Model DTC-500_1972
Contents
1. 7 PIN REMOTE SET POINT AMPHENOL 126 198 HEATER BINDING POST E F JOHNSON 111 0113 001 HEATER BINDING POST E F JOHNSON 111 0105 001 CHASSIS GROUND POST E F JOHNSON 111 0103 001 36 DESG PL 1 MT 1 MT 2 DL 1 DL2 LAKE SIIORE DESCRIPTION PART NO POWER TRANSFORMER T 25 29 PILOT LIGHT ASSEMBLY INDUSTRIAL DEVICES 1040A87 NULL METER 100 0 100 uAmp CURRENT METER 0 1 MilliAmp 10 TURN DIAL FOR R28 HELIPOT 2607 10 TURN DIAL FOR R54 HELIPOT 2607 37 6222 ese s e I 6 9 Ere le H Bly 2190 GIHD 9 Sd GII Occ el IVA O 2 GII se I oCo Ins uj Pat Elu l or i czu 224 l I le A Sf O eni tO IT O 6028 8024 4024 902u 3 8 9 vs Qu GOCH OZH LOO VWOOO OO G9H 38 42 D 92d d zz 428 227 m OCH a Q 22u e LO i C ees A 149 19 wo 9 _ ssu o9 812 og 7 28 o c sey 2 968 oe HL 8 H d etu ug tu 2589 1 Icy 8289 38 58 3 xu 6685 gg I S289 198 Iru OS crt seu tu O DI Sy gt I YJ 26 Ae oi e sir S L z a 29 zeu p D I 963 19 R62 R24 R33 N ER z E 7 U e GU oy 9835 842 ME fcn EM p Y I gt E P H3 Oly r kg C O al 638 O1u2 glyo j C i lig CDI l2. 126 217 or equivalent in place of the sensor as shown in Fig 3 7 and turn the sensor selector switch on the front panel to Manual A position A E R y Shield B D Figure 3 7 The voltage drop across resistor R is equal to 10 x 1076 x R volts thus a 100K ohm resistance would result in a 1 volt drop With the reformer TEMPERATURE SET POINT switch on the rear of the instrument 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 10 turn dial at the internal set point control if necessary for the null meter to indicate zero Move the reference set point switch on the rear panel to external position and adjust trim resistor R 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 resistance divider may be used for R in the sensor input connector however the leads as well as the divider resistor should be shielded 20 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 shielded through pin H of external set point plug J3 3 9
3. by op amp A4 Q3 and Q4 before being applied to the heater element Transistors Q3 and Q4 constitute a Darlington series pass element in a current amplifier circuit They are inside the feedback loop associated with op amp A4 R65 being the feedback resistor The input resistor for the op amp is R62 so that the voltage gain of the power amplifier circuit is R65 R62 or approximately 3 5 At rated output current of one ampere the voltage appearing at TP20 is 10 5 volts Use of a heater resistance in excess of ten ohms will reduce the available heater current below the rated maximum value of 1 ampere Winding 5 6 7 on transformer T1 diodes CR 22 and CR 23 and capacitor C16 constitutes the power supply for the series pass elements Q3 and 04 Power supplies PS 4 and PS 5 are supplies for operational amplifiers A2 AS and A4 transistor Ql and FET Q2 g Manual Heater Current Control When the mode selector switch is set to either MAN A or MAN B position switch section S1 F connects the input of the power amplifier stage to the wiper 27 of potentiometer R54 Varying the wiper position from zero to its maximum will vary the voltage at TP20 from zero to 10 volts The heater element current is thus varied proportionately to the setting of R54 and the maximum heater current switch 54 position h Heater Current Metering and Limiting The heater element current is measured by the heater current ammeter shunted by resistor R201 through R
4. 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 is externally connected to the chassis ground terminal Although the grounding of the controller common is normal operation practice the common Lo terminal may be disconnected from chassis ground if doing so helps to eliminate accidental ground loops within the system 21 SECTION IV Theory of Operation 4 1 Introduction This section contains the theory of operation of the DTC 500 Controller and a functional characterization of the controller in Laplace transform notation to aid the thermal system designer in system stability analysis 4 2 General Description Refer to Figure 3 3 and Figure 5 2 as an aid in the following discussion With reference to Figure 3 3 a precision constant current source causes 10 micro amperes of current to flow through the sensor diode The set point voltage source or bucking voltage is subtracted from the diode voltage and the difference or error signal is amplified in a variable gain amplifier stage operational ampli fier A2 in Fig 5 1 The amplified error is displayed on the NULL meter and also applied to 1 a gain of 20 amplifier 2 an integrator circuit and 3 a bound or clamping circuit The bounding circuit disables the integrator for large errors The output of the integrator is amplified
5. PS 1 and PS 2 and operational amplifier Al constitute the main components in the diode constant current supply Due to the high input impedance of the operational amplifier Al the diode current is forced to flow through resistor R26 developing 4 99V at 10 uAmps The wiper of potentiometer R23 is positioned so that an equal voltage is developed between the wiper of R23 and the junction of CR 22A and R24 With the wiper so adjusted any variation in the diode current will result in a differential error voltage When amplified and applied to the cathode of the sensor diode this signal will be of such a polarity as to drive the diode current back towards its design value of 10 uAmps 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 Supply and Divider Floating power supply PS 3 preregulates the voltage used to supply reference diode CR 13 The doubly regulated voltage appearing between tie point TP 5 and the cathode of CR 13 is applied to a 3 stage Kelvin Varley voltage divider consisting of R101 R117 R28 R29 R33 and R34 The set point voltage proper consists of the potential developed between tie point 5 and the wiper of potentiometer R28 The floating set point voltage power supply and Kelvin Varley voltage divider constitute a potentiometer loop When the set point voltage equals the sensor diode voltage no error signal
