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Model 330 Model 330 - Lake Shore Cryotronics, Inc.

1. Band 1000 Deviation A 1000 Amplifier Output OV Error Signal FIGURE 2 Output plot of the deviation amplifier showing Proportional Bands for gain settings of 100 and 1000 For the DRC 82C the maximum available gain is 1000 8 Ze I E V Ee em T 3 Error A Signal gt 40 mV 0 A DK 0 8 K 0 K B Leet 16 K 0 FIGURE 3 Output Power versus error signal in voltage or equivalent temperature of sensor for two different power settings A corresponds to a sensor sensitivity of 50 mV K B corresponds to a sensor sen sitivity of 2 5 mV K Note that the curves are linear in voltage not power in mV K is known As an example suppose the sensor producing the error signal in Figure 2 had a sensitivity of 1 mV K and the set point full scale range was 100 mV 100 K The proportional band would then be 8 or 8 K and 80 or 80 K for Ay 1000 and 100 respectively In cryogenic applications this terminology is less significant gain which is multiplicative is usually more useful since it is more easily understood by the user The power output stage of a cryogenic controller may or may not have variable gain associated with it If the controller has several output power stage ranged for example 5 covering 5 orders of magnitude in power as does the DRC 82C then the controller output into a 50 ohm load and with a gain of 200 for 5 watts and 50 watts would have the response shown in figure 3 Note that the overal
2. Half Rack Mounting Kit for One Model 330 Temperature Controller Half length mounting panel and mounting ears to attach one Model 330 to a 482 6 mm 19 inch by 88 9 mm 3 5 inch rack mount space See Figure 6 4 Half Rack Mounting Kit for One Model 330 Temperature Controller with Handles Half length mounting panel mounting ears and handles to attach one Model 330 to a 482 6 mm 19 inch by 88 9 mm 3 5 inch rack mount space See Figure 6 4 Dual Mounting Shelf for Two Model 330 Temperature Controllers Mounting brackets and ears to attach two Model 330 Temperature Controllers side by side on a 482 6 mm 19 inch by 88 9 mm 3 5 inch rack mount shelf See Figure 6 5 Dual Mounting Shelf for Two Model 330 Temperature Controllers with Handles Mounting brackets ears and handles to attach two Model 330 Temperature Controllers side by side on a 482 6 mm 19 inch by 88 9 mm 3 5 inch rack mount shelf See Figure 6 5 IEEE 488 GPIB Computer Interface Interconnect Cable Assembly Connects two IEEE 488 devices The 8072 cable is 1 meter 3 3 feet in length 8271 30 Sensor Heater Cable Assembly For Silicon Diode amp 100 Q Platinum RTD Temperature Sensors Lake Shore Cryogenic Wire Lake Shore sells these types of cryogenic wire WNC Nichrome Heater WSL See Text Single Strand WQT Quad Twist WDT Duo Twist WDL Duo Lead WQL Quad Lead WMW Manganin and WHD Heavy Duty See the Lake Shore Catalog for detail
3. Returns the currently selected sensor curve number for Channel B Table 3 1 lists sensor curve numbers Channel B Input Type Query BTYPE SI PT AS TC Or ER Returns input type for Channel B SI silicon diode PT platinum AS GaAlAs TC thermocouple ER error improper switch setting Curve Identification Query CUID WW XXXXXXXXXXXXXXXXXX Y ZZ2 Returns header lines identifying standard sensor and user curves loaded in each curve location Information lines for sensor curves 11 thru 31 are available only if the curves actually exist either as a user generated curve or as precision option curve Data returned is defined as follows W Curve number From 00 to 31 X Curve description 18 character information line All 18 spaces need not be used Y Temp coefficient N negative coefficient P positive coefficient Z Number of points The number of points for the curve usually 31 but can be up to 99 00 STANDARD DRC D N 31 01 STANDARD DRC E1 N 31 02 STANDARD CRV 10 N 31 03 STANDARD DIN PT P 31 CURV 4 20 Input Returned Remarks Initiate User Curve CURV AA SBOCCCCCCCCCCCCCCC D DDDDD EEE E Y YYYYY ZZZ Z Nothing If using the IEEE 488 interface enter an entire curve with CURV If using the Serial Interface the 256 character buffer prevents loading the entire curve all at once For Serial Interface only use CURV to enter the first two points and then the ECUR command t
4. 15 Repeat Steps 11 14 for Channel B except adjust R8 16 Power off the Model 330 17 Disconnect the test connector 18 Switch the input back to the desired sensor type 19 Follow the REPLACE TOP procedure in Paragraph 5 6 Service amp Calibration 5 7 Lake Shore Model 330 Autotuning Temperature Controller User s Manual FRONT TP3 JMP9 Heater 250 500 R28 ca U47 U16 Wem SV HEX Slave EPROM ka O e EI o qe 338 CONTROLLER MAIN BOARD 111 282 D E U12 Precision Option NOVRAM NOVRAM 1 g D e N i R21 N rj R26 R10 DC HEX U11 DC HEX Master EPROM g E TP2 e T re Dies em X coz N DE 1 Channel A Sensor DIP Switch TPL 2 Channel B Sensor DIP Switch TP1 New C 330 U 5 9 Figure 5 9 Typical Model 330 PCB Layout 5 8 Service amp Calibration Lake Shore Model 330 Autotuning Temperature Controller User s Manual 5 11 MODEL 330 4X THERMOCOUPLE CALIBRATION 1 2 5 6 Follow the REMOVE TOP procedure in Paragraph 5 6 AID Calibration Connect V lead of voltmeter to TP2 of the main board
5. C is 0 00000 mV and it loads as 4 50000 V Temperature loads in K 2 because there are not enough digits in the temperature format to store numbers larger than 999 9 K The temperature at full scale 1273 K should be loaded as 636 5 The first three characters of the description field must be S99 this sequence tells the Model 330 that it has a 51 configuration Model 330 51 Specifications Model Number Sensor Type Thermocouple Sensor Temperature Coefficient Positive Sensor Units Millivolts mV Input Range 45 mV Sensor Excitation Example Lake Shore Sensor Sensor Temperature Range Standard Sensor Curve NIST generated Typical Sensor Sensitivity 40 uV K at 300 K Measurement Resolution Sensor Units 1 5 uV Temperature Equivalence 37 mK at 300 K Sensor Unit Display Resolution 2 uV Measurement Accuracy 4 uV 40 1 RDG Temperature Accuracy with Calibrated Sensor and 8001 Precision Option 0 15K at 300 K t Measurement Temp Coefficient Sensor Units RDG C 0 018 Temperature Equivalence 40 mK C at 300 K Setpoint Display Resolution in Sensor Units 5 Thermocouple data are for uncompensated input T No Model 8001 Precision Calibration Option is available for thermocouples Error listed is for the controller only 6 2 Options and Accessories Lake Shore Model 330 Autotuning Temperature Controller User s Manual 6 3 ACCESSORIES Accessories are devices that perform a secondary duty as an aid or refinement to the primary
6. SoftCal Calibration With regards to accuracy there are 3 things that can be done with a temperature sensor Precision Calibration Standard sensors are A Lake Shore SoftCal can only be Lake Shore can do a precision interchangeable within the performed on Silicon Diodes For a calibration on most sensor types Up published tolerance band 2 point SoftCal data points are to 99 separate data points can be Standard Curve 10 Tolerance taken at 77 35 K and 305 K Fora3 taken with the ability to concentrate Accuracy Bands for DT 470 point SoftCal data points are taking data in areas of particular are listed below taken at 4 2 K 77 35 K and 305 K interest Ty pical calibration accuracy 2K 100 K 305K Typical 2 Point Accuracy for silicon diodes is listed below 100K 305K 375K 10K 2Kto 30K Typical Precision Cal Accuracy GE Lee 20K te 0k OE d e V o p Se 10K 12mK 20mK 1 of Temp 10 29 fee mE loce 20K 15mK 25mK 1 of Temp 1 0 K 375 K to 475 K 30K 25mK 45mK Temperatures down to 1 4 K only Typical 3 Point Accuracy 50K 30mK 55mK with a Precision Calibrated Sensor 0 5K 2 Kto lt 30 K 100K 25mK 50mK To increase accuracy the pu M ips 3005 oodmis Umi 0 15K 60K to lt 345 K 340K 100 mK User may perform a 0 25K 345K to lt 375 K 480K 100 mK SoftCal with his controller 1 0K 375 K to 475 K and sensor Once a sensor is A curve is fitted to these points A calibrated the standar
7. User s Manual Model 330 Autotuning Temperature Controller Includes Coverage For Model 330 1X Silicon Diode Model 330 2X Platinum Resistor Model 330 3X GaAlAs Diode Model 330 4X Thermocouple Model 330 5X Thermocouple E1 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 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 Rev 1 3 P N 119 009 15 November 2000 Lake Shore Model 330 Autotuning Temperature Controller User s Manual LIMITED WARRANTY Lake Shore Cryotronics Inc henceforth Lake Shore the manufacturer warrants this product to
8. Chromel DT 470 Series silicon 95429 Type E diodes follow the same 3 525 TypeK Type T User Curves or Precision Calibration Option See Table 3 1 standard temperature 3 485 response Curve 10 which allows them to interchange with one another Lake Shore programs Curve 10 into all Temperature Controllers Digital Thermometers and Temperature Transmitters DT 470 Series silicon diode sensors come in five bands of tracking accuracy allowing selection based on both performance and expense Values are for thermocouples with compensation Uncompensated thermocouples can use full 15 mV range Platinum Curve Users of the Model 330 2X have the option of the standard platinum curve or the precision option The standard platinum curve see Appendix C conforms to DIN 43760 1980 IEC 751 1983 and 1904 1984 DIN 43760 is the standard that defines the characteristics of a 100 Q platinum RTD with a resistance vs temperature curve specified by a 0 00385 Q Q C Thermocouple Curves Select the curve that matches the type of thermocouple used User Curves 11 thru 31 In addition to the standard curves Curve Numbers 11 thru 31 provide space for 20 user defined curves see Table 2 3 They may be user defined curves Precision Calibration Option Curves purchased from Lake Shore see Paragraph 2 9 or curves purchased from other vendors User defined curves can have up to 97 points plus two end points Load points into the controller
9. Heater Noise Front Panel Display Display Units Setpoint display Heater output display Annunciators Temperature resolution Sensor units resolution Keypad Computer Interfaces IEEE 488 Capabilities Serial Interface General Ambient Temperature Range Power Requirements Size Weight Table 1 2 Model 330 Specifications Two Model 330 1X Silicon Diode Model 330 2X Platinum RTD Model 330 3X GaAlAs Diode Model 330 4X Thermocouple Based on Model and Sensor Type Refer to Table 1 1 Both Channels in 1 second Room for twenty 31 point Curves Curve 10 DRC D or DRC E1 Obsolete DIN 43760 Ch AuFe 0 07 Ch AuFe 0 03 Type E Chromel Constantan Type K Chromel Alumel and Type T Copper Constantan Entered in Voltage or Temperature Digital three term PID with Autotuning P PI or PID control user selectable Gain Proportional 1 999 Reset Integral 1 999 sec and Rate Derivative 0 200 0 500 sec To 2 5 mK in a properly designed system for diode sensors Refer to Table 1 1 0 01 K or C below 200 least significant display digit in sensor units Front Panel 0 1 to 99 9 K min 10 Zones with Setpoint P D and Heater Range Variable DC Current Source 15 bits 50 Watts 25 Watts Field Configurable High 1 A Medium 0 3 A and Low 0 1 A 50 V 50 W or 25 V 25 W 50 Q 50 W or 25 Q 25 W 35 Q 50 W or 10 Q 25 W 50 uV 0 01 of output vo
10. I Manually adjusts control loop reset Integral term See Paragraph 3 3 5 2 D Manually adjusts control loop rate Derivative term See Paragraph 3 3 5 3 Heater Cycles heater display between LOW MEDIUM HIGH and OFF See Paragraph 3 3 1 Operation 3 1 Lake Shore Model 330 Autotuning Temperature Controller User s Manual Set Point Displays or adjusts the control loop temperature setpoint Paragraph 3 3 2 Press and hold this key to access the ramp rate feature where the user sets the rate at which the temperature setpoint automatically increases or decreases when the user changes the setpoint value See Paragraph 3 3 3 Control Returns bottom display to Control sensor readouts after reading or adjusting the setpoint See Paragraph 3 3 2 Escape Terminate a function without changing existing settings To reset most controller parameters to factory defaults press and hold both the Escape and Units keys for about 20 seconds See Paragraph 3 4 4 A Used in conjunction with other keys to increment or toggle readings in the upper Sample window V Used in conjunction with other keys to increment or toggle readings in the lower Control window Enter Accepts changes made in the field display Press and hold the Enter key to access the Power Up PUP configuration setup display See Paragraph 3 4 5 Local Switches controller between Local LOC and Remote REM operation See Paragraph 3 4 3 SoftCal Improves silicon diode sensor
11. In a two wire measurement configuration the voltage connections point A in Figure 1 are made near or at the current Source so only two leads are actually connected to the device Some loss in accuracy can be expected since the voltage measured at the voltmeter is the sum of the diode voltage and the voltage drop across the connecting leads The exact temperature uncertainty will depend on the temperature range and lead resistance For a 10 ohm lead resistance the diode voltage will be offset by 0 1 mV which gives a negligible temperature error at liquid helium temperature but a 50mK error near liquid nitrogen temperature Note the DI and CY adapter can be used only in a two wire configuration An excessive heat flow through the connecting leads to any temperature sensor can create a situation where the active sensing element for the DT 470 this is the diode chip is at a different temperature than the sample to which the sensor is mounted This is then reflected as a real temperature offset between what is measured and the true sample temperature Such temperature errors can be eliminated by proper selection and installation of the connecting leads In order to minimize any heat flow through the leads the leads should be of small diameter and low thermal conductivity Phosphor bronze or manganin wire is commonly used in sizes 32 or 36 AWG These wires have a fairly poor thermal conductivity yet the resistivities are not so large as to create any proble
12. Returned Remarks Example xSRE Input Returned Remarks xSTB Input Returned Remarks xTST Input Returned Remarks xWAI Input Returned Remarks 4 12 Lake Shore Model 330 Autotuning Temperature Controller User s Manual Query Operation Complete OPC 1 Format n term Places a 1 in the controller output queue upon completion of all pending selected device operations Send as the last command in a command string Not the same as OPC Reset Instrument RST Nothing Sets controller parameters to power up settings Configure Status Reports in the Service Request Enable Register SRE bit weighting Nothing Each bit has a bit weighting and represents the enable disable status 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 See the STB command for a list of status flags To enable status flags 0 3 4 and 6 send the command SRE 89 term 89 is the sum of the bit weighting for each bit Bit Bit Weighting Event Name 0 1 New A amp B 3 8 Alarm 4 16 Error 6 64 SRQ 89 Query the Configuration of Status Reports in the Service Request Enable Register SRE lt SRE bit weighting Format nnn term The integer returned represents the sum of the bit weighting of the enabled bits in the Service Request Enable Register See the STB command for a list o
13. Run IBTEST to test software configuration Do not install the instrument before running IBTEST Run IBCONF to configure the GPIB PCII IIA board and dev 12 Set the EOS byte to OAH See setup in Fig 4 1 IBCONF modifies gpib com 7 Connectthe instrument to the interface board and power up the instrument Verify address as 12 and terminators as CR LF Qv dms cos 4 1 4 2 Running The Example QuickBasic Program Copy c gpib pc Qbasic qbib obj to the QuickBasic directory QB4 2 Change to the QuickBasic directory and type link q qbib obj bqlb4x lib where x 0 for QB4 0 and 5 for QB4 5 This one time only command produces the library file qbib glb The procedure is found in the National Instruments QuickBasic readme file Readme qb 3 Start QuickBasic Type qb I qbib qlb Start QuickBasic in this way each time the IEEE interface is used to link in the library file Create IEEE sample interface program in QuickBasic See Table 4 1 Name file ieeeexam bas and save Run the program 4 1 5 Notes On Using the IEEE Interface To chain commands or queries together insert a semi colon between them Multiple queries cannot be chained The Model 330 responds to the last query entered when addressed as a talker Queries generally use the same syntax as an associated setting command followed by a question mark They most often return the same information that is sent Some queries have no command form Add a query to the end
14. 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 330 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 330 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 and the or symbol Apiezon is a trademark of Biddle Instruments CalCurve Carbon Glass Cernox Duo Twist Quad Lead Quad Twist and SoftCal are trademarks of Lake Shore Cryotronics Inc Chromel and Alumel are trademarks of Hoskins Manufacturing Company Cryo Gloves is a trademark of Tempshield Formvar is a trademark of Monsanto Chemical Company MS DOS and Windows 95 98 N
15. 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 See the ESR command for a list of event flags To enable event flags 0 3 4 and 7 send the command ESE 143 term 143 is the sum of the bit weighting for each bit Bit Bit Weighting Event Name 0 1 OPC 3 8 DDE 4 16 EXE 7 128 PON 143 Query the Configuration of Status Reports in the Standard Event Status Register ESE lt ESE bit weighting gt Format nnn term The integer returned represents the sum of the bit weighting of the enable bits in the Standard Event Status Enable Register Query Standard Event Status Register ESR lt ESR bit weighting gt Format nnn term Queries for various Model 330 error conditions and status The integer returned represents the sum of the bit weighting of the event flag bits in the Standard Event Status Register Query Identification IDN manufacturer model number serial number firmware date Format LSCI MODEL330 aaaaaa nnnnnn term Identifies the instrument model and software level Operation Complete Command OPC Nothing 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 xOPC Input Returned Remarks xRST Input Returned Remarks xSRE Input
16. exceeds 1 kelvin at a nominal 3 Hz frequency That variation represents an inherent disadvantage which is difficult for the all digital system to overcome since the sampling rate is lower than the frequency of the temperature variation The Sampling Theorem of Electrical Engineering implies that no sampled data control system can be stable unless it is sampled at a rate which exceeds at least twice the highest frequency variation within the system Some designers of all digital controllers for cryogenic temperatures appear to have overlooked this sampling rate problem There are also examples of digital controller which fail to achieve optimum performance because of the design of their output stage heater power is varied on a cyclical time proportioning ON OFF basis This often introduces noise within the system which may interfere with the cryogenic experiment An advantage that the microprocessor and its read only memory provides for users of digital controllers is that of a direct reading in temperature set point and sensor readout However as noted in Section III this feature may exact a price In the real world there is always an error due to lack of perfect conformity between the true sensor voltage or resistance temperature characteristic and the value actually stored in memory This error will depend on the degree of non linearity of the characteristic and on the amount of storage available It is seldom cost effective to keep the conformit
17. s Manual Accessories included with a new Model 330 Options and Accessories 6 3 Lake Shore Model 330 Autotuning Temperature Controller User s Manual EI perra eg Cable Length 4 3 meters 14 feet C 330 U 6 1 Figure 6 1 Model 2001 RJ 11 Cable Assembly 0000000000000 2000000000000 1 69 inches 1 5 8mm 0 63 inches C 330 U 6 2 wmf Figure 6 2 Model 2002 RJ 11 to DB 25 Adapter o o9 o Se oo seuout gez 1 Uu G ZE O Eman 60 3 mm 2 37 inches bg KE 15 9 mm 0 63 inches C 330 U 6 3 emf Figure 6 3 Model 2003 RJ 11 to DE 9 Adapter 6 4 Options and Accessories Lake Shore Model 330 Autotuning Temperature Controller User s Manual NOTE To avoid blocking the fan half rack mounting must have the blank panel on the right side as shown The Model RM 3H1 is the basic half rack mounting kit The Model RM 3H1 H addes the two handles Item Description P N Qty 1 Rack Mount Ear 107 049 1 2 Screw 6 32 x 1 2 Inch 0 035 2 FHMS Phillips 3 Rack Mount Support 107 046 1 4 Rack Mount Plate 107 051 1 5 Screw 8 32 x 3 8 Inch 0 081 2 FHMS Phillips 6 Screw 6 32 x 1 2 inch 0 044 2 PHMS Phillips Additional Parts for Model RM 3H1 H 7 Rack Mount Handle 107 433 2 8 Screw 8 32 x 3 8 inch 0 081 4 FHMS Phillips C 330 U 6 4 Figure 6 4 Model RM 3H1 H Rack Mount Kit Options and Accessories 6 5 Lake Shore Model 330 Autotuning Temperature Contro
18. 0 5 Watts for a 25 W heater setting is 25 volts so a 100 Q heater resistance would allow a maximum power output of 6 25 watts 25V 1000 If the heater load drops below 10 Q for a 25 W heater setting or 35 for a 50 W heater setting the output turns off to prevent instrument overheating If this occurs cycle the heater range through OFF to re engage the heater NOTE The heater output is isolated from earth ground To prevent heater noise coupling into the measurement do not allow the heater output to contact earth ground Within a cryostat use 30 gauge stranded copper lead wire ND 30 to connect to the heater Do not run heater leads coincident with the sensor leads due to potential capacitive pick up between the two sets of leads If heater leads must be close to sensor leads twist them so they cross at 90 degrees Error 30 Er30 appears if measured heater output does not match the predicted output and the controller turns the heater off Check heater resistance and test for shorts in heater wiring then turn the heater on again If the error message returns consult the factory 2 10 RACK MOUNTING The Model 330 ships with plastic feet ready for use as a bench instrument As an option the Model 330 installs in a standard 19 inch instrument rack For information on the optional Model 3022 Half Rack Mounting Kit for a single controller see Paragraph 6 3 and Figure 6 4 For information on the optional Model 3026 Dual Mount
19. 2 6 2 6 2 2 Thermocouple Wire Types at Cryogenic Temperatures sesssssrisssrrsserrrssrrrreseerrssne 2 6 2 6 3 Sensor Input Error Messages 0 cccceeceeteeseeeeeeeneeeeeecneeeeeeenanetecneeeedecseneteeeneeeedeensneeees 2 7 2 7 Sensor Curve Selection 2 ccccccccceteecanceeeeeeneeteeeaneeeeecesesesdeeesenaueeeseeeanseeeeadeceteeeaneeeeneees 2 7 2 8 Precision Calibration Option 2 8 2 9 Heater Setup eranc tom a ete det t ete de a ace teret 2 9 2 10 Rack Mounting heat LI rai uec Ad d e SUC e dee mE T e ep p ea en en 2 9 2 11 POQWORUUD rm 2 9 2 11 1 Power Up Sequence nine ecl Seege sedere en deen 2 9 2 11 2 Power Up PUP Configuration sseeeeeene enne nennen 2 10 2 11 3 Power Up Entors iv tags cee teint eer te ee ee e QU ago Dee ne Deo tue e Tene ee oe Dus ue i Dune a eR 2 10 3 OPERATION ME 3 1 3 0 eru cl ee PEE 3 1 3 1 Definition of Front Panel Controls A 3 1 3 1 1 Front Panel Keypad Definitions eeeeeeeeeeeee eene nennen tnter 3 1 3 1 2 Front Panel LED Display ii tede ceti imer tet 3 2 3 2 Thermometry Functions ieeeseseeeee entente tenete tnnt nen treni inne nnne nnn ien nnn int 3 2 3 2 1 Jegen Ke E 3 3 3 2 2 Channels tete A Lean di E d LE d 3 3 3 2 3 Units iie ni bcne elio innotuit oic tee Sere cee M 3 3 3 2 4 Thermocouple Temperature Compensation Model 330 4X Only 3 3 3 2 5
20. 4 15 4 3 5 Lake Shore Model 330 Autotuning Temperature Controller User s Manual Control Process Commands Control Process Commands allow the interface to change any of the Model 330 control parameters Access Manual mode PID parameters as well as Autotuning status CLIM Input Returned Remarks Example CLIM Input Returned Remarks Example GAIN Input Returned Remarks Example GAIN Input Returned Remarks HEAT Input Returned Remarks RAMP Input Returned Remarks RAMP Input Returned Remarks 4 16 Set Control Limit Band for Control Sensor CLIM XXX X Nothing Sets the control limit band for the control sensor Enter a value from 0 to 999 9 Used in conjunction with the Service Request function It utilizes the free field format See the Status Byte Register and the Control Limit Exceeded Bit Bit 2 discussions CLIM 1 25 term results in a control limit of 1 25 K or C Control Limit Query CLIM XXX X a number from 0 to 999 9 Returns the control limit setting The example above in the CLIM command returns 001 25 term Set Gain While In Manual Control Mode GAIN XXX Nothing Enter an integer from 0 to 999 GAIN 65 term instructs the Model 330 to set control gain to 65 Gain corresponds to the Proportional P portion of the PID Autotuning control algorithm Gain Query GAIN XXX Integer from 000 to 999 Returns current gain set
21. 52166 1 50272 1 48443 1 46700 1 45048 1 43488 1 42013 1 40615 1 39287 1 38021 1 36809 1 35647 1 34530 1 33453 1 32412 1 31403 1 30422 1 29464 1 28527 1 27607 1 26702 1 25810 1 24928 1 24053 1 23184 1 22314 1 21440 19645 1 1 17705 1 15558 1 13598 1 12463 1 11896 1 11517 1 11212 1 10945 1 10702 1 10263 1 09864 1 09490 1 09131 1 08781 1 08436 1 08093 1 07748 1 07402 1 07053 1 06700 1 06346 1 05988 1 05629 1 05267 1 04353 1 03425 1 02482 1 01525 1 00552 0 99565 0 98564 0 97550 0 95487 0 93383 0 91243 0 89072 0 86873 0 84650 0 82404 0 80138 0 77855 0 75554 0 73238 0 70908 0 68564 0 66208 0 63841 0 61465 0 59080 0 56690 0 54294 0 51892 0 49484 0 47069 0 44647 0 42221 0 39783 0 37337 0 34881 0 32416 0 29941 0 27456 0 24963 0 22463 0 19961 0 17464 0 14985 0 12547 0 10191 0 09062 Lighter numbers indicate truncated portion of Standard Curve 10 corresponding to the reduced temperature range of DT 471 diode sensors The 1 4 K to 325 K portion of Curve 10 is applicable to the DT 450 miniature silicon diode sensor Application Notes Lake Shore Model 330 Autotuning Temperature Controller User s Manual POLYNOMIAL REPRESENTATION Curve 10 can be expressed by a polynomial equation based on the Chebychev polynomials Four separate ranges are required to accurately describe the curve Table 1 lists the parameters for these ranges The pol
22. Copper Constantan Type T is a thermocouple pair consisting of Cu Copper as the positive thermoelement and a Cu Ni alloy Constantan as the negative element It may be used in a vacuum as well as oxidizing reducing or inert environments down to 90 K At temperatures below 80 K the thermoelectric properties of the positive thermoelement depend largely on the impurity of iron The high thermal conductivity of the copper element makes this thermocouple the least usable for cryogenic applications Sensitivity at 20 K 4 6 uV K Chromel CuFe 0 15 The Chromel Copper Iron thermocouple consists of a Ni Cr alloy Chromel as the positive thermoelement and a Copper 0 15 Iron alloy as the negative thermoelement Sensitivity at 4 2K gt 11 pu V K Less expensive than Gold Chromel thermocouples and physically stronger Recommended useful temperature range is 4 K to 300 K 2 6 Sensor Input Error Messages If an input signal from the sensor exceeding full scale is applied to the input leads an overload condition exists and is indicated by OL on the display If no signal or a signal of the wrong polarity exists at the input leads a Zero Error is indicated by Er27 for Channel A or Er28 for Channel B The Model 330 displays dashes if the input switch is improperly set 2 SENSOR CURVE SELECTION For accurate temperature readings select the response curve that matches the sensor used To determine curves cur
23. DI e Gnd RED E N RxD BLACK a NT o Figure 5 6 Model 2001 RJ 11 Cable Assembly Wiring Details NOT USED For Customer supplied computer with DB 25 Serial Interface Connector configured as DCE If the interface is DTE a Null Modem Adapter is required to exchange Transmit and Receive lines Receptacle DB 9 CONNECTOR NOT USED For Customer supplied computer with DE 9 Serial Interface Connector configured as DTE If the interface RJ11 is DCE a Null Modem Adapter is required to Receptacle exchange Transmit and Receive lines Figure 5 8 Model 2003 RJ 11 to DE 9 Adapter Wiring Details 5 4 Service amp Calibration Lake Shore Model 330 Autotuning Temperature Controller User s Manual 5 6 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 REMOVE TOP 1 Turn off the controller and disconnect the line cord from rear of controller 2 Use Phillips screwdriver to remove 6 screws 3 on top of each side of the controller 3 Slide the top up and off REPLACE TOP 4 Replace the top enclosure 5 Use Phillips screwdriver to replace 6 screws 3 on top of each side of the controller 6 Reconnect power cord to rear of controller and set power switch to on 5 7 OPERATING SOFTWARE EPROM AND PRECIS
24. Display Fitter TEE 3 4 3 2 6 UV ON cor tee esate aaa tae E ege 3 4 Table of Contents Lake Shore Model 330 Autotuning Temperature Controller User s Manual Chapter Paragraph Title Page 3 2 7 SoftCalz isdem mure EARS 3 5 3 2 7 1 lone sigo 3 5 3 2 7 2 Customer Performed Gott al 3 6 3 2 7 3 Entering Voltage Values from a Lake Shore SoftCal Report 3 6 3 3 GontroL EUnctlorns 5 etr tore Er PRIOR RI RED IE RIEN UM DAE 3 8 3 3 1 nica P EE 3 8 3 3 2 Setpoint and Entree Seege OU ERR eB REM ee 3 8 3 3 2 1 Voltage Resolution Models 321 1X 3X amp AX Only 3 9 3 3 2 2 Resistance Resolution Model 330 2X On 3 9 3 3 3 E Tune GEET 3 9 3 3 4 PAULOTUNG oorr E LA mU ML EM Me 3 9 3 3 4 1 Initial Values of PID Parameters in Autotuning Mode 3 10 3 3 4 2 Minimum Oversboct enne esent nenne E aE a nnne nns 3 10 3 3 4 3 Minimum Time To Setpoint aiaee oae t ec et aee c REL Abc etes 3 10 3 3 4 4 Gain ul EE 3 10 3 3 5 Manual Control Settings DD 3 10 3 3 5 1 Setting Gain Proporttonal enm eene nnns 3 10 3 3 5 2 Setting Reset Integral eee eet ete ana terns 3 10 3 3 5 3 Setting Rate Derivative 2 creer entren tt se th na tane den nnn ens 3 11 3 3 5 4 Effect of Temperature on Tuning Parameters eesseseeeesseesesrreserrresrrrssrrrssrrenssens 3 11 3 3 6 ENEE le DE 3 11 3 4 Interface and Miscellaneous FUNCTIONS eee 3 13 3 4 1 Baldi nc tec c DELE Ar tu LA er e UA d er rere ee
25. Enter while holding the Input Type key The display to the right appears Once the filter display appears continue to hold the Input Type key and press the Enter key again to cycle the display filter on and off Release when the appropriate reading appears 3 2 6 Curve For accurate temperature readings select the response curve that matches the sensor To determine the currently selected curve press Curve The default curve for the Model 330 11 is Curve 10 see Table 3 1 The display tot the right shows both the Channel A and B Sensor using Curve 02 the default setting for a Model 330 11 with two Silicon Diode Sensors Curves 0 10 are standard curves included with the instrument Curves 11 31 are user defined curves or Precision Option Calibrations See Table 3 1 To change the curve while pressing the Curve key press the A key to increment the Channel A Curve number or the V key to increment the Channel B Curve number Available curve numbers are 00 through 31 Release when the desired curve number appears then push the Curve key again If the selected Curve number displays then the Curve has the correct temperature coefficient for the sensor A different Curve number indicates an incorrect temperature coefficient for that type sensor The Curve number changes to the default curve number for that type sensor Table 3 1 Sensor Curves 1 325 D DT 500 DRC Curve D 1 325 E1 DT 500 DRC Curve E1 1 325 DT 470 DT 400 Series Se
26. GAIN PLUS INTEGRAL RESET TEMPERATURE CONTROL The manual reset adjustment described above varies markedly with the temperature set point and with the often changing heater power demands of the system Thus it is normally neither convenient nor desirable to have to resort to such a means of eliminating temperature droop offset Instead suppose a circuit could be added to the loop that would 1 sense that there is a steady state offset signal within the proportional band 2 make a bit by bit addition to the power output proportional to the magnitude of the offset and 3 continue the corrective action until the offset is reset to zero The practical realization of this circuit is an integrator inserted between the deviation amplifier and the power stage The origin of the interchangeable terms integral control and automatic reset is evident How does a proportional plus integral controller behave in a cryogenic system First in the idealized case let us again assume an infinite thermal conductivity which results in zero thermal resistance between the sensor and the heater The reset integrator continues to integrate until the error signal reaches zero which stops the integral action but keeps its output at the level corresponding to that needed by the power stage to overcome the droop This output is now the only drive to the power stage since the proportional error signal has been forced to zero No overshoot will occur since zero the
