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Model DRC-84C - Lake Shore Cryotronics, Inc.

1. Is Temperature 30 0 2 Round to nearest 50 mK Set up output info and decimal point drive for format of XXX X Output Temp to display Is rhere an option present Set up output info and decimal point drive for format of XXX XX Is there an option set point present Input set point from the front panel Input set point from option Input sensor type control sensor and switch info Input position of C C K Switch Is switch in position Yes Add 273 15 to set po nt read to get Kelvin set point Is switch ir position Is tvpe Platinum s set point Is set point 2399 92 j lt 20 0 Load HI inco temperarure storage area Load LO 2 into remperature storage area ls set point gt 799 97 Load HI 2 into cemperature storage area Determine voltage temperature table to be used Find Break Point Calculate stope for that dT breakpoint Convert BCD to Hex FIGURE 4 2 DRC 84C Software Flow Diagram 0482 43 44 where is set point voltage in volts Tap is break point temperature is set point temperature dV is slope between successive break points dT Vap is break point voltage At this point the program converts the BCD voltage to hexadecimal base 16 and outputs it to the D A converter in complementar
2. U15 Operational Amplifier Current A U16 Sensor A Current Driver U17 Operational Amplifier U18 Operational Amplifier U19 Operational Amplifier Output Buffer U20 Microprocessor Unit with piggy back PROM U21 Decoder Multiplexer U22 Decoder Multiplexer U23 Hex Inverters U24 Hex Inverters U25 Tri State Quad 2 data Selectors Multiplexers U26 Tri State Quad 2 data Selectors Multiplexers U27 Tri State Quad 2 data Selectors Multiplexers U28 Tri State Quad 2 data Selectors Multiplexers U29 Tri State Quad 2 data Selectors Multiplexers U30 Decoder Multiplexer U31 A D Converter Building Block U32 A D Converter Building Block U33 Timer Circuit U34 Quad Latch U35 Quad Latch U36 Quad Latch U37 Quad Latch U38 16 Bit D A Converter U39 Operational Amplifier Input Buffer U4O Operational Amplifier Summing Amplifier U41 Operational Amplifier U42 Operational Amplifier 043 Operational Amplifier Integrating Amplifier 044 Operational Amplifier Output Driver U45 8 Ampere Darlington Power Transistor PART NO LM308N 3N163 AD522 AD522 OPO7EJ 38P70 Plus PROM 2716 or 2532 7415139 7415139 7404 7404 7415257 7415257 7415257 7415257 7415257 7415139 7103A 8052A NE555N 4042 4042 4042 4042 HP16 BGC ICL 7650 ICL 7650 ICL 7650 ICL 7650 ICL 7650 MC1436CU 2N6044 59 60 MISCELLANEOUS CIRCUIT DESIG or FIG NO DESCRIPTION F1 Main Fus
3. a 4 bit parallel input of gain setting a bit parallel input of reset setting and a 4 bit output of switch position from the SW 10A Table 3 6 can be used for input and output line coding The BCD in and out is handled through connector J4 denoted on back panel as INTERFACE a 50 pin connector on the rear panel of the instrument Two internal jumper wires are placed on the printed circuit board in front of internal connector JE Cutting these jumpers allows the user to enable the remote set point by setting Pin 38 J4 high see Table 3 6 If the option was installed prior to shipment these jumpers have already been cut Options that are field installed need to have their jumpers cut by the user Data latches internal to the instrument provide a 1 2 4 8 code using positive logic with standard TTL levels of 0 4 volts or less for low logic O and 2 4 volts or higher for the high or 1 state under full load con ditions The drivers are sufficient to drive two standard loads 3 2mA in the low state Set point is input to the instrument via a remote set point enable pin externally generated pin 38 With no connection made to the external enable pin the option selects the internal front panel set point When the unit is receiving a set point externally the front panel set point switches are disabled The sensor temperature output is externally gated through the use of an internally generated data valid pulse Input of gain value
4. b and c are correct replace U31 This is the clock signal This is generated by an external RC net work with the help of the main processor If not present check R23 C18 and U20 for proper operation Wave Form 0482 0482 Signals from this point on are of a D C nature A general explanation of the D C levels is given in the following Table 5 4 Table 5 4 Signal 1 Input buffer U39 2 Summing amplifier U40 3 Integrating amplifier U43 4 Output power amplifier U44 Function This op amp circuit is used to buffer the incoming control sensor voltage so that there will be no current load on the sensor Resistor R33 varies the output If the voltage at pin 6 cannot be varied until it equals pin 3 U44 may be bad This unit uses current summing to obtain an error Signal With the voltages TP 1 and TP 5 equal and opposite the output of U40 should be nulled approx O volts If this is not present U4O may be bad If with an error signal the inte grator does not integrate increase output voltage at TP 4 with time check U41 U42 and U43 If there are problems with the output circuit U44 and U45 should be checked for proper operation If they appear to operate properly check the supply voltage present at the collector of U45 In the low power state it should be about 15 7 volts and 35 volts in the hi power state If this voltage is not present check diode bridge C
5. INTEGRATED CIRCUITS DESCRIPTION Bidirectional Instrumentation Bus Transceiver t1 Timer Circuit Quad AND OR Select Gates RESISTORS VALUE RATING 2 05K 1 ZW 100K 1 W 57 6K 1 xW 19 6K 1 xW 1 96M 1 ZW 1 0K 1 XW 1 0K 1 1 0K 1 xW 1 0K 1 xW 2 0M 1 xW 3 09K 1 ZW 6 65K 1 ZW 562 ohm 1 kW 9 76K 1 ZW 2 0M 1 511K 1 50K trimpot L A Gain Adjust 50K trimpot L A Offset Adjust 4 7 1 ZW 10 ohm 1 kW 2 05K 1 xW 19 6K 1 xW 57 6K 1 XW 100K 1 ZW 562 ohm 1 3 09K 1 6 65K 1 ZW 9 76K 1 xW 4 75 1 xW 2 4 Resistor Networks 10K 1 xW 33 IK 1 PART NO MC3448A MC3448A MC3448A NE555N CD4019BCN Hd FU Mt Mt Mt Mt Mt Mt Mt Mt Mt Mt Bournes 3006P 1 503 Bournes 3006P 1 503 rrj rrj nj rj Mt Mt Mt Mt Mt Mt Mt Mt Mt Mt Mt F Bournes 8018 08 2 472 Mt F Mt F 65 This Page Intentionally Left Blank 15v C6 GND C10 C48 C47 C11 8V 5 LED 05 LS 1 CS O O GND y U7 LAST USED 48 CR8 S2 TX1 F1 _ FIGURE 6 1 DRC 84C Power Supply 67 0482 15V 15V 5 hl 2 U17 4 AD522
6. K than for tem peratures below 30K 5 4 3 D A Converter a D A Verify Pins 1 through 16 of U38 have parallel data present representing the set point voltage generated by the set point switches The data is in complimentary hexadecimal form As an example a decimal hex table is given in Table 5 1 0482 Jable 2il Complimentary Decimal Hexadecimal Hexadecimal 0 0 F 1 1 E 2 2 D 3 3 C 4 4 B 5 5 A 6 6 9 7 7 8 8 8 7 9 9 6 10 A 5 11 B 4 12 C 3 13 D 2 14 E 1 15 F 0 The following table Table 5 2 gives set of data for pins 1 16 for the two standard curves D and E as well as for the D N standard curve for the platinum input Table 5 2 Curve D T Set Point Data Pin 1 4 5 8 9 12 13 16 004 0 1011 1111 0010 0100 022 0 1010 0001 0100 1001 130 0 1001 0101 1010 1000 300 0 1000 1001 1010 1100 Curve E T Set Point Data 004 0 1100 0000 1110 1100 022 0 1010 0010 0011 0010 130 0 1001 0101 1010 0000 300 0 1000 1001 1010 0000 EE SE EEE Pe SB S SE ENTIA as An 0482 50 _ DIN Standard Curve T Set Point 077 0 130 0 300 0 Data Pin 1 4 5 8 9 12 13 16 0111 1010 1101 1100 0111 0101 0001 1111 0110 0011 1011 1011 The previous sets of data were given for the purpose of data veri fication If the data does not match refer to Section 6 5 to find the problem b D A Calibrate The calibratioin of the D A converter is an iterative process using a span and of
7. Section Page V Calibration and Troubleshooting 5 1 Introduction 47 5 2 Test Equipment 47 5 3 General Remarks 47 5 4 Instrument Calibration 47 5 4 1 Current Sources 47 5 4 2 A D Converter 48 5 4 3 D A Converter 48 5 4 4 Output Buffer 51 5 4 5 DRC L A Option if present 51 5 5 Instrument Tests 55 VI Replaceable Parts List 6 1 Main Board Components 55 6 2 DRC 84C BCD L A and IEEE Components List 63 0482 iii Reference Figure 1 1 Figure 2 1 Table 3 1 Figure 3 1 Figure 3 2 Table 3 2 Table 3 3 Figure 3 3 Table 3 4 Figure 3 4 Table 3 5 Table 3 6 Table 3 7 Figure 4 1 Figure 4 2 Table 5 1 Table 5 2 Table 5 3 Table 5 4 Figure 6 1 Figure 6 2 Figure 6 3 Figure 6 4 Figure 6 5 Figure 6 6 Figure 6 7 Figure 6 8 Figure 6 9 Figure 6 1 Figure 6 1 hi Table of Illustrations Description Model DRC 84C Digital Cryogenic Thermometer Controller Sensor Cable and Monitor Connections Entry Number Correlation DRC 84C Front Panel DRC 84C Back Panel Relative Gain for BCD Option Reset Time Constants for BCD Option DRC 84C IEEE Panel Layout DT 500 DRC Voltage Temperature Characteristic Model DRC 84C showing Rack Mount Kit SW 10A Connector Detail BCD Temperature Output Model DRC Series Remote I O DIN Standard Curve for Platinum Sensors DRC 84C Block Diagram Software Flow Diagram Decimal hex Table Data for Standard Curves D amp E DRC 84C Troubleshooting Notes DRC 84C Trouble
8. by pressing the STORE key after each line is entered Press the RUN key The display will read ENTER To set the set point to 130 0 the remote gain value to 5 the remote reset value to A and toggle the flag to external control type Al130B5CAD and press the CONT key The display will then return those values just set in and return for a new input 10 DIMGS 5 RS 5 P 5 S 10 T3 10 AS 20 20 INPUT ENTER AS 30 OUTPUT706 A 40 ENTER706 G R P S T 50 PRINT 60 PRINT 70 PRINT GAIN G 80 PRINT RESET SRS 90 PRINT PANEL PS 100 PRINT SETPOINT S 110 PRINT TEMPERATURE T 120 GOTO20 Set the address switch to 6 by putting address switches 6 and 7 down 8 5 and 4 up Make sure switches 2 and 3 are up off to allow the DRC8 IEEE to both talk and listen Set switch 1 down on to select CR LF as the delimiter orientation NOTE The address switch is updated only on power up Connect the DRC8 IEEE to the 98034A IEEE interface of the 9825A Turn on the unit and enter the program below by pressing the STORE key after each line is typed Press the RUN key The display will read 33 23 ENTER set the set point to 130 0 the remote gain value to 5 the remote reset value to A and toggle the flag to external control type A130B5CAD and press the CONT key The printer will read the values just set in and return for a new input dimG 5 R 5 P 5 S 10 T 10 AS 20 ent ENTER AS wr
9. If the diode or lead wires are shorted or if the diode is connected backwards the display will read and flash 428 0 In the case of an open current or voltage lead the display will slowly drift higher in temperature from the last voltage reading taken by the A D converter The sensor and readout display for diodes should follow Table 3 4 which illustrates typical values expected of the standard DT 500 DRC or DT 500CU DRC 36sensors for your appropriate curve The DIN standard curve for the platinum sensors is given in Table 3 7 If the instrument or sensor does not agree with values listed in the table within the accuracy of the system consult sections on installation and or section on troubleshooting to determine the cause and cure of the malfunction If an error code is displayed refer to Section 3 13 for possible corrections 3 4 Analog Control The digital set point of temperature is converted to an analog set point of voltage which is then compared to the sensor voltage by summing two respective currents of opposite sign To familiarize yourself with the DRC 84C control section set the instrument so that you are reading and controlling with the same sensor Turn the reset integral control section off Establish a set point temperature several degrees above the display temperature Gradually turn the gain clockwise from a minimum position Note that as the gain is increased the offset between the display temperature and th
10. O 1 4 1 i 1 0 3 1 1 1 1 Min 2 16 02 i _ 0482 Table 3 4 DT 500DRC D Voltage Temperature Characteristic BP TEMP K PROM VOLTAGE 5984 3958 45932 2906 2880 2854 2828 3135 2643 423351 30 NO 3458 2366 29220 2086 4946 29 NO RO RO NN 4807 4667 4527 4387 4247 MN 4108 3968 3618 3269 52919 NO 42210 2220 1041 41521 1172 NI r 28 0909 0646 0119 9592 9066 Rmn 2 21 8338 7610 6984 6359 5646 26 155 0 0 16 0 17 0 0 Aa 22 0482 18 DT 500DRC D Voltage Temperature Characteristic BP 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 135 0 0 0 0 0 155 TEMP K PROM VOLTAGE O O O O O O O O O O O e gt pa pa LH LEE O O O O O 4932 4219 2009 3006 2307 2114 1720 1486 1308 1190 1116 1058 0970 0902 0850 0798 0746 0633 02520 0407 0287 0166 0046 279172 297890 96609 292227 93987 92647 291307 89966 88626 87286 85946 84606 83228 81850 80472 79094 271726 0482 DT 500DRC D Voltage Temperature Characteristic BP 0482 TEMP K 360 365 370 3154 380 O O O