6. appears at the input terminals of preamplifier A2 25 d Variable Gain Amplifier The variable gain amplifier shown in Fig 3 3 with a gain range of 7 5 to 750 is realized by chopper stabilized operational amplifier A2 The input resistor is R32 and the feedback element consists of R35 and R41 and potentiometer R37 and R38 and resistors R39 R40 and R41 Diodes CR 26 27 28 29 or R39 and R40 comprise a soft limiter circuitry Large signals cause forward biased diodes to conduct which in turn reduces the effective feedback resistance and amplifier gain and prevents the amplifier from saturating The output of amplifier A2 drives the null meter and subsequent stage A3 For small errors the meter reading is proportional to the error As the error amplitude increases either diode CR 35 or CR 36 conducts causing the meter reading to be logarithmic Cross over from linear to non linear deflection occurs at approximately 60 of full scale 26 e Automatic Reset Circuit Bounding Circuit The bound circuit integrator variable gain amplifier Av of 1 to 100 and the constant gain of 20 amplifier shown in Fig 3 3 are realized by operational amplifier A3 bipolar transistor Ql and field effect transistor Q2 in Fig 5 1 A simplified equivalent circuit of the stage is given in Fig 4 2 Application of the principle that the summing junction currents must add to zero yields the overall transfer function of the stage The constant ga
7. by a variable gain amplifier whose gain is set by the AUTO RESET potentiometer The gain range is from 1 to 100 The in tegrator bounding circuit post integrator variable gain amplifier and constant gain of 20 amplifier are associated with operational amplifier A3 transistor Ql and field effect transistor Q2 in Figure 5 1 The processed error signal drives the output power amplifier circuit whose voltage gain is 2 Operational amplifier A4 and transistors Q3 and Q4 in Fig 5 1 comprise the power amplifier The output of the power amplifier is metered by the HEATER CURRENT indicator and passed to the heater element Closed looped control action is achieved by providing a thermal Signal path between the heater element and the temperature sensing diode To illustrate the automatic temperature control action suppose the sensing diode is colder than the programmed temperature setting The diode voltage will be greater than the set point voltage which results in an error voltage The greatly amplified error signal causes a current to flow in the heating element which raises the diode temperature and reduces its voltage As the diode temperature approaches the set point temperature the error signal is reduced and less power is supplied to the heater element At some small temperature error or offset the power supplied to the heater element is just sufficient to heat the sample holder and diode to maintain a steady but slightly lower temperature The AUTO
8. 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 27 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 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 measurement from the top side of the printed circuit board Therefore the board need only be removed when it is necessary to replace a component To remove the printed circuit board unscrew the bolts from the bottom of the case which attach the board to the stand off studs Swing the rear of the board up using the front edge as a pivot Be sure to clear the line cord retainer and fuse holders Be sure to support the board in the raised position If the board is stressed it may break or develop hairline cracks in the printed wiring Use a low heat 25 to 50 watts small tip freshly tin
9. through PS 5 in Figure 5 1 Each supply uses an integrated uA723 type Precision Voltage Regulator as its main component A detailed drawing of one of the supplies is given in Fig 4 1 A description of this supply should suffice for all the others The secondary voltage of transformer Tl appearing at terminals 14 and 15 is rectified by diode rectifier bridge CR1 4 and filtered by capacitor Cl This unregulated voltage is applied to the uA723 power supply leads 12 and 7 The reference voltage op amp in the uA723 produces a stable 7 1 volt reference voltage at pin 6 This voltage is externally coupled to the non inverting input to the regulator op amp pin 5 by resistor Rj The value of R is chosen to be equal to the parallel combination of Rz and R4 to minimize offset errors Resistors Rz and R4 sample a fraction of the output voltage and apply it to the inverting input pin 4 The regulator op amp attempts to maintain the potential at pins 4 and 5 equal to one another in spite of variations in the line voltage and load current The output current is passed through Ro Automatic current limiting is accomplished by current sampling resistor R and the current shut down transistor connected to pins 2 and 3 If the current through R5 is excessive the resulting voltage developed across R causes the transistor to conduct diverting base current from the series pass transistor b Diode Constant Current Supply Referring to Fig 5 1 power supplies