27. K 72 mK at 77 K 32 mK at 300 K 0 1 mV to 1 mV 200 uV 0 035 40 mK at 4 2 K 350 mK at 77 K 105 mK at 300K 235 mK at 800K 0 006 5 mK at 4 2 K 50 mK at 77 K 50 mK at 300 K 0 45 uV 30 mK at 4 2 K 22 mK at 300 K 1 uv 1 5 uV 0 1 RDG 406 mK at 4 2K T 110 mK at 300K 150 mK at 300 K 0 01 40 mK at 4 2 K 40 mK at 300 K Table 1 1 identifies the input configurations possible with this instrument System performance with any of the inputs depends greatly on sensor characteristics Much of the typical data presented here is based on the Lake Shore sensor listed in each column Other sensors of the same type can be used with the instrument Similar performance can be expected if the sensor sensitivities match Introduction 1 3 Lake Shore Model 330 Autotuning Temperature Controller User s Manual Thermometry Number of Inputs Sensor Types Sensors Sold Separately Accuracy Update Rate Precision Curve Storage Standard Response Curves DT 400 Series Silicon Diodes DT 500 Series Silicon Diodes PT 100 Series Platinum RTDs Thermocouples SoftCal Control Control Type Automatic Control Mode Manual Control Mode Control Stability Setpoint Resolution Control Sensor Selection Ramp Rate Zones Heater Output Type Heater Setting Resolution Max Power To Heater Heater Current by Range Heater Output Compliance Heater Load for Full Power Minimum Heater Load
28. Medium 3 Heater High Use the TUNE command to activate the zone autotuning mode ZONE 1 100 0 2 100 0 100 20 term instructs the Model 330 to store in Zone 1 a 100 0 K setpoint a 2 Medium Heater Range a 100 Gain a 100 Reset and a 20 Rate Zone Storage Query ZONE XX SSS S R PPP III DDD When entering the zone command XX defines the zone between 01 and 10 Returns SSS S setpoint in kelvin R heater range PPP gain Ill Reset DDD Rate For Heater Range 0 Heater off 1 Heater Low 2 Heater Medium 3 Heater High Use TUNE command to activate zone autotuning mode Remote Operation Lake Shore Model 330 Autotuning Temperature Controller User s Manual 4 3 6 Curve Commands Curve Commands allow users to verify existing factory added curves or enter or delete user defined curves over the interface ACOMP Input Returned Remarks ACOMP Input Returned Remarks ACUR Input Returned Remarks ACUR Input Returned Remarks ATYPE Input Returned Remarks BCOMP Input Returned Remarks BCOMP Input Returned Remarks BCUR Input Returned Remarks Remote Operation Set Room Temperature Compensation for Channel A ACOMP 00r ACOMP 1 Nothing Effective only with the Model 330 4X Thermocouple Version Select temperature compensation parameter 0 off 1 on Room Temperature Compensation for Channel A Query ACOMP Dor L Effective only
29. Model 330 Autotuning Temperature Controller User s Manual 5 8 ERROR MESSAGES On power up the Model 330 checks internal memory There are two potential error messages The first error Er01 indicates an unsuccessful attempt to write and then read the internal non volatile RAM This error is not user correctable Consult the factory The second error Er02 indicates an unsuccessful attempt to read the internal non volatile RAM for the Model ID Sometimes initializing memory corrects this error To initialize memory press and hold both Escape and Units for about 20 seconds Release when the power up sequence begins Perform this operation only under extreme circumstances it erases any user defined curves in memory There are two sensor input error messages If an input signal from the sensor exceeding full scale is applied to the input leads OL indicates the overload If no signal or a wrong polarity signal exists at the input leads Er27 indicates a Zero Error for Channel A or Er28 for Channel B The Model 330 displays dashes if the input switches are improperly set Finally Er30 appears if the measured heater output does not match the predicted output The controller turns the heater off Check heater resistance test for shorts in the heater wiring then turn the heater on again If the error message returns consult the factory Table 5 1 Sensor Input Setup Display When DIP Switch aen Type Input Standard Settings Key is
30. States of America It is a microprocessor based instrument with digital control of a variable current output Features include Four Primary Sensor Configurations can be ordered in any combination Silicon Diode Model 330 1X Platinum Resistor 100 Q Model 330 2 GaAlAs Diode Model 330 3X Thermocouple Model 330 4X Thermometry Dual Sensor Inputs Isolated current sources allow true 4 wire sensor readings Isolated digital and analog power supplies improve sensor readings and quiet heater output Nonvolatile Memory Space store up to 21 sensor calibration curves SoftCal improves system accuracy with simple one to three point calibrations by user Five Tuning Modes Autotuning P Autotuning PI Autotuning PID Manual Zone Ten Temperature Zones Control Control Stability to 2 5 mK Three Term PID Control Loop 25or 50 Watt Maximum with 2 lower power ranges in decade steps Setpoint Ramping Interface 4 5 Digit LED Display for High Visibility Dual Display of Sensor Temperature in K C or sensor units in volts ohms Setpoint Display Continuous Display of Heater Output in 596 increments of the heater range selected EEE 488 and Serial Interface RS 232C Electrical Format We welcome comments concerning this manual Although we try to keep it free from errors some may occur When reporting specific problems describe it briefly and include the applicable
31. and I together and the negative terminals V 5 va and I together at the instrument then run two leads to the sensor TuS Leag 2 Expect some loss in accuracy since the voltage measured at the ES y instrument equals the sum of the sensor voltage and the voltage drop LL across the connecting leads The exact measurement error depends on sensor sensitivity and variations resulting from changing temperature For example a 10 Q lead resistance results in a 0 1 mV voltage error The resultant temperature error at liquid helium temperature is only 3 mK but because of the diode s lower sensitivity d V dT at higher temperatures it becomes 50 mK at liquid nitrogen temperature Four Lead Measurements All sensors both two lead and four lead devices may be measured in a four lead configuration to eliminate the Pici effects of lead resistance The exact point at which the Diode Platinum connecting leads are soldered to the two lead sensor 2 y 2 y normally results in a negligible temperature uncertainty t Always use four lead measurement with Series PT 100 Platinum Sensors attached to the Model 330 2X 2 4 Installation Lake Shore Model 330 Autotuning Temperature Controller User s Manual 2 6 1 2 Heat Sinking Sensor Leads Excessive heat flow through connecting leads to any temperature sensor puts the active sensing element is at a different temperature than the sample to which the sensor mounts This yields a
32. drawing for details If the device is to be used only below 325 K apply a layer of Apiezon N Grease between the SD package and mounting surface to enhance thermal contact 5 3 mm Me 32 mm EAT 2 2 mm 8 9 mm Sch 7 o Sensor d Beryllium 7 6 mm Oxide Heat Sink Chip 2 95 mm diameter for 4 40 machine Cathode B amp ANTE 314 40 shoulder screw extends 6 9 mm above clamp SD Sensor A Cathode re Anode Application Notes Lake Shore Model 330 Autotuning Temperature Controller User s Manual Current Source Sensor V FIGURE 1 Four Wire Configuration for DT 470 Installation SENSOR OPERATION Temperature controllers and thermometer instrumentation manufactured by Lake Shore Cryotronics are designed to be directly compatible with the DT 470 sensor to give optimum performance and accuracy together with direct temperature readouts Simply follow the instructions provided with the instrument concerning sensor connection and instrument operation If a user supplied current source voltmeter or other instrumentation are going to used with the DT 470 sensor special attention should be given to the following details The DT 470 is designed to operate at a constant current of 10 microamperes while the voltage variation with temperature is monitored Therefore the accuracy of the temperature measurement depends directly onf the specifications of the current source and the
33. for a sample BASIC program to establish communications between the computer and the Model 330 The Serial Interface shares Device Specific commands with the IEEE 488 interface listed in Paragraph 4 3 However without the advantage of the IEEE 488 Architecture there are several limitations No Bus Control Commands apply Only xIDN and RST Common Commands are usable Terminators are fixed to CRLF Aquery must be added to the end of a command string if the Model 330 must return information Over IEEE 488 the last query response is sent when addressed to talk The maximum buffer input is 256 characters which limits the length of chained commands The interface recognizes no new commands when processing a previous command Place a delay of 0 5 second between consecutive commands LSCI Model 2002 RJ 11 to DB 25 SERIAL UO To customer supplied Adapter computer with DB 25 Serial Interface Serial Interface Output on rear of Connector configured as Model 330 DCE If the interface is 1 DTE a Null Modem Adapter is required to CT exchange Transmit and 1 The Model 2001 2002 and 2003 Receive lines are options available from Lake Shore Use whichever adapter that matches your computer serial interface connector Pin outs are described in Paragraph 5 6 LSCI Model 2003 RJ 11 To customer supplied to DE 9 Adapter computer with DE 9 Serial Interface LSCI Model 2001 RJ 11 Cable Assembly Conne
34. format Resolution is 0 01 for temperatures below 200 Ifin kelvin 1 SETP 77 2 term will result in the display showing 77 20 K 2 SETP 123 term will result in the display showing 123 00 K If in Celsius 3 SETP 123 term will result in the display showing 123 00 C 4 SETP 123 456 term will result in the display showing 123 46 C Setpoint Status Query SETP XXX X for temperature or x Xxxx for voltage Returns current set point setting a 7 digit value a sign 5 digits and a decimal point Resolution is 0 01 for temperatures below 200 Using the examples above in the SETP command discussion If in kelvin 1 SETP term returns 077 20 term 2 SETP term returns 123 00 term If in Celsius 3 SETP term returns 123 00 term 4 SETP term returns 123 45 term Sets Autotuning Status TUNE X Nothing Sets Autotuning status 0 Manual 1 P 2 PI 3 PID 4 Zone See Paragraph 3 3 4 for details on Autotuning settings Autotuning Query TUNE X Returns current Autotuning status 0 Manual 1 P 2 PI 3 PID 4 Zone See Paragraph 3 3 4 for details on Autotuning settings Zone Storage ZONE XX 4SSS S R PPP III DDD Nothing Stores the stated values of Setpoint Heater Range Gain Rate and Reset Zone XX is between 01 and 10 SSS S setpoint in kelvin R heater range PPP gain IIl Reset DDD Rate For Heater Range 0 Heater off 1 Heater Low 2 Heater
35. from a thermo couple voltage sum it with 15 millivolts to make it positive and multiply it by 100 to shift the resolution A 15 0000 millivolt thermocouple voltage results in a 0 00000 volt table value and 15 0000 millivolts results in 3 00000 volts Operation 3 15 3 16 Lake Shore Model 330 Autotuning Temperature Controller User s Manual This Page Intentionally Left Blank Operation Lake Shore Model 330 Autotuning Temperature Controller User s Manual CHAPTER 4 REMOTE OPERATION 4 0 GENERAL Either of the two computer interfaces provided with the Model 330 permit remote operation The first is the IEEE 488 Interface Paragraph 4 1 The second is the Serial Interface Paragraph 4 2 The two interfaces share a common set of commands Paragraph 4 3 Use only one of the interfaces at a time See Paragraph 4 4 for a Serial Interface curve loading program 4 1 IEEE 488 INTERFACE The IEEE 488 Interface is an instrumentation bus with hardware and programming standards that simplify instrument interfacing The Model 330 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 All 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
36. good thermal contact to the mounting surface is maintained B 10 Application Notes Lake Shore Model 330 Autotuning Temperature Controller User s Manual DT 470 SD The SD version is the basic package for the DT 470 sensor line from which all 2 16 mm other configurations are made using the appropriate adapter The base of the 0 98 mm lt 1 4 mm device has a gold metallized surface and is the largest flat surface on the Anode sensor The base is electrically isolated from the sensing element and leads 1 84 mm and all thermal contact to the sensor must be made through the base A thin lH braze joint around the sides of the SD package is electrically connected to the ke Cathode sensing element Contact to the sides with any electrically conductive material 3 mm must be avoided When viewed with the base down and with leads towards the observer the positive lead anode is on the right For a removable mount the Sd sensor can be3 held against the mounting surface with the CO adapter see below or similar clamping mechanism Any method of clamping the sensor must avoid excessive pressure and should be designed so that thermal contractions or expansions do not loosen contact with the sensor For uses restricted to below 325 K a thin layer of Apiezon N Grease should be used between the sensor and sample to enhance the thermal contact The SD package can also be bonded with an epoxy such as Stycast The sensor should be pressed f
37. o Type Input Standard Settings Key is Pressed Range Curve s Go Oo a Silicon Diode re Kee SEN Volts 0 to 2 5 7 e 2 4 Curve 10 SoftCal Lr SE KEE Oh 0 to 300 3 DIN C 43760 RTD SCC SCC R ms o urve Lr 3 Ge P olts o 6 Co O D Thermocouple lt T A l l 6 AuFe 0 0796 vs Chromel compensation Millivolts 10 to 10 pe i i 17 AuFe 0 03 vs Chromel E _ 8 Type E chromel constantan o o Thermocouple lt l l 9 Type K chromel alumel compensation Sall lr Millivolts 15 to 15 off E i i 10 Type T copper constantan If the internal DIP switches are improperly set the display will read Er when the Input Type key is pressed The normal front panel display will show dashes to indicate improper DIP switch setting DIP Switch S1 is for Channel A and S2 is for Channel B 2 5 GROUNDING AND SHIELDING To protect operating personnel the National Electrical Manufacturer s Association NEMA recommends and some local codes require grounded instrument panels and cabinets This instrument comes with a three conductor power cable which grounds the instrument when plugged into an appropriate receptacle Grounding and shielding signal lines are major setup concerns The Model 330 allows 4 wire measurement of diode voltage and resistance To prevent inaccuracy isolate diode and resistive sensor leads from earth ground However thermocouple sensors may be grounded Shield sens
38. over the serial interface Paragraph 4 4 or buy a factory installed Precision Calibration Option Curve from Lake Shore SoftCal Curve SoftCal curves store in curve location numbers 11 thru 31 as a User Curve See Table 2 3 and Paragraph 3 2 7 to use SoftCal 2 8 PRECISION CALIBRATION OPTION There are three Model 330 precision options The Model 8000 Precision Calibration Option generates the data table from a Lake Shore calibrated sensor The maximum number of data points is 99 but a typical precision calibration option ranges between 30 and 40 points depending on the sensor type and temperature range of the calibration Lake Shore supplies data and accuracy of the fit which the user may enter over the Serial or IEEE 488 Interface Prior to shipment Lake Shore can also generate a custom sensor response curve from the individual sensor calibration and store it in the Model 330 via the Model 8001 Precision Calibration Option The Model 8001 is factory installed when you order an instrument with a calibrated sensor To order an instrument to be used with an existing Lake Shore calibrated sensor supply Lake Shore with the sensor model and serial number at the time of order The Model 8002 05 is for field installations of the Precision Calibration Option in an existing Model 330 Lake Shore stores the calibration data ina NOVRAM and sends the programmed IC to the customer The IC is then installed in the instrument by the customer The user must s
39. paragraph figure table and page number Send comments to Lake Shore Cryotronics Attn Technical Publications 575 McCorkle Blvd Westerville Ohio 43082 8888 This manual is subject to change without notice Due to our commitment to continuous product improvement we may modify the Model 330 software with time Some changes result from Customer feedback regarding operation on various cryogenic systems Please contact us with any observations or suggestions regarding the use of this controller Also please return warranty card to ensure receipt of software updates Introduction 1 1 Lake Shore Model 330 Autotuning Temperature Controller User s Manual 1 4 MODEL 330 TEMPERATURE CONTROLLER DESCRIPTION The Model 330 is a microcontroller based Autotuning temperature controller There are four primary sensor input types the Model 330 1X for Silicon Diode Temperature Sensors the Model 330 2X for Platinum Resistors the Model 330 3X for Gallium Aluminum Arsenide Diodes and the Model 330 4X for Thermocouples The Model 330 accommodates these commonly used cryogenic temperature sensors in any combination thermocouples optional They are field selectable without calibration except for thermocouples which are factory installed when ordered The Model 330 bright red dual LED display shows data from both sensors or one sensor and the setpoint It displays temperature in K C or sensor units in volts V millivolts mV or ohms Q Heater ou
40. size of the capacitor needed will depend on the frequency of the noise generally related to the power line frequency of 60 Hz and the dynamic impedance of the diode on the order of a few thousand ohms at a 10 pA operating current A capacitor in the range of 10 to 20 uF should reduce most noise effects to an acceptable level However because the capacitor increases the time constant in the circuit a sluggish response should be expected In switching operations 30 seconds or more may be required for the circuit to stabilize This quick fix is not meant as a substitute for proper measurement techniques but in certain circumstances it may be useful Note added in proof The capacitance values given above are for the elimination of the effects of low frequency noise such as 60 Hz If high frequency noise is a problem an additional capacitor of lower capacitance value may be needed The reason for this is because larger capacitors often have an associated inductance which limits their usefulness as a high frequency shunt 1 A S Grove Physics and Technology of Semiconductor Devices Wiley New York 1967 Chap 6 S M Sze Physics of Semiconductor Devices Wiley Interscience New York 1969 Chap 4 3 D A Fraser The Physics of Semiconductor Devices Clarendon Oxford 1983 4 R V Aldridge Solid State Electron 17 617 1974 V Chopra and G Dharmadurai Cryogenics 20 659 1980 D A Kleinman Bell Syst Tech J 35 685 1
41. system checkout procedure in Paragraph 2 12 Service amp Calibration 5 1 Lake Shore Model 330 Autotuning Temperature Controller User s Manual 5 3 REAR PANEL CONNECTOR DEFINITIONS Figures 5 2 thru 5 4 define Serial UO Analog Output Sensor input and Heater Output connectors SERIAL mm RS 232C In RxD RS 232C In RxD RS 232C Ground RS 232C Ground RS 232C Out TxD RS 232C Out TxD 123 4 Figure 5 2 SERIAL I O RJ 11 Rear Panel Connector Details CHANNELA CHANNEL B MW Wr PIN Symbol DESCRIPTION 1 I Current V Voltage resistor Current 1 mA Platinum V Voltage diode Current 10 pA Diodes none Shield Figure 5 3 Sensor CHANNEL A and B Rear Panel Connector Details HEATER OUTPUT HI LO GND PIN DESCRIPTION 1 HI 2 Lo 3 GROUND Figure 5 4 HEATER OUTPUT Rear Panel Connector Details 5 2 Service amp Calibration Lake Shore Model 330 Autotuning Temperature Controller User s Manual 5 4 IEEE 488 INTERFACE CONNECTOR Connect to the IEEE 488 Interface connector on the Model 330 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 al
42. temperature offset between what is measured and the true sample temperature To eliminate such temperature errors select and install connecting leads properly To minimize any heat flow through the leads use leads of small diameter and low thermal conductivity Phosphor bronze or Manganin wire is commonly used in sizes 32 or 36 AWG Though these wires have fairly low thermal conductivity the electrical resistance is not large enough to create problems in measurements Thermally anchor lead wires at several temperatures between room temperature and cryogenic temperatures to guarantee minimal heat conductivity through the leads to the sensor 2 6 1 3 Sensor Mounting Before installing a diode sensor identify the anode and the cathode f DT 470 SD When viewed with the base down and with the leads towards the Diode Sensor Leads observer the positive lead anode is on the right and the negative lead cathode is on the left The figure to the right shows the Lake Shore DT 470 SD silicon diode sensor lead configuration For other sensors read the accompanying literature or consult the manufacturer to ensure positive identification of sensor leads Be sure the lead identification remains clear even after installation Record the sensor serial number and location Cathode wem Anode On the DT 470 SD the base is the largest flat surface It is sapphire with gold metallization over a nickel buffer layer The base is electrically isolat
43. the primary address forms the Listen Address LA Adding 64 to the primary address forms the Talk Address TA EXAMPLE Selecting a primary address of 10 yields the following 10 32 42 Listen address 10 64 74 Talk address L Esc Return to Map Ctl PgUp PgDn Next Prev Board Figure 4 1 Typical National Instruments GPIB Configuration from IBCONF EXE Remote Operation Lake Shore Model 330 Autotuning Temperature Controller User s Manual 4 2 SERIAL UO INTERFACE RS 232C is a standard of the Electronics Industries Association EIA and one of the most common interfaces between a computer and electronic equipment The Customer supplied computer must have a Serial Interface port The Model 330 Serial Interface complies with the electrical format of the RS 232C Interface Standard A Serial Interface between the computer and the Model 330 permits remote monitoring and control of Model 330 control functions which in turn controls Model 330 operation See Figure 4 2 The Serial Interface can both transmit and receive information In transmit Tx mode the instrument converts parallel information to serial and sends it over a cable up to 50 feet long or longer with proper shielding In receive Rx mode the instrument converts serial information back to parallel for processing See Paragraph 4 2 1 for Serial Interface hardware configuration and adapters Paragraph 4 2 2 for Serial Interface settings and Paragraph 4 2 3
44. with the Model 330 4X Thermocouple Version Returns current room temperature compensation status 0 off 1 on Assign Curve Number for Channel A ACUR XX Nothing Enter integer from 0 through 31 for Channel A Table 3 1 lists sensor curve numbers Curve Number for Channel A Query ACUR Xx an integer from 00 to 31 Returns the currently selected sensor curve number for Channel A Table 3 1 lists sensor curve numbers Channel A Input Type Query ATYPE SI PT AS TC Or ER Returns input type for Channel A SI silicon diode PT platinum AS GaAlAs TC thermocouple ER error improper switch setting Set Room Temperature Compensation for Channel B BCOMP 0 or BCOMP 1 Nothing Effective only with the Model 330 4X Thermocouple Version Select temperature compensation parameter 0 off 1 on Room Temperature Compensation for Channel B Query BCOMP oor1 Effective only with the Model 330 4X Thermocouple Version Returns current room temperature compensation status 0 off 1 on Assign Curve Number for Channel B BCUR XX Nothing Enter an integer from 0 through 31 for Channel B Table 3 1 lists sensor curve numbers 4 19 BCUR Input Returned Remarks BTYPE Input Returned Remarks CUID Input Returned Remarks Example Lake Shore Model 330 Autotuning Temperature Controller User s Manual Curve Number for Channel B Query BCUR XxX an integer from 00 to 31
45. 0 15015 1 00460 1 02840 0 94455 0 19223 1 04070 1 07460 0 98574 0 23525 1 07460 1 08480 1 02044 0 32081 1 09020 1 09090 1 05277 0 46648 1 09700 1 09810 1 08105 0 62980 1 10580 1 10800 1 09477 0 75044 1 11160 1 11500 1 10465 0 98784 1 11900 1 12390 1 11202 1 16270 1 13080 1 13650 1 11517 1 31616 1 14860 1 15590 1 11896 1 48652 1 17200 1 18770 1 12463 1 65466 1 25070 1 23570 1 13598 1 82035 1 35050 1 33170 1 21555 1 98386 1 63590 1 65270 1 29340 2 16256 1 76100 1 96320 1 36687 2 32106 1 90660 2 17840 1 44850 2 47712 2 11720 2 53640 1 64112 2 61391 2 53660 2 59940 1 68912 2 76566 2 59840 2 65910 1 69808 2 89830 6 55360 6 55360 6 55360 6 55360 OO JO Om P h A Appendix A A 1 Lake Shore Model 330 Autotuning Temperature Controller User s Manual Table A 2 Thermocouple Curves Chromel versus Gold Iron Breakpoint Chromel vs Au 0 03 at Fe Chromel vs Au 0 07 at Fe Number Temp K Vrc mV Temp K Vrc mV 15 0000 15 0000 4 6676 5 2982 4 6067 S 5 2815 4 5259 5 2594 4 4571 5 2285 4 3703 5 1742 4 2869 5 0315 3 9928 4 9126 3 8830 4 5494 3 8126 4 3810 8 7411 s 4 1733 3 5948 f 3 9952 3 4436 3 8132 3 2026 3 6270 3 0374 3 4370 2 8689 3 2435 2 6957 2 9477 2 5184 2 6452 2 2468 2 3372 2 0615 2 0242 1 8725 1 6004 1 5839 1
46. 0 193093 A 5 0 723026 A 5 0 393265 A 6 0 020715 A 6 0 155717 A 6 0 149503 A 6 0 146911 A 7 0 014814 A 7 0 085185 A 7 0 046876 A 7 0 111192 A 8 0 008789 A 8 0 078550 A 8 0 388555 A 8 0 028877 A 9 0 008554 A 9 0 018312 A 9 0 056889 A 9 0 029286 A 10 0 039255 A 10 0 116823 A 10 0 015619 A 11 0 058580 Application Notes B 9 Lake Shore Model 330 Autotuning Temperature Controller User s Manual DT 470 SERIES TEMPERATURE SENSORS INSTALLATION AND OPERATION There are three aspects of using a temperature sensor which are critical to its optimum performance The first involves the proper electrical and thermal installation of the connecting leads which run to the sensor while the second aspect is the actual mounting of the sensor to the sample assembly The final concern is the measurement electronics used for reading and recording temperature data from the sensor CONNECTING LEADS Although the majority of the DT 470 series sensors are two lead devices measurements should preferably be made using a four wire configuration to avoid all uncertainties associated with the lead resistance This is done by using four connecting leads to the device and connecting the V and I leads to the anode and the V and l leads to the cathode as shown in Figure 1 The exact point at which the connecting leads are soldered to the device leads results in negligible temperature measurement uncertainties
47. 0 listed in Table 2 3 see Paragraph 3 2 6 3 5 3 Thermocouple Compensation From Front Panel To determine whether thermocouple compensation is selected or not see Paragraph 3 2 4 3 5 4 Thermocouple Compensation From Remote Interface To select or prevent thermocouple compensation over the remote interface use the ACOMP command see Chapter 4 3 5 5 Internal Offset Adjustment NOTE The offset adjustment compensates for the thermocouple used in calibration If another thermocouple is attached or the thermocouple has aged or system configuration is changed then repeat the offset adjustment When a new or different thermocouple is attached to the controller adjust the offset to compensate for discrepancies in thermocouple material leads and connections Offset adjustment trimpots are provided inside the Model 330 to allow offset calibration of the thermocouple See Paragraph 5 12 3 5 06 Curve Format The input is hardware limited to reading input between 15 mV and 15 mV Limit all curves in temperature so not to exceed these values For thermocouple compensation normalize the thermocouple curve to zero in degrees Celsius Compensation also limits the practical card range by approximately the room temperature voltage of the thermocouple The Model 330 operates on sensor curve data ranging from 0 00000 to 3 00000 volts Convert thermocouple voltage to this range before entering it into a curve table To obtain the proper table value
48. 0 thru 10 cannot be edited If the Model 330 does not recognize either the units value or the temperature value it assumes you are entering a new point and places it in the proper ascending position If the point to be edited was input as 0 19083 364 0 and should have been 0 19083 365 0 input this command ECUR 11 0 19083 365 0 term The Model 330 recognizes the units field and replaces that data point with the new temperature value Curve Bytes Free Query FREE XXXX value from 0000 to 3584 Returns the number of curve storage bytes available for new curve entry New curves require at least 100 bytes free A typical 31 point curve requires 176 bytes Delete User Curve Data Command KCUR XX Nothing Deletes all data stored for the User Curve where XX user curve number 11 thru 31 Curves 00 thru 10 cannot be deleted Repacks the remaining curves within the NOVRAM SoftCal Voltage Entry SCAL AA X XXXXX Y YYYYY Z Z4ZZZ7Z Nothing Stores the SoftCal voltage values at 4 2 K 77 32 K and 300 K where AA Curve number from 11 to 31 X XXXX 4 2 K voltage Y YYYYY 77 32 K voltage and Z ZZZZZ 300 K voltage SCAL 12 1 6260 1 0205 0 5189 term Remote Operation Lake Shore Model 330 Autotuning Temperature Controller User s Manual 4 4 USER CURVE LOADING PROGRAM To simplify the loading of a user curve using the Serial Interface the following curve loading program is provided The program will work with QuickBASIC V4 0 4 5 o
49. 1 Thermocouple Silicon Diode 330 42 Thermocouple Platinum Resistor 330 43 Thermocouple GaAlAs Diode 330 44 Thermocouple Thermocouple 330 51 Thermocouple Platinum Resistor 330 53 Thermocouple GaAlAs Diode 330 55 Thermocouple Thermocouple Use the model numbers above to specify input type eg 330 12 for a Model 330 with one Silicon Diode input and one Platinum input The standard 330 heater output is 25 watts Add a suffix of W50 to the order number for a unit factory configured for 50 watts operation or the user can do so by moving a jumper within the unit 6 2 OPTIONS MODEL NUMBER DESCRIPTION OF MODEL 330 OPTIONS 8000 Precision Option Floppy Disk Consists of breakpoint pairs from a Sensor Precision Calibration loaded on a floppy disk in ASCII format for Customer downloading 8001 Precision Option Factory Installed Provides custom factory programming of a specific sensor calibration curve The Precision Option improves combined sensor instrument accuracy to within 0 1 K or better over the calibrated temperature range of the sensor Data is stored ina memory chip NOVRAM Requires the use of a calibrated sensor Precision Option Field Installation For field installation of the precision option for Model 330 owners When ordering specify your instrument serial number and calibrated sensor model and serial number Anew NOVRAM will be sent for Customer installation Options and Accessories 6 1 Lake Shore Model 330 Autotuning T
50. 10 T 42K loc 10 UA 10 3 gt 10 4 2 e 2 A e A 60 Hz 10 1kHz 20 kHz 1 0 4 8 12 16 20 24 28 32 RMS AC VOLTAGE mV FIGURE 7 DC offset voltage as a function of rms ac voltage across a silicon diode temperature sensor operating at 77 K The symbols represent data recorded at a 10 UA dc current with the ac current modulation at 60 1000 and 20 000 Hz Lake Shore Model 330 Autotuning Temperature Controller User s Manual IV CONCLUDING REMARKS Noise in any measurement circuit is undesirable and should be eliminated to as great an extent as possible The first step is to electrically shield all instrumentation and wiring and use proper grounding techniques Secondly the diode measurement circuit should have a single circuit ground which is generally made at the voltmeter and which then requires a floating current source The installation of the diode and its connecting leads should be done carefully to avoid introducing any unwanted circuit ground connections such as an electrical short to a cryostat As a last resort a quick fix can be used to eliminate much of the dc offset voltage with some degradation in the diode circuit performance A good quality capacitor low leakage can be placed across the diode to shunt the induced ac currents similar to the test procedure used for identifying a noise problem This is most easily done by connecting the capacitor across the input to the voltmeter The
