Model DTC-500A - Lake Shore Cryotronics, Inc.
Contents
1. To increase system response if needed take the RATE control Key No 7 out of the detent off position in the clockwise direction For various settings of the control observe the transient response to a change in set point Too short a time constant may result in oscillation and an unstable system A change in gain may be necessary to eliminate oscillation or overshoot __ 0482 f 15 PROGRAMMED SET POINT TEMP SAMPLE HOLDER TEMP NEW SET PT TEMP INITIAL INSTANTANEOUS TEMP ERROR TEMP TIME TIME OF ABRUPT CHANGE IN SET PT TEMP INITIAL PROGRAMMED SET POINT TEMP SET PT SAMPLE HOLDER TEMP TEMP INSTANTANEOUS TEMP ERROR NEW SET PT TEMP TIME TIME OF ABRUPT REDUCTION IN SET PT TEMP Figure 3 4 Temperature versus Time Characteristics of Controller 16 0482 0482 3 6 Manual Reset Heating Mode By placing the mode selector switch Key No 4 in either MAN or MAN B a manually settable constant current may be supplied to the heater element The magnitude of the current is determined by the setting of the MAN RESET potentiometer Key No 5 and the HTR CURRENT RANGE Key 9 The current supplied to the heater is indicated on the HEATER CURRENT meter The full scale reading of the meter corresponds to the HTR CURRENT RANGE switch setting MAN RESET allows the user to hold temperature for short period of time in an open loop condition while he uses the null meter and the digit2. 9 to 1000 Milliamperes E GAIN Keys No 2 and 3 to minimum settings F RESET Key No 6 to off G RATE Key No 7 to off H INTERNAL SET POINT VOLTS switch Key No 1 to voltage corresponding to desired temperature I POWER switch Key No 8 to on If the block or sample holder whose temperature is to be controlled is colder than the set point temperature the sensor diode voltage will be high and the null meter will deflect to the right Slowly increase the GAIN setting Keys No 2 and 3 The HEATER CURRENT meter should show an immediate up scale deflection proportional to the GAIN setting The NULL meter should start to come off its full right deflection position as the gain is increased As the sample holder temperature approaches the set point temperature the NULL meter will approach center scale and the HEATER CURRENT meter will assume a steady value even with a further increase in the gain setting Continue to increase the gain until an incremental change in gain produces a negligible reduction in the null error but not so high as to produce oscillations To further reduce the null error rotate the AUTO RESET gain control Key No 6 out of the detent off position in the clockwise direction As the control is advanced the null meter should approach the center position with unobservable error Leave the AUTO RESET vernier in the position required to reduce the null error to zero but below any
3. Adjust the trim potentiometer 42750 that the null meter Key No 11 is at zero with the gain Keys No 2 and 3 at its highest value Both amplifiers are now in balance with zero offset 5 9 Adjustment of the Digital Set Point The adjustment of the digital set point requires only a precision resistor in the range from 50 K to 250 K Let us assume that the resistor has the value 100 010 ohms A Complete sections 5 6 5 8 B Place the precision resistor in place of J1 using the connection diagram shown in Figure 2 1 c C Set the digital set point Key No 1 to 1 0001 volts D Adjust trim potentiometer R25 so that the null meter reads zero with the gain Keys No 2 and 3 to its highest value The re calibration of your controller is now complete 0482 _ 0482 5 9 Parts List Component Location Diagram and Schematic REF DESG R1 R2 R3 R5 R6 R7 R9 R10 R12 R13 R14 R15 R16 R17 R19 R20 R21 R22 R23 R24 R25 R26 R27 R28 R29 R30 R31 R32 R34 R35 R36 R37 R38 R39 R40 Table 5 1 PARTS LIST FOR DTC 500A LAKE SHORE DESCRIPTION PART NO 3 92 1 19 1 1 511 ohm 1 8W 1 3 83 1 8W 1 10K Trim Pot constant current adjust 10K XV 0 5 499K XW 1 3 83K 1 Not present 100K Trim Pot Buffer Zero Not present Not present 1 0K 100K 909K 1 10 1 Not present 100K 423K 423K 423K 154K 1 Bo p PP Pr zj xij x
4. which when plugged into an appropriate receptacle grounds the instrument 2 5 Installation The DTC 500A Controller is all solid state and does not generate signifi cant heat except in the 1 amp scale It may therefore be rack mounted in close proximity to other equipment in dead air spaces However the heat from such adjacent equipment should not subject the DTC 500A Controller to an ambient temperature in excess of 50 122 As with any precision instrument it should not be subjected to the shock and vibrations which usually accompany high vacuum pumping systems 5 The recommended cable diagrams for the sensor diode and heater element are given in Figure 2 1 a and b The use of four wire diode connection is highly recommended to avoid introducing lead IR drops in the voltage sensing pair which is translated into temperature measurement error The indicated shielding connections are the recommended standard practice to avoid ground loops The alternate wiring scheme shown in Fig 2 1 c may be used for the diode in less critical applications where control is important but small temperature readout errors can be tolerated The heating element should be floated to preclude the possibility of any of the heater current being conducted into the diode sensor leads Electrical feedback in addition to the desired thermal feedback may cause oscillations and certainly erroneous temperature readings Inspect the
5. 0 to 100 of full output can be set from front panel Heater Output 0 25 watts into 25 ohm load Heater current range can be limited at 10mA 30mA 100mA 300mA and 1A approximate decade power increments Temperature Readout Method Sensor voltage is nulled against set point voltage using front panel thumbwheels in MANUAL mode Temperature is determined from V vs T tables requires sensor calibrated over appropriate temperature range Accuracy 100 microvolts tcalibration error of Sensor General Remote Set point Input 7 pin rear panel connector or optional BCD interface connector Dimensions Weight 432mm wide x 146mm high x 330mm deep 17 in x 5 in x 13 in Style L full rack package Net weight 8 2 kg 18 Ibs Power 105 125 or 210 250 VAC switch selected 50 or 60Hz 65 watts Accessories Supplied Mating connectors for sensor and remote inputs instruction manual Options and Accessories Available Model DTC BCD Interface Allows remote digital control of set point and provides BCD output of Sensor voltage divided by two Model SW 10A 10 Sensor Selector Switch Pushbutton selection of any one of up to 10 sensors Dimensions 216mm wide 102mm high x 330mm deep 8 in x 4 x 13 in Style L half rack package Model RM 3H Rack mount kit to mount either one or two SW 10A in standard 3 rack space 4 RM 5F Rack ears with handles to mount DTC 500A in standard 5 rack space Model DT
6. 28K HEATER CURRENT HTR CURRENT RANGE MILLIAMPERES POWER MANUAL SET Because the set point is in voltage rather than temp erature the controller is easily able to accommodate sensors with various response curves as well as exter nally generated set points without the accuracy con straints imposed by standard curve systems The set point is settable from 0 0000 to 2 9999 volts via either front panel thumbwheels external analog voltage or resistance control or digitally with the optional DTC BCD Interface which also provides a BCD output of the sensor voltage 2 Accurate temperature measurement is also possible with the DTC 500A by operating the unit in the open loop mode The sensor voltage is nulled against the set point using the built in meter thus the set point becomes a read out of the actual sensor voltage Re ferral to a V vs T calibration table for the particular sensor yields the actual temperature reading A dual sensor input is provided on the 500A which enables redundant measurements or optimization of sensor location for best control and most accurate readout Heater output of up to 25 watts is available from the DTC 500A Maximum heater current may be set from 10mA to 1A in 1X and 3X steps This enables output power to be appropriately limited to protect delicate heaters or systems as required Multi sensor inputs for the DTC 500A are possible with the accessory Model SW 10A Sensor Selector Up t
7. 5 den 15V Bo gt gt 2 2 1 3 7 1 15V 9 5VCOMD o pu Jue 1 LI 15 110 100 1000 MA saa LAST REFERENCE USED 4 340 MX CHEATER ELEMENT 1 KZ oT em m mim P1 10 100 V SET POINT THUMBWHEEL om CHASSIS GROUND DIGITAL GROUND gt RATE 55 1 Av Len 32 0 R20 kepz Figure 5 1 Circuit Schematic Diagram Figure 5 2 Parts Layout for Printed Circuit Board 0482 43 0482 9 5V o 5V 9 15V o 5V o 15V 019 7408 ZEN gt ble PMEPT 4104 4019 io h5 rat 4 5 R AHE 2 LEE 8 91 1 5 x maj EZE 5 B 2101 2161 2 8 o N S gt 4 5 5 5 4 9 2 op 2 x LG S V 8 x eJ V 7 27 E LL LI 2 0216 16 1171121 m II 5 51 113 5 8 5 ic 017 7414 12 745175 75 741 51 U11 71 Grounding 1 Digital common 1 I Analog ground 46 1 gt 5 2 gt 8052 TW p Q 9 lt H 6 C113 2 Rm R107 c 14 23 C104 N 202 gt Eo 3577 V C103 Figure 5 3 Figure 5 4 Circuit Schematic Diagram for BCD In Out Option Circuit Board Component Diagram for BCD In Out Option 45 Technical Data DTC 500A Temperature Co