10. 1 Introduction This section contains information and instructions necessary for the installation and shipping of the Model DTC 500 Cryogenic Temperature Controller Included are initial inspection instructions power and ground ing 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 mars and scratches and in perfect working order upon receipt To confirm this the instrument should be inspected visually for obvious damage upon receipt and tested electrically by use to detect any concealed damage Be sure to inventory all components supplied before discarding any shipping materials If there is damage to the instru ment 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 il 2 3 Power Requirements Before connecting the power cable to the line ascertain that the line voltage selector switch 115V or 230V is in the appropriate position for the line voltage to be used Examine the power line fuse Key No 13 Page 11 to insure that it is appropriate for the line voltage 115V Amp 230V 0 4 Amp Nominal permissible line voltage fluctuation is 10 at 50 to 60 Hz Caution Disco
11. 205 as appropriate for the current range selected The full scale output current is determined by the series combina tion of the heater element resistance and one of the group of resistors R206 through R209 This series combination is connected across the nominal 10 5 volt output of the power amplifier Approximately 5 volts appears across the IMA murrent meter and R66 Under no circumstances shall the rating of fuse FU2 be increased above one ampere in an attempt to achieve a power dissipation of ten watts in a heater element whose resistance is less than ten ohms Such a substitution invalidates the instrument warranty and is likely to damage the output power amplifier circuit 28 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 Voltohmist vacuum tube voltmeter or an equivalent high input impedance digital voltmeter a ten ohm ten 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 500 Controller 5 3 General Remarks Upon initial installation the single most probable cause of system mal function is an i
12. C22 01 MFD 50 VDC Mylar CR1 12 SILICON RECTIFIER IN4002 CR13 REFERENCE DIODE IN4571A CR14 21 SILICON RECTIFIER IN4002 CR22 SILICON RECTIFIER IN1612 CR23 SILICON RECTIFIER IN1612 CR24 SILICON PROTECTION DIODE 411 CR25 SILICON PROTECTION DIODE 411 CR26 SILICON DIODE 411 CR27 SILICON DIODE 411 CR28 10 V REFERENCE DIODE IN961 CR29 10 V REFERENCE DIODE IN961 CR30 SILICON DIODE 411 CR31 5 9 V DZ 7011 CR32 SILICON DIODE 411 CR33 SILICON DIODE IN841 CR34 SILICON DIODE 411 CR35 IN358 CR36 IN358 CR37 REFERENCE DIODE IN4571A Al OPERATIONAL AMPLIFIER 5825 A2 OPERATIONAL AMPLIFIER 5823 A3 OPERATIONAL AMPLIFIER 9825 A4 OPERATIONAL AMPLIFIER 5824 35 REF DESG Ml M2 M3 M4 M5 FUI FU2 HS 1 HS2 HS3 LAKE SHORE DESCRIPTION PART NO VOLT REG 6W7723393 VOLT REG 6W7723393 VOLT REG 6W7723393 VOLT REG 6W7723393 VOLT REG 6W7728393 2N3638 2N5459 FET TRANSISTOR 2N4234 2N4901 MODE SELECTOR SWITCH SET POINT SWITCH ASSEMBLY PART OF POTENTIOMETER R55 HEATER CURRENT METERING SW ASSEMBLY POWER SW A H amp H 81024 GB LINE VOLTAGE SELECTOR SWITCH SWITCHCRAFT 46256LF TEMP SET POINT SELECTOR SWITCH SWITCHCRAFT 46206L FUSE HOLDER LITTLEFUSE 342004 FUSE HOLDER LITTLEFUSE 342004 HEATSINK WAKEFIELD ENG MODEL 690 3 BA HEATSINK CR6 WAKEFIELD ENG MODEL 695 B HEATSINK CR7 WAKEFIELD ENG MODEL 695 B 5 PIN SENSOR SOCKET AMPHENOL 126 218 5 PIN SENSOR SOCKET AMPHENOL 126 218
13. D I Pin H Equivalent Set Point Network Figure 3 5 18 A number of external temperature programming networks are shown in Figure 3 6 E E E E T D SNL SM R R R 1 I 1 1 RE aP I R t O B o Se Ry R2 iv So R3 3 R R lt Ta 3 3 D D D D TRIM A B C D Figure 3 6 The following is a suggested procedure for designing external temperature set point control circuitry 1 Determine the range of desired temperature control voltage 2 Choose the most suitable control circuit for your application a Temperature control range 19 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 S 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 it is suggested that the divider calculation be based on approximately 20 ohms per 0 1 volts and a shunting resistor R in Fig 3 6 a used for precision trimming The 3 0 volts between pins E D can be measured with a precision floating voltmeter or calibrated with the DTC 500 internal set point volts switch and 10 turn dial as follows a Connect a precision resistor R any value between 50K 250K to the pins A B of the sensor A input plug J amphenal type