51. 1693 1 2905 0 6232 0 9912 0 0705 0 6847 0 5986 0 1670 0 7158 0 0378 0 8431 0 2387 0 9944 0 6350 1 1940 1 0387 1 4841 15 0010 15 0010 OANDABRWN Table A 3 Thermocouple Curves Chromel versus Copper Breakpoint Chromel vs Constantan Chromel vs Alumel Copper vs Constantan Number E Vre mV K Vre mV T Vre mV 15 0000 15 0000 15 0000 9 8355 6 4582 6 2584 9 8298 6 4551 6 2523 9 8182 6 4486 6 2401 9 7956 6 4376 6 2184 9 7570 6 4205 6 1888 9 7013 6 3951 6 1404 9 6204 6 3529 6 0615 9 5071 6 2913 5 9535 9 3366 6 2149 5 7995 9 1345 6 1022 5 5753 8 9030 6 0099 5 3204 8 6475 5 8634 5 0337 8 3673 5 6989 4 7194 7 9064 5 5156 4 3767 7 3943 5 3166 3 8781 6 8386 4 9881 3 3278 6 2400 4 6240 2 7342 5 3831 4 2267 A 1 9295 4 4564 3 7994 1 0586 3 4702 3 1866 0 1254 2 1605 2 5259 1 0616 0 7666 1 6463 2 3247 0 9948 3 0 5186 i 3 6639 2 8428 0 8688 5 3095 4 7704 3 1298 7 0419 7 1149 4 9999 9 1113 9 5570 7 6164 11 2758 12 4425 9 6125 13 8053 13 5573 i 12 2790 f 14 9685 15 0010 15 0010 15 0010 2 o 00 100 bo SSSSSSONAOWLNS OOoooo
52. 2 Common see Paragraph 4 1 2 2 3 Interface and Device Specific see Paragraph 4 1 2 3 Remote Operation 4 1 Lake Shore Model 330 Autotuning Temperature Controller User s Manual 4 1 2 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 330 recognizes two of these messages from the BUS CONTROLLER Remote REN and Interface Clear IFC The MPS sends one Uniline Command Service Request SRQ REN Remote Puts the Model 330 into remote mode IFC Interface Clear Stops current operation on the bus SRQ Service Request Tells the bus controller that the Model 330 needs interface service 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 330 recognizes two Multiline commands LLO Local Lockout Prevents the use of instrument front panel controls DCL Device Clear Clears Model 330 interface activity and puts it into a bus idle state Finally Addressed Bus Control Commands are Multiline commands that must include the Model 330 listen address before the instrument responds Only the addressed device responds to these commands The Model 330 recognizes three of the Addressed Bus Contro
53. 2 Setpoint and Control To change the setpoint press the Setpoint key If the lower display already shows setpoint it blinks and the instrument is ready for a new setpoint value If the lower display indicates the control reading it displays the current setpoint Press Setpoint again to enter a new setpoint Enter the new setpoint with the numbered keys and decimal point in the center of the keypad Press Enter to complete the operation or Escape to cancel and retain the previous value Also use either A or v to increment or decrement the display by one degree The setpoint on the Model 330 is limited to a resolution of 0 01 for temperatures below 200 and 0 1 for temperatures greater than 200 Any decimal digits entered after the 100 place are ignored If the setpoint is displayed in degrees Celsius or millivolts the key toggles the sign of the set point The setpoint is limited in temperature to the range of the curve used for control Table 3 1 gives these limitations in kelvin for curves 00 through 04 and 06 thru 10 The Control key quickly returns the bottom from displaying the setpoint to the Control sensor reading 3 8 Operation Lake Shore Model 330 Autotuning Temperature Controller User s Manual 3 3 2 1 Voltage Resolution Models 330 1X 3X and 4X Only Use voltage mode for diode input In voltage mode the display resolution is 0 0001 Volt V below 2 volts For thermocouple input the display is in millivolts The mi
54. 3 4 and Thermocouple Controller Operation Model 330 04 only Paragraph 3 5 3 1 DEFINITION OF FRONT PANEL CONTROLS The front panel consists of two major sections 20 front panel keys Paragraph 3 1 1 and a 2 row by 16 character LCD Paragraph 3 1 2 3 1 1 Front Panel Keypad Definitions Below are abbreviated descriptions of each front panel key See subsequent paragraphs for more detailed descriptions of each function 330 Autotuning Temperature Controller Heater Baud Address Escape Input Curve 4 Control Control Enter D 330 U 1 1 Figure 3 1 Model 330 Front Panel Units Sets the controller to display temperature units in kelvin K or Celsius C or sensor units in volts V millivolts mV or ohms Q depending on Model number See Paragraph 3 2 3 Baud Selects a Baud Rate of 300 or 1200 for Serial Interface See Paragraph 3 4 1 Address Selects the bus address and terminator for IEEE 488 Interface See Paragraph 3 4 2 Channel Assigns channel sensor to use for Sample and Control See Paragraph 3 2 2 Input Type Only displays the currently selected sensor input type Paragraph 3 2 1 To change sensor input see Paragraph 5 9 This key also controls Display Filter Paragraph 3 2 4 and Thermocouple Temperature Compensation Paragraph 3 2 5 Curve Selects the Channel A and B sensor response curve See Paragraph 3 2 6 P Manually adjusts control loop gain Proportional term See Paragraph 3 3 5 1
55. 4HS calibration with 1 4L calibration 1 4 475 K LSCI Curve 10 30 mV K at 4 2 K 1 9 mV K at 77 K 2 4 mV K at 300 K 2 2 mV K at 475 K Measurement Resolution Sensor Units Temperature Equivalence Sensor Units Display Resolution Measurement Accuracy Temperature Accuracy with 0 04 mV 1 3 mK at 4 2 K 21 mK at 77 K 16 mK at 300 K 18 mK at 475 K 0 1 mV to 1 mV 125 uV 0 015 RDG 50 mK at 4 2 K 120 mK at 77 K Calibrated Sensor and 8001 Precision Option Measurement Temperature Coefficient Sensor Units 0 002 RDG C Ambient Control Stability 2 5 mK at 4 2 K 25 mK at 77 K 25 mK at 300 K Thermocouple data is for uncompensated inputs T Sensor calibration and 8001 Precision Option are not available for thermocouples The error listed is for the instrument only 30 800 K DIN 43760 0 19 Q K at 30 K 0 42 O K at 77 K 0 39 Q K at 300 K 0 33 Q K at 800 K 5mQ 26 mK at 30 K 12 mK at 77 K 13 mK at 300 K 15 mK at 800 K 0 01 Q to 0 1 Q 12 m Q 0 04 RDG 45 mK at 30K 62 mK at 77K 80 mK at 300 K 75 mK at 475 K 0 004 15 mK at 30 K 15 mK at 77 K 15 mK at 300 K 25 mK at 800 K TG 120P with 14J calibration 1 4 325 K Needs Calibration and 8001 Precision Option Ch AuFe 0 07 1 4 325 K NBS NIST generated 180 mV K at 4 2K 16 uV K at 4 2 K 1 25 mV K at 77 K 20 uV K at 300 K 2 75 mV K at 300 K 0 09 mV 0 5 mK at 4 2
56. 65 170 Part 4 Reset and Rate Control October 1984 pp 133 145 Part 5 Selecting the Mode of Control December 1984 pp 132 136 Some of this material has appeared in Principles of Temperature Control available from Gulton Industries West Division Unlike reference 1 the discussion is not related to cryogenics but temperature control system principles are briefly and clearly explained C L Pomernacki Micro Computer Based Controller for Temperature Programming the Direct Inlet Probe of a High Resolution Mass Spectrometer Review of Scientific Instruments 48 1977 pp 1420 1427 W M Cash E E Stansbury C F Moore and C R Brooks Application of a Digital Computer to Data Acquisition and Shield Temperature Control of a High Temperature Adiabatic Calorimeter Review of Scientific Instruments 52 1981 pp 895 901 R B Strem B K Das and S C Greer Digital Temperature Control and Measurement System Review of Scientific Instruments 52 1981 pp 1705 1708 Application Notes B 7 Lake Shore Model 330 Autotuning Temperature Controller User s Manual STANDARD CURVE 10 Standard Curve 10 Measurement Current 10 pA 0 05 dV dT dV dT dV dT T K Voltage mV K T K Voltage mV K T K Voltage mVIK 1 69812 1 69521 1 69177 1 68786 1 68352 1 67880 1 67376 1 66845 1 66292 1 65721 1 65134 1 64529 1 63905 1 63263 1 62602 1 61920 1 61220 1 60506 1 59782 1 57928 1 56027 1 54097 1
57. 7772 004 4 4 829 63 003 1 5 03503 002 1 5 12385 001 6 5 15376 001 4 Sample ACSII File No 2 Typical Silicon Diode Sensor Format S00DT 470CU D46254 0 37198 300 0 0 44204 275 0 0 54863 235 0 0 61840 210 0 0 7322 9 170 0 0 84333 130 0 0 95137 090 0 1 00351 070 0 1 04031 055 0 1 07506 040 0 1 0 8564 036 0 1 09194 034 0 1 09964 032 0 1 11028 030 0 1 11764 029 0 1 12731 028 0 1 14093 027 0 1 16147 026 0 1 19192 025 0 1 23370 024 0 1 28745 023 0 1 43452 021 0 1 68003 018 0 1 91882 014 0 2 09621 010 0 2 32759 006 5 2 54962 003 6 2 62794 002 0 2 64172 001 4 Remote Operation 4 25 Lake Shore Model 330 Autotuning Temperature Controller User s Manual This Page Intentionally Left Blank 4 26 Remote Operation Lake Shore Model 330 Autotuning Temperature Controller User s Manual CHAPTER 5 SERVICE AND CALIBRATION 5 0 GENERAL This chapter covers several aspects of Model 330 service and calibration General Maintenance Precautions Paragraph 5 1 Electrostatic Discharge Paragraph 5 2 General Maintenance Information Paragraph 5 3 Changing Power Settings and Fuse Rating Paragraph 5 4 Rear Panel Connector Definitions Paragraph 5 5 Optional Serial Cable and Adapters Paragraph 5 6 Software EPROM and Precision Option NOVRAM Replacement Paragraph 5 7 Power Up and Sensor Error Messages Paragraph 5 8 Changing Sensor Input Type Paragraph 5 9 Calibration Paragraph 5 10 Thermocouple Calibration Paragraph 5 11 and Thermocouple Inte
58. 956 P R Swinehart L A Smith and J K Krause private communication values are consistent with numerous other measurements made at Lake Shore Cryotronics Inc R Morrison Grounding and Shielding Techniques in Instrumentation Wiley New york 1977 Vol 2 B 18 Application Notes
59. 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 gt E p Protective conductor terminal Frame or chassis terminal On supply Off supply f Fuse O H dA 1 8 Introduction Lake Shore Model 330 Autotuning Temperature Controller User s Manual CHAPTER 2 INSTALLATION 2 0 GENERAL This chapter covers general Model 330 installation instructions Inspection and Unpacking Paragraph 2 1 Repackaging for Shipment Paragraph 2 2 Definition of Rear Panel Connections Paragraph 2 3 Sensor Input Settings Paragraph 2 4 Grounding and Shielding Paragraph 2 5 Sensor Installation Paragraph 2 6 Sensor Curve Selection Paragraph 2 7 Precision Calibration Option Paragraph 2 8 Heater Setup Paragraph 2 9 Rack Mounting Paragraph 2 10 and Power Up Paragraph 2 11 2 1 INSPECTION AND UNPACKING Inspect shipping containers for external damage Make all claims for damage apparent or concealed or partial loss of shipment in writing to Lake Shore within five 5 days from receipt of goods If damage or loss is apparent please notify the shipping agent immediately Open the shipping containers Use the packing list included with the system to verify recei
60. Below 40 K a new conduction mechanism becomes dominant suggesting the influence of impurity conduction carrier freezeout increased ohmic behavior of the bulk material and p i n diode type behavior The only adjustable parameter in Eq 1 which is necessary for the present analysis is the parameter n This parameter can be determined quite easily from the IV characteristics of the silicon diode temperature sensor The parameter ls is eliminated by normalizing the IV curve to an arbitrarily chosen point on the curve The value of n 1 8 was found to give a relatively good fit to the IV data for both 305 and 77 K and has been assumed in the present discussion 7 Equation 1 can now be solved for V I V I nkT e in l Is 1 2 Substituting a dc current with an ac modulation lac lac cos t the average voltage read by the voltmeter in the dc voltage mode can be calculated from 47 V Vile Igo cos at dt 3 where T the period of integration of the voltmeter or approximately 2n Implied in this derivation is the assumption that is sufficiently small so that effects from diode capacitance on the order of picofarads can be ignored On carrying out the integration of Eq 3 and subtracting V lac the dc offset voltage is where lac lt lac ls If a small signal linear model is used the rms voltage across the diode can be easily related to lac nkT e V ms nkT AV V V lac AR 1441
61. Entry 4 3 1 Command List Structure Brief Description of Function Command Name CUNI Control Units Query Input CUNI Syntax of what user must input Returned K C V R or M Information returned in response to the query Remarks Used to query the unit for current control units information The character returned will be K for Explanation and definition of kelvin C for Celsius V for Volts R for Ohms or returned data M for millivolts 4 10 Remote Operation 4 3 2 Lake Shore Model 330 Autotuning Temperature Controller User s Manual Common Commands Common commands are input output commands defined by the IEEE 488 standard and are shared with other instruments complying with the standard Common commands begin with an asterisk xCLS Input Returned Remarks xESE Input Returned Remarks Example xESE Input Returned Remarks xESR Input Returned Remarks xIDN Input Returned Remarks xOPC Input Returned Remarks Remote Operation Clear Interface Command CLS Nothing Clears the bits in the Status Byte Register and Standard Event Status Register and terminates all pending operations Clears the interface but not the controller The controller related command is RST Configure Status Reports in the Standard Event Status Register ESE bit weighting Nothing Each bit is assigned a bit weighting and represents the enable disable status of the
62. Equivalent temperature errors are indicated along the right edge Application Notes Lake Shore Model 330 Autotuning Temperature Controller User s Manual The utilization of the small signal model has the advantage of being analytically simple However the model does not contain the nonlinearity inherent in the forward biased IV characteristics of a p n junction In an attempt to retain the non linear characteristics V lac lac cos at was expanded in a Fourier series The first term constant term is just the average dc voltage in Eq 3 and is not seen by the voltmeter operating in an ac measurement mode The remaining terms in the Fourier series can then be used to calculate the rms voltage which will be read by the voltmeter 2 le M Vs Se cosnat ZA SH dt 7 where an and bm are the Fourier coefficients In order to evaluate the Fourier coefficients VU was expanded in a power series around lac Sufficient terms were maintained in both the power series expansion and in Eq 7 to give a second order correction to Eq 5 1 nkTY 1 5 J ae O e dc s lac 15 Substitution of this result into Eq 4 gives the 77 K offset voltages shown in Fig 4 by the dashed line Slightly better agreement with the experimental data is seen at the higher rms voltages At 305 K the two calculation methods are in even better agreement and a plot similar to Fig 4 would show no difference The details of the extended calculation hav
63. Filter FILT 0 orFILT 1 Nothing Turns display filter on or off 0 Off 1 On Quiets display by taking a running average of 10 readings Display Filter Query FILT oor1 Returns display filter setting 0 Off 1 On Set Sample Channel to A or B SCHN A or SCHN B Nothing Sets the sample channel to sensor A or B Allow one controller update cycle 72 second before reading the sample data to ensure proper reading SCHN A term changes the sample channel to A Sample Channel Query SCHN AOrB Returns the current sample channel setting A channel A B channel B Sample Sensor Data Query SDAT 000 00 Returns sample sensor data A free field is active here The value returned is 7 characters a sign 5 digits and a decimal point The last digit may be a null 1 2345 term Typical response for a voltage query 123 40 term Typical response for a degrees Celsius query 234 50 term Typical response for a kelvin or degrees Celsius query Set Units for the Sample Channel SUNI K CUNI C OrCUNI S Nothing Set sample channel K kelvin C Celsius S appropriate sensor units volts for diodes ohms for RTDs or millivolts for thermocouples If operating in kelvin with a Model 330 11 SUNI S term makes the units volts the sensor units for a diode sensor Sample Units Query SUNI K C V R Or M Current sample units setting K kelvin C Celsius V volts R Ohms M millivolts
64. HE TEMPERATURE CONTROL LOOP If there is still an overshoot of the control temperature during transient changes of the set point within one s system it can be significantly reduced by the addition of a third control function to the controller called rate or derivative control Normally overshoot can be attributed to one of two causes 1 the application of much more power than is required to maintain the system at its desired set point or 2 the result of the thermal response relationships between the cooling power the heating power and the control sensor The best solution to the first possibility is to reduce the available power as discussed previously The second problem normally occurs with a large thermal mass where response is slow and overshoot due to the thermal inertia of the system can be quite large This overshoot is caused by the time lag between a change in output power and the control sensor sensing this change In very large non cryogenic systems this time lag can be 10 30 minutes In cryogenic systems it is usually less than a minute even near room temperature Consequently placement of the control sensor with respect to the heater is extremely important in the design of a cryogenic system as is the placement of both the heater and sensor with respect to the cooling power Rate action can be achieved by means of a differentiator circuit which provides a signal proportional to the rate of temperature change and 150 which is sub
65. IDN Query Identification HEAT Heater Query OPC Set Operation Complete RAMP Enable Disable Ramping OPC Query Operation Complete RAMP Ramping Enable Disable Query RST Reset Instrument RAMPR Set Ramp Rate in K min SRE Set Service Request Enable RAMPR Ramp Rate Query SRE Query Service Request Enable RAMPS Ramping Status Query STB Query Status Byte RANG Set Range TST Query Self Test RANG Range Query WA Wait To Continue RATE Set Rate Interface Commands RATE Rate Query ADDR Set Address RSET Set Reset RSET Reset Query ADDR Add ADD ress Query SETP Set Setpoint END EOI Query SETP Setpoint Query MODE Remote Mode D Tune Status MODE Remote Mode Query TUNE Tune Query TERM Terminator SEN Store Zone TERM Terminator Query ZONE Zone Query yo a a Eed A Compensation CCHN Set Control Channel nsau CCHN Control Channel Query ACOMP A Compensation Query CDAT Control Sensor Data Query ACUR Set Curve for A CUNI Set Control Units pip Curve A Query CUNI Control Units Query ATYPE A Input Type Query FILT Set Display Filter BCOMP Set B Compensation FILT Display Filter Query BCOMP B Compensation Query SCHN Set Sample Channel BCUR Set Curve for B SCHN Sample Channel Query BCUR Curve B Query SDAT Sample Sensor Data Query BTYPE B Input Type Query SUNI Set Sample Units CUID CURV SUNI S le Unit ample Units Query CURV Curve No Information Query ECUR Edit Curve FREE Curve Bytes Free Query KCUR Delete Curve SCAL SoftCal
66. ION OPTION NOVRAM REPLACEMENT The operating software for the Model 330 is contained on two Erasable Programmable Read Only Memory EPROM Integrated Circuits ICs The reference designator for the master EPROM is U11 DC HEX and the slave is U16 SV HEX The optional Precision Option is provided on a Non Volatile Ram Access Memory NOVRAM IC See Figure 5 9 for locations of these ICs Use the procedure below to replace either one or both existing software EPROMs or the NOVRAM CAUTION The EPROM and NOVRAM 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 1 Follow the REMOVE TOP procedure in Paragraph 5 6 2 Locate master software EPROM U11 DC HES slave EPROM U16 SV HEX or Precision Option NOVRAM U12 on the main circuit board Note orientation of existing IC See Figure 5 9 3 Use IC puller to remove existing EPROM s NOVRAM from socket Note orientation of new EPROM s NOVRAM Use IC insertion tool to place new device s into socket DALLAS A XXXXXXXXX P d E XXXXXXXXX Match notch on Match notch on O EPROM to notch 1 aM AIRE EE NOVRAM to 1 in socxet Typical EPROM notehiin socket Typical NOVRAM Follow the REPLACE TOP procedure in Paragraph 5 6 Proceed to Paragraph 2 12 and follow the power up sequence Service amp Calibration 5 5 Lake Shore
67. OTUNE The Autotuning algorithm determines controller gain Proportional reset Integral and rate Derivative by observing system time response upon setpoint changes under either P PI or PID control There are limitations to digital control and Autotuning First any control system is inherently unstable if the sampling rate frequency is not greater than twice the system bandwidth inverse of system time constant This is known as the Nyquist criterion With the current technology used in this controller i e sampling frequency etc digital control is possible for cryogenic systems with time constants near or greater than one second Most cryogenic systems operating above 1 kelvin meet this criteria Autotuning requires system time response measured as a result of a change in temperature setpoint Several points on this response curve must be measured to determine PID parameters Consequently for cryogenic systems where step responses are less than 5 seconds where there are few measured points correct determination of the PID parameters is difficult Manually select gain and reset rate is not normally required for better temperature control Fortunately fast cryogenic systems are not difficult to tune manually For slower systems with longer time constants which can be difficult to tune manually Autotuning obtains enough information on a step change to characterize the system and determine proper gain reset and rate In other
68. PUT DOWN LOAD A CURVE ENTER DRIVE AND FILE NAME OPEN FILES FOR INPUT AS 2 LINE INPUT 2 CURVES CLOSE 2 PRINT INPUT Get curve number from KB IF MID CURVES CURVES CURVES ELSE CURVES END IF 1 1 MID CURVES CURV xn 5 THEN CURV CURNUMS PRINT PRINT PRINT COMMANDS SENT TO 320 CMD LEFTS CURVES PRINT CMDS CMD CMDS TERMS PRINT 1 CMD FOR Z 1 TO DELAY NEXT Z 53 CHRCOUNT 54 POINTCOUNT 3 WHILE LEN CURVES gt CHRCOUNT 14 CMD MID CURVES CHRCOUNT 14 CHRCOUNT CHRCOUNT 4 14 PRINT POINTCOUNT SPACE 11 POINTCOUNT POINTCOUNT 1 CMD ECUR PRINT 1 CMD FOR I 1 TO DELAY NEXT I WEND PRINT PRINT PRINT GOTO LOOP1 CMD ENTER CURV CURNUMS 4 24 FILES ENTER DESTINATION CURVE NUMBER 11 to 31 CURVES CURNUMS CMDS TERMS Preset variable lengths Delay timer Get file name from KB Open ASCII disk file Read disk file into string Close disk file CURNUMS Test for DRC curve format Strip off DRC file header CURNUMS CURVES Add 300 series file header Add file header Screen prints to show what is sent Pick out header and first two points Send first command string to screen Add terminators Send curve create cmd to 321 320 330 Delay Character count for next curve point Curve data point counter Check for end of string Take out next point Advanc
69. Pressed Range Curve s Silicon Diode 1 c2 ed 2 Curve10 0 to 2 5 OTOR Di 4 Curve 10 SoftCal Series Platinum 0 to 300 3 DIN Curve 43760 GaAlAs Diode 0 to 6 0 Thermocouple 6 AuFe 0 0796 vs Chromel compensation Millivolts 10 to 10 Ge S 7 AuFe 0 03 vs Chromel 8 Type E chromel constantan Thermocouple 9 Type K chromel alumel 1 2 3 S compensation Millivolts 15 to 15 off 10 Type T copper constantan If the internal DIP switches are improperly set the display will read Er when the Input Type key is pressed The normal front panel display will show dashes to indicate improper DIP switch setting Improper Switch Setting DIP Switch S1 is for Channel A and S2 is for Channel B 5 6 Service amp Calibration Lake Shore Model 330 Autotuning Temperature Controller User s Manual 5 9 CHANGING SENSOR INPUT TYPE The factory establishes sensor input type and model number before shipping Configure sensor input type by setting DIP switches S1 and S2 on the main controller PCB To change the DIP Switch settings follow the REMOVE COVER procedure in Paragraph 5 6 and see the Table 5 1 DIP switch settings Switch diodes and resistor sensors in the field with no recalibration Diode Resistor sensors and thermocouple sensors cannot be exchanged After changing the DIP switches follow the REPLACE COVER procedure in Paragraph 5 6 5 10 CALIBRATION DIODE PLATINUM INPUT To calibrate the contro
70. T 2000 are trademarks of Microsoft Corporation NI 488 2 is a trademark of National Instruments Stycast is a trademark of Emerson amp Cuming Teflon is a trademark of DuPont De Nemours Copyright 1994 2000 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 A hereby declare Lake Shore Model 330 Autotuning Temperature Controller User s Manual Declaration of Conformity d Lake Shore Cryotronics Inc 575 McCorkle Blvd Westerville OH 43082 8888 USA that the equipment specified conforms to the following Directives and Standards Application of Council directives 73 23 EEC 89 336 EEC Standard to which Conformity is declared EN55022 Model Number EN50082 1 EN61010 1 330 Signature Date John M Swartz Printed Name President Position Lake Shore Model 330 Autotuning Temperature Controller User s Manual Electromagnetic Compatibility EMC for the Model 330 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 330 meets or exceeds
71. The BUS CONTROLLER designates to the devices on the bus which function to perform The MPS performs the functions of TALKER and LISTENER but cannot be a BUS CONTROLLER The BUS CONTROLLER is the digital computer which tells the MPS which functions to perform Below are Model 330 IEEE 488 interface capabilities SH1 Source handshake capability RL1 Complete remote local capability DC1 Full device clear capability DTO0 No device trigger capability C0 No system controller capability T5 Basic TALKER serial poll capability talk only unaddressed to talk if addressed to listen L4 Basic LISTENER unaddressed to listen if addressed to talk SR1 Service request capability AH Acceptor handshake capability PPO No parallel poll capability E1 Open collector electronics 4 1 1 IEEE 488 Interface Settings If using the IEEE 488 interface set the IEEE Address and Terminators Press the Address key to show the address Ad in the top display and the terminator in the lower display Hold the Address key and press the A key to increment the IEEE Address to the desired number or the W key to cycle the terminators through CR LF LF CR LF and End Release to accept the changes or current setting displayed 4 1 2 IEEE 488 Command Structure The Model 330 supports several command types These commands are divided into three groups 1 Bus Control see Paragraph 4 1 2 1 a Universal 1 Uniline 2 Multiline b Addressed Bus Control
72. Threaded Stud Cathode sensor 3mm x0 5 metric thread 5 5 mm across L 6mm flats 6 mm emm flats 6 mm DT 470 ET DT 470 MT Both adapters are gold plated copper hex head bolts with the SD package mounted in a slot on the adapter head The ET adapter screws into a 74 inch deep 6 32 threaded hole while the MT adapter screws into a 6 mm deep 3x0 5 mm threaded hole Before assembly the threads should be lightly greased with Apiezon N Grease Do not over tighten since the threads are copper and can be easily sheared Finger tight should be sufficient DT 470 BO The BO adapter should be mounted in the same manner as the CU The BO adapter contains its own thermal anchor and is an epoxy free assembly DT 470 CO The CO adapter is a spring loaded clamp to attach the DT 470 SD package to a flat surface It maintains pressure on the SD package as the temperature varies First remove the hold down cap which holds the three piece CO assembly together The CO assembly should appear as shown in the accompanying drawings Bolt the assembly into a 4 40 threaded hole The stop on the brass screw should rest against the mounting surface and it also prevents over compressing the spring Lift the edge of the clip using a small pliers or screw driver Slide the SD package into place underneath the clip and gently lower the clip onto the lid of the SD package Note that a slot is cut underneath the clip to accept the SD package Refer to the
73. V Q mV the Autotune Ramp and Zone features will not operate The user must return the display to K or C before these features will function While holding the Units key press the A key to cycle the Sample sensor units and the W key to cycle the Control Sensor between K C and V O mV Sample and Control units need not match 3 2 4 Thermocouple Temperature Compensation Model 330 4X Only For thermocouple sensors only Model 330 4X temperature compensation also displays when the Input Type key is pushed and held see Paragraph 2 7 2 1 The display is shown to the right In this display the Channel A thermocouple has temperature compensation on while the Channel B thermocouple has temperature compensation off To change temperature compensation status while holding the Input Type key press the A key to toggle Channel A temperature compensation on or off or the Y key to toggle the Channel B temperature compensation on or off Sample Operation 3 3 Lake Shore Model 330 Autotuning Temperature Controller User s Manual 3 2 5 Display Filter The filter function reads 10 sequential temperature readings over 5 seconds and displays a running average It quiets the display making it more readable when the sensor is exposed to fluctuating conditions Filter affects the display only and does not affect any other control functions Filter slows the display do not use it when ramping To turn the filter on press
74. accuracy by setting up a special modification to the Standard Curve 10 See Paragraph 3 2 7 Autotune Sets controller tuning to P PI PID Zone or Off See Paragraph 3 3 4 A and W This symbol next to a key indicates the function operates by holding the key and pressing the A key to change the top display setting and the W key to change the bottom display setting 3 1 2 Front Panel LED Display In normal operation the front panel LED display shows Sample Control temperature readings and heater status Other information displays on the various displays to the left and right of the temperature readings See Figure 3 2 Sample Remote Local Channel P PI PID or Zone Tuning SoftCal Heater Range Units C 330 U 3 2 Figure 3 2 Definition of Front Panel LED Display 3 2 THERMOMETRY FUNCTIONS The following front panel keyboard functions relate to Model 330 thermometry Input Type Paragraph 3 2 1 Channel Paragraph 3 2 2 Units Paragraph 3 2 3 Temperature Compensation Paragraph 3 2 4 Display Filter Paragraph 3 2 5 Curve Paragraph 3 2 6 and SoftCal Paragraph 3 2 7 3 2 Operation Lake Shore Model 330 Autotuning Temperature Controller User s Manual 3 2 1 Input Type Press and hold the Input Type key to verify internal DIP switch settings that determine sensor input type as defined in Table 2 1 When factory configured the Model number corresponds the type of sensor used in each channel of the
75. after rewarming Protect the injured tissue from further damage and infection and call a physician immediately Flush exposed eyes 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 Introduction 1 7 Lake Shore Model 330 Autotuning Temperature Controller User s Manual 1 6 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 330 protects the operator and surrounding area from electric shock or burn mechanical hazards 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 Temperature 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 Ground The Instrument To minimize shock hazard connect the instrument chassis and cabinet an electrical ground The instrument
76. alized Factory settings are Heater Off Setpoint 0 0 Units K Input Type Determined by Model Number Filter Off TempComp Off Ramp Rate Off 0 Curve Determined by Model Number all User and SoftCal Curves erased Zone Settings Default zone settings are shown in the figure below Baud 300 Autotune Auto PI selected P 50 20 D 100 Operation 3 13 Lake Shore Model 330 Autotuning Temperature Controller User s Manual Default Zone Settings Zone 10 Setpoint Heater High Zone 09 Setpoint Heater High Zone 08 Setpoint Heater High Zone 07 Setpoint Heater High Setpoint Heater High Zone 05 Setpoint Heater High Zone 04 Setpoint Heater High Zone 03 Setpoint Heater High Zone 02 Setpoint Heater Low Setpoint Heater Low 3 4 5 Power Up PUP Configuration Store a Model 330 Power Up PUP configuration to ensure that it powers up to a user defined state after power down Parameters including heater range setpoint gain reset units and curve number store in non volatile memory and are retained even when the line cord is disconnected To view PUP status hold the Enter key for about 5 seconds to see the display to the right Control On updates power up settings when the user changes them via the front panel or over the remote interface On is the default PUP If left on the instrument powers up in the same configuration it was powered down in Off disables updates to the power up m