11. and reset can be seen in the following tables highs are denoted as 1 and lows are denoted as 0 0482 Table 3 2 Relative Gain for BCD Option GAIN Pin Pin Pin Pin Relative Gain _48_ Ao Se _42_ 0 0 0 0 0 0 0 1 2 0 0 1 0 25 0 0 1 1 3 25 0 0 0 3 85 0 1 0 1 4 8 0 1 1 0 5 2 0 1 1 1 6 1 1 0 0 13 3 1 0 0 1 14 2 1 0 1 0 14 5 1 0 1 1 15 4 1 1 0 0 15 8 1 1 0 1 16 65 1 1 1 0 17 2 1 1 1 1 Max The gain of the basic instrument is 10 to 1000 with the front panel potentiometer covering a 100 1 span The relative gain is the gain factor above which the base instrument has incorporated These relative gains can be multiplied by about 10 to get overall gain These values were determined to make use of the range of gain most used and the fact that the circuit is based on a negative logarithmic variation of the front panel potentiometer 0482 15 This table can be shifted up or down in terms of overall gain if the customer needs to but should not be necessary The reset amplifier readings take on roughly the same sort of plot as the gain with minimum reset value with all lines low and maximum reset value with all lines high Table 3 3 Reset Time Constants for BCD Option RESET Pin Pin Pin Pin 47 45 43 bl sec 0 0 0 0 Off Open 0 O 0 1 28 0 1 0 21 0 0 1 1 19 0 1 0 0 16 0 1 1 14 0 1 1 0 12 0 1 1 1 10 1 0 0 9 1 8 1 O 1 O 7 1 0 1 1 6 1 1 0 0 5 1 1
12. be made would be to check the input line fuse The type of fuse and line voltage are shown on the rear panel of the instrument If the input line voltage and sensor input voltage have been checked the following sequence should be followed 1 Check all the power supplies for proper operation Power supply lines are indicated in Figure 6 5 Component Layout 2 Check for the waveforms at the following pins and refer to Table 5 3 for waveforms 51 52 a b c d Signal Pin 12 of U31 or Pin 3 of U32 Pin 14 of U32 Pin 7 of 031 A D Output of 031 Pin 2 of U40 Table 5 3 DRC 84C Signals Function Clock signal of A D converter The frequency should be about 50K Hz If not present replace U32 Also check R34 R35 and C26 Integrated signal of A D to deter mine the count period The period should be about 35 seconds If not present check 031 and U32 This is a D C level that is the reference voltage for the inte grator The value should be between 1 4 and 1 8 volts If not present check U32 Also check resistance string R36 39 for proper value and operation The digit drives Pins 19 24 25 26 and 27 are positive going pulses and last for 200 clock pulses The scan sequence is D5 MSD D4 03 D2 and D1 LSD The BCD pins pins 20 23 are positive going signals that go on simultaneously with the digit de vice If not present and signals a
13. sensor inputs are selected With button out heater power maximum is 10 watts LO in detent position full heater power is available 25 watts Hi power LED indicator Selects either the Celsius or Kelvin scale for both the display and the set point A C line cord A C line fuse Diode Sensor A and B input lead terminals Pin 1 Pin E V Pin B I Pin D V Pin H Shield Same connections as for diode sensors Analog output of sensor voltage 0 2 5V pin A and optional linear analog output of temperature 0 4V pin C Pin B is ground for sensor voltage Pin D is ground for linear analog output 0482 3 Q 5 7 08 9 HU mm FIGURE 3 1 DRC 84C Front Panel 0482 9 18 FIGURE 3 2 DRC 84C Back Panel Ll 18 Heater Heater element terminals 25 ohm heater required for 25 watts of power 19 Output power fuse 1 0 ASB specified 20 Interface BCD input of set point gain and reset i output of temperature Also IEEE interface port 21 GND Instrument or case ground 34 3 Temperature Readout The sensor s and heater should be installed following the suggestions listed in the Installation and Application Notes for Cryogenic Sensors brochure in Section VIII Connect the sensor s to the instrument following the diagram in Figure 2 1 Depress the power switch and observe that the display shows the proper temperature relative to the sample temperature
14. that Lake Shore can assure the customer that replacement sensors will be available at any time in the future For details please see Section 1 4 This controller will also use the PT 101 102 103 Series of platinum resistance thermometers which are available from Lake Shore Cryotronics Inc The data sheet for these sensors is included in the back of this manual 1 2 Description The DRC 80 Series is comprised of completely self contained units providing direct digital readout in Kelvin temperature units and for the controllers temperature control by direct analog comparison between the sensor voltage and an analog equivalent of the digital temperature set point The Lake Shore DRC 84C utilizes two temperature sensor technologies to achieve its wide range Silicon diodes for the low range 1 4 330K and platinum RTD s for higher temperatures 30 800K Each sensor type has its own input section which contains appropriate sensor excitation sources signal conditioning and switching A microprocessor in the 84C determines the temperature based on the input section activated the sensor signal and the sensor response curve stored in internal memory Additionally the micro processor generates a voltage equivalent to the control set point temperature for the sensor in use Comparison of that voltage with the actual sensor voltage produces the error signal which is the basis of the 84C s analog control Each input section of the DRC 84C featu
15. variables arises An example of a transmission is as follows FUNCTION FORMAT FOR DATA FORMAT LIMITS X Gain X DELM1 DELM2 0 9 A F Reset X DELM1 DELM2 0 9 A F Front Panel XXX DELMI DELM2 0 9 A F Set Point XXX X DELM1 DELM2 numerics only Temperature XXXX XX DELMI DELM2 numerics only OPEN I LIE 12345678 CABLE CONNECTION SELECT SWITCH Figure 3 3 DRC 84C IEEE Panel Layout 28 0482 The front panel variable has as its first character a remote local status indicator If the first character is a Q then the instrument will respond to front panel set point controls If the character is a 1l then the unit will respond to a set point from the IEEE interface The next two front panel characters are output in a packed format with individual bits representing a piece of data The front panel indi cators are denoted as follows Bit a Bits 1 4 SW 10A Display Sensor switch positions with bit l being the Least Significant Bit and bit 4 being the Most Significant Bit b Bit 5 Type O0 Button Out Si 1 Button In Plat c Bit 6 Control Sensor O0 Button Out A 1 Button In d Bit 7 Display Sensor O Button Out A 1 Button In e Bit 8 Scale EXPAND Mode O Button Out normal 1 Button In Expanded Scale NOTE The expanded scale bit is set only if the button is in and the display temperature is below 100 0 K A chart which shows the pushbutton information and corresponding output char
16. x10 gain is approximately one half of full rotation 4 Reset Adjusts reset time constant of integrator Effectively determines time constant of integrator between 25 and 1 seconds minimum and maximum respectively Note that reset control can be transferred to either the BCD or IEEE options if one of them is present pu 5 NO LABEL Digital temperature display located behind filter panel LED indicators also indicate scale expand which sensor is selected for display which sensor is selected for con trol and type of sensor This Page Intentionally Left Blank 10 10 11 12 13 14 15 16 17 Scale Expand Sensor Display Sensor Control Type Heater Power Scale NO LABEL Diode Sensor Inputs Platinum Sensor Inputs Monitor With button out the display reads to O 1K at all temperatures with button in detent position temperature reads to 0 01K below 30K 0 05K between 30K and 100K and to O 1K above 100K Scale expand is indicated on display panel With button out sensor A temperature is displayed with button in detent position sensor B is read and displayed Sensor being read is also indicated on display panel With button out sensor A is control sensor with button in detent position sensor B is the control sensor Control sensor is also indicated on display panel With button out the silicon diode inputs are selectable with button in detent position the platinum
17. 00 3010 T9000000000D00 3000000000000 O WE s gt sm 0988 E 300900 360 ro 3 801709 00000 20 O gp CR FIGURE 6 5 DRC 84C Component Layout 75 0482 0482 RIM HIGH LOW dd S DS14 DSS 057 259 e PALADAR 7515 pse 8 510 _ 512 ra AANA GND DS1 LSD 5082 7651 RIOS SR1O6 Q 5v 0514 DSS DS7 DS9 st OOOO O m04 2515 056 058 0510 0512 O Or 42752 O R102 NOTES 1 SIGN HIGH ON JB 12 OFF LOW 48 12 NEG ON 2 CPK HIGH ON JB 13 K FIGURE 6 7 DRC 84C Display Board LOW ONJB 1 Component Layout FIGURE 6 6 DRC 84C Display Board Schematic SV DSV C59 C58 gt OP15 or OPO7 o 3 x 0J3 C 2 7 062 21 R86 R89 Y 9 5V DAC HP16 D 15V 15V 12 Ba 4 7420 7 GND R87 5V 2 R88 nt 15V 7 m 35 C56 N 0 052 054 056 R76 7415175 74LS175 74LS1 74123 Ty 50 BEEGERE 910 712 de 75 wo GNDe IT CIP T N NENNE ENN MS 2833 if E mu pu 5 ul 7 gt 8 1 U57 E Dx x 1 N 504 i 5 hese USO B U59 SEN 74257 74257 y REMOTE sara CONTROL GAS GND 1595 2 i lll G c I o R77 HQ 000000 TETY CM 008 59 U58 U57 ol lol fa CHN 300
18. 00006 6000000 see 3000000 E Q 009060 a SPS E 00000000 g 2999 000000 gt DE la LE 828 TT UU TT P TPP E e e 0800888 808089898 08 wc Z I I 4 i 12 BERA BER 5V An TO e T OVON F A Y YN AG e ese ORO OJO DoS eae 2 S38 x ind ird le T a a TAB eo ale ec3e 696 696 ete 39 28 BER 13 58898333 ss E gt L2 2 8 QOOO OC C FIGURE 6 9 DRC 84C BCD L A Component Layout FIGURE 6 8 DRC 84C BCD L A Option 0482 4 79 w 3 Es 0214 0205 ae 13 94 00000 00000 es E T 2557 BD E R D sos ben 5 Y A 2 E B id 81 595 or E ES tt 5v 9000000 0000000 2 H2V u209 7 0208 20600000 2 00000000 S S eT 1 C206 jai WELL gt 34 2 C205 E prc eet me d Crea U207 U206 DE 1 lo eL 9 4 3348 3000000 000000 E Hb 2 586 39 eee TT 3 esa C211 gt 2610 85 pac 934 7 32 0 54 ir PAIN 23424 000900007 09012001 TRT 26 10 52 TI TITT T 40 6 23 10 51 II TT IT TIT 15 234 21 00000000 00000006 e JD 881980 TIT 2 SS n C202 e LES e e a
19. 00V 100V 100V 100V 100V 100V 100V 100V 100V TYPE E Aly Al Al e Ale Al Poly Poly Poly Poly Poly Poly Mylar Ed D Mica D Mylar Mica D Mylar Mica D Poly Mylar Poly Poly Mylar Poly Mylar Mica D Mica D Tan Poly Poly Poly Poly Mylar Mylar Mylar Mylar Mylar Mylar Mylar Mylar 55 756 CIRCUIT DESIGNATION C41 C42 C43 C44 C45 C46 C47 C48 CIRCUIT DESIG ji J2 J3 J4 15 16 37 JA JB JC JD JE JF JG CAPACITORS VALUE RATING 033 uf 100V 033 pf 10V 2 033 WE 100V 68 100V 2400 uf 50V 68 uf 100V 68 uf 100V 68 uf 100V CONNECTORS DESCRIPTION 5 Pin Socket Sensor A 5 Pin Socket Sensor B 7 Pin Socket Monitor BCD IEEE In Out Interface Grey Binding Post Heater V Out Black Binding Post Heater V Out Black Binding Post Heater GND 10 Contact PC Mount Display Board 10 Contact PC Mount Display Board 16 Pin IC Socket SW 10 Input of switch position 24 Pin IC Socket IEEE Interface Connection 24 Contact Edge Card BCD L A Option 14 Pin IC Socket Gain Reset Option Input 10 Contact PC Mount To Display Board TYPE Mylar Mylar Mylar Mylar E Al Poly Poly Poly MFR and PART NO Amphenol 126 218 mates with 126 217 Amphenol 126 218 mates with 126 217 Amphenol 126 193 mates with 126 195 Lake Shore Cryotronics I
20. 191 192 194 196 198 200 96000 203 205 201 204 209 210 2124 214 OHMS 98000 87000 76000 65215 51000 39000 26000 14000 01000 87000 73000 59000 46573 15000 00000 172 174 176 178 84000 68000 52000 36000 19000 67000 49000 32000 13000 94000 75000 56000 38649 17000 75000 54000 33000 12000 91000 69000 46000 0482 0482 TEMP K eee NUUS ES 785 0 790 0 795 0 800 0 RES 216 218 219 2215 22354 225 226 228 230 2325 233 2355 237 239 240 2 amp 2 244 245 247 249 251 2944 254 256 257 259 261 263 264 266 268 269 2715 2734 274 276 278 279 281 283 284 286 288 289 DIN Standard Curve for Platinum Sensors OHMS 25553 01000 78000 55000 31000 07000 83000 59000 34000 10593 84000 57000 31000 06000 79000 22000 25000 97000 71350 42000 14000 85000 56000 27000 97000 68000 39092 07000 77000 46000 14000 83000 51000 19000 87000 56633 22000 88000 25000 21000 87000 53000 18000 83000 ET 26 3 9 IEEE Interface Option The IEEE interface option available for the DRC instruments fully com plies with the IEEE standard 488 1978 and incorporates the functional electrical and mechanical specifications of the standard 3 9 1 General IEEE Specifications and Operation The following di
21. 20 19 18 LT 16 15 160 180 O O O O Table 3 7 TEMP K n Eu DIN Standard Curve for Platinum Sensors RES OHMS 82000 23481 68000 14601 65000 17006 72621 31000 90899 57000 24000 92364 66000 41000 14995 99000 01541 11000 22502 36000 52499 67000 82000 95000 08087 16000 25000 34000 42000 49000 27000 64758 69000 75000 80000 84000 88000 92000 96840 98000 0482 0482 BP 14 13 12 11 DIN Standard Curve for Platinum Sensors TEMP K 285 290 295 300 305 360 365 270 2795 380 O O O O C O O O O O 114 27003 19000 11000 122 123 125 129 1335 139 139 141 OHMS 00000 01000 02000 03000 03000 04385 02000 00000 98000 96000 94000 92000 90000 88000 86000 83000 80000 78433 72000 67000 62000 97000 21000 45000 39000 32000 03000 95000 86000 127 78000 69000 121 61563 20000 40000 135475 31000 20000 09000 23 24 BP 10 DIN Standard Curve for Platinum Sensors TEMP K 300 565 240 272 280 O O O O O RES 142 144 146 148 150 152 154 1565 158 159 101 163 165 30000 169 167 IJ 180 03545 85000 185 187 182 183 189
