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1. 4 Select the Model 2750 RATIO function press SHIFT then RATIO 5 Setthe calibrator output to 1 00000V DC and allow the reading to settle 6 Verify that the ratio reading is between 0 9999926 and 1 000074 7 Press OPEN to open Channel 1 Figure 1 18 Connections for Model 7700 ratio and average verification CH1 Model 7700 DC Voltage Calibrator eki Output IL HI 4 C APO tc Output Q LO CH11 Note Use shielded cables to minimize noise 1 36 Performance Verification Model 2750 Multimeter Switch System Service Manual Calibration 2 2 Calibration Model 2750 Multimeter Switch System Service Manual Introduction Use the procedures in this section to calibrate the Model 2750 Calibration procedures include Comprehensive calibration Usually the only calibration required in the field Manufacturing calibration Usually only performed at the factory unless the unit has been repaired Model 7700 calibration Covers calibration procedures specific to Model 7700 cards WARNING The information in this section is intended only for qualified service personnel Do not attempt these
2. Ly i Je ERE A OHMS 4 WIRE HLHLHLHL LL d d 17 CH18 CH19 CH20 HLHLE CH21 CH22 Z CHIT CH12 CHI3 CH14 CH15 CH16 L CH22 Fuse CH21 Fuse 92ueu9jureyw UNOY 3 6 Routine Maintenance Model 2750 Multimeter Switch System Service Manual 5 De solder the blown CH21 or CH22 fuse as required taking care not to damage the circuit board or spread solder flux around the board CAUTION Do not use a fuse with a higher current rating than specified or module damage may occur 6 Install a new 3A 250V fast blow fuse Keithley part number FU 107 1 7 Solder the new fuse in place using organic OA based flux solder again taking care not to damage the circuit board or spread solder flux around the board 8 Carefully clean the repaired area of the circuit board with a foam tipped swab or brush dipped in pure water then blow dry the board with dry nitrogen gas Allow the board to dry for several hours in a 50 C low humidity environment before use 9 Reinstall the circuit board into the plastic housing then close the top cover Replacing non volatile RAM battery The Model 2750 has a three year lithium battery for non volatile RAM Use the procedure
3. ge 4 24 Troubleshooting Model 2750 Multimeter Switch System Service Manual Disassembly E 5 2 Disassembly Model 2750 Multimeter Switch System Service Manual Introduction This section explains how to handle clean and disassemble the Model 2750 Disassembly drawings are located at the end of this section Handling and cleaning To avoid contaminating PC board traces with body oil or other foreign matter avoid touching the PC board traces while you are repairing the instrument Some circuit board areas especially those under the motherboard shield have high impedance devices or sen sitive circuitry where contamination could cause degraded performance Handling PC boards Observe the following precautions when handling PC boards Wear cotton gloves Only handle PC boards by the edges and shields Do not touch any board traces or components not associated with repair Do not touch areas adjacent to electrical contacts Use dry nitrogen gas to clean dust off PC boards Solder repairs Observe the following precautions when soldering a circuit board Use an OA based organic activated flux and take care not to spread the flux to other areas of the circuit board Remove the flux from the work area when you have finished the repair by using pure water with clean foam tipped swabs or a clean soft brush Once you have removed the flux swab only the repair area with methanol then blo
4. Model 2750 Multimeter Switch System Service Manual Table B 5 continued Calibration errors Error Number Error Message 4461 10 vac noise error 462 100 vac zero error 463 100 vac full scale error 464 750 vac zero error 465 750 vac full scale error 466 750 vac noise error 467 Post filter offset error 468 1 aac zero error 469 1 aac full scale error 470 3 aac zero error 471 3 aac full scale error 472 Input time constant error 473 Frequency gain error 474 100 Ohm Ioff Ocomp FS error 475 10K Ohm Ioff Ocomp FS error 476 Temperature Cold Cal error 477 Analog output zero error 478 Analog output pos gain error 479 Analog output neg gain error 480 Ik 4 w dckt Ioff zero error 481 Ik 4 w dckt Ion zero error 482 Ik 4 w dckt Ioff full scale error 483 Ik 4 w dckt Ion full scale error 484 100 4 w dckt Ioff zero error 485 100 4 w dckt Ion zero error 486 100 4 w ocomp Ion zero error 487 100 4 w ocomp Ion full scale error Calibration Reference B 23 Sa 3 e t oO E e oO B 24 Calibration Reference
5. 5 1 26 Performance Verification Model 2750 Multimeter Switch System Service Manual 5 Source 1A and full scale AC currents as summarized in Table 1 13 and verify that the readings are within stated limits 6 Press the OPEN key to open Channel 21 Table 1 13 Plug in module ACI limits ACV Range Applied AC Voltage Reading Limits 1kHz 1 year 18 C to 28 C 1A 1 000000A 0 99860 to 1 00140A 3A 3 00000A 2 9817 to 3 0183A If the Fluke 5725A amplifier is not available apply 2 2A from the calibrator Reading limits for 2 2A are 2 1949 to 2 2051A Verifying normal resistance Check normal resistance by connecting accurate resistance values to the Model 7700 and verify that its resistance readings are within the specified limits CAUTION not apply more than 300V between the 7700 plug in module INPUT or SENSE H and L terminal or between any adjacent chan nels or instrument damage could occur Follow these steps to verify normal resistance accuracy 1 Using shielded Teflon or equivalent cables in a 4 wire configuration connect the Model 7700 CH1 H and L INPUT terminals and CH11 H and L SENSE terminals to the calibrator as shown in Figure 1 13 Install the Model 7700 in Slot 1 of the Model 2750 then turn on the power and allow the unit to warm up for two hours before proceeding Be sure the front panel INPUTS switch is set to the REAR position Set the calibrator for 4 wire
6. Model 2750 Front Panel Sense Sense LO Note Use low thermal cables to minimize noise 2 Setthe calibrator for 4 wire resistance with external sense on 3 Select the Model 2750 4 wire resistance function by pressing the 4 key then choose the SLOW integration rate with the RATE key 4 Select the Model 2750 dry circuit resistance function by pressing SHIFT then DRYCKT 5 Setthe Model 2750 for the 1O range and make sure the FILTER is on Enable OCOMP offset compensated ohms by pressing SHIFT then OCOMP Use OCOMP for 10 109 1000 and 1kQ range verification Enable line sync ON by pressing SHIFT then LSYNC NOTE Maximum reading rate for the range is two readings per second 6 Recalculate reading limits based on actual calibrator resistance values 7 Source the nominal full scale resistance values for the 1Q 1kQ ranges summarized in Table 1 7 and verify that the readings are within calculated limits N 1 e lt 2 5 1 18 Performance Verification Model 2750 Multimeter Switch System Service Manual Table 1 7 Limits for Model 2750 dry resistance verification Q Range 1Q 10Q 100 2 1kQ Nominal Nominal Reading Limits Resistance 1 year 18 C to 28 C Recalculated Limits 10 0 999860 to 1 000140Q to Q 10Q 9 99860 to 10 00140Q to Q 1000 99 9820 to 100 0180Q to Q 1kQ 0 999510 to 1 000490
7. lt Model 2750 Multimeter Switch System Service Manual 5 6 Disassembly Power module removal Perform the following steps to remove the power module Disconnect the wires going to the power transformer Remove the POWER switch rod 3 Disconnect the power module s ground wire This green and yellow wire connects to a threaded stud on the chassis with a kep nut 4 Squeeze the latches on either side of the power module while pushing the module from the access hole Instrument reassembly Reassemble the instrument by reversing the previous disassembly procedures Make sure that all parts are properly seated and secured and that all connections are properly made WARNING To ensure continued protection against electrical shock verify that power line ground green and yellow wire attached to the power mod ule and the power transformer ground black wire are connected to the chassis When installing the power transformer be sure to recon nect the black ground wire to the mounting stud on the bottom of the chassis Be sure to install all four case screws to assure a good case to chassis ground connection Input terminal wire connections Although it is not necessary to disconnect the input terminal wires use the information in Table 5 1 to connect input terminal wires should you choose to do so Table 5 1 Input terminal wire colors Input Terminal Wire Color INPUT HI INPUT LO SENSE HI SENSE LO AMPS a
8. Signal U129 U129 U129 Gain Range U163 Pin 1 Pin 8 Pin9 U166 10Q S4 OFF OFF ON x100 100Q S4 OFF OFF ON x100 1kQ S4 OFF ON OFF x10 10kQ S4 OFF ON OFF x10 100kQ S4 OFF ON OFF x10 IMQ S4 ON OFF OFF x1 10MQ S4 ON OFF OFF xl 100MQ S4 ON OFF OFF xl Table 4 18 94 signal multiplexing and gain Signal U129 U129 129 Gain Range U163 Pin 1 Pin 8 Pin9 U166 1Q S4 then S7 OFF OFF ON x100 10Q S4 then S7 OFF OFF ON x100 100Q S4 then S7 OFF OFF ON x100 1kQ S4 then S7 OFF ON OFF x10 10kQ S4 then S7 OFF ON OFF x10 100kQ S4 then S7 OFF ON OFF x10 IMQ S4 then S7 ON OFF OFF xl 10MQ S4 then S7 ON OFF OFF xl 100MQ S4 then S7 ON OFF OFF xl Table 4 19 94 dry circuit signal multiplexing and gain Signal U129 U129 U129 Gain Range U163 1 Pin8 Pin9 U166 10 54 then 57 OFF OFF ON x100 10Q S4 then S7 OFF OFF ON x100 1000 84 then 57 OFF OFF ON x100 1kQ S4 then 57 OFF OFF ON x100 Model 2750 Multimeter Switch System Service Manual Troubleshooting 4 23 Figure 4 2 provides a block diagram of the analog circuitry Table 4 20 shows where the various switching devices are located in the block diagram Table 4 20 Switching device locations Switching Devices Analog Circuit Section Figure 4 3 Q101 Q102 Q151 Q150 Q122 Q135 Q159 Q114 Q136 Q109 K101 Q113 Q104 Q108 Q106 Q148 K102 U103 U105 U111 U133 Q123 Q124
9. 10 50 0 1 0 08 65 12uV 110083 140dB 1 Off 1502 6 5 lt 4uV 90dB5 140dB 01 Off 500 400 55 22yV 80dB 001 Off 2500 2000 45 150uV 80dB A 4 Specifications DC MEASUREMENT CHARACTERISTICS DC Volts A D LINEARITY 2 0 ppm of reading 1 0 ppm of range INPUT IMPEDANCE 100mV 10V Ranges Selectable gt 10GQ with 400pF or 10M Q 1 100 1000V Ranges 10M 1 Dry Circuit 100kQ 1 lt LuF INPUT BIAS CURRENT lt 5pA at 23 C COMMON MODE CURRENT lt 500 at 50Hz or 60Hz AUTOZERO ERROR Add 2ppm of range error 5 for 10 minutes and 1 C INPUT PROTECTION 1000V all ranges 300V with plug modules Resistance MAX 4WO LEAD RESISTANCE 80 of range per lead Dry Ckt mode 50 per lead for 10 range 10 of range per lead for 100 1000 and 1 ranges 1kQ per lead for all other ranges OFFSET COMPENSATION Selectable on 4WO 10 100 1000 1 and 10kQ ranges CONTINUITY THRESHOLD Adjustable 1 to 1000 Q INPUT PROTECTION 1000V all Source Inputs 350V Sense Inputs 300V with plug in modules DC Current SHUNT RESISTORS 100mA 3A 0 10 20mA 50 INPUT PROTECTION 3A 250V fuse Thermocouples CONVERSION 175 90 REFERENCE JUNCTION Internal External or Simulated Fixed OPEN CIRCUIT CHECK Selectable per channel Open gt 12kQ EARTH ISOLATION 500V peak gt 10GQ and lt 300pF any terminal to chassis DC Notes 20 overrange except on 1000V and 3
10. C CARD Path to request calibration information from card in slots 1 to 5 COUN lt NRf gt Request number of times card in slot lt NRf gt 1 to 5 has been calibrated DATE lt NRf gt Request card lt NRf gt 1 to 5 calibration date REFTEMP lt NRf gt Returns card ground voltage followed by actual calibrated temp sensor readings comma delimited for card in slot lt NRf gt 1 to 5 Model 2750 Multimeter Switch System Service Manual Calibration Reference 17 CODE CALibration PROTected CODE Purpose To program the calibration code or password so that you can perform the Model 7700 calibration procedures Format cal prot code char string Parameters Up to an 8 character string including letters and numbers Description The CODE command enables the Model 2750 calibration procedures when performing these procedures over the bus This command must be sent to the unit before sending any other Model 7700 calibration com mand The default calibration code is KI002750 NOTE The CODE command should be sent only once before performing calibration Do not send CODE before each calibration step The code parameter must be enclosed in single quotes Example CAL PROT CODE KI002750 Send default code of KI002750 COUNE CALibration PROTected CARD COUNt lt NRf gt Purpose To determine how many times a Model 7700 has been calibrated Format cal prot card coun lt NRf gt lt NRf gt
11. Model 2750 Multimeter Switch System Service Manual Calibration 2 3 Calibration considerations When performing the calibration procedures Make sure that the equipment is properly warmed up and connected to the appro priate input jacks Make sure that the correct front or rear terminals are selected with the INPUTS switch Make sure the calibrator is in OPERATE before you complete each calibration step Always let the source signal settle before calibrating each point Ifan error occurs during calibration the Model 2750 will generate an appropriate error message See Appendix B for more information WARNING Observe the following safety precautions when performing these tests Some of the procedures in this section may expose you to danger ous voltages Use standard safety precautions when such danger ous voltages are encountered to avoid personal injury or death caused by electric shock gt N N zu E E For the front panel terminals only the maximum common mode voltage voltage between INPUT LO and chassis ground is 500V peak Exceeding this value may cause a breakdown in insulation creating a shock hazard For the plug in modules the maximum common mode voltage voltage between any plug in module terminal and chassis ground is listed in the module s specifications Exceeding this value may cause a breakdown in insulation creating a shock hazard e When using
12. ROUT CLOS RCO 102 107 The following command resets the count of slot 1 module channels 1 through 10 ROUT CLOS RCO 0 101 110 Setting count update interval Relay closure counts are updated in temporary RAM every time a channel is closed regardless of how it was closed by an SCPI command front panel control or during a scan These counts are permanently written to the EEPROM on the card only at a user set table time interval which has a factory default of 15 minutes or whenever the counts are queried Valid intervals set in integer number of minutes are between 10 and 1440 min utes 24 hrs Relay closures are counted only when a relay cycles from open to closed state If you send multiple close commands to the same channel without sending an open command only the first closure will be counted EO 5 oO Ea 5 z oO 5 5 fs oO The lower the interval the less chance there is of losing relay counts due to power failures However writing to the EEPROM more often may reduce scanning throughput The higher the interval the less scanning throughput is reduced but more relay counts may be lost in the event of a power failure To set the count update interval send this command ROUTe CLOSe COUNt INTerval lt interval gt For example to set the interval to 30 minutes send this command ROUT CLOS COUN INT 30 3 10 Routine Maintenance Model 2750 Multimeter Switch System Service Manual Rack mountin
13. clist Query count for channels in clist channel list INTerval lt NRf gt Set count update interval in minutes 10 to 1440 INTerval Query count update interval RCOunt clist Reset count for channels in clist Unit must be in manufacturing calibration mode See text below Reading relay closure count To determine the closure count of specific channels send this query via remote ROUTe CLOSe COUNt Gclist Here clist is the summary of channels For example to determine the closure count of channels 1 and 4 of a module in slot 1 the following query would be sent ROUT CLOS COUN 101 104 The following query would determine the closure count of slot 1 module channels 1 through 10 ROUT CLOS COUN 101 110 Model 2750 Multimeter Switch System Service Manual Routine Maintenance 3 9 Resetting relay closure count NOTE The Model 2750 must be in the manufacturing calibration mode to reset the clo sure count To do so press and hold the OPEN key while turning on the power then send the CAL PROT CODE code to unlock calibration default code 002750 After resetting relay counts send CAL PROT LOCK to lock out calibration To reset the relay closure count of specific channels to 0 send this command via remote ROUTe CLOSe RCOunt Gclist Again clist is the summary of channels to be reset For example the following command resets channels 2 and 7 of a module in slot 1 to 0
14. Response lt ground_voltage gt lt ref_temp gt Description The CARD REFTEMP query allows you to read back the ground volt age and calibration reference temperature from a Model 7700 in Slot 1 through Slot 5 respectively lt NRf gt 1 to 5 The two response values are delimited by a comma Example CAL PROT CARD REFTEMP 1 Request card 1 temp g 3 e oO oO E e oO B 20 Calibration Reference Model 2750 Multimeter Switch System Service Manual SAVE CALibration PROTected CARD1 SAVE Purpose To save calibration constants in card EEROM after the calibration pro cedure Format cal prot cardl1 save Parameters None Description The SAVE command stores calculated calibration constants derived during Model 7700 calibration in card EEROM EEROM is non volatile memory Calibration constants will be retained indefinitely once saved Generally SAVE is sent after all other calibration steps except for LOCK NOTE Card calibration will be only temporary unless the SAVE command is sent to permanently store calibration constants Example CAL PROT CARD1 SAVE Save card calibration constants STEPO CALibration PROTected CARD1 STEPO Purpose To perform Model 7700 calibration Format cal prot cardl stepO lt temp gt Parameters lt temp gt Cold calibration temperature C Description STEPO performs temperature sensor calibration of the Model 7700 The card must be
15. 60W 125VA maximum Card Sense CONTACT LIFE typ 2105 operations at max signal level 2108 operations cold switching CONTACT RESISTANCE 10 at end of Channel 1 contact life 10 oo Channel 25 CONTACT POTENTIAL Channesz9 Backplane lt 4500nV typical per contact 1uV max isolation lt 4500nV typical per contact pair 1 V HI o o HI max Channel 10 Input OFFSET CURRENT lt 100pA um dE ZE 9 CONNECTORTYPE Screw terminal 20 Rene 5 Channel 23 Q 0 46 AWG wire size 2 Pole Open Channel 24 4 Pole Closed A see Note ISOLATION BETWEEN ANY TWO see Note Backplane TERMINALS gt 102 Q lt LOOpF i isolation ISOLATION BETWEEN ANY TERMINAL Soho S ERN euz 1 k Mode AND EARTH gt 10 0 lt 200 10 oto nr EE To Mod CROSS TALK 10MHz 500 Load 40dB Backplane Channels 12 19 INSERTION LOSS 500 Source 500 Load 0 1dB below 1MHz HI o oT o 3dB below 2M Hz Channel 20 COMMON MODE VOLTAGE 300 LO o oo between any terminal and chassis MEER T C COLD JUNCTION ak AMPS 1 0 18 28 C Mainframe Temp HI o N 5 1 5 0 18 amp 28 50 C Mainframe Channel 21 DT O Temp LO 3A NOTE Channels 23 25 in this schematic ENVIRONMENTAL HI o ooo refer to the designations used for OPERATING ENVIRONMENT Channel 22 5 controland not actual available channels Spe
16. AC current tert 5 1 25 Verifying normal resistance ru 1 26 Verifying dry circuit resistance ra 1 28 Verifying temperature rru 1 31 Verifying frequency Be ERROR UR 1 34 Verifying ratio and average ru 1 35 Calibration Introduction AE 2 2 Environmental conditions ra 2 2 Warmup period rrua 2 2 Line power sennen eaen arae a EE 2 2 Calibration considerations 2 3 Calibration code ardan epit einer 2 4 Front panel calibration code 2 4 Remote calibration code rra 2 4 Comprehensive calibration rra 2 5 Calibration Cycle ararte udatan paran 2 5 Recommended equipment rra 2 5 Aborting calibration 2 2 6 Front panel calibration rra 2 6 Remote calibration rra 2 14 Manufacturing calibration rr 2 20 Recommended test equipment rra 2 20 Extender board preparation rra 2 20 Unlocking manufacturing calibration 2 21 Measuring function generator signal amplitude 2 21 Front panel manufacturing calibration 2 21 Remote manufacturing calibration rra 2 22 Model 7700 calibration sr 2 23 Recommended test equipment rra 2 23 Extender board connections rra 2 24 Model 7700 calibration ra 2 24 Routine Maintenance Inner Rm 3 2 Setting the line voltage and replacing the line fuse 3 2 Replacing the AMPS fuse rra 3 4 Replacing Model 7700 plug in module
17. Check for cal error D D yyyy mm dd D D Save calibration constants Lock out calibration Check for key press routine Flush keyboard buffer ESC to abort program Model 2750 Multimeter Switch System Service Manual DO IS INKEYS LOOP WHILE 1 IF I CHR 27 THEN GOTO EndProg RETURN 1 CalEnd PRINT Performing calibration step I DO PRINT 1 SRQ INPUT 2 LOOP UNTIL s PRINT 1 OUTPUT 16 ESR PRINT 1 ENTER 16 INPUT 2 PRINT 1 SPOLL 16 INPUT 2 RETURN ErrCheck PRINT 1 OUTPUT 16 SYST ERR PRINT 1 ENTER 16 INPUT 2 E Err IF E lt gt 0 THEN PRINT Err GOTO ErrCheck RETURN Settle DO PRINT 1 OUTPUT 4 ISR PRINT H1 ENTER 4 INPUT 2 LOOP UNTIL s AND amp H1000 RETURN 1 EndProg BEEP PRINT Calibration aborted PRINT 1 OUTPUT 4 STBY PRINT 1 OUTPUT 16 SYST PRES PRINT 1 LOCAL 4 16 Calibration Program C 5 Abort if ESC is pressed Check for cal step completion Request SRQ status Input SRQ status byte Wait for operation complete Clear OPC Clear SRQ Error check routine Query error queue Display error Calibrator settling routine Query status register Test settle bit Close files end program CLOSE END CmdList DATA Connect low thermal short to inputs wait 3 minutes DC STEP1 DATA Disconnect low thermal short from in
18. DUAL PICOAMP OP AMP AD706JR IC 910 U124 IC 5V VOLTAGE REGULATOR IC 1371 oO oO O E m 77 6 10 Replaceable Parts Table 6 1 continued Model 2750 motherboard parts list Model 2750 Multimeter Switch System Service Manual Circuit Designation Description Keithley Part No U125 IC 15V VOLTAGE REGULATOR IC 1241 U127 U173 U174 U181 U196 IC QUAD 2 IN AND 74 08 IC 837 U128 U166 IC OP AMP MC34081BD IC 1058 U132 U138 U139 U190 IC OPA177GS IC 960 U133 U208 IC CMOS ANAL SWITCH DG444DY IC 866 U135 IC 32 BIT MICROCONTROLLER 20MHZ LSI 203 20 U136 IC 2048 X 8 SERIAL E 2 PROM IC 1318 U137 IC HI SPEED BIFET OP AMP AD711JR IC 894 U140 U143 IC PHOTO TRANS TLP626BV LFI IC 1006 0141 PRECISION REFERENCE LM399 196 600A U142 IC OP AMP NE5534D IC 802 U144 IC 5V VOLTAGE REGULATOR IC 576 LM2940CT U146 U179 IC POS GATES INVERT 74HCT14 656 U147 U191 IC TINYLOGIC CMOS INVERTER IC 1282 U148 U153 IC QUAD 2 IN NOR 74HCT02 IC 809 U149 IC NCHAN LAT DMOS QUADFET IC 893 SD5400CY U150 IC OPTOCOUPLER 2611 IC 690 U151 U152 U164 U193 IC 512K X 8 BIT CMOS SRAM LSI 234 70 U154 IC QUAD D FLIP FLOP W CLK RESET IC 923 7 175 0155 OPTOCOUPLER 2601 IC 239 U156 PROGRAMMED ROM 2750 800A01 U157 PROGRAMMED ROM 2750 801 A01 U158 IC GPIB ADAPTER 9914A LSI 123 U159 IC 45V RS 232 TRANSCEIVER MAX202 952 U160 IC OCTAL INTERFACE BUS 75160 IC 646 U
19. E Performance Verification Model 2750 Multimeter Switch System Service Manual Install the Model 7700 in Slot 1 of the Model 2750 then turn on the power and allow the unit to warm up for two hours before proceeding Be sure the front panel INPUTS switch is set to the REAR position Select the temperature function by pressing the TEMP key Close Channel 1 by pressing the CLOSE key then ENTER for SINGLE channel and keying in 101 Configure the Model 2750 for C units type K temperature sensor and internal ref erence junction as follows a Press SHIFT then SENSOR and note the unit displays the temperature units UNITS C If necessary use the cursor and range keys to select C units b Press ENTER The unit displays the sensor type SENS TCOUPLE Make sure that TCOUPLE is displayed then press ENTER The unit displays the thermocouple type TYPE J d Selecta type K temperature sensor then press ENTER The unit displays the reference junction type JUNC SIM e Select INT reference junction then press ENTER NOTE Defaults for 7700 7706 and 7708 modules are Ktype C units Internal temperature sensor Open Tdetect off Sensor type Tcouple Source each of the voltages summarized in Table 1 16 and verify that the tempera ture readings are within limits Be sure to select the appropriate thermocouple type for each group of readings See step 3 above Open Channel 1 after the test is complete Ta
20. Figure 1 6 Figure 1 7 Figure 1 8 Figure 1 9 Figure 1 10 Figure 1 11 Figure 1 12 Figure 1 13 Figure 1 14 Figure 1 15 Figure 1 16 Figure 1 17 Figure 1 18 2 Figure 2 1 Figure 2 2 Figure 2 3 Figure 2 4 Figure 2 5 3 Figure 3 1 Figure 3 2 Figure 3 3 Figure 3 4 Performance Verification Connections for Model 2750 DC volts verification 1 9 Connections for Model 2750 AC volts verification 1 10 Connections for Model 2750 DC current verification 1 12 Connections for Model 2750 AC current verification 1 13 Connections for Model 2750 resistance verification 1Q to 10 ranges rr 1 14 Connections for Model 2750 resistance verification 100 range sr 1 15 Connections for Model 2750 dry circuit resistance verification ra 1 17 Connections for Model 2750 frequency verification 1 20 Connections for Model 7700 DC volts verification 1 21 Connections for Model 7700 AC volts verification 1 22 Connections for Model 7700 DC current verification 1 24 Connections for Model 7700 AC current verification 1 25 Connections for Model 7700 resistance verification 1Q to 10 ranges 1 27 Connections for Model 7700 resistance verification 100MQ fange tree EE eens 1 27 Connections for Model 7700 dry circuit r sistance verification arruta rt e e ete eee sense 1 29 Connections for Model 7700 thermo