14. M ia rur BS Iu Pet s HE a pii riis I TER 3 Noe e LhZA ahah uto nc A i Detsen die cnet 5 Prasana e Abus Z c 12 Table 3 1 cont NO KEY NAME FUNCTION 20 i NO LABEL Remote set point voltage divider cable receptacle Amphenol 126 195 plug 21 HEATER Heater element lead terminals Grey is the high side and Black is the low side 22 GROUND Chassis ground terminal 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 500 as a cryogenic thermometer to measure the temperature of a calibrated diode connected to SENSOR A terminals initially position switches and controls as follows 1 Temperature set point switch Key No 19 to INTERNAL 2 Mode switch Key No 6 to MAN A 3 MAN RESET Key No 7 to zero 4 MAX HEATER AMP Key No 8 to 0 01 5 GAIN Key No 4 to minimum setting 6 AUTO RESET Key No 5 to off 7 POWER switch Key No 9 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 left the set point voltage is less than the sensor voltage If the deflection is to the right the set point voltage is greater than the sensor voltage Adjust the set point voltage until the NULL meter is centered while increas
15. MATIC RESET feature of the controller is used to reduce this error to zero The automatic reset circuit integrates the error and this accumulated signal drives the output power amplifier The integrator signal continues to grow as long as an error exists The heater current continues to increase in response to the integrator signal Eventually the error is driven to zero and the integrator signal assumes a constant value This signal is precisely the value of heater current required to maintain the error at zero The integrator capacitor stores or remembers this signal as the appropriate heater current level to maintain temperature coincidence between the diode and the set point temperature In control theory terminology the AUTO RESET circuit raises the system type number from zero to one Feedback Control System Analysis and Synthesis by John J D Azzo and Constantine H Houpis McGraw Hill Book Co New York 1966 Pg 397 22 regulated output R3 68k 62k Ry ddAL cLV Q IIHONIVd AHL dO LINDYID A Iddf S UAMOd VNOILVHHUdO Tv AUNDTA peejnbDoe Jun esues Ju Juno p pejej iBeuun L S d 23 Eo Rs R57 zp Ej R45 SR5C9 Re FIGURE 4 2 SIMPLIFIED EQUIVALENT CIRCUIT OF AUTOMATIC RESET AMPLIFIER 24 4 5 Detailed Description a Regulated Power Supplies There are five essentially identical regulated power supplies in the instrument They are designated as PS 1
16. User s Manual Model DTC 500 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 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 Obsolete Manu
17. W 8 65K 1 8W 18K 1 4W 100K 1 4W 1 5K 1 4W 12K 1 4W 33K 1 4W 680K 1 4W 2 7 MEG 1 4W IK TEN TURN POT 3 83K 1 8W 2 7K 1 4W 1 MEG 1 4W 1 2K 1 4W 1 MEG POT 1K 1 4W 10K 1 4W 16 2K 1 4W SOK 1 8W 12K 1 4W 56K 1 4W 17 61 1 8W TRIMMING RESISTORS 48 7 1 8W 430 1 8W 54 9 1 4W 16 9 1 8W 5 0 1 8W 1 65 1 2W 4 995 iW 1000 1 4W 324 1 2W 90 2W 23530 5W BF SP S gO SS BD DO SO JO BO GT UT UT UT LUT UT Qn SO g Ge 1 oO dH SO SO Ge GT UT Mm iw OS o9 SO SO GE gd S Go g9 go pep oe dE E E ps LAKE SHORE PART NO NOMINAL MANUAL RESET AUTO RESET CONTROL NOMINAL SET POINT VOLTAGE DIVIDER ASSEMBLY HEATER CURRENT RANGE AND METER SWITCH ASSEMBLY 34 REF LAKE SHORE DESG DESCRIPTION PART NO Cl 220 MFD 63 VDC Electrolytic G2 91 pF Mica DM10 C3 OPTIONAL 25 MFD 25 VDC Electrolytic C4 220 MFD 63 VDC Electrolytic CS 91 pF Mica DM10 C6 OPTIONAL 25 MFD 25 VDC Electrolytic C7 220 MFD 63 VDC Electrolytic C8 91 pF Mica DM10 C9 OPTIONAL 25 MFD 25 VDC Electrolytic C10 220 MFD 63 VDC Electrolytic C11 91 pF Mica DM10 C12 OPTIONAL 25 MFD 25 VDC Electrolytic C13 220 MFD 63 VDC Electrolytic C14 91 pF Mica DM10 C15 OPTIONAL 25 MFD 25 VDC Electrolytic C16 2500 MFD 25 VDC Electrolytic C17 22 MFD 100 VDC Mylar C18 68 MFD 50 VDC Mylar C19 22 MFD 50 VDC Mylar C20 100 MFD 15 VDC Tantalum C21 470 pF 100 VDC Mica
18. al 1972 II IV VI n 1 2 3 4 9 I 2 2 2 2 2 2 ON C1 GW t2 3 3 3 du 3 3 3 3 3 O J ON 2 W ND Table of Contents eneral Information Introduction Description General Specifications Major Assemblies Supplied Accessory Equipment and Custom Options nstallation Introduction Initial Inspection Power Requirements Grounding Requirements Installation Repackaging for Shipment 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 Remote Temperature Programming Grounding Theory of Operation 4 1 Introduction 4 2 Detailed Description a Regulated Power Supplied b Diode Constant Current Supply c Set Point Voltage Supply and Divider d Variable Gain Amplifier e Automatic Reset Circuit Bounding Circuit f Output Power Amplifier g Manual Heater Current Control h Heater Current Metering and Limiting Maintenance and Trouble Shooting U1 C1 Vi ui G GU 01 UT WV GOOL WW ND Introduction Test Equipment and Accessories General Remarks Servicing Printed Circuit Boards Operational Checks Normal Operating Voltages and Gains Calibration of Set Point Voltage Calibration of Sensor Current Parts List Printed Circuit Board Component Locator and Schematic Appendixes Pa
19. e 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 vernier is varied in the vicinity of the null 30 While still in the MAN A position set the MAXIMUM HEATER AMP switch at 1 amp Vary the MAN RESET potentiometer from zero towards 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 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 MAX HEATER CUR switch to 1 am Position the mode control switch to AUTO A Abruptly rotate the set point voltage vernier counter clockwise sufficiently to cause a 10 unit deflection of the NULL meter 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 towards full scale deflection The rate at which the heater current rises is determined by the AUTO RESET time constant setting The rate 1s a minimum in the counterclockwise position and a