77. ally posted on the side of each dewar Keep cryogenic dewars in a well ventilated place protected from the weather and away from heat sources Figure 3 1 shows a typical cryogenic dewar NON 1 5 2 Liquid Helium and Nitrogen Safety Precautions eo LIQUID Transfer LHe and LN and operate storage dewar controls in accordance with manufacturer supplier instructions During transfer follow all safety precautions written on the storage dewar and recommended by the manufacturer WARNING Liquid helium is a potential asphyxiant and can cause rapid suffocation without warning Store and use in an adequately ventilated area DO NOT vent the container in confined spaces DO NOT enter confined spaces HELIUM St KEEP UPRIGHT where gas may be present unless area is well ventilated If inhaled remove to fresh air If not breathing give artificial respiration If breathing is difficult give oxygen Get medical attention Figure 1 3 Cryogenic Liquid helium can cause severe frostbite to exposed body parts DO Storage Dewar NOT touch frosted pipes or valves For frostbite consult a physician immediately If a physician is unavailable warm the affected parts with water that is near body temperature Two essential safety aspects of handling LHe are adequate ventilation and eye and skin protection Although helium and nitrogen gases are non toxic they are dangerous because they replace air in a normal
78. an analog to digital AD converter The digitized temperature is then compared to the digital set point within the microprocessor and by means of an appropriate algorithm the average power to the heater is adjusted A converter with a 14 bit resolution 1 part in 16 384 enables the microprocessor to determine the temperature to approximately 4 mK at 4 2 kelvin using the diode sensor of Figure 2 In a system which is inherently stable the control temperature stability can be no better than the temperature resolution of the AD converter 4 mK for this example Cost effective AD converters with such resolution have sampling times in the half second range In the world of ovens furnaces and other large industrial processes which operate above room temperature stable control can be maintained by digital systems updating temperature only once or twice a second This is for the same reason that ON OFF controllers are successful in these cases the large thermal time constants of the controlled environments However as discussed in Section II the time constants are much shorter in cryogenic systems so much so that temperature can and frequently does change at a rate which exceeds the sampling frequency of a typical digital cryogenic controller approximately 2 Hz A good example is a mechanical refrigerator based on the Gifford McMahon cycle At 10 kelvin and below these refrigerators unloaded often have a peak to peak variation in temperature which
79. and the V lead to TP1 Adjust this voltage with R10 until it reaches 2 5000 volts Zero Calibration Disable room temperature calibration over the front panel Short the two TC input terminals with a very short piece of wire Change the display to mV units and adjust R6 for Channel A or R8 for Channel B Adjust until the display shows 0 0000 mV Compensation Calibration Enable room temperature calibration over the front panel Select Celsius for display units Keep the two TC input terminals shorted Adjust R28 TP COMP until display shows current room temperature 20 to 30 C range Verify linearity with a voltage standard connected to TC input terminals Check at both 10 mV and 210 mV Follow the REPLACE TOP procedure in Paragraph 5 6 Once the actual thermocouple is attached to the input it may be necessary to adjust R28 to correct for any unusual junction effects at the input terminals 5 12 MODEL 330 4X THERMOCOUPLE INTERNAL OFFSET ADJUSTMENT When attaching a new or different thermocouple to the controller adjust the offset to compensate for discrepancies in thermocouple material leads and connections The Model 330 provides offset adjustment trimpots to allow offset calibration of the thermocouple NOTE The offset adjustment compensates for the thermocouple used in the calibration If another thermocouple is attached or the thermocouple has aged or the configuration of the system is changed then repeat the offset adjustmen
80. aph 2 7 2 for Thermocouple Model 330 4X sensors and Paragraph 2 7 3 for sensor input error messages 2 6 1 Diode Model 330 1X and Platinum Model 330 2X Connections Table 2 2 Diode or Platinum Input Connections The Model 330 has a rear panel 6 pin input connector for silicon diode Model 330 1X or platinum resistance Model 330 2X sensors Table 2 2 lists lead connections Current See Paragraph 2 7 1 1 for two lead vs four lead measurement SE Paragraph 2 7 1 2 for connecting leads Paragraph 2 7 1 3 for sensor mounting and Paragraph 2 7 1 4 for the effect of measurement errors due to AC noise Current 1 mA platinum Voltage Current 10 pA diodes Shield 2 6 1 1 Two Lead Versus Four Lead Measurements Use a four lead connection for two lead resistive elements and diodes to avoid current resistive IR drops in the voltage sensing pair that cause measurement error In two lead measurement the leads that measure sensor voltage are also current carrying leads The voltage measured at the instrument is the sum of the sensor voltage and the IR voltage drop within the two current leads Because heat flow down the leads can be critical small diameter wire and significant resistance per foot is preferred to minimize this heat flow Consequently a voltage drop within the leads may exist Two Lead Measurements Sometimes system constraints dictate two lead measurements Connect n S s I the positive terminals V
81. ation cannot transfer from one sensor to another 3 2 7 1 SoftCal Errors The advantage of performing a SoftCal with the actual sensor and Model 330 that take measurements is that it compensates for the combined temperature error of the sensor and controller If the sensor is calibrated separate from the Model 330 the specified accuracy of the Model 330 must be added to the sensor accuracy SoftCal accuracy also depends on the precision of the setting points An error in the setting temperature can actually degrade sensor performance beyond normal tolerance bands For example the boiling point of nitrogen at standard pressure is near 77 4 K During a storm this can change as much as 0 2 K because of the change in atmospheric pressure These types of errors must be added to the sensor accuracy Operation 3 5 Lake Shore Model 330 Autotuning Temperature Controller User s Manual 3 2 7 2 Customer Performed SoftCal Depending on the desired temperature range the Customer may perform a 2 point or 3 point SoftCal This example assumes a 3 point SoftCal For 2 point omit the steps associated with reading the voltage at 4 2 K Requirements are a stable temperature source at three temperatures 4 2 K Liquid Helium 77 35 K Liquid Nitrogen and 300 K room temperature It does not matter in which order SoftCal data is taken NOTE Allow the instrument to warm up for an hour before beginning the SoftCal procedure In this example we will take o
82. be free from defects in material or workmanship for a period of 12 months from the date of shipment During the warranty period under authorized return of instruments or component parts to Lake Shore freight prepaid the company will repair or at its option replace any part found to be defective in material or workmanship without charge to the owner for parts service labor or associated customary return shipping cost Replacement or repaired parts will be warranted for only the unexpired portion of the original warranty or 90 days whichever is greater All products are thoroughly tested and calibrated to published specifications prior to shipment Calibration Certifications are offered for 6 month periods only Where such documentation must be updated a re certification service is offered by Lake Shore at a reasonable cost LIMITATION OF WARRANTY This warranty does not apply to defects resulting from improper installation product modifications made by others without Lake Shore s express written consent or from misuse of any product or part This warranty also does not apply to fuses software non rechargeable batteries or problems arising from normal wear or failure to follow instructions This warranty is in lieu of any other warranties expressed or implied including merchantability or fitness for a particular purpose which are expressly excluded The owner agrees that Lake Shore s liability with respect to this product shall be set for
83. breathing atmosphere Liquid helium is an even greater threat because a small amount of liquid evaporates to create a large amount of gas Store and operate cryogenic dewars in open well ventilated areas When transferring LHe and LN protect eyes and skin from accidental contact with liquid or the cold gas issuing from it Protect eyes with full face shield or chemical splash goggles safety glasses even with side shields are inadequate Always wear special cryogenic gloves Tempshield CryoGloves 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 Wear long sleeve shirts and cuffless trousers long enough to prevent liquid from entering shoes 1 5 3 Recommended First Aid Post an appropriate Material Safety Data Sheet MSDS obtained from the manufacturer distributor at every site that stores and uses LHe and LN The MSDS specifies symptoms of overexposure and first aid If a person exhibits symptoms of asphyxia such as headache drowsiness dizziness excitation excessive salivation vomiting or unconsciousness remove to fresh air If breathing is difficult give oxygen If breathing Stops 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 by bathing it in warm water not exceeding 105 F 40 C DO NOT rub the frozen part either before or
84. charge Sensitive Components eeeeeereeeeeeeeeee 1 6 1 4 2 Handling Electrostatic Discharge Sensitive Components sees 1 6 1 5 Handling Liquid Helium and Liquid Ntrogen meme 1 7 1 5 1 Handling Cryogenic Storage Dewars sse eee mener 1 7 1 5 2 Liquid Helium and Nitrogen Safety Precautions een 1 7 1 5 3 Recommended First Ad 1 7 1 6 EE SUMA T 1 8 1 7 Satety Symbols dte edat mte iba te E E Ta RR Te reae E Eee erede aide 1 8 2 INSTALPATION 2 Innere pepe 2 1 2 0 EEE e PM tee 2 1 2 1 Inspection and Unpacking c ecccceceeeeeeeeeeceeeeeeeeececaeceeeeeeeseccacaeceeeeeseseeneeaeeeeeeesesenaees 2 1 2 2 Repackaging For Shipment eeeeieeeieeseeesiseee eee ten enint hinten nnns 2 1 2 3 Definition of Rear Panel Connections enm eem 2 2 24 Sensor Input Settings ecer EE 2 3 2 5 Grounding and Shielding a nennsss nanesenia iii eene nenrnen nnne nnns 2 3 2 6 Sensor Installation ote oe ce eoe dedit du i be e ade 2 4 2 6 1 Diode Model 330 1X and Platinum Model 330 2X Connections sseeeeeceeeeeeeeeeeeee 2 4 2 6 1 1 Two Lead Versus Four Lead Measurements sssssseenssserterrrnseerttnnrnnserrtrrnnnnnentent 2 4 2 6 1 2 Heat Sinking Sensor Leads sss eene 2 5 2 6 1 3 Sensor MOUNN ET 2 5 2 6 1 4 Measurement Errors Due to AChNoise nnmnnn 2 6 2 6 2 Thermocouple Model 330 4X Connections eene 2 6 2 6 2 1 Thermocouple Com pensation nere
85. complex than for more stable predictable high temperature loads For example over its useful temperature range a single cryogenic load may exhibit thermal property variations of three orders of magnitude or greater A temperature setpoint change initiates the Autotuning function When Autotuning is active the TUNE light blinks and the controller automatically gathers data to determine optimum control parameters The TUNE light stops blinking and tunes no more until the next setpoint change The controller never disturbs the system It tunes only on user setpoint changes System design is also a factor Under some circumstances very fast cryogenic systems may not provide sufficient data points on step changes to accurately predict proper control settings Unusually large thermal lags caused by poor placement and mounting relative to the heater can obstruct the correlation between the heater and the system necessary to tune properly For slower systems with longer time constants which are very difficult to tune manually Autotuning can obtain enough information on a step change to characterize the system and determine proper values for Gain Reset and Rate To put the controller in Autotune PID mode hold the Autotune key and press the W key to cycle the Control window display to P PI or PID Release when the desired setting is reached The TUNE annunciator in the upper Sample window comes on when any of the selected Autotuning element
86. conditions the user may prefer to stay with manual settings For example when a closed cycle refrigerator has very little mass on its second stage and is near its bottom temperature Autotuning may give poor results for control settings due to the large temperature fluctuations of the cooling cycle Adding mass to the second stage smoothes out these fluctuations but lengthens cool down time Lake Shore simplified the input of the rate time constant to correspond to a percentage of the reset time constant i e 0 to 20096 Consequently in manual mode with RATE set to 10096 any change in RESET causes the controller to automatically calculate the RESET time constant 999 RESET and set the RATE time constant at 1 8 of the RESET time constant This is one half the conventional Zeigler Nichols setting for rate and results in less overshoot of a given setpoint Therefore once RATE is set as a percent you need not worry about updating its value with setpoint changes resulting in new PI settings For less RATE set RATE at something less than 10096 Remember many cryogenic systems require no rate 096 See the application note titled Fundamentals for Usage of Cryogenic Temperature Controllers in Appendix D if you are not familiar with cryogenic temperature controllers Introduction 1 5 Lake Shore Model 330 Autotuning Temperature Controller User s Manual 1 3 PRECISION CALIBRATION OPTIONS The Lake Shore Precision Calibration Option converts calibra
87. controller The factory configuration appears on the B page immediately following the title page of this manual For example a Model 330 11 displays Control This display shows that both Channel A and B Sensors are Sl or Silicon Diodes Other input types are PT for Platinum RTDs AS for GaAlAs Diodes and TC for Thermocouples The Input Type display is for information only no user changes are available To change input type see Paragraph 5 9 3 2 2 Channel The Channel key specifies which sensor to use for Sample and Control While holding the Channel key press the A key to cycle the Sample display between Channel A and B or the v key to cycle the Control display between Channel A and B Release when you reach the desired configuration Depending on the installation either Channel may be used for Sample and Control 3 2 3 Units The Units key gives slightly different display choices depending on the sensor input and model number All four models permit selection of temperature displays in kelvin K or Celsius C The difference lies in sensor output selection For silicon and GaAlAs diodes Models 330 1X and 3X respectively the additional units selection is Volts V For the Platinum RTDs Model 330 2X the additional units selection is ohms Q For the thermocouple Model 330 4X the additional units selection is millivolts mV Units in K is the default for all models NOTE When the display is set to read in
88. ctor configured as DTE If the interface is DCE a Null Modem Adapter is required to exchange Transmit and Receive lines C 330 U 4 2 Figure 4 2 Optional Serial Interface Connections Remote Operation 4 7 Lake Shore Model 330 Autotuning Temperature Controller User s Manual 4 2 1 Serial Interface Hardware Configuration The Model 330 operates at two different Baud rates 300 or 1200 Hold the Baud key and press the W key to cycle between 300 and 1200 The remaining communication parameters are fixed as defined in Table 4 3 The serial interface connector is a standard 6 wire RJ 11 telephone jack Lake Shore offers the optional Model 2001 10 foot Cable Assembly Model 2002 RJ 11 to DB 25 Adapter and the Model 2003 RJ 11 to DE 9 Adapter as shown in Figure 4 2 To make your own cable see Figure 5 6 Table 4 2 Serial Interface Parameters Transmission Three Wire Baud Rate 300 or 1200 Connector RJ 11 Modular Socket Bits per Character 1 Start 7 Data 1 Parity 1 Stop Timing Format Asynchronous Parity Type Odd Transmission Mode Half Duplex Terminator CR ODH LF OAH Data Interface Levels Transmits and Receives Using EIA Voltage Levels 4 2 2 Sample BASIC Serial Interface Program The program in Table 4 3 is a sample interactive serial poll routine for the Model 330 Serial Interface written in QuickBASIC V4 0 Below are examples using this program User supplied input appears in bold type TER COMMAND CUNI K Set Contr
89. d 4 V wu Ea 2 Is 5 ms J2V dl e 42V e Algo tls Evaluation of Eq 5 and substitution back into 4 yields 2 Ay BET di ds 6 e 2 nkT where 2 eV ms nkT lt 1 for a physical solution Equation 6 predicts an offset voltage which is independent of both frequency and dc operating current and is shown plotted in Fig 4 by the solid line The agreement with the experimental measurements is quite good verifying the overall picture as to the effect of induced currents on diode temperature sensors The results recorded at 305 K are described equally well by Eq 6 10 1uA A 10 uA 100 uA 10 2 3 4 5 6 RMS AC VOLTAGE mV 7 8 FIGURE 4 DC offset voltage as a function of rms ac voltage across a silicon diode temperature sensor operating at 77 K The symbols represent data recorded at three different dc operating currents with a 60 Hz signal superimposed The solid curve gives small signal model results while the dashed curve represents the extended calculations Equivalent temperature errors are indicated along the right edge 104 AK 10 01K gt E gt 10 4 i 001 K 1uA 10 A 10 uA 100 uA 1 0 4 8 12 16 20 24 28 32 RMS AC VOLTAGE mV FIGURE 5 DC offset voltage as a function of rms ac voltage across a silicon diode temperature sensor operating at 4 2 K The symbols represent data recorded at three different dc operating currents with a 60 Hz signal superimposed
90. d A voltage is taken at the 2 or 3 very detailed report that includes Curve 10 is replaced with the data points These voltages can be Raw Temperature Data custom curve for that entered into controllers with Poly nomial Fits sensor SoftCal capability A calibration Interpolation Tables report is sent with the sensor is sent with the sensor Operation User calculates break points and manually enters Option data into the controller 8002 05 A Precision Option can be generated for either SoftCal or the Precision Calibration 8001 Precision Option Precision Option Precision Option breakpoint pairs breakpoint pairs breakpoint pairs are loaded in a are loaded on a are loaded in a NOVRAM and Floppy Disk in NOVRAM for field factory ACSII format for installation installed Customer downloading C 330 U 3 3 wmf Figure 3 3 Sensor Calibrations and Precision Options 3 7 Lake Shore Model 330 Autotuning Temperature Controller User s Manual 3 3 CONTROL FUNCTIONS The following front panel keyboard functions relate to Model 330 control Heater Paragraph 3 3 1 Setpoint Paragraph 3 3 2 Ramp Paragraph 3 3 3 Autotune Paragraph 3 3 4 Manual PID Paragraph 3 3 5 and Zone Paragraph 3 3 6 3 3 4 Heater This key controls heater ranges Four heater ranges are available High Medium Low and Off The indicators HIGH MED LOW or OFF appear in the Control window to indicate the currently sel
91. d clamp or damaged through solder mounting DT 470 LR 3 2mm 12 19mm The gold plated copper LR adapter is designed for insertion into a 1 8 inch diameter k T hole A thin layer of Apiezon N Grease should be applied to the copper adapter Anode before insertion This eases installation at room temperature and enhances the thermal contact 3 1 mm dia Cathode DT 470 CU DT 470 DI DT 470 CY The gold plated copper CU DI and CY 2 9 mm diameter 14 3 mm dia adapters serve as both sensor and thermal anchor assembly These adapters mount to a flat surface with a 4 40 brass screw Avoid over tightening the screw use only enough force to firmly hold the sensor in place A brass screw is recommended as the 0 76 mm off center differential thermal contraction between the adapter and the screw causes the mounting assembly to tighten as opposed to loosen when the system cools Apply a thin layer of Apiezon N Grease to enhance thermal contact between the adapter and mounting surface 8 mm zomm diameter thick 2 9 mm dia hole 5 1mm centered thick DT 470 CU DT 470 DI DT 470 CY The CU adapter has four color coded leads Red I Green V Clear V and Blue I The CY adapter has two color coded leads Yellow and Green The green lead on the DI adapter is the cathode Application Notes Lake Shore Model 330 Autotuning Temperature Controller User s Manual DT 470 ET DT 470 MT SD 556 32 sensor
92. d on any selected channel Issues a Service Request if enabled Standard Event Status ESB Bit 5 When set indicates if one of the bits from the Standard Event Status Register has been set See Paragraph 4 1 4 2 4 1 3 2 Standard Event Status Register and Standard Event Status Enable Register The Standard Event Status Register supplies various conditions of the Model 330 STANDARD EVENT STATUS REGISTER FORMAT Bt 7 6 5 4 3 2 1 O0 Welghting 128 84 92 46 J 8 4 d Bit Name Bits 2 and 6 are not used Reports of this register interrupt the user only if the bits are enabled in the Standard Event Status Enable Register and if bit 5 of the Service Request Enable Register is set The Standard Event Status Enable Register allows the user to enable any of the Standard Event Status Register reports The Standard Event Status Enable command ESE sets the Standard Event Status Enable Register bits Setting a bit of this register enables that function To set a bit send the command at GE with the sum of the bit weighting for each bit to be set See the ESE command The Standard Event Status Enable Query ESE reads the Standard Event Status Enable Register ESR reads the Standard Event Status Register Once this register has been read the bits are reset to zero Power On PON Bit 7 Set to indicate a controller off on off transition Command Error CME Bit 5 Set to indicate a comma
93. dow display to PI This is the Model 330 default condition 3 3 4 4 Gain Only With the Gain P only control algorithm the controller initiates no time dependent control parameters other than digital sampling rate In this mode characteristics of the controlled system are more apparent but there is a temperature offset from the setpoint To select the P tuning algorithm hold the Autotune key and press the v key to cycle the Control window display to P 3 3 5 Manual Control Settings PID In manual mode the controller accepts PID parameters from the user to provide three term PID control To put the controller in Manual mode hold the Autotune key and press the W key to cycle the lower Control window display to OFF then release The controller is now in Manual mode and the user may set gain Proportional see Paragraph 3 3 5 1 reset Integral see Paragraph 3 3 5 2 and rate Derivative see Paragraph 3 3 5 3 Paragraph 3 3 5 4 discusses the effect of temperature on tuning parameters 3 3 5 4 Setting Gain Proportional Enter a gain Proportional value from 000 to 999 To enter a gain value press the P key The lower Control window display shows the current P setting the default is 50 with the units place blinking Use the numeric keypad to enter a new setting Press Enter to accept the new Proportional setting or Escape to return the normal display and retain the old setting To experimentally determine proper gain use the follo
94. e accuracy to within 0 25 K at low temperature and to within 0 5 K at room temperature Band 13 sensors are accurate to within 1 0 K at low temperature and to within 1 0 of temperature or better from 100 K to 475 K For better accuracy use SoftCal Implement SoftCal as a method or a service 1 The Customer may perform the SoftCal procedure Use the Model 330 and the silicon diode sensor to sense either two or three sources of a stable temperature For a 3 point SoftCal sense stable temperatures of 4 2 K Liquid Helium 77 35 K Liquid Nitrogen and 295 K Room Temperature For a 2 point SoftCal sense stable temperatures of 77 35 K and 295 K See Paragraph 3 2 7 2 User performed SoftCal has the advantage of nulling both sensor and controller inaccuracies 2 Lake Shore provides an inexpensive SoftCal Calibration Service that provides voltages corresponding to the 2 or 3 point calibrations The calibration consists of a modified T vs V Curve 10 Table for a specific DT 400 Series Sensor A SoftCal Report is generated that includes the voltages for data points and a unique sensor curve table interpolated from these 2 or 3 points Enter the voltages over the remote interface see Paragraph 3 2 6 3 With either method the Model 330 creates a new curve for this specific diode and stores it as Curve 11 thru 31 in controller memory This procedure can make an inexpensive Band 13 diode more accurate than our tightest Band 11 diode The calibr
95. e count to next point Send next point to screen Build next command Send to instrument Delay TO RETURN CURVE FROM INSTRUMENT Curve load complete Remote Operation Lake Shore Model 330 Autotuning Temperature Controller User s Manual Below are sample outputs from the program Sample ACSII File No 1 Older DRC Sensor Format XC06 S00TG120ACS2 8333 0 86045 325 0 0 90212 310 0 0 94350 295 0 0 98457 280 0 1 02532 265 0 1 06566 250 0 1 09231 240 0 1 11874 230 0 1 14489 220 0 1 15784 215 0 1 17072 210 0 1 18349 205 0 1 19616 200 0 1 20869 195 0 1 22109 190 0 1 23331 18 5 0 1 24534 180 0 1 25717 175 0 1 26875 170 0 1 28009 165 0 1 29116 160 0 1 30194 155 0 1 31241 150 0 1 32258 145 0 1 33241 140 0 1 34192 135 0 1 35108 130 0 1 35 991 125 0 1 36840 120 0 1 37657 115 0 1 38440 110 0 1 39189 105 0 1 39908 100 0 1 40597 095 0 1 41258 090 0 1 41894 085 0 1 42509 080 0 1 43712 070 0 1 44327 065 0 1 44993 060 0 1 45288 058 0 1 45611 056 0 1 45973 054 0 1 46394 052 0 1 46904 0 50 0 1 47551 048 0 1 48412 046 0 1 49606 044 0 1 51300 042 0 1 53706 040 0 1 5525 0 039 0 1 57064 038 0 1 59183 037 0 1 61638 036 0 1 64461 035 0 1 67679 034 0 1 7 1316 033 0 1 75390 032 0 1 79917 031 0 1 84902 030 0 1 90348 029 0 1 96261 028 0 2 02646 027 0 2 09484 026 0 2 16753 025 0 2 24441 024 0 2 32537 023 0 2 41034 022 0 2 49920 021 0 2 63876 019 5 2 83726 017 5 3 05000 015 5 3 27618 013 5 3 51800 011 5 3 71192 010 0 3 91739 008 5 4 13945 007 0 4 36487 005 6 4 5
96. e mathematical model which is presented below One surprising aspect of the data acquisition was how well the signal processing in the voltmeter could hide even high ac levels in the dc measurement modes For example operating at 10 uA dc and 77 K with a rms noise level of 6 mV gives a dc voltage offset of about 1 5 mV which is about a 0 6 K temperature error When reading the voltage signal using the filtering and integrating capabilities of the HP 34564 the dc voltage reading is stable to better than 0 02 mV 8 mk This stability gives a deceptive view of exactly how accurate the temperature measurement really is and emphasizes the importance of checking all aspects of a measuring system Application Notes B 15 Lake Shore Model 330 Autotuning Temperature Controller User s Manual The measured offset voltages shown in Figs 4 and 6 can be understood by using the well known result from p n junction theory Is exp eV nkT 1 1 where I the forward current through the junction I the reverse saturation current e the electron charge V the voltage across the junction k Boltzmann s constant and T the absolute temperature n is a parameter depending on the location of the generation and recombination of the electrons and holes and typically has a value between 1 and 2 This expression for the IV characteristics of a p n junction is valid from approximately 40 K to above 300 K for the silicon diodes discussed here
97. e not been given as the mathematics is somewhat tedious and the slight discrepancies between the small signal model and the extended model do not justify the added complexity For all practical purposes Eq 6 can be reliably used above 40 The physics of a p n junction at 4 2 K is not clearly understood and attempts to correlate the present data by modeling low temperature IV characteristic of a diode failed If the diode does take on a p i n type behavior the different curves shown in Fig 5 for 1 10 and 100 pA can possibly be understood in terms of the additional current dependent terms in the IV curve 6 Another explanation for the significant offset voltage at 100 pA could be self heating in the diode If the diode is operated at too high a power level the diode has a tendency to warm slightly above the surrounding environment This will have the effect of distorting the IV curve in the direction of lower voltages at higher currents This distortion will then increase the offset voltage At 4 2 K self Heating usually becomes a problem as the current approaches 100 pA Application Notes 10 T 77K loc 10 UA 10 A 60 Hz 10 1kHz 20 kHz 0 1 2 3 4 5 6 7 8 RMS AC VOLTAGE mV FIGURE 6 DC offset voltage as a function of rms ac voltage across a silicon diode temperature sensor operating at 77 K The symbols represent data recorded at a 10 uA dc current with the ac current modulation at 60 1000 and 20 000 Hz
98. e range of 0 to 10 K The medium temperature point is taken in the range of 50 to 100 K The high temperature point is taken in the range of 200 to 300 K If the actual reading is somewhere between these ranges no data point will be taken and no curve generated To take a second SoftCal measurement near 77 35 K immerse the sensor in liquid nitrogen and allow the reading to stabilize Repeat Steps 3 thru 8 To take the third SoftCal measurement allow the temperature sensor to stabilize at ambient temperature Take an independent temperature measurement of the air at the location of the temperature sensor Repeat Steps 3 thru 8 Erase old calibration points if calibrating a new sensor To erase old calibration points enter zero as a calibration point This will not erase any curves To turn off SoftCal without the loss of the calibration select another Curve number 3 2 7 3 Entering Voltage Values from a Lake Shore SoftCal Report If a Lake Shore SoftCal Report was purchased the voltage values for the 2 or 3 point calibration can be entered and the resulting modified Lake Shore Curve 10 stored as Curve number 11 to 31 in the controller memory The voltages can only be entered using an IEEE 488 or Serial Interface See the SCAL Command in Chapter 4 for how to enter SoftCal voltages 3 6 Operation Standard Lake Shore Model 330 Autotuning Temperature Controller User s Manual Lake Shore DT 400 Series Silicon Diode Temperature Sensor
99. e sse danses trend nn 1 5 1 3 Cryogenic Storage Dewar sse eene en nennen eas kavi deai nns 1 7 2 1 Typical Model 330 Rear Panel oneic iinei i A iA 2 2 2 2 Heater J mper JMBO9 i estie rette ru o d t D e e ed he dee 2 9 3 1 Model 330 Front Panel 3 1 3 2 Definition of Front Panel LED Display enm enm eene nnns 3 2 3 3 Sensor Calibrations and Precision Options nennen nnn 3 7 3 4 Record of Zone Setge gm ec EO Oa eee D HR aerea 3 12 4 1 Typical National Instruments GPIB Configuration from IBCONF ESE 4 6 4 2 Optional Serial Interface Connechons mener 4 7 5 1 Power FUSE ACCESS coire d ee tid sio paite o tuae Ea ra paa ke pa tu Doe pde a E 5 1 5 2 SERIAL I O RJ 11 Rear Panel Connector Details sssssssssssseeeeeemennee 5 2 5 3 SENSOR CHANNEL A and B Rear Panel Connector Details ssssssssssssssssss 5 2 5 4 HEATER OUTPUT Rear Panel Connector Details 5 2 5 5 IEEE 488 Rear Panel Connector Details 5 3 5 6 Model 2001 RJ 11 Cable Assembly Wiring Details ssseee 5 4 5 7 Model 2003 RJ 11 to DE 9 Adapter Wiring Details sse m 5 4 5 8 Model 2002 RJ 11 to DB 25 Adapter Wiring Details 5 4 5 9 Typical Model 330 PCB Layo t siss si isnie ate nene nennen ennemi nennen enne nnns 5 8 6 1 Model 2001 RJ 11 Cable Aesembhy sse nennen nennen nennen nnne 6 4 6 2 Model 2002 RJ 11 to DB 25 Adapter eene errem nnns 6 4 6 3 Model 2003 RJ 11 to DE 9 Adapter ssssssssss
