Model DTC-500SP - Lake Shore Cryotronics, Inc.
Contents
1. 4 9f 4 avs e e LL 20 695899956 2 s E 1599 cod DYS e amp sp 8 75 e o f VW 0001 OOE OOLOE Ol OG vis amp e m lt oca 6LH2 N G S d LG eme 33 SECTION V 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 a precision resistor connected to simulate the diode in a connector assembly wired according to Fig 2 1 c are normally sufficient for testing and calibrating the DTC 500SP Controller 5 5 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 TEMPERATURE SET POINT switch is in the INTERNAL position Because o2. C ALTERNATE SENSOR CABLE FIGURE 2 1 SENSOR AND HEATER CABLES SECTION III Operating Instructions 53 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 calibrated diode is assumed to be connected as shown in Fig 2 1 a to the Sensor A receptacle and a 25 ohm heating element is assumed to be connected to the 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 Table 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 5 GAIN Variable gain 1 10 Together with gain multiplier allows adjustment of overall controller gain over 1000 to 1 range 4 MAN B MAN A Mode selector switch AUTO A uses sensor AUTO A A to automatically control temperature MAN A disengages automatic control feature but permits readout of sensor A voltage
3. 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 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 cord located behind the thumbwheel digits has not worked loose from its proper position during shipping This can be easily observed by removal of the top cover Adjust the set point voltage until the NULL meter is centered while increasing the GAIN toward maximum Increasing 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 24 After determining the set point voltage refer to the diode calibration chart to ascertain the diode temperature 10 M 5 Wo S y E Z CO
4. MAR ener Nutt A AERC A O ES ee rini ENTER spre tei m OREN I AE ETN NEE DD TCA SERIES DTC TEMPERATURE CONTROLLERS Technical Specification DTC 500SP MEDECIN eM etu ete oT M NN HEU er ITE DE RAIL NM RESP TSO FEIT VRAT LATINA ELE TT NO rele P C e I GZ zi gt Sea 2 er a a ANY ARA Pt Pr ER DRESS SL T ORNS OA UNS RUNS TIER RITE e AAS ARS lI ISAT AAA AO A Ce RV Nee e CALI LE p Tr iC vtt AC NIORT Ga B RIT AI Ee ER al NR CAN mL m m EET RR AA ARE TER NOD INE SNE PIS ruere WO R eran ear ur MODEL DTC 500SP ULTRA STABLE PRECISION CRYOGENIC TEMPERATURE INDICATOR CONTROLLER 1 to 400 Kelvin Range Digital Set Point True Three Mode Control Controllability of 0 0005 1 to 28 Kelvin 0 005 28 to 400 Kelvin Silicon Diode Sensor Programmable BCD Input Output Optional 0 40 Watt Output SSYyOOir C BTU Foy o TART The Model DTC 500SP Ultra Stable Precision Cryogenic Temperature Controller is the latest State of the art con troller designed for use with the proven DT 500 Series Silicon Diode Sensors The use of high quality components and true three mode proportional integral and derivative control allow control to 0 0005K between 1 and 28 Kelvin and 0 005 Kelvin between 28 and
5. 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 37 _ uorado 404 303 Juauodwoj pavog S TUNDIA 15 5 9915 8 on Ln n 6n on O O 5 ign 20 En vn GN x Q zm 8 195 18 _ 6 gt SER FABER Pan Ce BL LH 41 5 9 Parts List Component Location Diagram and Schematic Table 5 1 PARTS LIST FOR DTC 500SP DESCRIPTION 3 92K kW 1 8250 ohm 1 499 1 8W 1 3 75K 1 8W 1 SK Trim Pot constant current adjust 10K xW 0 5 499K xW 1 3 83K xW 1 Not present 100K Trim Pot Buffer Zero Not present Not present 1 xW 1 100K xW 1 909K xW 1 1M xW 1 10K W 14 1 M xW 1 Not present 100K xW 1 845K xW 1 amp 23K xW 1 423K xW 1 93 1K 1 20K Trim Pot D A Converter Adjust Not present 100K Trim Pot Summer Zero Not present 10K Pot Gain Control 8 25K xW 5 1 96 M xW 1 LOOK xW 1 1 1 8W 1 ZW 0 5 Not present 1 02K xW 1 1 xW 1 3 92K 1 8W 1 20K
6. Introduction Test Equipment and Accessories General Remarks Servicing Printed Circuit Boards Operational Checks Calibration of Sensor Current Zero Offset of Input Buffer Amplifier Zero Offset of Summing Amplifier Adjustment of the Digital Set Point Appendices 11 Reference Figure Figure T ble Figure Figure Figure Figure Figure Figure Figure Table Table Table Figure Figure Figure Figure Figure Figure Figure Figure Figure Table Ls 2 3 5 2 1 21 1 1 2 5 5 4 5 5 3 6 5 7 5 2 5 5 4 1 4 1 4 2 4 5 4 4 4 5 Du 1 5 2 5 3a b 5 4 5 1 Table of Illustrations Description Model DTC 500SP Cryogenic Temperature Indicator Controller Sensor and Heater Cables 7 Entry Number Correlation 8 9 10 Front Panel Rear Panel 12 Block Diagram DTC 500SP Temperature Controller 13 Temperature versus Time Characteristics of Controller 16 Remote Temperature Programming 18 Programming Networks 18 Programming Voltage 19 Parallel BCD Input of Set Point 21 Parallel BCD Output of Sensor Voltage 22 Translation of Null Error versus Set Point Deviation 26 Internal Remote Circuitry Indicating Switching and Summing of Input Signals 29 Simplified Equivalent Circuit and Transfer Function of Gain Summing Amplifier 30 Simplified Equivalent Circuit of Automatic Reset Amplifier 31