22. 3 Detailed Description A detailed description of the operation of the DRC instrument is outlined in the following sections The Figures required for each sec tion will be denoted in that section 4 3 1 Power Supplies Please refer to Figure 6 1 Schematic 1 for the following dis cussion There are eight different power supplies incorporated in the DRC series instruments The main power transformer TX1 has split pri maries for 115 or 230 volt AC operation The slide switch 52 selects the proper line voltage The first secondary is output through leads 1 and 3 This secondary is rectified by CR1 and a floating 15 volt supply is obtained through C1 and the positive 15 volt regulator Ul This supply is used to power the constant current sources for diodes in the case of the DRC 80C and both diodes and platinum sensors in the case of the DRC 84C The second secondary through leads 2 4 and 6 is full wave bridge rectified by CR2 5 A 15 volt supply is generated by C2 C7 and a posi tive 15 volt regulator U2 The negative 15 volt supply is generated by C3 C8 and voltage regulator U3 Both these supplies are used in the A D and D A converters as well as the analog section Regulators U6 and U7 with capacitors C10 C47 C48 and C11 generate plus and minus 8 volts for the low voltage low offset operational amplifiers used in the analog section The third secondary is through leads 8 10 and 12 and is full wave rectified by CR
23. 53 NCc x 2 xL Z o 115 8C39 4 92 10 ED 2 2 R63 Last Used u45 C46 CR18 S11 TX2 F2 R68 TX2 J ORNIS RED YLW 3 5 18 4 CRIE CR16 C45 R68 DK i fig 48 IT FIGURE 6 4 DRC 84C Analog Output Section _ 73 L2 A C LOW Og 206 RI o O lt gt 563 20 o 6 C LIG E g OOO 2010 M OTI 2040 00000 GO DM Se ae 00000 008006 5 EY y io e DER V 5209 y OE 030 100000 2 iin A MES X oe 29900 800006 5 l 300000 T 30000000000 so o sel 000000 2 205 Sol ommo i sol Jo jor 0108 soli H 04793 2 9 000 0000000 00000000 00000000 0000000 B PES 1S 5 x o z 00 0000000 60000000 900000007 6000000 o ES A 3 00 d 000 00000 Sane 9904 00000 00 5 TEN S 00000 9000000 300000005 000000 X e 0 x O m So __ 000000000000000000 Bor to 000000 04000 Q O 000000 00000 z 0000000000000000000 20 aa 2000 a a a a 00 0000000000 000000 00 doo E E 000000 so 0000000000 i g SOHO 000000 4 gt 5 x OO 0 20 0090000 00090000 0000000 30000000 60060000 8000000 O O soo 00000000 So 30 300000
24. 6 7 The five volt supply that is used by the TTL IC s is formed by C4 C9 and a 5 volt positive voltage regulator U4 A 5 volt half wave supply for the LED display is provided by CR8 C5 and the 5 volt positive regulator U5 The reason for splitting the 5 volt supplies is to avoid the LED display from loading down the main 5 volt supply The eighth supply is used in the output power section and will be covered there 2902 40 4 3 2 Precision Current Sources and Input Switching Please refer to Figure 6 2 Current Sources Input Connections Switching Schematic 2 for the following discussion An explanation of the constant current sources will be limited to the Sensor A source of the silicon diode since the four current source Circuits are exactly the same with the exception of resistor values be tween the platinum and diode sources to achieve the two different values of current A precision reference voltage is generated by an internal temperature stabilized precision voltage reference U12 Resistors R11 and trimpot R12 vary this voltage to match the voltage generated by feedback resistor R13 Resistor R13 has been selected to generate 4 99V by an adjustment of the reference voltage to equal this feedback voltage Op amp U15 drives an FET U16 to generate a current flow through Pins A and B of the sensor connector The voltages generated by the sensors are fed to front panel push button switches 57 58 and S9 Selector s
25. ATN line goes high false then the devices addressed to send or receive data perform their functions while all others ignore the DATA lines Transfer of the information on the data lines is accomplished through the use of three signal lines DAV Data Valid NRFD Not Ready For Data and NDAC Not Data Accepted These signals operate in an interlocking handshake mode The two signal lines NRFD and NDAC are each connected in a logical AND to all devices connected to the bus The DAV is sent by the talker and received by listeners while the NRFD and NDAC are sent by listen ers back to the talker The General Interface Management Lines manage the bus and control the orderly flow of commands on the bus The IFC Interface Clear message 0482 0482 basically clears the interface to a known state appropriate to the device being addressed SRQ Service Request is used by a device to indicate the need for attention or service and to request an interruption of data flow REN Remote Enable is used to select between two sources of device data an an example front panel or rear panel controls on a measurement device EOI End or Identify indicates the end of a multiple byte transfer sequence or along with the ATN line executes a polling sequence 3 9 2 Specific Operation of the DRC8 IEEE Interface The DRC8 IEEE allows for the remote control of set point gain and reset It also provides a digital output of temperature in Kelvin th
26. Condition The display temperature calculated for the platinum sensor is below 20 0 K Since the temperature in this range would be in accurate the error code has been added This code will also be displayed if an input is selected that does not have a platinum sensor in it The set point input is below 20 0 K for the platinum sensor This is an inaccurate region of the platinum curve The instru ment will continue to look for a set point above 20 0 K and will not update the temp erature information until this is done The set point is above 399 9 K for the silicon diode The instrument will continue to look for a set point within the upper limit of the sensor The set point is above 799 9 K for the platinum sensor The instrument will continue to look for a set point within the upper limit of the sensor 0482 0482 SECTION IV Theory of Operation Gul Introduction The DRC 84C Thermometer Controller is in actuality two instruments a digital thermometer and an analog controller A general description of the instrument is given in Section 4 2 with a detailed description in the following sections 4 2 General Description Refer to the DRC 84C Block Diagram Figure 4 1 for the following discussion Two precision 10 microampere constant current sources are used to excite the diode thermometers Models DT 500 DRC DT 500CU DRC 36 or any DT 500 series sensor with a precision option Front panel push buttons select w
27. Hewlett Packard 5082 7651 Hewlett Packard 5082 4494 58 DIODES CIRCUIT DESIG TYPE MFR and PART NO DS6 Pilot Light LED Hewlett Packard 5082 4494 Scale Normal Indicator DS7 Pilot Light LED Hewlett Packard 5082 4494 B Display Indicator DS8 Pilot Light LED Hewlett Packard 5082 4494 A Display Indicator DS9 Pilot Light Indicator Hewlett Packard 5082 4494 B Control Indicator DS10 Pilot Light Indicator Hewlett Packard 5082 4494 A Control Indicator DS11 Pilot Light Indicator Hewlett Packard 5082 4494 Hi Power Indicator DS12 Pilot Light Indicator Hewlett Packard 5082 4494 Low Power Indicator DS13 Pilot Light Indicator Hewlett Packard 8052 7656 DS14 Pilot Light Indicator Hewlett Packard 5082 4494 DS15 Pilot Light Indicator Hewlett Packard 8052 4494 INTEGRATED CIRCUITS CIRCUIT DESIG DESCRIPTION PART NO Ui 15V Positive Voltage 7815 Regulator U2 15V Positive Voltage 7815 Regulator U3 15V Negative Voltage 7215 Regulator UA 5 Positive Voltage 7805 Regulator U5 5V Positive Voltage 7805 Regulator U6 8V Positive Voltage 78L08 Regulator U7 8V Negative Voltage 79M08 Regulator U8 Operational Amplifier LM308 U9 34163 U10 Operational Amplifier LM308 U11 EE Es 3N163 U12 Temp Stabilized Voltage LM399H Reference Current Sources U13 Operational Amplifier LM308N Current B U14 Pa E Lo 3N163 Sensor B Current Driver 0482 1 0482 INTEGRATED CIRCUITS CIRCUIT DESIG DESCRIPTION
28. I The cable connector meets IEEE 488 1978 standards and is polarized for proper cable insertion The following table shows cable connector contact wiring for the IEEE 488 bus 27 Contact Signal Line Contact Signal Line 1 DIO1 13 D105 2 102 14 DIO6 3 DIO3 15 DIO7 4 DIO4 16 DIO8 5 EOI 24 17 24 6 DAV 18 Gnd 6 7 NRFD 19 Gnd 7 8 NDAC 20 Gnd 8 9 IFC 21 Gnd 9 10 SRQ 22 Gnd 10 11 ATN 23 Gnd 11 12 SHIELD 24 Gnd LOGIC Note Gnd n refers to the signal ground return of the referenced contact EOI and REN return on contact 24 When addressed as a TALKER the interface outputs gain and reset set tings front panel settings including Remote Local status set point and display temperature in the form of five string variables After each one of the variables is output delimiters DELMI and DELM2 are transmitted After the fifth variable the last delimiter has the EOI line set for end NOTE In programming for an input from the DRC8 IEEE interface five string variables must be used or read into the computer or the interface will hang up waiting to output all of the data outputting data to array the array must have enough elements to allow the input of all five variables from the DRC8 IEEE interface in this case the number of elements is 27 Since there are five sets of delimiters output and most computers use these delimiters to terminate string variables the need for five string
29. O O PROM VOLTAGE 0 76338 0 74961 0 73582 0 72170 0 70757 0 69344 0 67931 0 66518 0 65105 0 63693 0 62280 0 60867 0 59455 0 58080 0 56707 0 55334 0 53960 0 52649 0 51337 0 50026 0 48714 0 47403 0 46057 0 44711 0 43365 0 42019 0 40613 0 39208 0 37802 0 36397 0 34940 0 33482 0 32025 0 30508 0 29111 0 27654 0 26197 0 24739 0 23325 0 21911 0 20497 0 19083 0 17774 0 16464 0 15155 19 Table 3 5 SW 10A CONNECTOR DETAIL Shield T V V I V V I V V I V Ve I V V l V V V V Va I V Ve I V Va I lt rg O C 1 1 1 2 2 2 3 3 3 4 4 5 2 5 6 6 6 y 7 7 8 8 8 9 9 9 10 exo 20 0482 Table 3 6 BCD TEMPERATURE OUTPUT MODEL DRC SERIES REMOTE I O 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 1 3 5 7 911 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 BCD TEMPERATURE BCD TEMPERATURE BCD TEMPERATURE BCD TEMPERATURE OUTPUT SET POINT INPUT OUTPUT SET POINT INPUT Data Valid Ground Trend Bit SW B2 1 01 O 1 SW B3 Remote Control 00 O O Internal 1 External gt o o Not used 5V BO Reset BO Gain B1 Reset B1 Gain B2 Reset B2 Gain B3 Reset B3 Gain 400 IN Not used e N O e N 0482 21 299 BP 28 27 26 25 24 23 22 21
30. R14 7 gt BV 15V n do U18 AD522 DIODE B 1 16 6 i Last used O 3 4 1 4 3 EIS 77789 510 50 DISPLAY 50 CONTROL SENSOR SENSOR SELECT F1 R76 FIGURE 6 2 DRC 84C Current Source Input 0482 Connections Switching 69 5 74LS139 iU 3 02 SET POINT J 36 52 LATCH 035 52 U34 JE 32 JE 42 OPTION LATCH DISPLAY Y 0 3 gt LATCH JG 2 gt JG T gt IGN S lt INDIGNTOR 3205 85 En ops j 7 Ns Pe iX 1 ER SG TY CET fm HD Sie Mt Epp pup jQ Sp PIE Min SH 10 Hes E SR 5 19 2 15 lt 2 205 o SV LED 23757 18 025 5 7 2357 14 7415267 2357 3 _ 2367 21 R69 V R7O V R23 i U33 AA C47 7555 2 ____ CR11 8 535 511 Y TX1 F1 R7O C26 46 13 gt gt gt JE J JC FIGURE 6 3 DRC 84C Microprocessor Section 0482 0482 7 9388 2 L2 gt 214 15 R41 033 14 4 E HP16 BGC 20 C44 TL i ooo Sank 17 TP1 A R45 R46 8 c3 S5B R52 R49 NC SS 8 C32C33 R
31. R15 18 switch S2 and C45 for proper operation TX2 may also need to be replaced Signal paths should also be checked If signals are present at Source components and not at destination components a printed circuit problem requiring a repair of the printed circuit foil may be required Continuity checks between points will turn up any unwanted open circuits in signal paths If the signals at the component pins outlined in Table 5 3 and 5 4 are present and a problem still exists a factory representative should be contacted 53 This Page Intentionally Left Blank 0482 6 1 Main Board Components CIRCUIT DESIGNATION C1 C2 C3 C4 05 C6 C7 C8 c9 C10 C11 C12 C13 C14 C15 C16 C17 C18 C19 C20 C21 C22 C23 C24 C25 C26 C27 C28 C29 C29A C30 C31 C32 C33 C34 C35 C36 C37 C38 C39 C40 SECTION VI DRC 84C CAPACITORS VALUE 470 470 uf 470 uf 2700 uf 470 uf 1 uf sl HE 1 uf st MP 68 uf 0015 uf 150 pf 0015 uf 150 pf 0015 f 150 pf Not used 68 uf 33 XE 68 yf 68 uf 68 uf 68 uf 33 uf 330 pf 330 pf 1 5 1 uf 68 uf 68 uf 68 nf 033 uf 033 uf uf 053 pE 035 Not used 039 033 uf 035 uf REPLACEABLE PARTS LIST RATING 35V 35V 35V 25V 35V 100V 100V 100V 100V 100V 100V 100V 500V 100V 500V 100V 500V 100V 100V 100V 100V 100V 100V 100V 500V 500V 25V 100V 100V 100V 1