8. Manual Output Control Range Full Scale Heater Current Ranges 2 Heater Resistance Maximum Power Output Ranges Controller Proportional Gain Temperature Readout Potentiometer control 0 to full scale of current setting 10mA 50mA 100mA 300mA 1A 25 Q for maximum power 3 2 5 x 10 to 25 watts in multiples of 10 4 Amp mV in automatic mode nominal Two sensor connections front panel selectable between control sensor and temperature sensing only sensor Accuracy Excitation Current Excitation Current Regulation Sensor Calibration Chart 1 4 Major Assemblies Supplied 100 microvolts calibration error of sensor and calibration error of full scale set point 10 microamperes 0 02 0 02 Must be supplied by manufacturer of sensor in use The Model DTC 500A Cryogenic Temperature Controller includes as standard equipment in addition to the controller proper the following additional components A 1 Operating and Service Manual B 2 Five pin plugs for temperature sensor cables C 1 Seven pin plug for remote set point cable Temperature sensitive diodes are not supplied as part of the DTC 500A Controller 1 5 Accessory Equipment and Custom Options Available The following accessory equipment and custom options are available from the factory Items marked with an asterisk are of a custom nature The customer should discuss these items with a factory representative bef
9. Proportional gain integral reset and derivative rate Set from front panel con trols Manual 0 to 100 of full output can be set from front panel Heater Output 0 25 watts into 25 ohm load Heater current range can be limited at 10mA 30mA 100 300mA and 1A approximate decade power increments Temperature Readout Method Sensor voltage is nulled against set point voltage using front panel thumbwheels in MANUAL mode Temperature is determined from V vs T tables requires sensor calibrated over appropriate temperature range Accuracy 100 microvolts calibration error of Sensor General Remote Set point Input 7 pin rear panel connector or optional BCD interface connector Dimensions Weight 432mm wide x 146mm high x 330mm deep 17 in x 5 in x 13 in Style L full rack package Net weight 8 2 kg 18 158 Power 105 125 or 210 250 VAC switch selected 50 or 60Hz 65 watts Accessories Supplied Mating connectors for sensor and remote inputs instruction manual 64 E Walnut St Westerville Ohio 43081 614 891 2243 Telex 24 5415 Cryotron WIVL PRINTED IN USA 481 Options and Accessories Available Model DTC BCD interface Allows remote digital control of set point and provides BCD output of Sensor voltage divided by two Model SW 10A 10 Sensor Selector Switch Pushbutton selection of any one of up to 10 sensors Dimensions 216mm wide x 102mm high x 330mm deep 8 in x 4 x 13 in Style
10. advantage ous for setting up steady state voltages where a fast response to changes in input is not reuired The circuit is described in detail in a paper by J R Stockton d Input Internal Remote Circuitry Figure 4 1 shows part of the input circuitry for the DTC 500A A simple highly linear mark space ratio digital to analog converter J R Stockton J of Physics E Scientific Instruments 1977 Vol 10 0482 The sensor select switch selects either sensor or sensor B voltage leads as indicated as well as switching the current leads not shown Note that the negative voltage lead is grounded with the current source negative and positive leads floating The sensor voltage goes through a buffer amplifier prior to being converted to a positive signal current by resistors 14 amp R15 This buffered voltage is available to the user at terminal B of J3 R13 110 ohms is present so that inadvertant shorting of this output does not destroy the buffer amplifier The INT REM switch selects between the internal set point and the external set points In its center position the internal set point and the remote set point signals if present are mixed Do not use the mix position unless you intend to use both internal and remote signals since the remote set point will tend to generate noise if no signal is present In the remote position the unused input should be grounded so as to eliminate potential sources of noise No
11. table for small errors 25 26 Table 4 1 Translation of Null error versus set point deviation as function of gain Gain Sensor Set Point Error mV div 1 70 5 36 10 7 50 3 1 100 75 500 55 1000 08 g Automatic Reset Circuit Bounding Circuit The bound circuit and variable gain integrator are realized by operational amplifiers U11 and U13 respectively A simplified equivalent circuit of the circuit is given in Figure 4 3 Note from Figure 5 1 that the amplified error signal Vo is inverted Amplifier 011 prior to being integrated by this amplifier Application of the principle that the summing junction currents must add to zero yields the overall transfer function of the stage The bounding circuit disables the integrating function for large errors when rapid corrective action is desired The memory action of integrating Capacitor C19 causes the controller to be sluggish in such transient operations The method of disabling the capacitor depends upon the sign of the error and the polarity of the voltage across 19 When the sensor voltage Vs is smaller than the set point voltage Vsp the error signal Ve Vs Vsp 0 and an over temperature condition exists The input voltage to the reset amplifier is also negative resulting in an output voltage which would integrate towards a large positive value To avoid this condition since reset is not required the diode CR6 essentially shorts the output to
12. the electrical supply common ground The common lead of the controller circuitry Lo terminal of the heater output Key 22 Fig 3 2 can be externally connected to the chassis ground terminal Although the grounding of the controller common is normal operation practice the common Lo terminal may be dis connected from chassis ground if doing so helps to eliminate accidental ground loops within the system The effect of grounding may be observed by monitoring the a c signal present on the heater circuit Choose the connection which reduces the a c signal to its lower value _ 20 0482 Table 3 2 PARALLEL BCD INPUT OF SET POINT 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 Function i Function BCD 0008 BCD 0002 BCD 0004 BCD 0001 BCD BCD 008 BCD BCD 002 BCD BCD 004 BCD 2 BCD 001 BCD 1 BCD 08 If high 5V Select Remote Set Point 4 0482 21 Table 3 3 PARALLEL BCD OUTPUT OF SENSOR VOLTAGE 2 4 6 8 1012 14 16 18 20 22 24 26 28 30 32 34 36 38 40 1 3 5 7 9 1113 15 17 19 21 23 25 27 29 31 33 35 37 39 94 1 J4 21 BCD BCD 1 DATA VALID Common Ground Note BCD output is one half of actual sensor voltage 22 0482 SECTION IV Theory of Operation 4 1 Introduction This section contains the theory of operation of the DTC 500A Controller and functional characte
13. zero is in part determined by the bounding circuit Its non linear behavior accounts for the assymetry in the temperature versus time characteristics as shown in Figure 3 4 If the instrument responds to the tests outlined above as indicated either the trouble lies elsewhere in the system or the malfunction in the controller is of a subtle nature 5 6 Calibration of Sensor Current The sensor current has been factory calibrated to 10 microamperes 10 nanoamperes To check the sensor current without removing the case cover a conveniently available precision resistance of not less than 01 tolerance should be connected to pins A B of the sensor connector socket J or Jj and the sensor selector switch on the front panel switched to the appropriate sensor input A or B The SET POINT SELECTOR switch should be switched to REMOTE and remote plug J3 be disconnected high quality potentiometric voltmeter connected to the precision resistor should measure voltage equal to 10 microamperes times the value of the resistor Typically a 100 K 01 resistor should read 1 0000 within 100 microvolts If recalibration is indicated the voltage across the precision resistors can be recalibrated after removing the case cover and adjusting trimmer R5 on the circuit board Note that due to the non linearity of the diode the adjustment of the current source does not have to be to the same level of accuracy as the measurement of voltage
14. 19 C20 C21 C22 C23 C24 C25 C26 C27 C28 C29 C30 C31 C32 01 02 03 U4 05 07 U6 U8 U9 U10 U11 U12 U13 U14 U15 U16 U17 018 019 U20 DESCRIPTION Not present 33 MFD 100V Electrolytic 33 MFD 100V Electrolytic 33 MFD 100V Electrolytic 33 MFD 100V Electrolytic Not present Not present 022 MFD 50V Mylar 150 PFD 50V Dipped Mylar 047 50V Tantalum 1 0 MFD 100V Electrolytic 0 1 MFD 100V Mylar 1 0 MFD 100V Electrolytic 1 MFD 100V Mylar 2600 MFD 50V Electrolytic 2200 MFD 16V Electrolytic 470 MFD 25V Electrolytic 470 MFD 25V Electrolytic 470 MFD 25V Electrolytic 1 MFD 100V Mylar 1 MFD 100V Mylar 470 MFD 25V Electrolytic 1 0 MFD 100V Electrolytic Not present 50 PFD 5 Dipped Mylar 0015 MFD 5 Electrolytic Presettable up down Binary Decade Presettable up down Binary Decade Presettable up down Binary Decade Presettable up down Binary Decade Presettable up down Binary Decade Dual D Edge Triggered Flip Flop Quad 2 Input NAND Schmitt Trigger Dual SPDT Low Resistance Sw Operational Amplifier Operational Amplifier Dual Operational Amplifiers Operational Amplifier Operational Amplifier Operational Amplifier Positive Voltage Regulator Negative Voltage Regulator Positive Voltage Regulator Positive Voltage Regulator Operational Amplifier Voltage Reference itch 1 5A 1 5A 1 5A 1 5A Counter Counter Counter Counter Counter