21. PROT CARD1 INIT Initiate 7700 calibration OCK CALibration PROTected CARD1 LOCK Purpose To lock out Model 7700 calibration Format Cal prot card1 lock Parameters None Description The LOCK command allows you to lock out Model 7700 calibration after completing the procedure Thus LOCK performs the opposite of enabling calibration with the CODE command Example CAL PROT CARD1 LOCK Lock out card 1 calibration Model 2750 Multimeter Switch System Service Manual Calibration Reference B 19 LOCK CALibration PROTected CARD1 LOCK Purpose To read Model 7700 calibration lock status Format cal prot card1 lock Response 0 Calibration locked 1 Calibration unlocked Description The LOCK query requests status from the Model 2750 on Model 77700 calibration locked unlocked state Calibration must be enabled sending the CODE command before calibration can be performed Example CAL PROT CARD1 LOCK Request card 1 cal lock state RCOunt CALibration PROTected CARD1 RCOunt Purpose To reset card calibration count to 0 Format Cal prot card1 rco Parameters None Description The RCOunt command resets the card calibration count reported by COUNt to 0 Example CAL PROT CARDI RCO Rest card calibration count REFTEMP CALibration PROTected CARD REFTEMP lt NRf gt Purpose To request the Model 7700 reference calibration temperature Format cal prot card reftemp NRf lt NRf gt 1105
22. STEP7 B 10 STEPS B 11 STEP9 B 11 Q2 signal multiplexing and gain 4 22 Q2 signal switching 4 17 Q2 O4 reference switching 4 19 4 20 Q4 signal multiplexing and gain 4 22 Q4 signal switching 4 18 4 19 AC calibration commands B 13 AC characteristics accuracy A 12 AC current A 14 A 15 verifying Model 2700 1 13 AC voltage A 14 A 15 verifying Model 2700 1 10 verifying Model 7700 1 22 ACA signal switching 4 20 Accuracy calculations A 12 ACV and ACA signal multiplexing and gain 4 21 ACV and FREQ signal switching 4 16 AMPS input 4 10 Analog circuitry 4 8 block diagram 4 9 Analog signal switching states 4 15 Assembly drawings 5 3 battery replacement 3 6 calibration 2 1 aborting 2 6 AC current 2 13 AC voltage 2 12 code 2 4 comprehensive 2 5 considerations 2 3 cycle 2 5 DC current 2 11 DC volts 2 8 front panel 2 6 front panel short and open 2 7 Model 7700 2 24 Model 7700 and 7706 2 23 preparing the Model 2700 2 6 recommended equipment 2 5 Remote Model 7700 2 25 resistance 2 10 setting dates and saving 2 13 step completion B 25 calibration code front panel 2 4 remote 2 4 calibration commands AC B 13 DC B 8 manufacturing B 15 miscellaneous B 4 Model 7700 and 7706 B 16 calibration program C 1 Calibration equipment C 2 Computer hardware requirements C 2 General instructions C 3 Model 2700 C 3 Software requirements C 2 Calibration Reference B 1 Card cage removal 5 5 Case cover removal 5 4 Command
23. below to replace the battery if required Refer to the disassembly procedures in Section 5 and the parts list and component layout drawings at the end of Section 6 for more informa tion WARNING There is a danger of explosion if the battery is incorrectly replaced Replace only with the same or equivalent type recommended by the manufacturer Dispose of used batteries according to federal state and local laws The following procedure is intended only for qualified service person nel Do not perform this procedure unless you are qualified to do so Disconnect the line cord and all connecting wires from the Model 2750 before removing the top cover Model 2750 Multimeter Switch System Service Manual Routine Maintenance 3 7 WARNING The precautions below must be followed to avoid personal injury Wear safety glasses or goggles when working with lithium batteries Do not short the battery terminals together Keep lithium batteries away from all liquids Do not attempt to recharge lithium batteries Observe proper polarity when installing the battery Do not incinerate or otherwise expose the battery to excessive heat gt 60 C Bulk quantities of lithium batteries should be disposed of as haz ardous waste Dispose of used batteries according to all federal state and local laws Replace the battery as follows 1 Before replacing the battery refer to the troubleshooting procedures in Table
24. cal prot dc step5 Cal voltage Cal voltage 90 to 110 V STEP5 programs the 100V DC comprehensive calibration step The allowable range of the calibration voltage parameter is from 90 to 110 but 100 is recommended for best results CAL PROT DC STEP5 100 Program 100V step CALibration PROTected DC STEP6 Purpose Format Parameters Description Example STEP7 To program the 1000 4 wire comprehensive calibration step cal prot dc step6 Cal resistance Cal resistance 90 to 110 Q STEP6 programs the 1000 4 wire resistance comprehensive calibra tion step The allowable range of the calibration resistance parameter is from 90 to 110 but 100 is recommended for best results CAL PROT DC STEP6 100 Program 100Q step CALibration PROTected DC STEP7 Purpose Format Parameters Description Example To program the 10kQ 4 wire comprehensive calibration step cal prot dc step7 Cal resistance Cal resistance 9E3 to 11E3 Q STEP7 programs the 10kQ 4 wire resistance comprehensive calibra tion step The allowable range of the calibration resistance parameter is from 9E3 to 11E3 but 10E3 is recommended for best results CAL PROT DC STEP7 10E3 Program 10kQ step Model 2750 Multimeter Switch System Service Manual Calibration Reference B 11 STEPS CALibration PROTected DC STEP8 Purpose To program the 100kQ 4 wire comprehensive calibration step Format Cal prot dc step8 Cal r
25. make sure that power has been removed from the card for at least two hours to allow card circuitry to cool down After turning on the power during the calibration procedure complete the procedure as quickly as possible to minimize card heating that could affect calibration accuracy Allow the Model 2750 to warm up for at least two hours Front panel Model 7700 calibration 1 Connect the Model 7700 to the Model 7797 Calibration Extender Board see Extender board connections With the power off install the Model 7700 7797 combination in Slot 1 and select the rear inputs with the INPUTS switch Allow three minutes for thermal equilibrium Accurately measure and record the cold temperature of the Model 7700 card sur face at the center of the card with an RTD sensor Press in and hold the Model 2750 OPEN key while turning on the power Press SHIFT then TEST then display TEST CALIB with the up or down range key Press ENTER select RUN then enter the appropriate calibration code default 002750 Using the up or down range key select CARD at the CAL RUN prompt then press ENTER Set the display value to the cold calibration temperature you measured in Step 3 then press ENTER to complete Model 7700 calibration Model 2750 Multimeter Switch System Service Manual Calibration 2 25 Remote Model 7700 calibration 1 Connect the Model 7700 to the 7797 Calibration Extender Board see Extender board connections abov
26. 1 100MW THICK FILM R 418 49 9K R297 R321 R322 RES 2 21K 1 100MW THICK FILM R 418 2 21K R302 RES 499 1 1OOMW THICK FILM R 418 499 R304 RES 20K 1 100MW THICK FILM R 418 20K R306 RES 4 99K 1 1 4W METAL FILM R 391 4 99K R308 R347 R399 RES 100 1 1OOMW THICK FILM R 418 100 R309 RES 1 1 10W METAL FILM R 263 1K R310 RES 9 09K 1 1 10W METAL FILM R 263 9 09K R311 RES 392 1 1OOMW THICK FILM R 418 392 R312 R313 RES 332K 1 100MW THICK FILM R 418 332K R318 RES 73 2K 1 100MW THICK FILM R 418 73 2K R323 RES 150 1 100MV THIN FILM R 438 150 R333 R334 R344 R345 R370 R371 RES 10K 1 100MW THICK FILM R 418 10K R378 R382 R335 RES 33 5 250MW METAL FILM R 376 33 R341 R421 RES 1 1OOMW THICK FILM R 418 1K R350 RES 6 04K 1 125MW THIN FILM R 423 6 04K R353 RES 200 1 1OOMW THICK FILM R 418 200 R354 RES 200 1 1OOMW THICK FILM R 418 200 R355 R359 R363 R367 R397 R403 RES 4 75K 1 1000MW THICK FILM R 418 4 75K R357 RES 10K 1 100MW THICK FILM R 418 10K R368 RES 100 1 1OOMW THICK FILM R 418 100 Model 2750 Multimeter Switch System Service Manual Replaceable Parts 6 9 Table 6 1 continued Model 2750 motherboard parts list Circuit Designation Description Keithley Part No R369 RES 10M 196 125MW THICK FILM R 418 10M R386 RES NET 50K 1 5W THICK FILM TF 243 50K R387 RESISTOR NETWORK 10K 10K TF 236 R388 RES NET 5K 1 668
27. 1 to 5 Response lt n gt Calibration count Description The CARD COUNt command allows you to determine how many times a Model 7700 in Slot 1 through Slot 5 lt NRf gt 1 to 5 respec tively has been calibrated NOTE Usethe command to help you monitor for unauthorized calibration procedures Example CAL PROT CARD COUN 1 Request card 1 calibration count E 5 e c c 5 B 18 Calibration Reference Model 2750 Multimeter Switch System Service Manual DATE CALibration PROTected CARD DATE lt NRf gt Purpose To request the Model 7700 calibration date Format cal prot card date NRf lt NRf gt 1to5 Response year month day Description The CARD DATE query allows you to read back the calibration date from a Model 7700 in Slot 1 through Slot 5 respectively lt NRf gt 1 to 5 NOTE The card calibration date is automatically set to the Model 2750 real time clock date when the card is calibrated Example CAL PROT CARD DATE 1 Request card 1 cal date INIT CALibration PROTected CARD1 INITiate Purpose To initiate Model 7700 calibration procedures Format Cal prot cardl init Parameters None Description The INIT command enables Model 7700 calibration when perform ing these procedures over the bus This command must be sent to the unit after sending the CODE command but before performing Model 7700 calibration Example CAL
28. 11 Table 2 12 Table 2 13 Table 2 14 3 Table 3 1 Table 3 2 Performance Verification Recommended verification equipment 1 4 DCV reading rra 1 9 ACV reading limits rss 1 11 IDCT DImitSz E SPEED EE eee iens 1 12 ACL hints eicit RES 1 13 Limits for normal resistance verification 1 16 Limits for Model 2750 dry resistance verification 1 18 Thermocouple temperature verification reading limits 1 19 Four wire RTD temperature verification reading limits 1 19 Plug in module reading limits 1 22 Plug in module ACV reading limits sr 1 23 Plug in module DCI limits rr 1 25 Plug in module ACT limits sr 1 26 Limits for plug in module normal resistance verification 1 28 Limits for plug in module dry circuit resistance earra atan eres 1 30 Model 7700 thermocouple temperature verification reading limits rra 1 32 Plug in module four wire RTD temperature verification reading limits rra 1 33 Calibration Recommended equipment for comprehensive calibration 2 5 Comprehensive calibration procedures 2 7 DC volts calibration summary rra 2 9 Ohms calibration summary rr 2 10 DC current calibration summary rr 2 11 AC voltage calibration summary 8 2 12 AC current calibration summary rrura 2 13 DC voltage calibration progra
29. 20 front panel 2 21 Recommended test equipment 2 20 remote 2 22 Unlocking manufacturing calibration 2 21 measurement accuracy optimizing A 14 measurement speed optimizing A 15 Measuring function generator signal amplitude 2 21 Memory circuits 4 7 Microcontroller 4 7 Microprocessor 4 7 Model 7700 amps fuse 3 5 Model 7700 and 7706 calibration commands B 16 Module slot control 4 8 Motherboard removal 5 4 Multiplexer and A D converter 4 11 No comm link error 4 23 operation principles 4 4 Ordering information 6 2 Parts lists 6 2 Performance Verification 1 1 power components removing 5 5 Power module removal 5 6 Power module wire colors 5 7 Power supply 4 4 block diagram 4 4 Power supply checks 4 13 Power supply components 4 5 Power transformer removal 5 5 Power on self test 4 3 ratio and average verifying Model 7700 1 35 reading limit ACV Model 2700 1 11 calculating resistance 1 5 calculation example 1 5 DCV Model 2700 1 9 four wire RTD temperature verification Model 2700 1 19 Model 7700 thermocouple temperature verification 1 32 Plug in module ACV Model 7700 1 23 Plug in module DCV Model 7700 1 22 Plug in module four wire RTD temperature verification Model 7700 1 33 thermocouple temperature verification Model 2700 1 19 Recommended test equipment 1 4 2 23 Remote calibration 2 14 AC current 2 19 AC voltage 2 18 command summary B 2 DC current 2 17 DC volts 2 15 Locking out calibra
30. 2750 INPUT and SENSE jacks using four wire connections See Figure 1 5 for similar connecting scheme Be sure the INPUTS switch is in the FRONT position 2 Configure the Model 2750 temperature function for C units and RTD temperature sensor 0 0 00385 as follows a Press SHIFT then SENSOR and note the unit displays the temperature units UNITS C Press ENTER and note the unit displays the sensor type SENS TCOUPLE Using the cursor and range keys set the display as follows SENS 4W RTD Press ENTER and note the unit displays TYPE PT100 Using the cursor and range keys set the unit for the following display TYPE PT385 f Press ENTER to complete the temperature configuration process 3 Select the temperature function by pressing the TEMP key 4 Setthe decade resistance box to each of the values shown in Table 1 9 and verify that the temperature readings are within the required limits E Table 1 9 Four wire RTD temperature verification reading limits Applied Resistance Reading Limits 1 year 18 C to 28 C 22 800 190 06 to 189 94 100 000 0 06 to 0 06 313 590 599 94 to 600 06 Based on o 0 00385 See text 1 20 Performance Verification Model 2750 Multimeter Switch System Service Manual Verifying frequency Follow the steps below to verify the Model 2750 frequency function 1 Connect the function generator to the Model 2750 INPUT jacks See Figure 1 8 Be sure t
31. 3 14A 1 POWER ROD 704 313A 1 REAR PANEL 2750 303A 1 RUBBER GROMMET GR 55 1 4 SCREWLOCK FEMALE CS 725 5 SOCKET CONNECTOR CS 984 1 1 TEST LEADS CA 22 1 TILT BAIL 2750 319A 1 TRANSFORMER TR 347A Model 2750 Multimeter Switch System Service Manual Replaceable Parts 6 15 Table 6 5 Model 7700 module parts list Circuit Designation Description Keithley Part No C1 C9 C10 C11 C14 C15 C22 C4 CAP 0 1UF 20 50V CERAMIC C 418 1 C16 CAP 220U 20 10V TANTALUM C 558 220 C17 C18 C19 C21 C25 C26 C23 47P 5 100V CERAMIC C 465 47P C24 C15 C2 C6 C7 C8 C12 C13 C20 C27 0 1UF 20 50V CERAMIC C 418 1 C28 C31 C29 C32 C33 C34 CAP 47P 5 100V CERAMIC C 465 47P C30 CAP 4 7U 10 35V TANTALUM C 476 4 7 CR1 CR22 DIODE DUAL SWITCHING BAV99L RF 82 CR23 CR24 CR26 CR27 DIODE SWITCHING MMBD914 RF 83 CR2 CR21 CR25 DIODE DUAL SWITCHING BAV99L RF 82 EL EO FUSE 3A FU 107 1 CONN RT ANGLE DUAL ROW RECEPT CS 1065 1 K1 K21 K24 K25 K26 K27 SINGLE COIL LATCH RELAY RL 225 K22 K23 NON LATCHING RELAY RL 242 Ql N CHANNEL P CHANNEL POWER TG 360 MOSFET 02 04 TRANS PNP SILICON TG 388 Q3 Q6 Q49 Q50 TRANS NPN SILICON TG 389 034 36 38 40 42 44 46 7 TRANS PNP SILICON TG 388 Q35 37 39 41 43 45 47 48 TRANS NPN SILICON TG 389 Q5 P CHANNEL TMOSFET TG 392 Q8 10 12 14 16 18 20 22 24 26 28 TRANS PNP SILICON TG 388 30 32 Q9 11 13 15 17 19 21 23 25 27 29 TRANS NPN SILICON TG 389 31 33 RI RES 69
32. 50 2 operation using factory defaults operating conditions RST Autorange off Display off Limits off Trigger delay 0 16 Speeds include measurements and binary data transfer out the GPIB reading element only 17 Sample count 1024 auto zero off 18 Auto zero off NPLC 0 01 19 Additional Uncertainty Plug In Modules 7709 7701 7703 7707 7700 7708 7706 Simulated Simulated Using Using Type Range Ref Junction Ref Junction CJc CJc J 200 to 0 C 0 1 0 3 0 8 16 K 200 to 0 C 0 2 0 4 08 16 200 to 0 C 0 3 0 6 0 8 16 T 200 to 0 C 0 1 0 3 0 8 16 E 200 to 0 C 0 1 0 2 0 8 16 R Oto 400 C 0 6 11 05 1 0 S Oto 400 C 0 6 12 05 10 B 3350 to 1100 C 0 3 05 05 10 20 For lead resistance gt 00 add the following uncertainty Q for measurement temperatures of 70 100 C 100 150 2 2kQ 44004 0 22 C 1 11 C 5 0kQ 44007 0 10 C 0 46 C 10kQ 44006 0 04 C 0 19 C 21 For 4 wire Q only offset compensation on LSYNC on 22 For Dry Circuit 1kQ range 2 readings s max Specifications A 5 23 For Front Inputs add the following to Temperature Coefficient ppm of reading uncertainty 1M Q 25ppm 10MQ 250ppm 100M Q 2500ppm Operating environment specified for 0 C to 50 C and 50 RH at 35 C AC SPECIFICATIONS Accuracy H of reading of range 23 C 5 C Calibration 3Hz 10Hz 20 kHz 50 kHz 100 kHz Function Range Resolution Cyde 10Hz 20kHz 50kHz 100kHz 300 kHz Voltage 100
33. 699 36 to 700 64V 698 79 to 701 21V Tf the 5725A amplifier is not available change the 700V 50kHz step to 220V 50kHz Reading limits for 220V 50kHz 219 36 to 220 64V Verifying DC current Check DC current accuracy by applying accurate DC currents from the DC current cali brator to the AMPS input of the Model 2750 and verify that the displayed readings fall within specified limits Follow these steps to verify DC current accuracy 1 Connect the Model 2750 AMPS and INPUT LO jacks to the calibrator as shown in Figure 1 3 Be sure the INPUTS switch is in the FRONT position 2 Select the DC current measurement function by pressing the DCI key Model 2750 Multimeter Switch System Service Manual 1 12 Performance Verification Figure 1 3 Connections for Model 2750 DC current verification Calibrator Output DC Current Model 2750 Front Panel E ol Q Output H m Amps Note Be sure calibrator is set for normal current output 3 Setthe Model 2750 for the 20mA range 4 Source positive and negative full scale currents for each of the ranges listed in Table 1 4 and verify that the readings for each range are within stated limits Table 1 4 DCI limits DCI Range Applied DC Current Reading Limits 1 year 18 C to 28 C 20mA 20 0000mA 19 89960 to 20 01040mA 100mA 100 0000mA 99 9
34. 8 10135 lines DO D15 9 UI35 pin 60 10 U159 pin 13 11 U159 pin 14 12 17158 pins 34 42 13 U158 pins 26 31 14 17158 pin 24 15 U158 pin 25 16 1135 pin 48 17 0135 pin 76 18 U135 pin 77 19 UI135 pin 74 Required Condition RAM OK ROM OK Digital common 5 5VD supply 5 5VB supply 3V Low on power up then goes high Check for stuck bits Check for stuck bits 32 758kHz Pulse train during RS 232 I O Pulse train during RS 232 I O Pulse train during IEEE 488 I O Pulses during IEEE 488 I O Low with remote enabled Low during interface clear Pulse train Pulse train Pulse train Pulse train Remarks Verify that RAM and ROM are functional All signals referenced to digital common Digital logic supply Battery backed memory supply Battery voltage BT100 MPU RESET line MPU address bus MPU data bus MPU clock RS 232 RX line RS 232 TX line TEEE 488 data bus IEEE 488 command lines TEEE 488 REN line TEEE 488 IFC line ADRXB ADTX ADCLK ADTS Model 2750 Multimeter Switch System Service Manual Analog signal switching states Troubleshooting 4 15 Table 4 5 through Table 4 13 provide switching states of the various relays FETs and analog switches for the basic measurement functions and ranges These tables can be used to assist in tracing an analog signal from the input to the A D multiplexer Table 4 5 DCV signal switc
35. 9 J1006 CONN MICRODIN W GND FINGERS CS 792 J1007 CONN D SUB MALE BOARDLOCK TYPE CS 848 9 Model 2750 Multimeter Switch System Service Manual Replaceable Parts 6 5 Table 6 1 continued Model 2750 motherboard parts list Circuit Designation Description Keithley Part No J1008 LATCHING HEADER FRICTON CS 724 3 SGL ROW J1010 CONN FEMALE 8 PIN CS 612 8 J1012 CONN HEADER STRAIGHT SOLDER PIN CS 368 20 J1014 CONN HEADER STRAIGHT SOLDER PIN CS 368 16 J1015 CONN HEADER STRAIGHT SOLDER PIN CS 368 10 J1016 CONN HEADER STRAIGHT SOLDER PIN CS 368 26 J1017 LATCHING HEADER FRICTION SINGLE CS 724 12 ROW K101 K102 K103 K104 RELAY MINATURE DPDT TQ2E L2 5V RL 155 EA2 5TNJ L101 L102 L103 L104 L123 FERRITE CHIP 600 OHM BLM32A07 CH 62 L105 L106 L118 L119 L125 L126 FERRITE CHIP 600 OHM BLM32A07 CH 62 L501 L107 CHOKE CH 61 L108 DATA LINE FILTER CH 111 1 L109 CHOKE EMI CH 57 L110 L111 L112 L113 L114 L116 CHOKE 22UH CH 66 22 L117 L124 L120 L122 CHOKE 22UH CH 66 22 L121 CHOKE 100U SM INDUCTOR CH 66 100 LS101 BEEPER 5V 30MA QMX 05 EM 6 M315 M316 WIRE ROUTING CABLE CLAMP CC 88 1 Q101 Q102 Q159 N CHANNEL MOSFET TG 387 Q104 Q107 Q113 Q114 Q126 TRANS N CHANNEL JFET SNJ132199 TG 294 Q136 Q137 Q148 Q106 Q117 TRANS N CHANNEL JFET SNJ132199 TG 294 Q108 Q109 Q123 Q124 Q171 TRANS N CHANNEL JFET SST4118 TG 347 Q110 Q112 Q115 Q118 Q149 TRANS NPN MMBT3904 TG 238 Q160 Q164 Q111 Q116 Q129 Q163 Q165 TRA
36. C124 C125 CAP 1UF 20 50V CERAMIC C 418 1 C127 C133 C135 C120 CAP 270PF 5 100V CERAMIC C 465 270P C123 C241 C245 CAP 1000P 10 100V CERAMIC C 451 1000P C131 C148 CAP 1000U 20 35V ALUM ELEC C 595 1000 C132 CAP 220PF 10 100V CERAMIC C 451 220P C134 C140 C224 C235 C251 C287 CAP 47PF 1096 100V CERAMIC C 451 47P C121 C136 C138 C139 C142 C144 C147 CAP 1UF 20 50V CERAMIC C 418 1 C153 C155 C137 CAP 3 5 100V CERAMIC C 465 33P C143 CAP 100P 10 100V CERAMIC C 451 100P C145 C240 CAP 1000PF 20 50V CERAMIC C 418 1000P C146 CAP 1000UF 20 16V ALUMINUM C 488 1000 C150 C285 C288 C289 CAP 47PF 10 100V CERAMIC C 451 47P C152 C164 CAP 39U 20 1000V CERAMIC C 616 39 C156 C273 C274 C281 CAP 3300U 20 16V ALUM ELEC C 592 3300 C157 CAP 100PF 5 100V CERAMIC C 465 100P C159 C163 C167 C170 C172 CAP 1UF 20 50V CERAMIC C 418 1 C174 C178 C180 C165 CAP 1UF 20 50V CERAMIC C 418 1 oO oO O E m 77 6 4 Replaceable Parts Table 6 1 continued Model 2750 motherboard parts list Model 2750 Multimeter Switch System Service Manual Circuit Designation Description Keithley Part No C171 C177 CAP 2200P 10 100V CERAMIC C 430 2200P C175 C209 CAP 22UF 20 25V TANTALUM C 440 22 C179 C266 CAP 100PF 5 100V CERAMIC C 465 100P C182 C185 C187 C190 C193 CAP 1UF 20 50V CERAMIC C 418 1 C194 C197 C199 C186
37. C189 C191 CAP 01UF 2096 50V CERAMIC C 418 01 C188 CAP 10PF 5 50V MONO CERAMIC C 452 10P C201 C208 C210 C212 C218 CAP 1UF 2096 50V CERAMIC C 418 1 C221 C223 C225 C220 C222 C255 CAP 47P 5 100V CERAMIC C 465 47P C262 C268 C303 C311 C227 C229 C231 C234 C236 CAP 1UF 2096 50V CERAMIC C 418 1 C239 C250 C263 C230 C296 CAP 01UF 20 50V CERAMIC C 418 01 C242 C243 C246 C249 C283 C284 CAP OLUF 1096 50V CERAMIC C 491 01 C244 C267 C272 C278 CAP 1000PF 20 50V CERAMIC C 418 1000P C252 CAP 22PF 1096 100V CERAMIC C 451 22P C264 C265 C291 C292 CAP 15 1 100V CERAMIC C 512 15P C269 C271 C275 C276 C279 CAP 1UF 2096 50V CERAMIC C 418 1 C298 C299 C149 C293 C294 CAP 47UF 20 25V ALUM ELEC C 314 47 C297 C302 CAP 1UF 2096 50V CERAMIC C 418 1 C300 C301 CAP 270PF 5 100V CERAMIC C 465 270P 102 103 DIODE BRIDGE DF01 RF 52 CR104 CR106 DIODE BRIDGE PE05 RF 48 105 DIODE HI VOLTAGE HV 15 RF 76 CR107 CR109 CR111 CR112 DIODE DUAL SWITCHING BAV99L RF 82 115 117 110 118 DIODE DUAL HSM 2822T31 RF 95 119 DIODE SWITCHING MMBD914 RF 83 CR120 CR122 CR125 DIODE DUAL COMMON ANODE RF 98 BAWS6LT2 CR126 CR101 CR113 CR114 DIODE DUAL SWITCHING BAV99L RF 82 DS101 DS102 PILOT LIG HSMH T400 LED PL 92 1 J1002 CONN RT ANGLE HEADER CS 1017 1 J1003 CONN RT ANGLE HEADER 5 PINS CS 1017 2 J1004 CONN RIGHT ANGLE 24PIN CS 507 J1005 CONN RT ANGLE MALE 9 PIN CS 761
38. I Source Q119 Q123 Q124 Q125 Q126 102 U123 U133 Dry Circuit Voltage Clamps U162 U206 Temp Sensor Front Terminals Protection O mE DS101 ow Ohms 102 5101 Sensing Q106 SENSE SSP Scanner Outputs HI Q150 Q151 Front Terminals O 5101 SENSE SSPE Scanner Outputs LO Q122 Q135 Scanner Outputs Slot Control nputs er je rc nputs E oO E ge Solid State Protection 4 10 Troubleshooting Model 2750 Multimeter Switch System Service Manual INPUT HI INPUT HI protection is provided by the SSP Solid State Protection circuit The SSP is primarily made up of Q101 and Q102 An overload condition opens Q101 and Q102 which disconnects the analog input signal from the rest of the analog circuit Note that for the 100VDC and 1000VDC ranges Q101 and Q102 of the SSP are open The DC voltage signal is routed through the DCV Divider Q114 and Q136 on to the DCV switching circuit AMPS input The ACA or DCA input signal is applied to the Current Shunt circuit which is made up of K103 R158 R205 and R338 For the 20mA DC range 5 1Q R205 R338 R158 is shunted across the input Relay K103 is energized set state to select the shunts For all other DCA ranges and all ACA ranges 0 19 R158 is shunted across the input K103 reset The ACA signal is then sent to the AC Switching amp Gain circuit
39. NRf gt 1009 4 wire step STEP7 lt NRf gt 10kQ 4 wire step 5 8 lt NRf gt 100kQ 4 wire step STEPO lt NRf gt 4 wire step Model 2750 Multimeter Switch System Service Manual Calibration Reference B 3 Table B 1 continued Remote calibration command summary Command Description CALibration PROTected DC STEP 10 lt NRf gt 10mA DC step STEP11 lt NRf gt 100mA DC step 5 12 lt NRf gt 1A DC step AC AC cal steps STEPI 10mV AC at 1kHz step STEP2 100mV AC at 1kHz step STEP3 100mV AC at 50kHz step STEPA AC at 1KHz step 5 5 AC at 50kHz step STEP6 10V AC at 1kHz step STEP7 10V AC at 5OKHz step 5 8 100V AC at 1kHz step STEPO 100V AC at 50kHz step STEPIO 700V AC at 1kHz step STEPI I 100mA AC at 1kHz step STEPI2 1A AC at 2 step STEPI3 2A AC at 1kHz step STEP14 1V AC at 3Hz geni STEPI5 1V AC at IKHz step Note Upper case letters indicated short form of each command For example instead of sending CALibration PROTected INITiate you can send CAL PROT INIT DC STEPO AC STEP14 and AC STEP15 are one time factory calibration points and are valid only in manu facturing calibration mode O E 5 e c c 5 B 4 Calibration Reference Model 2750 Multimeter Switch System Service Manual Miscellaneous calibration commands Miscellaneous commands perform miscellaneous calib