32. Resistor Network Bournes 8 2 472 R30 121K 1 Mt F R31 301K 1 xW Mt F R32 36 5K 1 Mt F R33 121K 1 XW Mt F R34 10K 1 ZW Mt F R35 33 2 1 ZW Mt F R36 107 ohm R37 196 ohm R38 5K A D Adjust Bournes 30594 1 502 R39 1 18K 1 xW MES Es R40 511K 1 ZW R41 50K Trimpot D A Span Adjust Bournes 30594 1 503 R42 50K Trimpot D A Zero Adjust Bournes 30594 1 503 R43 2 2 M ohm 1 W Mt F R44 100K 1 ZW Mt F R45 100K 01 xW Vishay B8111 S102C R46 100K 01 W Vishay B8111 S102C R47 29525 1 ZW Mt F R48 1 ZW Mt F R49 10K 1 59 Mt F R50 100K 1 ZW Mt F R51 10K 1 W ME F R52 10 ohm 1 ZW Mt F R53 10K Potentiometer Integral to Gain Switch R54 20K 1 xW MET R55 2K 1 ZW MES EA i 0482 62 CIRCUIT DESIG R56 R57 R58 R59 R60 R61 R62 R63 R64 R65 R66 R67 R68 R69 R70 R71 R72 R73 R74 R75 R76 CIRCUIT DESIG S1 52 53 54 55 56 58 S9 510 511 RESISTORS VALUE RATING 1K 1 xW 14 7K 1 ZW 1 96 M ohm 1 W 332K 1 XW 10K 1 ZW 100 ohm 1 XW 100K Potentiometer Integral 7 87K 1 XW 1 96 M ohm 1 W 200K 1 ZW 200K 1 ZW 374K 1 xW 47 ohm 5 1W 4 75K 1 W Es 1 xW 10K 1 W 1K 1 XW 10K 1 W 1K 1 W 976K 1 W 976K 1 ZW SWITCHES DESCRIPTION ON OFF Switch 115 230 Line Switch Reset ON Switch Reset Remote Switch Gain Remote Switch Hi Low Heater Output Select Control Sensor Select Display Sensor Select Trend Sensor Select Trend Se
33. User s Manual Model DRC 84C Digital Cryogenic Thermometer 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 L akeShore Lake Shore Cryotronics Inc 575 McCorkle Blvd Westerville Ohio 43082 8888 USA E Mail Addresses sales Qiakeshore 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 govemment or other contractual support or relationship whatsoever has existed which in any way affects or mitigates proprietary rights of Lake Shore Cryotronics Inc in these developments Methods and apparatus disclosed herein may be subject to U S Patents existing or applied for Lake Shore Cryotronics Inc reserves the right to add improve modify or withdraw functions design modifications or products at any time without notice Lake Shore shall not be liable for errors contained herein or for incidental or consequential damages in connection with furnishing performance or use of this material Obsolete Manual A
34. acter is shown below This is data represented by the second character of the Panel information variable or bits 5 8 above Output Bit Expanded Display Control Character Representation Scale Sensor Sensor Type 0 0000 no A A Si 1 0001 no A A Plat 2 0010 no A B Si 3 0011 no A B Plat 4 0100 no B A Si 5 0101 no B A Plat 6 0110 no B B Si 7 0111 no B B Plat 8 1000 yes A A Si 9 1001 yes A A Plat A 1010 yes A B Si B 1011 yes A B Plat C 1100 yes B A Si D 1101 yes B A Plat E 1110 yes B B Si F 1111 yes B B Plat 0482 29 The SW 10A switch position is represented by the characters 1 9 and A The 1 9 stands for positions 1 thru 9 the A stands for position 10 Ihe switch position information is only present for the B display sensor When the A position is selected as display sensor the position is returned as zero When there is no position present for the B display sensor the switch position is returned as zero An example of the panel information for a DRC instrument that is in remote accepts set point commands from the IEEE is in the expanded scale mode has B as display sensor A as control sensor and has an SW 10A position of 2 would look like 1C2 When the instrument is in display A mode the external switch position is ignored and the switch position character is set to zero An example of a transmission for an instrument which has switch l of the IEEE address switch up at power on a gain setting of 5 a reset settin
35. address switch to 6 by putting address switches 6 and 7 down 8 5 and 4 up Make sure switches 2 and 3 are up off to allow the DRC8 IEEE to both talk and listen Set switch 1 down on to select CR LF as the delimiter orientation NOTE The address switch is updated only on power up Connect the DRC8 IEEE to the IEEE interface of the HP 85 Turn on the unit and enter the program below including line numbers by pressing the END LINE key after every line Press the RUN key The display will read ENTER To set the set point to 130 0 the remote gain value to 5 the remote reset value to and toggle the flag to external control type in A130B5CAD and press the END LINE key The display will then return those values just set in and return for a new input 32 0 0482 0482 10 DISP ENTER GINPUTAS 20 OUTPUT706 A 30 ENTER706 G R P 55 75 40 PRINT 50 PRINT 60 PRINT GAIN G 70 PRINT RESET RS 80 PRINT PANEL p 90 PRINT SET POINT 58 100 PRINT TEMPERATURE TS 110 GOTO10 3 9 3 3 HP 9845B Set the address switch to 6 by putting address switches 6 and 7 down 8 5 and 4 up Make sure switches 2 and 3 are up off to allow the DRC8 IEEE to both talk and listen Set switch 1 down on to select CR LF as the delimiter orientation NOTE The address switch is up dated only on power up Connect the DRC8 IEEE to the 98034A IEEE inter face of the 9845B Turn on the unit and enter the program below including line numbers
36. d shield C ALTERNATE SENSOR CABLE ground 2 5 sensor voltage A TOmV K temperature optiomE ground D MONITOR OUTPUT 0482 FIGURE 2 1 Sensor Cable and Monitor Connections 0482 SECTION III Operating Instructions 3 1 Introduction This section contains a description of the operating controls and their adjustment under normal operating conditions and typical controller applications These instructions are based upon the instrument having been installed as outlined in Section II The diode polarity as shown in Figure 2 1 a in particular must be correct For the DRC 84C instrument a 25 ohm heating element is assumed attached to the Heater terminals as shown in Figure 2 1 b Jaz Controls Indicators Connectors The operating controls indicators and connectors on the DRC 84C 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 entries in Table 3 1 Table 3 1 Entry Number Correlation NO KEY NAME FUNCTION 1 POWER A C line switch ON OFF Display serves as indicator light 2 NO LABEL Digital set point Has O 1 K resolution Gain Variable gain allows adjustment of overall controller gain over 100 to 1 range Maxi mum gain is full clockwise prior to detent position labeled REM which transfers gain control to remote BCD or IEEE option when present The potentiometer is logarithmic so that
37. drive the heater circuit When the error signal goes to zero the integrator supplies a constant signal which keeps the output power constant and therefore the temperature constant For positive error signals i e the sensor temperature greater than the set point temperature the output power is kept on by the charge stored on the integrator If the error signal stays positive this charge drops off the integrator which gradually reduces the output power towards zero The output of the integrator would go positive towards the supply voltage except that the diode CR13 shorts this output at about 0 4 volts The available power to the heater is generated by a power supply that consists of transformer TX2 full wave bridge rectifier CR15 18 and a capacitor C45 This transformer has its input voltage 115 230 selected by 82 A split secondary is used for HI LO power selection The low end of the secondary Pin 1 of JN is carried on to the diode full wave bridge One of the other two points of the secondary is selected by 6 the HI LO power selector on the front panel This switch either picks a portion of the secondary voltage LO power mode or the entire secondary HI power mode The voltage selected is then rectified by the diode bridge and filtered by its capacitor and the power trans istor and load This voltage is applied to power transistor U45 The amount of voltage applied to the load J5 to J6 is then dependent on its loop gain
38. e 3 AG Slow Blow 90V 125V 3 4A 210V 250V 4 10A Fuseholder F2 Heater Fuse 3AG Slow Blow 1A Fuseholder TX1 Power Transformer TX2 Heater Transformer Power Cord 115V CEE Color Coded 230V Strain Relief Heat Sink for U4 MFR amp PART NO Bussmann MDL 3 4 Bussmann MDL 4 10 Littlefuse 342004A Bussmann MDL 1 Littlefuse 342004A LSCI supplied TX 696 107 TX 696 106 LSCI supplied Belden 17236 Belden 17740C H H Smith 939 Aavid 5772B RESISTORS CIRCUIT DESIG VALUE RATING TYPE R1 3 74K 1 R2 20K 1 ZW Mt F R3 5K Trimpot Bournes 3059Y 1 502 R4 20K 1 EW Mt F R5 5K Trimpot Bournes 3059Y 1 502 R6 12K 1 Mt F R7 12K 1 Mt F R8 10K 1 Mt F RO 5K Trimpot Sensor B I Source Adjust Bournes 30594 1 502 R10 499K 1 ZW Mt F R11 10K 1 xW Mt F R12 5K Trimpot Sensor A I Source Adjust Bournes 30594 1 502 R13 499K 1 W Mt F 0482 RESISTORS CIRCUIT DESIG VALUE RATING TYPE R14 100K Trimpot 1 Mt F R15 10K Trimpot Bournes 3059Y 1 104 R16 16 2K 1 ZW MESE R17 100K Trimpot Bournes 3059Y 1 104 R18 10K Trimpot Bournes 3059Y 1 103 R19 16 2K 1 ZW Mt F R20 20K Trimpot Output Buffer Adjust Bournes 30594 1 203 R21 10 ohm 1 Mt F R22 4 75 1 W Mt E R23 4 42 1 W Mt F R24 4 75 1 Mt F R25 4 75K 1 ZW Mt F R26 4 7K Resistor Network Bournes 8 2 472 R27 4 7K Resistor Network Bournes 8 2 472 R28 4 7K Resistor Network Bournes 8 2 472 R29 4 7K
39. e 63 64 CIRCUIT DESIGNATION CR200 CIRCUIT DESIGNATION U51 U52 U53 U54 U55 U56 057 058 059 U60 U61 U62 U63 U200 U201 U202 U203 U204 U205 U206 U207 U208 U209 U210 DIODES TYPE MFR and PART NO Silicon IN4148 INTEGRATED CIRCUITS DESCRIPTION PART NO Quadruple D type flip flops 7415175 with clear y 74 8175 ds 7415175 74LS175 4 normally open SPST LF13202 JFET Analog Switches Dual Retriggerable Monostable 74123 Multivibrator Dual SPST MOS Analog HI1 5043 5 Switches 4 normally open SPST LF13202 JFET Analog Switches Tri State Quad 2 data 7808227 Selectors Multiplexers Tri State Quad 2 data 7415293 Selectors Multiplexers Operational Amplifier OPO7EJ 16 Bit D A Converter HP16 DGC Dual 4 input Positive NAND 7420 Gates Peripheral Input Output MK3871 Circuit P10 General Purpose Interface MC68488 Adapter Hex Inverting Buffer CD4049 Tri State Octal Buffers DM81LS95N Tri State Octal Buffers DM81LS95N Quad 2 Input NOR Gate 74LS02 Quadruple D type flip flops 7415175 with clear H 741 5175 4 normally open 5 5 LF13202 JFET Analog Switches n LF13202 Bidirectional Instrumentation MC3448A Bus Transceiver 0482 0482 CIRCUIT DESIGNATION U211 U212 U213 U214 U215 CIRCUIT DESIGNATION R72 R73 R74 R75 R76 R 77 R78 R79 R80 R81 R82 R83 R84 R85 R86 R87 R88 R89 R200 R201 R202 R203 R204 R205 R206 R207 R208 R209 R210 R211 218 R219 R220
40. e present values of set point gain and reset as well as the status of the front panel switches and Remote Local status Address and function selection are made via a switch package located on the rear panel of the DRC instrument see Figure 3 3 DRC8 IEEE panel lay out Positions 4 8 of the switch are the address switches for the interface with 4 being the most significant bit and 8 being the least significant bit As an example with switches 5 6 and 7 ON and switches 4 and 8 OFF the address selected is 14 or E base 16 Position 3 of the switch package is the TALKER select with position 2 being the LISTENER select Both functions are selected with both switches OFF or up while either can be deselected by turning the appropriate switch ON or down Switch position 1 is used to select the order in which the output delimiters are put onto the IEEE bus The following table gives the deli miter orientation versus switch position Delimiter Order Switch 1 Position Delm 1 Delm 2 Up OFF LF CR Down ON CR LF The use of this switch allows the DRC8 IEEE to interface to controllers which accept both forms of delimiters to terminate input strings NOTE the address switches are updated on power up only The address and delimiter orientation is read only when the instrument is turned on Any change in the address switch while the instrument is on will be ignored The DRC8 IEEE transmits and receives all characters in ASCI
41. e desired temperature This information is then input into the microprocessor and by using the same breakpoint temperature information a digital set point voltage is calculated This voltage is output through data latches to a 16 bit D A converter where an analog voltage correspond ing to the set point temperature is generated 37 38 SENSOR SENSOR B SENSOR A SENSOR B SILICON DIODE SECTION SENSOR CURRENT J SOURCES INPUTS AND SWITCHING PLATINUM RTD SECTION COPYRIGHT 1981 Lake Shore Cryotronics Inc DRC 84C BLOCK DIAGRAM ANALOG TO DIGITAL CONVERTER DISPLAY SENSOR DIGITAL TO ANALOG CONVERTER CONTROL SENSOR FIGURE 4 1 DRC 84C DISPLAY MICROCOMPUTER T1 I OPTIONAL m p DIGITAL INTERFACE bs d THUMBWHEEL SET POINT ANALOG CONTROLLER HEATER TO CONTROL HEATER Block Diagram 0482 70482 The control sensor voltage is input buffered and fed to an error amplifier along with the opposite sign set point voltage The error amplifier generates a signal proportional to the gain setting With the addition of reset integral output power is controlled and applied to the system through a twenty five watt heater The microprocessor also controls the BCD and IEEE options These options remotely control the set point gain and reset as well as indicat ing the display temperature 4