15. 1982 11 Table of Contents Section I II III IV 3 3 3 Q eneral Information 1 Introduction 2 Description and Applications 3 General Specifications 4 Major Assemblies Supplied 5 Accessory Equipment and Custom Options Available nstallation Introduction Initial Inspection Power Requirements Grounding Requirements Installation Repackaging for Shipment NNNNNNH OU 0 HR peration Instructions Introduction Controls Indicators and Connectors Initial Checks Temperature Readout Mode Constant Temperature Control Mode Manual Reset Heating Mode Temperature Readout Mode Sensor B Current Source Modification Remote Temperature Programming Remote Voltage Programming Remote Resistance Divider Programming Remote Parallel BCD Input Output Option Grounding 0 3 3 3 3 3 3 3 3 3 9 9 9 tO WANA Theory of Operation 4 1 Introduction 4 2 General Description 4 3 Detailed Description Power Supplies Diode Constant Current Supply Set Point Voltage Input Internal Remote Circuitry Summing Variable Gain Amplifier Null Meter Circuit Automatic Reset Circuit Bounding Circuit Automatic Rate Circuit Output Power Amplifier Heater Current Metering and Limiting re aoe MOAN Page Ree ATI 0482 0482 Section V aintenance and Trouble Shooting Introduction Test Equipment and Accessories General Remarks Serv
16. 500 Silicon Diode Sensors Refer to Lake Shore Series DT 500 Technical Data for complete list DT 500K or DT 500KL DT 500K TO5 DT 500KL TO5 DT 500P GR DT 500P or DT 500P GR MINI DT 500FP DT 500 CU 36 Sensor Calibrations Other ranges also available Type Range K Expanded Calibration Printout Interpolated data equal intervals over calibration range First 500 data points Each additional 1000 data points Figure 1 1 Model DTC 500A Cryogenic Temperature Indicator Controller 0482 SECTION I General Information 1 1 Introduction This section contains a description of the Model DTC 500A Cryogenic Temperature Controller its applications general specifications major assemblies supplied and accessory equipment available 1 2 Description and Applications The Model DTC 500A Cryogenic Temperature Controller is housed in an aluminum case and is rack mountable with the RM 5H rack mount kit in a standard 19 relay panel All connections are at the rear of the case with all normal operating controls on the front panel The instrument is line operated from either 115 volt or 230 volt mains 50 or 60 Hertz The controller is designed to accept a voltage signal from a temperature sensitive transducer generally a DT 500 or TG 100 Series Diode which is not supplied compare this signal with an internal set point voltage amplify and process their difference error signal and drive an external heating el
17. E position or the center MIX position Pin D of J3 is precision regulator of 6 9 volts 5 To insure maximum accuracy the total resistance between pins E D of J3 should be greater than 10 000 ohms Since the signal desired is less than 3 volts a dropping resistor R must be used to limit the voltage across the variable resistor to less than 3 volts The remote set point diagram is shown in Figure 3 5 Pin D Pin Pin E or F Equivalent Set Point network l Pin H R Ry 10K Shield 206 _ Pin E Analog Ground Figure 3 5 Remote Temperature Programming number of external temperature programming networks are shown in Figure 3 6 Re Trim Resistor A B C D Figure 3 6 Programming Networks 18 0482 1 0482 The following is a suggested procedure for designing external temperature set point control circuitry A Determine the range of desired temperature control voltage B Choose the most suitable control circuit for your application a Temperature control range 100 b Limited temperature control range c Fixed temperature set points selected in steps d Most flexible arrangement allowing for selected steps and continuously variable temperature set points Additional variations of the above may be tailored to fit the intended application C insure that the total resistance between pins E amp D of the external programming voltage divider be of the correct value to devel
18. L SET potentiometer from zero toward its maximum The current meter should increase linearly along with the advance of the MANUAL SET control With the MANUAL SET control set to give mid scale heater current meter deflection rotate the MTR CURRENT RANGE switch though all of its positions The heater current meter indication should remain approximately at mid scale in all of the positions Zero the null meter with the set point voltage controls Turn the AUTO RESET and GAIN controls to mid scale position Set the HTR CURRENT RANGE switch to 1000 Position the mode control switch to AUTO A Abruptly change the set 34 0482 _ 0482 point voltage sufficiently to cause 10 unit deflection of the NULL meter to the right The heater current meter deflection will consist of two components The first is a rapid step rise due to the steady null error and a second gradually rising component due to the AUTO RESET circuit integrating the steady error The heater current meter will gradually rise toward full scale deflection The rate at which the heater current rises is determined by the AUTO RESET time constant setting The rate is a minimum in the counterclockwise position and a maximum in the fully clockwise position Abruptly change the set point voltage to cause 10 units deflection of the NULL meter to the left The HEATER CURRENT meter should gradually decrease from full scale deflection to zero The rate at which the current meter goes to
19. L half rack package Model RM 3H Rack mount kit to mount either one or two SW 10A in standard 3 rack space Model RM 5F Rack ears with handles to mount DTC 500A in standard 5 rack space Model DT 500 Silicon Diode Sensors Refer to Lake Shore Series DT 500 Technical Data for complete list DT 500K or DT 500KL DT 500K TO5 or DT 500KL TO5 DT 500P GR DT 500P or DT 500P GR MINI DT 500FP DT 500 CU 36 Sensor Calibrations Other ranges also available Type Range K Expanded Calibration Printout Interpolated data at equal intervals over calibration range First 500 data points Each additional 1000 data points
20. LAKE SHORE PART NO CD4029 CD4029 CD4029 CD4029 CD4029 MC1413 CD4093 AD7512 15 OP15 MC1458P F741TC LF356N LF356N MC7805 MC7915 MC7815 MC7815 LN308 LM399H AE AE AE AE AE AL BE D1 39 _ 40 REF DESG 021 022 023 91 1 2 33 J4 J5 J6 211 121 1 2 CR1 CR2 CR3 CR4 CR5 CR6 CR7 CR8 CRO CR10 LAKE SHORE DESCRIPTION PART NO F E T 3N163 Not present Voltage Reference LM399H Power Transistor 2N6044 5 pin sensor socket Amphenol 5 pin sensor socket Amphenol 7 pin remote set point Amphenol 40 pin connector Heater Binding Post Heater Binding Post Chassis Ground Post Internal Wiring Header Internal Wiring Header Fuse Holder Littlefuse Fuse Holder Littlefuse Silicon Diodes Silicon Diodes 6 2V Zener Diode Semcor LMZ6 2 6 2V Zener Diode Semcor LMZ6 2 Silicon Diode Silicon Diode 1N459 Silicon Diode Bridge WLOO5 Silicon Diode Bridge WLOO5 Silicon Diode Bridge W102M Silicon Diode Bridge WO6M 0482 12 101 R102 R103 R104 R105 R106 R107 R108 R109 R110 R112 C101 C102 C103 C104 C105 C106 C107 C108 0482 PARTS LIST FOR DTC 500A Level Translator Level Translator Level Translator Level Translator Level Translator Quad AND OR Select Gate Quad AND OR Select GATE Quad AND OR Select Gate Quad AND OR Select Gate Quad AND Or Select Gate Quadruple D Type Flip Flops Quadruple D Type Flip Flops Quadruple D Type Flip F
21. The full scale output current is determined by the series combination of the heater element resistance and one of the group of resistors R70 through R72 This series combination is connected across the nominal 7 5 or 25 volt output of the power amplifier Approximately 5 volts appears across the Heater Current Meter M1 and its appropriate shunt resistor 27 Under circumstances shall the rating of fuse FU2 be increased above one ampere in an attempt to achieve a power dissipation of 25 watts in heater element whose resistance is less than 25 ohms Such substitution invalidates the instrument warranty and is likely to damage the output power amplifier circuit SC J F a 2 M SENSOR 92259 p SELECT Jo Do 0 gt BofJ2 R13 R15 7 R14 e n le 5831 SC Rie A of R17 JB4 Y 558 R18 C of O 3V 9 43 R20 JB6 T n I D A 2 R25 R2 VERTER 8 D E m REM Figure 4 1 Internal Remote Circuitry Indicating Switching and Summing of Input Signals 28 0482 x1 x10 R34 x100 R33 V R36 R32 A 5 k 1 JC7 14 R31 gt R29 GAIN C15 k 09JCS le U10 5 7 k 1 MAX GAIN k O MIN GAIN SO o OL 24 1 R 3 Ve eR15 Rg 1 15 KR o R36 R R32R3 1 SR Rat 38631 1 k Figure 4 2 Simplified E