100. ected range Once selected the 20 segment Heater bar graph display indicates to the nearest 5 the Heater is on MEDium setting percentage of heater current applied Heater Output is at 4596 The percentage of current reflects the percentage of full scale current applied to heater output for the selected range Output changes automatically according to control parameters The figure above shows the heater set to MEDium and output currently at 45 of full scale If the controller controls a system with less than 10 heater output it may be necessary to reduce the heater range A 25 Q load is required to get a full 25 Watt H eater Heater 25 W with 25 O 50 W with 50 Q load is required to get a full 50 Watt power Range Current Heater Power Heater Power output on the 50 W setting See Paragraph Oto1A 25 Watts 50 Watts 2 10 for additional heater setup details MEDIUM 0 to 0 3A 2 5 Watts 5 Watts If the heater load drops below 10 Q for a 25 0t00 1A 0 25 Watts 0 5 Watts W heater setting or 35 for a 50 W heater setting the output turns off to prevent instrument overheating If this occurs cycle the heater range through OFF to re engage the heater Error 30 Er30 appears if measured heater output does not match the predicted output and the controller turns the heater off Check heater resistance and test for shorts in heater wiring then turn the heater on again If the error message returns consult the factory 3 3
101. ed from the sensing element and leads make all thermal contact to the sensor through the base A thin braze joint around the sides of the SD package electrically connects to the sensing element Avoid contact to the sides with any electrically conductive material When installing the sensor verify there are no electrical shorts or current leakage paths between the leads or between the leads and ground IMI 7031 varnish or epoxy may soften varnish type lead insulation so that high resistance shunts appear between wires if there was insufficient time for curing Slide Teflon spaghetti tubing over bare leads when the possibility of shorting exists Avoid putting stress on the device leads and allow for thermal contractions that occur during cooling which may fracture a solder joint or lead installed under tension at room temperature For temporary mounting in cold temperature applications use a thin layer of Apiezon N Grease between the sensor and sample to enhance the thermal contact under slight pressure The preferred method to mount the DT 470 SD sensor is the Lake Shore CO Adapter CAUTION e Use a heat sink when soldering sensor lead wires Lake Shore will not warranty replace any device damaged by solder mounting or use of a user designed clamp NOTE Apply Stycast epoxy only to underneath of the DT 470 SD package Covering the sensor with epoxy places stress on the sensor that may cause shifts in readings For semi permanent mount
102. el 330 Autotuning Temperature Controller User s Manual lll PROPORTIONAL CONTROL The block diagram in Figure 1 shows a systems in which only proportional control is being used In this system the desired control temperature setting set point is being compared to the sensor signal and the difference or error signal including polarity is amplified within the controller When the sensor temperature corresponds to the set point temperature in voltage for a diode or resistance for a resistor the sensor signal will be equal to but opposite in polarity to the set point signal and the error signal will be zero In older instruments the set point is normally calibrated in millivolts or volts or resistance corresponding to the sensor output signal Most modern controllers have stored within them the appropriate voltage temperature or resistance temperature sensor characteristic so that the set point can be calibrated directly in temperature However as discussed in Section VII this convenience feature can compromise the resolution and accuracy of the controller The output of the controller is dc power to a resistive heater the output magnitude of which depends on the size and sign of the error signal as well as on the gain of the deviation amplifier and the output power supply Since the controller s power output state tracks the deviation amplifier output it is evident that the power output is proportional to the magnitude of the
103. emory The instrument powers up in the configuration it was in when the power up feature was turned off To change PUP status hold the Enter key and press the W key to toggle the PUP status between On and Off 3 14 Operation Lake Shore Model 330 Autotuning Temperature Controller User s Manual 3 5 Thermocouple Controller Operation Model 330 4X ONLY The thermocouple input option allows either Channel A Channel B or both to accommodate thermocouple sensors The controller supports Chromel AuFe 0 0796 Chromel AuFe 0 0396 E K and T thermocouples with internal curves that enable it to operate in temperature units C and K as well as voltage in millivolts The thermocouple input utilizes a secondary temperature sensor to monitor Reference Junction room temperature and provide curve compensation Disable thermocouple Reference Junction Compensation to use the Model 330 with external compensation techniques 3 5 4 Sensor Attachment Thermocouple leads attach to the terminal block by aluminum screws Tighten the terminal screws carefully Loose connections result in unstable readings and control Connect the leads with proper polarity or the input option will not operate properly The terminal block positive terminal is on the side of the V label on the back panel and should correspond with the positive thermoelement listed for each type of thermocouple 3 5 2 Thermocouple Curve Selection To choose a thermocouple curve 06 thru 1
104. emperature Controller User s Manual 6 2 1 330 51 Option The Model 330 51 is a special configuration of the Model 330 41 that allows temperature measurement and control to 1000 C with a Type K Thermocouple The Channel A input is modified to read a sensor signal of 45 mV instead of the normal x15 mV The larger input range lowers measurement resolution accordingly Below are typical specifications for the modified Channel A Channel B operates normally and conforms to the Platinum sensor specifications detailed in the Model 330 User s Manual CAUTION The Model 330 51 has a special Type K Thermocouple curve loaded in location 11 Select this curve for Channel A instead of the standard curve at location 9 Failure to use the curve in location 11 results in improper temperature or millivolts reading from the instrument causing the oven heater to burn out Curves for other thermocouples can be downloaded with a computer interface The curves must follow the CURV Command format specified in this addendum and not follow the format in the Model 330 User s Manual All thermocouple curves for this instrument are limited to 45 mV and 1273 K Use Type K to 1273 K but Type E is limited to 850 K and Type T to 670 K because of their higher sensitivities Only Type K curve is included CURV Command Format Changes To change the thermocouple response signal in millivolts to a voltage equivalent add 45 mV and multiply by 100 For example the response at 0
105. ent X Number of points for the curve usually 31 but can be up to 99 Y Units voltage or Ra see CURV Command with 1 character before the decimal and 5 after it 0 00000 Z Temperature with 3 places before the decimal point and one after it 000 0 After sending the CURV command values returned include temperature coefficient number of points and beginning and end points This is normal This extra information shows in bold in the example below 11 S10USERCURVE N 31 0 00000 499 9 0 19083 365 0 0 24739 345 0 0 36397 305 0 0 42019 285 0 0 47403 265 0 0 53960 240 0 0 59455 220 0 0 73582 170 0 0 54606 130 0 0 95327 090 0 1 00460 070 0 1 04070 055 0 1 07460 040 0 1 09020 034 0 1 09700 032 0 1 10580 030 0 1 11160 029 0 1 11900 028 0 1 13080 027 0 1 14860 026 0 1 07200 025 0 1 25070 023 0 1 35050 021 0 1 63590 017 0 1 76100 015 0 1 90660 013 0 2 11720 009 0 2 53660 003 0 2 59840 001 4 6 55360 000 0 term Remote Operation 4 21 ECUR Input Returned Remarks Example FREE Input Returned Remarks KCUR Input Returned Remarks SCAL Input Returned Remarks Example 4 22 Lake Shore Model 330 Autotuning Temperature Controller User s Manual Edit or Add A Data Point In User Curve ECUR XX Y YYYYY Z2Z2Z 7 Nothing Enter the point to be added or edited XX curve number from 11 to 31 Y YYYYY voltage and ZZZZ temperature in kelvin Data points in Curves 0
106. er case IF CMD EXIT THEN CLOSE 1 END Get out on Exit IF CMDS CURVE THEN GOTO LOAD Load a curve from disk file CMDS CMDS TERMS PRINT 1 CMDS Send command to instrument IF INSTR CMDS lt gt 0 THEN Test for query RS If query read response N 0 Clr return string and count WHILE N lt TIMEOUT AND INSTR RS TERMS 0 Wait for response INS INPUTS LOC 1 1 Get one character at a time IF INS THEN N N 1 ELSE N 0 Add 1 to timeout if no chr RS RSS INS Add next chr to string WEND Get chrs until terminators IF RS lt gt THEN See if return string is empty RSS MID RS 1 INSTR RSS TERMS 1 Strip off terminators PRINT RESPONSE RS Print response to query ELSE PRINT NO RESPONSE No response to query END IF END IF Get next command GOTO LOOP1 Remote Operation 4 23 Lake Shore Model 330 Autotuning Temperature Controller User s Manual LIkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk CURVE LOADING PROGRAM This routine will load a curve Get here by entering CURVE above NOTE SPACING OF THE DATA STRING IS VERY CRITICAL For this example the string data must be on a single line of an ASCII file using the same format as the attached sample LIkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk WK WK WK WK WK LOAD CURVES SPACE 2000 DELAY 2000 PRINT PRINT PRINT IN
107. error signal In process control nomenclature this response is described in terms of proportional control Let us examine the behavior of the sensor signal set point deviation circuit in a modern cryogenic controller the Lake Shore Cryotronics Model DRC 82C In figure 2 the amplifier output deviation gain times error is plotted against the error signal for two amplifier gains A 100 and A 1000 Gain in this closed loop system refers not to the power gain as in an audio amplifier but is related to the maximum amount of error signal allowed before the controller is directed to produce full output power The DRC 82C requires a 0 to 8 volt signal from the deviation amplifier to drive the power output stage from zero to maximum In Figure 2 For Av 1000 there is a narrow band of error signals 0 to 8 mV within which the proportional action occurs This proportional band expands tenfold for A 100 and so on for lower gains obviously gain and proportional band are inversely related Proportional band is expressed as a percentage of full scale range Note that the proportional band in mV can be converted to temperature in kelvins if the sensitivity of the sensor Variable Set Point Sensor Deviation Power Stage Amplifier Non Inverting Inverting FIGURE 1 Block diagram of Cryogenic Temperature Controller A is amplifier voltage gain Proportional Proportional 8V Band 100
108. et The Model 330 produces a service request only if bit 6 of the Service Request Enable Register is set If disabled the BUS CONTROLLER still examines Status Byte Register status reports by serial poll SPE but the Service Request cannot interrupt the BUS CONTROLLER The STB common command reads the Status Byte Register but will not clear the bits Certain bits in the Status Byte Register continually change The Standard Event Status Bit and the Status Reports for the Overload Display Data Ready and Control Data Ready continuously update to reflect current controller status The Control Channel Limit is latched set to 1 and remains latched until the Status Byte Register is read See below for Status Byte Register bit assignments These reports occur only if enabled in the Service Request Enable Register Sample Data Ready SDR Bit 0 When set a valid sample reading is available Control Data Ready CDR Bit 1 When set a valid control data reading is available Control Limit Ready CLE Bit 2 When set indicates the control sensor reading is inside the chosen limit from the setpoint The bit will not revert to zero if the reading falls back outside the chosen limit If this report is read and the control sensor reading is still inside the limit the Model 330 sets the CLE bit again Enter the control channel limit with the CLIM device dependent command Overload Indicator OVI Bit 4 When set indicates a display overloa
109. et as a function of the ac current amplitude However the ac rms voltage across the diode was chosen instead for two reasons the first of which is purely practical In many circumstances the ac voltage measurement can be made without any modifications to existing measurement systems so laboratory checks can be quickly taken and compared directly to the data presented here to give an estimate of potential temperature errors Second in the calculations using the model presented below one unknown parameter could be eliminated from the calculations by using the voltage across the diode instead of the current Figures 4 and 5 give the offset voltage as a function of the ac rms voltage across the diode for dc currents of 1 10 and 100 pA with the ac current modulation at 60 Hz The equivalent temperature error corresponding to the dc offset voltage is indicated along the right edge of the figure Figures 6 and 7 give similar plots but at a fixed 10 pA dc current with the ac current modulation at 60 1000 and 20 000 Hz The magnitude of the dc offset voltages is consistent with what has been observed in measurement systems when corrective action has been taken to eliminate noise problems Special note should be taken of the dc current independence in Fig 4 and the frequency independence in Figs 6 and 7 The data taken at 305 K have not been shown as the results are qualitatively very similar to the 77 K measurements and can be adequately described by th
110. etpoint Heater Range P 1 999 D 1 200 Off Low High HH LS Zone 06 Setpoint Heater Range P 1 999 D 1 200 Off Low High Setpoint Heater Range P 1 999 D 1 200 Off Low High Setpoint Heater Range P 1 999 D 1 200 Off Low High HH LS Zone 03 Setpoint Heater Range P 1 999 D 1 200 Off Low High Zone 02 Setpoint Heater Range P 1 999 D 1 200 Off Low High LLL Zone 01 Setpoint Heater Range P 1 999 D 1 200 Off Low High C 321 U 3 4 Figure 3 4 Record of Zone Settings 3 12 Operation Lake Shore Model 330 Autotuning Temperature Controller User s Manual 3 4 INTERFACE AND MISCELLANEOUS FUNCTIONS The following front panel keyboard functions relate to Model 330 thermometry or temperature control Baud Paragraph 3 4 1 Address Paragraph 3 4 2 Local Paragraph 3 4 3 Defaults Reset Paragraph 3 4 4 and Power Up Configuration PUP Paragraph 3 4 5 3 4 4 Baud If using the Serial Interface set the Baud rate to 300 or 1200 300 is the default Press and hold the Baud key to show the current Baud rate in the lower Control window To change the Baud rate hold the Baud key and press the W key to cycle the Baud rate between 300 and 1200 Other Serial Interface parameters are fixed see Table 4 2 3 4 2 Address Views and sets the IEEE 488 address and terminator To view the IEEE 488 address press and hold the Address key The number for the selected address appears in the upper Samp
111. f status flags Query Status Byte STB SSTB bit weighting Format nnn term 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 Query Self Test TST 0 or 1 Format n term The Model 330 performs a self test at power up 0 no errors found 1 errors found Wait to Continue WAI Nothing Prevents execution of any further commands or queries until completion of all previous ones Changing the sample sensor and reading it immediately with a device dependent query may result in a reading error because the sensor needs time to stabilize Place a WAI between the sensor change and query for a correct reading Achieve the same results with repeated queries or using a Service Request but WAI is easier Send WAI as the last command in a command string followed by appropriate termination It cannot be embedded between other commands Remote Operation 4 3 3 ADDR Input address Returned Remarks ADDR Input Returned Remarks END Input Returned Remarks END Input Returned MODE Input Returned Remarks Example MODE Input Returned TERM Input Returned Remarks Remote Operation Lake Shore Model 330 Autotuning Temperature Controller User s Manual Interface Commands Set IEEE Address ADDR address An in
112. gs and heater range Configure the zones using 01 as the lowest to 10 as the highest zone in K Copy Figure 3 4 to plan zones then use the manual to record final zone settings Paragraph 3 4 4 lists default zones Although Zone tuning can be activated from the front panel the IEEE 488 or Serial Interface is the only way to set up the zones See Paragraph 4 3 4 for ZONE and ZONE commands After zone setup place the controller in zone mode Hold the Autotune key and press the W key to cycle the display to Zone Once zone is turned on the instrument updates control settings each time the setpoint changes to a new zone If the settings are changed manually the controller uses the new setting while it is in the same zone and update to the zone table settings when the setpoint changes to a value outside that zone This feature is most effective when combined with the ramp rate feature The user can potentially ramp through all 10 zones from 1 4 K to room temperature by changing only the setpoint The controller automatically changes PID and heater range settings as the temperature setpoint passes through the different zones Operation 3 11 Lake Shore Model 330 Autotuning Temperature Controller User s Manual Zone Setting WorkSheet Setpoint Heater Range P 1 999 D 1 200 Off Low High Setpoint Heater Range P 1 999 D 1 200 Off Low High So Zone 08 Setpoint Heater Range P 1 999 D 1 200 Off Low High Zone 07 S
113. hape and distortion but the oscilloscope was removed from the circuit when actual data were recorded DVM FIGURE 3 Measurement circuit schematic diagram Data were recorded at the three dc current values of 1 10 and 100 pA with the temperature stabilized at 305 77 or 4 2 K At each temperature and dc current value the dc voltage and the ac voltage across the diode were recorded as the amplitude and frequency of the signal generator were varied The dc voltage reading across the 10 kQ standard resistor was also monitored to verify that the dc component of the current remained constant to within 0 05 In addition the IV characteristic of the diode was measured at each temperature from 0 1 to 150 pA Although detailed measurements were taken on only one diode other diodes were randomly selected and spot checked at all three temperatures and frequencies to verify consistency with the measured data The diodes tested were of the DT 500 series of Lake Shore Cryotronics Inc and have been in production long enough to have a substantial reliability and calibration history Ill RESULTS AND DISCUSSION The data were analyzed by calculating a voltage offset AV This offset is defined as the difference between the dc voltage reading across the diode when operated with an ac dc current and the dc voltage reading when operated with a pure dc current see Fig 2 At first glance the logical choice seems to be to examine the variation of this offs
114. holding Enter press the W key to cycle between On and Off On indicates that power up settings change when instrument settings are changed via the front panel or the remote interface On is the default PUP condition If left on the instrument powers up in the same configuration it powered down Off indicates power up memory updates are disabled and the instrument powers up in the same configuration as when the power up feature was turned off 2 11 3 Power Up Errors On power up the Model 330 checks internal memory There are two potential error messages The first error Er01 indicates an unsuccessful attempt to write and read the internal non volatile RAM This error is not user correctable Contact the factory The second error ErO2 indicates an unsuccessful attempt to read internal non volatile RAM for the Model ID Sometimes initializing the Model 330 memory may correct this error To initialize the memory hold both the Escape and Units keys for about 20 seconds Release once the power up sequence begins Perform this operation only under extreme circumstances it erases all user defined curves in memory 2 10 Installation Lake Shore Model 330 Autotuning Temperature Controller User s Manual CHAPTER 3 OPERATION 3 0 GENERAL This chapter covers Definition of Front Panel Controls Paragraph 3 1 Thermometry Functions Paragraph 3 2 Control Functions Paragraph 3 3 Interface and Miscellaneous Functions Paragraph
115. hromel as the positive thermoelement This thermocouple has relatively high temperature sensitivity below 25 K and usable sensitivity below 10 K It is widely used in cryogenic applications due to its relatively high thermoelectric sensitivity gt 15 uV K above 10K Recommended useful temperature range for the 0 03 Fe is 4 K to 325 K and for the 0 07 Fe is 1 4 K 2 6 Installation Lake Shore Model 330 Autotuning Temperature Controller User s Manual Type E Chromel Constantan Type E is a thermocouple pair consisting of a Ni Cr alloy Chromel as the positive thermoelement and a Cu Ni alloy Constantan as the negative thermoelement It has the highest sensitivity of the three standard thermocouples E K and T typically used for low temperature applications 8 5 uV K at 20K This thermocouple is best for temperatures down to 40 K It is recommended for oxidizing or inert environments Do not use it in sulfurous or reducing atmospheres or environments that promote corrosion Recommended useful temperature range is 3 K to 475 K Type K Chromel Alumel Type K is a thermocouple pair consisting of a Ni Cr alloy Chromel as the positive thermoelement and a Cu Al alloy Alumel as the negative thermoelement It may be used in inert environments but not in sulfurous or reducing atmospheres or environments that promote corrosion Sensitivity at 20K 4 1 p V K Recommended useful temperature range is 3 K to 575 K Type T
116. ing use Stycast epoxy instead of Apiezon N Grease In all cases periodically inspect sensor mounting to verify that good thermal contact to the mounting surface is maintained For the Model 330 2X Series PT 100 Platinum Sensors follow the same procedures for diode type sensors The difference is Platinum sensors have no lead polarity and some materials used at cold temperatures will not tolerate the high temperature range of the Platinum sensor Installation 2 5 Lake Shore Model 330 Autotuning Temperature Controller User s Manual 2 6 1 4 Measurement Errors Due To AC Noise Poorly shielded leads or improperly grounded measurement systems can introduce AC noise into sensor leads For diode sensors AC noise appears as a shift in the DC voltage measurement due to the non linear current voltage characteristics of the diode When this occurs measured DC voltage is too low and the corresponding temperature indication is high Measurement error can approach several tenths of a kelvin For Series PT 100 Platinum Sensors the noise causes no DC shift but it may still degrade accuracy To determine if this is a problem in your measurement system perform either of the two procedures below 1 Place a capacitor across the diode to shunt the induced AC currents Capacitor size depends on the noise frequency If the noise is related to the power line frequency use a 10 microfarad capacitor If AC coupled digital noise is suspected digital circuits or
117. ing Shelf for side by side mounting of two controllers see Paragraph 6 3 and Figure 6 5 2 11 POWER UP This paragraph covers the Power Up Sequence Paragraph 2 11 1 Power Up PUP Configuration Paragraph 2 11 2 and Power Up Errors Paragraph 2 11 3 2 11 1 Power Up Sequence 1 All elements of the LED display including Heater light 2 The initials for Lake Shore Cryotronics Inc LSCI appear in the top window the numbers 330 appear in the bottom window 3 The top line displays the IEEE 488 address default 12 the bottom line displays the Serial interface Baud rate default 300 4 The Sensor A input type displays in the top window see Table 2 1 while the curve number displays in the bottom window see Table 2 3 5 The Sensor B input type is displayed in the top window same as displays in Table 2 1 while the curve number is displayed in the bottom window as defined in Table 2 3 Installation 2 9 Lake Shore Model 330 Autotuning Temperature Controller User s Manual 2 11 2 Power Up Configuration The user may store a Model 330 Power Up PUP configuration so the Model 330 powers up to a user defined state after power down Retain heater range setpoint gain reset units and curve number store in non volatile memory even when the line cord is disconnected Hold down Enter for 5 seconds to display PUP status in the top window and either the words On or Off in the bottom window To change PUP status while
118. interfaces then use a capacitor between 0 1 to 1 microfarad In either case if the measured DC voltage increases there is induced noise in your system 2 Measure the AC voltage across the diode with an AC voltmeter or oscilloscope Most voltmeters do not have the frequency response to measure noise associated with digital circuits or interfaces which operate in the MHz range See the paper Measurement System Induced Errors In Diode Thermometry J K Krause and B C Dodrill Rev Sci Instr 57 4 661 April 1986 for a thorough discussion of this potential problem and the magnitude of error which may result It is available from Lake Shore To greatly reduce the potential for this error connect twisted leads pairs between the controller and the diode sensors preferably Duo Twist Cryogenic Wire which features phosphor bronze wire 32 or 36 AWG twisted at 3 15 twists per centimeter 8 twists per inch Duo Twist wire is available from Lake Shore See the Lake Shore Product Catalog or contact Lake Shore for details 2 6 2 Thermocouple Model 330 4X Connections The thermocouple input has a thermal block to connect thermocouple wires The positive and negative terminals correspond to V and V and should match the polarity of the thermocouple used Tighten the screw terminals carefully loose connections result in unstable readings and control For details on thermocouple operation see Paragraph 3 5 2 6 2 1 Thermocouple Compensa
119. irmly against the surface during curing to assure a thin epoxy layer and good thermal contact The device may be removed in the future by using the appropriate epoxy stripper The SD adpater can be soldered using a rosin flux non corrosive if extreme care is exercised First tin the base of the sensor using a low wattage temperature controlled soldering iron which will not exceed 200 C Use only a minimal amount of solder Tin the surface to which the sensor is to bonded and again avoid an excessive thickness of solder Clean both the sensor and mounting surface of any residual flux Next re heat the mounting surface to the melting point of the solder press the device into position and allow the sensor to warm to the melting point of the solder After both tinned surfaces have flowed together remove the heat source and let the sample and sensor cool Under no circumstance should the sensor be heated above 200 C and the solder must be limited to only the base of the sensor Excess solder running up the sides of the SD package can create shorts Repeated mounting and demounting of a soldered sensor may eventually cause wetting deterioration and ruin the thermal contact to the sensing element although the nickel buffer layer should minimize these problems CAUTION The preferred method for mounting the SD sensor is either the CO adapter or bonding with epoxy Lake Shore Cryotronics Inc will not warranty replace any device damaged by a user designe
120. 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 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 From Live Circuits 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 representative for service and repair to ensure that safety features are maintained 1 7 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
121. ith last data byte if enabled End Terminating characters are sent when the Model 330 completes its message transfer on output They also identify the end of an input message This command works only with the IEEE 488 Interface and does not change the serial terminators 4 13 TERM Input Returned Remarks Lake Shore Model 330 Autotuning Temperature Controller User s Manual Terminator Query TERM Returns the current terminating character type 0 Carriage return and line feed CR LF 1 Line feed and carriage return LF CR 2 Line feed LF 3 No terminating characters EOI line set with last data byte if enabled End This command works only with the IEEE 488 Interface 4 3 4 Display Commands Display commands allow the interface to act as a virtual display Transfer display data as well as format CCHN Input Returned Remarks Example CCHN Input Returned Remarks CDAT Input Returned Remarks Example CUNI Input Returned Remarks Example CUNI Input Returned Remarks 4 14 Set Control Channel to A or B CCHN A or CCHN B Nothing Sets control channel to sensor A or B Do not combine channel control unit and setpoint changes Allow one controller update cycle 72 second between these commands so the Model 330 interprets them correctly CCHN A term changes the control channel to A Control Channel Query CCHN AOrB Returns the cur
122. l Commands SDC Selective Device Clear The SDC command performs essentially the same function as the 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 SRQ Status Register This status register contains important operational information from the unit requesting service The SPD command ends the polling sequence 4 1 2 2 Common Commands Common Commands are addressed commands which 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 See Paragraph 4 3 for a list of all Model 330 common commands 4 1 2 3 Interface and Device Specific Commands Device Specific Commands are addressed commands The Model 330 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 This section discusses Common and De
123. l voltage and power gain of the controller is modified by changing the output power settings B 2 Application Notes Lake Shore Model 330 Autotuning Temperature Controller User s Manual To illustrate the effect of the sensor in more detail consider the idealized curve Figure 4 for a Lake Shore silicon diode which has a nominal sensitivity of 50 mV K below 30 kelvin and 2 5 mV K above 30 kelvin Figure 3 illustrates the effect of converting the voltage error signal horizontal axis to its equivalent temperature error for the two sensitivity regions of 2 the silicon diode sensor These curves introduce the concept of loop gain dP dT watts kelvin which includes the gain of the sensor as well as that of the deviation amplifier and power output stage As the transition in temperature 1 from above 30 kelvin to below 30 kelvin is made the loop gain is increased by a factor of 20 because of the increased sensitivity of the silicon diode thermometer Because of noise and thermal phase lag the deviation amplifier gain will normally have to be reduced by the same factor so that the 100 200 300 loop gain remains relatively constant 50 mV kelvin 2 5 mV kelvin Temperature kelvin In order to maintain any desired temperature above that of FIGURE 4 Idealized curve for Lake Shore Cryotronics Inc DT the cryogen in a cryogenic system of course some level of 500 Series silicon diode temperature sensors heater powe
124. lability is better than 2 mK With diodes there is no need for a sensor pre amplifier which would precede the set point control and deviation amplifier However in the case of resistance thermometers including both semiconductor and metal types a pre amplifier becomes necessary In a dc measurement system such as is used in the DRC 82C it is sometimes possible to obtain temperature control stability with resistance thermometers superior to that obtainable with diodes This requires a highly stable and adjustable constant current source in addition to a pre amplifier designed for very low noise and drift The choice of sensor is not at all obvious it depends on many factors besides sensitivity including sensor size time response power dissipation magnetic field dependence and temperature range In the less common case of cryogenic thermocouples the very low sensitivity 10uV K requires quite large pre amplifier gains and a stable reference junction arrangement Thermocouples are sometimes used when sensor size or time response are more important than temperature stability and accuracy At cryogenic temperatures thermocouple accuracy does not approach that of a semiconductor diode or resistance thermometer when either are properly installed VII ANALOG VERSUS DIGITAL CONTROL In this day of computers designing digital instrumentation with a microprocessor is definitely in vogue In a digital control system the sensor voltage is digitized by