42. e set point 12 0482 0482 will be decreased The gain potentiometer is logarithmic with rotation and covers a 100 to 1 range so that the gain at mid rotation is ten times the minimum gain With most systems an oscillation in temperature will occur at some clockwise rotation Further clockwise rotation will cause a wild oscilla tion in temperature The gain should then be backed off until a stable control temperature occurs Note that an offset between display tempera ture and set point will still be present Finally turn on the reset control With the addition of reset the temperature error between setpoint and control temperature should reduce to zero The rate at which this reduces to zero is determined again by a clockwise rotation with the shortest time constant occurring at full clock wise rotation Note that the system can become unstable again with too much reset added Slight variations in the gain and or reset should give stable temperature control The HI LO power switch also changes the loop gain with the HI posi tion increasing the gain by a factor of approximately two It may be necessary when changing from LO to HI power setting to reduce the gain slightly to compensate for the increased overall loop gain 32 2 Analog Output of Temperature The analog output of temperature takes the display temperature and converts it to an analog signal which has a sensitivity of 10 mV K under normal operation The analog out
43. ensor Excitation Current source 10 microamperes for each sensor in silicon diode section 0 5 milliampere 0 00596 for each sensor in platinum RTD section Sensor Response Curves Silicon Diode Section Domes tic US units require Sensor Curve D Export units require Sensor Curve E Sensor curves subject to change refer to manual for proper curve when reorder ing Sensors Curves to match existing Sensors available on special request See also DRC Precision Option Platinum RTD Section Standard response curve is based on 0 1 interchangeability at 09 and temp erature coefficient 0 100 C of 0 00385 C Refer to Lake Shore PT 100 Technical Data for details Special calibrations are available and may be incor porated into the 84C via the DRC Precision Option Input Resistance Greater than 1000 megohms Maxi mum Sensor Power Dissipation Silicon diode 25 W at 4 2K Platinum 254W below 80K increasing 100 W at 273K Temperature Readout Display 4 digit 1 1 cm 0 43 LED shows temperature directly in Kelvin or Celsius as selected by front panel switch Display Sensor can be selected independent of Control Sensor within each section Resolution 0 1K or 0 1 C Scale Expand increases resolution to 0 01 for temperatures below 30K and 0 05K for 30 100K no increase in accuracy Accuracy 20 25 C ambient Silicon diode 0 5 at 4K and 77K 1 0K at 300K with standard sensor Accuracy with Lake Shore calibrated Se
44. etermined the proper Voltage Temperature Break Point is determined The program finds the correct break point for temperature determination by checking each break point voltage to see if it is lower than the input voltage As the break point is found the temperature is calculated using the following equation Vi dT T BP AD av BP where T is temperature inK is break point voltage VAD is input voltage dT is slope between successive break points dV Tap is break point temperature After the correct temperature has been calculated the program looks to see if the instrument is in the scale expand mode In this mode the front panel display converts to a resolution of O1K from 1K when below 100 1f there is no LO 1 error condition in the case of the platinum sensor the temperature is output in a bit parallel digit serial form and is latched into the display board Once the temperature has been output the program looks to the set point The program determines if there is an option present and if there will be a set point input from that option If no option is present the program reads the front panel thumbwheel switches If an option is present the front panel switches are ignored and the set point is read from the remote source The program then determines whether the LO 2 HI 1 or HI 2 errors have occurred If so the program continues and outputs the appropriate error to the display and loops back to inp
45. fset potentiometer to get a calibrated reading The reading can be calibrated in one of two methods 1 Method 1 Use of the Voltmeter 2 With the voltmeter connected between ground and TP 1 a negative voltage for diodes should be present that corresponds to the set point temperature from the front panel thumbwheel switches As an example Curve D is used to calibrate the instrument for a D curve sensor the curve the instrument has can be noted from the sticker on PROM U20 The curve is denoted in parenthesis A temperature is dialed in to give a fairly low voltage reading for example 330 0K The voltage read on the voltmeter should be 29111 V Trimpot R41 is varied until this reading is obtained Then a temperature point is selected to give a higher voltage reading for example 21 0K The voltage read on the voltmeter should be 1 3505 V Trimpot R42 is varied until this reading is obtained This process should be repeated until no further trim adjustments are needed Method 2 Use of Display The DRC 84C incorporates a method by which the D A con verter can be tied to the input sensor voltage line With no sensor in either rear panel connector 1 and TP2 should be tied together This links the D A output with the A D converter input The same iterative process should be used as in Method 1 with the exception that the display should read the setpoint setting 0482 0482 Note This method sho
46. g of C scale expand button in A as display sensor B as control sensor no SW 10A input set point of 130 0 K and a display of 24 06 K is in remote control IEEE and has Si as type would look like this 5 LF CR C LF CR LAO LF CR 130 0 CR 0024 06 LF CR EOI SET ON FINAL CR When there is a display error message this message is transmitted over the bus in the temperature variable The following table gives the display error and the corresponding error code output from the IEEE Display Sensor Interface Equivalent LO 1 E100 00 HI 1 E200 00 HI 2 E300 00 LO 2 E400 00 When addressed as a LISTENER the interface must receive a code function and code settings to set parameters The codes and commands along with formats are CODE FUNCTION FORMAT FOR DATA FORMAT LIMITS X A Set Point Variable forms of XXX X only numerics accepted B Gain X 0 9 A F C Reset X 0 9 A G D Flag Toggle The A command allows for considerable flexibility If the A com mand is received but not followed by any numerics the set point is set to zero The internal program is structured so that the last three numerics before the decimal point are accepted and the first numeric after the decimal point All other ASCII characters are ignored except for B C and D The following examples should illustrate the flexibility of the input This format makes the allowance for the implied sign before any numeric variable output in basic program
47. hangeability at 0 C and a temperature coefficient O to 100 C of 0 00835 C The curve conforms to DIN standard 43760 and is published in the Lake Shore PT 100 Technical Data sheet Custom calibrations are avail able and can be incorporated into the 84C via the DRC Precision option Since silicon diode sensors can be damaged by exposure to temperatures above 380K DT 500DRC Sensors should not be used above 330K to prevent deter ioration of their epoxy seals precautions are recommended in designing systems for operation at higher temperatures The preferred approach is to have diode sensors installed only when the system is operated below room temperature Special software limits and error codes are generated if the instrument is set to control a point above or below the silicon diode or platinum sensor temperature limits see Section 3 13 Table of Error Condi tions Control temperature is easily selected and read directly in Kelvin or Celsius on front panel digital thumbwheel switches and an adjoining scale select switch The switches provide quick and constant display of the set point with a resolution of 0 1K or Temperature controllability is a function of system design and performance is often better than 0 1 degree Both the gain and reset are variable and can be set from the front panel to enable the Controller to be precisely tuned to match the system response over any temperature region Ample gain and reset have been desig
48. hich sensor is to be displayed and or controlled Two precision 0 5 milliamperes constant current sources are used to excite the platinum resistance thermometers Models PT 101 102 and 103 Two ultra stable amplifiers multiply the voltage signal by a factor of 20 so that 100 ohms is seen as a 1 0000 volt signal Front panel push buttons select the type of sensor diode or platinum as well as which sensor is to be displayed and or controlled The display sensor voltage is fed to an Analog to Digital converter pair A D where it is converted to a digital voltage signal proportional to the sensor voltage The multiplexed BCD outputs from the A D are sampled and verified by the microprocessor The microprocessor executes a program which takes the sampled sensor voltage and using break point voltage and temperature information stored in a tabulator array calcu lates the associated Kelvin temperature to better than 0 01 Kelvin The microprocessor then outputs the temperature information to the display board The decoder driver decodes this temperature data latches the information and drives the display digits The sensor display voltage is also available as a buffered output through the monitor plug on the rear of the instrument The control section of the instrument is essentially independent of the display or thermometer section To control at a particular temper ature the thumbwheel switches on the front of the instrument are set for th
49. imiter selection Switch 1 Position Input Delimiter UP OFF CR DOWN ON LF The DC Device Clear command on the IEEE bus will clear the flag and return control of the set point to the front panel ls 3 9 3 Sample Programming This section contains some sample programming for the DRC8 IEEE option 3 9 3 1 Commodore Pet CBM 2001 Set the address switch to 6 by putting address switches 6 and 7 down 8 5 and 4 up Make sure switches 2 and 3 are up off to allow the DRC8 IEEE to both talk and listen Set switch 1 up off to select LF CR as the delimiter orientation NOTE The address switch is updated only on power up Connect the CBM IEEE cable to the DRC8 IEEE interface Turn on the PET and enter the program below including line numbers by pressing the return key after every line After entering the program type RUN and press the return key The display will read ENTER set the set point to 130 0 the remote gain value to 5 the remote reset value to A and toggle the flag to external control type in A130B5CAD and press return The display will then return those values just set in and return for a new input 10 AS 20 OPEN1 6 30 PRINT 1 ASCHRS 13 40 CLOSEL 50 OPEN2 6 60 INPUT 2 G R P S T 70 CLOSE2 80 PRINT 90 PRINT 100 PRINT GAIN G 110 PRINT RESET R 120 PRINT PANEL eps 130 PRINT SET POINT 55 140 PRINT TEMPERATURE T 150 GOTO10 3 9 3 2 85 Set the
50. ing order upon receipt To confirm this the instrument should be inspected visual ly for obvious damage upon receipt and tested electrically by use to detect any concealed damage Be sure to inventory all components supplied before dis carding any shipping materials If there is damage to the instrument in tran sit be sure to file appropriate claims with the carrier and or insurance company Please advise the company of such filings In case of parts short ages please advise the company The standard Lake Shore Cryotronics warranty is given on the title page 2 3 Power Requirements Before connecting the power cable to line voltage insure that the instru ment is of the proper line voltage and fused accordingly The line voltage and fuse are shown on the rear panel of the instrument The line voltage can be changed by switching line voltage selector switch 52 Figure 6 5 DRC 84C Component Layout located on the main printed circuit board of the unit Nominal permissible line voltage fluctuation is 410 at 50 to 60 Hz 2 4 Grounding Requirements To protect operating personnel the National Electrical Manufacturer s 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 2425 Installation The DRC 84C Thermometer Controller is all solid sta