20. e output power amplifier is capable of supplying up to 10 Watts of heater power In view of the high cost of some cryogenic fluids such as heliun cost consciousness suggests that cryostat design and operating strategies be planned to limit heater power requirements to substantially less than ten watts Power boosters are available from the company as accessory equipment if required for special applications The principal intended application of the DTC 500 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 raw outputs range between 0 and 3 0 volts and whose incremental sensitivities are in the range of tenths of millivolts In addition to its use as a closed loop automatic temperature controller the Model DTC 500 Controller may be used as a precision thermometer By adjusting the set point voltage so that the error signal 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 500 Controller are applicable when used with the TG 100 or DT 500 full range temperature sensitive diode General Controller Range Heater Output Sensor Sensor Input Sensor Current Input Line Voltage Power Consumption Circuit D
21. esign Weight Dimensions Gain Temperature Control Set Points Repeatability Automatic Reset 1 K to 400 K nominal 1075 to 10 watts 0 1 Amp 0 10 Volts Models TG 100 or DT 500 temperature sensitive diodes single ended or floating model four terminal connection constant current potentiometric 10 microamperes 115V or 220V 50 60 Hz 30VA Solid State 15 pounds 54 high 19 wide 1135 deep rack mount ing 3 Amps millivolt into 10 ohm resistor at maximum setting 0 to 3 0 volts Switch 1 volt per step 100 mV per step and 10 turn interpolating potentiometer with 0 1 mV graduations 0 1 linearity 10 microvolts 0 019K or better 3 to 100 second variable time constant or off Manual Output Control Range 10 turn potentiometer control 0 to full range current Heater Current Ranges 10 mA 30mA 100mA 300mA 1A Heater Resistance for Max Power 10 Ohms Controller Proportional Gain 3 Amps mV in automatic mode nominal Temperature Readout 2 Sensor connections front panel selectable between control sensor and temperature sensing only sensor Accuracy equivalent to 100 microvolts 0 1 K worse case calibration error of sensor Excitation Current 10 microamperes Excitation Current Regulation 0 05 Sensor Calibration Chart must be supplied by manufacturer of sensor in use 1 4 Major Assemblies Supplied The Model DTC 500 Cryogenic Temperature Controller includes a
22. ge NWN ti JS UI C LUT UT YOLVDIGNI AWUALVYJJWAL DINADORUD 005 511 I300W NDIA AN SSS ES SECTION I General Information 1 1 Introduction This section contains a description of the Model DTC 500 Cryogenic Temperature Controller its applications general specifications major assemblies supplied and accessory equipment available 1 2 Description and Applications The Model DTC 500 Cryogenic Temperature Controller is housed in an aluminum case with standard 19 relay panel front for rack mounting 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 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 orovided excite the temperature transducer The error processing section of the controller is of the proportional plus integral 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 Th
23. in of 20 amplifier in Fig 3 3 is represented by the term R57 R45 while the variable gain amplifier following the ideal integrator is represented by the term 1 R57 Re R45C20 in the equation in Fig 4 2 The bounding circuit disables the integrating function for large errors when vapid corrective action is desired The memory action of integrating capa citor C20 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 C20 If the voltage across capacitor C17 is of such a polarity as to make TP19 positive with respect to TP17 diode CR 33 conducts reducing the effective gain of the stage and discharging the capacitor The second mode of bounding occurs if the error signal at the base of Ql becomes excesSively negative Ql is normally biased by CR 30 so that field effect transistor Q2 is cut off approximately 9V at the gate As the base of Q1 be comes more negative Ql conducts current increasing the collector voltage toward zero The reduced bias on FET Q2 causes its source drain impedance to act as a shunt resistor across capacitor C20 This shunting effect discharges the capacitor and converts the ideal integrator action to a type zero action The switch S3 is open when the AUTO RESET control is in the off position f Output Power Amplifier The processed error signal appearing at TP18 is greatly amplified in power
24. ing the GAIN towards maximum Increaging the voltage will move the meter pointer to the right decreasing the set point voltage will deflect the meter pointer to the left After centering the meter read the set point voltage by adding the vernier potentiometer reading approximately scaled to the SET POINT switch setting value The ten turn dial s 500 divisions correspond to 100 milli volts so that each dial division corresponds to 0 2 millivolts readable to 0 1 millivolt 13 UATTOWLNOD AUNLVUHdWAL 00S DLA WVUDVIG AJ018 TANDIJ U3ed 8 TEWIOUL Jo39gnuo31y 18384 pue 1930 PW TIAN AN 3ueuin 1 189 lt lt Iosu s 1 po 001 91 lt L 23 dnv lt EW 11 1 af 349 9 2 S8BITO 19 ESH 1 Q JULINA 3u 1suo 14 programmed set point temp sample holder temp new set pt temp A initial I set pt instantaneous temp error temp time time of abrupt change in set pt temp programmed set point temp initial set p p sample holder temp temp instantaneous temp error set pt temp time time of abrupt reduction in set pt temp FIGURE 3 4 TEMPERATURE VERSUS TIME CHARACTERISTICS OF CONTROLLER After determining the set point voltage refer to the diode calibration chart to ascertain the diode temperature 3 5 Constant Tem