22. User s Manual Model DTC 500A Cryogenic Temperature Indicator Controller Obsolete Notice This manual describes an obsolete Lake Shore product This manual is copy from our archives and may not exactly match your instrument Lake Shore assumes no responsibility for this manual matching your exact hardware revision or operational procedures Lake Shore is not responsible for any repairs made to the instrument based on information from this manual LakeShore Lake Shore Cryotronics Inc 575 McCorkle Bivd Westerville Ohio 43082 8888 USA Internet 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 Obsolete Manual
23. able 3 1 Table 3 1 Entry Number Correlation No Key Name Function 1 SET POINT VOLTS Digital set point of sensor voltage 0 2 9999 2 GAIN Gain Multiplier X1 X10 X100 GAIN Variable gain 1 10 Together with gain multiplier allows adjustment of overall controller gain over 1000 to 1 range Mode selector switch AUTO uses sensor A to automatically control temperature MAN A disengages automatic control feature but permits readout of sensor A voltage MAN B permits readout of sensor B voltage MAN SET When mode selector switch 4 is in either MAN A or MAN B position the MAN SET potentiometer permits the user to manually adjust the current to the heater element Caution High current settings will quickly boil away cryogenic fluids 6 AUTO RESET Adjusts auto reset time constant of integrator OFF MIN MAX See Fig 3 3 Effectively determines times constant of integrator between 100 and 1 seconds MIN and MAX respectively or OFF 9 10 10 11 12 15 14 15 16 17 18 19 20 21 RATE OFF MIN MAX POWER HTR CURRENT RANGE MILLIAMPERES REMOTE INPUT J3 HEATER CURRENT NULL INT REM 115 230 VAC 0 75 0 4 AMP NO LABEL 1 0A F B SENSOR A J1 SENSOR B J2 J4 HEATER Function Adjusts Auto rate time constant of differ entiator Effectively determines time constant of di
24. across the sensor 5 7 Zero Offset of Input Buffer Amplifier This amplifier has been trimmed at the factory and should not require immediate attention After a few months of operation it may introduce some measure ment error due to a zero offset For example a 1mV zero offset in the output would correspond to approximately a 0 4 K offset in the sensor reading above 30K where the sensitivity is approximately 2 5mV K Below 25 K where the sensitivity is approximately 50mV K this would result in an appreciably smaller error 35 This offset may be zeroed as indicated below A Allow 20 minutes for warm up of the controller B Make shorting plug so that Pins E and D the sensor input voltage leads to the buffer amplifier are shorted Place this shorting plug in J1 C Mode switch Key No 4 to MAN D Use a HIGH input impedance voltmeter to monitor output of buffer amplifier The ground connection is Pin D of J1 The output connection is pin 6 of U9 E Adjust trim R10 so that the amplifier offset is less than 100yuV 5 8 Zero Offset of Summing Amplifier This amplifier has also been trimmed at the factory and should not require immediate attention In order to zero the offset of this amplifier it is nec essary to first zero the offset of the input buffer amplifier Section 5 7 With the shorting plug in place J1 and no other inputs to the summing amplifier i e no inputs to J3 or J4 set the digital set point to 0 0000 volts
25. al set point to read second sensor This is accomplished by adjusting the output current Key No 5 such that the heater current Key No 10 does not vary when switched from Auto to MAN or MAN B Key No 4 3 7 Temperature Readout Mode Sensor In some applications the temperature is controlled or regulated at one physical location while it 15 desired to measure the temperature at second location This requires two sensors Sensor A located at the temperature control point and Sensor at the second point where only the temperature is to be measured Sensor B must be calibrated 3 8 Current Source Modification The current source within the DTC 500A is floating and presently excites either Sensor A or Sensor B depending on the switch position of the mode selector switch Key No 4 A simple wiring change can be made so that both Sensors A and B are excited simultaneously if either or both sensors are electrically isolated from a common ground With the instrument lid removed unsolder the wire to Pin A Sensor B connector and resolder to Pin A Sensor A connector unsolder the wire to Pin B Sensor A and resolder to Pin B Sensor B connector now two wires on this terminal Now solder a wire between Pin B Sensor A connector and Pin A Sensor B connector The two sensors are now connected in series If you wish to use only Sensor A make up a shorting plug for Sensor B terminal that shorts Pin A to Pin B For so
26. calibration curve for the transducer in use will then give its temperature 1 3 General Specifications The following specifications for the DTC 500 A Controller are applicable when used with the TG 100 or DT 500 full range temperature sensitive diodes 1 2 2 General Controller Range Heater Output Sensor Sensor Input Sensor Current Input Line Voltage Power Consumption Circuit Design Weight Dimensions Sensitivity Temperature Control Set Points Control Accuracy Setpoint Repeatability Control Modes Manual Control Automatic Reset Rate 0 0001 volt to 2 9999 volts 1 K to 400 K for DT 500 series diodes 25 watts maximum Models DT 500 or TG 100 temperature sensitive diodes single ended or floating models Four terminal connection constant current potentiometric 10 microamperes 115V or 230V 50 60 Hz 65 watts Solid State 8 2kg 18 1bs 54 high 17 wide 13 deep v4 Amp millivolt into 25 0 resistor at maximum setting internal O to 3 0 volts via 5 digital thumbwheels Remote Analog 0 to 3 0 volts Digital optional parallel BCD 0 0005 K 1 to 28 K in a properly 0 005 28 to 400 designed system for DT 500 series diodes 100 microvolts Proportional gain integral reset and derivative rate 0 to 100 of full output 1 to 100 second variable time constant or off 1 to 100 second variable time constant or off 0482 1 0482
27. e at the new constant value required to maintain the desired temperature A sketch of the temperature versus time pattern described above is given in Figure 3 4 Observe that there is no temperature overshoot or oscillation when the GAIN and AUTO RESET controls are properly adjusted This statement presupposes that the sample holder heater and sensor may be accurately modeled as a simple R C type time constant thermal circuit If oscillation or overshoot are observed when changing the set point voltage in small increments reduce the GAIN and increase the AUTO RESET time constant rotate CCW settings until oscillations are no longer observed and or adjust the HTR CURRENT RANGE Key No 9 to a lower setting Normally at cryogenic temperatures the above adjustments will result in a stable system with good transient response due to the short time constants encountered at these temperatures For these constants the rate switch should remain in an off position If however the transient response of the system must be improved this can be done by the addition of rate or derivative to the control functions Physically the effect can be described as introducing anticipation into the system The system reacts not only to the magnitude and integral RESET of the error but also its probable value in the future If the error is changing rapidly then the controller responds faster The net result is to speed up the response of the system
28. egulator U 15 supplies the 5 volts used for the BCD option only P S 5 is an unregulated supply for the output power stage The output voltage is 25 volts on the one ampere scale and approximately 7 5 volts for all lower current settings b Diode Constant Current Supply A precision reference voltage is generated by an internally tempera ture stabilized precision voltage reference U23 Resistors R3 thru R6 vary this voltage to match the voltage generated by feedback resistor R7 Resistor R7 has been selected to generate 4 99V across it when the output current is 10 microamperes Op amp 419 drives an FET U21 to generate a current flow through Pins A and B of the selected input sensor connector This current is varied by trimpot R5 The entire constant current supply system was designed to be fully floating so that the cathode of the sensor diode might be returned to common c Set Point Voltage The digital set point consists of a digital to analog converter which is linear to approximately lppm Its accuracy is obtained by a simple symmetrical application of the mark space ratio principle A single up down counter chain is used which alternately counts down to zero and up to the maximum from the value to be converted The first of these intervals is used for the mark time the second for the space time the sum of the two being independent of the input value This circuit has a response time of approximately one second and is