51. inum resistor the buffered output voltage is 20 times the actual sensor voltage For example if the input voltage from the platinum sensor is 0 0100V then the buffered output voltage would be 0 2000V 2 6 Repackaging for Shipment Before returning an instrument to the factory should repair be neces sary please discuss the malfunction with a factory representative He may be able to suggest several field tests which will preclude returning a satisfac tory instrument to the factory when the malfunction is elsewhere If it is indicated that the fault is in the instrument after these tests the represen tative will provide shipping and labeling instructions for returning it When returning an instrument please attach a tag securely to the instrument 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 a 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 0482 Do not ground shield voltage sense Sasu ee de eee eee A RECOMMENDED SENSOR CABLE Do not ground shield SEG 1 4 5ohm J6 heater element BLACK 0 RO B RECOMMENDED HEATER CABLE Do not groun
52. lel BCD interface TTL com patible Allows remote control of set point gain reset and provides BCD output of temperature in Kelvin and Sensor selected either from front panel or optional SW 10A Model DRC8 IEEE 488 interface Allows remote control of set point gain reset and provides digital output of temperature in Kelvin and Sensor selected either from front panel or optional SW 10A Model DRC8 L A Analog output proportional to Kelvin temperature for use with recorders or other readouts 10mV K at lt 10 ohm output resistance Model KT LA Analog output identical to DRC8 L A except for use when unit is also equipped with DRC8 BCD Model KT BCD Parallel BCD interface identical to DRC8 BCD except for use when unit is also equipped with DRC8 L A Model SW 10A 10 Sensor Selector Switch for use with DRC Thermometer or Controller Pushbutton selection of any one of up to 10 sensors Connects to Sensor B position Sensor selected ts also identified via digital interfaces Dimensions 216mm wide x 102mm high x 330mm deep 8 in x 4 in x 13 in Style L half rack package Model RM 3F Rack ears with handles to mount style L full rack instrument package in standard 3 rack space Model RM 3H Rack mounting hardware to mount either one of two Style L half rack unit s in standard 3 rack space DRC Precision Option Custom programmed read only memory for DRC instruments which improves specified accuracy to 0 1 or be
53. ming 0482 0482 INPUT SET POINT A 000 0 A9 009 0 A8009 6 009 6 A130 130 0 122 3 92 123 9 1239 239 0 50 5 050 5 The and commands each require 1 character following the command The gain and reset values can be seen in Section 3 8 The D code command is used to change from front panel controls to IEEE control or vice versa The D code acts as a flag toggle in that if the unit is under front panel control and the D command is sent to the DRC instrument then it will respond to changes only from the interface If the D command is sent again the instrument returns to front panel control Therefore on odd times for the D command being sent the unit is in remote control and on even times the unit is in front panel control As an example a controller sends the ASCII sequence A130 0B9C5D A is the set point code 130 0 five characters to represent the set point 130 0 K B is the gain code 9 is the setting for resistors 1001 C is the reset code 5 is the setting for resistors 0101 D is the flag to convert controller operation if no other D has been sent through this one switches control from front panel to IEEE The interface looks for one of two input terminators The DRC8 IEEE will return to normal operation when the EOI command is accepted on input The DRC8 IEEE will also look for an input delimiter depending on the position of switch 1 of the address switch The following table shows the input del
54. nc E F Johnson 111 0113 001 E F Johnson 111 0103 001 E F Johnson 111 0103 001 AMP MODII 3 86018 5 mates to JG AMP MODII 3 86018 5 mates to JH Cambion 703 5316 01 04 12 Cambion 703 5324 01 04 12 TRW 50 24B 10 Cambion 703 5314 01 04 12 AMP 87228 5 mates to JA 0482 0482 CIRCUIT DESIGNATION JH JL JM JN CIRCUIT DESIG CR1 CR2 CR3 CR4 CR5 CR6 GR 7 CR8 9 CR10 CR11 CR12 CR13 CR14 CR15 CR16 CR17 CR18 051 052 DS3 DS4 D55 CONNECTORS DESCRIPTION 10 Contact PC Mount To Display Board 16 Contact PC Mount Power Transformer jJ Contact Transistor Mounts on U45 8 Contact PC Mount Heater Output Transformer MFR and PART NO AMP 87228 5 mate to JB AMP 350214 1 mates to 1 480 438 0 Molex 10 17 2032 AMP 350212 1 mates to 1 480 285 0 DIODES TYPE MFR and PART NO Silicon INAOO6 Silicon IN4006 Silicon IN4006 Silicon IN4006 Silicon IN4006 Silicon MR501 Silicon MR501 Silicon MR501 Silicon 743 743 Not Used Silicon INA148 Silicon INA59 Silicon IN459 Silicon MR501 Silicon MR501 Silicon MR501 Silicon MR501 7 Segment LED Hewlett Packard 5082 7651 Least Significant Digit 7 Segment LED 2nd Significant Digit 7 Segment LED 3rd Significant Digit 7 Segment LED Most Significant Digit Pilot Light LED Scale Expand Indicator Hewlett Packard 5082 7651 Hewlett Packard 5082 7651
55. nd the error signal is positive resulting in the inverting gain amplifier output being negative Since the output amplifier is also an inverting amplifier power is applied to the load The amount of power is dependent on the magnitude of the error signal the gain setting and also the magnitude of the integral signal If the combination of the gain and error signal are such that the output of the gain amplifier is more negative than two volts the output amplification will result in full power being delivered to the load For 0482 0482 this condition an integral time is not required and is eliminated by using the comparator U42 The output gain is inverted resulting in a positive signal If this signal is greater than two volts the output of the comparator approaches the negative supply voltage and CR11 is forward biased This in turn causes CR13 to become forward biased so that the integator is effectively removed from the circuit However when the output of the gain amplifier is between zero and a minus two volts the comparator output approaches the positive supply voltage re sulting in CR11 being shut off and R59 and R60 having no effect since pin 2 of amplifier U43 is a virtual ground The integrator will then integrate with a time constant which is proportional to the setting of the potentiometer R62 and the magnitude of the amplifier error signal The output of the gain amplifier is summed with the output of the inte grator to
56. ned in to assure fast response low offset error and high stability Two heater output levels are selectable on the DRC 84C Th HI mode provides up to 25 watts of heater power while the LO mode limits output power to a nominal 10 watts Five options are available with the DRC 80 Series of instruments One option is an analog signal which is proportional to temperature DRC8 L A This option has a sensitivity of 10 mV K A second option is a ten position switch SW 10A for multiple sensor readout This switch is a separate half rack box which plugs into the Sensor B position of the DRC 84C The sensor selected is also identified via digital interface of the DRC 84C if present 0482 3 0482 Another option is a custom cut PROM DRC Precision Option which corresponds to the calibration curve of the customer s DT 500 Series sensor A combination of a calibration and custom cut PROM will increase display accuracy to nearly 1 Kelvin over the calibrated range Please note that any sensor may be used with this option i e the customer is not re stricted to the DRC Series sensors There are two programming options available each will control the set point the gain and reset as well as output the displayed temperature and sensor selected from the SW 10A The DRC8 BCD I O is in a parallel BCD format while the DRC8 IEEE is in the popular IEEE 488 format The DRC 80 Series is designed around a 3870 microprocessor and asso ciated supp
57. nsor Select TYPE Mt Mt Mt Mt Mt Mt to Reset Switch Mt F Mt Mt Mt Mt Mt Mt Mt Mt Mt Mt Mt Mt Mt nj rr trj Hj rrj Ud o nj Hj oU nj rr MFR amp PART NO Centralab P10074 Switchcraft C46206LFR Allen Bradley 21M562 Allen Bradley 21M563 Allen Bradley 21M563 Centralab PO25026 Centralab 25025 Centralab PO25025 Centralab PO25025 Centralab PO25025 0482 6 2 DRC 84C BCD L A and IEEE Components List CAPACITORS CIRCUIT DESIGNATION VALUE RATING TYPE C56 4 033 WE 100V Mylar C57 68 uf 100V Poly C58 68 uf 100V Poly C59 68 uf 100V Poly C200 ouf 100V Poly C201 100V Poly C202 EET 100V Poly C203 E 100V Poly C204 EIE 100V Poly C205 100 1 206 od uf 100 1 C207 1 uf 100V Poly C208 18 uf 500V Mica D C210 1 u 100V Poly 6211 Ave 100V Poly CONNECTORS CIRCUIT DESIGNATION DESCRIPTION MFR and PART NO J4 BCD option 50 pin Connector T amp B Ansley 609 5016 Mates with T amp B Ansley 609 5030 J4 IEEE option 24 pin Connector AMP 552791 1 Mates with IEEE cable connector JD IEEE option S N 4136 16 pin IC Socket Cambion or lower IEEE Interface 703 5316 01 04 12 Connection JD IEEE option S N 4137 24 pin IC Socket Cambion or higher IEEE Interface 703 5324 01 04 12 Connection JF 14 pin IC Socket Cambion Gain Reset Control 703 5314 01 04 12 ab
58. nsor and DRC Precision 0 1K or better depending on calibration range Platinum RTD Conforms to DIN 43760 tolerances 0 1K See Lake Shore PT 100 Technical Data for details Calibrated Sensor and DRC Precision improves accuracy to 0 01K depending on range Temperature Control Set Point Digital thumbwheel selection directly in Kelvin Celsius or Celsius as determined by front panel switch Remotely settable in Kelvin with BCD or IEEE 488 Option Set Point Resolution 0 1K or 0 1 C Typical Controllability 0 1K or better in a properly designed system Control Mode Proportional gain and integral reset Set via front panel or remotely with BCD or IEEE 488 option Heater Output HI 0 25 watts 1A max 25V max LO 0 10 watts nominal 1A max or 12V max Isolated output 25 ohm heater is recommended Control Sensor Selected by front panel pushbutton independent of Display Sensor within either section General Monitor Output Buffered output of 1X Display Sensor voltage silicon and 5X Display Sensor voltage platinum Additional outputs listed below as options Dimensions Weight 432mm wide x 102mm high x 330mm deep 17 in x 4 in x 13 in Style L full rack package Net weight 8 4 kg 18 5 Ibs Power 90 110 105 125 or 210 250VAC 50 or 60Hz 75 watts Accessories Supplied Mating connectors for sensor inputs and monitors instruction manual Options and Accessories Available Model DRC8 BCD Paral
59. nstrument is troubleshooted Some checks that could be made are 1 Open or shorted sensor or heater leads especially in an area of frequent disassembly 2 Leakage paths between heater and sensor leads that induce electrical feedback in addition to thermal feedback If the malfunction points toward the instrument more detailed tests should be made 5 4 Instrument Calibration The DRC 84C has been factory calibrated If a recalibration is needed the following procedure should be followed Please refer to the component layout for the DRC 84C Figure 6 5 for the following discussion 5 4 1 Current Sources a Current Source Diode Sensor A A precision resistor of not less than 01 tolerance should be connected across pins A and B Figure 2 1 of the diode A Sensor socket A high input impedance voltmeter connected across the precision resistor should measure a voltage equal to 10 micro amperes times the value of the resistor For example a 100K ohm 01 resistor should read 1 0000 volts within 100 uvolts if recalibration is needed the voltage across the 100K re sistor can be adjusted by varying resistor R12 47 _ b Current Source Diode Sensor B The above procedure can be followed with the diode B Sensor socket should be varied for this adjustment C Current Source Platinum Sensor A A 100 ohm precision resistor of not less than 0 1 tolerance should be connected across pins A and B Figure 2 1 of the
60. o control Tri State 8 line to 4 line multiplexers 7415257 controlled by a decoder demultiplexer 74139 to input the information needed The second of the 2 ports handles the input of data and manipulation of display data The CPU outputs the set point information through one of its 1 0 ports as well The DRC 84C software is discussed in detail in Section 4 3 4 4 3 4 Software Refer to Figure 4 2 as an aid in the following discussion The flow chart gives the major steps of the program When the instrument is turned on the program does a power on reset and starts the program at the beginning At this point the program initializes internal registers to be used in the program The program first checks for an A D converter overrange and then inputs multiplexed A D information when the A D tells it there is fresh data ready the program loops until the A D information is ready The program then verifies that there are no illegal characters that were input and stores the reading After the first cycle a calculation is done with each A D reading The program then inputs display sensor information There is one stan dard curve for the instrument and there are a maximum of twelve additional 4l curves for each type of sensor There can be a calibrated curve for Sensor A B and ten different switch positions generated by the SW 10A The program determines the type of sensor input and what curve to use for that sensor Once the curve is d