25. max imum in the fully clockwise position Abruptly rotate the set point voltage vernier clockwise to cause 10 units deflection of the NULL meter The HEATER CURRENT meter should grad ually 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 asymetry in the temperature versus time characteristics as shown in Fig 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 6 5 6 Nominal Voltages and Gains The following voltage measurements were made with an RCA Senior Voltohmist meter A 1 75K resistor was used to simulate the diode and a 10 ohm 10 watt resistor was used in place of a heater element The voltage across the input filter capacitors Cl C4 C7 C10 and C13 in power supplies PS 1 through PS 5 nominally 24 volts with nominal line voltage The output voltage which appears between terminals 3 and 7 of the uA723 integrated circuits is 15 volts The sampling resistors are proportional so that the potential between pin 4 and pin 7 is approximately 7 volts Reference diodes CR 37 and CR 13 are reverse biased at 6 4 volts The voltage appearing across capaci
26. mproperly connected temperature sensing diode If it is impossible 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 A receptacle and that the TEMPERATURE SET POINT INTERNAL REMOTE Slide switch at the rear of the case 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 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 1 Open or shorted sensor and heater leads particularly in the vicinity of the sample holder if it is subject to frequent dis assembly 2 Leakage paths between heater and sensor leads giving rise to electrical feedback in addition to thermal feedback 3 Premature loss of cryogenic fluid due t 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 temperatur etc 4 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 5 Examine heater element fuse FU2 If it is indicated that
27. n 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 5 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 level which induces oscillations 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 units The NULL meter should deflect to the left 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 state ment presupposes that the
28. ned 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 in serting 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 ten watt ten 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 at maximum position and the mode selector switch in position MAN A assuming the test plug is in SENSOR A receptacl
29. nnect line cord before inspecting or changing line fuse 2 4 Grounding Requirements To protect operating personnel the National Electrical Manufacturers Assocation 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 Do not ground shield voltage sense current supply W D 777 JS BLACK B RECOMMENDED HEATER CABLE Do not ground shield Coo 7 7 7 ae C ALTERNATE SENSOR CABLE FIGURE 2 1 SENSOR AND HEATER CABLES 2 5 Installation The DTC 500 Controller is all solid state and does not generate Significant heat 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 500 Controller to an ambient temper ature in excess of 500C 1220F 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 The indicated shielding connections are the recommended standard practice to avoid ground loops If thermal con
30. o volts If recalibration is indicated the voltage drop across the precision resistors can be measured after removing the case cover and adjusting trimmer R2 on the circuit board a2 5 9 Parts List Component Location Diagram and Schematic Table 5 1 PARTS LIST REF LAKE SHORE DESG DESCRIPTION PART NO R1 3 6K 1 4W 10 R2 6 2 ohms 1 4W R3 8 2K 1 8W NOMINAL R4 7 5K 1 8W 1 R5 3 6K 1 4W 10 R6 6 2 ohms 1 4W R7 8 2K 1 8W 1 NOMINAL R8 7 5K 1 8W R9 3 6K 1 4W 10 R10 6 2 ohms 1 4W 5 R11 8 2K 1 8W NOMINAL R12 7 5K 1 8W R13 1 24K 1 8W 1 R14 3 6K 1 4W 10 R15 6 2 ohms 1 4W R16 8 2K 1 8W NOMINAL R17 7 5K 1 8W 1 R18 3 6K 1 4W 10 R19 6 2 ohms 1 4W R20 8 2K 1 8W 1 NOMINAL R21 7 5K 1 8W R22 7 5K 1 8W R23 5K TRIMPOT HELIPOT 58PR5000 R24 30 9K 1 8W R25 50K 1 8W NOMINAL R26 499K 1 8W 1 R27 100K 1 4W 5 R28 100 ohms 10 TURN POT HELIPOT 7216 R29 TRIM RESISTOR NOMINAL R30 3 48K 1 8W 15 R31 470 1 8W 1 R32 100K 1 4W 5 R33 10 TRIMPOT HELIPOT 78PR10 R34 579 1 4W 1 R34A NOMINAL R35 22 MEG 1 4W 5 R36 560 1 4W 5 R37 10K POTENTIOMETER GAIN CONTROL R38 100 1 8W 1 R39 100 1 4W 5 R40 10K 1 4W 5 R41 20K 1 4W 5 R42 NOMINAL DESG R43 R44 R45 R46 R47 R48 R49 R50 R51 R52 R53 R54 R55 R56 R57 R58 R59 R60 R61 R62 R63 R64 R65 R101 104 R105 106 R107 117 R200 R201 R202 R203 R204 R205 R206 R207 R208 R209 DESCRIPTION 470 1 4W 330K 1 4