29. ement An internal precision 10 microampere constant current source is provided to excite the temperature transducer The error processing section of the controller is of the proportional plus integral and differential mode design Generous amplifier gain ranges have been provided to affect rapid closed loop response times low steady state temperature offsets and to insure system stability over a wide range of thermal system parameters The output power amplifier is capable of supplying up to 25 watts of heater power In view of the high cost of some cryogenic fluids such as helium cost consciousness suggests that cryostat design and operating strategies be planned to limit heater power requirements to substantially less than twenty five watts The principal intended application of the DTC 500A Controller is as a constant temperature regulator for laboratory size cryostats Its basic design however enables it to be used as a general purpose controller for sensors whose outputs range between 0 and 3 0 volts and whose incremental sensitivities are in the range of tenths of millivolts or greater In addition to its use as a closed loop automatic temperature controller the Model DTC 500A Controller may be used as a precision thermometer By adjusting the set point voltage so that the error signal as indicated by the null meter is zero the output voltage of the temperature sensor is accurately obtained Reference to a voltage versus temperature
30. ference source Although one point calibration as described above is sufficient it may be desirable to check several points In that case precision rheostat may be used for R at the sensor input connector However the leads as well as the divider resistor should be shielded and the shields connected to pin H of the sensor A input connector 71 Similarly the leads and box housing the externally programmable temperature resistance network should be shielded through pin H of external set point plug J3 3 9 3 Remote Parallel BCD Input Output Option The remote programming option consists of a TTL parallel 18 bit input of set point voltage and a TTL parallel 17 bit output of one half of the sensor voltage It is assumed that the sensor voltage output can be multiplied by two within the computer The cable pin out connectors are indicated in Tables 3 2 and 3 3 Both the internal and external BCD input of the set point is accomplished either in the INTERNAL or position by setting connector Ja pin 38 high 5V for external BCD or low 0 V for internal BCD Both internal and external BCD set points are disabled in the REMOTE position Note that in the MIX position either BCD set point can be combined with an external signal from connector 23 0 The BCD output of one half of the sensor voltage is present in all modes INTERNAL MIX and REMOTE 3 10 Grounding The chassis is grounded by the 3 lead power cable to
31. fferentiator between 1 and 100 seconds MIN and respectively or OFF 2 line switch ON OFF and pilot light Switch selected current selector Use of low setting will avoid inadvertent boil off in setting up system and or system oscillations Monitors heater element current Full scale deflection corresponds to MAX HEATER AMP switch 9 setting Indicates the difference between the set point voltage and the sensor output voltage Meter is non linear for large errors of either sign See page 23 and 24 for discussion Selects between internal set point and remote set point The center position allows mixture of both set points Front panel set point inoperative with switch in REMOTE position A C line voltage selector slide switch 50 60 Hz A C line fuse FUl See para 2 3 115 VAC 0 75 AMP 230 VAC 0 4 AMP A C line cord Heater element line fuse 1 AMP Fast Blow Sensor A cable receptacle Five pin Amphenol type 126 217 Plug Sensor B cable receptacle Five pin Amphenol type 126 217 Plug Remote set point either by means of 0 to 3 volt signal or a potentiometer Amphenol 126 195 Plug 40 pin connector for REMOTE BCD in out option Heater element lead terminals Grey is the high side and Black is the low side 0482 7 GROUND NO LABEL Function Chassis ground terminal 23 Heat sink for output transistors 3 3 Ini
32. for Printed Circuit Board Circuit Schematic Diagram for BCD In Out Option Circuit Board Component Diagram for BCD In Out Option Parts List for DTC 500A Page 12 12 15 16 18 18 19 21 22 26 28 29 30 31 32 43 43 45 45 37 0482 0482 Specifications DTC 500A Cryogenic Temperature Controller input Temperature Range 1 4 to 380K with Lake Shore DT 500 Series Sensors 0 to 3 0 volts for other sensors Recommended Sensors DT 500 Series Silicon Diode Sensors order separately Calibration required over appropriate temperature range to provide V vs T data Sensor Input Dual sensor input 4 terminal input for each sensor Can be connected in 2 wire configuration Sensor position is used for automatic control mode Sensor or B positions are used in manual mode for temperature readout or manual control Sensor Excitation 10 microampere current source Temperature Control Set Point Internally selected via 5 front panel digital thumbwheel switches from 0 0000 to 2 9999 volts Externally selectable via either resistance 0 to 1000 ohms or voltage 0 to 3 volts Optional BCD control with DTC BCD Interface Set Point Resolution 1004 V Typical Controllability 0 0005K for temperatures from 1 4 to 28K 0 005K at higher temperatures in a properly designed system Control Modes Automatic Proportional gain integral reset and derivative rate Set from front panel con trols Manual
33. g the voltage will move the meter pointer to the left decreasing the set point voltage will deflect the meter pointer to the right After centering the meter the set point voltage can be read directly to 100 uvolts table of relative sensitivity for the null meter as a function of gain setting is given on page 26 After determining the set point voltage refer to the diode calibration chart to ascertain the diode temperature 1 0482 cre en FIGURE 3 2 DTC 500A Cryogenic Temperature Controller Rear FIGURE 3 1 DTC 500A Cryogenic Temperature Controller Front Panel Panel 0482 WHTTIONLNOO FUNLVYYANEL VOOS DLA WYHDVIG 001 83 YYNSIA HlVd NOVACHYY TVWHHHL gt gt gt gt 16 31033 14 135 TINN gt WSp LNAKETA VILVYH N Ga e Ee Fre YLLIN sie 02 02 000 2 aounos ap ee Se _ 13 0482 3 5 Constant Temperature Control Mode Assume that calibrated diode is in use as described in paragraph 3 4 To maintain a constant temperature determine the corresponding set point voltage from the diode calibration chart Set this voltage on the SET POINT switches Position controls as indicated below A Temperature set point switch Key No 12 to INTERNAL B Mode switch Key No 4 to AUTO C MANUAL SET Key No 5 to one D CURRENT RANGE Key No
34. ground If however the sensor voltage is larger than the set point voltage Vsp the error signal is positive and an under temperature condition exists If the input voltage Vo Avl Ve lt 2 volts then the output voltage of the comparator Ull is 15 volts The integrator is therefore disabled since the diode 85 is contrasting with its anode close to 14 volts For an input signal Vo between zero and two volts the integrator is operational and ultimately once the system is controlling and stable the voltage developed across C19 becomes just equal to the error voltage Vo which is required to hold a constant temperature under open loop conditions Since this voltage is now present on the capacitor of the reset amplifier it is no longer needed at the output of the gain summing amplifier resulting in the error signal reducing to zero 0482 0482 The switch in series with R77 in the feedback loop is closed when the AUTO RESET control is in the off position and the amplifier gain is approximately 001 h Automatic Rate Circuit For most cryogenic applications the addition of rate will not greatly enhance the system response However in some applications rate will improve response The simplified circuit and transfer function are shown in Figure 4 4 Note that an output is only present for a rapidly changing input signal and that the time constant varies from 1 85 to 187 seconds With the AUTO RATE switch closed the ci
35. heater element fuse FU2 Key No 16 Pg 12 for proper value 3 AG 1 0A Fast Blow or smaller current rating if desired This fuse pro tects the output amplifier from damage in case of heater element shorting Use of larger fuse may cause damage to the instrument and invalidates the instrument warranty 2 6 Repackaging for Shipment Before returning an instrument to the factory for repair please discuss the malfunction with a factory representative He may be able to suggest sev eral field tests which will preclude returning a satisfactory instrument to the factory when the malfunction is elsewhere If it is indicated that the fault is in the instrument after these tests the representative will send shipping instructions and labels for returning it When returning an instrument please attach a tag securely to the instru ment itself not on the shipping carton clearly stating A Owner and address B Instrument Model and Serial Number C Malfunction symptoms D Description of external connections and cryostats If the original carton is available repack the instrument in plastic bag place in carton using original spacers to protect protruding controls and close carton Seal lid with paper or nylon tape Affix mailing labels and FRAGILE warnings If the original carton is not available wrap the instrument in protect ive plastic wrapping material before placing in an inner container Place shock absorbing material arou