61. of the controller the voltage stored on the integrator and the magnitude of the error signal 4 3 6 Digital Display Board Please refer to Figure 6 6 Display Board Schematic and Figure 6 7 Display Board Component Layout as an aid in the following discussion The display board receives its data in a bit parallel digit serial form The information is latched into the display decoder driver U101 which drives the display digits DS1 4 Control of the decimal point is carried out by the BCD decimal decoder driver U102 This driver receives its information directly from the microprocessor Front panel pushbutton information is displayed by pilot light LED s DS5 12 and are explained by information contained on the display glass 45 This Page Intentionally Left Blank 0482 SECTION V Calibration and Troubleshooting Sat Introduction This section contains the instructions for calibrating and trouble shooting the DRC 84C instrument Jel Test Equipment A high input impedance digital voltmeter and oscilloscope a 25 ohm 25 watt resistor to simulate a heater element and a precision resistor connected to simulate the diode wired according to Figure 2 1 c are normally sufficient to test and calibrate the DRC 84C instrument 55 3 General Remarks On installation one of the major problems is an improperly connect ed temperature sensing diode It is advised that other portions of the cryogenic system be tested before the i
62. ort circuits The DRC curve is stored in a PROM which can handle up to 32 break points per curve The data consists of a table of temperature and voltage associated with each break point These straight line segments can generate the DRC curve to an accuracy of better than 0 1 Kelvin over the entire temperature range 4 0 400K The DRC diodes match this curve to 0 5K at Helium and Nitrogen temperatures and to 1 0K at room temperature 1 3 Major Assemblies Supplied The DRC 84C includes as standard equipment in addition to the digital thermometer controller the following A Operating and Servicing Manual B Four five Pin Plugs for Temperature Sensor Cables C One seven Pin Plug for Monitor of Sensor Output Voltage and the DRC8 L A option Model DT 500 Series silicon diodes or platinum thermometers are not supplied as part of the DRC 84C instrument Complete Specifications Accessory Equipment and Customs Options are listed in the front of the Manual 1 4 Ordering of Replacement or Additional Sensors Two different sensor configurations are available for use with the Model DRC 80 Series instruments These are the DT 500 DRC and the DT 500CU DRC 36 sensors Their description is included elsewhere in this manual All sensor configurations are available if the diode is calibrated and a special PROM is cut More than one curve presently exists which can be used with the DRC 80 Series instruments If additional sensors are ordered for
63. ounting plate attached and secure it in Interface opening J4 after any existing plate is removed Place 14 pin header connector into board connector JF noting Pin 1 to Pin l alignment Note Ribbon cable and 14 pin header are only present for BCD option 4 If set point is to be controlled externally main circuit board jumpers JMPl and JMP2 must be cut 5 Connect black or green and white wires of BCD L A board to 7 pin rear panel connector J3 White goes to pin C and black or green goes to pin D 6 Replace instrument cover Installation of DRC IEEE Option Board The installation of the DRC IEEE option board can be done as follows 1 Remove instrument cover 2 Remove blank plate covering J4 connector on rear panel 3 Install 14 pin header into connector JF Install 24 pin header into JD Note pin 1 to pin 1 correlation See Figure 6 5 DRC 84C Component Layout for connector locations 4 Place option board in J4 opening and secure in place with screws provided 5 Replace instrument cover 3 12 Rack Mounting the DRC 84C The DRC 84C can be rack mounted with an RM 3F rack mounting kit A typical full rack mount unit can be seen in Figure 3 4 Lake Shore Cryotmnios Inc TENPERACURE CONTROLLER MODEL BRC 252 FIGURE 3 4 Typical Rack Mounted Unit 0482 36 3 13 Error Conditions The following error conditions can occur with the DRC 84C Display LO 1 LO 2 HI 1 HI 2
64. platinum A Sensor socket A high input impedance voltmeter connected across the precision resistor should measure a vol tage equal to 0 5 milli amperes times the value of the resistor For example 100 ohm 10 1 resistor should read 50 millivolts within 5 uvolts If recalibration is needed the voltage across the 100 ohm resistor can be adjusted by varying resistor R3 d Current Source Platinum Sensor B The above procedure can be followed with the platinum B Sensor socket R5 should be varied for this adjustment 5 4 2 A D Converter To adjust the A D converter a voltage needs to be applied across pins E and D Figure 2 1 of the display sensor connector for the diode A A variable 200K resistor hooked up as in Fig 2 1 a or precision vol tage source in place of the diode are ideal ways to generate this voltage If a resistor is used it should be varied until one of the breakpoint voltages indicated in the Voltage Temperature Characteristic Table is generated A high impedance voltmeter must be used for this adjustment After an appropriate voltage is obtained the display should be calibra ted by adjusting trimpot R38 until the display reads the correct tempera ture If a precision voltage source is used a breakpoint voltage should be dialed in and the display should be calibrated as above A breakpoint temperature above 40K should be used since the voltage sensitivity with temperature is lower at the higher temperatures 2 5 mV
65. pril 1982 115 IV Lo CO CO 2 GLO Uy Co Ep Section Table of Contents General Information Lek HE Ht FUN Ins al 2 2 2 3 2 4 245 2 6 Introduction Description Major Assemblies Supplied Ordering of Replacement or Additional Sensors tallation Introduction Initial Inspection Power Requirements Grounding Requirements Installation Repackaging for Shipment Operating Instructions 3 1 NO XO XO WD CO Co CO Co CO CO Lo Hi IS F2 xO 0 y DAU e Uy Introduction Controls Indicators Connectors Temperature Readout Analog Control Analog Output of Temperature Standard DT 500 DRC and DT 500CU DRC 36 Curves The 10 Sensor Selector Switch Remote Parallel BCD Input Output Option IEEE Interface Option General IEEE Specifications and Operation Specific Operation of the DRC8 IEEE Interface Sample Programming Installation of DRC BCD L A Option Board Installation of DRC IEEE Option Board Rack Mounting the DRC 84C Error Conditions Theory of Operation 4 1 YY FS Co CO Co CO Co Introduction General Description Detailed Description Power Supplies Precision Current Sources and Input Switching A D Converter and Microprocessor Hardware Software Analog Control and Set Point Digital Display Board Page UD oy O Ui Ui un 0482 Table of Contents cont d
66. put voltage is located on the monitor connector Key 17 of Figure 3 2 See Section 3 10 for installation notes on DRC 8 L A 3 6 Standard DT 500 DRC and DT 500CU DRC 36 Curves The standard DT 500 DRC and DT 500CU DRC 36 curve is explained in Section 3 3 The Tables include a list of PROM sensor voltages and break points used in the linearization of the DRC curve to arrive at the correct temperature readout 3x7 The 10 Sensor Selector Switch The 10 Sensor Selector Switch includes an umbilical which ties to the DRC 84C main printed circuit board via a 16 pin ribbon cable header which plugs into internal socket JC see Figure 6 5 DRC 84C Component Layout and a cable to connect the selected sensor leads to the DRC 84C Sensor Plug B is either Key 15 or Key 16 of Figure 3 2 The SW 10A is supplied with an 18 cable which is shielded and has male 5 pin amphenol connectors at each end This cable connects between se 14 411 of the SW 10A and one of the B sensor plugs of the DRC 84C Sensors are connected to the SW 10A via printed circuit edge J10 A 36 pin edge card connector and hood has been supplied with the SW 10A Connectors to this edge J10 are given in Table 3 5 3 8 Remote Parallel BCD Input Output Option The BCD option consists of a 16 bit parallel output of temperature along with a scale expand bit to indicate decimal point a 15 bit parallel input of set point in Kelvin degrees or Celsius depending on switch posi tion
67. res dual sensor input which enables two sensors to be used concurrently Either sensor can be selected to be the control sensor and or the temperature display sensor both sensors must be of the same type silicon diodes or platinum RTD s Thus control can be centered at one point in a system and temperature monitored elsewhere This permits for instance maintenance of temperature at a particular cold stage and simultaneous measurement of sample temperature Selection of input section as well as display and control sensor is made via front panel push buttons 0482 NEN A 4 digit display clearly and unambiguously shows the temperature directly in Kelvin or Celsius with O 1 degree resolution At low temperatures under 30K a SCALE EXPAND mode increases resolution to 0 01K for monitoring trends and other relative temperature measurements Absolute accuracy at low temperatures is 0 5K in either mode The silicon diode input section of the DRC 84C is designed to use proven Lake Shore DT 500 Series DRC curve silicon diode Sensors which provide measurement accuracy to 0 5 at low temperatures Accuracy can be increased to better than 0 1K through use of an individually calibrated sensor and the DRC Precision option to store the calibration Any DT 500 Sensor can be utilized in the latter case Lake Shore PT 100 Series 100 ohm Platinum RTD s are the ideal Sensors for the platinum section The standard response curve is based on 0 1 interc
68. scussion covers the general operation of the IEEE 488 interface For a more detailed description of signal level and interaction refer to the IEEE Std 488 1978 publication IEEE Standard Digital Interface for Programmable Instrumentation All instruments on the interface bus must be able to perform the inter face functions of TALKER LISTENER or CONTROLLER A TALKER transmits data onto the bus to other devices A LISTENER receives data from other devices through the bus Some devices perform both functions The CONTROLLER desig nates to the devices on the bus which function to perform The IEEE works on a party line basis with all devices on the bus con nected in parallel All the active circuitry of the bus is contained within the individual devices with the cable connecting all the devices in parallel to allow the transfer of data between all devices on the bus There are 16 signal lines contained on the bus A 8 Data Lines B 3 Byte Transfer Control Lines C 5 General Interface Management Lines The data lines consist of 8 signal lines that carry data in a bit parallel byte serial format These lines carry universal commands addresses program data measurement data and status to all the devices on the bus The controller designates the functions of the units on the bus by setting the ATN line low true and sending talk or listen addresses on the DATA lines When the ATN line is low all devices listen to the DATA lines When the
69. shooting Notes DRC 84C Power Supply DRC 84C Current Source Input Connections Switching DRC 84C Microprocessor Section DRC 84C Analog Output Section DRC 84C Component Layout DRC 84C Display Board DRC 84C Display Board Component Layout DRC 84C BCD L A Option DRC 84C BCD L A Option Component Layout DRC 84C IEEE Option DRC 84C IEEE Option Component Layout 11 li 15 16 28 17 35 20 21 22 38 43 49 49 52 53 67 69 71 73 75 77 77 79 79 81 81 0482 0482 Specifications DRC 84C Temperature Controller Input Temperature Range 1 4 to 330K with standard silicon diode DRC Sensor to 380K with other silicon Sensors 30 to 800K with platinum sensor Silicon diodes cannot be exposed to temperatures above their useful range Sensors order separately Silicon Diode DT 500 DRC DT 500CU DRC 36 or any calibrated DT 500 Series Diode with DRC Precision Option See below for proper response curve Platinum RTD PT 101 PT 102 PT 103 or any other 100 ohm 0 00385 C sensor See response curve details below Sensor Input Two section input silicon diode and platinum RTD Front panel switch selects either section Each section accommodates two sensors with 4 terminal input for each sensor Front panel switches enable independent selection of either sensor within each section as display and or control sensor Display control sensors cannot be mixed between silicon and platinum sections S