31. perature Control Mode Assume that a 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 switch and vernier Position controls as indicated below 1 Temperature set point switch Key No 19 to INTERNAL 2 Mode switch Key No 6 to AUTO A 3 MAN RESET Key No 7 to zero 4 MAX HEATER AMP Key No 8 to 1 0 AMP 5 GAIN Key No 4 to minimum setting 6 AUTO RESET Key No 5 to off 7 SET POINT VOLTS switch and potentiometer to voltage corresponding to desired temperature 8 POWER switch Key No 9 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 left Slowly increase the GAIN setting Key No 4 in a clockwise direction 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 left 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 i
32. 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 water proof paper or 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 SECTION III Operating Instructions 3 1 Introduction This section contains a description of the operating controls their adjustment under normal operating conditions typical controller appli cations 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 a to the Sensor A receptacle and a 10 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 Figures 3 1 and 3 2 The numbers with leaders to various controls in the figures are keyed to the ent
33. ries in Table 3 1 Table 5 1 NO KEY NAME FUNCTION l SET POINT VOLTS Ten turn vernier interpolator 0 0 1 potentiometer to continously adjust set point voltage between switch setting and next higher setting 2 SET POINT VOLTS Kelvin Varley divider selects most 0 l and 2 VOLTS significant digits of setpoint voltage 3 SET POINT VOLTS selector switch of Kelvin Varley 0 to 9 VOLTS divider 0 1 volt per step 4 GAIN 1 100 Adjusts overall controller gain between 330 and 33 000 Figure 3 3 5 AUTO RESET Adjusts gain of amplifier following OFF MIN MAX integrator See Fig 3 3 Effect ively determines time constant of integrator between 3 and 100 seconds 6 AUTO A MAN A Mode selector switch AUTO A uses MAN B 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 NO KEY 10 11 12 13 14 15 16 17 18 19 Table 3 1 cont NAME MAN RESET MAX HEATER AMP POWER NO LABEL HEATER CURRENT NULL 115 230V 50 60 Hz NO LABEL 1 0A S B SENSOR A SENSOR P TEMP SET POINT INTERNAL REMOTE FUNCTION When mode selector switch 5 is in either MAN A or MAN B position the MAN RESET ten turn potentiometer per mits the user to manually adjust the current to the heater element Caution High settings will quickly boil away cryogenic fluids S
34. s standard equipment in addition to the controller proper the following additional components 1 1 Operating and Service Manual 2 2 Five pin plugs for temperature sensor cables 3 1 Seven pin plug for remote set point cable Temperature sensitive diodes are not supplied as part of the DTC 500 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 1 Extra 5 and 7 pin connectors 2 3 4 5 6 7 Multisensor selector panel Special low thermal offset switch and cabling for selecting among multiple sensors Remote set point voltage control and programming module Custom modification of sensor current supply value TG 100 Gallium Arsenide or DT 500 Temperature Sensitive Diode Uncalibrated See data sheets at end of this manual for nominal operating characteristics and case styles available TG 100 Gallium Arsenide or DT 500 Temperature Sensitive Diode Calibrated Standards laboratory calibration service for correlating diode output voltage with diode temperature See sensors data sheet for additional information Power Boosters for heater power requirements in excess of ten watts or other than ten ohm heater resistances SECTION II Installation 2
35. sample holder may be accurately modeled as a simple R C type time constant circuit If oscillation or overshoot are observed when changing the set point voltage in small increments reduce the GAIN and AUTO RESET settings until oscillations are no longer observed 3 6 Manual Heating Mode By placing the mode selector switch Key No 6 in either position MAN A or MAN B a 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 7 and the MAX HEATER AMP switch Key No 8 The current supplied to the heater is indicated on the HEATER CURRENT meter The full scale reading of the meter corresponds to the MAX HEATER AMP switch setting 3 7 Temperature Readout Mode Sensor B In some applications the temperature is controlled or regulated at one physical location while it is desired to measure the temperature at a second location This requires two sensors Sensor A located at the temper ature control point and Sensor B at the second point where only the temperature is to be measured Sensor B must be calibrated Assume that the temperature at Sensor A has been stabilized by operating the controller in the constant temperature control mode as described in Section 3 5 By observing the steady HEATER CURRENT reading one may switch to the MAN A mode as described in Section 3 6 and establish this same current by adjusting the MAN RESET po
36. siderations dictate the alter nate wiring scheme shown in Fig 2 1 c may be used for the diode 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 15 Pg 11 for proper value 3 AG 1 0A Slow Blow or smaller current rating if desired This fuse protects 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 malfunction with a factory representative He may be able to suggest several 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 instrument itself not on the shipping carton clearly stating 1 Owner and address 2 Instrument Model and Serial Number 3 Malfunction symptoms 4 Description of external connections and cryostats If the original carton is available