7. 3 y L Ee 9 7 V SET POINT 77 CHASSIS GROUND THUMBWHEEL SWITCHES DIGITAL GROUND SHOR ens o SHORE RYGTRORKS Westerville Ohio 43081 SCHEMATIC DIAGRAM 252 9 500 SP APP D DATE SIZE DRWG NO REVISION 078001 HERUM MANET RR R55 RATE 55 8 REO C RI ex R5 ca E R27 t O CR4 NE E IIO O x R42 U5 04 U3 02 U1 U6 U7 U8 cm em n LE Rao Rg C 79 1 O OOO OP 0O00 OO OO O O O OO O O O O 9 O OOO O O OPO R O 26 gej C22 J1 Je Q ra Fososeacvedpeososocescsed 12 R20 tera R77 R30 8 deem gie u 529 qc O 0 e 44 c l R47 R53 THUMBWH W lt ss ITEM QTY PART OR P NO LIST OF MATERIALS ona ae mores OBW LRHE SHORE AVOTRORILS int 1 gt esterv 03 X xxx 005 lO 13 80 e Ohio 43081 TE DIC 500 SP MACHINE FINISH BREAK SHARPCORNERS R E REMOVE ALL BURRS E DT COMPON E T S AYOU T DO NOT SCALE DRAWING EMEN SIZE DR REVISION WG NO NEXT CUSTOM PROTO PROD USED MATERIAL BEAL C 12 80 01 REMOTE J 7 5K V ies TC S NL o 15v 81 8 11254 81112 54 oo 8111254 4104
8. Shield lt 3 volts Pin E Andlog Ground Figure 3 5 Remote Temperature Programming A number of external temperature programming networks are shown in Figure 3 6 oD oD SE Rr Trim Resistor A B C D Figure 3 6 Programming Networks 18 The following is a suggested procedure for designing external temperature set point control circuitry Determine the range of desired temperature control voltage 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 To insure that the total resistance between pins E amp D of the external programming voltage divider be of the correct value to develop 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 3 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 500SP internal set point volts switch as follows a Connect a precision known resistor R any va
9. Simplified Equivalent Circuit of Automatic Rate Amplifier 32 Circuit Schematic for Power Stage Showing Switching of Full Scale Current 33 Circuit Schematic Diagram 38 Parts Layout for Printed Circuit Board 39 Circuit Schematic Diagram for BCD In Out Option 40 Circuit Board Component Diagram for BCD In Out Option 41 Parts List for DTC 500SP 42 111 SECTION I General Information 1 1 Introduction This section contains a description of the Model DTC 500SP Cryogenic Temperature Controller its applications general specifications major assemblies supplied and accessory equipment available 1 2 Description and Applications The Model DTC 500SP Cryogenic Temperature Controller is housed in an aluminum case with standard 19 relay panel front for rack mounting 11 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 element 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 p
10. W 1 2 8K xW 5 LAKE SHORE PART NO 42 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 R77 R78 R79 R80 C1 C2 C5 C6 LAKE SHORE DESCRIPTION PART NO 2 8K W 5 1 xW 1 14 7K 1 2 0K ZW 1 10K xW 5 1 96 M 1 100K Pot Reset Control 8 06K 17 1 27 M 1 1 96 1 10 10 866 ohm xW 1 100K Pot Rate Control 866 ohm LW 1 200K kW 1 200K xW 1 10K Pot Manual Reset Control 82 5K 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 5KM xW 20 Not present 150K xW 1 100 ohm xW i 1470 ohm xW 1 165K xW 1 215 ohm 1 33 MFD 25V Mylar 118 PFD 10V Dipped Mylar Not present 2 2 MFD 35V Metal Tantalum Not present 1 MFD 100V Mylar 43 REF DESG C7 C8 C9 C10 C11 C12 C13 C14 C15 C16 C17 C18 C19 C20 C21 C22 C23 C24 C25 C26 C27 C28 C29 C30 C31 C32 U1 U2 U3 U4 U5 U6 U7 U8 09 010 011 012 013 014 115 016 017 018 019 020 DESCRIPTION Not present 27 f 100V Electrolytic 27 MFD 100V Electrolytic 27 MFD 100V Electrolytic 27 100V Electrolytic 1 MFD 100V Mylar Not prese
11. 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 11 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 solder from the mounting hole before insert ing a new component with the use of a wick 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 Contami
12. 14 Abruptly increase the set point voltage by ten millivolts The sensor voltage now represents a 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 stabilize 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 a
13. 2 5mV K Below 25 K where the sensitivity is approximately 50mV K this would result in an appreciably smaller error 56 This offset may be zeroed as indicated below A Allow 20 minutes for warm up of the controller B Make a shorting plug so that Pins E and D the sensor input voltage leads to the buffer amplifier are shorted Place this shorting plug in 1 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 100uV 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 J4 set the digital set point to 0 0000 volts Adjust the trim potentiometer 2750 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 to 250 Let us assume that the resistor has the value 100 010 ohms
14. 910 31546 T TT Tr TS IL pte 10 TTS v dE wu p oe O s r r 5v lift 25 J6 C O C O C D CC OA O 1 B O 1 C 2 O 1 D SET POINT IN J6 A 1 J4 38 SET PT INT SET PT INT 1 EXT 25 NOTE J4 IS LOCATED ON REAR PANEL J6 IS LOCATED ON PC BOARD iil 4019 5 16 kia leer EFH IE R Rn c 1 O INT REMOTE 7939 1B LAKE SHORE CRYOTRONICS ME pe E Westerville Ohio 43081 Dh eim PCO IN OPTION Lu SCHEMATIC cie DRWG NO REVISION Cl NRM 0 5V J4 Bi 3 82 01 295 2 23 LSD 4 O B3 E B452 2 0 07 8 0 DV 3 0 9 100 5 011 198 D 013 140 0 _ 5V 017 180 3 919 200 7 C 921 220 6 240 gt O 5v 025 260 2 227 eo a B 029 309 5 31 s E 033 MSD 340 0 VA 36 389 REMOTE CONTROL 400 NC GROUNDING 7 DIGITAL GND N ANALOG GND 035 DATA VALID 7939 1 SO e LAKE SHORE CRYOTRONICS INC NOTE J4 IS LOCATED ON REAR PANEL R OZ Bo pu 5 see OY Hu EE ES APP D DATE SIZE DRWG NO REVISION