36. i xm 28 17 1 NE Ar BC BC 89 20K Trim Pot D A Converter Adjust Not present 100K Trim Pot Summer Zero Not present 10K Pot Gain Control 8 25K 1 96 M 100K 1K 10K Not present 1 0K 1 0K 3 92K 20K 2 8K kW 57 XV 1 17 1 8W 1 0 57 XV 1 XV 1 1 8V 1 17 5 37 38 REF DESG R41 R42 R43 R44 R45 R46 R47 R48 R49 R50 R51 R52 R53 R54 R55 R56 R57 R58 R59 R60 R61 R62 R63 R64 R65 R66 R67 R68 R69 R70 R71 R72 R73 R74 R75 R76 77 R78 R79 R80 LAKE SHORE DESCRIPTION PART NO 2 8K ZW 5 1 xW 1 14 7K XVI 1 2 0L 1 10 LW 5 1 96 M 17 100K Pot Reset Control 8 06K kW 17 1 27 1 1 96 1 10 10 866 ohm kW 17 100 Pot Rate Control 866 ohm kW 17 200K kW 17 100 17 10 Pot Manual Reset Control 82 5K kW 1 Not present Not present Not present Not present Not present 422 ohm 1W 54 9 ohm 1W 16 9 ohm 1W 4 97 ohm 1W 1 64 ohm 1W 498 ohm 1W 715 ohm 1W 360 ohm 1W 81 6 ohm 1W 62 ohm 1 1 5 XVI 20 Not present 150K 1 100 ohm kW 1 1470 ohm 1 174 1 2150 1 33 25V Mylar 150 PFD 10V Dipped Mylar Not present 2 2 MFD 35V Metal Tantalum Not present 1 MFD 100V Mylar 0482 4 0482 REF DESG C7 C8 C9 C10 C11 C12 C13 C14 C15 C16 C17 C18 C
37. ibrating the DTC 500A Controller 5 3 General Remarks Upon initial installation the single most probable cause of system mal function is an improperly connected temperature sensing diode If it is impossi ble to zero the null meter at any setting of the set point voltage controls carefully examine the cable diode assembly to insure that the diode polarity is correct that the sensor is plugged into the SENSOR receptacle and that the SET POINT SELECTOR switch is in the INTERNAL position Because of the highly reliable solid state design of the controller it is most unlikely that the controller will be source of difficulty For this reason it is advisable to examine other portions of the cryogenic system before testing the controller proper Some suggested checks are A Open or shorted sensor and heater leads particularly in the vicinity of the sample holder if it is subject to frequent dis assembly B Leakage paths between heater and sensor leads giving rise to electri cal feedback in addition to thermal feedback Premature loss of cryogenic fluid due to thermal shorts in dewar ice blocks in lines sample holder immersed in cryogen sample holder in vapor whose temperature is above the controller set point temperature etc D Excessive thermal path phase lags will cause the control loop to be unstable at high gain settings Physical separation between the diode and heater particularly by paths of small thermal cros
38. icing Printed Circuit Boards Operational Checks Calibration of Sensor Current Zero Offset of Input Buffer Amplifier Zero Offset of Summing Amplifier M 5 5 5 5 5 5 5 5 5 Adjustment of the Digital Set Point Ul B 111 Reference Figure 1 1 Figure 2 1 Table 3 1 Figure 3 1 Figure 3 2 Figure 3 3 Figure 3 4 Figure 3 5 Figure 3 6 Figure 3 7 Table 3 2 Table 3 3 Table 4 1 Figure 4 1 Figure 4 2 Figure 4 3 Figure 4 4 Figure 4 5 Figure 5 1 Figure 5 2 Figure 5 3 Figure 5 4 Table 5 1 Table of Illustrations Description Model DTC 500A Cryogenic Temperature Indicator Controller Sensor and Heater Cables Entry Number Correlation Front Panel Rear Panel Block Diagram DTC 500A Temperature Controller Temperature versus Time Characteristics of Controller Remote Temperature Programming Programming Networks Programming Voltage Parallel BCD Input of Set Point Parallel BCD Output of Sensor Voltage Translation of Null Error versus Set Point Deviation Internal Remote Circuitry Indicating Switching and Summing of Input Signals Simplified Equivalent Circuit and Transfer Function of Gain Summing Amplifier Simplified Equivalent Circuit of Automatic Reset Amplifier Simplified Equivalent Circuit of Automatic Rate Amplifier Circuit Schematic for Power Stage Showing Switching of Full Scale Current Circuit Schematic Diagram Parts Layout
39. level which induces oscillations After achieving a stable operating point reduce the HTR CURRENT RANGE Key No 9 to a lower setting As lower settings are dialed in the percent 5 of maximum heater current being used should increase The optimum area for control can be obtained by keeping the meter pointer between 0 2 and 0 7 on the meter face 14 0482 Abruptly increase the set point voltage ten millivolts The sensor voltage now represents temperature warmer than that represented by the set point voltage The NULL meter should deflect to the left and the HEATER CURRENT should go to zero immediately As the sample holder cools the NULL METER pointer should return toward zero As the NULL METER pointer approaches zero the HEATER CURRENT will increase from zero to the new steady state value required to maintain the sample at the lower temperature requested The NULL METER should read zero as the HEATER CURRENT stabilizes at its new value Now abruptly decrease the set point vernier control by ten millivolts The sensor voltage now represents a temperature colder than that represented by the set point voltage The NULL meter should deflect to the right and the HEATER CURRENT meter should deflect toward full scale As the sample holder heats the NULL meter pointer will tend to zero and the HEATER CURRENT meter reading will decrease toward its new steady state value As the NULL meter centers the HEATER CURRENT should stabiliz
40. lops Quadruple D Type Flip Flops Quadruple D Type Hex Buffers Drivers with open collector Table 5 1 BCD I O Option DESCRIPTION TTL to Logic High MOS TTL to Logic High MOS TTL to Logic High MOS TTL to Logic High MOS TTL to Logic High MOS Flip Flops High Voltage Outputs Hex Quadruple 2 Input Positive And Gates Interface Analog to Digital Converter Interface Analog to Digital Converter 866 Inverter 1 8w 100K 1 8w 100K 1 8w 300K 35 7 100 Tr 5490 law 100 1 Not 14K Present 1822 1 8w 0 1 68 Not 300 22 68 Not 360 MFD 100V MFD 100V present PFD MFD 100V MFD 100V present MFD 1 17 12 17 17 17 17 Mylar My Polypropylene My lar lar LAKE SHORE PART NO F4104 BPC F4104 BPC F4104 BPC F4104 BPC F4104 BPC SIL 4019 BC SIL 4019 BC SIL 4019 BC SIL 4019 BC SIL 4019 BC 74LS175N 74LS175N 74LS175N 74LS175N 74LS175N D53630N MM 74C14N 74LS08N ICL 7103 ACPI ICL 8052 ACPD 41 REF LAKE SHORE DESG DESCRIPTION PART NO C109 1 MFD 100V Mylar C110 1 100V Mylar C111 1 100V Mylar C112 2 2 MFD 35V Tantalum C113 2 2 MFD 35V Tantalum CR101 Diodes 1 5 V IN125 CR102 Diodes 1 5 V IN125 1 42 0482 597 9 ot I 115 230 VAC L2 1 C26 230 15 V I 5V CCM I he 5 g15V MI L ANALOG Ao 3311
41. me applications a constant current other than 10 wA is desired This constant current is programmed by means of the following formula 1 4 99 R7 with R5 being a trim for this current For 10 mA R7 is 499K for 100 pA R7 must be 49 9K current source can be programmed between 1 and 1 mA if desired The compliance voltage is slightly less than 5 volts 3 9 Remote Temperature Programming Three types of remote programming are acceptable by the DTC 500A They are A An analog signal from 0 to 3 volts standard B An external resistance divider standard C A parallel BCD set point including an A D converter with parallel BCD output of one half of the sensor voltage option Remote temperature control can be achieved by applying either A or B of the above signals and switching the SET POINT to the REMOTE position or the center MIX position In the MIX position the remote signal and the internal set point are added directly The BCD set point replaces the front panel set point in the INTERNAL position 17 3 9 1 Remote Voltage Programming To apply a remote voltage signal to the DTC 500A connect a 0 to 3 volt signal between Pin E and Pin the analog ground of the REMOTE INPUT connector J3 on the rear panel of the unit 3 9 2 Remote Resistance Divider Programming Remote temperature control can 150 be achieved by connecting an external resistance divider to J3 and switching the SET POINT to the REMOT
42. nd all sides of the instrument to prevent damage to protruding controls Place the inner container in a second heavy carton and seal with tape Affix mailing labels and FRAGILE warnings 0482 0482 Do not ground shield voltage sense current supply current supply A RECOMMENDED SENSOR CABLE Do not ground shield RE or M JA VET 25 Ohm J5 heater element BLACK ces 1 RECOMMENDED HEATER CABLE Do not ground shield C ALTERNATE SENSOR CABLE FIGURE 2 1 SENSOR AND HEATER CABLES 0482 SECTION III Operating Instructions 3 1 Introduction This section contains a description of the operating controls their adjust ment under normal operating conditions typical controller applications and suggested cryostat adjustment techniques These instructions are predicated upon the instrument having been installed as outlined in Section II The diode polarity as shown in Fig 2 1 a in particular must be correct A calibrated diode is assumed to be connected as shown in Fig 2 1 to the Sensor A receptacle and a 25 ohm heating element is assumed to be connected to the Heater terminals as shown in Fig 2 1 b 3 2 Controls Indicators and Connectors The operating controls indicators and connectors on the instrument s front and rear panels are shown in Fig 3 1 and 3 2 The numbers with leaders to various controls in the figures are keyed to the entries in T