40. P1005 PIN 5 5 5 Digital 5 supply 3 P1005 PIN 9 37 5 Display 37V supply 4 U401 PIN 1 Goes low briefly on power up then Microcontroller RESET goes high 5 U401 PIN43 4MHz square wave Controller 4MHz clock 6 0401 PIN 32 Pulse train every 1msec Control from main processor 7 U401 PIN 33 Brief pulse train when front panel Key down data sent to main processor key is pressed Power supply checks Power supply problems can be checked using Table 4 3 Table 4 3 Power supply checks Step Item Component Required Condition Remarks 1 Line fuse Check continuity Remove to check 2 Line voltage 120V 240V as required Check power module position 3 Line power Plugged into live receptacle Check for correct power up sequence power on 4 10144 pin 3 5V 5 5VD referenced to Common 5 10101 pin 7 37 5 37V referenced to Common Di 6 U125 pin 3 15 7V 5 15V referenced to Common 2 7 10119 pin 3 15 7V 5 15V referenced to Common 8 U124 pin 3 5V 5 5VRL referenced to Common 2 106 2TP102 E oO E ge Model 2750 Multimeter Switch System Service Manual Digital circuitry checks Digital circuit problems can be checked using Table 4 4 4 14 Troubleshooting Table 4 4 Digital circuitry checks Step Item Component 1 Power on test 2 U152 pin 16 3 U171 pin 16 4 U194 pin 1 5 U171 pin 4 6 U135 pin 68 7 0135 lines A0 A20
41. Q125 Q126 Q158 K103 U129 U163 Q157 U208 K104 Q171 SSP Solid State Protection HI SSP Sense HI SSP Sense LO SSP I Source DCV Divider DCV and Ohms Switching Front End Bypass AC switching and Gain Ohms I Source Current Shunts A D Mux and Gain Dry circuit clamp No comm link error A No Comm Link error indicates that the front panel processor has ceased communica tion with the main processor which is located on the motherboard This error indicates that there may be a problem with the cable connection from the front panel display or one of the main processor ROMs may require reseating in its socket Check to be sure there is a proper cable connection from the front panel display ROMs may be reseated as follows Turn off the power and disconnect the line cord and all other test leads and cables from the instrument 2 Remove the case cover as outlined in Section 5 3 Find the two firmware ROMs 0156 U157 located on the motherboard These are the only ICs installed in sockets Refer to the component layout drawing at the end of Section 6 for exact locations CAUTION not to push down excessively or you might crack the mother board 4 Carefully push down on each ROM IC to make sure it is properly seated in its socket 5 Connect the line cord and turn on the power If the problem persists additional troubleshooting will be required E oO E
42. VHz input because instrument damage may occur Follow these steps to verify AC voltage accuracy 1 Connect the Model 2750 HI and LO INPUT jacks to the AC voltage calibrator as shown in Figure 1 2 Be sure the INPUTS switch is in the FRONT position Figure 1 2 Connections for Model 2750 AC volts verification Amplifier Connect to Calibrator Note Amplifier required only for 9 700 50kHz output 000000 Model 2750 Front Panel Input l Output HI 4 J tJ tJ CJ 43 O input Shielded Cable Model 2750 Multimeter Switch System Service Manual Performance Verification 1 11 2 Selectthe AC volts function by pressing the ACV key 3 Setthe Model 2750 for the 100mV range make sure that REL is disabled N 4 Source IKHz and 50kHz AC voltages for each of the ranges summarized in d Table 1 3 and make sure the respective Model 2750 readings fall within stated e limits lt O o ED Table 1 3 e CERA ACV reading limits 5 Applied 1kHz Reading Limits 50kHz Reading Limits Range Voltage 1 year 18 C to 28 C 1 year 18 C to 28 C 100mV 100 0000mV 99 910 to 100 090mV 99 830 to 100 170mV 1V 1 000000V 0 99910 to 1 00090V 0 99830 to 1 00170V 10V 10 00000V 9 9910 to 10 0090V 9 98300 to 10 0170V 100V 100 0000V 99 910 to 100 090V 99 830 to 100 170V 750V 700 000V
43. allowed to cool down to ambient temperature before calibration and the cold temperature of the card must be measured and sent as the lt temp gt parameter during calibration NOTE Before calibrating the Model 7700 make sure that power has been removed from the card for at least two hours to allow card circuitry to cool down After turning on the power during the calibration procedure complete the procedure as quickly as possible to minimize card heating that could affect calibration accuracy Example CAL PROT CARD1 STEPO 23 Perform 7700 calibration Model 2750 Multimeter Switch System Service Manual Calibration Reference 21 Remote error reporting Methods to detect and determine the nature of calibration errors are discussed in the fol lowing paragraphs Error summary Table B 5 summarizes Model 2750 calibration errors including error numbers and error messages NOTE Error numbers and error messages are separated by commas All calibration errors will set Bit 3 in the Standard Event Register See the Model 2750 User s Manual Table B 5 Calibration errors Error Number Error Message 400 10 vdc zero error 401 100 vdc zero error 402 10 vdc full scale error 403 10 vdc full scale error 404 100 vdc full scale error 405 100 vdc full scale error 406 100 2 w zero error 407 10k 2 w zero error 408 100k 2 w zero
44. amps fuses 3 5 Replacing non volatile RAM battery 3 6 Replace the battery as follows rra 3 7 Plug in module relay closure count rra 3 8 Closure count commands rra 3 8 Reading relay closure count sr 3 8 Resetting relay closure count rr 3 9 Setting count update interval rra 3 9 Rack mounting u aa ertt re sieur pe 3 10 Rack mount kit uio traer arretara 3 10 Rack mount procedure rra 3 10 Troubleshooting IntrodUucHon o end aa tiers d iecit 4 2 Repair considerations rra 4 2 Power on self test raa 4 3 Frontspanel tests AO 4 3 KR NERI are 4 3 DISP test nietos ep pe 4 3 Principles of operation rra 4 4 lanum M 4 4 Display board eriek an EE A EEaren 4 6 Digital CIECUI qaq nu l iie eee t eb eere 4 7 REUS AAE 4 8 Troubleshooting 5 eritrear 4 13 Display board checks surra 4 13 Power supply checks rrura 4 13 Digital circuitry checks rr 4 14 Analog signal switching states 2222 4 15 No comm link error rru 4 23 Disassembly Introducti eM 5 2 Handling and cleaning rra 5 2 Handling PC boards AAA 5 2 Solder repairs d arrana 5 2 Static sensitive devices ra 5 3 Assembly drawings rrua 5 3 Disassembly procedures rra 5 4 Case Cover removal ran aan 5 4 Motherboard removal rra 5 4 Card cage removal essetis et rearen 5 5 Front panel disassembly rru 5 5 Removing powe
45. as appropriate If your calibrator does not have provisions for turning external sense on and off disconnect the sense leads when external sens ing is to be turned off and connect the sense leads when external sensing is to be turned on 2 Perform the calibration steps summarized in Table 2 8 For each step Set the calibrator to the indicated voltage and make sure the unit is in operate Use the recommended voltage if possible Send the indicated programming command Change the voltage parameter if you are using a different calibration voltage Wait until the Model 2750 completes each step before continuing 2 16 Calibration Model 2750 Multimeter Switch System Service Manual NOTE Ensure the calibrator has settled to the final value You can do so by verifying that the Settled indicator is off or by using the OPC operation complete query Table 2 8 DC voltage calibration programming steps Calibration Parameter Step Calibrator Voltage Calibration Command Range 10V 10 00000V CAL PROT DC STEP3 10 9 to 11 10V 10 00000V CAL PROT DC STEPA 10 9 to 11 100V 100 0000V CAL PROT DC STEPS5 100 90 to 110 Use recommended value where possible Change parameter accordingly if using a different calibrator voltage Resistance calibration Follow these steps for resistance calibration 1 Set the calibrator to the resistance mode and turn on external sensing NOTE Use external sense 4
46. at IkHz 1VAC at SOKHz 10VAC at 1kHz 10VAC at 50kHz 100VAC at 1kHz 100VAC at 50kHz 700VAC at 1kHz 10 00000mV 1kHz 100 0000mV IkHZ 100 0000mV 50kHz 1 000000V 1kHz 1 000000 50kHz 10 00000V 1kHz 10 00000V 50kHz 100 0000V 1kHz 100 0000V 50kHz 700 000V 1kHz CAL PROT AC STEPI CAL PROT AC STEP2 CAL PROT AC STEP3 CAL PROT AC STEPA CAL PROT AC STEPS CAL PROT AC STEP CAL PROT AC STEP7 CAL PROT AC STEPS CAL PROT AC STEPO CAL PROT AC STEPIO Model 2750 Multimeter Switch System Service Manual Calibration 2 19 AC current calibration Follow these steps for AC current calibration 1 Connect the calibrator to the AMPS and INPUT LO terminals of the Model 2750 as shown in Figure 2 3 2 Perform the calibration steps summarized in Table 2 12 For each step Set the calibrator to the indicated current and frequency and make sure the unit is in operate You must use the stated current and frequency Send the indicated programming command Wait until the Model 2750 completes each step before continuing Table 2 12 AC current calibration programming steps Calibration Step Calibrator Current Frequency Calibration Command N 100mA at 1kHz 100 0000mA 1kHz CAL PROT AC STEP1 1 e at 1kHz 1 000000 1kHz CAL PROT AC STEP12 ie 2A at kHz 2 000000A 1kHz CAL PROT AC STEP13 E Programming calibration dates Program the present calibration date and calibratio
47. between any plug in module terminal and chassis ground is listed in the module s specifications Exceeding this value may cause a breakdown in insulation creating a shock hazard When using the front panel terminals simultaneously with plug in modules all cable insulation voltage ratings must equal or exceed the maximum voltage applied to either the front panel terminals or the plug in module terminals Model 2750 verification Perform these tests to verify accuracy using the Model 2750 front panel terminals Verifying DC voltage Check DC voltage accuracy by applying accurate voltages from the DC voltage calibrator to the Model 2750 INPUT jacks and verify that the displayed readings fall within specified limits CAUTION Do not exceed 1000V peak between front terminals INPUT HI and INPUT LO because instrument damage may occur Follow these steps to verify DC voltage accuracy 1 Connect the Model 2750 HI and LO INPUT jacks to the DC voltage calibrator as shown in Figure 1 1 Make sure the INPUTS switch is set to the FRONT position NOTE Use shielded low thermal connections when testing the 100mV and 1V ranges to avoid errors caused by noise or thermal effects Connect the shield to the cal ibrator s output LO terminal Model 2750 Multimeter Switch System Service Manual Performance Verification 1 9 Figure 1 1 Connections for Model 2750 DC volts verification Calibrator Output DC Voltage Model 2750 Front Pan
48. cal prot dc step2 None STEP2 performs the open circuit calibration step in the comprehen sive calibration procedure Disconnect all cables and accessories from the input jacks before sending this command CAL PROT DC STEP2 Perform open circuit calibration CALibration PROTected DC STEP3 Purpose Format Parameters Description Example 5 4 To program the 10 comprehensive calibration step cal prot dc step3 Cal voltage Cal voltage 9 to 11 V STEP3 programs the 10V DC comprehensive calibration step The allowable range of the calibration voltage parameter is from 9 to 11 but 10 is recommended for best results CAL PROT DC STEP3 10 Program 10V step CALibration PROTected DC STEP4 Purpose Format Parameters Description Example To program the 10V DC comprehensive calibration step cal prot dc step4 Cal voltage Cal voltage 9 to 11 V STEPA programs the 10V DC comprehensive calibration step The allowable range of the calibration voltage parameter is from 9 to 11 but 10 is recommended for best results CAL PROT DC STEP4 10 Program 10V step g 3 e oO oO E e oO B 10 Calibration Reference STEP5 Model 2750 Multimeter Switch System Service Manual CALibration PROTected DC STEP5 Purpose Format Parameters Description Example STEPG To program the 100V DC comprehensive calibration step
49. module which can display up to 12 alphanumeric characters and includes the various annunciators and five LED annunciators The display uses a common multiplexing scheme with each character refreshed in sequence U402 and U403 are the drivers for the display characters and annunciators Note that data for the drivers are serially transmitted from the microcontroller MOSI and PC1 Filament voltage for the display is derived from the power supply transformer F1 and F2 The display drivers require 37VDC and 5VDC which are supplied by U144 4 5 VD 0101 37V Key matrix The front panel keys S401 S430 are organized into a row column matrix to minimize the number of microcontroller peripheral lines required to read the keyboard A key is read by strobing the columns and reading all rows for each strobed column Key down data is interpreted by the display microcontroller and sent back to the main microprocessor using proprietary encoding schemes Digital circuitry Refer to Figure 4 2 for the following discussion on digital circuitry Microprocessor U135 is a 68332 microprocessor that oversees all operating aspects of the instrument The MPU has a 16 bit data bus and provides a 21 bit address bus It also has parallel and serial ports for controlling various circuits For example the RXD and TXD lines are used for the RS 232 interface The MPU clock frequency of 19 92MHz is controlled by crystal Y101 MPU RESET is performed mo
50. panel INPUTS switch is set to the REAR position 3 Set the calibrator for 4 wire resistance with external sense on 4 Select the Model 2750 4 wire resistance function by pressing Q4 key Close Channel 1 by pressing the CLOSE key then ENTER for SINGLE channel and keying in 101 5 Setthe Model 2750 for the dry circuit resistance function by pressing SHIFT then DRYCKT J e e I t 2 EA e E Figure 1 15 Connections for Model 7700 dry circuit resistance verification CH1 Model 7700 Sense HI OI Resistance Calibrator rr etetea nd T A Output HI C Ol C de 2 C SENSE p C OHMS 4 WIRI A m GR c Q Ak e Sense LO CH11 Note Use shielded low thermal cables to minimize noise 1 30 Performance Verification Model 2750 Multimeter Switch System Service Manual 6 Set the Model 2750 for the 10 range and make sure the FILTER is on If previ ously disabled enable OCOMP offset compensated ohms by pressing SHIFT then OCOMP Use OCOMP for 1 1
51. perform them Otherwise they should be performed only by service personnel Service personnel are trained to work on live circuits and perform safe installations and repairs of prod ucts Only properly trained service personnel may perform installation and service procedures Keithley products are designed for use with electrical signals that are rated Installation Category I and Installation Category II as described in the International Electrotechnical Commission IEC Standard IEC 60664 Most measurement control and data I O signals are Installation Category I and must not be directly connected to mains voltage or to voltage sources with high transient over voltages Installa tion Category II connections require protection for high transient over voltages often associated with lo cal AC mains connections The user should assume all measurement control and data I O connections are for connection to Category I sources unless otherwise marked or described in the Manual Exercise extreme caution when a shock hazard is present Lethal voltage may be present on cable con nector jacks or test fixtures The American National Standards Institute ANSI states that a shock haz ard exists when voltage levels greater than 30V RMS 42 4V peak or 60VDC are present A good safety practice is to expect that hazardous voltage is present in any unknown circuit before measuring Users of this product must be protected from electric shock at all times The
52. polling to obtain the status byte then test bit 2 to see if it is set If the EAV bit is set an error has occurred and you can use the SYST ERR query to read the error and at the same time clear the EAV bit in the sta tus byte Bit 3 of the Standard Event Register will also be set by a calibration error Generating an SRQ on error To program the instrument to generate an IEEE 488 bus SRQ when an error occurs send the following command SRE 4 This command will enable SRQ when the EAV bit is set You can then read the status byte and error queue as outlined above to check for errors and to determine the exact nature of the error Detecting calibration step completion When sending remote calibration commands you must wait until the instrument com pletes the current operation before sending a command You can use either OPC or OPC to help determine when each calibration step is completed Using the OPC query With the OPC operation complete query the instrument will place an ASCII 1 in the output queue when it has completed each step To determine when the OPC response is ready do the following 1 Repeatedly test the MAV Message Available bit bit 4 in the status byte and wait until it is set You can request the status byte by using the STB query or by serial polling 2 When MAV is set a message is available in the output queue and you can read the output queue and test for an ASCII 1 3 After reading the
53. responsible body must en sure that users are prevented access and or insulated from every connection point In some cases con nections must be exposed to potential human contact Product users in these circumstances must be trained to protect themselves from the risk of electric shock If the circuit is capable of operating at or above 1000 volts no conductive part of the circuit may be exposed Do not connect switching cards directly to unlimited power circuits They are intended to be used with impedance limited sources NEVER connect switching cards directly to AC mains When connecting sources to switching cards install protective devices to limit fault current and voltage to the card Before operating an instrument make sure the line cord is connected to a properly grounded power re ceptacle Inspect the connecting cables test leads and jumpers for possible wear cracks or breaks be fore each use When installing equipment where access to the main power cord is restricted such as rack mounting a separate main input power disconnect device must be provided in close proximity to the equipment and within easy reach of the operator For maximum safety do not touch the product test cables or any other instruments while power is applied to the circuit under test ALWAYS remove power from the entire test system and discharge any capacitors before connecting or disconnecting cables or jumpers installing or removing switching cards
54. summary B 2 Component layouts 6 3 Connections AC volts calibration 2 12 DC and AC amps calibration 2 11 DC volts and ohms calibration 2 8 Input terminal wire 5 6 low thermal short 2 7 manufacturing calibration 2 22 Model 2700 AC current verification 1 13 Model 2700 AC volts verification 1 10 Model 2700 DC current verification 1 12 Model 2700 DC volts verification 1 9 Model 2700 frequency verification 1 20 Model 2700 resistance verification 100 range 1 15 Model 2700 resistance verification 100Q to 1OMQ ranges 1 14 1 17 1 29 Model 7700 AC current verification 1 25 Model 7700 AC volts verification 1 22 Model 7700 DC current verification 1 24 Model 7700 DC volts verification 1 21 Model 7700 frequency verification 1 34 Model 7700 ratio and average verification 1 35 Model 7700 resistance verification 100MQ range 1 27 Model 7700 resistance verification 100Q to 10 ranges 1 27 Model 7700 thermocouple temperature verification 1 31 Power module wire 5 7 dB characteristics accuracy A 13 dBm characteristics accuracy A 13 DC calibration commands B 8 DC characteristics accuracy A 12 DC current A 14 A 15 verifying Model 2700 1 11 verifying Model 7700 1 24 DC voltage A 14 A 15 Verifying Model 2700 1 8 verifying Model 7700 1 21 DCA signal multiplexing and gain 4 21 DCV signal multiplexing and gain 4 21 DCV signal switching 4 15 derating factors additional A 14 Digital circuitry 4 7 block diagram 4 6 Digit
55. temperature verification procedures are provided below for those who wish to separately verify temperature accuracy Thermocouple temperature 1 Connect the DC voltage calibrator output terminals and ice point reference to the Model 7700 CH1 H and L INPUT terminals using low thermal shielded connec tions as shown in Figure 1 16 Figure 1 16 Connections for Model 7700 thermocouple temperature verification Twisted SEN Thermocouple Wire 7 Calibrator Output DC Voltage worse dn ane Eide Output leeeeeoc V HI OO t CLE CJ Ooo OGO Cj CJ CJ e ooo oo 9 99 000 000 OOO OC d EGOZ Output LO CH21 2 g CHIT CH12 CH13 CH14 CHIS CHI Model 7700 Low Thermal Copper Connection Make HI and LO Connections in Ice Bath I Notes This setup and reading limits table does not include errors from ice point thermocouple wire and connections HI and LO connections from the calibrator and Model 7700 must be electrically isolated Ice Bath from each other J e e lt t 2
56. warmup period Using the correct line voltage Using the proper calibration equipment Using the specified reading limits Environmental conditions Conduct your performance verification procedures in a test environment that has Anambient temperature of 18 to 28 C 65 to 82 F Arelative humidity of less than 8096 unless otherwise noted Warmup period Allow the Model 2750 to warm up for at least two hours before conducting the verification procedures If the instrument has been subjected to temperature extremes those outside the ranges stated above allow additional time for the instrument s internal temperature to stabilize Typically allow one extra hour to stabilize a unit that is 10 C 18 F outside the specified temperature range Also allow the test equipment to warm up for the minimum time specified by the manu facturer Line power The Model 2750 requires a line voltage of 100V 120V 220V 240V 10 and a line fre quency of 45Hz to 66Hz or 360Hz to 440Hz Note that the line frequency is automatically sensed at powerup but the line voltage must be manually set to either 100V 120V or 220V 240V as described in Section 3 1 4 Performance Verification Model 2750 Multimeter Switch System Service Manual Recommended test equipment Table 1 1 summarizes recommended verification equipment You can use alternate equip ment as long as that equipment has specifications at least as good as those listed in Ta
57. while the DCA signal is routed directly to the A D MUX amp Gain circuit Signal switching Signal switching for DCV and OHMS is done by the DCV amp Ohms Switching circuit FETs Q113 Q104 and Q108 connect the DCV or ohms signal to the X1 buffer U113 For offset compensated ohms and all dry circuit ohms measurements the signal is routed directly to the A D mux by Q106 bypassing U113 Note that the reference current for OHMS is generated by the Ohms I Source circuit For 4 wire ohms measurements SENSE LO is connected to U163 Signal switching and gain for ACV FREQ and ACA is done by the AC Switching amp Gain circuit which is primarily made up of K102 U102 U103 U105 U112 U118 U111 U110 and U117 Note that U111 is used for frequency adjustment The states of these analog switches vary from unit to unit Model 2750 Multimeter Switch System Service Manual Troubleshooting 4 11 Multiplexer and A D converter All input signals except FREQ are routed to the A D MUX amp Gain circuit The multi plexer U163 switches the various signals for measurement In addition to the input sig nal the multiplexer also switches among reference and zero signals at various phases of the measurement cycle When the input signal is selected by the MUX it is amplified by U132 and U166 Gain is controlled by switches in U129 and associated resistors The multiplexed signals of the measurement cycle are routed to the A D Converter U165 w
58. 0 00106kQ to 100kQ 100kQ 99 9890 to 100 0110kQ to IMQ 1M 0 999890 to 1 000110MQ to MQ 10MQ 10MQ 9 99590 to 10 00410MQ to MQ 100MQ 100MQ 99 5770 to 100 4230MQ to MQ Enable OCOMP for 1Q 10Q and 100Q ranges Calculate limits based on actual calibration resistance values and Model 2750 one year resistance accuracy specifications See Verification limits Verifying dry circuit resistance Check the dry circuit resistance function by connecting accurate resistance values to the Model 2750 and verifying that its resistance readings are within the specified limits CAUTION not apply more than 300V between the 7700 plug in module INPUT or SENSE H and L terminal or between any adjacent chan nels or instrument damage could occur Follow these steps to verify dry circuit resistance accuracy 1 Using shielded Teflon or equivalent cables in a 4 wire configuration connect the Model 7700 CH1 H and L INPUT terminals and CH11 H and L SENSE terminals to the calibrator as shown in Figure 1 15 NOTE The range can tolerate 80 of range 0 80 lead resistance Ensure that relay and cable connections have lt 0 80 of resistance before verifying the 10 range Model 2750 Multimeter Switch System Service Manual Performance Verification 1 29 2 Install the Model 7700 in Slot 1 of the Model 2750 then turn on the power and allow the unit to warm up for two hours before proceeding Be sure the front