15. MAN B permits readout of sensor B voltage 5 MAN RESET When mode selector switch 4 is in either MAN or MAN B position the MAN RESET 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 No Key 10 11 12 13 14 15 16 17 18 19 20 21 OFF MIN MAX POWER F S CURRENT AMPS 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 REMOTE INPUT J3 J HEATER Function Adjusts Auto rate time constant of differ entiator Effectively determines time constant of differentiator between 1 and 100 seconds MIN and respectively or A C line switch and pilot light Switch selected current selector Use of a 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 e
16. 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 Note 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 A 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 V i R15 with Rg 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 are the null resistors R19 R26 R28 and the trim resistor R27 The trimming of this amplifier is described in Section 5 8 and CR4 are 6 8 volt zener diodes which are present to keep the amplifier out of saturation due to extraneous noise spikes f 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 lin
17. 15 V JB3 _ S2C A of 9 R17 364 w 86 528 R18 Cof 0 3 J4 R20 I I SA R22 R21 D AO 2 bal 0 0 gt CON R25 R2 VERTER TE INT REM FIGURE 4 1 Internal Remote Circuitry Indicating Switching and x10 R34 x100 R33 V R36 R32 A gt O 7 1 R37 J R29 GAIN C15 K O 9JC8B le Vo GAIN k 1 _ MIN GAIN R36 R32R34 ACR Rar fr Rg R36 R29 1 Figure 4 2 Simplified Equivalent Circuit and Transfer Function of Gain Summing Amplifier 30 CR5 R R 432944 _ F2 RAG 15V OFF V R75 CR6 e OF MIN R49 2 MAX V 48 _ 1 V 1 47 RE 1 7 2 gt R49C19 RESET SWITCH 7 SEC Vi mss 5004 CET ev MIN k O 1 43 1 14 5 Figure 4 3 Simplified Equivalent Circuit of Automatic Reset Amplifier 31 OFF V R54 MA X R53 OFF MIN C17 R50 V Ng 1 SRE4C 1 Rz4 k Rea xn pul 7 7 5 1 RATE SWITCH T SEC OFF 22x107 MIN k 0 1 85 MAX k 1 187 Figure 4 4 Simplified Equivalent Circuit of Automatic Rate Amplifier 32 IN3N3 13 Y3LV jueiin e eog IINA JO 7 862 BUTMOYS 9881S
18. 400 Kelvin in a properly designed system The controller is designed to accept the output from a diode temperature sensor compare this output to an internal or external set point value process and amplify the difference error signal and drive an external heating element The error processing section of the controller is of the proportional integral and derivative mode design Generous amplifier gain ranges have been provided to effect rapid closed loop response low steady state temperature offsets and to ensure system stability over a wide range of thermal system parameters The controller output power amplifier is capable of supplying up to 40 watts of heater power which is adequate for the majority of applications An output current selector switch allows control of the maximum amount of power that can be supplied by the controller The Model DTC 500SP may also be used in an open loop mode with a calibrated DT 500 sensor for temperature measurement by manually adjusting the digital set point selector until the null meter is zeroed The temperature is then determined by comparing set point voltage values to the V vs T curve of the calibrated sensor Two sensor inputs are provided on the controller with a selector switch on the front panel allowing one to select one sensor for control or the second sensor normally calibrated for temperature readout The Model DTC 500SP allows the use of either the internal set point control or accept
19. 5K 100 100K 300K 35 7K 100K 5490 1 8w gt Trim pot Not Present Not Present 14K 182 1 100V Mylar 68 MFD 100V Mylar low 1 8w 1 5 MFD 300 MFD 22 MFD 100V Polypropylene 68 MFD 100V Mylar Not present 360 MFD 12 15 LAKE SHORE PART NO F4104 BPC 4104 F4104 4104 4104 BPC SIL 4019 SIL 4019 BC SIL 4019 BC SIL 4019 BC SIL 4019 BC 741 5175 741 5175 741 5175 741 5175 741 5175 SN7417N MM 74C14N 74LS08N ICL 7103 ACPI ICL 8052 ACPD 46 REF DESG C109 C110 C111 C112 C113 CR101 CR102 l MFD 100V l MFD 100V l MFD 100V 2 2 MFD 35V 2 2 MFD 35V Diodes DESCRIPTION Mylar Mylar Mylar Tantalum Tantalum V Diodes 1 5 V LAKE SHORE PART NO 4 L1 15 230 VAC 230 E jo 06 5V COM O RB 6 95v V QUE p N 7 C ANALOG Ao 5 1 vi 15VBo l L 2 D R13 R14 15V 78 F 52 R16 R15 R17 S B R16 Q owl L O 0 LJ 15019 J R20 2 15V 110 30 100 300 1000 MA e fT S4A V SoA R23 822 Ral R25 9 INT REM wo BIS T 340 C14 SBB CHEATER ELEMENT lt jx GAIN 1 1O 100 V la o la O U v N N NP O N gt N n Ro 2 OO LJ 22 0 O0 C
20. EATER CUR switch to 1 amp Position the mode control switch to AUTO A Abruptly change the set 35 point voltage sufficiently to cause a 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 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 As an aid in trouble shooting in the latter case typical voltages and gains under specified conditions are given in Section 5 10 5 6 Calibration of Sensor Current The sensor current has be
21. L 1979