125. le under the CURV command When entering omit temperature coefficient number of points and endpoints The Model 330 determines and stores whether the curve is a positive or negative coefficient curve Based on temperature coefficient the Model 330 then stores the curve end points and also adds the number of points GaAlAs Diode No conversion necessary 0 00000 to 6 00000 Platinum Resistance Input range is 0 00 to 299 99 Q 0 00 Q looks like 0 00000 and 299 99 Q looks like 2 99990 0 01 times R Thermocouple Millivolts Input range is 15 to 15 Add 15 mV to make all positive 0 30 mV and multiply by 100 to make look like 0 3 00000 V For example a thermocouple voltage of 5 0000 mV would be entered as 1 00000V To aid in automated loading of User Curves for Serial Interface users see the QuickBASIC Curve Loading Program in Paragraph 4 4 Curve Number Information Query CURV XX AA SBO CCCCCCCCCCCCCCC D XX Y YYYYY ZZZ Z2 User must provide curve number 00 thru 31 with query The unit will return header line and all point information for that curve as follows A Curve number from 11 to 31 S For the Model 330 the first character must be the letter S B Setpoint Limit 0 325 K 1 375 K 2 475 K 3 800 K 4 999 K 0 Fixed Character 0 for all curves except 9 for thermocouples C 15 character curve description D Temp coefficient N negative coefficient P positive coeffici
126. le window The default address is 12 To change the IEEE 488 address hold the Address key and press the A key to cycle through the addresses Release when you reach the desired address To view the IEEE 488 communication terminators press the Address key The symbol for the terminators appears in the lower Control window The four terminators are CrLf Carriage Return Line Feed LfCr Line Feed Carriage Return Lf Line Feed End No Terminator EOI line set with last data byte if active To change the IEEE 488 terminators hold the Address key and press the W key to cycle through the terminators Release when you reach the desired terminator Change all other IEEE 488 interface parameters with computer interface commands described in Chapter 4 3 4 3 Local Toggles the instrument between Remote computer controlled operating mode and Local front panel controlled operating mode This can be locked out by the IEEE 488 interface see Paragraph 4 1 Local Mode is the normal operating mode Front panel control is fully active Operating in Local Mode does not disable interface activity In Remote Mode the controller is under remote interface control and the front panel keys are disabled 3 4 4 Instrument Reset and Factory Default Settings To reset the controller to factory default settings press and hold the Escape and Units keys for 20 seconds CAUTION The controller erases all User or SoftCal Curves and Zone Settings when it is initi
127. ller you will need the following Digital Multimeter DMM with a 472 digit display and capable of 4 lead resistance measurement Test connector wired as follows 3 I 4 V RrEsT 1000 Q 2 CV 1 4 This is the connection for a resistive sensor Res should be nominal 1000 Q with temperature as stable as possible 20 50 ppm C WARNING To avoid potentially lethal shocks refer procedure below to qualified personnel Follow the REMOVE TOP procedure in Paragraph 5 6 Select the PT input switch for both inputs A and B See Table 5 1 Turn off the heater Allow the controller to warm up for 1 hour Measure and note resistance of the Rs connector to 4 places with a 4 lead measurement Put the test connector in Channel A and attach the multimeter in DC Voltage mode across Rs SR 9 7M ic Adjust Channel A current source with trim potentiometer R21 until current through Res is 1 mA For example for a 1000 0 Q resistor the voltage should read 1 0000 V For a 1002 5 Q resistor the voltage should read 1 0025 V 8 Repeat steps 6 and 7 for Channel B except adjust R25 9 Connectthe negative lead of the multimeter to TP1 and the positive lead to TP2 10 Adjust R10 until the voltage reads 2 5000 VDC 11 Place the test connector back on Channel A 12 Short across Rs for Zero Calibration 13 Configure the Model 330 to display Channel A in ohms Q 14 Adjust R6 until the display reads 0 000 Q toggles to error
128. ller User s Manual NOTES Remove and discard two screws above front fan slots Replace with two longer screws Item 2 The tabs on the front mounting bracket Item 3 will slide into corresponding fan slots on the controller to the left The bracket must be mounted to the controller on the right to avoid interfering with fan operation The Model RM 3H2 is the basic Rack Mounting Kit The Model RM 3H2 H adds the two handles Item 6 and associated screws Item 7 Item Description P N Qty 1 Rack Mount Ear 107 049 2 Screw 6 32 x 1 2 Inch 0 035 6 FHMS Phillips 3 Front Locking Bracket 107 042 1 4 RearLocking Bracket 107 043 2 5 Screw 6 32 x 3 8 inch 0 043 4 PHMS Phillips Additional Parts for Model RM 3H2 H 6 Rack Mount Handle 107 433 2 7 Screw 8 32 x 3 8 inch 0 081 4 FHMS Phillips Figure 6 5 Model RM 3H2 H Dual Rack Mount Kit 6 6 C 330 U 6 5 Options and Accessories Lake Shore Model 330 Autotuning Temperature Controller User s Manual APPENDIX A CURVE TABLES Table A 1 Standard Diode and Platinum Curves Breakpoint PLATINUM 100 OHM e Q Equiv 0 00000 0 00000 0 00000 0 00000 0 19083 0 28930 0 09032 0 03820 0 24739 0 36220 0 12536 0 04235 0 36397 0 41860 0 18696 0 05146 0 42019 0 47220 0 29958 0 05650 0 47403 0 53770 0 42238 0 06170 0 53960 0 59260 0 56707 0 06726 0 59455 0 73440 0 68580 0 07909 0 73582 0 84490 0 76717 0 09924 0 84606 0 92570 0 83541 0 12180 0 95327 0 99110 0 89082
129. llivolt display resolution is 1 microvolt 3 3 2 2 Resistance Resolution Model 330 2X Only Resistance mode is allowed for the Platinum Resistor input configuration The display resolution in resistance is 0 01 Q below 200 Q and 0 1 Q above 200 Q 3 3 3 Ramp The ramping feature allows the user to set the rate at which the temperature setpoint increases or decreases when the user changes the setpoint The ramp rate range is from 0 1 to 99 9 degrees per minute Ramp only works if the controller reads in temperature units K or C Setting to 0 turns the ramp function off For example to change the setpoint from 50 K to 100 K ata rate of 1 k min press and hold the Set Point key The display to the right appears Use the numeric keypad to enter the ramp rate of 1 0 Press Enter to accept the new ramp rate and display the normal display Press Setpoint and use the numeric keypad to enter 100 K The display slowly changes to 100 K at a rate of 1 K per minute reaching 100 K in 50 minutes To stop the ramp at any point press Setpoint followed by Enter 3 3 4 Autotune There are three Model 330 automatic tuning modes Auto P Auto PI and Auto PID The Autotuning algorithm determines proper settings for Gain Proportional Reset Integral and Rate Derivative by observing system time response upon changes in setpoint under either P PI or PID control Adaptation of an Autotuning algorithm for use at cryogenic temperatures is more
130. lowed in a system is 2 meters for each device on the bus or 20 meters maximum A system may be composed of up to 15 devices Figure 5 5 shows the IEEE 488 Interface connector pin location and signal names as viewed from the Model 330 rear panel IEEE 488 INTERFACE SH1 AH1 T5 L4 SR1 RL1 PPO DCH DTO CO E1 12 11 10 9 8 7 6 5 4 3 2 1 24 23 22 21 20 19 18 17 16 15 14 13 PIN SYMBOL 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 Not Data Accepted Interface Clear Service Request Attention Cable Shield Data Input Output Line 5 Data Input Output Line 6 Data Input Output Line 7 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 Qo JO Om P GO Figure 5 5 IEEE 488 Rear Panel Connector Details Service amp Calibration 5 3 Lake Shore Model 330 Autotuning Temperature Controller User s Manual 5 5 OPTIONAL SERIAL INTERFACE CABLE AND ADAPTERS To aid in Serial Interface troubleshooting Figures 5 6 thru 5 8 show wiring information for the optional cable assembly and the two mating adapters T ES T TxD YELLOW N lt Gnd GREEN
131. ltage with Optional Model 3003 Heater Output Conditioner heater noise is lowered by 20 dB Two 4 5 digit LED Temperature in K or C Sensor units in volts 330 1X amp 3X ohms 330 2X or millivolts 330 4X Shared with control sensor 20 digit LED bar graph percent of full scale current for range Channel units heater range interface mode 0 01 below 200 0 1 above Refer to Table 1 1 Numeric plus special function Complies with IEEE 488 2 SH1 AH1 T5 L4 SR1 RL1 PPO DC1 DTO CO E1 300 or 1200 baud RJ 11 connector RS 232C electrical standard 20 to 30 C 68 F to 86 F or with reduced accuracy in range 15 C to 35 C 59 F to 95 F 110 120 220 240 VAC 5 10 50 or 60 Hz 135 Watts 217 mm x 90 mm x 419 mm 8 5 x 3 5 x 16 5 half rack package 5 kilograms 11 pounds User configurable with IEEE 488 or Serial Interface only Introduction Lake Shore Model 330 Autotuning Temperature Controller User s Manual Power Supply Channel 4 Lead A Sensor IEEE 488 Interface RS 232C Interface Channel B Converter 16 Bits Heater Output 25 W or 50 W RAM for Curves Isolation electrical refers to the separation of voltage supplies within the instrument The 330 design isolates heater output measurement and digital interface circuitry Converter 15 Bits C 330 U 1 2 Figure 1 2 Model 330 Block Diagram 1 2 CONTROL FUNDAMENTALS AND AUT
132. lue of the coefficient This property makes it easy to determine the contribution of each term to the temperature calculation and where to truncate the series if full accuracy is not required Program 1 BASIC Subroutine to evaluate temperature Program 2 BASIC Subroutine to evaluate temperature T from the Chebychev series using Equations 1 and 3 T from the Chebychev series using Equations 1 and 4 An array Tc Ndegree should be dimensioned ACS is used to represent the arccosine function 100 REM Evaluation of Chebychev series 100 REM Evaluation of Chebychev series 110 X V VL VU V VU VL 110 X V VL VU V VU VL 120 Tc 0 1 120 T 20 130 Tc 1 e x 130 FOR I 0 to Ndegree 140 T A O A 1 X 140 T T A I COS I ACS X 150 FOR I 2 to Ndegree 150 NEXT I 160 Tc I 2 X Tc I 1 Tc I 2 160 RETURN 170 T T A I Tc I 180 NEXT I 190 RETURN Table 1 Chebychev Fit Coefficients 2 0 K to 12 0 K 12 0 K to 24 5 K 24 5 K to 100 0 K 100 K to 475 K VL 1 32412 VL 1 32412 VL 1 32412 VL 1 32412 VU 1 69812 VU 1 69812 VU 1 69812 VU 1 69812 A 0 7 556358 A 0 17 304227 A 0 71 818025 A 0 287 756797 A 1 5 917261 A 1 7 894688 A 1 2 53 799888 A 1 194 144823 A 2 0 237238 A 2 0 453442 A 2 1 669931 A 2 3 837903 A 3 0 334636 A 3 0 002243 A 3 2 314228 A 3 1 318325 A 4 0 058642 A 4 0 158036 A 4 1 566635 A 4 0 109120 A 5 0 019929 A 5
133. lve low level signals and hence require a low noise background For that reason ripple free direct current usually controlled by a series transistor bank should be used to power the heater 4 Asone traverses the cryogenic regime from the liquid helium range up towards room temperature there can be quite large variations in both the thermal time constants and thermometer sensitivities 5 nthe case of the furnace in which the load does not experience large endo or exothermic reactions the heat input required to maintain a set point temperature is approximately constant This is because the heat loss through a fixed thermal conductance to the room temperature environment outside the furnace is also constant However there are cryogenic systems where the low temperature environment provided by e g a surrounding cryogen such as a liquid helium or liquid nitrogen bath may vary drastically as the level of the cryogen changes In addition the thermal conductance to the outside world is highly dependent on the gas pressure vacuum maintained in the cryostat The resulting variations in cooling power will cause the heat input requirements to be anything but constant A few cryogenic systems employ a controller cooling loop but this type of system will not be discussed Most of the difficulties in cryogenic control applications are associated with factors 4 and 5 where changes in parameters are involved Application Notes B 1 Lake Shore Mod
134. mally between 1 4 and 1 8 the reset time constant if it is used at all Start with settings of either 0 50 or 100 and determine which setting yields the desired control Don t be surprised if the preference for your system is 0 OFF Because it is a percent of reset time constant rate scales automatically with changes in the reset value and does not have to be revisited frequently 3 3 5 4 Effect of Temperature on Tuning Parameters As temperature increases system gain normally increases Consequently if sensor sensitivity is relatively constant you can normally increase the controller gain with increasing temperature System gain is a product of controller gain and sensor gain For example for a silicon diode at 25 K the sensor sensitivity dV dT is approximately an order of magnitude larger than it is at 35 K If load parameters do not change greatly neither does system gain Therefore increase controller gain to compensate for the reduction in sensor sensitivity Usually system time response slows down as temperature increases Therefore after determining a valid reset at a particular temperature increasing the temperature decreases the reset value which in turn increases the time constant Conversely decreasing temperature increases the reset value which in turn decreases the time constant 3 3 6 Zone Setting The Model 330 allows up to 10 custom temperature zones where the controller automatically uses pre programmed PID settin
135. ment System Induced Errors in Diode Thermometry Review of Scientific Instruments 57 4 661 665 Available on request from Lake Shore Cryotronics Inc Sparks L L 1983 Temperature Strain and Magnetic Field Measurements In Materials at Low Temperatures Ed By R P Reed and A F Clark American Society of Metals Metals Park 515 571 White G K 1979 Experimental Techniques in Low Temperature Physics Clarendon Press Oxford Application Notes B 13 Lake Shore Model 330 Autotuning Temperature Controller User s Manual MEASUREMENT SYSTEM INDUCED ERRORS IN DIODE THERMOMETRY by John K Krause and Brad C Dodrill Diode temperature sensors are capable of being used at the accuracy level of a few hundredths of a kelvin However in order to achieve this performance proper measurement techniques must be used Poorly shielded or improperly grounded measurement systems can introduce ac noise which will create an apparent shift in the dc voltage reading across a diode sensor This results in a temperature measurement error which may approach several tenths of a kelvin The presence of the ac noise in question is not obvious during normal usage and several quick tests are outlined to verify whether or not a noise problem exists Experimental data and derivations from theoretical p n junction characteristics are given which correlate the ac noise level with possible voltage temperature measurement errors These results can be used in estima
136. mmand to instrument IF INSTR CMD lt gt 0 THEN Test for query RS If query read response N 0 Clr return string and count WHILE N lt TIMEOUT AND INSTR RS TERMS 0 Wait for response INS INPUTS LOC 1 1 Get one character at a time IF INS THEN N N 1 ELSE N 0 Add 1 to timeout if no chr RS RSS INS Add next chr to string WEND Get chrs until terminators IF RS lt gt THEN See if return string is empty RS MIDS RSS 1 INSTR RS TERMS 1 Strip off terminators PRINT RESPONSE RS Print response to query ELSE PRINT NO RESPONSE No response to query END IF END IF Get next command GOTO LOOP1 Remote Operation Lake Shore Model 330 Autotuning Temperature Controller User s Manual 4 3 EEE 488 SERIAL INTERFACE COMMAND SUMMARY The IEEE 488 Serial Interface commands are listed alphabetically in function order There are five command groups Common Commands Paragraph 4 3 2 Interface Commands Paragraph 4 3 3 Display Commands Paragraph 4 3 4 Control Process Commands Paragraph 4 3 5 and Curve Commands Paragraph 4 3 6 The commands are listed in the same order as shown below Command Function Command Function Common Commands Control Process Commands CLS Clear Interface CLIM Control Limit ESE Set Std Event Status Enable CLIM Control Limit Query ESE Query Std Event Status Enable GAIN Set Gain ESR Query Std Event Status Register GAIN Gain Query
137. mmand transmits to the instrument and the MPS receives and displays the response If no query is sent the instrument responds to the last query received Type EXIT to exit the program NOTE The INPUT instruction accepts no commas as part of an input string If a comma appears in an instrument command replace it with a space REM INCLUDE c gpib pc qbasic qbdecl bas Link to IEEE calls CLS Clear screen PRINT IEEE 488 COMMUNICATION PROGRAM PRINT CALL IBFIND dev12 DEV12 Open communication at address 12 TERMS CHR 13 CHR 10 Terminators are lt CR gt lt LF gt INS SPACES 2000 Clear for return string INPUT ENTER COMMAND or EXIT CMDS Get command from keyboard CMD UCASES CMD Change input to upper case IF CMD EXIT THEN END Get out on Exit CNDS CMDS TERMS CALL IBWRT DEV12 CMD Send command to instrument CALL IBRD DEV12 INS Get data back each time ENDTEST INSTR INS CHR 13 Test for returned string IF ENDTEST gt 0 THEN String is present if CR is seen INS MIDS INS 1 ENDTEST 1 Strip off terminators PRINT RESPONSE IN Print return string ELSE PRINT NO RESPONSE No string present if timeout END IF GOTO LOOP2 Get next command Remote Operation 4 5 Lake Shore Model 330 Autotuning Temperature Controller User s Manual National Instruments Primary GPIB Address Secondary GPIB Address Timeout setting Terminate Read on EOS Set EOI with EOS o
138. ms in four wire measurements Lead wires should also be thermally anchored at several temperatures between room temperature and cryogenic temperatures to guarantee that heat is not being conducted through the leads to the sensor A final thermal anchor at the sample itself is a good practice to assure thermal equilibrium between the sample and temperature sensor Note that the CU CY BO and DI mounting adapters serve as their own sample thermal anchor If the connecting leads have only a thin insulation such as Formvar or other varnish type coating a simple thermal anchor cn be made by winding the wires around a copper post or other thermal mass and bonding them in place with a thin layer of GE 7031 varnish There are a variety of other ways in which thermal anchors can be fabricated and a number of guidelines which may be found in detail in the references given below SENSOR MOUNTING General Comments Before installing the DT 470 sensor identify which lead is the anode and which lead is the cathode by referring to the accompanying device drawings Be sure that the lead identification remains clear even after installation of the sensor and record the serial number and location The procedure used to solder the connecting leads to the sensor leads is not very critical and there is very little danger in overheating the sensor If for some reason the leads have to be cut short they should be heat sunk with a copper clip or needle nose pliers befo
139. mum power settings 0 1 K for a 50 watt setting 0 32 for a 5 watt setting and 1 0 for the 0 5 watt setting As expected the temperature offsets become smaller as the loop gain increases However there are limits to this approach as we move from the idealized example to a real system The Real World Unfortunately the thermal conductivity within a system is not infinite and both it and the heat capacity may vary by several orders of magnitude between 1 K and 300 K Also the controller the sensor the sensor leads and the block may all have electrical noise This noise is amplified by the controller for a high enough amplifier gain setting the output of the controller will become unstable and oscillate In addition the placement of the sensor with respect to the heater and the sensor construction and mounting itself introduce thermal lags This is due to the finite thermal conductivity of the block and the thermal resistances between the heater sensor and the block These thermal lags introduce a phase shift between the controller output and the sensor which will reduce even further the gain at which the system will be stable Therefore the thermal block design is extremely important in the proper performance of any cryogenic system No controller can make up for poor thermal design of the system nor can good design overcome the inherent limiting properties of the materials and sensor packages which are currently available Application Note
140. n Writes Type of compare on EOS EOS byte Send EOI at end of Write System Controller Assert REN when SC Enable Auto Serial Polling Enable CIC Protocol Bus Timing Parallel Poll Duration Use this GPIB board Base I O Address Fl Help F6 Reset Value National Instruments Primary GPIB Address Secondary GPIB Address Timeout setting Serial Poll Timeout Terminate Read on Set EOI with EOS on Writes Type of compare on EOS EOS byte Send EOI at end of Write Enable Repeat Addressing Fl Help F6 Reset Value F9 GPIBO Configuration GPIB PC2 2A Ver 2 1 TSelect the primary GPIB address by E using the left and right arrow keys This address is used to compute the talk and listen addresses which identify the board or device on the GPIB Valid primary addresses range from 0 to 30 00H to 1EH Adding 32 to the primary address forms the Listen Address LA Adding 64 to the primary address forms the Talk Address TA EXAMPLE Selecting a primary address of 10 yields the following 10 32 42 Listen address 10 64 74 Talk address Return to Map Ctl PgUp PgDn Next Prev Board DEV12 Configuration GPIB PC2 2A Ver 2 1 T Select the primary GPIB address by using the left and right arrow keys This address is used to compute the talk and listen addresses which identify the board or device on the GPIB Valid primary addresses range from 0 to 30 00H to 1EH Adding 32 to
141. n the packing slip Installation 2 1 Lake Shore Model 330 Autotuning Temperature Controller User s Manual 2 3 DEFINITION OF REAR PANEL CONNECTIONS The Model 330 rear panel consists of the power and fuse assembly IEEE 488 Interface Connector Serial UO Connector two Sensor Input connectors and Heater Output Connections CAUTION Verify the AC Line Voltage shown in the fuse holder window corresponds to that marked on the rear panel and that both settings are appropriate for the intended AC power input Remove and verify the proper fuse is installed before inserting the power cord and turning on the instrument Always turn off the instrument before making any rear panel connections This is especially critical when making sensor to instrument connections HEATER OUTPUT 000 IEEE 488 INTERFACE CHANNEL A CHANNEL B SHI AHI T5 SR1RL1PPODCIDTocoE1 SERIAL UO aes E T des D Figure 2 1 Typical Model 330 Rear Panel C 330 U 2 1 Power and Fuse Assembly The power and fuse assembly is the entry point for AC power to the unit The assembly consists of the power line jack the power switch and the fuse holder The line cord plugs into the power line jack The power switch turns the unit on and off The fuse holder contains a 2 A 3AG Slow Blow fuse for 90 125 VAC or a 1 A 3AG Slow Blow fuse for 210 250 VAC See Paragraph 5 2 for changing power settings and fuse rating IEEE 488 Interface Connector The sta
142. nd error since the last reading Controller unable to interpret a command due to syntax error unrecognized header or terminators or unsupported command Execution Error EXE Bit 4 Set to indicate an execution error Occurs when the controller is given a task outside its capabilities Remote Operation 4 3 Lake Shore Model 330 Autotuning Temperature Controller User s Manual Device Dependent Error DDE Bit 3 Set to indicate a device dependent error Determine the actual device dependent error by executing the various device dependent queries Query Error QYE Bit 2 Set to indicate a query error Rare Involves data loss due to full output queue Operation Complete OPC Bit 0 This bit is generated in response to the xOPC common command It indicates when the Model 330 has completed all selected pending operations 4 1 4 Example IEEE Setup and Program Below is an example of how to setup and run a simple program using the built in Model 330 IEEE 488 Interface It does not reflect every hardware software configuration found in the field This example uses the National Instruments GPIB PCII IIA card and QuickBasic 4 0 or 4 5 on a PC compatible 4 1 4 1 GPIB Board Installation Install GPIB PCII IIA card using National Instruments instructions Install NI 488 2 software for DOS Version 2 1 1 was used for the example Verify that config sys contains the command device gpib pc gpib com Reboot the computer
143. ndard 24 pin connector connects the controller to any computer equipped with a IEEE 488 Interface Refer to Paragraph 4 1 for further information Serial UO Connector Accepts a standard RJ 11 telephone connector to connect to the user s computer The optional Model 2001 RJ 11 to RJ 11 10 foot Cable Model 2002 RJ 11 to DB 25 Adapter and Model 2003 RJ 11 to DE 9 Adapter are available accessories from Lake Shore refer to Chapter 6 for details Refer to Paragraph 4 2 for setup and Serial I O commands Channel A and B Sensor Input Connectors Connect up to two temperature sensors to the unit Always turn off the unit before connecting sensors Refer to Paragraph 2 6 for details on sensor input setup Heater Output Connections Banana jacks provide HI LO and GND heater connections Refer to Paragraph 2 10 for details on heater connection setup 2 2 Installation Lake Shore Model 330 Autotuning Temperature Controller User s Manual 2 4 SENSOR INPUT SETTINGS To configure sensor input type set DIP switches S1 and S2 on the main PCB inside the unit To check DIP switch settings press Input Type Input configurations are shown in Table 2 1 To change the DIP Switch settings refer to Paragraph 5 9 Switch diodes and resistor sensors in the field with no recalibration Thermocouple sensors cannot be exchanged in the field but compensation can be turned on or off with the Input Type key Table 2 1 Sensor Input Setup Display When DIP Switch
144. near interpolation between calibration data points 1 4 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 volts 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 volts cannot be seen felt or heard 1 4 1 Identification of Electrostatic Discharge Sensitive Components Below are various industry symbols used to label components as ESDS o Bee 1 4 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 i
145. ns will be discussed and examples given of its operation and adjustment While the emphasis will be placed on analog control systems the advantages and disadvantages of digital versus analog control will also be presented II CHARACTERISTICS OF CRYOGENIC TEMPERATURE CONTROL SYSTEMS The adjective cryogenic as applied to temperature control systems defines a set of conditions that distinguishes such systems from those for which the great majority of applications exist i e industrial processes in which temperatures are above and often well above room temperature There are at least five factors which crucially affect temperature control performance when one compares a cryogenic system with that existing inside a furnace for example 1 The values of heat capacity lower Cp and thermal conductivity often higher x are such that much shorter thermal time constants t o Cp x are the rule at low temperatures 2 The temperature sensor used in a furnace is almost always one of a variety of thermocouples with sensitivities in the 10 100uV C range In the cryogenic regime resistance thermometers both metallic and semi conductive diode and capacitance thermometers provide from one to three order of magnitude higher sensitivity 3 The heat input for furnaces is almost always derived from a line frequency source and is controlled by relays variable transformers saturable reactors or SCRs Experiments performed in a cryostat usually invo
146. nsors Curve 10 14 800 PT DIN Platinum DIN Curve 43760 2 475 DT 470 DT 400 Series Sensors Curve 10 Reserved 1 4 325 AuFe07 AuFe 0 07 vs Chromel 4 325 f AuFe03 AuFe 0 03 vs Chromel 3 425 Type E 3 525 f Type K 3 485 Type T User Defined Curves or Precision Option Calibrations Increased resolution more data points version of Curve 10 Used by the Model 330 to generate a SoftCal Curve Values are for thermocouples with compensation Uncompensated the thermocouple can use the full 15 mV range 3 4 Operation Lake Shore Model 330 Autotuning Temperature Controller User s Manual 3 2 7 SoftCal SoftCal improves the accuracy of a DT 400 Series Silicon Diode Sensor It enables the user to reduce the error between a silicon diode and the Standard Curve 10 which the controller uses to convert diode input voltage to a corresponding temperature In short SoftCal generates inexpensive calibrations for Model 330 DT 400 Series sensors The Lake Shore DT 400 Series Sensors incorporate remarkably uniform sensing elements that exhibit precise stable and repeatable temperature response in the range from 2 K to 475 K They exhibit excellent uniformity from device to device and as a result are routinely interchanged with one another This diode feature makes SoftCal possible For the DT 400 Series diodes five tolerance bands of tracking accuracy are available see Figure 3 3 Band 11 sensors offer absolut
147. o add remaining points one at a time up to a maximum of 97 points The entry format is as follows A 7 Curve number from 11 to 31 00 to 10 are reserved and cannot be changed or deleted S For the Model 330 the first character must be the letter S B Setpoint Limit 0 325 K 1 375 K 2 475 K 3 800 K 4 999 K 0 For the Model 330 the third character should be the number 0 C Curve description Must be at least 1 character More than 15 characters is ignored D First voltage or resistance lowest units value E First temperature Y Last voltage or resistance highest units value Z Last temperature Input data points with the units value first in ascending order The points must be a continuous string with no extra spaces or terminators The value is voltage or Rs with one character before the decimal place and five after it 0 00000 The table below gives the conversion of raw units into the format required The Model 330 automatically fills in leading and trailing zeros The second value is the temperature with three characters before the decimal point and one after it 000 0 After all or both for Serial points are input placement of an terminates the sensor curve input Remote Operation Lake Shore Model 330 Autotuning Temperature Controller User s Manual CURV continued CURV Input Returned Remarks Example To view a typical output after using this command see the examp
148. of a command string to confirm command execution For example CUNI K CUNI commands the Model 330 to set the temperature units to kelvin then return the temperature units to confirm the change The term free field indicates that the decimal point is a floating entity and can be placed at any appropriate place in the string of digits Leading zeros and zeros following a decimal point are unneeded in a command string but they are sent in response to a query A leading is not required but a leading is required term indicates where the user places terminating characters or where they appear on a returning character string from the Model 330 4 4 Remote Operation Lake Shore Model 330 Autotuning Temperature Controller User s Manual Table 4 1 Sample BASIC IEEE 488 Interface Program IEEEEXAM BAS EXAMPLE PROGRAM FOR IEEE 488 INTERFACE This program works with QuickBasic 4 0 4 5 on an IBM PC or compatible The example requires a properly configured National Instruments GPIB PC2 card The REM SINCLUDE statement is necessary along with a correct path to the file QBDECL BAS CONFIG SYS must call GPIB COM created by IBCONF EXE prior to running Basic There must be QBIB QBL library in the QuickBasic Directory and QuickBasic must start with a link to it All instrument settings are assumed to be defaults Address 12 Terminators CR LF and EOI active To use type an instrument command or query at the prompt The co