43. ntroller a Versatile Precision Thermometer Controller Provides Ultra Stable Cryogenic Temperature Control Lake Shore Cryotronics Inc CRYOGENIC TEMPERATURE CONTROLLER bun MODEL DTC 500A REMOTE INTERNAL ABOVE NULL BELOW SENSOR TEMPERATURE SET POINT SELECTOR INTERNAL SET POINT VOLTS VARIABLE Features 1 4 to 380K Range True Three Mode Control Uses Silicon Diode Sensors 100 V Set Point Resolution Manual Heater Override 0 25 Watt Heater Output Optional BCD Interface The Lake Shore Cryotronics Model DTC 500A is the top of the line Temperature Controller for use with all DT 500 Series Silicon Diode Temperature Sensors True three mode control gain rate and reset is com bined with premium spec components to allow system control as stable as 0 5 millikelvin below 28K and 5mK at higher temperatures The DTC 500A utilizes any Lake Shore DT 500 Series silicon diode Sensor calibrated Sensors are recommend ed for optimum accuracy and versatility A built in 10 microampere source provides the Sensor excitation current The voltage signal from the Sensor is then com pared to the set point and the error signal is amplified to provide the heater drive Use of analog control means constant and immediate correction for temperature changes Ample range of gain reset and rate have been designed into the 500A to assure fast response low offset error and high stability Controllability to 0 5mK Below
44. o 10 sensors can be connected to either of the dual inputs on the DTC 500A Selection is made via front panel pushbuttons on the SW 10A For the ultimate in stability and versatility in cryogenic temperature measurement and control turn to the Lake Shore Cryotronics DTC 500A tete qttod EEE gt gt gt COPYRIGHT 1981 Lake Shore Cryotronics Inc Specifications DTC 500A Cryogenic Temperature Controller Input Temperature Range 1 4 to 380K with Lake Shore DT 500 Series Sensors 0 to 3 0 volts for other sensors Recommended Sensors DT 500 Series Silicon Diode Sensors order separately Calibration required over appropriate temperature range to provide V vs T data Sensor Input Dual sensor input 4 terminal input for each sensor Can be connected in 2 wire configuration Sensor position is used for automatic control mode Sensor or B positions are used in manual mode for temperature readout or manual control Sensor Excitation 10 microampere current source Temperature Control Set Point Internally selected via 5 front panel digital thumbwheel switches from 0 0000 to 2 9999 volts Externally selectable via either resistance 0 to 1000 ohms or voltage 0 to 3 volts Optional BCD control with DTC BCD Interface Set Point Resolution 1004 V Typical Controllability 0 0005K for temperatures from 1 4 to 28K 0 005K at higher temperatures in a properly designed system Control Modes Automatic
45. op a drop of 3 volts across the programming resistor it is suggested that the divider calculation be based on more than 1600 ohms per 1 volt and a shunting resistor RT in Fig 5 6 used for precision trimming to 3 volts The 3 0 volts can be measured with a precision floating voltmeter with the sensor circuit open i e sensor plugs disconnected or calibrated with the DTC 500A internal set point volts switch as follows a Connect a precision known resistor R any value between 50K 250K to the pins AE and BD of the Sensor A input plug 21 Amphenol type 126 217 or equivalent in place of the sensor as shown in Fig 5 7 and turn the sensor selector switch on the front panel to Manual A position A E RE 0 3 Shield D Figure 3 7 Programming Voltage J1 The voltage drop across resistor R is equal to 10 x 1079 amperes R ohms volts thus a 100 K ohm resistance would result in a 1 volt drop With the TEMPERATURE SET POINT switch in INTERNAL position the null meter will indicate zero error when the internal temperature set point switch on the front panel is at 1 000 volts Increase the gain to maximum and adjust the internal set point if necessary for the null meter to indicate zero Move the reference set point switch to EXTERNAL position and adjust trim resistor RT on the external set point programming instrument so that the null meter reads zero The external programming network is now matched to the internal re
46. ore ordering A Extra 5 and 7 pin connectors 3 Multisensor selector panel Special low thermal offset switch and cabling for selecting among multiple sensors Custom modification of sensor current supply value DT 500 Silicon Temperature Sensitive Diode or TG 100 Gallium Arsenide uncalibrated See data sheets at end of this manual for nominal operating characteristics and case styles available DT 500 Silicon Temperature Sensitive Diode or TG 100 Gallium Arsenide calibrated Standards laboratory calibration service for correlat ing diode output voltage with diode temperature See sensor data sheet for additional information Also see Cryogenic Calibration Service data sheet Power boosters for heater power requirements in excess of twenty five watts or other than twenty five ohm heater resistance BCD Input Output Optional Include parallel BCD input of set point and a parallel BCD output of sensor voltage Model RM 5F rack ears with handles to mount DTC 500A in standard 55 high 19 wide rack space 0482 20482 SECTION II Installation 2 1 Introduction This section contains information and instructions necessary for the installation and shipping of the Model DTC 500A Cryogenic Temperature Con troller Included are initial inspection instructions power and grounding requirements installation information and instructions for repackaging for shipment 2 2 Initial Inspection This inst
47. quivalent Circuit and Transfer Function of Gain Summing Amplifier 29 0482 V __ V gt 1 RESET SWITCH YT SEC OFF 0 0014 MIN k 0 1 43 MAX k 1 145 Figure 4 3 Simplified Equivalent Circuit of Automatic Reset Amplifier 30 0482 OFF R54 MAX R51 R53 RATE OFF MIN R52 17 R50 gt Vg 1 1 SRC 1 1 17 Regt 1 5 0CI7 RATE SWITCH 7 SEC OFF 225107 MIN k O 1 85 MAX k 1 187 Figure 4 4 Simplified Equivalent Circuit of Automatic Rate Amplifier 0482 ES 3 9195 1104 BZuyyo rms 28 35 103 5 3Ino3IO 6 nd 9 INNE 9f ZLY LYF OLY 2 o 3 ee op 91pe T lt 2 9 024097 0482 32 0482 SECTION Maintenance and Troubleshooting 5 1 Introduction This section contains instructions for maintaining and calibrating the controller nominal voltage values and gains circuit schematic diagram printed circuit board component diagram and parts list 5 2 Test Equipment and Accessories An RCA Senior Voltohmyst vacuum tube voltmeter or an equivalent high input impedance digital voltmeter a 25 ohm 25 watt resistor to simulate the heater element and precision resistor connected to simulate the diode in a connector assembly wired according to Fig 2 1 c are normally sufficient for testing and cal
48. rcuit is effectively dis abled from the controller since the gain is less than 1077 i Output Power Amplifier The output power stage consists of a summing amplifier and two stages of voltage amplification an output switching network and a variable supply voltage First note that on the one ampere scale the supply voltage is 25 volts while on all other maximum current ranges the supply voltage is approximately 7 5 volts The voltage at the input of 012 is V e fedt 46 The overall gain of the summing amplifier is Broken up into settings Since R39 R56 R55 20K the gain for the 1 ampere setting is R79 R58 20K R58 20K 2 5 12 The gain for the other four settings is j Manual Heater Control When the mode selector switch is set to either MAN A or MAN B position switch section SlE connects tbe input of the power amplifier stage to the wiper of potentiometer R57 through resistor R74 Varying the wiper position from zero to its maximum will vary the output voltage at the emitter of 01 from 0 to 25 volts on the 1 ampere scale and from 0 to 7 5 volts for all other current selectors The heater element current is thus varied proportionally to the setting of R57 and the maximum heater current switch 54 position k Heater Current Metering and Limiting The heater element current is measured by the heater current ammeter shunted by resistor R65 through R69 as appropriate for the current range selected
49. rization of the controller in Laplace transform notation to aid the thermal system designer in system stability analysis In some applications it may be required for an experienced user to modify the gain reset or rate range The information given within this section should make these modifications straightforward 4 2 General Description Refer to Figure 3 3 and Figure 5 1 as an aid in the following discussion precision constant current source causes 10 microamperes of DC current to bias the control diode The voltage developed across the control diode is fed through a buffer amplifier and this voltage generates positive current through the 3 megohm resistor into the current summing amplifier The digital set point is converted to an analog voltage by the five digit D A converter The resulting voltage is negative and an appropriate resistance string is chosen so that its current into the summing amplifier just balances the sensor generated positive current The result is zero current at the summing junction when the set point voltage is just equal to the sensor voltage Because current summing operational amplifier is used many signals can be mixed together Therefore the digital set point signal can be mixed with the remote signals described in Section 3 9 The gain of the controller is built into this summing operational amplifier A simplified equivalent circuit of this amplifier is shown in Figure 4 2 The associated switching f