22. SA eamus wma 01 T3NVd LNOUA aj 60r Femera I g II 11 0c THNVd amp 2 6 9 8 4 c 12 UH TIOULNOD SunlVWadWHl 45005 21 WvusvIG X2018 9 13 HLVd X0Vv8aagdd TVNHHHL oda d tek amat A1OWId _ 3OVvI3OA por LAS w P1 A UALVAH ene WEZ KE NN AL 394105 UdLVAH LNGTWHDD INVISNOO _ 3 5 Constant Temperature Control Mode Assume that a calibrated diode is in use as described in paragraph 3 4 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 A C MAN RESET Key No 5 to zero D F S CURRENT AMPS Key No 9 to 1 0 AMP E GAIN Keys No 2 and 3 to minimum settings F RESET Key No 6 to off G RATE Key No 7 to off 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 p
23. User s Manual Model DTC 500SP Cryogenic Temperature Indicator Controller Obsolete Notice This manual describes an obsolete Lake Shore product This manual is a 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 aD A LakeShore Lake Shore Cryotronics Inc 575 McCorkle Blvd 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 O
24. ance of an external analog set point from an analog programmer It is also possible to select a set point mode where the external set point is adjusted about an internally selected set point value An optional BCD Input Output Option allows the use of an external BCD in put for computer control of the set point A BCD Output of the sensor voltage allows the computer to see the actual control temperature and thus allows direct computer control of temperature The Model DTC 500SP is housed in an aluminum case with a standard 19 front panel for convenient relay rack mounting All connections are made at the rear of the case with all normal operating controls positioned on the front panel PRINTED IN U S A APRIL 1979 GENERAL Range Sensor Sensor Input Sensor Excitation Voltage Input Power Consumption Construction Weight Dimensions TEMPERATURE CONTROL Set Points Control Accuracy Setpoint Repeatability Control Modes Manual Control Heater Current Ranges Heater Resistance for Maximum Power Maximum Output TEMPERATURE READOUT Accuracy Sensor Calibration APPLICATION DATA SPECIFICATIONS 1 to 400 Kelvin DT 500 Series Silicon Diode 4 terminal connection constant current potentiometric 10 microamperes 115 V 230V 50 60Hz 65 watts Solid state electronics 8 2kg 18 Ibs 13 3cm 574 high 48 3cm 19 wide 26 5cm 10 7 16 deep Internal 0 to 3 0 Volts via 5 Digital thumbwhe
25. and 017 which supply 15 volts and 15 volts respectively P S 4 consisting of a diode bridge and regulator 015 supplies the 5 volts used for the option only P S 5 15 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 Power supply P S 1 and operational amplifier A1 constitutethe main components in the diode constant current supply Due to the high input impedance of the operational amplifier A1 the diode current is forced to flow through resistor R5 developing 4 99V at 10 microamperes The voltage across R5 is therefore equal to the voltage at the inverting input terminal of A1 with a voltage of 4 99V applied to the non inverting input of Al by the reference circuit of R1 R2 R3 R4 and CR5 The current through R5 4 99 K will maintain the regulated current through sensor to 10 microamperes 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 consist of a digital to analog gonverter which is linear to approximately lppm Its accuracy is obtained by 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 conve
26. at 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 circuit is effectively disabled from the controller since the gain is less than 10 5 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 Since fedt de dt for R39 R55 R56 20K the voltage gain associated with the summing amplifier U12 is R58 20K 5 Writing a mode equation at 1 yields 2VI VI R59 20K R63 Ip Ip2 Duo A x Vo SVI VI VO SV R61 20K 9K Vo 20 VI Therefore on the 1 ampere scale the voltage gain is 20 and the voltage drop across R69 is 0 5 volts so that 40 volts is available across the load resistor if the input signal is 2 volts The voltage gain of the power stage is reduced for all other current settings For example on the 10mA scale the voltage gain is 20 140 13 8 13 0 6 where I 10mA The input signal for full scale is therefore I40 0 6 0 24 volts j Manual Heater Control When the mode selector switch is set to either MAN A or MAN B position switch section S1F connects
27. aterials 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 page ii 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 FU1 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 which when plugged into an appropriate receptacle grounds the instrument 2 5 Installation The DTC 500SP 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 500SP Controller to an ambient temp
28. bsolete Manual 1980 Table of Contents Section I General Information 1 1 Introduction 1 1 2 Description and Applications 1 1 3 General Specifications 1 1 4 Major Assemblies Supplied 5 1 5 Accessory Equipment and Custom Options Available 3 II Installation 2 1 Introduction 5 2 2 Initial Inspection 5 2 3 Power Requirements 5 2 4 Grounding Requirements 5 2 5 Installation 5 2 6 Repackaging for Shipment 6 III Operation Instructions 3 1 Introduction 8 3 2 Controls Indicators and Connectors 3 3 Initial Checks 10 3 4 Temperature Readout Mode 10 3 5 Constant Temperature Control Mode 14 3 6 Manual Reset Heating Mode 17 3 7 Temperature Readout Mode Sensor 17 3 8 Current Source Modification 17 3 9 Remote Temperature Programming 17 5 9 1 Remote Voltage Programming 17 3 9 2 Remote Resistance Divider Programming 18 3 9 3 Remote Parallel BCD Input Output Option 20 3 10 Grounding 20 IV Theory of Operation 4 1 Introduction 25 4 2 General Description 23 4 3 Detailed Description 24 a Power Supplies 24 b Diode Constant Current Supply 24 Set Point Voltage 24 d Input Internal Remote Circuitry 24 e Summing Variable Gain Amplifier 25 f Null Meter Circuit 25 g Automatic Reset Circuit Bounding Circuit 26 h Automatic Rate Circuit 27 i Output Power Amplifier 27 k Heater Current Metering and Limiting 28 Section V VI Maintenance and Trouble Shooting 1 Qn UT UT UT UTUT Won Os R W