70. t706 A red706 G R P S T prtG prtR prtPS prts prtT gtol A O 3 9 3 5 HP 9835A Set the address switch to 6 by putting address switches 6 and 7 down 8 5 and 4 up Make sure switches 2 and 3 are up off to allow the DRC8 IEEE to both talk and listen Set switch 1 down on to select CR LF as the delimiter orientation NOTE The address switch is updated only on power up Connect the DRC8 IEEE to the 98034A interface of the HP 35A Turn on the unit and enter the program below by pressing the STORE key after each line is typed Press the RUN key The display will read ENTER To set the set point to 130 0 the remote gain value to 5 the remote reset value to A and toggle the flag to external control type Al30B5CAD and press the CONT key The display will read the values just set in and return for a new input 10 INPUT ENTER SAS 20 OUTPUT706 A 30 ENTER706 G R P S T 40 PRINT 50 PRINT 60 PRINT GAIN 65 70 PRINT RESET RS 80 PRINT PANEL pS 90 PRINT SETPOINT 95 100 PRINT TEMPERATURE s TS 110 0 010 3 10 Installation of DRC BCD L A Option Board The installation of the DRC BCD L A option board can be done as follows 1 Remove instrument cover 2 Insert the BCD L A option board into instrument JE connector the instrument has its edge card connector configured such that the option board can only be inserted in one way 0482 3 Take 50 pin ribbon connector with m
71. te and does not generate significant heat It may therefore be rack mounted in close proximity to other equipment in dead air spaces The heat from such adjacent equipment should not subject the controller to an ambient temperature 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 in the case of the DRC 84C controllers are shown in Figure 2 1 a and b The use of a four wire diode or resistor connections is highly recommended to avoid introducing lead IR drops which will occur if the alternate two lead sensor cable connection is used For example for a two lead connection with diodes every 25 ohms of cable resistance corresponds to a 1K error above 30 Kelvin The alternate wiring scheme shown in Figure 2 1 c may be used for the diode in less critical applications where lead resistance can be kept small Because of the low resistance of platinum resistance thermometers the four lead cable connections must be used to obtain system accuracy The indi cated shielding connections are the recommended standard practice to avoid ground loops Figure 2 1 d shows the monitor connections for the analog output of sensor voltage 0 2 5V for diodes 0 3 0V for platinum Pin A and optional linear analog output of temperature 0 8V Pin C In the case of the plat
72. tter over a given calibration range Any DT 500 Series Silicon Diode Sensor or PT 100 Series Platinum RTD can be utilized Requires that an appropriate calibration be purchased for the Sensor Specify Sensor input position A or B or 1 10 SW 10A to assure proper location of calibration within PROM First calibration stored Subsequent Calibrations stored in same PROM Model DT 500 DRC Silicon Diode Temperature Sensor 1 5mm diameter x 4 1 long Specify response Curve Model DT 500CU DRC 36 Silicon Diode Temperature Sensor 8mm diameter x 3 3mm thick with mounting hole Specify response curve Model PT 101 Platinum RTD 3 1mm diameter x 30 5 mm long Model PT 102 Platinum RTD 2 0mm diameter x 20 3mm long Model PT 103 Platinum RTD 1 8mm diameter x 12 1mm long Specifications subject to change FIGURE 1 1 Model DRC 84C Digital Cryogenic Thermometer Controller 0482 SECTION I General Information 1 1 Introduction The following is a description of the DRC 84C Cryogenic Digital Thermometer Controller The DRC 80 Series of instruments is designed to be used with the Model DT 500 DRC and DT 500CU DRC 36 silicon diode sensors manufactured by Lake Shore Cryotronics Inc Several different diode sensor curves are designed for use with this instrument When ordering replacement sensors care must be taken to assure that the correct sensor curve is specified Multiple curves are needed so
73. uld be used in the diode type only The linearity of the converter is the same for diodes and platinum If this method is used for the platinum type the high stability instrumentation amplifiers of the platinum input may be damaged Note An A D that is in calibration is vital to the accuracy of this method of calibration 5 4 4 Output Buffer With a constant voltage fed into the instrument as in the A D converter calibration place the voltmeter between Pins A and B of 7 pin rear panel connector J3 This voltage should be equal to the input volt age R20 is varied to obtain the proper buffered signal 5 4 5 DRC L A Option if present The output of the DRC L A option outputs 10mV K relative to display temperature In other words 100 0 K on the display corresponds to a 1 0000V output between Pins C and D of monitor connector J3 To recali brate the option two adjustments need to be made With a low temperature on the display e g 22 0 K adjust the offset adjustment potentiometer R89 see Figure 6 9 DRC 80C BCD L A Option Component Layout until the output corresponds to 10 mV K Then take the display to a higher tempera ture e g 300 KY Adjustment of gain potentiometer R88 will bring the output to 10 mV K The procedure may need one more iteration that is go to the low temperature on the display adjust the offset then go to high temperature display and adjust the gain again DoD Instrument Tests The first check to
74. ulse is required to make one count 50 000 pulses per second would allow for 0482 0482 1 2 readings per second The digital signal is output in a bit parallel byte serial form The A D converter output is multiplexed by U27 and U28 and input by the microprocessor In addition to the A D information the microprocessor inputs the front panel control information external switch position set point and optional inputs BCD or IEEE and outputs display information and set point voltage The microprocessor unit MPU used in the DRC 84C is a 38P70 which utilizes a piggy back memory architecture A 3870up was originally a mask only part with the user tied to one program form when the part was fabri cated The piggy back variation of the part allows for variable memory space between 8K and 64K of PROM to be placed on top of the up This allows all lines that were used for addresses and data to be used for input output The microprocessor unit has an internal RAM scratchpad memory used for programming The unit derives its internal clock from resistor R23 and C18 if needed The MPU has four 4 8 bit bi directional ports used for communication to and from the processor Two of these ports Ports O and 5 are used for internal control of the instrument A D input BCD temperature output set point voltage output etc The remaining two ports Ports 1 and 4 are used for option access IEEE 488 The CPU uses one of its I O ports t
75. use with your instrument you must be certain to order the correct curve so that your instrument will have its stated accuracy The proper curve may be determined in one of the following ways A Specify the sensor serial number that is currently being used with the instrument serial number is found on the end of the plastic box in which the sensor was received Specify the serial number of your instrument Our records will indicate with which sensor the instrument is compatible Remove the top of your instrument and observe the indicator on the curve PROM The fourth way is to measure the diode voltage at 4 2K and give this value to Lake Shore Cryotronics Inc when re ordering sensors Lake Shore PT 100 ohm Platinum RTD s are available for the platinum Section These thermometers have a 0 1 interchangeability at O C and a temperature coefficient 0 to 100 C of 0 00385 0482 i 0482 SECTION II Installation Zed Introduction This section contains information and instructions necessary for the installation and shipping of the model DRC 84C Cryogenic Temperature Indicator and Controller Included are initial inspection instructions power and grounding requirements installation information and instructions for repack aging for shipment 252 Initial Inspection This instrument was electrically and mechanically inspected prior to shipment It should be free from mechanical damages and in perfect work
76. ut another set point until the error is cor rected The program then calculates the break point voltage in much the same way it calculates the temperature The program determines which is the con trol sensor and its appropriate curve It then calculates the set point volt age using the following equation Top Vap 42 0482 Initialize System Check tor luput Overrange Is there an Overrange Yos Load in temperature storage area Input A D ril Is it a valid Reading Do you need any more A D Readings Yo Input sensor type display sensor and switch info Determine Volrage Temperature Table ro be used Find Breakpoint Determine slope dT dV for that Breakpoint V Find AD Multiply bv dT Add Tap No Is type Platinum Yes Yes Load LO 1 into temperature storage area Input position of C C K Switch Is swirch in C position Subtract 272 157 from the Kelvin Temp to gec rhe Celsius Temp Is the result negative Change storage register ro indicate negarive temperature Change storage register R to indicate Make sure storage register R6 shows no sign and Check Scale Expand Bit Is Scale Expand in Yes Round to che nearest tenth of a degree Is Temperature lt 100
77. wes 0000000 8 Jo A TOA are Zi e e s 090000007 8 e 00000000000000000000 9 amp U201 J000000000000000000 rer ge ane 4 t lt ssp og ms T E M C207 mo NC U210 0211 U204 000000 000000 2300000000 E 17 gt 000000 0009009 00000000 1 p 73509 EJ U212 U213 21 218 000000 000000 00000000 a NOTES 15V 204 205 4 1 Pc 5 ORT DESIGNATION FOR MK3871 ARE 40 47 50 57 P 13 2 0202 PIN1 to 000000 PINS to GND 3 JD IS 24 PIN DIP SOCKET JD IS A 16 PIN DIP SOCKET JF IS 14 PIN DIP SOCKET 4 U205 _ FIGURE 6 11 DRC 84C IEEE Option IS GND ks pr 14 IS 5v Component Layout JD 21 5 LO OV ON PORT 57 SELECTS TIMER CLOCK PI EFP roe HI 5V ON PORT 57 SELECTS PORT 56 CLOCK FIGURE 6 10 DRC 84C IEEE Option 0482
78. witch 7 selects the type of sensor selected platinum or silicon 510 then routes the appropriate voltage and type information to switches 8 and 59 Switch 59 selects which sensor A or B will be the display sensor This switch takes the appropriate sensor voltage and feeds it to the A D converter as well as informing the microprocessor of its position Switch S8 selects which switch is the control sensor This switch takes the voltage and feeds it to an input buffer amplifier to be used as the control voltage This switch also identifies its position to the microprocessor Switch S10 identifies whether or not the scale expand is in use Switch S6 selects the power setting and will be explained in detail in the power amplifier section Section 4 3 5 Buffer Amplifier U19 gives a buffered output of the display sensor which is available at the monitor plug This amplifier can have an offset voltage as high as 0 5 mV This is adjusted to zero with trim potentio meter R20 4 3 3 A D Converter and Microprocessor Hardware Please refer to Figure 6 3 DRC 84C Schematic 3 for the following discussion The Analog to Digital converter consists of a precision 4 digit IC pair 8052A 7103A U31 and U32 that produces a multiplexed BCD output that is accurate to 1 count over the entire 40 000 count range The 7103A U31 runs on a 50K Hz clock cycle generated by U33 This clock frequency allows for one reading every 8 seconds since one clock p
79. y form The program then loops back to begin the cycle over again 4 3 5 Analog Control and Set Point Refer to Figure 6 4 Schematic 4 for the following discussion The digital set point voltage information is output in digit serial bit parallel form The data is then latched by four quad latches U34 through U37 using a data valid signal from U24 The data latched into the quad latches is in a complementary hexadecimal form This data is converted by a D A converter for a negative analog voltage silicon or positive platinum set point The set point is then compared to the opposite polarity sensor voltage by amplifier U40 and its associated circuitry If the two signals are not equal in magnitude this error signal is amplified with the amplification controlled by the gain con trol potentiometer on the front panel In order to understand the analog control circuitry three dif ferent cases should be discussed The examples will be covered for the diode The examples can be applied to the platinum sensor keeping in mind the platinum sensor has the opposite temperature coefficient of the diode It should be remembered that in the case of the diode sensor voltage decreases with increasing temperature i e the diode is a nega tive temperature coefficient sensor For the first case assume that the sample temperature is less than the decimal set point temperature Therefore the sensor voltage is greater than the set point voltage a

Model DRC-84C - Lake Shore Cryotronics, Inc.

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