149. ol Units to kelvin units TER COMMAND CUNI Control Units Query Controller returns appropriate unit where K kelvin ZZ Aw B COMMAND CDAT Sensor Data Query Controller returns appropriate sensor reading o Z A d ad Ed S bi Di 3 COMMAND TUNE 3 Set Autotuning Status Controller sets Autotuning to PID R COMMAND TUNE Autotuning Status Query Controller returns appropriate setting where 0 Manual 1 P 2 Pl and 3 PID ENTER COMMAND RANG 0 RANG Combination command Sets heater to off and requests heater status where 0 off and 1 on E D Z H ENTER COMMAND 4 2 3 Notes on Using the Serial Interface To chain commands together insert a semi colon between them Multiple queries cannot be chained Queries generally use the same syntax as the associated setting command followed by a question mark They usually return the same information that is sent Add a query to the end of a command string to confirm command execution For example CUNI K CUNI commands the Model 330 to set temperature units to kelvin then requests the Model 330 return the temperature units to confirm the change Acorrectly spelled query without a returns nothing Misspelled commands and queries are ignored When the term free field is used it indicates that the decimal point is a floating entity and can be placed at any appropriate place in the string of digits Leading zer
150. om operating on changes in the set point such as in temperature seep applications Fortunately most sweeping is done slowly enough so as to be unaffected by typical rate time constants To determine the rate control setting in seconds for a system an abrupt increase in power is applied to the system while in equilibrium The time delay is then observed to the start of the resulting temperature increase as indicated by the control sensor This delay corresponds to the value to be set on the rate control Application Notes B 5 Lake Shore Model 330 Autotuning Temperature Controller User s Manual VI SENSOR CONSIDERATIONS Sensor Gain Revisited Since a controller will amplify input noise as well as sensor signal it becomes important to consider sensor performance when designing a complete system The Lake Shore DT 500 Series Sensors have a voltage temperature characteristic which lend themselves to cryogenic temperature control use because of their high sensitivity at low temperatures Figure 3 Coupled with this sensitivity is an extremely low noise level which results in part from assembly techniques used for all DT 500 Sensors which comply with the relevant portions of MIL STD 750C It is therefore possible to obtain short term control at low temperatures which can approach 0 1 mK in specially designed Systems such as the Lake Shore calibration facility Even above 30 K where the sensitivity is reduced by a factor of 20 short term control
151. oooouo9 o MOORROM OBOGU ARBSSSAONSS OoOoooooonuoo o SEET EEN SES ooooooooo o OBNODABRWN A 2 Appendix A Lake Shore Model 330 Autotuning Temperature Controller User s Manual APPENDIX B APPLICATION NOTES B1 0 GENERAL This appendix includes these Lake Shore Applications Notes 1 Fundamentals For Usage Of Cryogenic Temperature Controllers Application Note Page B 1 2 Standard Curve 10 Technical Data eene nennen Page B 8 3 DT 470 Series Temperature Sensors Installation and Operation Application Note Page B 10 4 Measurement System Induced Errors In Diode Thermometry Article Reprint Page B 14 FUNDAMENTALS FOR USAGE OF CRYOGENIC TEMPERATURE CONTROLLERS by Dr John M Swartz Lake Shore Cryotronics Lawrence G Rubin MIT National Magnet Laboratory 575 McCorkle Blvd Westerville OH 43082 170 Albany St Cambridge MA 02139 INTRODUCTION Cryogenic temperature controllers have been available for years but users often have an incomplete understanding of their operating principles and of the closed loop interactions between the controller and the controlled low temperature environment The object of this primer is to address this problem by presenting some fundamental and practical concepts of control at low temperatures The so called three mode or PID controller utilizing Proportional gain Integral reset and Derivative rate functio
152. or cables whenever possible Attach shields to the input connector shield pin Do not attach the shield at the sensor end The heater output is isolated from earth ground To prevent heater noise coupling into the measurement do not allow the heater output to contact earth ground The rear panel earth ground GND is for shielding only Model 330 digital logic ties directly to earth ground for interface communications Separate sensor lines and digital communication lines whenever possible to prevent excess noise in the measurement Installation 2 3 Lake Shore Model 330 Autotuning Temperature Controller User s Manual 2 6 SENSOR INSTALLATION This paragraph covers general sensor installation recommendations See the Lake Shore Product Catalog or Sensor Guide for installation details and sensor specifications Call Lake Shore for copies of application notes or questions concerning sensor installation General recommendations include 1 Thermally anchor the sensor 2 Do not ground the sensor 3 Shield the leads and connect the shield wire to SHIELD pin only Do not connect shield at the other end of the cable 4 Keep leads as short as possible 5 Use twisted pair wire preferably Lake Shore Duo Twist wire or equivalent for two wire or Quad Twist wire or equivalent for four wire applications 6 Thermally anchor lead wires See Paragraph 2 7 1 for installing Diode Model 330 1X and Platinum Model 330 2X sensors Paragr
153. os and zeros following a decimal point are unneeded in a command string but they are sent in response to a query A leading is not required but a leading is required term indicates where the user places terminating characters or where they appear on a returning character string from the Model 330 4 8 Remote Operation Lake Shore Model 330 Autotuning Temperature Controller User s Manual Table 4 3 Sample BASIC Serial Interface Program SEREXAM BAS EXAMPLE PROGRAM FOR SERIAL INTERFACE This program works with QuickBasic 4 0 4 5 or Qbasic on an IBM PC or compatible with a serial interface It uses the COM1 communication port at 1200 BAUD Enter an instrument command or query at the prompt The command transmits to the instrument which displays any query response Type EXIT to exit the program NOTE The INPUT instruction in this example accepts no commas as part of an input string If a comma appears in an instrument command replace it with a space CLS Clear screen PRINT SERIAL COMMUNICATION PROGRAM PRINT TIMEOUT 2000 Read timeout may need more BAUDS 1200 TERMS CHR 13 CHR 10 Terminators are lt CR gt lt LF gt OPEN COM1 BAUDS O 7 1 RS FOR RANDOM AS 1 LEN 256 LINE INPUT ENTER COMMAND or EXIT CMDS Get command from keyboard CNDS UCASES CMD Change input to upper case IF CMDS EXIT THEN CLOSE 1 END Get out on Exit CMD CMDS TERMS PRINT 1 CMDS Send co
154. ot rely on visual inspection of the fuse Use the procedure below to clean the Model 330 periodically to remove dust grease and other contaminants 1 Clean front and back panels and case with soft cloth dampened with mild detergent and water solution NOTE Do not use aromatic hydrocarbons or chlorinated solvents to clean the Model 330 They may react with the plastic materials in the controller or the silk screen printing on the back panel 2 Clean surface of printed circuit boards PCBs using clean dry air at low pressure 5 2 CHANGING POWER SETTING AND FUSE RATING There are two power configurations domestic and foreign Domestic has a single fuse on the hot Foreign has a double fuse for the hot and neutral Units with power requirements specified at purchased are factory pre configured If power settings are incorrect for your application change them with the procedure below 1 Turn off unit Unplug line cord from rear of unit Use small screwdriver to open fuse drawer Pull out fuse holder rotate until proper voltage setting displays through fuse drawer window Place fuse holder back in fuse drawer 5 Remove existing fuse s Replace with proper fuse ratings as follows 2 A for 100 120 VAC or 1 A for 220 240 VAC 6 Slide fuse drawer back into unit Plug line cord into rear of unit Figure 5 1 Power Fuse Access Boo Power On Off Screwdriver Fuse Switch Sbt Drawer m 8 Perform initial setup and
155. ovide 25 W or 50 W maximum and accommodate a variety of cryogenic systems The Model 330 power output is a quiet variable DC current for as little noise coupling as possible between the heater and experiment If lower power is required two lower ranges are available with either of the settings Both IEEE 488 and Serial Interfaces provide remote access to data from the Model 330 and allows setting of most front panel functions 330 Autotuning Temperature Controller Baud 4 Address Escape Heater M M E Input A 80 Type Curve 4 60 Control 40 C 330 1 1 Figure 1 1 Model 330 Temperature Controller Front Panel 1 2 Introduction Lake Shore Model 330 Autotuning Temperature Controller User s Manual Table 1 1 Electronic Information for Various Sensors and Temperature Ranges Suffix Sensor Type Sensor Temperature Coefficient Sensor Units Input Range Sensor Excitation 1 Silicon Diode Negative Volts V 0 2 5 V 10 pA 0 1 constant current 2 100Q Platinum RTD Positive Ohms Q 0 300 Q 1 mA 0 01 constant current 3 GaAlAs Diode Negative Volts V 0 6V 10 pA 0 1 constant current 4 Thermocouple Positive Millivolts mV 15 mV N A The following specifications reflect operational characteristics with the specified Lake Shore Sensor Example Lake Shore Sensor Sensor Temp Range Standard Sensor Curve Typical Sensor Sensitivity DT 470 CO PT 103 with 1
156. pt of the instrument sensor accessories and manual Inspect for damage Inventory all components supplied before discarding any shipping materials If there is freight damage to the instrument file proper claims promptly with the carrier and insurance company and notify Lake Shore Notify Lake Shore immediately of any missing parts Lake Shore cannot be responsible for any missing parts unless notified within 60 days of shipment See the standard Lake Shore Warranty on the A Page immediately behind the title page 2 2 REPACKAGING FOR SHIPMENT To return the Model 330 sensor or accessories for repair or replacement obtain a Return Goods Authorization RGA number from Technical Service in the United States or from the authorized sales service representative from which the product was purchased Instruments may not be accepted without a RGA number When returning an instrument for service Lake Shore must have the following information before attempting any repair 1 Instrument model and serial number 2 Username company address and phone number 3 Malfunction symptoms 4 Description of system 5 Returned Goods Authorization RGA number Wrap instrument in a protective bag and use original spacers to protect controls Repack the system in the LSCI shipping carton if available and seal it with strong paper or nylon tape Affix shipping labels and FRAGILE warnings Write the RGA number on the outside of the shipping container or o
157. r there are probably ac noise currents present The second method simply involves measuring the ac voltage signal across the diode Although an oscilloscope is often the logical choice for looking at ac signals many do not have the sensitivity required and they often introduce unwanted grounds into the system and compound the problem Most testing can be performed with the same digital voltmeter used to measure the dc voltage by simply selecting the ac voltage function There should be no ac voltage across the diode If there is the data presented in the following sections can be used to estimate the potential error in the temperature measurement Il EXPERIMENTAL In order to quantify the effects of induced currents on silicon diode temperature sensors the circuit of Fig 3 was used to superimpose an ac current on the dc operating current The dc current source was 10k battery powered with currents selectable from 1 pA to gt 1 mA The signal generator could be varied in both amplitude and frequency All i voltage measurements were made with a Hewlett Packard 3456A voltmeter in either the dc voltage mode or the ac rms voltage mode The dc measurements were taken with an integration time of 10 V power line cycles without using the filtering options available on the voltmeter The average of several readings was taken to reduce the 3 measurement uncertainty An oscilloscope was also used to double check and monitor signal frequency s
158. r QBasic for use on an IBM PC or compatible with serial interface The user should create an ASCII file with the curve data in the same format as used in the CURV command Immediately following the program are two sample user curve files Then launch the Curve Loading Program where you will be prompted for a file name The program will then open the ASCII file and download the data The line of code in bold is the only difference between the first part of this program and the example shown below 1 SERCURV BAS EXAMPLE PROGRAM FOR SERIAL INTERFACE This program works with QuickBasic 4 0 4 5 or QBasic on an IBM PC or compatible with a serial interface It uses the COM1 communication port and 300 BAUD I To use enter an instrument command or query at the prompt The command goes to 2 the instrument and any query response displays EXIT exits the program NOTE The INPUT instruction in this example accepts no commas as part of an input string If a comma appears in an instrument command replace it with a space when entering data from the keyboard CLS Clear screen PRINT SERIAL COMMUNICATION PROGRAM PRINT TIMEOUT 2000 Read timeout may need more BAUDS 300 BAUD rate 300 or 1200 TERMS CHR 13 CHR 10 Terminators are lt CR gt lt LF gt OPEN COM1 BAUDS o 7 1 RS FOR RANDOM AS 1 LEN 256 LOOP1 INPUT ENTER COMMAND or EXIT CMDS Get command from keyboard CMD UCASES CMD Change input to upp
159. r must be supplied by the controller We have seen in Figures 2 and 3 that a non zero temperature error signal is Exam UE necessary to produce an output and that the magnitude of the Voltage in Volts P V 50 V 50P error or temperature offset is a function of the power output level and the loop gain Let us demonstrate the nature of the offset SE also called droop with an example i Assume that a system sample block the mass whose temperature is to be controlled has a finite heat capacity but that its thermal 15 8 conductivity is infinite as is the thermal conductance between the block and the sensor and heater The result will be that the temperature within the block will be isothermal no matter at what rate the block is heated or cooled For the following discussion ignore any noise associated with the system and assume that to 5 control at 20 kelvin the heating power required is 0 2 watts Assume also that 50 watts of heater power is available reducible in five steps of one decade each Figure 5 shows the control offset for 1 6 1 6 0 32 0 an amplifier gain of 100 and three output power settings which will 0 1 deliver enough power to the system to balance the cooling power D Temperature Error K FIGURE 5 Effect of output power setting on offset for a The temperature offsets for a power level of 0 2 watts at 20 kelvin proportional controller only are easily calculated from Figures 2 and 4 for the three maxi
160. r re eer ee 3 13 3 4 2 Addr6ss 2 enema etii etn NAE UE TU 3 13 3 4 3 bo6alt iere a im eri et mrulim i ERE i 3 13 3 4 4 Instrument Reset and Factory Default Settings A 3 13 3 4 5 Power Up PUP Configuration nemen 3 14 3 5 Thermocouple Controller Operation Model 330 4X Only sse 3 15 3 5 1 Sensor Attachmeri cubes Semis Re URS ce edd ee Ee 3 15 3 5 2 Thermocouple Curve Selection cccccccccceceeeeeeeceaeeeceteeeeeeeanaeceeeeseseeaeaeeeeeeeeeeenaees 3 15 3 5 3 Thermocouple Compensation From Front Panel 3 15 3 5 4 Thermocouple Compensation From Remote Interface sssssssssssssss 3 15 3 5 5 Internal Offset Adjustment eese ensem ena E 3 15 3 5 6 Curve Forma t 2 d iet e e aeta ir Seene 3 15 4 REMOTE OPERATION iic iini e io irent ect dE SEENEN 4 1 4 0 General ctu 4 1 4 1 i Hie ET m 4 1 4 1 1 IEEE 488 Interface Settings sssssssssseee eene enm nennen nnne 4 1 4 1 2 IEEE 488 Command Structure eene entren nens 4 1 4 1 2 1 Bus Control Commandes sss tenent stent EAE sns 4 2 4 1 2 2 Common Commands sse enne eret en ik nenne mrs n nennen nennen nns 4 2 4 1 2 3 Interface and Device Specific Commande 4 2 4 1 3 Status Reglstets x aene e DOR ED IUE d a UR oe a ned te 4 2 4 1 3 1 Status Byte Register and Service Request Enable Register sssssss 4 2 4 1 3 2 Standard Event Statu
161. re Remove and Replace Procedure ssssssssssesrrnrseesrtnrrtnnserstrnnennsreenn nnn 5 5 5 7 Operating Software EPROM and Precision Option NOVRAM Replacement 05 5 5 5 8 Error Messages diee fei cca editae de e A Le dei aeu as avid ected e de ees 5 6 5 9 Changing Sensor Input Typa erener eeraa a a a e a aera 5 6 5 10 Calibration Diode Platinum Input 5 7 5 11 Model 330 4X Thermocouple Calibration sm m 5 9 5 12 Model 330 4X Thermocouple Internal Offset Adiustment AA 5 9 6 OPTIONS AND ACCESSORIES 5 eruere ne retentu EES cevesesuetenecdensevescuecdees 6 1 6 0 General s d o mi AT c LI tuti LP Ed 6 1 6 1 Mera 6 1 6 2 OPUS nF ee eg E M E eMe OLI IUS rate earns 6 1 6 2 1 Ile EINEN Ree EE 6 2 6 3 ACGeSSOLIBSU n xus en deer exce ert EE Ee 6 3 APPENDIX A CURVE TABLES rere p E Aar araa R a E enero Re bak n ee ara ene ERE EAR RE Aaea akm ii SD RD A 1 APPENDIX B APPLICATION NOTES 0 ictccccsscccececeetcessenidiecceeteenteetidineeceursesantidee ceveeseesuebideneeeversenaetideeestess B 1 B1 0 GONG e rs te cai EE B 1 ALPHABETICAL INDEX 5 5 5 eret rore pereo p Pert EENS ee ee esas has INDEX 1 Table of Contents Lake Shore Model 330 Autotuning Temperature Controller User s Manual LIST OF ILLUSTRATIONS Figure No Title Page 1 1 Model 330 Temperature Controller Front Panel nes 1 2 1 2 Model 330 Block Diagram 4 eeeseeesiiess esee esee tne eene nnn
162. re soldering Standard rosin core electronic solder m p 180 C is suitable for most applications Applications involving the use of the SD package up to 200 C will require a higher melting point solder A 90 Pb 10 Sn solder has been used quite successfully with a rosin flux For all adapters except the CY CU and DI the leads are a gold plated Kovar Prolonged soldering times may cause the solder to creep up the gold plated leads as the solder and gold alloy This is not detrimental to the device performance When installing the sensor make sure there are no shorts or leakage resistance between the leads or between the leads and ground GE 7031 varnish or epoxy may soften varnish type insulations so that high resistance shunts appear between wires if sufficient time for curing is not allowed Teflon spaghetti tubing is useful for sliding over bare leads when the possibility of shorting exists Also avoid putting stress on the device leads and allow for the contractions that occur during cooling which could fracture a solder joint or lead if installed under tension at room temperature The DT 470 sensor is designed for easy removal for recalibration checks or replacement and the following discussions for each of the adapters are geared in this direction If semi permanent mountings are desired the use of Stycast epoxy can replace the use of Apieson N Grease In all cases the mounting of the sensor should be periodically inspected to verify that
163. rent control channel setting A channel A B channel B Control Sensor Data Query CDAT 000 00 Returns control sensor data A free field is active here The value returned is 7 characters a sign 5 digits and a decimal point The last digit may be a null 1 2345 term Typical response for a voltage query 123 40 term Typical response for a degrees Celsius query 234 50 term Typical response for a kelvin or degrees Celsius query Set Units for the Control Channel CUNI K CUNI C OrCUNI S Nothing Set control channel units K kelvin C Celsius S appropriate sensor units volts ohms or millivolts If operating in kelvin with a Model 330 01 CUNI S term makes the units volts the sensor units for a diode sensor The Model 330 02 platinum controller has sensor units of ohms and the Model 330 04 thermocouple controller has sensor units of millivolts Control Units Query CUNI K C V R OI M Current control units setting K kelvin C Celsius V volts R Ohms M millivolts Remote Operation FILT Input Returned Remarks FILT Input Returned Remarks SCHN Input Returned Remarks Example SCHN Input Returned Remarks SDAT Input Returned Remarks Example SUNI Input Returned Remarks Example SUNI Input Returned Remarks Remote Operation Lake Shore Model 330 Autotuning Temperature Controller User s Manual Set Display
164. rently selected press Curve The Sample window displays the curve for Sensor A while the Control window displays the curve for Sensor B This sample display indicates Sensor A is using Curve 02 and Sensor B is also using Curve 02 Curve 02 is the DT 400 Series Curve 10 The default curve is Curve 02 for silicon diodes and Curve 03 for platinum RTDs and thermocouples To change the curve press and hold the Curve key and press the A key to increment the Sensor A curve or the Y key to increment the Sensor B curve number The curve numbers available are 00 through 31 When the proper curve number is reached let go Table 2 3 lists the standard curves with curve number and temperature range If a curve with the wrong temperature coefficient slope is selected the Model 330 selects the default curve for the sensor type Installation 2 7 Lake Shore Model 330 Autotuning Temperature Controller User s Manual Table 2 3 Sensor Curves Sensor curves are defined Curve No No of Lines Range K Description as follows 1 325 DT 500 DRC Curve D Domestic D and E1 Curve Older 1 325 DT 500 DRC Curve E1 Export Lake Shore DT 500 Series 1 325 DT 400 Series Sensors Curve 10 Diode Sensors can still use 14 800 Platinum DIN 43760 the Model 330 when set to 2 475 Curve 10 SoftCal D Curve Domestic or E1 Reserved Curve Export 1 4 325 AuFe 0 07 vs Chromel Curve 10 The Lake Shore 4 325 AuFe 0 03 vs
165. rmal resistance eliminates the thermal lag which is the cause of overshoot The zero thermal time constant also means that any amount of reset will eventually force the system to zero error Before we switch the discussion back to real systems let us deal with the nomenclature and units involved in integral control Automatic reset action can be expressed in terms of a time constant minutes or its inverse reset rate repeats per minute The reset time constant is the time required measured in minutes for the reset circuit to integrate to full output with an input signal which is constant and equal to the proportional band error signal The amount of reset action can also be measured in repeats per minute or the number of times which the integrator can integrate between zero and full output in a time period of one minute for the constant proportional band error signal Thus if the time constant were say two minutes this is the same as saying that the reset circuitry repeats the proportional action in two minutes or repeats per minute The term reset windup refers to a condition occurring in reset controller when an offset persists for a sufficiently long time The integration of the error with time will cause the integrator to saturate or windup at maximum output and remain so until the control point is traversed By the time this has happened a large overshoot may have occurred This problem can be prevented by disabling the reset ac
166. rnal Offset Adjustment Paragraph 5 12 5 1 GENERAL MAINTENANCE PRECAUTIONS These recommended general safety precautions are unrelated to any specific procedure and do not appear elsewhere in this manual Personnel should understand and apply these precautions during installation Installation personnel shall observe all safety regulations at all times Keep away from live circuits Turn off system power before making or breaking electrical connections Regard any exposed connector terminal board or circuit board as a possible shock hazard Discharge charged components only when such grounding cannot damage equipment If a test connection to energized equipment is required make the test equipment ground connection before probing the voltage or signal Do not install or service equipment alone Do not under any circumstances reach into or enter any enclosure to service or adjust equipment without the presence or assistance of another person able to render aid If there is no power ensure you are plugged into a live outlet and that both ends of the power cord are plugged in Next check the fuse Remove line cord then place a small slotted screwdriver in the slot of the small door at the rear of the controller to gain access to the fuse See Figure 5 1 For 100 120 V operation the fuse rating is 2 A and the fuse type is MDL 2 Slow Blow For 220 240 V operation the fuse rating is 1 A and the fuse type is MDL 1 Test the fuse with an ohmmeter Do n
167. s Apiezon N Grease 25 gram Tube General purpose grease well suited for cryogenic use because of its low viscosity Often used to thermally anchor cryogenic sensors as well as lubricate joints and o rings Contains high molecular weight polymeric hydrocarbon additive which gives it a tenacious rubbery consistency that forms a cushion between mating surfaces Indium Foil 5 Pieces 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 May be used as a Sealing gasket for covers flanges and windows in cryogenic applications 25 Q Cartridge Heater Features precision wound nickel chromium resistance wire magnesium oxide insulation two solid pins non magnetic package and has UL and CSA component recognition The heater is HTR 25 25 W 6 35 mm 0 25 inch diameter by 25 4 mm 1 inch long The 25 W rating is in dead air In cryogenic applications the cartridge heater can handle many times this dead air power rating 50 Q Cartridge Heater Features precision wound nickel chromium resistance wire magnesium oxide insulation two solid pins non magnetic package and has UL and CSA component recognition The heater is HTR 50 25 W 6 35 mm 0 25 inch diameter by 25 4 mm 1 inch long The 25 W rating is in dead air In cryogenic applications the cartridge heater can handle many times this dead air power rating 119 009 Model 330 User
168. s B 3 Lake Shore Model 330 Autotuning Temperature Controller User s Manual Since the thermal conductivity of cryogenic materials is finite good practice dictates that the controller power output be the same order of magnitude as the cooling power If for example the cooling power is 0 2 watt and 50 watts is available a change in set point to a higher temperature outside the proportional band of the controller will dump 50 watts into the system block Due to the thermal lag of the block etc a large temperature overshoot may occur with the system stabilizing only after several oscillations This thermal lag can easily be observed since the sensor temperature will continue to rise long after the output from the controller has been reduced to zero The obvious way to reduce this effect is to limit the heater power to the system to for example 0 5 watts This can readily be done with a controller such as the DRC 82C which has multiple maximum output power settings The overshoot will therefore be smaller when the set point is changed and the system will stabilize much faster although the rate of temperature rise will be less Because changing the power output setting affects the loop gain dP dT it may be necessary to readjust the deviation amplifier gain controller gain setting for optimum control It is normally good practice to determine the power requirements for one s system prior to or during the first experimental run Some system manufact
169. s Register and Standard Event Enable Register 4 3 4 1 4 Example IEEE Setup and Program sse eene nnn 4 4 4 1 4 1 GPIB Board Installation z zieda aa a aae dae eea et aaraa eaat 4 4 4 1 4 2 Run the Example QuickBasic Program 4 4 4 1 5 Notes On Using the IEEE Interface AA 4 4 4 2 Serial O Interface iei e iced an date cete eb qe d aerae deb aed dn rede dca adus 4 7 4 2 1 Serial Interface Hardware Confgouraton een 4 8 4 2 2 Sample BASIC Serial Interface Program 4 8 4 2 3 Notes On Using The Serial Interface 4 8 ii Table of Contents Lake Shore Model 330 Autotuning Temperature Controller User s Manual Chapter Paragraph Title Page 4 3 IEEE 488 Serial Interface Command Gummanm sse 4 10 4 3 1 Command EE ele 4 10 4 3 2 common Ee En EE 4 11 4 3 3 Interface ComM E Te 4 13 4 3 4 Display eu 4 14 4 3 5 GControl Process Commands EE 4 16 4 3 6 Gurve Commiarids 54 teo etc rate eee e DE Ee 4 19 4 4 User Curve Loading Program 4 23 5 SERVICE AND CALIBRATION 5 eren iore oreet el re SEENEN 5 1 5 0 Cac DET 5 1 5 1 General Maintenance Precautions eene nnne nnn 5 1 5 2 Changing Power Setting and Fuse Rating 5 1 5 3 Rear Panel Connector Definitions sss nennen 5 2 5 4 IEEE 488 Interface Connechor enne nennen 5 3 5 5 Optional Serial Interface Cable and Adapters sssessennnensseesr tn neeeeetnnrtnnseeettennnnnsererrnn nenne 5 4 5 6 Top of Enclosu
170. s heater status 0 off 1 low 2 medium 3 high Heater Status Query RANG 0 1 2 0r 3 Returns current heater status 0 off 1 low 2 medium 3 high Manual Mode Rate Setting RATE XXX Nothing Enter an integer from 0 through 200 Rate corresponds to the Differential D portion of the PID Autotuning control algorithm Rate Query RATE XXX Integer from O to 200 Returns current rate setting Rate corresponds to the Differential D portion of the PID Autotuning control algorithm Manual Mode Reset Setting RSET XXX Nothing Enter an integer from 0 to 999 Reset corresponds to the Integral I portion of the PID Autotuning control algorithm Reset Query RSET XXX Integer from 000 to 999 Returns current reset setting Reset corresponds to the Integral I portion of the PID Autotuning control algorithm 4 17 SETP Input Returned Remarks Example SETP Input Returned Remarks Example TUNE Input Returned Remarks TUNE Input Returned Remarks ZONE Input Returned Remarks Example ZONE Input Returned Remarks 4 18 Lake Shore Model 330 Autotuning Temperature Controller User s Manual Sets the Setpoint In Units Chosen For Control Channel SETP XXX XX for temperature or SETP X XXXX for voltage Nothing For the setpoint parameter enter a value from 0 to 999 9 for temperature or 0 to 2 4990 for voltage Utilizes the free field
171. s is active Note that Autotuning is for PID settings only Autotuning does not set or change the heater range the user must select the proper heater range for their system NOTE The Model 330 only controls when set to temperature units Operation 3 9 Lake Shore Model 330 Autotuning Temperature Controller User s Manual 3 3 4 1 Initial Values of PID Parameters In Autotune Mode Initial values of PID parameters in Autotune mode are set when the controller is changed from Manual to either P PI or PID control Initial factory settings are Autotuning PI where P 50 and 20 which corresponds to 20 repeats per 1000 seconds or an equivalent time constant of 1000 20 or 50 seconds 3 3 4 Minimum Overshoot The full three function PID control algorithm minimizes overshoot It uses Gain P Reset I and Rate D to bring the system to the control temperature as smoothly as possible Rate is limited to the reset setting in seconds e g if the reset rate is 20 then rate is limited to 12 seconds or less To select the PID tuning algorithm hold the Autotune key and press the v key to cycle the Control window display to PID 3 3 4 3 Minimum Time To Setpoint The two function PI control algorithm minimizes the time it takes for the system to first reach the setpoint Some of the damping used in PID control is not present so expect more overshoot To select the PI tuning algorithm hold the Autotune key and press the v key to cycle the Control win
172. ssssssssseerenen enne tenent nennen enn nnns 6 4 6 4 Model RM 3H1 H Rack Mount Kn 6 5 6 5 Model RM 3H2 H Dual Rack Mount Kit 6 6 LIST OF TABLES Table No Title Page 1 1 Electronic Information for Various Sensors and Temperature Hanges 1 3 1 2 Model 330 Gpechficetons enne entere tenen nnne nenr nns n enn n nene 1 4 2 1 Sensor Input Setup idee a oce Lee edades Lee eee upon Pug te ede edad vun de dnd ada dud 2 3 2 2 Diode or Platinum Input Connections enne nnns 2 4 2 3 Sensor Curves Abbreviated 220 cccccccceddeccceedecceeeedenecceedecceeensanceeeessaaceeessecceeeessaceeeedeaeeeeedineeeedanes 2 8 3 1 Sensor Curves Complete list with write in area sss 3 4 4 1 Sample BASIC IEEE 488 Interface Program ssssssesse eene nennen 4 5 4 2 Serial Interface Parametere 4 8 4 3 Sample BASIC Serial Interface Program ssssssssssesseeeeneeeene nennen 4 9 5 1 Sensor N t Set p eene ert ae ed dae duae eee dati ANEN 5 6 A 1 Standard Diode and Platinum Curves eene nennen enne A 1 A 2 Thermocouple Curves Chromel Versus Gold lron ssssssssssssseseee A 2 A 3 Thermocouple Curves Chromel Versus Copper nnn A 2 iv Table of Contents Lake Shore Model 330 Autotuning Temperature Controller User s Manual CHAPTER 1 INTRODUCTION 1 0 GENERAL Lake Shore Cryotronics Inc designed and manufactures the Model 330 Autotuning Temperature Controller in the United