59. 00 1000 and 1kQ range verification Enable line sync press SHIFT then LSYNC 7 Recalculate reading limits based on actual calibrator resistance values NOTE Maximum reading rate for 1kQ dry circuit is two readings per second 8 Source the nominal full scale resistance values for the 1Q 1kQ ranges summarized in Table 1 15 and verify that the readings are within calculated limits Table 1 15 Limits for plug in module dry circuit resistance verification Nominal Nominal Reading Limits O Range Resistance 1 year 18 C to 28 C Recalculated Limits 1Q 10 0 999860 to 1 000140Q to Q 10Q 10Q 9 99860 to 10 00140Q to Q 100 2 1000 99 9820 to 100 01800 to Q IkQ IkQ 0 999510 to 1 000490kQ to kQ Enable OCOMP offset compensated ohms when testing 10 100 1000 and 1kQ ranges Calculate limits based on actual calibration resistance values and Model 2750 one year resistance accuracy specifications See Verification limits Model 2750 Multimeter Switch System Service Manual Performance Verification 1 31 Verifying temperature Thermocouple thermistor and RTD temperature readings are derived from DC volts and resistance measurements respectively For that reason it is not necessary to independently verify the accuracy of temperature measurements As long as the DC volts and resistance functions meet or exceed specifications temperature function accuracy is automatically verified However
60. 0000 mV 0 1 uV 90 Days 0 35 0 03 0 05 0 03 0 11 0 05 0 6 0 08 4 0 0 5 1 000000 V 1 0 uV 10 00000 V 10 uv 1Year 0 35 0 03 0 06 0 03 0 12 0 05 0 6 0 08 4 0 0 5 100 0000 V 100 UN 750 000 V 1 0 uV Temp Coeff C3 0 035 003 0 005 003 0 006 005 0 01 006 0 03 01 3Hz 10Hz 10 Hz 5 kHz Current 1 000000 A 10 pA 90 Day 1Yr 0 30 0 04 0 10 0 04 3 00000 AR 10 pA 0 35 0 06 0 15 0 06 Temp Coeff C 0 035 0 006 0 015 0 006 3 Hz 500 kHz 333 ms 2 us Frequency 100mV 0 333ppm DO Day 1Yr 100 ppm 0 333 ppm SLOW 1s gate and Period to 3 33 ppm 100 ppm 3 33 ppm MED 100ms gate 750 V 333 ppm 100 ppm 33 3 ppm FAST 10ms gate Additional Uncertainty of reading Low Frequency Uncertainty MED FAST 20Hz 30Hz 0 3 30Hz 50Hz 0 50Hz 100Hz 0 1 0 100 Hz 200 Hz 0 0 18 200 Hz 300 Hz 0 0 10 gt 300 Hz 0 0 CREST FACTOR 5 1 2 2 3 3 4 4 5 Additional Uncertainty 0 05 0 15 030 040 Max Fundamental Freq 50kHz 50kHz 3kHz 1kHz gt 6 Specifications AC MEASUREMENT CHARACTERISTICS AC Volts MEASUREMENT METHOD AC coupled True RM S INPUT IMPEDANCE 1M Q 2 by lt 100pF INPUT PROTECTION 1000Vp or 400VDC 300Vrms with plug in modules AC Current MEASUREMENT METHOD AC coupled True RM S SHUNT RESISTANCE 0 10 BURDEN VOLTAGE 1A lt 0 5Vrms lt 1 5Vrms Add 1 5Vrms when used with plug in modules INPUT PROTECTION 3A 250V fuse Frequency and Period MEASUREMENT
61. 00A 2 9817 to 3 0183A Tf the Fluke 5725A amplifier is not available apply 2 2A from the calibrator Reading limits for 2 2A are 2 1949 to 2 2051A 1 14 Performance Verification Model 2750 Multimeter Switch System Service Manual Verifying normal resistance Check the normal resistance function by connecting accurate resistance values to the Model 2750 and verifying that its resistance readings are within the specified limits CAUTION Do not apply more than 1000V peak between front terminals INPUT HI and LO or more than 350V peak between SENSE HI and LO or instrument damage could occur Follow these steps to verify resistance accuracy 1 Using shielded Teflon insulated or equivalent cables in a 4 wire configuration connect the Model 2750 INPUT and SENSE jacks to the calibrator as shown in Figure 1 5 Be sure the INPUTS switch is in the FRONT position 2 Set the calibrator for 4 wire resistance with external sense on Figure 1 5 Connections for Model 2750 resistance verification to ranges Sense HI Resistance Calibrator Model 2750 Front Panel Input Output LO LO Note Use shielded low thermal cables to minimize noise Enable or disable calibrator external sense as indicated in procedure Model 2750 Multimeter Switch System Service Manual Performance Verification 1 15 3 Select the Model 2750 4 wire res
62. 00Q range steps then save cali bration using CAL PROT SAVE Uncalibrated ranges will retain previous cali bration constants and can be verified as discussed in Section 1 Short and open calibration 1 Connect the Model 8610 low thermal short to the instrument INPUT and SENSE terminals as shown in Figure 2 1 Make sure the INPUTS button is not pressed in so that the front inputs are active Wait at least three minutes before proceeding to allow for thermal equilibrium NOTE sure to connect the low thermal short properly to the LO and SENSE ter minals Keep drafts away from low thermal connections to avoid thermal drift which could affect calibration accuracy 2 Sendthe following command CAL PROT DC STEP1 3 After the Model 2750 completes this step remove the low thermal short and then send this command CAL PROT DC STEP2 gt e N N zu gt NOTE sure to minimize movement near front input terminals Excessive movements can cause capacitive coupling errors which could affect calibration accuracy DC volts calibration After the front panel short and open steps do the following 1 Connect the calibrator to the Model 2750 as shown in Figure 2 2 Allow three min utes for thermal equilibrium NOTE Although 4 wire connections are shown the sense leads are connected and dis connected at various points in this procedure by turning calibrator external sense on or off
63. 0V TRIGGERING AND MEMORY Window Filter Sensitivity 0 01 0 1 1 10 or Full scale of range none Reading Hold Sensitivity 0 01 0 1 96 1 or 10 of reading Trigger Delay Oto 99 hrs 1ms step size External Trigger Delay lt ms External Trigger Jitter lt 5005 Memory Size 110 000 readings MATH FUNCTIONS Rel Min M ax Average Std Dev Peak to Peak of stored reading Limit Test 96 1 x and mX b with user defined units dis played REMOTE INTERFACE GPIB IEEE 488 2 and RS 232C SCPI Standard Commands for Programmable Instruments LabVIEW Drivers ACCESSORIES SUPPLIED M odel 1751 Safety Test Leads User Manual Service M anual ACCESSORIES AVAILABLE 4288 7 Rack Mount Rear Support Kit 77XX 904A Module Manual Specifications are subject to change without notice A 8 Specifications 7700 20 channd Differential Multiplexer w Automatic CJ C GENERAL 20 CHANNELS 20 channels of 2 pole relay input All channels configurable to 4 pole 2 CHANNELS 2 channels of current only input RELAY TYPE Latching electromechanical ACTUATION TIME Sms CAPABILITIES CHANNELS 1 20 Multiplex one of 20 2 pole or one of 10 4 pole signals into DMM CHANNELS 21 22 Multiplex one of 2 2 pole current signals into DMM INPUTS MAXIMUM SIGNAL LEVEL e _ Channels 1 20 300V DC or rms 1A Card Input m switched 60W 125VA maximum LO o Channels 21 22 60V DC or 30V rms 3A switched
64. 1 10 0 999820 to 1 000180 2 to Q 10Q 10Q 9 99880 to 10 00120Q to Q 1000 1000 99 9880 to 100 0120Q to Q IKU 1kQ 0 999894 to 1 000106kQ to 10k 10k 9 99894 to 10 00106kQ to kQ 100kQ 100kQ 99 9890 to 100 01 10kQ to IMQ IMQ 0 999890 to 1 0001 1OMQ to MQ 10MQ 10MQ 9 99590 to 10 00410MQ to MQ 100MQ 100MQ 99 7970 to 100 2030MQ to MQ Enable OCOMP offset compensated ohms when testing 1Q 100 and 1000 ranges Calculate limits based on actual calibration resistance values and Model 2750 one year resistance accuracy specifications See Verification limits Verifying dry circuit resistance Check the dry circuit resistance function by connecting accurate resistance values to the Model 2750 and verifying that its resistance readings are within the specified limits CAUTION Do not apply more than 1000V peak between front terminals INPUT HI and LO or more than 350V peak between SENSE HI and LO or instrument damage could occur Follow these steps to verify dry circuit resistance accuracy 1 Using shielded Teflon insulated or equivalent cables in a 4 wire configuration connect the Model 2750 INPUT and SENSE jacks to the calibrator as shown in Figure 1 7 Be sure the INPUTS switch is in the FRONT position Model 2750 Multimeter Switch System Service Manual Performance Verification 1 17 Figure 1 7 Connections for Model 2750 dry circuit resistance verification Sense HI Resistance Calibrator
65. 1 10 mA 20 80 40 80 40 100 40 8 1 C Resistance 10 00000 Q 10 1 20mv 25 40 80 40 100 40 8 1 C 100 0000 Q 100 uQ 100 20mv 25 40 90 40 140440 8 1 C 1 000000 kQ 1 mQ 10 pA 20mv 25 90 180490 400 90 8 1 C Continuity QW 1000 100 m 1mA 122 V 40 100 100 100 100 100 8 1 Current 20 00000 mA 10 nA 02 V 60 30 300 80 500 80 50 5 C 100 0000 mA 100 nA 01V 100 300 300 800 500 800 50 50 1 000000 10 pA 0 5V 200 430 500 80 800 80 50 5 C 3 000000 A 10 pA 15V 1000 15 1200 40 1200 40 50 5 C Channel Ratio 19 Ratio Accuracy Accuracy of selected Channel Range Accuracy of Paired Channel Range Channel Average 10 Average Accuracy Accuracy of selected Channel Range Accuracy of Paired Channel Range TEMPERATURE 19 Displayed in C F or K Exclusive of probe errors Thermocouples Accuracy based on ITS 90 Type Range Resolution ReferenceJunction 200to 4760 C 200 to 1372 C 200 to 1300 C 200to 400 200 to 1000 C Oto 1768 C Oto 1768 C 350 to 1820 C 4 WireRTD EO OSO rri 2 0 001 C 0 001 C 0 001 C 0 001 C 0 001 C OEC 01 C 0 1 C Temperature Coefficient 0 18 C amp 28 50 C 90 Day 1 Year 23 C 5 C Relative to UsingCJC Simulated from Plug In Module 0 2 C 1 0 0 2 C 1 0 C 0 2 C 10 0 2 C 1 0 C 0 2 C 10 0 6 C 1 8 C 0 6 C 1 8 C 0 6 C 1 8 C 0 03 C C 0 03
66. 1 11 Plug in module ACV reading limits ACV Applied AC 1kHz Reading Limits 50kHz Reading Limits Range Voltage 1 year 18 C to 28 C 1 year 18 C to 28 C 100mV 100 0000mV 99 910 to 100 090mV 99 830 to 100 170mV 1V 1 000000V 0 99910 to 1 00090V 0 99830 to 1 00170V 10V 10 00000V 9 9910 to 10 0090V 9 98300 to 10 0170V 100V 100 0000V 99 910 to 100 090V 99 830 to 100 170V 750V 300 000V 299 60 to 300 40V 299 27 to 300 73V Tf the 5725A amplifier is not available change the 300V 9 50kHz step to 220V 50kHz Reading limits for 220V 50kHz 219 36 to 220 64V 1 24 Performance Verification Model 2750 Multimeter Switch System Service Manual Verifying DC current Check DC current accuracy by applying accurate DC currents from the DC current cali brator to the input terminals of the Model 7700 and verify that the displayed readings fall within specified limits Follow these steps to verify DC current accuracy 1 Figure 1 11 Connect the Model 7700 CH21 H and L terminals to the calibrator as shown in Figure 1 11 Install the Model 7700 in Slot 1 of the Model 2750 then turn on the power and allow the unit to warm up for two hours before proceeding Be sure the front panel INPUTS switch is set to the REAR position Select the DC current measurement function by pressing the DCI key Set the Model 2750 for the 20mA range Close Channel 21 by pressing the CLOSE key then ENTER for SINGLE channel and keying in 1
67. 1 terminals to the calibrator as shown in Figure 1 14 9 Disable external sense on the calibrator 10 Set the Model 2750 for the 100MQ range 11 Source a nominal 100MQ resistance value and verify that the reading is within calculated limits for the 1OOMQ range 12 Press the OPEN key to open Channel 1 Figure 1 14 Connections for Model 7700 resistance verification 100 range CH1 Model 7700 n Calibrator Output 2 wire Resistance Note Use shielded cables to minimize noise Disable calibrator external sense mode J e e lt t 2 E 1 28 Performance Verification Model 2750 Multimeter Switch System Service Manual Table 1 14 Limits for plug in module normal resistance verification Nominal Nominal reading limits O Range resistance 1 18 C to 28 C Recalculated limits 1Q 10 0 999820 to 1 000180 2 to Q 10Q 100 9 99880 to 10 00120Q to Q 1000 1000 99 9880 to 100 0120 to Q IKU 1kQ 0 999894 to 1 000106kQ to kQ 10k 10k 9 99894 to 1
68. 100 to 100 0900mA 1A 1 000000A 0 999160 to 1 000840A 3A 3 000000A 2 99628 to 3 00372A Source positive and negative currents with values shown Tf the Fluke 5725 amplifier is not available apply 2 2A from calibrator Reading limits for 2 2A input are 2 197240 to 2 202760A Model 2750 Multimeter Switch System Service Manual Performance Verification 1 13 Verifying AC current Check AC current accuracy by applying accurate AC voltage current at specific frequen cies from the AC current calibrator to the Model 2750 input and verify that the displayed readings fall within specified limits Follow these steps to verify AC current 1 Connect the Model 2750 AMPS and INPUT LO jacks to the calibrator as shown in Figure 1 4 Be sure the INPUTS switch is in the FRONT position 2 Select the AC current function by pressing the ACI key N 1 e lt t 2 5 Figure 1 4 Connections for Model 2750 AC current verification Calibrator Output AC Current Model 2750 Front Panel OOU OOU 3 Setthe Model 2750 for the 1A range 4 Source and full scale AC currents as summarized in Table 1 5 and verify that the readings are within stated limits Table 1 5 ACI limits ACV Range Applied AC Voltage Reading Limits 1kHz 1 year 18 C to 28 C 1A 1 000000A 0 99860 to 1 00140A 3A 3 000
69. 131 E oO E ge 4 6 Troubleshooting Model 2750 Multimeter Switch System Service Manual Display board Display board components are shown in the digital circuitry block diagram in Figure 4 2 Figure 4 2 Digital circuitry block diagram BAT Battery BT100 Back Y103 Control Realtime Clock U171 NVRAM d U1 Ge 52 U136 t U156 U157 U164 U193 Line Sync Jae D Control ADTX Analog ura EEE 68332 Circuitry U180 ADTS uP U181 See Figure 4 3 U182 U135 0183 ADRXB U184 U186 TRIG IN Trigger U146 TRIG OUT Data IN IEEE 488 K Bus Data OUT U158 U160 U161 Trigger Link ioi Digital OUT Digital Output U188 U189 Digital Digital Input VO U146 U191 U192 Model 2750 Multimeter Switch System Service Manual Troubleshooting 4 7 Microcontroller U401 is the display board microcontroller that controls the display and interprets key data The microcontroller uses three internal peripheral I O ports for the various control and read functions Display data is serially transmitted to the microcontroller from the digital section via the TXB line to the microcontroller RDI terminal In a similar manner key data is serially sent back to the digital section through the RXB line via TDO The 4MHz clock for the micro controller is generated by crystal Y401 Display DS401 is the display
70. 15K 1 1 4W METAL FILM R 391 15K R120 R130 R154 R183 R186 R191 RES 100K 1 1OOMW THICK FILM R 418 100K R193 R315 R121 R391 R395 R352 RES 100K 1 1OOMW THICK FILM R 418 100K R123 RES 73 2K 1 100MW THICK FILM R 418 73 2K R124 R150 R211 R240 R258 R268 RES 49 9K 1 100MW THICK FILM R 418 49 9K R271 R125 R230 R232 R163 R305 RES 49 9K 1 100MW THICK FILM R 418 49 9K R126 R128 R185 R275 RES 475 1 1 4W METAL FILM R 391 475 R127 R144 RES 2 49K 1 1 4W METAL FILM R 391 2 49K R129 RES 215 1 100MW THICK FILM R 418 215 R131 R136 R138 R141 R161 RES 100 1 1 4W METAL FILM R 391 100 R178 R180 R184 R135 RES 33 2K 1 100MW THICK FILM R 418 33 2K R142 RES 10 5 125MW METAL FILM R 375 10 R143 R152 R164 R242 R253 RES 100K 1 1 4W METAL FILM R 391 100K R145 R156 R196 R213 R257 R270 RES 100 1 100MW THICK FILM R 418 100 R300 R303 R146 RES 1 1M 5 125MW METAL FILM R 375 1 1M R147 RES 732 1 1000MW THICK FILM R 418 732K R148 R301 R356 R372 RES 499 1 1 4W METAL FILM R 391 499 R149 R151 RES 1 5K 1 1000MW THICK FILM R 418 1 5K R153 RES NET 3 6K MICRO DIVIDER TF 246 1 R155 R169 R201 R214 R218 R229 RES 4 75K 1 100MW THICK FILM R 418 4 75K R244 R351 Model 2750 Multimeter Switch System Service Manual Replaceable Parts 6 7 Table 6 1 continued Model 2750 motherboard parts list Circuit Designation Description Keithley Part No R157 R243 RES 499 1 1000MW
71. 161 IC OCTAL INTER BUS TRANS 75161 IC 647 U163 IC 8 CHAN ANA MULTIPLEXER IC 844 DG408DY U165 PROGRAMMED ROM 2000 802A02 U168 U183 U184 IC DUAL D TYPE F F 74HC74 IC 773 U170 IC 2 INPUT OR GATE IC 1206 U171 IC PHANTOM TIME CHIP IC 1317 U175 IC DUAL HIGH CMR SPEED OPTO IC 588 HCPL 2631 U182 IC RETRIG MULTIVIB 74HC123AM IC 788 U187 INTERGRATED CIRCUIT SMT IC 1423 U188 U189 IC PROTECTED QUAD POWER DRIVERS IC 1212 Model 2750 Multimeter Switch System Service Manual Table 6 1 continued Model 2750 motherboard parts list Replaceable Parts 6 11 Circuit Designation Description Keithley Part No U192 IC 2 INPUT AND GATE IC 1140 U194 IC CONTROLLER WITH MONITOR IC 1424 U195 IC 3 TO 8 LINE DECODER IC 1378 U206 U162 IC PRECISION BIFET OPAMP IC 1194 VR100 VR101 VR102 DIODE ZENER 6 0V BZX84B6V2 DZ 87 VR103 VR104 DIODE ZENER 6 8V MMSZ5235BT1 DZ 100 VR105 VR106 DIODE ZENER 11V MMSZ11T1 DZ 103 VR107 VR108 DIODE ZENER 4 3V BZX84C4V3 DZ 85 VR109 DIODE ZENER 17V MMBZ5247BL DZ 104 VR110 VR111 DIODE ZENER 10V MMSZ5240B DZ 99 VR112 VR113 VR116 VR117 DIODE ZENER 6 2V MMSZ6V2 DZ 97 VR119 VR120 VR114 VR115 DIODE ZENER 3 3V CMPZ4684 DZ 115 Y101 Y103 CRYSTAL FSM327 CR 41 Y102 OSCILLATOR HIGH SPEED CMOS CR 37 12MHZ Order current firmware revision for example 01 17 oO oO ee Z 6 12 Replaceable Parts Model 2750 Mu
72. 21 Source positive and negative full scale currents for each of the ranges listed in Table 1 12 and verify that the readings for each range are within stated limits Press the OPEN key to open Channel 21 Connections for Model 7700 DC current verification Model 7700 Calibrator Output DC Current Output HI 4 OO GO GOO Q oo Output LO Note Be sure calibrator is set for normal current output Model 2750 Multimeter Switch System Service Manual Table 1 12 Plug in module DCI limits Performance Verification 1 25 DCI Range 20mA 100mA lA 3A Applied DC Current 20 0000mA 100 0000mA 1 000000A 3 000000A Reading Limits 1 year 18 C to 28 C 19 89960 to 20 01040mA 99 9100 to 100 0900mA 0 999160 to 1 000840A 2 99628 to 3 00372A Source positive and negative currents with values shown Tf the Fluke 5725 amplifier is not available apply 2 2A from calibrator Reading limits for 2 2A input are 2 197240 to 2 202760A V
73. 3dBm 0 00032dBm dBm and dB for other voltage inputs can be calculated in exactly the same manner using pertinent specifications ranges and reference impedances Calculating dB characteristics accuracy The relationship between voltage and dB is as follows Vin VREF dB 20 log As an example of how to calculate the actual readings limits for dB with a user defined VREF of 10V you must calculate the voltage accuracy and apply it to the above equation To calculate a 60dB measurement assume 10mV RMS for a VREF of 10V Using the 100mV range one year 10Hz 20kHz frequency band and SLOW rate the voltage limits are as follows 0 06 of reading 0 03 of range 0 0006 x 10mV 0 0003 x 100mV 6uV 36u V Accuracy M odel 2750 Multimeter Switch System Service M anual Specifications 11 Thus the actual reading accuracy 15 10 36mV or 10 036mV to 9 964mV Applying the voltage reading accuracy into the dB equation yields 10 036mV dBm 201og 15 59 96879dB b 9964mV _ dBm ikera 60 03133dB Thus the actual reading accuracy is 60dB 0 031213dB to 60dB 0 031326dB dBm and dB for other voltage inputs can be calculated in exactly the same manner using pertinent specifications ranges and other reference voltages Additional derating factors In some cases additional derating factors must be applied to calculate certain accuracy values For example
74. 4 4 in Section 4 to determine if the battery requires replacement Remove the Model 2750 top cover using the disassembly procedures in Section 5 Locate battery BT100 using the motherboard component layout drawing at the end of Section 6 De solder the battery from the top side of the circuit board Install a new battery Keithley part number BA 51 taking care to observe proper polarity Solder the battery connection to the circuit board using organic OA based flux solder After soldering remove all flux using a foam tipped swab or brush dipped in pure water Blow dry the board with dry nitrogen gas then allow the board to dry for several hours in a 50 C low humidity environment before use Reinstall the top cover by following the disassembly procedures in Section 5 in reverse order oO E 3 oO E E e oO 3 8 Routine Maintenance Model 2750 Multimeter Switch System Service Manual Plug in module relay closure count The Model 2750 keeps an internal count of the number of times each module relay has been closed This count will help you determine if and when any relays require replace ment see module contact life specifications The count can be read or reset only via remote as outlined below Closure count commands Table 3 2 summarizes closure count commands Table 3 2 Closure count commands Command Description ROUTe Route subsystem CLOSe Path to CLOSe commands COUN
75. 700 verification test procedures include DC volts AC volts DC current AC current Resistance Temperature Frequency Ratio and average Test considerations When performing the verification procedures Be sure to restore factory defaults as outlined above Make sure the equipment is properly warmed up and connected to the correct input terminals Also make sure that the INPUTS switch is in the correct position Do not use autoranging for any verification tests because autorange hysteresis may cause the Model 2750 to be on an incorrect range For each test signal you must manually set the correct range for the Model 2750 using the range keys Make sure the calibrator is in operate before you verify each measurement Always let the source signal settle before taking a reading 1 8 Performance Verification Model 2750 Multimeter Switch System Service Manual WARNING Observe the following safety precautions when performing these tests Some of the procedures in this section may expose you to danger ous voltages Use standard safety precautions when such danger ous voltages are encountered to avoid personal injury or death caused by electric shock For the front panel terminals only the maximum common mode voltage voltage between INPUT LO and chassis ground is 500V peak Exceeding this value may cause a breakdown in insulation creating a shock hazard e For the plug in modules the maximum common mode voltage voltage
76. 8K 1 IW THICK FILM R 418 69 8K R10 R11 R12 RES 4 7K 5 125MW METAL FILM R 375 4 7K R108 R109 R110 R111 R3 R150 RES 1 100MW THICK FILM R 418 1K R13 R14 RES 3 01K 1 125MW METAL FILM R 391 3 01K R15 R54 R58 R59 RES 4 22K 1 125MW METAL FILM R 391 4 22K R2 RES 10K 1 100MW THICK FILM R 418 10K R4 R5 R6 R7 RES 2 21K 1 125MW METAL FILM R 391 2 21K R8 RES 1K 5 125MW METAL FILM R 375 1K R9 RES 1K 5 125MW METAL FILM R 375 1K R55 R56 R57 RES 470 5 125MW METAL FILM R 375 470 oO oO O E m 77 6 16 Replaceable Parts Table 6 5 continued Model 7700 module parts list Model 2750 Multimeter Switch System Service Manual Circuit Designation Description Keithley Part No R60 R61 RES 4 22K 1 125MW METAL FILM R 391 4 22K R62 R63 RES 137 1 125MW METAL FILM R 391 137 R64 R65 R66 R67 R68 R69 R70 RES 499 1 100MW THICK FILM R 418 499 R71 101 110 122 CONN 4 PIN JOLO BB 125 04 115 4 121 CONN 6 PIN TE 115 6 U1 U2 U3 U4 U8 IC 8 STAGE SHIFT STORE MC14094BD IC 772 U11 U12 U13 U15 U17 U18 IC CENTIGRADE TEMP SENSOR IC 906 LM35DM 014 RETRIG MULTIVIB 74HC123AM IC 788 U16 IC 2 5 CASCADABLE SERIAL EEPROM LSI 212 U24 IC QUAD 2 IN AND 74 08 IC 837 U6 IC 8 CHAN ANA MULTIPLEXER IC 844 DG408DY U7 U25 IC POS NAND GATES INV 74HCT14 IC 656 U9 U10 IC DUAL OPTO IC 1358 TOP CO
77. 9 R234 RES 5 11K 1 1000MW THICK FILM R 418 5 11K R236 RES 700 196 3W FOIL R 449 700 R241 RES 34K 196 100MW THICK FILM R 418 34K R246 RES 82 5 1 100MW THICK FILM R 418 82 5 R248 R261 R294 R295 R331 R332 RES 100 1 100MW THICK FILM R 418 100 R227 R364 R249 RES 4 02 1 1000MW THICK FILM R 418 4 02K oO oO O E m 77 6 8 Replaceable Parts Table 6 1 continued Model 2750 motherboard parts list Model 2750 Multimeter Switch System Service Manual Circuit Designation Description Keithley Part No R251 R256 R263 R284 R288 RES 1 1OOMW THICK FILM R 418 1K R298 R340 R259 R320 RES 10 10 1OOMW THICK FILM R 418 10 R262 RES 20K 1 100MW THICK FILM R 418 20K R264 R392 R396 RES 4 75K 1 100MW THICK FILM R 418 4 75K R265 RES 2 2M 10 1 2W 1 5KV METAL R 367 2 2M OXIDE R267 R269 RES 24 9K 1 100MW THICK FILM R 418 24 9K R273 R274 R307 R314 RES 475 1 1 4W METAL FILM R 391 475 R406 R416 R426 R428 R277 RES 66 5K 1 100MW THICK FILM R 418 66 5K R278 R281 RES 357 1 1OOMW THICK FILM R 418 357 R280 RES 49 9 1 100MW THICK FILM R 418 49 9 R285 RES 80 6K 1 100MW THICK FILM R 418 80 6K R286 RES 2K 1 1OOMW THICK FILM R 418 2K R287 R316 R317 R349 RES 1 28M 1 1 8W METAL FILM R 176 1 28M R289 R296 R299 R342 R337 R383 RES 1 100MW THICK FILM R 418 1K R390 R394 R290 R325 R330 R346 RES 49 9K
78. A E 2 Addthefollowingto ppm of range uncertainty 100mV 15ppm 1V and 100V 2ppm 10 and Dry Circuit Q 40ppm 10 1M 2ppm 20mA and 1 10ppm 100mA 40ppm 3 3296 measured with 10M O input resistance DMM gt 10GQ DMM on 10MQ and 100M2 ranges For Dry Circuit Q 32596 with Input HI connected to Sense with Sense HI disconnected add 30mvV 4 Relativeto calibration accuracy 5 For signal levels gt 500V add 0 02ppm V uncertainty for portion exceeding 500V 6 Specifications arefor 4 wire O 10 100 and 1000 with offset compensation on With offset compensation on OPEN CKT VOLTAGE is 12 8V For 2 wire add 1 50 to ppm of range uncertainty 10 range is 4 wire only 7 Must have 10 matching of lead resistance in Input HI and LO 8 Addthefollowingto ppm of reading uncertainty when using plug in modules JOKO 100ko 1MQ 10MQ 100 MQ All Modules 220ppm 2200 7701 7703 7707 7709 Modules 10 ppm 100ppm 1000 1 10 7706 7708 Modules 5 ppm 50 ppm 500ppm 5000ppm 5 9 Add 1 5V when used with plug in modules 10 For RATIO DCV only For AVERAGE DCV and Thermocouples only Available with plug in modules only 11 Add 6pV to of range uncertainty when using Models 7701 7703 and 7707 and 3uV for Models 7706 and 7709 12 Auto zero off 13 For LSYNC On line frequency 30 1 For LSYNC Off use 60dB for gt 1PLC 14 For 1kQ unbalance LO lead AC CMRR is 70dB 15 Speeds are for 60Hz