37. strument has been carefully calibrated to within 100 mV and residual base line resistance of the 10 turn potentiometer R28 Should it be desirable to check or recalibrate the set point reference voltage the sensor should be disconnected and the TEMPERATURE SET POINT switch on the back panel be in the INTERNAL position The reference voltage may be measured across pins E D of the sensor connectors Jj or Jz without opening the core Voltage measurements should be taken with a high precision potentiometric instrument If recalibration is indicated after allowing a minimum of 20 minutes warm up time remove the cover and adjust trimmer R33 so the voltage between terminal pins 5 and 3 should be within 3 0000 100 uv 5 8 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 21 or J and the sensor selector switch on the front panel switched to the appropriate sensor input A or B The TEMPERATURE SET POINT switch on the rear panel should be switched to REMOTE 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 a 100K 01 resistor should read 1 0000 within 100 micr
38. t D 689 liy 614 2 ro 9 o U 58 Siu 6142 ICH RR PI Ozu 0E s li AZ SACRA pce 9I ow Bri N lt A i 6 PS2 PSI PS3 PS5 PS4 w I5 3 to DTC 500 7329 30
39. tentiometer By alternating between the AUTO A 17 and Man A modes the MAN RESET potentiometer may be trimmed sufficiently accurately to hold the temperature steady in the MAN A position Then switch to the MAN B position and quickly adjust the SET POINT VOLT switch and potentiometer to zero the NULL meter This reading is used to determine the temperature of Sensor B After taking the Sensor B voltage reading reset the SET POINT VOLT switch and potentiometer to the desired temperature control point and then return to AUTO A control mode If there is appreciable null error upon returning to the AUTO A mode of control the adjustment of the MAN RESET control should be refined and the measurement of the Sensor B voltage repeated Since the system is operating open loop or is coasting in both the MAN A and MAN B mode of control positions no adjustments or changes should be made in the cryostat system which would introduce transients during this period of time 3 8 Remote Temperature Programming Remote temperature control can be achieved by replacing the internal Kelvin Varley voltage divider with an external resistive divider connected to Jz and switching the TEMPERATURE SET POINT to the REMOTE position To insure maximum accuracy the total resistance between pins E D of J should be equal to 515 ohms The remote set point connection diagram is shown in Figure 3 5 PL Pin E 515 3 Volts ohm a cal GG Pin B Pin
40. tor C16 in PS 6 varies between approximately 14 and 20 volts depending upon the heater element current At no load the voltage is 20 volts decreasing to 14 volts at 1 ampere output 31 The emitter of is biased to 0 5V to compensate for the turn on voltage of Ql The output power amplifier stage may be checked by placing the mode selector switch in the MAN A position The potential across R54 terminals 6 to 7 is 3 4 volts The voltage at terminal 20 should be approximately 3 5 times the voltage selected between the slider of R51 and ground The voltage at the output of amplifier A4 is about one volt more negative than the voltage at terminal 20 because of the base emitter drops of Q3 and Q4 With the AUTO RESET control in the off position in the switch detent and the MAX IIEATER CUR switch in the 1 amp position the total voltage gain of amplifiers A3 and A4 may be inferred The CURRENT METER corresponds to a 10 volt full scale voltmeter if a 10 ohm heater element is used Comparison of the incremental output voltage change to the corresponding incremental NULL meter error change will yield the gain The nominal cascade gain of the last two stages is 40 Gain checks should be performed by first zeroing the NULL meter with the SET POINT VOLTAGE VERNIER A small voltage change is made in the vernier dial setting and the resulting changes in the NULL meter and CURRENT meters observed 5 7 Calibration of Set Point Voltage The in
41. witch selected current limiter Use of a low setting will avoid inadvertent boil off in setting up system A C line switch ON OFF A C line pilot light Meters heater element current Full scale deflection corresponds to MAX HEATER Switch setting Indicates the difference between the set point voltage and the sensor output voltage Meter is non linear for large errors of either sign A C line voltage selector slide switch A C line fuse FU1 See para 2 5 A C line cord Heater element line fuse 1 AMP Slow Blow Sensor A cable receptanle Five pin Amphenol type 126 217 Plug Sensor B cable receptacle Five pin Amphenol type 126 217 Plug Selects between internal set point voltage divider and external divider for comparison with sensor voltage Front panel set point controls in operative when switch is in the REMOTE position Be sure this control is set on INTERNAL since its location on the rear panel may cause one to overlook its setting when initially checking out the instrument 10 b xum OT IT TANVd LNOUd Hdn51I4 D Aer d 2 v LE ERA SE ah LG 42927 Z CY AN E Li WA DAR a ci I Tz A 27 517 o Z 7217226227 Z w 7 d A 4 gt 11 TANVd V l dunoid 0 RO DUE UE ATP RY HEY DOW DM AIV
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