29. ccurately 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 F S CURRENT AMPS Key 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 lso 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 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 change in gain may be necessary to eliminate oscillat
30. ction 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 around 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 Do not ground shield A RECOMMENDED SENSOR CABLE Do not ground shield J GREY 40 Ohm J5 heater element BLACK Me PEE 1 B RECOMMENDED HEATER CABLE Do not ground shield
31. ear 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 table for small errors 25 Table 4 1 Translation of Null error versus set point deviation as a function of gain Gain Sensor Set Point Error mV div 1 70 5 36 10 7 50 3 1 100 slo 500 55 1000 08 g Automatic Reset Circuit Bounding Circuit The bound circuit and variable gain integrator shown in Figure 5 3 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 U11 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 C19 When the sensor voltage Vs is smaller than the set point voltage Vsp the error signal Ve Vs Vsp o and an over temperature condition exists The input voltage to the reset am
32. ed or regulated at one physical location while it is desired to measure the temperature at a second location This requires two sensors Sensor 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 5 8 Current Source Modification The current source within the DTC 500SP is floating and presently excites either Sensor A or Sensor B depending on the switch position of the mode selector switch Key 4 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 and resolder to Pin Sensor B connector now two wires on this terminal 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 some applications a constant current other than 10 is desired This constant current is programmed by means of the following formula I 4 99 R7 with RS being a trim for this current For 10 R7 is 499K for 100 uA R7 must be 49 9K The current source can be programmed between 1 uA and 1 mA if desired The compliance voltage is sli
33. ed 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 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 5 2 and 3 3 Both the internal and external BCD input of the set point is accomplished either in the INTERNAL or MIX position by setting connector J4 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 external signal from connector 71 The BCD output of one half of the sensor voltage is present in all modes INTERNAL MIX and 3 10 Grounding The chassis is grounded by the 3 lead power cable to the electrical supply common ground The common lead of the controller circuitry Lo terminal of the heater output Key 21 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 mounting t
34. els External Analog 0 to 1000 ohms or 0 3 0 volts Digital optional serial or parallel BCD 0 0005 Kelvin 1 to 28 Kelvin x 0 005 Kelvin 28 to 400 Kelvin 50 microvolts Proportional gain integral and derivative 0 to 100 of full output 10 mA 30 mA 100 mA 300 mA 1A In a properly designed system 40 ohms 40 watts 0 to 400 volts O to 1A into 40 ohm load Two sensor capability control sensor and sample sensor 100 microvolts calibration error of sensor Must be calibrated over desired readout range 1 Uncalibrated sensors are acceptable for control mode only Sensors must be calibrated for temperature readout mode 2 Sensors can be wired into controller in 2 or 4 lead connection although 4 lead connection is recommended 3 Power cable sensor leads and Remote Temperature Control are wired into the rear of the chassis 4 Use of an additional switch not supplied with the DTC 500SP can be used for temperature readout of additional sensors if desired Input from this switch would be wired into the Sensor B input in rear of chassis Switch should be free of contact resistance and be shorting type 5 Sensors must be ordered separately as they are not included with the DTC 500SP as a part of the instrument price 6 See Lake Shore Cryotronics Inc Bulletin installation and Application Notes for Cryogenic Sensors for installa tion instructions for temperature sensors PRINTED IN U S A APRI
35. en factory calibrated to 10 microamperes 10 nanoamperes check the sensor current witbout 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 and the sensor selector switch on the front panel switched to the ppropriate sensor input A or B The TEMPERATURE SET POINT switch should be switched to REMOTE and remote plug J3 be disconnected A high quality potentiometric voltmeter connected to the precision resistor should measure a voltage equal to 10 microamperes times the value of the resistor Typically 100 K 01 resistor should read 1 0000 within 100 microvolts If recalibration is indicated the voltage across the precision resistors can recalibrated after removing the case cover and adjusting trimmer R5 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 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 lmV 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