79. A TF 243 5K R398 RES 1 100MW THICK FILM R 418 1K R417 R419 R283 R358 RES 10K 1 100MW THICK FILM R 418 10K R430 R432 R434 R436 R438 R440 RES 475 1 1 4W METAL FILM R 391 475 R442 R439 R441 RES 100 1 1 4W METAL FILM R 391 100 RV101 RV102 VAR 576V METAL OXIDE 510L40 VR 5 RV103 TRANSIENT VOLTAGE SUPPRESSOR VR 25 RV104 RV 105 BIDIRECTIONAL TRANSIENT VOLT VR 8 SUPPRESSOR S101 SWITCH PUSHBUTTON 8 POLE SW 468 5 101 SURGE ARRESTOR CG3 1 5AL SA 4 SA102 SA103 SURGE ARRESTOR SA 8 50156 50157 SOCKET PLCC 032 T A 5 143 32 ST100 STANDOFF ST 204 2 TP102 TP105 CONN TEST POINT CS 553 TP103 TP104 TP106 TP107 SURFACE MOUNT PCB TEST POINT CS 1026 U101 IC VOLTAGE REG LM317M IC 846 U102 U118 IC J FET OP AMP TLE2081CD IC 967 U103 U105 U111 U129 IC CMOS ANALOG SWITCH DG211DY IC 768 U104 U200 U201 U205 IC MOSFET DRIVER TLP591B IC 877 U106 U109 U121 U130 U134 IC 8 STAGE SHIFT STORE MC14094BD IC 772 U203 U207 U107 U108 U126 U199 IC PHOTO DARLINGTON TRANS IC 911 PS2506L 1 U110 IC TRMS TO DC CONVERTER 637JR IC 796 U112 IC J FET OP AMP LF357M IC 966 U113 IC OP AMP LTC1050CS8 IC 791 U114 U167 IC DUAL J FET OP AMP OP 282GS IC 968 U115 U198 IC QUAD COMPARATOR LM339D IC 774 U116 U202 IC DARLINGTON ARRAY ULN2003L IC 969 U117 U145 IC VOLT COMPARATOR LM311M IC 776 U119 IC 15V VOLTAGE REGULATOR IC 1334 U120 U131 U169 U186 IC VOLT COMPARATOR LM393D IC 775 U122 U180 IC QUAD 2 INPUT OR 74HCT32 IC 808 U123 IC
80. AC at 1kHz 100mV AC at 50kHz 1V AC at IKHz 1V AC at 50kHz 10V AC at IKHz 10V AC at 50kHz 100V AC at 1kHz 100V AC at 50kHz 700V AC at 1kHz 10 00000mV 1kHz 100 0000mV 1kHz 100 0000mV 50kHz 1 000000V 1kHz 1 000000V 50kHz 10 00000V 1kHz 10 00000V 50kHz 100 0000V 1kHz 100 0000V 50kHz 700 000V 1kHz Model 2750 Multimeter Switch System Service Manual Calibration 2 13 AC current calibration After the 700VAC at 1kHz point has been calibrated the unit will prompt you for 100mA at 1kHz Follow these steps for AC current calibration 1 Connect the calibrator to the AMPS and INPUT LO terminals of the Model 2750 as shown in Figure 2 3 2 Perform the calibration steps summarized in Table 2 7 For each step Set the calibrator to the indicated current and frequency and make sure the unit is in OPERATE Press ENTER to complete each calibration step Allow the unit to complete each step before continuing z Table 2 7 E AC current calibration summary N 2 Calibration Step Calibrator Current Frequency A 100mA at 1kHz 100 0000mA 1kHz at 1kHz 1 000000A 1kHz 2A at 1kHz 2 000000A 1kHz L E Setting calibration dates and saving calibration At the end of the calibration procedure the instrument will display the CALIBRATION COMPLETE message Press ENTER to continue and the Model 2750 will prompt you to enter the calibration date and the calibration due date Set the
81. C C 0 03 C C 0 03 C C 0 03 C C 0 03 C C 0 03 C C 0 03 C C 100Q platinum PT100 D100 F100 PT385 PT3916 or user type Offset compensation On 200 to 630 C 0 01 C Thermistor 2 2kO 5kQ and 10 20 80 to 150 C 0 01 C 0 06 C 0 08 C 0 003 C C 0 002 C C Specifications A 3 DC SYSTEM SPEEDS 8 RANGE CHANGES 6 50 5 42 s FUNCTION CHANGES 50 5 42 5 AUTORANGE lt 30ms ASCII READINGS TO RS 232 19 2k BAUD 55 s MAX INTERNAL TRIGGER RATE 2000 s MAX EXTERNAL TRIGGER RATE 375 s DC MEASUREMENT SPEEDS Single Channel 60Hz 50Hz Operation FUNCTION DIGITS READINGS s PLCs DCV DCI Q 10M 6 51216 5 4 10 Thermocouple 6 516 35 28 1 Thermistor 6 51216 45 36 1 5 51216 150 120 0 1 5 5161 300 240 0 1 bb 500 400 0 1 451 2500 2000 0 01 AKO lt 10 6 516 14 11 10 6 516 15 12 1 5 517 33 25 0 1 RTD 22 6 516 09 07 10 6 516 8 64 1 5 516 17 18 14 4 0 1 Channel Ratio 6 516 25 2 10 Channel AVG 6 516 15 12 1 5 517 25 20 0 1 Multiple Channels Into and Out of Memory to GPIB 15 18 Channels s 7703 Scanning DCV 200 s 7703 Scanning DCV with Limits or Time Stamp On 180 5 7703 Scanning DCV alternating 2W 58 s 7702 Scanning DCV 65 s 7700 and 7708 Scanning Temperature T C 50 s DC SPEED vs NOISE REJECTION RMS Noise Rate Filter Readings Digits 10VRange NMRR CMRR
82. KEI I HLEY Model 2750 Multimeter Switch System Service Manual GRENE MEASUR EMSILES ONFIDENCE WARRANTY Keithley Instruments Inc warrants this product to be free from defects in material and workmanship for a period of 3 years from date of shipment Keithley Instruments Inc warrants the following items for 90 days from the date of shipment probes cables rechargeable batteries diskettes and documentation During the warranty period we will at our option either repair or replace any product that proves to be defec tive To exercise this warranty write or call your local Keithley representative or contact Keithley headquarters in Cleveland Ohio You will be given prompt assistance and return instructions Send the product transportation prepaid to the indicated service facility Repairs will be made and the product returned transportation prepaid Repaired or replaced products are warranted for the balance of the original warranty period or at least 90 days LIMITATION OF WARRANTY This warranty does not apply to defects resulting from product modification without Keithley s express written consent or misuse of any product or part This warranty also does not apply to fuses software non recharge able batteries damage from battery leakage or problems arising from normal wear or failure to follow instruc tions THIS WARRANTY IS IN LIEU OF ALL OTHER WARRANTIES EXPRESSED OR IMPLIED INCLUDING ANY IMPLIED WARRANT
83. METHOD Reciprocal Counting technique GATE TIME SLOW 1s MED 100ms and FAST 10ms AC General 70dB MAXIMUM CREST FACTOR 5 at full scale VOLT HERTZ PRODUCT lt 8 x 10 AC MEASUREMENT SPEEDS Single Channel 60Hz 50Hz Operation Function Digits Readings s Rate Bandwidth ACV ACI 6 58 2s Reading SLOW 3 Hz 300 kHz 6 58 1 4 1 1 MED 30 Hz 300 kHz 65 4 8 4 MED 30 Hz 300 kHz 6 5 40 32 FAST 300 Hz 300 kHz Frequency 6 5 1 1 SLOW 3Hz 300 kHz Period 5 5 9 9 MED 30Hz 300 kHz 45 35 35 FAST 300 Hz 300 kHz 41519 65 65 FAST 300 Hz 300 kHz Multiple Channel 7703 SCANNING ACV 180 s AC SYSTEM SPEEDS 1 RANGE CHANGES 4 5 3 5 FUNCTION CHANGES 4 5 3 5 AUTORANGE TIME lt 3s ASCII READINGS TO RS 232 19 2k baud 50 s MAX INTERNAL TRIGGER RATE 300 5 MAX EXTERNAL TRIGGER RATE 250 5 AC Notes 1 20 overrange except on 750V and 2 Specification are for SLOW mode and sine wave inputs 2596 of range SLOW and MED are multi sample A D conversions FAST is DETector BANDwidth 300 with nPLC 1 0 3 Applies to 0 18 C and 28 50 C 4 For square wave inputs gt 10 of ACV range except 100mV range 100mV range frequency must be gt 10Hz if input is 20mV 5 Applies to non sine waves gt 5Hz 6 For 1kQ unbalance in LO lead Specifications A 7 7 Speeds for 60Hz 50Hz operation using factory defaults operating conditions RST Autorange off Displa
84. Model 2750 Multimeter Switch System Service Manual Table B 5 continued Calibration errors Error Number Error Message 488 100 4 w dckt Ioff full scale error 489 100 4 w dckt Ion full scale error 490 10 4 w dckt Ioff zero error 491 10 4 w dckt Ion zero error 492 10 4 w dckt full scale error 493 10 4 w full scale error 494 10 4 w ocomp Ion zero error 495 10 4 w ocomp Ion full scale error 496 1 4 w dckt Ioff zero error 497 1 4 w dckt Ion zero error 498 1 4 w dckt Ion full scale error 500 Calibration data invalid 513 AC calibration data lost 514 DC calibration data lost 515 Calibration dates lost 518 Card calibration data lost 519 Card calibration dates lost 610 Questionable calibration Model 7700 card only Error queue As with other Model 2750 errors any calibration error will be reported in the bus error queue You can read this queue by using the SYST ERR query The Model 2750 will respond with the appropriate error number and message as summarized in Table B 5 Model 2750 Multimeter Switch System Service Manual Calibration Reference 25 Status byte EAV Error Available bit Whenever an error is available in the error queue the EAV Error Available bit bit 2 of the status byte will be set Use the STB query or serial
85. Model 7700 frequency verification CH1 Function Generator INPUT v2 WIRE 36 Ld lt j b OO Function Model 7700 Output Model 2750 Multimeter Switch System Service Manual Performance Verification 1 35 Verifying ratio and average Follow the procedure below to verify ratio and average CAUTION Exceeding 300V between the 7700 plug in module INPUT or SENSE H and L terminals may cause instrument damage 1 Connect the Model 7700 and CH11 H and L terminals to the DC calibrator as shown in Figure 1 18 2 Install the Model 7700 in Slot 1 of the Model 2750 then turn on the power and allow the unit to warm up for two hours before proceeding Be sure the front panel INPUTS switch is set to the REAR position 3 Select the Model 2750 DCV function and the 1V range Close Channel 1 by press ing the CLOSE key then ENTER for SINGLE channel and keying in 101 J e e I t EO 2 5
86. Multimeter Switch System Service Manual Troubleshooting 4 17 Table 4 7 Q2 signal switching Range Q101 Q102 0151 0150 0122 Q135 Q114 Q136 100 ON ON OFF OFF OFF OFF OFF OFF 1000 ON ON OFF OFF OFF OFF OFF OFF 1kQ ON ON OFF OFF OFF OFF OFF OFF 10kQ ON ON OFF OFF OFF OFF OFF OFF 100kQ ON ON OFF OFF OFF OFF OFF OFF IMQ ON ON OFF OFF OFF OFF OFF OFF 10MQ ON ON OFF OFF OFF OFF OFF OFF 100 0 ON ON OFF OFF OFF OFF OFF OFF Range Q109 K101 K102 Q113 Q104 Q108 Q106 Q148 100 OFF SET RESET OFF ON OFF OFF ON 1000 OFF SET RESET OFF ON OFF OFF ON 1kQ OFF SET RESET OFF ON OFF OFF ON 10kQ OFF SET RESET OFF ON OFF OFF ON 100kQ OFF SET RESET OFF ON OFF OFF ON IMQ OFF SET RESET OFF ON OFF OFF ON 10MQ ON SET RESET OFF ON OFF OFF ON 100 0 ON SET RESET OFF ON OFF OFF ON K101 set states Pin 8 switched to Pin 7 Pin 3 switched to Pin 4 K102 reset states Pin 8 switched to Pin 9 Pin 3 switched to Pin 2 E oO E ge 4 18 Troubleshooting Model 2750 Multimeter Switch System Service Manual Table 4 8 94 signal switching Range Q101 Q102 0151 0150 0122 Q135 Q114 Q136 10 OFF OFF ON ON ON ON OFF OFF 100 OFF OFF ON ON ON ON OFF OFF 1000 OFF OFF ON ON ON ON OFF OFF 1kQ OFF OFF ON ON ON ON OFF OFF 10kQ OFF OFF ON ON ON ON OFF OFF 100kQ OFF OFF ON ON ON ON OFF
87. NS PNP MMBT3906L TG 244 Q121 Q134 0119 TRANS P CHANNEL JFET 1270 TG 166 1 Q122 0135 0150 Q151 TRANS N CHAN MOSFET TN2540N8 TG 274 Q125 Q158 Q103 Q157 TRANS N CHANNEL FET 2N4392 TG 128 1 Q127 Q128 Q131 Q132 Q133 TRANS N MOSFET VN0605T TG 243 Q130 NPN SILICON TRANSISTOR TG 309 Q156 TRANS PNP SILICON 2N3906 TG 84 Q162 Q120 TRANS PNP BC860C TG 323 R101 R102 RES 1M 5 125MW METAL FILM R 375 1M e eg 2 m n 6 6 Replaceable Parts Table 6 1 continued Model 2750 motherboard parts list Model 2750 Multimeter Switch System Service Manual Circuit Designation Description Keithley Part No R104 R105 RES 549K 1 1 4W METAL FILM R 315 549K R106 RES 11K 1 1 10W METAL FILM R 263 11K R107 RES 49 9 1 1 4W METAL FILM R 391 49 9 R108 R207 R336 RES 24 9K 1 100MW THICK FILM R 418 24 9K R109 R134 R167 R194 R195 RES 1 1 4W METAL FILM R 391 1K R110 R133 R405 THICK FILM TF 280 1 R111 R140 R165 R190 R197 R200 RES 1 100MW THICK FILM R 418 1K R203 R279 R112 R116 R221 RES 15k 1 1OOMW THICK FILM R 418 15K R113 R188 RES 49 9 1 1 4W METAL FILM R 391 49 9 R114 R122 R199 RES 604 1 1OOMW THICK FILM R 418 604 R115 R175 R176 R324 R132 R139 RES 2 49K 1 1 4W METAL FILM R 391 2 49K R117 RES NET VARIOUS 1 MDN460 TF 255 R118 R103 R160 R174 R361 R362 RES 499 1 1 4W METAL FILM R 391 499 R365 R366 R119 R384 R385 RES
88. OFF IMQ OFF OFF ON ON ON ON OFF OFF 10MQ ON ON OFF OFF ON ON OFF OFF 100MQ ON ON OFF OFF ON ON OFF OFF Range Q109 K101 K102 Q113 Q104 Q108 Q106 Q148 10 OFF SET ON OFF OFF OFF ON 100 OFF SET RESET ON OFF OFF OFF 1000 OFF SET RESET ON OFF OFF OFF 1kQ OFF SET RESET ON OFF OFF OFF 10kQ OFF SET RESET ON OFF OFF OFF 100kQ OFF SET RESET ON OFF OFF OFF IMQ OFF SET RESET ON OFF OFF OFF 10MQ ON SET RESET OFF ON OFF OFF 100MQ2 ON SET RESET OFF ON OFF OFF KlOlsetstates Pin 8 switched to Pin 7 Pin 3 switched to Pin 4 K102 reset states Pin 8 switched to Pin 9 Pin 3 switched to Pin 2 z Z Z Z z Z Z 2 04 only Model 2750 Multimeter Switch System Service Manual Troubleshooting 4 19 Table 4 9 94 dry circuit signal switching Range 0101 Q102 Q151 0150 0122 0135 0114 0136 10 ON ON ON ON ON ON OFF OFF 10Q ON ON ON ON ON ON OFF OFF 1000 OFF OFF IK ON ON ON ON ON ON OFF OFF Range Q109 K101 K102 Q113 Q104 Q108 Q106 QI148 10 OFF SET RESET ON OFF OFF ON OFF 10Q OFF SET RESET ON OFF OFF ON OFF 1000 OFF SET RESET ON OFF OFF ON OFF IK OFF SET RESET ON OFF OFF ON OFF K101 set states Pin 8 switched to Pin 7 Pin 3 switched to Pin 4 K102 reset states Pin 8 switched to Pin 9 Pi
89. PINS CS 736 4 J3 CONN RT ANGLE HEADER CS 1066 1 J4 CONN RT ANGLE HEADER 26 PIN CS 1066 2 J4 J5 CONN FEMALE 8 PIN CS 612 8 J5 CONN FEMALE 8 PIN CS 612 8 J6 CONN MALE 3 PIN CS 612 1 J6 J7 CONN MALE 3 PIN CS 612 1 L1 L2 FERRITE CHIP 600 OHM BLM32A07 CH 62 2 11 13 FERRITE CHIP 600 BLM32A07 CH 62 R1 R3 RES 4 75K 1 1000MW THICK FILM R 418 4 75K 2 R1 R4 RES 4 75K 1 1000MW THICK FILM R 418 4 75K R2 R3 R5 R19 RES 475 1 1 AW METAL FILM R 391 475 R2 R4 R13 RES 475 1 1 4W METAL FILM R 391 475 S n 6 14 Replaceable Parts Model 2750 Multimeter Switch System Service Manual Table 6 4 Model 2750 miscellaneous parts list Qty Description Keithley Part No 1 3 SLOT CARD CAGE 2750 316B 1 5X20MM SNAP IN FUSE HOLDER FH 40 2 BANANA JACK PUSH IN BLACK BJ 14 0 2 BANANA JACK PUSH IN RED BJ 14 2 1 BANANA JACK PUSH IN WHITE BJ 14 9 1 CARD CAGE 2700 3 18A 1 CARD CAGE SUPPORT 2750 313A 1 COND RUBBER SWITCH 2750 3 10A 37 CONNECTOR CS 236 4 CONNECTOR CS 638 8 1 CONNECTOR HARDWARE KIT CS 713 4 CONNECTOR HOUSING CS 638 3 1 CONNECTOR MODULES CS 638 12 1 COVER 2750 309A 1 DISPLAY LENS 2750 307A 4 FOOT MOLDED 24322 4 FOOT RUBBER FE 6 1 FRONT PANEL 2750 305A 1 FRONT REAR ROD 2700 3 19A 1 FUSE HOLDER FH 35 1 1 FUSE 630A 250V SLO BLO FUSE FU 106 630 1 FUSE 3A 250 FU 99 1 2 HANDLE HH 30 7 1 LINE CORD CO 7 1 LINE MODULE PM 1 1B 1 MOTHER BD SUPPORT BRACKET 2750
90. TE command allows you to store the calibration date in instru ment memory for future reference You can read back the date from the instrument over the bus by using the DATE query or the CALIBRA TION selection in the front panel CAL menu NOTE The year month and day parameters must be delimited by commas Example CAL PROT DATE 2001 3 16 Send cal date 3 16 2001 CAL PROT DATE Request cal date NDUE CALibration PROTected NDUE Purpose To send the next calibration due date to the instrument Format cal prot ndue year month day Parameters year 2000 to 2099 month to 12 day to 31 Query cal prot ndue Response lt year gt lt month gt lt day gt Description The NDUE command allows you to store the date when calibration is next due in instrument memory You can read back the next due date from the instrument over the bus by using the NDUE query or the front panel CAL menu NOTE next due date parameters must be delimited by commas E 5 e c c Example CAL PROT NDUE 2002 3 16 Send due date 3 16 2001 CAL PROT NDUE Request due date B 8 Calibration Reference Model 2750 Multimeter Switch System Service Manual DC calibration commands The DC commands perform calibration of the DCV DCI and ohms functions Table B 2 summarizes these calibration commands along with parameter limits Table B 2 DC
91. THICK FILM R 418 499 R158 RES 1 1 2W 4 TERMINAL MOLDED 342 1 R159 R360 R168 R182 R239 R247 RES 1K 1 1 4W METAL FILM R 391 1K R266 R272 R162 R166 RES 560K 5 250MW METAL FILM R 376 560K R170 RES 2 21 1 100MW THICK FILM R 418 2 21 R171 RES 100K 1 125W THIN FILM R 456 100K R172 R339 R343 RES 1 100MW THICK FILM R 418 1M R173 RES 1K 1 125W THIN FILM R 456 1K R177 RES 100K 1 1 4W METAL FILM R 391 100K R181 R202 R204 R206 R208 R210 RES 10K 1 100MW THICK FILM R 418 10K R220 R223 R187 R425 R427 R429 R431 R433 RES 100 1 1 4W METAL FILM R 391 100 R435 R437 R189 RES 3 01K 1 1 4W METAL FILM R 391 3 01K R192 RES 6 98K 1 1 4W METAL FILM R 391 6 98K R198 RES 70K 1 3W 300V METAL FOIL R 449 70K R205 R338 RES 10 5 UEN METAL FILM R 246 10 R209 RES 332K 1 100MW THICK FILM R 418 332K R212 R217 RES 2 21K 1 1000MW THICK FILM R 418 2 21K R215 RES 4 42K 1 1 4W METAL FILM R 391 4 42K R216 RES 2 87K 1 1 4W METAL FILM R 391 2 87K R219 RES 2K 1 100MW THICK FILM R 418 2K R222 RES 56 2K 1 1000MW THICK FILM R 418 56 2K R224 R231 R348 R389 R420 R422 RES 10K 1 100MW THICK FILM R 418 10K R423 R424 R225 RES 470 5 125MW METAL FILM R 375 470 R226 RES 475 1 100MW THICK FILM R 418 475 R228 R235 R237 R245 R250 R252 RES 475 1 100MW THICK FILM R 418 475 R255 R233 R238 R254 R276 R282 RES 10K 1 100MW THICK FILM R 418 10K R291 R293 R31
92. TION Operating the Model 2750 on the wrong line voltage may result in instrument damage E 5 2E 5 b 3 Ifconfiguring the instrument for a different line voltage remove the line voltage selector from the assembly and rotate it to the proper position When the selector is installed into the fuse holder assembly the correct line voltage appears inverted in the window 4 Install the fuse holder assembly into the power module by pushing it in until it locks in place Table 3 1 Power line fuse Line Voltage Rating Keithley Part No 100 120V 0 630A 250V 5 x 20 mm slow blow FU 106 630 200 240V 0 315A 250V 5 x 20 mm slow blow FU 106 315 3 4 Routine Maintenance Model 2750 Multimeter Switch System Service Manual Replacing the AMPS fuse The front panel AMPS fuse protects the Model 2750 AMPS current input from an over current condition Follow the steps below to replace the AMPS fuse WARNING Make sure the instrument is disconnected from the power line and other equipment before replacing the AMPS fuse 1 Turn off the power and disconnect the power line and test leads 2 Using a screwdriver rotate the fuse carrier one quarter turn counterclockwise Figure 3 2 Release pressure on the jack and its internal spring will push the fuse carrier out of the socket CAUTION Do not use a fuse with a higher current rating than specified or instru ment damage may occur If the ins
93. UN Request calibration count Model 2750 Multimeter Switch System Service Manual Calibration Reference B 5 INIT CALibration PROTected INITiate Purpose To initiate comprehensive and factory calibration procedures Format cal prot init Parameters None Description The INIT command enables Model 2750 calibration when perform ing these procedures over the bus This command must be sent to the unit after sending the CODE command but before sending any other calibration command NOTE The INIT command should be sent only once before performing either DC AC or factory calibration Do not send INIT before each calibration step Example CAL PROT INIT Initiate calibration CALibration PROTected LOCK Purpose To lock out comprehensive or manufacturing calibration Format cal prot lock Parameters None Description The LOCK command allows you to lock out both comprehensive and manufacturing calibration after completing those procedures Thus LOCK performs the opposite of enabling calibration with the CODE command NOTE unlock comprehensive calibration send the CODE command To unlock manufacturing calibration hold in the OPEN key while turning on the power Example CAL PROT LOCK Lock out calibration O E 5 e c c 5 B 6 Calibration Reference Model 2750 Multimeter Switch System Service Manual LOCK CALibration PROTected LOCK Purpose To re
94. VER HEAT STAKE ASSEMBLY 7700 302A BOTTOM CARD COVER 7702 301C COMPRESSION SPRING SP 7 3 Specifications A 2 Specifications MODEL 2750 SPECIFICATI ONS DC CHARACTERISTICS CONDITIONS MED 1 PLC or 10 PLC or MED 1 PLC with Digital Filter of 10 ACCURACY 3 ppm of reading ppm of range TEST INPUT ppm parts per million CURRENT 5 RESISTANCE e g 10ppm 0 001 TEMPERATURE ORBURDEN OROPENCKT 24Hour 90Day 1Year COEFFICIENT FUNCTION RANGE RESOLUTION VOLTAGE VOLTAGE 23 C 1 23 5 23 C 5 0 18 C amp 28 50 C Voltage 100 0000 mV 01 UN gt 10 GQ 15 30 25435 30 35 1 5 1 000000 V 10 gt 10 GQ 15 6 2547 3047 1 1 C 1000000 V 10 pv gt 10 GQ 10 4 2045 3045 1 1 C 100 0000 V 100 pV 10 1 15 6 35 9 45 9 5 1 C 1000000 V5 1 mv 10 MQ 1 20 6 3549 50 9 5 1 C Resistance 1 000000 Q 1 uQ 10 mA 5 9 V 80 40 80 40 100 40 8 1 C 1000000 Q 10 10 mA 59 V 20 20 80 20 100420 8 1 C 100 0000 Q 100 1mA 122 V 20 20 80 20 100 20 8 1 C 1 000000 1 1 122 V 20 6 80 6 100 6 8 1 C 10 00000 kQ 10 mQ 100 pA 68 V 20 6 80 6 100 6 8 1 C 100 0000 kQ 100 10 pA 128 V 20 6 80 10 100410 8 1 C 1 000000 23 10 10 pA 128 V 20 6 80 10 100 10 8 1 C 10 00000 MQ 73 10 Q 0 7 UAI INO 7 0 V 150 6 200 10 400 10 70 1 C 100 0000 MQ 73 100 Q 07 pA 10M Q 70V 800 30 2000 30 2000 30 385 1 C DryCircuit 1 000000 Q
95. Y OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR USE THE REMEDIES PROVIDED HEREIN ARE BUYER S SOLE AND EXCLUSIVE REMEDIES NEITHER KEITHLEY INSTRUMENTS INC NOR ANY OF ITS EMPLOYEES SHALL BE LIABLE FOR ANY DIRECT INDIRECT SPECIAL INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OF ITS INSTRUMENTS AND SOFTWARE EVEN IF KEITHLEY INSTRUMENTS INC HAS BEEN ADVISED IN ADVANCE OF THE POSSIBILITY OF SUCH DAMAGES SUCH EXCLUDED DAM AGES SHALL INCLUDE BUT ARE NOT LIMITED TO COSTS OF REMOVAL AND INSTALLATION LOSSES SUSTAINED AS THE RESULT OF INJURY TO ANY PERSON OR DAMAGE TO PROPERTY KEITHLEY Keithley Instruments Inc 28775 Aurora Road Cleveland OH 44139 440 248 0400 Fax 440 248 6168 http www keithley com BELGIUM Keithley Instruments B V Bergensesteenweg 709 B 1600 Sint Pieters Leeuw 02 363 00 40 Fax 02 363 00 64 CHINA Keithley Instruments China Yuan Chen Xin Building Room 705 12 Yumin Road Dewai Madian Beijing 100029 8610 62022886 Fax 8610 62022892 FRANCE Keithley Instruments Sarl 3 all e des Garays 91127 Palaiseau Cedex 01 64 53 20 20 Fax 01 60 11 77 26 GERMANY Keithley Instruments GmbH Landsberger Strasse 65 82110 Germering 089 84 93 07 40 Fax 089 84 93 07 34 GREAT BRITAIN Keithley Instruments Ltd The Minster 58 Portman Road Reading Berkshire RG30 1EA 0118 9 57 56 66 Fax 0118 9 59 64 69 INDIA Keithley Instruments GmbH Flat 2B WILOCRISSA 14 Rest Hous
96. ad comprehensive calibration lock status Format cal prot lock Response 0 Comprehensive calibration locked 1 Comprehensive calibration unlocked Description The LOCK query requests status from the Model 2750 on calibration locked unlocked state Calibration must be enabled sending the CODE command before calibration can be performed Example CAL PROT LOCK Request cal lock state SAVE CALibration PROTected SAVE Purpose To save calibration constants in EEROM after the calibration procedure Format cal prot save Parameters None Description The SAVE command stores internally calculated calibration constants derived during both comprehensive and manufacturing calibration in EEROM EEROM is non volatile memory Calibration constants will be retained indefinitely once saved Generally SAVE is sent after all other calibration steps except for LOCK NOTE Calibration will be only temporary unless the SAVE command is sent to per manently store calibration constants Example CAL PROT SAVE Save calibration constants Model 2750 Multimeter Switch System Service Manual Calibration Reference B 7 DATE CALibration PROTected DATE Purpose To send the calibration date to the instrument Format Ccal prot date year month day Parameters year 2000 to 2099 month 1 to 12 day to 31 Query cal prot date Response lt year gt lt month gt lt day gt Description The DA
97. al circuitry checks 4 14 Digital I O 4 8 Disassembly 5 1 Disassembly procedures 5 4 DISP test 4 3 Display 4 7 Display board 4 6 Display board checks 4 13 Environmental conditions 1 3 2 2 Error queue B 24 Error summary B 21 Extender board connections 2 24 factory defaults restoring 1 6 Factory service 6 2 frequency Verifying Model 2700 1 20 verifying Model 7700 1 34 Front panel disassembly 5 5 tests 4 3 Front panel Model 7700 calibration 2 24 Front terminal AMPS fuse 3 4 fuse front terminal replacing 3 4 Power line 3 3 fuses plug in module replacing 3 5 Generating an SRQ on calibration complete B 26 Generating an SRQ on error B 25 Handling and cleaning 5 2 Handling PC boards 5 2 IEEE 488 interface 4 8 INPUT HI 4 10 Input terminal wire colors 5 6 Instrument reassembly 5 6 K Introduction Calibration 2 2 Calibration Program C 2 Calibration Reference B 2 Disassembly 5 2 Performance Verification 1 2 Replaceable Parts 6 2 Routine Maintenance 3 2 troubleshooting 4 2 Key matrix 4 7 KEY test 4 3 limits ACI Model 2700 1 13 DCI Model 2700 1 12 Plug in module ACI Model 7700 1 26 Plug in module DCI Model 7700 1 25 plug in module resistance verification Model 7700 1 28 resistance verification Model 2700 1 16 1 18 1 30 line fuse replacing 3 2 Line power 1 3 2 2 Line sync 4 8 line voltage setting 3 2 Maintenance Routine 3 1 Manufacturing calibration 2 20 Extender board preparation 2
98. an additional derating factor of 0 02ppm V must be added to DCV specifications for voltages over 500V Before calculating accuracy study the associated specifications very carefully to see if any derating factors apply O ptimizing measurement accuracy The configurations listed below assume that the multimeter has had factory setups restored DC voltage DC current and resistance Select 6 1 2 digits 10 PLC filter ON up to 100 readings fixed range Use REL on DC voltage and 2 wire resistance measurements Use 4 wire resistance measurements with offset compensation for best accuracy AC voltage and AC current Select 6 1 2 digits 10 PLC filter ON up to 100 readings fixed range Temperature Select 6 1 2 digits 10 PLC filter ON up to 100 readings A 12 Specifications Model 2750 Multimeter Switch System Service M anual O ptimizing measurement speed The configurations listed below assume that the multimeter has had factory setups restored DC voltage DC current and resistance Select 3 1 2 digits 0 01 PLC filter OFF fixed range AC voltage and AC current Select 3 1 2 digits 0 01 PLC filter OFF fixed range Temperature Select 3 1 2 digits 0 01 PLC filter OFF For all functions turn off the display and autozero and set the trigger delay to zero Use the SAMPle COUNt and READ bus commands Calibration Reference B 2 Calibration Reference Introduction M
