the controller will power up with the control output in the same state it was before power was turned off Power Up Disable means the controller will always power up with the heater off no matter how it was set when power was turned off To change the Power Up parameter press the Control Setup key and press Enter until the following display appears Use the A or V key to toggle between Power Up Enable and Disable Press the Enter key Operation 4 15 Lake Shore Model 325 Temperature Controller User s Manual Control Setup Continued
289. w main window Terminators are lt CR gt lt LF gt Clear return string Initialize the IEEE device Do Do Wait loop DoEvents Give up processor to other events Loop Until gSend True Loop until Send button pressed gSend False Set Flag as False strCommand frmIEEE txtCommand Text Get Command strReturn Clear response display strCommand UCase strCommand Set all characters to upper case If strCommand EXIT Then Get out on EXIT End End If Call ibwrt intDevice strCommand amp term Send command to instrument If ibsta And EERR Then Check for IEEE errors do error handling if needed Handle errors here End If If InStr strCommand lt gt 0 Then Check to see if query strReturn 5 100 Build empty return buffer Call ibrd intDevice strReturn Read back response If ibsta And EERR Then Check for IEEE errors do error handling if needed Handle errors here End If If strReturn Then Check if empty string strReturn RTrim strReturn Remove extra spaces and Terminators Do While Right strReturn 1 Chr 10 Or Right strReturn 1 Chr 13 strReturn Left strReturn Len strReturn 1 Loop Else strReturn No Response Send No Response End If frmIEEE txtResponse Text strReturn Put response in text on main form End If Loop End Sub Remote Operation 6 13 Lake Shore Model 325 Temperature Controller User s Manual 6 1 5 3 Program Operation Once the program is runnin
290. w point is automatically put into its proper place in breakpoint sequence 5 4 Advanced Operation Lake Shore Model 325 Temperature Controller User s Manual Edit Curve Continued NOTE Typing over an existing reading or temperature will replace that value when you press the Enter key To delete a breakpoint go to point and enter zeros for both the sensor reading and temperature Press the Enter key then the Escape key When curve entry is complete the user must assign the new curve to an input The Model 325 does not automatically assign the new curve to either input 5 2 1 1 Thermocouple Curve Considerations The following are things to consider when generating thermocouple curves Users may enter temperature response curves for all types of thermocouples Enter curve data in mV K format with thermocouple voltage in millivolts and temperature in kelvin The curve must be normalized to 0 mV at 273 15 0 C Thermocouple voltages in millivolts are positive when temperature is above that point and negative when temperature is below that point To convert curves published in Celsius to kelvin add 273 15 to the temperature in Celsius The temperature range for some thermocouple types may extend below 1 K or above 1000 K The input voltage of the 325 is limited to 50 mV so any part of the curve that extends beyond 50 mV is not usable by the instrument A message of S OVER or S UNDER on the display
291. wer to the load but it does not actively control temperature Any change in the characteristics of the load will cause a change in temperature Closed loop control is available for both loops and no tuning is required 4 6 3 Tuning Modes The Model 325 offers three tuning modes or ways to set the necessary P I and D parameters for closed loop control MHP output is active during closed loop control and must be set to zero if not wanted Heater range must also be considered as part of tuning when using control Loop 1 Manual PID Tuning Manual tuning is the most basic tuning method The user manually enters parameter values for P I D and heater range using their knowledge of the cooling system and some trial and error Refer to Sections 2 7 and 4 8 for guidelines Manual tuning can be used in any situation within the control capabilities of the instrument AutoTune The Model 325 automates the tuning process with an AutoTune algorithm This algorithm measures system characteristics after a setpoint change and calculates P I and D The user must set heater range AutoTune will not work in every situation Refer to Sections 2 8 and 4 9 for details Zone Tuning Optimal control parameters values are often different at different temperatures within a system Once values have been chosen for each temperature range or zone the zone feature can automatically select the correct set each time the setpoint is changed This mode does not help choose control p
292. wo surfaces that are in contact Good gasket materials are soft thin and have good thermal conductivity They must also withstand the environmental extremes Indium foil and cryogenic grease are good examples 2 4 Cooling System Design Lake Shore Model 325 Temperature Controller User s Manual 2 3 5 Contact Pressure When sensors are permanently mounted the solder or epoxy used to hold the sensor act as both gasket and adhesive Permanent mounting is not a good solution for everyone because it limits flexibility and can potentially damage sensors Much care should be taken not to over heat or mechanically stress sensor packages Less permanent mountings require some pressure to hold the sensor to its mounting surface Pressure greatly improves the action of gasket material to increase thermal conductivity and reduce thermal gradients A spring clamp is recommended so that different rates of thermal expansion do not increase or decrease pressure with temperature change 2 3 6 Lead Wire Different types of sensors come with different types and lengths of electrical leads In general a significant length of lead wire must be added to the sensor for proper heat sinking and connecting to a bulk head connector at the vacuum boundary The lead wire must be a good electrical conductor but should not be a good thermal conductor or heat will transfer down the leads and change the temperature reading of the sensor Small 30 to 40 AWG wire made of an al
293. y reducing the time it takes for temperature to reach the setpoint It can also see the error decreasing rapidly when the temperature nears the setpoint and reduce the output for less overshoot The derivative term can be useful in fast changing systems but it is often turned off during steady state control because 1t reacts too strongly to small disturbances The derivative setting D is related to the dominant time constant of the load similar to the I setting and is therefore set proportional to setting when used 2 6 4 Manual Heater Power MHP Output The Model 325 has a control setting that is not a normal part of a PID control loop Manual Heater Power MHP output can be used for open loop control meaning feedback is ignored and the heater output stays at the users manual setting This is a good way to put constant heating power into a load when needed The MHP output term can also be added to the PID output Some users prefer to set a power near that necessary to control at a setpoint and let the closed loop make up the small difference MHP output is set in percent of full scale current or power for a given heater range NOTE output should be set to 0 when not in use Cooling System Design 2 9 Lake Shore Model 325 Temperature Controller User s Manual change in setpoint temperature P Only too high actual temperature response a time P Only b P Only too low 1 9 1 P 325 2 3 bmp
294. your computer they may be copied from your National Instruments setup disks or they may be downloaded from www ni com 4 Configure the GPIB by selecting the System icon in the Windows 98 95 Control Panel located under Settings on the Start Menu Configure the GPIB Settings as shown in Figure 6 5 Configure the DEV12 Device Template as shown in Figure 6 6 Be sure to check the Readdress box 6 1 5 2 Visual Basic IEEE 488 Interface Program Setup This IEEE 488 interface program works with Visual Basic 6 0 VB6 on an IBM PC or compatible with a Pentium class processor A Pentium 90 or higher is recommended running Windows 95 or better It assumes your IEEE 488 GPIB card is installed and operating correctly refer to Section 6 1 5 1 Use the following procedure to develop the IEEE 488 Interface Program in Visual Basic 1 Start VB6 2 Choose Standard EXE and select Open 3 Resize form window to desired size 4 On the Project Menu select Add Module select the Existing tab then navigate to the location on your computer to add the following files Niglobal bas and Vbib 32 bas 5 Add controls to form a Add three Label controls to the form b Addtwo TextBox controls to the form Add CommandButton control to the form 6 Onthe View Menu select Properties Window 6 10 Remote Operation Lake Shore Model 325 Temperature Controller User s Manual System Properties 2 x General Device Manager Hardware Pro

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