36. er Output Ranges 4 x 10 73 to 40 watts in multiples of 10 Controller Proportional Gain 4 Amp mV in automatic mode nominal Temperature Readout Two sensor connections front panel selectable between control sensor and temperature sensing only sensor ccuracy 100 microvolts calibration error of sensor and calibration error of full scale set point Excitation Current 10 microamperes 0 02 Excitation Current Regulation 0 02 Sensor Calibration Chart Must be supplied by manufacturer of sensor in use 1 4 Major Assemblies Supplied The Model DTC 500SP 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 500SP 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 before ordering A Extra 5 and 7 pin connectors Multisensor selector panel Special low thermal offset switch and cabling for selecting among multiple sensors Custom modification of sensor current supply value DI 500 Silicon Tempera
37. erature in excess of 50 C 122 F As with any precision instrument it should not be subjected to the shock and vibrations which usually accompany high vacuum pumping systems The recommended cable diagrams for the sensor diode and heater element are given in Figure 2 1 a and b The use of a four wire diode connection is highly recommended to avoid introducing lead IR drops in the voltage sensing pair which is translated into a 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 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 a 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 malfun
38. f the highly reliable solid state design of the controller it is most unlikely that the controller will be a 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 C Premature 1055 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 cross 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 31 fabricate the instrument circuit board
39. ghtly less than 5 volts 5 9 Remote Temperature Programming Three types of remote programming are acceptable by the DTC 500SP They are A An analog signal from O to 3 volts standard B An external resistance divider standard C A parallel BCD set point including an A D converter with parallel BCD 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 3 9 1 Remote Voltage Programming To apply a remote voltage signal to the DTC 500SP connect a 0 to 3 volt signal between the analog ground E and Pin A 17 3 9 2 Remote Resistance Divider Programming Remote temperature control can also be achieved by connecting an external resistance divider to J3 and switching the SET POINT to the REMOTE position or the center position Pin D of J3 is a precision regulator of 6 9 volts 55 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 C Pin Equivalent Set Point network L_s Pin H
40. he a c signal present on the heater circuit Choose the connection which reduces the a c signal to its lower value 20 Pin J 14 J4 74 10 12 14 16 18 20 8 Table 3 2 PARALLEL BCD INPUT OF SET POINT 10 12 14 16 18 20 22 24 26 9 11 13 45 17 19 21 23 25 Function BCD BCD BCD BCD BCD BCD BCD BCD BCD BCD 0008 0002 0004 0001 008 002 004 001 08 02 Pin J4 J4 J4 14 44 J4 J4 J4 J4 28 2 22 24 26 28 30 32 34 36 38 40 30 32 34 36 38 40 29 31 33 35 37 39 Function BCD 04 BCD 01 BCD 8 BCD 2 BCD 4 BCD 1 BCD 2 BCD 1 If high 45V Select Remote Set Point 21 PARALLEL BCD OUTPUT OF SENSOR VOLTAGE Table 3 3 2 4 6 8 1012 14 16 18 20 22 24 26 28 30 32 34 36 38 40 l 3 5 7 9 1113 15 17 19 21 23 25 27 29 31 33 35 37 39 Pin J4 J J J J J J J J J Note 11 13 15 17 19 Function BCD BCD BGD BCD BCD BCD BCD BCD BCD BCD BCD output is 0001 0002 0004 0008 001 002 004 008 01 02 one half of actual J4 J4 J4 J4 J4 J4 J4 J4 J4 J4 Pin Function BCD 04 BCD 08 BCD 1 BCD 2 BCD 4 BCD 8 BCD 1 Common Ground sensor voltage 22 SECTION IV Theory of O
41. ion or overshoot 15 programmed set point temp sample holder temp new set pt temp d gt 2 EN tantaneous temp error set pt LL L instan p temp 1 time of abrupt change in set pt temp programmed set point temp initial set pi sample holder temp temp instantaneous temp error new set pt s temp time time of abrupt reduction in set pt temp FIGURE 3 4 TEMPERATURE VERSUS TIME CHARACTERISTICS OF CONTROLLER 3 6 Manual Reset Heating Mode By placing the mode selector switch Key No 4 in either position MAN A 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 F S CURRENT AMPS switch Key No 9 The current supplied to the heater is indicated on the HEATER CURRENT meter The full scale reading of the meter corresponds to the F S CURRENT AMPS switch setting RESET allows the user to hold a temperature for a short period of time in an open hoop condition while he uses the null meter and the digital set point to read a 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 A to MAN A or MAN B Key No 4 3 7 Temperature Readout Mode Sensor B In some applications the temperature is controll