99. anner card Slot 1 and select the rear inputs with the INPUTS switch Allow three minutes for thermal equilibrium 2 Press in and hold the OPEN key while turning on the power 3 Press SHIFT then TEST then display CALIB TEST with the up or down range key Press ENTER select RUN then enter the appropriate calibration code default 002750 4 Select ALL at the CAL RUN prompt 5 Press ENTER to perform the first manufacturing calibration step 6 Perform the entire front panel comprehensive calibration procedure discussed ear lier in this section See Comprehensive calibration earlier in this section 7 Connect the function generator to the Model 2750 front panel INPUT jacks as shown in Figure 2 5 Select the front input jacks with the INPUTS switch gt e N N zu gt 2 22 Calibration Model 2750 Multimeter Switch System Service Manual Figure 2 5 Function generator connections for manufacturing calibration Function Generator BNC to Dual Model 2750 Banana Plug Front Panel Adapter ei eslei Function Output Note Output voltage must be accurately measured See text 8 After the last AC current calibration step the instrument will prompt you to enter 3Hz at RMS 1kHz with the following prompts Low frequency cal Set the function
100. as been changed modify the CAL PROT CODE parameter accordingly 7 Runthe program and follow the prompts on the screen to perform calibration Figure C 1 Model 2750 calibration program Model 2750 calibration program Rev 1 0 3 1 2001 OPEN IEEE FOR OUTPUT AS 1 Open IEEE 488 output path OPEN IEEE FOR INPUT AS 2 Open IEEE 488 input path PRINT 1 INTERM CRLF Set input terminator PRINT 1 OUTTERM LF Set output terminator PRINT 1 REMOTE 4 16 Put 2750 5700A in remote PRINT 1 CLEAR Send DCL PRINT 1 OUTPUT 16 SYST PRES CLS Initialize 2750 PRINT 1 OUTPUT 16 ESE 1 SRE 32 Enable OPC and SRQ PRINT 1 OUTPUT 4 RST CLS STBY Reset 5700A calibrator PRINT 1 OUTPUT 4 CUR_POST NORMAL Normal current output C CAL PROT 2750 partial command header CLS Clear CRT PRINT Model 2750 Multimeter Comprehensive Calibration Program PRINT 1 OUTPUT 16 CAL PROT CODE KI002750 Send KI002750 cal code PRINT 1 OUTPUT 16 CAL PROT INIT Initiate calibration GOSUB ErrCheck RESTORE CmdList 1 FOR I 1 25 Loop for all cal points READ Msg Cmd Read message cal strings C 4 Calibration Program SELECT CASE I CASE 1 2 PRINT GOSUB Msg KeyCheck CASE 3 RINT RINT OSUB KeyCheck RINT 1 OUTP RINT 1 OUTP RINT 1 OUTP 5 12 14 TO 22 RINT OUTP RINT OUTP TO 9 RINT RINT RINT RINT RINT INPUT tg g t
101. assemble and reassemble the Model 2750 Refer to these drawings for information about the Keithley part numbers of most mechanical parts in the unit The drawings are located at the end of this section of the manual Front Panel Assembly 2750 040 Card Cage Power Module Assembly 2750 050 Power Module Transformer Chassis Assembly 2750 051 Front Panel Card Cage Chassis Assembly 2750 052 Chassis Assembly 2750 053 2750 054 Final Inspection 2750 080 Ajquiassesiq 5 4 Disassembly Model 2750 Multimeter Switch System Service Manual Disassembly procedures Case cover removal Follow the steps below to remove the case cover to gain access to internal parts WARNING Before removing the case cover disconnect the line cord and any test leads from the instrument Remove Screws Remove the four screws two on each side that secure the case to the chassis Remove Cover To remove the case grasp the case at the sides and carefully slide the cover back about an inch then lift the case cover off the chassis Motherboard removal Perform the following steps to remove the motherboard This procedure assumes that the case cover is already removed 1 2 Remove the IEEE 488 RS 232 and Digital I O fasteners The IEEE 488 RS 232 and Digital I O connectors each have two nuts that secure the connectors to the rear panel Remove these nuts Remove the front rear switch rod At the switch pla
102. ber Factory service If the instrument is to be returned to Keithley Instruments for repair perform the following Callthe Repair Department at 1 888 KEITHLEY for a Return Material Authoriza tion RMA number Complete the service form at the back of this manual and include it with the instrument Carefully pack the instrument in the original packing carton Write ATTENTION REPAIR DEPARTMENT and the RMA number on the ship ping label Model 2750 Multimeter Switch System Service Manual Replaceable Parts 6 3 Component layouts Component layouts for the various circuit boards are provided on the following pages Table 6 1 Model 2750 motherboard parts list Circuit Designation Description Keithley Part No BT100 L1 BATTERY 3 6V 950MAH BA 51 C100 C129 C130 C141 C158 C176 CAP 47P 5 100V CERAMIC C 465 47P C200 C219 C102 C101 CAP 01UF 1096 1000V CERAMIC C 64 01 C103 C107 C111 C128 C151 C166 CAP 1UF 20 50V CERAMIC C 418 1 C290 C295 C104 CAP 100UF 20 63V ALUM ELEC C 403 100 C105 CAP 22UF 20 400V FILM 513 22 C106 CAP 15P 1 100V CERAMIC C 512 15P C108 CAP 068U 10 100V CERAMIC C 389 068 C109 CAP 2 2UF 20 63V POLYCARB C 480 2 2 C110 C181 C226 C254 C277 C192 CAP 47P 596 100V CERAMIC C 465 47P C112 C248 CAP 01 596 50V NPO C 514 01 C113 C114 C119 C126 C247 CAP 1000P 10 100V CERAMIC C 451 1000P C115 CAP 33UF 20 63V POLYCARBONATE C 482 33 C116 C118 C122
103. ble 1 1 In general equipment uncertainty should be at least four times better than cor responding Model 2750 specifications Keep in mind however that calibrator uncertainty will add to the uncertainty of each measurement Table 1 1 Recommended verification equipment Fluke 5700A Calibrator AC Voltage AC Current DC Voltage 1kHz 50kHz DC Current 1kHZ Resistance 100mV 14ppm 100mV 200ppm 20mA 60ppm 1A 690ppm 1Q 95ppm 1 0V 7ppm 1 0V 82ppm 100mA 70ppm 2 2A 682ppm 100 17 10V 5ppm 10V 82ppm 1A 110ppm 100Q 17ppm 100V 7ppm 100V 90ppm 2 2 94 1kQ 12ppm 1000V 9ppm 700V 85ppm 10kQ 1 1 ppm 100kQ 13ppm 1MQ 18ppm 10MQ 37ppm 100MQ 120ppm Fluke 5725A Amplifier AC Voltage 50kHz 700V x375ppm DC Current 3A 500ppm AC Current 1kHz 3A 457ppm Stanford Research Systems DS345 Function Generator 1V RMS 1kHz 5ppm General Radio 1433 T Precision Decade Resistance Box 10Q to 400Q 0 02 Miscellaneous Equipment Double banana plug to double banana plug shielded cables 2 BNC to double banana plug shielded cable Note The Fluke 5725A amplifier is necessary only if you wish to verify the 750V AC range at 50kHz and 3A AC and DC current ranges at 3A Verification at 220V 50kHz and 2 2A on the current ranges using only the 5700A calibrator is adequate for most applications Calibrator 1Q uncertainty is not four times better than Model 2750 1Q range acc
104. ble 1 16 Model 7700 thermocouple temperature verification reading limits Thermocouple Type Applied DC Voltage Reading Limits 1 year 18 C to 28 C J 7 659mV 191 8 to 188 2 C 1 0 to 1 0 C 42 280mV 749 0 to 751 0 C K 5 730mV 191 8 to 188 2 C OmV 1 0 to 1 0 C 54 138mV 1349 0 to 1351 0 C Voltages shown are based on ITS 90 standard Model 2750 Multimeter Switch System Service Manual Performance Verification 1 33 RTD temperature 1 Connect the precision decade resistance box listed in Table 1 1 to the Model 7700 CH1 and CH11 H and L terminals using four wire connections See Figure 1 14 for similar connecting scheme 2 Install the Model 7700 in Slot 1 of the Model 2750 then turn on the power and allow the unit to warm up for two hours before proceeding Be sure the front panel INPUTS switch is set to the REAR position 3 Select the temperature function by pressing the TEMP key Close Channel 1 by pressing the CLOSE key and keying in 101 4 Configure the Model 2750 temperature function for C units and RTD temperature sensor 0 0 00385 as follows a Press SHIFT then SENSOR and note the unit displays the temperature units UNITS C Press ENTER and note the unit displays the sensor type SENS TCOUPLE Using the cursor and range keys set the display as follows SENS 4W RTD Press ENTER and note the unit displays TYPE PT100 Using the cursor and range keys set the un
105. bration equipment The following calibration equipment is required Fluke 5700A Calibrator Keithley Model 8610 Calibration Short Double banana plug to BNC cables See Section 2 for detailed equipment information and refer to these figures for connections Low thermal short connections Figure 2 1 DC volts and ohms connections Figure 2 2 DC amps and AC amps connections Figure 2 3 AC volts connections Figure 2 4 Model 2750 Multimeter Switch System Service Manual Calibration Program C 3 General program instructions 1 With the power off connect the Model 2750 and the calibrator to the IEEE 488 interface of the computer Be sure to use shielded IEEE 488 cables for bus connec tions 2 Turnon the computer Model 2750 and calibrator Allow the Model 2750 and the calibrator to warm up for at least one hour before performing calibration 3 Make sure the Model 2750 is set for a primary address of 16 Use the front panel GPIB key to check or change the address Make sure the calibrator primary address is at its factory default setting of 4 S S 5 a ga J S 3 5 Make sure that the computer bus driver software CECHP EXE is properly initial ized 6 Enter the QBasic editor and type in the program below Check thoroughly for errors then save it using a convenient filename NOTE The program assumes a default calibration code of KI002750 If the calibration code h
106. calibration commands STEP8 lt NRf gt STEPO lt NRf gt 100kQ 4 wire calibration step IMQ 4 wire calibration step Command Description Parameter Limits CALibration PROTected DC STEP 1 Front terminal short circuit STEP2 Open circuit STEP3 lt NRf gt 10V DC calibration step 9 to 11 5 4 lt NRf gt 10V DC calibration step 9 to 11 5 5 lt NRf gt 100V DC calibration step 90 to 110 STEP6 lt NRf gt 1000 4 wire calibration step 90 to 110 STEP7 lt NRf gt 10kQ 4 wire calibration step 9 to 11E3 90E3 to 110E3 900E3 to 1 1E6 STEPIO lt NRf gt 10mA DC calibration step 9E 3 to 11E 3 STEPI 1 lt NRf gt 100mA DC calibration step 90E 3 to 110E 3 STEPI2 lt NRf gt 1A DC calibration step 0 9 to 1 1 STEP1 CALibration PROTected DC STEP1 Purpose To perform front terminal short circuit calibration Format 1 1 Parameters None Description STEP1 performs the short circuit calibration step in the comprehen Example sive calibration procedure Connect a low thermal short Model 8610 to the front panel input jacks before sending this command CAL PROT DC STEP Perform short circuit calibration Model 2750 Multimeter Switch System Service Manual Calibration Reference B 9 STEP2 CALibration PROTected DC STEP2 Purpose Format Parameters Description Example STEP3 To perform front terminal open circuit calibration
107. ce the edge of a flat blade screwdriver in the notch on the push rod Gently twist the screwdriver while pulling the rod from the shaft Unplug cables Unplug the display board ribbon cable from connector J1014 Unplug the transformer cables from connectors J1002 and J1003 Unplug scanner slots ribbon cables from connectors J1012 and J1016 Unplug analog backplane connections J1008 and J1010 Unplug front panel input terminals connector from J1017 Remove the fastening screws five total that secure the motherboard to the chassis Most screws are around the periphery of the board one of these screws secures U144 while two are located away from the edges of the board During reassembly replace the board and start the IEEE 488 RS 232 and Digital I O connector nuts and the mounting screw Tighten all the fasteners once they are all in place and the board is correctly aligned Remove the motherboard by sliding it forward until the connectors clear the rear panel then carefully pull the motherboard from the chassis Model 2750 Multimeter Switch System Service Manual Disassembly 5 5 Card cage removal After the motherboard has been removed the 2 slot card cage underneath that holds plug in modules can be removed simply by removing the three screws two top one bottom that attach the card cage to the case bottom The 3 slot card cage can be removed in a sim ilar manner by removing the three screws two top one bottom t
108. cified for to 50 C eio For more information refer to the Specified to 8096 R H at 35 C ROUTe MULTiple command section STORAGE ENVIRONMENT 25 C to 65 C Card TZ in the Model 2700 or 2750 User s Manual WEIGHT 0 45kg 11b Channels 24 and 25 can be individually controlled using ROUTe MULTiple if the ed E module is not to be connected to the Specifications subject to change without notice internal DMM M odel 2750 Multimeter Switch System Service M anual Specifications Accuracy calculations A 9 The information below discusses how to calculate accuracy for both DC and AC characteristics Calculating D C characteristics accuracy Calculating AC characteristics accuracy DC characteristics accuracy is calculated as follows Accuracy ppm of reading ppm of range ppm parts per million and 10ppm 0 001 As an example of how to calculate the actual reading limits assume that you are measur ing 5V on the 10V range You can compute the reading limit range from one year DCV accuracy specifications as follows Accuracy 30ppm of reading 5ppm of range 30ppm x 5V 5ppm x 10V 150 50uV 200UV Thus the actual reading range is 5V 200 or from 4 9998V to 5 0002 DC current and resistance calculations are performed in exactly the same manner using the pertinent specifications ranges and input signal values AC characteristics accuracy is calculated similarly e
109. couple temperature verification rra 1 31 Connections for Model 7700 frequency verification 1 34 Connections for Model 7700 ratio and average verification sr 1 35 Calibration Low thermal short connections 2 7 Connections for DC volts and ohms calibration 2 8 Connections for DC and AC amps calibration 2 11 Connections for AC volts calibration 2 12 Function generator connections for manufacturing calibration 2 22 Routine Maintenance Power module n erento tat reiz 3 3 AMPS SUIS 3 4 Model 7700 amps fuses rr 3 5 Rack preparation rr 3 11 4 Figure 4 1 Figure 4 2 Figure 4 3 Figure 4 4 C Figure C 1 Troubleshooting Power supply block diagram rra 4 4 Digital circuitry block diagram rra 4 6 Analog circuitry block diagram sess 4 9 Simplified schematic of dry circuit ohms 4 12 Calibration Program Model 2750 calibration program rr C 3 List of Tables 1 Table 1 1 Table 1 2 Table 1 3 Table 1 4 Table 1 5 Table 1 6 Table 1 7 Table 1 8 Table 1 9 Table 1 10 Table 1 11 Table 1 12 Table 1 13 Table 1 14 Table 1 15 Table 1 16 Table 1 17 2 Table 2 1 Table 2 2 Table 2 3 Table 2 4 Table 2 5 Table 2 6 Table 2 7 Table 2 8 Table 2 9 Table 2 10 Table 2
110. d CAL PROT AC STEPIA Cal voltage Here Cal voltage is the actual 3Hz generator signal amplitude you measured previously 9 Set the generator to output a 1V RMS IKHz sine wave then send the following command z CAL PROT AC STEPI5 1E3 10 Send the following commands to set calibration dates save calibration and lock 2 calibration 3 CAL PROT DATE lt year gt lt month gt lt day gt CAL PROT NDUE lt year gt lt month gt lt day gt ie CAL PROT SAVE CAL PROT LOCK 5 5 Model 7700 calibration The following procedures calibrate the temperature sensors on the Model 7700 plug in modules NOTE For additional information about the Keithley modules refer to the module documentation Recommended test equipment In order to calibrate the Model 7700 you will need equipment summarized in Table 2 14 Table 2 14 Recommended equipment for Model 7700 calibration Digital Thermometer 18 to 28 C 0 1 Keithley 7797 Calibration Extender Board 2 24 Calibration Model 2750 Multimeter Switch System Service Manual Extender board connections The Model 7700 being calibrated should be connected to the 7797 Calibration Extender Board and the extender board should then be installed in scanner Slot 1 Note that the module being calibrated will be external to the Model 2750 to avoid card heating during calibration Model 7700 calibration NOTE Before calibrating the Model 7700
111. e With the power off install the Model 7700 7797 combination in Slot 1 and select the rear inputs with the INPUTS switch Allow three minutes for thermal equilib rium Accurately measure and record the cold temperature of the Model 7700 card sur face at the center of the card Press in and hold the Model 2750 OPEN key while turning on the power Enable calibration by sending the CODE command For example the default com mand is CAL PROT CODE KI002750 Initiate calibration by sending the following command CAL PROT CARDI INIT Calibrate the Model 7700 with the following command CAL PROT CARDI STEPO temp Here temp is the cold calibration temperature measured in Step 3 Send the following commands to save calibration and lock out calibration CAL PROT CARDI SAVE CAL PROT CARDI LOCK N e 2 A E 5 2 26 Calibration Model 2750 Multimeter Switch System Service Manual 3 Routine Maintenance 5 oO EO 5 z 5 5 fs 3 2 Routine Maintenance Model 2750 Multimeter Switch System Service Manual Introduction The information in this section deals with routine type maintenance and includes proce dures for setting the line voltage replacing the Model 2750 line and front terminal AMPS fuses and replacing the amps fuses for the Models 7700 plug in module Replacement of the Model 2750 non volatile RAM battery and reading module relay card cl
112. e Crescent Bangalore 560 001 91 80 509 1320 21 Fax 91 80 509 1322 ITALY Keithley Instruments s r l Viale S Gimignano 38 20146 Milano 02 48 39 16 01 Fax 02 48 30 22 74 NETHERLANDS Keithley Instruments B V Postbus 559 4200 AN Gorinchem 0183 635333 Fax 0183 630821 SWITZERLAND Keithley Instruments SA Kriesbachstrasse 4 8600 D bendorf 01 821 94 44 Fax 01 820 30 81 TAIWAN Keithley Instruments Taiwan 1 Fl 85 Po Ai Street Hsinchu Taiwan R O C 886 3572 9077 Fax 886 3572 903 9 00 Model 2750 Multimeter Switch System Service Manual 2001 Keithley Instruments Inc All rights reserved Cleveland Ohio U S A First Printing March 2001 Document Number 2750 902 01 Rev A Manual Print History The print history shown below lists the printing dates of all Revisions and Addenda created for this manual The Revision Level letter increases alphabetically as the manual undergoes sub sequent updates Addenda which are released between Revisions contain important change in formation that the user should incorporate immediately into the manual Addenda are numbered sequentially When a new Revision is created all Addenda associated with the previous Revision of the manual are incorporated into the new Revision of the manual Each new Revision includes a revised copy of this print history page Revision A Document Number 2750 902 01 March 2001 All Keit
113. e steps to verify DC voltage accuracy 1 Connect the Model 7700 and L INPUT terminals to the DC voltage calibra tor as shown in Figure 1 9 NOTE Use shielded low thermal connections when testing the 100 and 1V ranges to avoid errors caused by noise or thermal effects Connect the shield to the cal ibrator s output LO terminal CH1 Calibrator Output DC Voltage wal Output HI 9 ang e o d SIG 8 C ame HEO oue 090 GO O l mi GEO B e Qa eb fo d Output LO Note Use shielded low thermal cables Model 7700 for 100mV and 1V ranges 2 Install the Model 7700 in Slot 1 of the Model 2750 then turn on the power and allow the unit to warm up for two hours before proceeding Be sure the front panel INPUTS switch is set to the REAR position 3 Select the DC volts function by pressing the DCV key and set the Model 2750 to the 100mV range Close Channel 1 by pressing the CLOSE key then ENTER for SINGLE channel and then keying in 101 4 Se
114. ed DC STEP11 Purpose To program the 100mA comprehensive calibration step Format cal prot dc stepll Cal current Parameters Cal current 90E 3 to 110E 3 A Description STEP11 programs the 100mA comprehensive calibration step The allowable range of the calibration current parameter is from 90E 3 to 110E 3 Use the 100E 3 value whenever possible for best results Example CAL PROT DC STEP11 0 1 Program 100mA step STEP12 CALibration PROTected DC STEP1 2 Purpose To program the 1A comprehensive calibration step Format cal prot de step12 Cal current Parameters Cal current 0 9 to 1 1 A Description STEP12 programs the 1A comprehensive calibration step The allow able range of the calibration current parameter is from 0 9 to 1 1 Usea value of 1 whenever possible for best results Example CAL PROT DC STEP12 1 Program 1A step Model 2750 Multimeter Switch System Service Manual Calibration Reference 13 AC calibration commands The AC commands perform comprehensive user calibration of the ACV and ACI func tions Table B 3 summarizes these calibration commands Table B 3 AC calibration commands Command Description CALibration PROTected AC STEP 1 10mV AC at 1kHz calibration step STEP2 100mV AC at 1kHz calibration step STEP3 100mV AC at 50kHz calibration step 5 4 1V AC at 1kHz calibration step STEPS 1V AC at 50kHz calibration step STEP6 10V AC at 1kHz calibratio
115. el N 1 e lt t 2 5 Note Use shielded low thermal cables for 100mV and 1V ranges 2 Select DC volts function by pressing the key and set the Model 2750 to the 100mV range 3 Set the calibrator output to 0 00000mV DC and allow the reading to settle Enable the Model 2750 REL mode Leave REL enabled for the remainder of the DC volts verification test 5 Source positive and negative and full scale voltages for each of the ranges listed in Table 1 2 For each voltage setting be sure that the reading is within stated limits Table 1 2 DCV reading limits Range Applied DC Voltage Reading Limits 1 year 18 C to 28 C 100mV 100 0000mV 99 9935 to 100 0065mV 1V 1 000000V 0 999963 to 1 000037V 10V 10 00000V 9 99965 to 10 00035V 100V 100 0000V 99 9946 to 100 0054V 1000V 1000 000V 999 931 to 1000 069V Source positive and negative values for each range Refer to specifications DC note 5 for signal gt 500V 1 10 Performance Verification Model 2750 Multimeter Switch System Service Manual Verifying AC voltage Check AC voltage accuracy by applying accurate AC voltages at specific frequencies from the AC voltage calibrator to the Model 2750 inputs and verifying that the displayed read ings fall within specified ranges CAUTION Do not exceed 1000V peak between front terminals INPUT HI and INPUT LO or 8 x 10
116. erifying AC current Check AC current accuracy by applying accurate AC voltage current at specific frequen cies from the AC current calibrator to the Model 7700 input terminals and verify that the displayed readings fall within specified limits Follow these steps to verify AC current 1 Connect the Model 7700 CH21 and L terminals to the calibrator as shown in Figure 1 12 2 Install the Model 7700 in Slot 1 of the Model 2750 then turn on the power and allow the unit to warm up for two hours before proceeding Be sure the front panel INPUTS switch is set to the REAR position 3 Select the AC current function by pressing the ACI key 4 Set the Model 2750 for the range Close Channel 21 by pressing the CLOSE key then ENTER for SINGLE channel and keying in 121 Figure 1 12 Connections for Model 7700 AC current verification Model 7700 52 ili yu Output HI uka 2 CH21 Calibrator Output AC Current C C OOO OOO OO Q C e J e e I t 2
117. error 409 10M 2 w zero error ie 410 10M 2 w full scale error 411 10M 2 w open error 5 412 100 4 w zero error 413 10k 4 w zero error e 414 100k 4 w zero error 2 415 4 w sense lo zero error 416 100 4 w full scale error B 22 Calibration Reference Model 2750 Multimeter Switch System Service Manual Table B 5 continued Calibration errors Error Number Error Message 417 10k 4 w full scale error 418 100k 4 w full scale error 419 1M 4 w full scale error 420 10M 4 w full scale error 421 10m adc zero error 422 100m adc zero error 423 10m adc full scale error 424 100m adc full scale error 425 1 adc full scale error 426 10 4 w zero error 427 1k 4 w zero error 428 10 2 w zero error 429 10k 4 w ocomp Ioff full scale error 430 10k 4 w ocomp Ion full scale error 438 Date of calibration not set 439 Next date of calibration not set 450 100m vac dac error 451 1 vac dac error 452 10 vac dac error 453 100 vac dac error 454 100m vac zero error 455 100m vac full scale error 456 vac zero error 457 1 vac full scale error 458 1 vac noise error 450 10 vac zero error 460 10 vac full scale error
118. eset ON ON ON OFF OFF OFF K103 set states Pin 8 to 7 Pin 3 to 4 K103 reset states Pin 8 to 9 Pin 3 to 2 Model 2750 Multimeter Switch System Service Manual Troubleshooting 4 21 Table 4 14 through Table 4 19 can be used to trace the analog signal through the A D mul tiplexer U163 to the final amplifier stage These tables show the MUX lines S3 S4 S6 57 that are selected for measurement during the SIGNAL phase of the multiplexing cycle Also included are switching states of analog switches U129 that set up the gain for the final amplifier stage U166 Table 4 14 DCV signal multiplexing and gain Signal U129 U129 U129 Gain Range U163 Pin 1 Pin 8 Pin9 U166 100mV S4 OFF OFF ON x100 1V S4 OFF ON OFF x10 10V S4 ON OFF OFF xl 100V S4 OFF ON OFF x10 1000V S4 ON OFF OFF xl Table 4 15 ACV and ACA signal multiplexing and gain Signal U129 U129 U129 Gain Range U163 Pin 1 Pin 8 Pin9 U166 All S3 ON OFF OFF 1 Table 4 16 DCA signal multiplexing and gain Signal U129 U129 U129 Gain Range U163 Pin 1 Pin 8 Pin9 U166 20mA S6 OFF OFF ON x100 100mA S6 OFF OFF ON x100 1A S6 OFF OFF ON x100 3A S6 OFF ON OFF x10 E oO E ge 4 22 Troubleshooting Model 2750 Multimeter Switch System Service Manual Table 4 17 Q2 signal multiplexing and gain