50. rom sensor to sensor B and the switching associated with the internal and remote switch are shown in Figure 4 1 From Figure 4 1 it can be seen that the error signal is a current which is amplified as voltage by the variable gain operational amplifier U10 of Figure 4 2 The amplified error is displayed on the NULL meter and also applied through an inverter to 1 an integrator circuit reset 2 a bound or clamping circuit and 3 a differentiator circuit rate The error signal its integral and differential are summed as current by the operational amplifier U12 This amplifier then drives the output power circuit The current from the power amplifier is metered by the current meter Changing the current range from 10mA to 1 Amp changes the voltage gain of the output stage from 0 2 to 20 Closed loop control action is achieved through the thermal path between the heater element and the temperature sensing diode 1 0482 23 24 4 3 Detailed Description a Power Supplies There are four regulated supply voltages within the DTC 500A They are designated P S 1 through P S 4 Figure 5 1 5 1 consisting of a diode bridge and regulator U 18 supplies a regulated 15 volts and an unregulated 18 volts to the circuit comprising the constant current source P S 2 and P S 3 consist of a diode bridge with regulators Ul7 and amp 16 which supply 15 volts and 15 volts respectively P S 4 con sisting of a diode bridge and r
51. rument was electrically and mechanically inspected prior to shipment It should be free from mechanical damages and in perfect working order upon receipt confirm this the instrument should be inspected visu ally for obvious damage upon receipt and tested electrically by use to detect any concealed damage Be sure to inventory all components supplied before discard ing any shipping materials If there is damage to the instrument in transit be sure to file appropriate claims with the carrier and or insurance company Please advise the company of such filings In case of parts shortages please advise the company The standard Lake Shore Cryotronics warranty is given on the first page of this manual 2 3 Power Requirements Before connecting the power cable to the line ascertain that the line volt age selector switch 115V or 230V is in the appropriate position for the line voltage to be used Examine the power line fuse FUI Key No 14 Page 12 to insure that it is appropriate for the line voltage 115V 0 75 Amp 230V 0 40 Amp Nominal permissible line voltage fluctuation is 10 at 50 to 60 Hz CAUTION Disconnect line cord before inspecting or changing line fuse 2 4 Grounding Requirements To protect operating personnel the National Electrical Manufacturers Association NEMA recommends and some local codes require instrument panels and cabinets to be grounded This instrument is equipped with a three conductor power cable
52. s section should be avoided E Examine heater element fuse FU2 If it is indicated that the controller is malfunctioning after performing the tests to be described below it is recommended that the instrument be returned to the factory for repair The components used in the instrument are costly and may be permanently damaged if subjected to inappropriate test voltages or excessive soldering iron heat Although premium materials and techniques have been used to 33 fabricate the instrument circuit board there is always the risk of lifting a connection pad or cracking the board when unsoldering a component 5 4 Servicing Printed Circuit Boards It is suggested that components be unsoldered for trouble shooting only as a last resort since ample information is available at the numbered terminal pins Attempt to infer component currents by voltage tests rather than removing a lead and seriesing it with an ammeter All voltages are available for measure ment from the top side of the printed circuit board When it is necessary to replace a component access is available by removing the bottom cover Use a low heat 25 to 50 watts small tip freshly tinned soldering iron Use small diameter rosin core solder Remove a component lead by applying heat to the lead observing the solder melt and then pulling the lead through the board from the top side Never apply tension to printed wiring from the bottom side Thoroughly clean all of the old
53. solder from the mounting hole before insert ing a new component with the use of a wick or desoldering suction device Shape the new component and insert in mounting hole Do not use heat or force to insert the new component If the leads will not go through the hole file the lead or clean the hole more thoroughly Once mounted properly apply heat to lead and wiring pad simultaneously and resolder Clean excess flux from the connection and adjoining area with warm water and weak detergent if need be Contamination in some areas of the board can seriously degrade the high input impedance of the operational amplifiers 5 5 Operational Checks Replace the sensor diode connector plug with a test plug made up according to Fig 2 1 c Substitute a precision resistor for the sensor diode in the test plug Remove the heater element leads and place a twenty five watt twenty five ohm resistor across the heater output terminals Ten microamperes flowing through the test resistor should develop a potential of 1 00 volts across a 100 K ohm resistor With the gain set a maximum position and the mode selector switch in position MAN A assuming the test plug is in SENSOR A receptacle attempt to null the error with a set point voltage in the vicinity of 1 0 volts The null meter should swing smoothly as the set point voltage is varied in the vicinity of the null While still in the MAN A position set the HTR CURRENT RANGE switch at 1000 Vary the MANUA
54. te that all external signals must be negative as well as the internal set point At null the current from the sensor is just balanced by the negative current s from its set point s resulting in error signal which is dependent on the gain setting for no reset and zero for the normal operation when reset is engaged e Summing Variable Gain Amplifier simplified unit for the summing amplifier is shown in Figure 4 2 Capacitors C14 and C15 are present for high frequency stability Since all input currents flow through equal resistors an equivalent error voltage signal is i R15 with Ry either 10K or IK The gain of this amplifier varies from 2 to 2000 depending on the position of the variable gain potentimeter and gain multiplier switch Not shown in Figure 4 2 is the null resistor R 30 and the trim re sistor R27 The trimming of this amplifier is described in Section 5 8 CR3 and CR4 are 6 8 volt zener diodes which are present to keep the amplifier out of saturation due to extraneous noise spikes also not shown Null Meter Circuit Directly after the variable gain summing amplifier is the null meter circuit The Null Meter is desensitized for large errors by placing two germanium diodes across its terminals The result is a linear scale for error less than 50 of full deflection in either direction with high non linearity for larger errors Sensor set point error in null can be related to gain settings by the following
55. tial Checks Initial checks calibration checks and servicing procedures are described in Section V MAINTENANCE 3 4 Temperature Readout Mode To use the DTC 500A as a cryogenic thermometer to measure the temperature of calibrated diode connected to SENSOR terminals initially position switches and controls as follows Temperature set point switch Key No 12 to internal INT B Mode switch Key No 4 to MAN A C MANUAL SET Key No 5 to one D CURRENT RANGE Key 9 to 10 E GAIN Key No 2 and 3 to minimum setting F RESET Key No 6 to off G RATE Key No 7 to off H POWER switch Key No 8 to on The null meter will probably deflect off scale either left or right when the power switch is turned on If the deflection is to the right the set point voltage is less than the sensor voltage If the deflection is to the left the set point voltage is greater than the sensor voltage In other words in order to null the meter turn the set point in the direction that you wish the needle to move If the null meter will not null regardless of the set point voltage check to make sure that the printed circuit card located behind the thumbwheel digits has not worked loose from its proper position during shipping This can be easily observed by removal of the ton cover Adjust the set point voltage until the NULL meter is centered wh le increasing the GAIN toward maximum Increasin
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