42. ith the TG 100 or DT 500 full range temperature sensitive diodes 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 2 18 155 5 high 19 wide 11 deep rack mounting v4 Amp millivolt into 40 Q resistor at maximum setting internal 0 to 3 0 volts via 5 digital thumbwheels Remote Analog 0 to 5 0 volts Digital optional parallel BCD 0 0005 K 1 to 28 K in a properly 0 005 28 to 400 K i 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 Manual Output Control Range Potentiometer control 0 to full scale of current setting Full Scale Heater Current Ranges 10mA 30mA 100mA 300mA 1A Heater Resistance e 25 Q for maximum power Maximum Pow
43. ither sign See page 23 and 24 for discussion Selects between internal set point and remote set point The center position allows a mixture of both set points Front panel set point inoperative with switch in position A C line voltage selector slide switch 50 60 Hz A C line fuse See para 2 3 115 VAC 0 75 AMP 230 0 4 A C line cord Heater element line fuse 1 AMP Fast Blow Sensor cable receptacle Five pin Amphenol type 126 217 Plug Sensor B cable receptacle Five pin Amphenol type 126 217 Plug J2 Remote set point either by means of 0 to 3 volt signal or a potentiometer Amphenol 126 195 Plug J3 40 pin connector for REMOTE BCD in out option Heater element lead terminals Grey is the high side and Black is the low side No Key Name Function 22 GROUND Chassis ground terminal 23 NO LABEL Heat sink for output transistors 3 3 Initial Checks Initial checks calibration checks and servicing procedures are described in Section V MAINTENANCE 3 4 Temperature Readout Mode To use the DTC 500SP as a cryogenic thermometer to measure the temperature of a calibrated diode connected to SENSOR A terminals initially position switches and controls as follows A Temperature set point switch Key No 12 to internal INT B Mode switch Key No 4 to MAN MAN RESET Key No 5 to zero D F S CURRENT AMPS Key No 9 to 0 01
44. lue between 50K 250K to the pins AE and BD of the Sensor 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 0 4 Shield H D Figure 3 7 Programming Voltage Jl The voltage drop across resistor R is equ l to 10 x 1076 amperes x 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 19 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 reference source Although one point calibration as described above is sufficient it may be desirable to check several points In that case a 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 Ji Similarly the leads and box housing the externally programmable temperature resistance network should be shield
45. lus 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 forty watts The principal intended application of the DTC 500SP 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 5005P Controller may be used as a precision thermometer 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 calibration curve for the transducer in use will then give its temperature 1 3 General Specifications The following specifications for the DTC 500SP Controller are applicable when used w
46. mming operational amplifier simplified equivalent circuit of this amplifier is shown in Figure 4 2 The associated switching from sensor A 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 a 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 5 a differentiator circuit rate The error signal its integral and differential are summed as current by the operational amplifier 012 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 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 23 4 3 Detailed Description a Power Supplies There are four regulated supply voltages within the DTC 5008P They are designated as P S 1 through P S 4 Figure 5 1 5 1 consisting of a diode bridge and regulator U18 supplies a regulated 15 volts and an unregulated 18 volts to the Lake Shore Cryotronics constant current source 5 2 and P S 3 consist of a diode bridge with regulators U16
47. nation 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 forty watt forty 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 MAXIMUM HEATER AMP switch at 1 amp Vary the MAN RESET potentiometer from zero toward its maximum The current meter should increase linearly along with the advance of the MAN RESET control With the MAN RESET control set to give mid scale heater current meter deflection rotate the MAX HEATER AMP switch through all of its positions The heater current meter indication should remain approxmately 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 MAX H
48. nce LM399H Q1 Power Transistor 2N6044 1 5 pin sensor socket Amphenol J2 5 pin sensor socket Amphenol J3 7 pin remote set point Amphenol J amp 40 pin connector J5 Heater Binding Post 16 Heater Binding Post J7 Chassis Ground Post F1 Fuse Holder Littlefuse F2 Fuse Holder Littlefuse CR Silicon Diodes CR2 Silicon Diodes CR3 6 2V Zener Diode Semcor LMZ6 2 amp 6 2V Zener Diode Semcor LM26 2 CR5 Silicon Diode CR6 Silicon Diode 1N459 CR7 Silicon Diode Bridge WLOO5 CR8 Silicon Diode Bridge WLOO5 CRI Silicon Diode Bridge WLOO5 CR10 Silicon Diode Bridge WO6M U17 U20 R101 R102 R103 R104 R105 R106 R107 R108 R109 R110 R112 C101 C102 C103 C104 C105 C106 C107 C108 Level Translator TTL Level Translator TTL Level Translator TTL Level Translator TTL Level Translator TTL PARTS LIST FOR DTC 500SP Table 5 1 BCD I O Option DESCRIPTION to Logic High MOS to Logic High MOS to Logic High MOS to Logic High MOS to Logic High MOS 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 Quadruple Quadruple Quadruple D Type Flip Flops D Type Flip Flops D Type Flip Flops D Type Flip Flops Hex Buffers Drivers with open collector High Voltage Outputs Hex Inverter Quadruple 2 Input Positive And Gates Interface Analog to Digital Converter Interface Analog to Digital Converter 7