119. esistance Parameters Cal resistance 90E3 to 1 10E3 Q Description STEP8 programs the 100kQ 4 wire resistance comprehensive calibra tion step The allowable range of the calibration resistance parameter is from 90E3 to 110E3 but 100E3 is recommended for best results Example CAL PROT DC STEP8 100E3 Program 100kQ step 5 9 CALibration PROTected DC STEP9 Purpose To program IMQ comprehensive calibration step Format cal prot dc step9 Cal resistance Parameters Cal resistance 900E3 to 1 1E6 Description STEP9 programs IMQ comprehensive calibration step The allow able range of the calibration resistance parameter is from 900E3 to 1 1E6 Use the 1E6 value whenever possible or the closest possible value Example CAL PROT DC STEP9 Program 1MQ calibration step STEP10 CALibration PROTected DC STEP1 0 Purpose To program the 10mA comprehensive calibration step Format cal prot dc step10 Cal current Parameters Cal current 9E 3 to 11E 3 A Description STEP10 programs the 10 comprehensive calibration step The allowable range of the calibration current parameter is from 9E 3 to 11E 3 Use the 10E 3 value whenever possible for best results Example CAL PROT DC STEP10 10E 3 Program 10mA step g E 3 e oO oO e oO B 12 Calibration Reference Model 2750 Multimeter Switch System Service Manual STEP11 CALibration PROTect
120. g Rack mount kit Model 4288 7 rack mount kit Mounts a Model 2750 in a standard 19 inch rack Includes rear brackets to provide additional support for a mainframe that has two or more switching modules installed NOTE Model 2750 includes hardware that allows it to be mounted to the front rails of a standard 19 inch rack With two or more switching modules installed rear support brackets may be required The Model 4288 7 rack mount kit includes rear support brackets Rack mount procedure The Model 2750 can be mounted in a standard 19 inch rack For a mainframe that has one or no switching modules installed the Model 2750 can be secured to the front rails of the rack The hardware necessary to secure the mainframe to the front rails of the rack is supplied with the Model 2750 The supplied hardware kit includes four dress screws and four retaining clips Each retaining clip has a captive nut Perform the following steps to mount the Model 2750 to the front rails of the rack WARNING Make sure the Model 2750 is turned off the line cord is disconnected and it is not connected to any external circuitry 1 Select a location in the rack The mainframe takes up 3 5 inches of vertical space Model 2750 Multimeter Switch System Service Manual Routine Maintenance 3 11 2 Using Figure 3 4 as a guide install two retaining clips on the left front rail Slide each retaining clip over a mounting hole such that the captive nut is pos
121. g Q tg CASE 4 6 H UT OUTPUT OUTPUT OUTPUT OUTP ENTER 4 R RS Cmd Cmd CASE 10 13 23 J AMPS IF I 13 THEN J PRINT 1 PRINT GOSUB KeyCheck PRINT 1 PRINT 1 P dE db db db db NK b b b b S END SELECT IF I gt 2 THEN GOSUB Settle PRINT 1 OUTPUT 16 C Cmd GOSUB CalEnd GOSUB ErrCheck NEXT I RINT 1 OUTPUT INPUT Enter RINT 1 OUTPUT OSUB ErrCheck INPUT Enter 1 OUTPUT ErrCheck RINT 1 OUTP ErrCheck RINT 1 OUTPUT 16 CAL PROT LOCK Calibration completed RINT 1 OUTPUT 16 SYST PRES 4 STBY calibration date 16 CAL P H z ROT DATE calibration 16 CAL PROT NDUE UT 16 CAL PROT SAVE tg tg tg Q tg GO E Q tg E mg KeyCheck WHILE INKEYS lt gt PRINT WEND OUTPUT 4 OUTPUT 4 OPER yyyy mm dd due date PRINT Press any key to continue Model 2750 Multimeter Switch System Service Manual Select cal sequence Connect calibrator to INPUT and SENSE jacks Wait 3 minutes UT 4 EXTSENSE OFF UT 4 Msg UT 4 OPER 24 25 UT 4 Msg 4 OPER 4 Msg 4 EXTSENSE ON 4 OPER UT 4 OUT STRS R INPUT HI OUTPUT 4 STBY Connect calibrator to J and INPUT LO jacks Msg Send cal command to 2750 Wait until cal step ends
122. g can occur on 1006 or J1007 0192 allows hardware handshaking to external controllers by gating off triggers U188 and U189 provide digital output The two driver ICs U188 and U189 provide cur rent sink capability of 250mA each Module slot control U122 U127 U170 U173 U174 U195 and U196 make up the control circuitry that allows communication of relay data to Slot 1 Slot 2 Slot 3 Slot 4 or Slot 5 Line sync U179 U180 U181 U182 U183 U184 and U186 are used to control A D triggers syn chronized at the zero cross point of the power line voltage U186 controls zero crossing detection while U182 and U183 preserve the trigger states until the zero crossing thresh old is detected Analog circuitry Refer to Figure 4 3 for the following discussion on analog circuitry Model 2750 Multimeter Switch System Service Manual Troubleshooting 4 9 Figure 4 3 Analog circuitry block diagram A D MUX Overload Protection Digital Q103 107 117 Circuitry Front Terminals CR101 113 See Figure 4 2 U128 140 143 Ws 1 EO Scanner Outputs AMPS Current Shunts K103 R158 R205 R338 AC Switching amp Gain bota ETIN 5101 mas EE FREQ DCV amp Ohms Ge INPUT SSP Switching Gai Scanner Outputs HI Q101 Q102 K101 Q104 u1 29 01 32 Q108 Q113 U163 U166 Dry Circuit Stability Clamp C152 C164 SSP 105 0159 DCV Divider R117 Q109 Q114 Q136 K104 Ohms
123. g command Change the current parameter if you are using a different calibration current Wait until the Model 2750 completes each step before continuing NOTE Ifyou are performing DC only calibration proceed to Programming calibra tion dates Table 2 10 DC current calibration programming steps Calibration Calibrator Step Current Calibration Command Parameter Range 10mA 10 00000mA CAL PROT DC STEP10 10E 3 9E 3 to 11E 3 100mA 100 00000mA CAL PROT DC STEP11 100E 3 90E 3 to 110E 3 1A 1 000000A CAL PROT DC STEP12 1 0 9 to 1 1 Change parameter if using different current gt e N N gt 2 18 Calibration AC voltage calibration Model 2750 Multimeter Switch System Service Manual Follow these steps for AC voltage calibration 1 Connect the calibrator to Model 2750 INPUT HI and LO terminals as shown in Figure 2 4 2 Perform the calibration steps summarized in Table 2 11 For each step Set the calibrator to the indicated voltage and frequency and make sure the unit is in operate You must use the stated voltage and frequency Send the indicated programming command Wait until the Model 2750 completes each step before continuing Table 2 11 AC voltage calibration programming steps Calibration Step Calibrator Voltage Frequency Calibration Command 10mV AC at 1kHz 100mV AC at 1kHz 100mV AC at 50kHz 1VAC
124. generator to output RMS 3Hz sine wave Use the left and right arrow keys and the range keys to adjust the dis play to agree with the generator amplitude you measured previously then press ENTER Frequency cal Set the function generator to output a 1V RMS 1kHz sine wave Enter 1 000000KHz at the prompt then press ENTER 9 Setthe calibration dates then save calibration to complete the process Remote manufacturing calibration 1 Install the shorted calibration extender board see Extender board preparation earlier in this section in scanner card Slot 1 and select the rear inputs with the INPUTS switch Allow three minutes for thermal equilibrium 2 Press in and hold the OPEN key while turning on the power 3 Enable calibration by sending the CODE command For example the default com mand is CAL PROT CODE K1002750 4 Initiate calibration by sending the following command CAL PROT INIT 5 Calibrate step 0 with the following command CAL PROT DC STEPO Model 2750 Multimeter Switch System Service Manual Calibration 2 23 6 Perform the entire remote comprehensive calibration procedure discussed earlier in this section See Comprehensive calibration earlier in this section 7 Connect the function generator to the Model 2750 INPUT jacks as shown in Figure 2 5 Select the front input jacks with the INPUTS switch 8 Set the generator to output a 1V RMS 3Hz sine wave then send the following comman
125. han corresponding Model 2750 specifications Table 2 1 Recommended equipment for comprehensive calibration Fluke 5700A Calibrator AC Voltage AC Current DC Voltage 1kHz 50kHz DC Current 1kHz Resistance 10V 5ppm 10mV 710ppm 10mA 60ppm 100mA 190ppm 1000 17ppm 100V 7ppm 100mV 200ppm 100mA 70ppm 1A 690ppm 10kQ 1 1ppm 1V 82ppm 1A 110ppm 2 670ppm 100 13ppm 10V 82ppm IMQ 18 100V 90ppm 700V 85ppm Miscellaneous Equipment Keithley 8610 low thermal shorting plug Double banana plug to double banana plug shielded cable BNC to double banana plug shielded cable 1kHz specifications 10 and 700V points require 1kHz only calibrator specifications are 90 day 23 C 5 C specifications and indicate total absolute uncertainty at specified output gt e N N zu gt 2 6 Calibration Model 2750 Multimeter Switch System Service Manual Aborting calibration You can abort the front panel calibration process at any time by pressing EXIT The instru ment will then ask you to confirm your decision to abort with the following message ABORT CAL Press EXIT to abort calibration at this point or press any other key to return to the calibra tion process NOTE The Model 2750 will not respond to any remote programming commands while the ABORT CAL message is displayed Front panel calibration Follow the
126. hat secure it to the chas sis although it is not necessary to remove the motherboard to do so Front panel disassembly Use the following procedures to remove the display board and or the pushbutton switch pad NOTE You must first remove the case cover and the front rear input switch rod and dis connect the front input terminal wires as described earlier in this section Unplug the display board ribbon cable from connector J1014 if you have not already done so Remove the front panel assembly Remove the four screws two on each side and two internal kep nuts that secure the front panel to the chassis then pull the front panel assembly forward until it separates from the chassis Remove the four screws that secure the display board to the front panel Pull the display board from the front panel Remove the switch pad by pulling it from the front panel Removing power components The following procedures to remove the power transformer and or power module require that the case cover be removed as previously explained Power transformer removal Perform the following steps to remove the power transformer 1 Disconnect the two power cables connected to the motherboard and the wires going to the rear panel power module Remove the two nuts that secure the transformer to the bottom of the chassis Pull the black ground wire off the threaded stud and remove the power transformer from the chassis J S 7 3
127. he INPUTS switch is in the FRONT position 2 Setthe function generator to output a IKHz IV RMS sine wave 3 Select the Model 2750 frequency function by pressing the FREQ key 4 Verify that the Model 2750 frequency reading is between 999 9Hz and 1 0001kHz Figure 1 8 Connections for Model 2750 frequency verification Function Generator BNC to Dual Model 2750 Banana Plug Front Panel Adapter Function Output Model 7700 verification Use these procedures to verify measurement accuracy through the Model 7700 20 Channel Multiplexer Card NOTE Although the following tests are based on the Model 7700 20 Channel Multi plexer the same general procedures can be used for other plug in modules that have similar capabilities Refer to module documentation for specific informa tion on terminals and connections for other plug in modules Model 2750 Multimeter Switch System Service Manual Performance Verification 1 21 Verifying DC voltage Figure 1 9 Connections for Model 7700 DC volts verification Check DC voltage accuracy by applying accurate voltages from the DC voltage calibrator to the Model 7700 input terminals and verifying that the displayed readings fall within specified limits CAUTION Do not exceed 300V DC between the 7700 plug in module INPUT H and L terminals or between any adjacent channels Follow thes
128. he instrument was not damaged during shipment and that the unit meets factory specifications Ifthe instrument s accuracy is questionable Following calibration WARNING information this section is intended only for qualified service personnel Do not attempt these procedures unless you are qualified to do so NOTE Ifthe instrument is still under warranty and its performance is outside specified limits contact your Keithley representative or the factory to determine the cor rect course of action If the unit is not under warranty and it fails to meet speci fied limits refer to the calibration procedures in Section 2 There are two general verification procedures in this section Model 2750 verification Covers procedures to verify measurement accuracy of the Model 2750 using the front panel terminals Model 7700 verification Discusses procedures to verify accuracy of measure ment made through the Model 7700 20 Channel Multiplexer Note that the same general procedures can be used to verify measurement accuracy of other Model 2750 plug in modules that have similar functions For specific information about the individual modules refer to the corresponding module documentation Model 2750 Multimeter Switch System Service Manual Performance Verification 1 3 Verification test requirements Be sure that you perform the verification tests Under the proper environmental conditions After the specified
129. here it converts the analog signals to digital form The digital signals are then routed through an opto isolator to the MPU to calculate a reading The multiplexer amplifier has an overload protection circuit The circuit reduces the multi plexer gain to unity during overload conditions This circuit is made up of primarily CR101 CR113 0103 Q107 Q117 0128 U140 U143 VR110 and VR111 Scanner card signals Scanner card input signals are connected directly to installed scanner cards Scanner card output signals are routed internally to the INPUTS switch which selects between the front panel terminals and the scanner card outputs The Model 7700 7706 and 7708 modules contain CJC voltage temperature sensors These sensors are multiplexed into U163 at various phases of the measurement cycle Dry circuit ohms Figure 4 4 shows a simplified schematic of the dry circuit ohms circuitry Dry circuit ohms measurements are made similar to those for conventional ohms in that a IDOA to 10 current source depending on ohms range forces a current through the DUT resistance and the voltage across the device is measured In the case of dry circuit ohms however there are two clamps that act to limit the voltage across the DUT to 20mV Normally the voltage is sensed across the SENSE HI and LO terminals and the main clamp restricts the DUT voltage to 20mV A secondary clamp monitors the voltage across INPUT HI and LO and acts to restrict the vol
130. hing Range 0101 Q102 0151 0150 0114 0136 0109 100mV ON ON OFF OFF OFF OFF OFF IV ON ON OFF OFF OFF OFF OFF 10V ON ON OFF OFF OFF OFF OFF 100V OFF OFF OFF OFF ON ON OFF 1000V OFF OFF OFF OFF ON ON OFF Range K101 Q113 Q104 Q108 Q106 Q148 100mV SET OFF ON OFF OFF ON 1V SET OFF ON OFF OFF ON 10V SET OFF ON OFF OFF ON 100V SET OFF OFF ON OFF ON 1000 SET OFF OFF ON OFF ON K101 set states Pin 8 switched to Pin 7 Pin 3 switched to Pin 4 reset states Pin 8 switched to Pin 9 Pin 3 switched to Pin 2 E oO E ge 4 16 Troubleshooting Model 2750 Multimeter Switch System Service Manual Table 4 6 ACV and FREQ signal switching U103 U103 Range Q101 Q102 K101 K102 Pin8 Pin9 100mV ON ON RESET RESET ON ON IV ON ON RESET RESET ON ON 10V ON ON RESET SET OFF OFF 100V ON ON RESET SET OFF OFF 750V ON ON RESET SET OFF OFF 0105 0105 0103 0103 0105 0111 Range Pin9 Pin8 16 1 Pin1 Pin 16 100mV OFF OFF OFF ON ON OFF 1V OFF OFF ON OFF OFF OFF 10V ON OFF OFF ON ON OFF 100V ON OFF ON OFF OFF OFF 750V ON ON OFF OFF OFF OFF K101 and K102 reset states Pin 8 switched to Pin 9 Pin 3 switched to Pin 2 K101 and K102 set states Pin 8 switched to Pin 7 Pin 3 switched to Pin 4 Model 2750
131. hley product names are trademarks or registered trademarks of Keithley Instruments Inc Other brand names are trademarks or registered trademarks of their respective holders Safety Precautions The following safety precautions should be observed before using this product and any associated in strumentation Although some instruments and accessories would normally be used with non hazardous voltages there are situations where hazardous conditions may be present This product is intended for use by qualified personnel who recognize shock hazards and are familiar with the safety precautions required to avoid possible injury Read the operating information carefully before using the product The types of product users are Responsible body is the individual or group responsible for the use and maintenance of equipment for ensuring that the equipment is operated within its specifications and operating limits and for ensuring that operators are adequately trained Operators use the product for its intended function They must be trained in electrical safety procedures and proper use of the instrument They must be protected from electric shock and contact with hazardous live circuits Maintenance personnel perform routine procedures on the product to keep it operating for example setting the line voltage or replacing consumable materials Maintenance procedures are described in the manual The procedures explicitly state if the operator may
132. istance function by pressing the 4 key then choose the SLOW integration rate with the RATE key 4 Set the Model 2750 for the 1Q range and make sure the FILTER is on Enable OCOMP offset compensated ohms by pressing SHIFT then OCOMP Use OCOMP for 1Q 10Q and 100 range verification 5 Recalculate reading limits based on actual calibrator resistance values 6 Source the nominal full scale resistance values for the 1Q 10MQ ranges summa rized in Table 1 6 and verify that the readings are within calculated limits 7 Connect the Model 2750 INPUT and SENSE jacks to the calibrator as shown in Figure 1 6 N 1 e e lt t 2 5 8 Disable external sense on the calibrator 9 Set the Model 2750 for the 100MO range 10 Source a nominal 100MQ resistance value and verify that the reading is within cal culated limits for the 100MO range Figure 1 6 Connections for Model 2750 resistance verification 100 range Calibrator Output 2 wire Resistance Model 2750 Front Panel O Note Use shielded cables to minimize noise Disable calibrator external sense mode 1 16 Performance Verification Model 2750 Multimeter Switch System Service Manual Table 1 6 Limits for normal resistance verification Nominal Nominal Reading Limits O Range Resistance 1 year 18 C to 28 C Recalculated Limits
133. it for the following display TYPE PT385 f Press ENTER to complete the temperature configuration process 5 Setthe decade resistance box to each of the values shown in Table 1 17 and verify that the temperature readings are within the required limits Open Channel 1 when finished J e e I t EA e E E Table 1 17 Plug in module four wire RTD temperature verification reading limits Applied Resistance Reading Limits 1 year 18 C to 28 C 22 800 190 06 to 189 94 100 000 0 06 to 0 06 313 590 599 94 to 600 06 Based on o 0 00385 See text 1 34 Performance Verification Model 2750 Multimeter Switch System Service Manual Verifying frequency Follow the steps below to verify the Model 2750 frequency function 1 Connect the function generator to the Model 7700 H and L INPUT terminals Figure 1 17 2 Install the Model 7700 in Slot 1 of the Model 2750 then turn on the power and allow the unit to warm up for one hour before proceeding Be sure the front panel INPUTS switch is set to the REAR position 3 Set the function generator to output a 1kHz 1V RMS sine wave Select the Model 2750 frequency function by pressing the FREQ key Close Chan nel 1 by pressing the CLOSE key then ENTER for SINGLE channel and keying in 101 5 Verify that the Model 2750 frequency reading is between 0 9999kHz and 1 0001kHz Figure 1 17 Connections for
134. itioned on the inside of the rack cabinet In a similar manner install two retaining clips on the right front rail Figure 3 4 Rack preparation Left Front Rack Rail Retaining Clips with Nuts 3 Remove the four foot assemblies from the bottom of the Model 2750 The retaining screw for an assembly is located under the rubber foot Simply pull off the rubber feet to gain access to the screws Retain these foot assemblies for future use 4 Position the Model 2750 in the rack and loosely attach the front panel to the rack rails using the four supplied dress screws 5 Tighten the four dress screws CAUTION For a Model 2750 that has two or more installed switching modules rear brackets may be required to support the additional weight The Model 4288 7 is a rack mount kit for the Model 2750 that uses rear support brackets oO E 3 oO E E e oO 3 12 Routine Maintenance Model 2750 Multimeter Switch System Service Manual Troubleshooting 4 2 Troubleshooting Model 2750 Multimeter Switch System Service Manual Introduction This section of the manual will assist you in troubleshooting and repairing the Model 2750 Included are self tests test procedures troubleshooting tables and circuit descrip tions It is left to the discretion of the repair technician to select the appropriate tests and documentation needed to troubleshoot the instrument Refer to the disassembly proce dures in Sectio
135. kQ to kQ Enable OCOMP offset compensated ohms when testing 1Q 10Q 100Q and 1kQ ranges Calculate limits based on actual calibration resistance values and Model 2750 one year dry circuit resistance accuracy specifications See Verification limits Verifying temperature Thermocouple thermistor and RTD temperature readings are derived from DC volts and resistance measurements respectively For that reason it is not necessary to independently verify the accuracy of temperature measurements As long as the DC volts and resistance functions meet or exceed specifications temperature function accuracy is automatically verified However temperature verification procedures are provided below for those who wish to separately verify temperature accuracy Thermocouple temperature 1 Connect the DC voltage calibrator output terminals to the Model 2750 INPUT jacks using low thermal shielded connections Use 2 wire connections similar to those shown in Figure 1 1 Be sure the INPUTS switch is in the FRONT position 2 Configure the Model 2750 for C units type J temperature sensor and 0 C simu lated reference junction as follows a b Press SHIFT then SENSOR and note the unit displays the temperature units UNITS C If necessary use the cursor and range keys to select C units Press ENTER The unit displays the sensor type SENS TCOUPLE Make sure that TCOUPLE is displayed then press ENTER The unit
136. l sensing is to be turned on 2 Setthe calibrator to output DC volts and turn external sense off 3 Perform the steps listed in Table 2 3 to complete DC volts calibration For each calibration step Set the calibrator to the indicated value and make sure it is in OPERATE Press the ENTER key to calibrate that step Wait until the Model 2750 finishes each step The unit will display the CALI BRATING message while calibrating NOTE lIfyour calibrator cannot output the values recommended in Table 2 3 use the left and right arrow keys and the up and down range keys to set the Model 2750 display value to match the calibrator output voltage Table 2 3 DC volts calibration summary Calibration Step Calibrator Voltage Allowable Range 10V 10 00000V 9V to 11V 10V 10 00000V 9 to 11V 100V 100 0000V 90V to 110V gt N N E 2 10 Calibration Model 2750 Multimeter Switch System Service Manual Resistance calibration Completing the 100V DC calibration step ends the DC voltage calibration procedure The Model 2750 will then prompt you to connect 100Q Follow these steps for resistance calibration 1 Set the calibrator output for resistance and turn on external sense NOTE Use external sense 4 wire when calibrating all resistance ranges Be sure that the calibrator external sense mode is turned on 2 Perform the calibration steps summa
137. ltimeter Switch System Service Manual Table 6 2 Model 2750 display board parts list Circuit Designation Description Keithley Part No C401 C405 C407 C409 C412 CAP 1UF 20 50V CERAMIC C 418 1 C406 C408 CAP 33PF 10 100V CERAMIC C 451 33P C413 CAP 22UF 20 6 3 TANTALUM C 417 22 C414 CAP 47PF 1096 100V CERAMIC C 451 47P C415 C416 CAP 1000PF 10 100V CERAMIC C 451 1000P CR401 CR402 DIODE MBRO520LT1 RF 103 DS401 DISPLAY DD 61 JI CONN RT ANGLE HEADER 16 PIN CS 1066 3 LED1 LED2 LED3 LED4 LED5 PILOT LIG HSMH T400 LED PL 92 1 LPIL LPD LPIS LPIA LPIS VERTICAL LIGHT PIPE PL 117 1 R401 R404 R406 R409 R411 RES 15k 1 1000MW THICK FILM R 418 15K R414 R418 R405 R408 R410 R412 RES 12 1 1 1 4W METAL FILM R 391 12 1 R413 RES 13K 1 100MW THICK FILM R 418 13K R419 RES 10M 5 125MW METAL FILM R 375 10M R420 R421 RES 10K 1 100MW THICK FILM R 418 10K R451 R455 RES 1 21K 1 1000MW THICK FILM R 418 1 21K 0401 PROGRAMMED MICROCONTROLLER 2750 802A01 U402 U403 IC LATCHED DRIVERS UCN 5812EPF 1 732 U406 IC DARLINGTON ARRAY ULN2003L IC 969 Y401 CRYSTAL 4MHZ CR 36 4M Order current firmware revision for example 01 Model 2750 Multimeter Switch System Service Manual Replaceable Parts 6 13 Table 6 3 Model 2750 backplane board parts list Circuit Designation Description Keithley Part No ILD CONN 2 ROWS OF 16 PINS CS 736 4 J1 J2 J3 CONN 2 ROWS OF 16