173. t 1 2 Follow the REMOVE TOP procedure in Paragraph 5 6 Place the thermocouple in a reference bath of known temperature liquid nitrogen ice etc Allow the system to stabilize to the reference temperature On the Model 330 front panel select the thermocouple input and the desired temperature units Turn on thermocouple compensation Adjust the offset adjustment trimpot R6 for Channel A and R8 for Channel B so the displays read the reference temperature Follow the REPLACE TOP procedure in Paragraph 5 6 Service amp Calibration 5 9 5 10 Lake Shore Model 330 Autotuning Temperature Controller User s Manual This Page Intentionally Left Blank Service amp Calibration Lake Shore Model 330 Autotuning Temperature Controller User s Manual CHAPTER 6 OPTIONS AND ACCESSORIES 6 0 GENERAL This chapter covers Model 330 Temperature Controller model numbers Paragraph 6 1 Options Paragraph 6 2 and Accessories Paragraph 6 3 6 1 MODELS Two Model 330 independent sensor inputs can be variously configured with certain combinations of the following input types Users can reconfigure any of the input types except for the optional thermocouple input Model Channel A Sensor Channel B Sensor 330 11 Silicon Diode Silicon Diode 330 12 Silicon Diode Platinum Resistor 330 13 Silicon Diode GaAlAs Diode 330 22 Platinum Resistor Platinum Resistor 330 23 Platinum Resistor GaAlAs Diode 330 33 GaAlAs Diode GaAlAs Diode 330 4
174. t to ground potential by providing a conductive surface and discharge paths As a minimum observe these precautions 1 Deenergize 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 4 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 5 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 6 Do not handle ESDS devices unnecessarily or remove from the packages until actually used or tested 1 6 Introduction Lake Shore Model 330 Autotuning Temperature Controller User s Manual 1 5 HANDLING LIQUID HELIUM AND LIQUID NITROGEN Liquid Helium LHe and liquid nitrogen LN2 may be used in conjunction with the Model 330 Although LHe and LN are not explosive there are certain safety considerations when handling them 1 5 1 Handling Cryogenic Storage Dewars Operate all cryogenic containers dewars in accordance with manufacturer instructions Safety instructions are norm
175. te that this voltage offset is due to induced currents in the total measuring system and is not simply a voltage pickup by the diode itself An ac voltage superimposed symmetrically about the dc operating voltage of the diode would not cause a dc voltage offset VOLTAGE V N o 5 o m o a 0 0 0 0 100 200 TEMPERATURE K 300 FIGURE 1 Voltage temperature curve for a typical silicon diode temperature sensor at a constant current of 10 uA IV CURVE lccoswt l DC OPERATING ac POINT V FIGURE 2 IV curve for a silicon diode sensor showing effect of an induced ac current superimposed on the dc operating current lac The expected dc operating voltage is Vac which is shifted from the average voltage Vave indicated by the voltmeter in a dc measurement mode Application Notes Lake Shore Model 330 Autotuning Temperature Controller User s Manual There are two simple techniques which can be used to test whether these errors might be present in a measuring system The first is to connect a capacitor about 10 pF in parallel with the diode to act as a shunt for any ac noise currents The capacitor must have low leakage current so as not to alter the dc current through the diode The capacitor may also alter the time response of the measurement system so allow sufficient time for the capacitor to charge and for the system to equilibrate If the dc voltage reading across the diode increases with the addition of the capacito
176. ted sensor data into breakpoint pairs readable by the controller program The Precision Calibration Option is available in three forms the Model 8000 loads the breakpoint pairs on a floppy disk in ASCII format for Customer downloading the Model 8001 is a factory installed NOVRAM the Model 8002 05 is a field installed NOVRAM Precision Calibration improves specified accuracy to 0 1K or better over a given calibration range for DT 400 Series Silicon Diode Sensors Accuracy for other sensors depends on the type and calibration range Lake Shore supplies a copy of break point information containing sensor type sensor serial number maximum allowable error break point number voltage or resistance temperature and temperature error along with a second sheet containing only the break point temperatures and voltages The Precision Calibration Option Table is a piecewise linear interpolation based on the sensor calibration Optimum break points are determined by an iterative procedure using weighted linear least squares defined by either a maximum number of break points allowed or a maximum allowable error Break point voltages are derived from the least squares linear equations and differ from the calibration data Differences between input table voltages and break point voltage are converted to a corresponding error in temperature by dividing the voltage difference by the sensitivity Temperature errors by this method will be considerably less than by li
177. teger from 1 to 30 Address 0 and 31 are reserved Nothing Sets the IEEE address The Model 330 is factory preset to 12 IEEE Address Query ADDR 1 to 30 Returns the current IEEE address setting The Model 330 is factory preset to 12 Set End Or Identify EOI Status END 0 or END 1 Nothing Sets the EOI status 0 enabled 1 disabled When enabled the hardware EOI line becomes active with the last byte of a transfer The EOI identifies the last byte allowing for variable length data transmissions End Or Identify EOI Status Query END Current EOI status 0 EOI enabled 1 EOI disabled Set Local Remote or Remote With Local Lockout Mode MODE 0 MODE 1 or MODE 2 Nothing Sets the Model 330 mode 0 Local Mode 1 Remote Mode 2 Remote Mode with Local Lockout Press the front panel Local key to set the Model 330 to local provided the key has not been disabled by local lockout The Model 330 powers up in local mode At the end of a command string MODE 0 maintains constant local operation Mode Query MODE Current mode setting 0 local mode 1 remote mode 2 remote mode with local lockout Set Terminating Character Type TERM 0 TERM 1 TERM 2 or TERM 3 Nothing Sets the terminating character type from 0 to 3 defined as follows 0 Carriage return and line feed CR LFEO 1 Line feed and carriage return LF CREO 2 Line feed LFE9 3 No terminating characters EOI line set w
178. th in this warranty and incidental or consequential damages are expressly excluded 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 330 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 time 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
179. the generic requirements of the European EMC directive 89 336 EEC 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 Pay special attention to instrument cabling Improperly installed cabling may defeat even the best EMC protection For the best performance from any precision instrument follow the grounding and shielding instructions in the User s Manual In addition the installer of the Model 330 should consider the following Leave no unused or unterminated cables attached to the instrument Make cable runs as short and direct as possible Do not tightly bundle cables that carry different types of signals Add the clamp on ferrite filter part number 109 053 included with the connector kit to the serial interface cable near the instrument rear panel when that interface is used Lake Shore Model 330 Autotuning Temperature Controller User s Manual TABLE OF CONTENTS Chapter Paragraph Title Page 1 INTRODUCTION mm 1 1 1 0 EE e EEE E A Mu A ae E E E E 1 1 1 1 Model 330 Temperature Controller Description sssssssseeeene 1 2 1 2 Control Fundamentals and Autotune nennen 1 5 1 3 Pr cision Calibration Options 2 2 52 toe eec ate ine at EES op beats de seet 1 6 1 4 Electrostatic Ree TEE 1 6 1 4 1 Identification of Electrostatic Dis
180. though the ac component can be due to a poorly designed current supply a more common source of the ac is noise induced in the measurement circuit This noise can be introduced through improper shielding improper electrical grounds or ground loops Currently available voltmeters have sufficient normal mode rejection capabilities in their dc measurement modes that these noise effects can go completely unnoticed if they are not explicitly checked The equivalent temperature error which may be caused by this problem is typically a few tenths of a kelvin although an extreme case with a 4 K error has been observed The effect of the ac noise appears as a shift in the dc voltage measurement due to the nonlinear current voltage characteristics of the diode An illustration of this effect is shown in Fig 2 where an exaggerated IV curve is given An induced ac noise current superimposed on the dc operating current lac is shown along the current axis The resulting voltage seen by the voltmeter is shown along the voltage axis The nonlinear IV characteristics of the diode have caused a distortion in the ac voltage signal making it asymmetrical with respect to the voltage reading corresponding to lac When a voltmeter operating in a dc voltage mode reads this signal the signal is processed by integrating filtering etc to give an average dc voltage reading which will be lower than expected The apparent temperature measurement will then be too high No
181. ting in manual or AutoTune mode Gain corresponds to the Proportional P portion of the PID Autotuning control algorithm Heater Power Status Query HEAT XXX Returns the percent of full scale heater current The returned number represents five percent increments up to 100 Enable Disable Ramp Function RAMP 0 Or RAMP 1 Nothing RAMP 0 disables the ramping function while RAMP 1 enables ramping Ramping Enable Disable Status Query RAMP Dor l Returns Ramp status 0 ramping function disabled 1 ramping function enabled Remote Operation RAMPR Input Returned Remarks Example RAMPR Input Returned Remarks RAMPS Input Returned Remarks RANG Input Returned Remarks RANG Input Returned Remarks RATE Input Returned Remarks RATE Input Returned Remarks RSET Input Returned Remarks RSET Input Returned Remarks Remote Operation Lake Shore Model 330 Autotuning Temperature Controller User s Manual Set Ramp Rate in Kelvin per Minute RAMPR XX X Nothing XX X is the ramp rate in Kelvin per minute between 0 and 99 9 RAMP 10 term instructs the Model 330 to make the ramp rate equal to 10 K Min Ramp Rate Query RAMPR XX X Returns the current value of the ramp rate Ramping Status Query RAMPS oor1 Returns 1 if controller is ramping or 0 if not ramping Set Heater Status RANG 0 RANG 1 RANG 20r RANG 3 Nothing Set
182. ting the accuracy and performance of a temperature measurement system Several of the more common problems which introduce noise into diode circuitry are described INTRODUCTION Current technological uses of temperature sensors require better calibration accuracies and better device performance than ever before However the assurance of an accurate temperature measurement does not stop with simply the sensor specifications Just as critical is the instrumentation used with the sensor and the manner in which the instrumentation is used This paper concentrates on identifying verifying and eliminating an often overlooked instrumentation or system induced error in the use of diode temperature sensors L PROBLEM DEFINITION Semiconductor diode temperature sensors have been in use for over 20 years and with the advantages they offer over resistance sensors or thermocouples for many applications their popularity continues to increase Diodes are operated at a constant current typically 1 10 or 100 pA while the voltage variation with temperature V T is monitored The diode sensor has a useful temperature range from above room temperature to as low as 1 K with reproducibilities to better than 50 mK Figure 1 shows the voltage variation with temperature for a typical silicon diode temperature sensor An error arises in diode thermometry if the excitation current is not a true dc current but has an ac component superimposed on the dc Al
183. tion The thermocouple input has a thermal block for connecting thermocouple wires and for temperature compensation Thermocouple response curve tables within the instrument are normalized to the ice point of water Obtain accurate readings by one of two methods use an ice bath with a reference junction with the internal room temperature compensation turned OFF or more conveniently eliminate the reference junction and ice bath and use the internal electronic room temperature compensation by turning internal compensation ON When a new or different thermocouple is attached to the controller adjust the offset to compensate for discrepancies in thermocouple material leads and connections Offset adjustment trimpots are provided inside the Model 330 to allow offset calibration of the thermocouple See Paragraph 5 12 2 6 2 2 Thermocouple Wire Types at Cryogenic Temperatures Below are recommended thermocouple wire types for cryogenic temperatures The ANSI color code for thermocouples is red for the negative lead while the type of thermocouple determines the positive lead color purple Type E black Type J yellow Type K and blue Type T For details on thermocouples or other sensors see the Lake Shore Temperature Sensor Guide Chromel vs Gold with 0 03 or 0 07 Atomic Iron 0 03 not currently sold by Lake Shore Consists of Gold Au doped with 0 03 or 0 07 atomic percent Iron Fe as the negative thermoelement and a Ni Cr alloy C
184. tion when controller response goes outside the proportional band A controller such as the DRC 82C accomplishes this with an anti reset windup or reset inhibit circuit B 4 Application Notes Lake Shore Model 330 Autotuning Temperature Controller User s Manual The Real World Revisited Since a real cryogenic system has non zero thermal resistance the value of the reset is important in setup of the controller The amount of reset desired is dependent on 1 the time required for the control sensor to reach equilibrium once it enters the proportional band and 2 the amount of output signal required from the reset action to overcome the cooling power of the cryogenic system For example assume that 50 output is required and the time to reach equilibrium is 3 seconds 05 minutes Therefore the repeats per minute is 10 and the time constant is 0 1 minutes In actuality this is not easy to determine without a few tries Almost always however the time constant increases with increasing temperature so that if one is operating over a broad temperature range finding the appropriate time constants for the two extremes will bracket the appropriate time constants within that temperature range Once the correct time constant has been selected the system should settle to its control set point within two or three time constants If significant overshoot is still occurring the system design should be carefully reviewed V ADDING DERIVATIVE RATE TO T
185. tput current always displays on a separate bar graph The full function keypad makes the Model 330 easy to operate Precision thermometry is necessary for stable accurate control and the Model 330 analog design provides stable and repeatable measurements Current source isolation allows for a true four lead measurement of the sensor signal A high resolution A D converter digitizes the signal for use in thermometry control and Autotuning Enhance Model 330 thermometry accuracy with a Lake Shore calibrated sensor and 8000 Series Precision Calibration Option or with SoftCal Model 330 control software compares the measured control sensor value to the desired control setpoint and minimizes the difference with a three term PID function Enter control parameters in any one of five tuning modes Autotuning P Autotuning PI Autotuning PID Zone and Manual Autotuning utilizes information gathered during setpoint changes to automatically optimize control parameters Program up to 10 custom temperature zones so the controller automatically uses pre programmed PID settings and heater ranges computer interface required Set the rate at which the ramp setpoint increases or decreases when it is changed Combine this setting with the zone feature to ramp through all 10 zones from 2 K to room temperature with only a setpoint change The controller changes PID and heater range settings as the setpoint passes through different zones Two heater settings pr
186. tracted from the proportional output signal This reduces the effective overall amplifier gain driving the output power stage The reduced gain effectively increases the proportional band of the controller This slows down the rate of temperature rise and therefore allows more time for the block to stabilize Consequently the overshoot is substantially reduced or eliminated depending on the magnitude of the thermal problem as is indicated in Figure 6 100 The addition of rate is necessary only because of inherent thermal Erl problems which cannot be substantially eliminated by improvements in thermal design Also note that rate is effective only during the Time SENA e ong s point ee of Se the set E FIGURE 6 The effect of adding Rate to the control as a destapitzing InTuence st SOU ereiore be normal practice lO circuit to dynamically widen the proportional band and turn off the rate control when near the control point reduce the overshoot which would occur in its absence Without Rate j The differentiator circuit should precede the reset integrator in the circuit so that the deviation and derivative signals acting on the integrator input will be just sufficient to create the proper reset value by the time the temperature reaches set point In some cases it is important for the rate circuit to precede the deviation amplifier as well i e immediately following the sensor input This would then prevent the rate circuit fr
187. troller User s Manual A system normally takes several time constants to settle into the set point e g the 50 second time constant if correct for the controlled system results in a stable set point in about 5 to 10 minutes The oscillation period measured in determining the appropriate gain equals the desire reset time Divide this number in seconds into 1000 and set the result into the RESET register This result is the number of repeats per 1000 seconds If the system did not oscillate at the highest gain setting use the following procedure Stabilize the temperature at a high gain setting Change the set point downward by one or two degrees and observe the time that it takes for the temperature to change 60 of this excursion Use this number as the reset time divide it into 1000 and set in the result as the RESET value 3 3 5 3 Setting Rate Derivative Adjusts rate time constant of derivative D in the control function Enter a value between 0 and 200 of 1 4 the reset time In manual mode rate is normally set at 1 4 the reset time in seconds 10096 because larger values may cause system instability To enter a rate value press the D key The lower Control window display shows the current D setting the default setting is 100 with the units place blinking Use the numeric keypad to enter a new setting Press Enter to accept the new setting or Escape to return the normal display and retain the old setting The rate time constant is nor
188. unit MODEL NUMBER DESCRIPTION OF MODEL 330 ACCESSORY 106 009 Heater Output Connector Dual Banana Jack Sensor Mating Connector Quantity 2 Detachable 120 VAC Line Cord RJ 11 Cable Assembly Four Wire Cable Assembly with RJ 11 plugs on each end Used with RS 232C Interface Cable is 14 feet 4 6 meters long See Figure 6 1 RJ 11 to DB 25 Adapter Adapts RJ 11 receptacle to female DB 25 connector Connects Model 622 647 to RS 232C Serial Port on rear of Customer s computer See Figure 6 2 RJ 11 to DE 9 Adapter Adapts RJ 11 receptacle to female DE 9 connector Connects Model 622 647 to RS 232C Serial Port on rear of Customer s computer See Figure 6 3 Heater Output Conditioner A passive filter which further reduces already low Model 330 heater output noise Typical insertion loss for the Model 3003 is 20 dB at 10 uV at line frequency and gt 40 dB from double the line frequency up The Model 3003 is housed in a 144 mm x 72 mm x 165 mm 5 67 x 2 84 x 6 5 inch panel mount enclosure and weighs 1 6 kg 3 5 Ibs The Model 3003 requires no external power Take care not to reverse the polarity of the incoming heater signal An input protection diode acts as a short in case of reversed polarity It is not necessary to use ground terminals provided but sometimes it helps reduce noise Shorting out the filter input or output while the controller driving it is turned on is not recommended the Model 3003 may have a large stored charge
189. upply the Model 330 serial number at the time of order 2 8 Installation Lake Shore Model 330 Autotuning Temperature Controller User s Manual 2 9 HEATER SETUP Model 330 heater output is on the rear panel as a Dual Banana Jack A mating connector is HEATER supplied Current is driven from the Heater Output HI connection to the LO connection 25 o 50 Connect a resistive load of 50 Q for the 50 Watt heater setting or 25 Q for the 25 Watt heater setting between these two points JMP9 The factory sets the Model 330 jumper per Customer request at the time of order and Figure 2 2 indicates the setting on the B Page inside the front cover The jumper is set to 25 for 25 W Heater Jumper output or 50 for a 50 W output To check the heater setting before first operation see JMP9 Paragraph 5 7 for instructions on properly opening and closing the instrument then look for JMP9 Figure 2 2 on the Model 330 Printed Circuit Board Figure 5 9 CAUTION Do not change the Heater Jumper JMP9 with the instrument power on The heater output is 1 A on High range 0 3 A P Heater Heater 25W with 25 O 50 W with 50 O needs no fuse The Model 330 powers either a Range Cue TE iL eater Power Heater Power 25 W or 50 W resistive heater for maximum 0t01A 25 Watts 50 Watts heater output Larger resistance may be used MEDIUM 0 to 0 3A 2 5 Watts 5 Watts but results in lower maximum power output For example the output compliance voltage 0 to0 1A 0 25 Watts
190. ur first SoftCal measurement around 4 2 K 1 Select the input channel that needs calibration as the Sample sensor 2 Immerse the temperature sensor in Liquid Helium and allow the controller temperature reading to stabilize The temperature controller knows which point is being entered by the temperature range 3 Select K units for low temperatures and C units for higher temperatures This takes advantage of display resolution 4 Press the SoftCal key to display the CUR indicator Enter a curve number from 11 to 31 Be sure to select a number not currently holding another curve this procedure overwrites any data in that location Push the Enter key The Sample window shows the current sensor reading In the Control window enter the exact temperature of the sensor versus the displayed value Push the Enter key The CAL indicator turns off and normal operation resumes When the CAL indicator turns off the instrument accepts the new point and generates a new curve from it To verify the new point push the Curve key and use the A or W key to increment the display to the Curve number of the SoftCal curve Verify the Sample display reads the same as the value just entered If the curve number changes back to the default value for that type sensor then no calibration occurred and no new curve was generated SoftCal automatically logs points based on the temperature range of the sensor The low temperature point is taken in th
191. urers may have that information available and may possibly supply a power load curve with the system Two other aspects of temperature control should be mentioned First ON Off controllers are frequently encountered at room temperature and above As the name implies such systems have only two states power on when the temperature is below the set point and off when it is above The proportional controller with excessive loop gain approximates this mode Although ON OFF controllers perform adequately with large furnaces for example they are generally unsatisfactory for cryogenic applications because of the relatively short thermal time constants encountered at low temperatures Secondly some controllers such as the DRC 82C have a manually adjustable power output control This control can be used in either of two modes 1 open loop with a manual adjust of heater power in place of the signal from the deviation amplifier and 2 automatic where the adjustment is in addition to the controller s closed loop signal Mode 1 is extremely helpful in set up procedures and in subsequently determining the power levels associated with the desired temperatures In Mode 2 one can reduce and sometimes eliminate temperature offset by providing the required power without the need for a large error signal to drive the output stage This latter method has a name manual reset and serves as an introduction to the next section on reset control IV PROPORTIONAL
192. vice Specific commands Device Specific Commands consist of Interface Display Channel Control Process and Curve commands See Paragraph 4 3 for a list of all Model 330 interface and device specific commands 4 1 3 Status Registers There are two status registers the Status Byte Register Paragraph 4 1 3 1 and the Standard Event Status Register Paragraph 4 1 3 2 4 1 3 1 Status Byte Register and Service Request Enable Register The Status Byte Register consists of one data byte containing six bits of information about Model 330 status STATUS BYTE REGISTER FORMAT Bit ce E E PN PS ES ER Ce Waighing 198 564 92 16 8 4 2 4 E Bit Name 4 2 Remote Operation Lake Shore Model 330 Autotuning Temperature Controller User s Manual If the Service Request is enabled setting any of these bits causes the Model 330 to pull the SRQ management low to signal the BUS CONTROLLER These bits reset to zero upon a serial poll of the Status Byte Register Inhibit or enable these reports by turning their corresponding bits off or on in the Service Request Enable Register The SRE command sets the bits Setting a bit in the Service Request Enable Register enables that function See the SRE command Service Request SRQ Bit 6 Determines whether the Model 330 reports via the SRQ line Four bits determine which status reports to make If bits 0 1 2 4 or 5 are set then the corresponding bit in the Status Byte Register is s
193. voltmeter A current source operating at the level of 10 01 microamperes 40 1 gives a nominal temperature uncertainty of 10 millikelvin 0 01 K which is probably suitable for most applications The voltmeter resolution required can be estimated from the sensitivity dV Dt of the DT 470 Temperature K Sensitivity mV K 305 2 4 77 1 9 4 2 33 Multiplying the above sensitivity by the desired temperature resolution in kelvin will give the required voltage resolution in millivolts The static impedance of the DT 470 sensor operating at a 10 microampere current is on the order of 100 000ohms Therefore the input impedance of the voltmeter must be significantly larger than this to avoid measurement errors Voltmeters with input impedances of greater than 109 or 1010 ohms should be used Good quality instrumentation must be used and all instrumentation and wiring should be properly grounded and shielded Temperature measurement errors will result if there is excessive AC noise or ripple in the circuitry Further details can be found in the article by Krause and Dodrill given in the references NOTE All materials mentioned which are used in sensor installation are available from Lake Shore Cryotronics Inc References Krause J K and Swinehart P R 1985 Demystifying Cryogenic Temperature Sensors Photonics Spectra August 61 68 Available on request from Lake Shore Cryotronics Inc Krause J K and Dodrill B C 1986 Measure
194. wing procedure Set Autotune to Manual then turn off both Reset I and Rate D Enter a nominal gain of 50 Verify that the heater turns on if not increase the gain setting until the heater turns on then let the system stabilize It stabilizes at some point below the setpoint typically 2 to 3 K below Increase the gain by factors of two until the system temperature begins to oscillate Adjust the gain for small sustained oscillations Measure the period of these oscillations to determine the correct setting for reset Reduce the gain by a factor of two to three until the temperature again stabilizes Be sure to allow time at each setting for the system to stabilize if it will Some systems and cryogenic sensors with low sensitivity require the maximum gain 3 3 5 2 Setting Reset Integral Adjusts the reset time constant of reset Integral in the control function Reset time in seconds 999 Value Entered For example if the Reset setting is 20 the reset time in seconds is about 50 999 20 50 Enter a value from 1 to 999 A reset of zero makes the controller proportional only To enter a reset value press the I key The lower Control window display shows the current setting the default is 20 with the units place blinking Use the numeric keypad to enter a new setting Press Enter to accept the new setting or Escape to return the normal display and retain the old setting 3 10 Operation Lake Shore Model 330 Autotuning Temperature Con
195. y error as small as the useful resolution of the controller system Thus in the 14 bit system referred to earlier in this section its 4 mK resolution would be swamped by e g a conformity limited 100 mK Fortunately in a controller such as the DRC 82C the user can select either a temperature or voltage resistance set point and readout The choice between analog and digital controllers turns out to be not a choice at all but an optimum combination of the best features of each True analog control provides a heater output that is a continuous function of the sensor signal and so eliminates the sampled data problem This analog control may be combined with digital circuitry for readout of sensors and power output for setting the PID control parameters and for deriving the set point signal This approach is used in most of the Lake Shore Cryotronics Inc controllers B 6 Application Notes Lake Shore Model 330 Autotuning Temperature Controller User s Manual For Further Reading 1 E M Forgan On the Use of Temperature Controllers in Cryogenics Cryogenics 14 1974 pp 207 214 This is a cogent discussion of the interaction between the electrical and thermal response times in a typical cryogenic control system The mathematical analyses are straightforward and relatively easy to follow A series on process Control published in the journal Measurement amp Control Part 3 On Off and Proportional Control September 1984 pp 1
196. ynomials represent Curve 10 on the preceding page with RMS deviations of 10 mK The Chebychev equation is T x 3 ad 1 i 0 where T x temperature in kelvin ti x a Chebychev polynomial and a the Chebychev coefficient The parameter x is a normalized variable given by ve V VL VU V VU VL where V voltage and VL and VU lower and upper limit of the voltage over the fit range The Chebychev polynomials can be generated from the recursion relation Lais 2xti x ti 1 x H to x 1 669 x 2 Alternately these polynomials are given by ti x cos i x arccos x 4 The use of Chebychev polynomials is no more complicated than the use of the regular power series and they offer significant advantages in the actual fitting process The first step is to transform the measured voltage into the normalized variable using Equation 2 Equation 1 is then used in combination with equations 3 and 4 to calculate the temperature Programs 1 and 2 provide sample BASIC subroutines which will take the voltage and return the temperature T calculated from Chebychev fits The subroutines assume the values VL and V U have been input along with the degree of the fit The Chebychev coefficients are also assumed to be in any array A 0 A 1 A iaegree An interesting property of the Chebychev fits is evident in the form of the Chebychev polynomial given in Equation 4 No term in Equation 1 will be greater than the absolute va

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