49. nt 022 MFD 50V Mylar 150 PFD 50V Dipped Mylar 047 MFD 50V Tantalum 1 0 MFD 100V Electrolytic Not present 1 0 MFD 100V Electrolytic 1 MFD 100V Mylar 2600 MFD 50V Electrolytic 2700 MFD 25V 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 50 PFD 5 Dipped Mylar 0015 MFD 5 Electrolytic Presettable up down Binary Decade Counter Presettable up down Binary Decade Counter Presettable up down Binary Decade Counter Presettable up down Binary Decade Counter Presettable up down Binary Decade Counter Dual D Edge Triggered Flip Flop Quad 2 Input NAND Schmitt Trigger Dual SPDT Low Resistance Switch Operational Amplifier Operational Amplifier Dual Operational Amplifiers Operational Amplifier Operational Amplifier Operational Amplifier Positive Voltage Regulator 1 5A Negative Voltage Regulator 1 54 Positive Voltage Regulator 1 54 Positive Voltage Regulator 1 54 Operational Amplifier Voltage Reference LAKE SHORE PART NO CD4029 CD4029 CD4029 CD4029 GD4029 MC1413 CD4093 AD7512 OP15 OP15 MC1458P F741TC LF356N LF356N MC7805 MC7915 MC7815 MC7815 LN308 LM399H AE AE AE AE AE AL BE D1 44 s n ss1 lt X gt XL q t REF LAKE SHORE DESG DESCRIPTION PART NO U21 F E T 3N163 U22 Not present U23 Voltage Refere
50. oint temperature the sensor diode voltage will be high and the null meter will deflect to the right Slowly increase the setting Keys 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 vernier in the position required to reduce the null error to zero but below any level which induces oscillations g After achieving a stable operating point reduce the F S CURRENT AMPS Key No 9 to a lower setting As lower settings are dialed in the percent 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
51. peration 4 1 Introduction This section contains the theory of operation of the DTC 500SP Controller and a functional characterization 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 A 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 a 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 a 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 su
52. plifier is also negative resulting in an output voltage which would integrate towards a large positive value avoid this condition since reset is not required the diode CR6 essentially shorts the output to 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 lAvilVe lt 2 volts then the output voltage of the comparator U11 is 15 volts The integrator is therefore disabled since the diode CR5 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 26 The switch is closed when the AUTO RESET control is in the off position and the amplifier gain is approximately 10 5 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 th
53. rted 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 advantageous for setting up steady state voltages where a fast response to changes in input is not required 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 500SP simple highly linear mark space ratio digital to analog converter R Stockton J of Physics E Scientific Instruments 1977 Vol 10 24 The sensor select switch selects either sensor A 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 resistor 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
54. the 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 collector of Q2 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 27 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 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 R73 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 R200 and its appropriate shunt resistor Under no circumstances shall the rating of fuse FU2 be increased above one ampere in an attempt to achieve a power dissipation of 25 watts in a heater element whose resistance is less than 25 ohms Such a substituti n invalidates the instrument warranty and is likely to damage the output power amplifier circuit 28 Summing of Input Signals 29 J FS e SENSOR J2 F SELECT oe pour cres MIS RR gt R
55. ture 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 Senstive Diode or TG 100 Gallium Arsenide calibrated Standards laboratory calibration service for correlating 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 forty watts or other than forty ohm heater resistance BCD Input Output Optional Include parallel BCD input of set point and a parallel BCD output of sensor voltage SECTION II Installation 2 1 Introduction This section contains information and instructions necessary for the installation and shipping of the Model DTC 500SP 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 instrument was electrically and mechanically inspected prior to shipment It should be free from mechanical damages and in perfect working order upon receipt To 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 m
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