138. lue Using Model 2750 one year 10kQ range accuracy of 100ppm of reading 6ppm of range the calculated reading limits are Reading limits 10 03kQ 10 03kQ x 100ppm 10kQ x 6ppm Reading limits 10 02894kQ to 10 03106kQ 1 6 Performance Verification Model 2750 Multimeter Switch System Service Manual Restoring factory defaults Before performing the verification procedures restore the instrument to its factory defaults as follows 1 Press SHIFT and then SETUP The instrument will display the following prompt RESTORE FACT 2 Using either range key select FACT then restore the factory default conditions by pressing ENTER Performing the verification test procedures Verification test summary Verification tests can be performed either through the Model 2750 front panel terminals or through plug in modules This section contains the following procedures Model 2750 verification Use this procedure to test Model 2750 accuracy through the front panel terminals Model 7700 verification Use this procedure to test accuracy through any of the available plug in modules with the same functions as the Model 7700 20 Channel Multiplexer Card Model 2750 tests Model 2750 verification test procedures include DC volts AC volts DC current e AC current Resistance Temperature Frequency Model 2750 Multimeter Switch System Service Manual Performance Verification 1 7 Model 7700 tests Model 7
139. mentarily on power up E oO E ge Memory circuits ROMs U156 and U157 store the firmware code for instrument operation U157 stores the DO D7 bits of each data word U156 stores the D8 D15 bits RAMs U151 U152 U164 and U193 provide battery backed operating storage 4 8 Troubleshooting Model 2750 Multimeter Switch System Service Manual Semi permanent storage facilities include NVRAM U136 This IC stores such information as instrument setup and calibration constants Data transmission from this device is done in a serial fashion U194 U171 Y103 and BT100 make up the battery watchdog control along with the real time clock U171 automatically senses when the 5VD supply is being powered down and then switches to BT100 for power RS 232 interface Serial data transmission and reception is performed by the TXD and RXD lines of the MPU U159 provides the necessary voltage level conversion for the RS 232 interface port IEEE 488 interface U158 U160 and U161 make up the IEEE 488 interface U158 a 9914A GPIA takes care of routine bus overhead such as handshaking while U160 and U161 provide the necessary buffering and drive capabilities Trigger circuits Buffering for Trigger Link input and output is performed by U146 Trigger input and out put is controlled by the TP5 and PC2 lines of the MPU Digital I O U146 U191 and U192 make up the digital input circuitry External triggerin
140. mming steps 2 16 Resistance calibration programming steps 2 16 DC current calibration programming steps 2 17 AC voltage calibration programming steps 2 18 AC current calibration programming steps 2 19 Recommended equipment for manufacturing calibration 2 20 Recommended equipment for Model 7700 calibration 2 23 Routine Maintenance Power line fuse sa 3 3 Closure count commands ra 3 8 4 Table 4 1 Table 4 2 Table 4 3 Table 4 4 Table 4 5 Table 4 6 Table 4 7 Table 4 8 Table 4 9 Table 4 10 Table 4 11 Table 4 12 Table 4 13 Table 4 14 Table 4 15 Table 4 16 Table 4 17 Table 4 18 Table 4 19 Table 4 20 5 Table 5 1 Table 5 2 6 Table 6 1 Table 6 2 Table 6 3 Table 6 4 Table 6 5 B Table B 1 Table B 2 Table B 3 Table B 4 Table B 5 Troubleshooting Power supply components rra 4 5 Display board checks rr 4 13 Power supply checks rr 4 13 Digital circuitry checks rr 4 14 DCV signal switching rr 4 15 ACV and FREQ signal switching rrura 4 16 Q2 signal switching rr 4 17 O4 signal switching adar taeraren 4 18 Q4 dry circuit signal switching rra 4 19 92 04 reference signal switching 4 19 Q4 dry circuit reference signal switching 4 20 DCA signal switching sr 4 20 signal switching sr 4 20 DCV signal m
141. mmon mode voltages Use standard safety precautions to avoid personal contact with these voltages The WARNING heading in a manual explains dangers that might result in personal injury or death Always read the associated information very carefully before performing the indicated procedure The CAUTION heading in a manual explains hazards that could damage the instrument Such damage may invalidate the warranty Instrumentation and accessories shall not be connected to humans Before performing any maintenance disconnect the line cord and all test cables To maintain protection from electric shock and fire replacement components in mains circuits including the power transformer test leads and input jacks must be purchased from Keithley Instruments Standard fuses with applicable national safety approvals may be used if the rating and type are the same Other components that are not safety related may be purchased from other suppliers as long as they are equivalent to the original component Note that selected parts should be purchased only through Keithley Instruments to maintain ac curacy and functionality of the product If you are unsure about the applicability of a replacement component call a Keithley Instruments office for information To clean an instrument use a damp cloth or mild water based cleaner Clean the exterior of the instrument only Do not apply cleaner directly to the instrument or allow liquids to enter or spill on
142. n 3 switched to Pin 2 Table 4 10 92 04 reference signal switching Range Q159 Q158 Q157 U133 0 7V U133 7V 1 ON ON OFF OFF ON 10Q ON ON OFF OFF ON 1000 OFF ON OFF IK ON ON OFF ON OFF 10kQ ON ON OFF OFF ON 100kQ ON ON OFF ON OFF IMQ ON ON OFF ON OFF 10MQ OFF OFF OFF OFF ON 100MQ OFF OFF OFF OFF ON Range Q123 Q125 Q124 Q126 2 1Q ON ON OFF OFF S 100 ON ON OFF OFF e 1000 OFF OFF IKO ON ON OEE OEE 10kQ OFF OFF ON ON 100kQ OFF OFF ON ON d IMQ OFF OFF ON ON 10MQ OFF OFF ON ON 100MQ OFF OFF ON ON 4 20 Troubleshooting Model 2750 Multimeter Switch System Service Manual Table 4 11 4 dry circuit reference signal switching Range Q159 Q158 Q157 U133 0 7V U133 7V 0123 Q125 10 ON ON ON OFF ON ON ON 100 ON ON ON ON OFF ON ON 1000 ON ON ON OFF ON OFF OFF 1kQ ON ON ON ON OFF OFF OFF Range 0124 Q126 K104 U133 9 Q171 U208 9 U208 16 10 OFF OFF SET ON ON ON ON 100 OFF OFF SET ON ON ON ON 1000 ON ON SET ON ON ON ON 1kQ ON ON SET ON ON ON ON K104 set states Pin 8 switched to Pin 7 Pin 3 switched to Pin 4 Table 4 12 DCA signal switching Range K103 20mA Set 100mA Reset 1A Reset 3A Reset K103 set states Pin 8 to 7 Pin 3 to 4 K103 reset states Pin 8 to 9 Pin 3 to 2 Table 4 13 ACA signal switching U105 U105 U111 U105 U103 U103 Range K103 Pin 16 Pin1 Pin 16 Pin8 Pin16 Pint 1A Reset ON ON OFF OFF OFF OFF 3A R
143. n 5 and the parts lists in Section 6 for further information WARNING The information in this section is intended only for qualified service personnel Do not perform these procedures unless you are qualified to do so Some of these procedures may expose you to hazardous voltages that could cause personal injury or death Use caution when working with hazardous voltages The metal shield located on the motherboard is at analog LO potential and may have hazardous voltages To avoid a possible shock hazard connect the metal shield to chassis ground before servicing Repair considerations Before making any repairs to the Model 2750 be sure to read the following considerations CAUTION The PC boards are built using surface mount techniques and require specialized equipment and skills for repair If you are not equipped and or qualified it is strongly recommended that you send the unit back to the factory for repairs or limit repairs to the PC board replace ment level Without proper equipment and training you could damage a PC board beyond repair Repairs will require various degrees of disassembly However it is recommended that the Front Panel Tests be performed prior to any disassembly The disassembly instructions for the Model 2750 are contained in Section 5 of this manual Do not make repairs to surface mount PC boards unless equipped and qualified to do so see previous CAUTION When working inside the unit and replacing
144. n Road Dewai Madian Beijing 100029 8610 6202 2886 Fax 8610 6202 2892 FRANCE Keithley Instruments Sarl 3 all e des Garays 91127 Palaiseau C dex 01 64 53 20 20 Fax 01 60 11 77 26 GERMANY Keithley Instruments GmbH Landsberger Strasse 65 D 82110 Germering 089 84 93 07 40 Fax 089 84 93 07 34 GREAT BRITAIN Keithley Instruments Ltd The Minster 58 Portman Road Reading Berkshire RG30 0118 9 57 56 66 Fax 0118 9 59 64 69 INDIA Keithley Instruments GmbH Flat 2B WILLOCRISSA 14 Rest House Crescent Bangalore 560 001 91 80 509 1320 21 Fax 91 80 509 1322 ITALY Keithley Instruments s r l Viale San Gimignano 38 20146 Milano 02 48 39 16 01 Fax 02 48 30 22 74 KOREA Keithley Instruments Korea 2FL URI Building 2 14 Yangjae Dong Seocho Gu Seoul 137 130 82 2 574 7778 Fax 82 2 574 7838 NETHERLANDS Keithley Instruments B V Postbus 559 NL 4200 AN Gorinchem 0183 635333 Fax 0183 630821 SWITZERLAND Keithley Instruments SA Kriesbachstrasse 4 8600 D bendorf 01 821 94 44 Fax 01 820 30 81 TAIWAN Keithley Instruments Taiwan 1FL 85 Po Ai Street Hsinchu Taiwan R O C 886 3 572 9077 Fax 886 3 572 9031 Copyright 2001 Keithley Instruments Inc No 2193 Printed in the U S A 2 2000
145. n due date by sending the following commands CAL PROT DATE year month day CAL PROT NDUE year month day For example the following commands assume calibration dates of 3 5 2001 and 3 5 2002 respectively CAL PROT DATE 2001 3 5 CAL PROT NDUE 2002 3 5 Saving calibration constants After completing the calibration procedure send the following command to save the new calibration constants CAL PROT SAVE NOTE Calibration constants will not be saved unless the CAL PROT SAVE command is sent Locking out calibration After saving calibration send the following command to lock out calibration CAL PROT LOCK 2 20 Calibration Model 2750 Multimeter Switch System Service Manual Manufacturing calibration The manufacturing calibration procedure is normally performed only at the factory but the necessary steps are included here in case the unit is repaired and the unit requires these calibration procedures NOTE Ifthe unit has been repaired the entire comprehensive calibration procedure should also be performed in addition to the manufacturing calibration procedure Recommended test equipment Table 2 13 summarizes the test equipment required for the manufacturing calibration steps In addition you will need the calibrator Table 2 1 and signal generator to com plete the comprehensive calibration steps Table 2 13 Recommended equipment for manufacturing calibration Stanford Resea
146. n step STEP7 10V AC at 50kHz calibration step 5 8 100V AC at 1kHz calibration step STEPO 100V AC at 50kHz calibration step STEPIO 700V AC at 1kHz calibration step STEPI I 100mA AC at 1kHz calibration step STEPI2 1A AC at 1KHz calibration step STEPI3 2A AC at 1kHz calibration step E oO oO oO E e oO B 14 Calibration Reference Model 2750 Multimeter Switch System Service Manual 5 lt gt CALibration PROTected AC STEP lt n gt Purpose To program individual AC calibration steps Format cal prot ac step lt n gt Parameters 1 10mV AC at 1kHz calibration step 2 100mV AC at IkHZ calibration step 3 100mV AC at 50kHz calibration step 4 1V AC at 1KHz calibration step 5 1V AC at 50kHz calibration step 6 10V AC at 1kHz calibration step 7 10V AC at 50kHz calibration step 8 100V AC at 1kHz calibration step 100V AC at 50khz calibration step 10 700V AC at 1kHz calibration step 11 100mA at calibration step 12 1A AC at 1kHz calibration step 13 2A AC at kHz calibration step Description The AC STEP command programs the 13 individual AC calibration steps lt n gt represents the calibration step number The appropriate sig nal must be connected to the instrument when programming each step as summarized in the parameters listed above Example CAL PROT AC STEP7 Program 10V 50kHz step Model 2750 Multimeter Switch Sys
147. nd AMPS fuse Red Black Yellow Gray White Model 2750 Multimeter Switch System Service Manual Disassembly 5 7 Power module wire connections Use the information in Table 5 2 and DETAIL B of drawing 2750 050 to connect power module wires is Table 5 2 2 Power module wire colors z Location Wire Color 2 Top wire Gray Right top Violet Left top Red Right bottom White Left bottom Blue 5 8 Disassembly Model 2750 Multimeter Switch System Service Manual Replaceable Parts 6 2 Replaceable Parts Model 2750 Multimeter Switch System Service Manual Introduction This section contains replacement parts information and component layout drawings for the Model 2750 and the Model 7700 module For additional information about the Model 7700 module refer to the modules manual Parts lists Both electrical and mechanical parts for the Model 2750 are listed in several tables on the following pages For additional information on mechanical parts see the assembly draw ings provided at the end of Section 5 Ordering information To place an order or to obtain information concerning replacement parts contact your Keithley representative or the factory see inside front cover for addresses When order ing parts be sure to include the following information nstrument model number Model 2750 Instrument serial number Part description Component designation if applicable Keithley part num
148. odel 2750 Multimeter Switch System Service Manual This appendix contains detailed information about the various Model 2750 remote calibra tion commands Section 2 of this manual covers detailed calibration procedures For infor mation about additional commands to control other instrument functions refer to the Model 2750 User s Manual Command summary Table B 1 summarizes Model 2750 calibration commands Table B 1 Remote calibration command summary Command Description CALibration Calibration root command PROTected All commands in this subsystem are protected by the calibration lock except queries and CODE CODE up to 8 char string Calibration code or password default KI002750 COUNt Request the number of times the unit has been calibrated INITiate Initiate calibration LOCK Lock out calibration opposite of enabling cal with CODE command LOCK Request comprehensive cal lock state 0 locked 1 unlocked SAVE Save cal constants to EEROM DATE year month day Send cal date to 2750 DATE Request cal date from 2750 NDUE year month day Send next due cal date to 2750 NDUE Request next due cal date from 2750 DC DC cal steps STEPO Rear scanner terminals short step STEP 1 Front terminal short circuit STEP2 Open circuit STEP3 lt NRf gt 10V DC step 5 4 lt NRf gt 10V DC step 5 5 lt NRf gt 100V DC step STEP6 lt
149. ont panel short and open calibration DC volts calibration Resistance calibration DC current calibration AC volts calibration AC current calibration Programming calibration dates Saving calibration constants Locking out calibration NOTE As with front panel calibration you can choose to perform comprehensive DC only or AC only calibration Be sure to include a space character between each command and parameter Preparing the Model 2750 for calibration 1 Connect the Model 2750 to the IEEE 488 bus of the computer using a shielded IEEE 488 cable such as the Keithley Model 7007 or connect the unit to a com puter through the RS 232 port using a straight through 9 pin to 9 pin cable use a 9 25 pin adapter if necessary Turn on the Model 2750 and allow it to warm up for at least two hours before per forming calibration Make sure the primary address of the Model 2750 is the same as the address speci fied in the program that you will be using to send commands Use the GPIB key Unlock the calibration function by sending this command CAL PROT CODE K1002750 The above command shows the default code KI002750 Substitute the correct code if changed Send the following command to initiate calibration CAL PROT INIT Model 2750 Multimeter Switch System Service Manual Calibration 2 15 NOTE calibration can be partially performed if desired For example to calibrate only the 100Q range perform the DCU and 1
150. or making internal changes such as installing or removing jumpers Do not touch any object that could provide a current path to the common side of the circuit under test or power line earth ground Always make measurements with dry hands while standing on a dry insulated surface ca pable of withstanding the voltage being measured The instrument and accessories must be used in accordance with its specifications and operating instructions or the safety of the equipment may be impaired Do not exceed the maximum signal levels of the instruments and accessories as defined in the specifications and operating information and as shown on the instrument or test fixture panels or switching card When fuses are used in a product replace with same type and rating for continued protection against fire hazard Chassis connections must only be used as shield connections for measuring circuits NOT as safety earth ground connections If you are using a test fixture keep the lid closed while power is applied to the device under test Safe operation requires the use of a lid interlock Ifa screw is present connect it to safety earth ground using the wire recommended in the user documentation The A symbol on an instrument indicates that the user should refer to the operating instructions located in the manual The A symbol on an instrument shows that it can source or measure 1000 volts or more including the com bined effect of normal and co
151. osure count is also covered Setting the line voltage and replacing the line fuse WARNING Disconnect the line cord at the rear panel and remove all test leads connected to the instrument front and rear before replacing the line fuse The power line fuse is located in the power module next to the AC power receptacle Figure 3 1 If the line voltage must be changed or if the line fuse requires replacement perform the following steps 1 Place the tip of a flat blade screwdriver into the power module by the fuse holder assembly Figure 3 1 Gently push in and to the left Release pressure on the assembly and its internal spring will push it out of the power module CAUTION For continued protection against fire or instrument damage replace the fuse only with the type and rating listed If the instrument repeat edly blows fuses locate and correct the cause of the trouble before replacing the fuse 2 Remove the fuse and replace it with the type listed in Table 3 1 Model 2750 Multimeter Switch System Service Manual Routine Maintenance 3 3 Figure 3 1 Power module Model 2750 e A ere cum GE TRIG LINK 5232 EE HL ES e Line Voltage Selector Spring Fuse Holder Assembly CAU
152. output queue repeatedly test MAV again until it clears At this point the calibration step is completed 3 e oO oO E e oO B 26 Calibration Reference Model 2750 Multimeter Switch System Service Manual Using the OPC command The OPC operation complete command can also be used to detect the completion of each calibration step To use OPC to detect the end of each calibration step you must do the following 1 Enable operation complete by sending ESE 1 This command sets the OPC oper ation complete bit in the standard event enable register allowing operation com plete status from the standard event status register to set the ESB event summary bit in the status byte when operation complete is detected Send the OPC command immediately following each calibration command For example CAL PROT DC STEP1 OPC Note that you must include the semicolon to separate the two commands and that the OPC command must appear on the same line as the calibration command After sending a calibration command repeatedly test the ESB Event Summary bit bit 5 in the status byte until it is set Use either the STB query or serial poll ing to request the status byte Once operation complete has been detected clear OPC status using one of two methods 1 Use the ESR query then read the response to clear the standard event status register or 2 send the CLS command to clear the stat
153. ower up Batteries and fuses are OK Front panel operational All ranges or functions are bad Checked all cables Display or output check one C Drifts Unable to zero C Unstable Overload Will not read applied input Calibration only Certificate of calibration required Data required attach any additional sheets as necessary Show a block diagram of your measurement including all instruments connected whether power is turned on or not Also describe signal source Where is the measurement being performed factory controlled laboratory out of doors etc What power line voltage is used Ambient temperature F Relative humidity Other Any additional information If special modifications have been made by the user please describe Be sure to include your name and phone number on this service form Specifications are subject to change without notice All Keithley trademarks and trade names are the property of Keithley Instruments Inc All other trademarks and trade names are the property of their respective companies KEITHLEY Keithley Instruments Inc 28775 Aurora Road Cleveland Ohio 44139 440 248 0400 Fax 440 248 6168 1 888 KEITHLEY 534 8453 www keithley com BELGIUM Keithley Instruments B V Bergensesteenweg 709 B 1600 Sint Pieters Leeuw 02 363 00 40 Fax 02 363 00 64 CHINA Keithley Instruments China Yuan Chen Xin Building Room 705 12 Yumi
154. parts be sure to adhere to the handling precautions and cleaning procedures explained in Section 5 Many CMOS devices are installed in the Model 2750 These static sensitive devices require special handling as explained in Section 5 Whenever a circuit board is removed or a component is replaced the Model 2750 must be recalibrated See Section 2 for details on calibrating the unit Model 2750 Multimeter Switch System Service Manual Troubleshooting 4 3 Power on self test During the power on sequence the Model 2750 will perform a checksum test on its EPROM U156 and U157 and test its RAM U151 U152 U164 and U193 If one of these tests fails the instrument will lock up Front panel tests There are two front panel tests one to test the functionality of the front panel keys and one to test the display In the event of a test failure refer to Display board checks for details on troubleshooting the display board KEY test The KEY test allows you to check the functionality of each front panel key Perform the following steps to run the KEY test Press SHIFT and then TEST to access the self test options 2 Use the up or down RANGE key to display TEST KEY 3 Press ENTER to start the test When a key is pressed the label name for that key is displayed to indicate that it is functioning properly When the key is released the message NO KEY PRESS is displayed 4 Pressing EXIT tests the EXIT key However
155. ply The following information provides some basic circuit theory that can be used as an aid to troubleshoot the power supply A block diagram of the power supply is shown in Figure 4 1 Figure 4 1 Power supply block diagram CR104 5VD C156 C175 C281 U144 C273 C274 O D Common 37V CR116 CR117 C104 U101 D Common Line Power Voltage Power Switch Select Transformer O 18V Switch CR102 CR115 9O 15 7 C131 C148 O Common U119 U125 O 187V O 18V 5V A Common Model 2750 Multimeter Switch System Service Manual Troubleshooting 4 5 AC power is applied to the AC power module receptacle Power is routed through the line fuse and line voltage selection switch of the power module to the power transformer The power transformer has a total of four secondary windings for the various supplies AC voltage for the display filaments is taken from a power transformer secondary at F1 and F2 and then routed to the display board Each DC supply uses a rectifier and a capacitive filter and many supplies use an IC regula tor Table 4 1 summarizes rectifier filter and regulator circuits for the various DC supplies Table 4 1 Power supply components Supply Rectifier Filter Regulator 5VD CR104 C281 C156 C175 C273 C274 0144 37V CR116 CR117 C104 U101 15 7V CR102 CR115 C148 U125 15 7V CR102 CR115 C131 0119 5V 5VRL 5V2 CR103 C146 U124 18V CR102 C148 18V CR102 C
156. procedures unless you are qualified to do so All the procedures require accurate calibration equipment to supply precise DC and AC voltages DC and AC currents and resistance values Comprehensive calibration can be performed any time by an operator either from the front panel or by using the SCPI com mands sent either over the IEEE 488 bus or the RS 232 port DC only and AC only cali bration may be performed individually if desired Environmental conditions Conduct the calibration procedures in a location that has Anambient temperature of 18 to 28 C 65 to 82 F Arelative humidity of less than 8096 unless otherwise noted Warmup period Allow the Model 2750 Multimeter Switch System to warm up for at least two hours before performing calibration If the instrument has been subjected to temperature extremes those outside the ranges stated above allow extra time for the instrument s internal temperature to stabilize Typi cally allow one extra hour to stabilize a unit that is 10 C 18 F outside the specified tem perature range Allow the test equipment to warm up for the minimum time specified by the manufacturer Line power The Model 2750 requires a line voltage of 100V 120V 220V 240V 10 and a line fre quency of 45Hz to 66Hz or 360Hz to 440Hz Note that the line frequency is automatically sensed at power up but the line voltage must be manually set to either 100V 120V or 220V 240V as described in Section 3
157. puts DC STEP2 DATA OUT 10 V 0 HZ DC STEP3 10 DATA OUT 10 V DC STEP4 10 DATA OUT 100 V DC STEP5 100 DATA OUT 100 OHM DC STEP6 DATA OUT 10 KOHM DC STEP7 DATA OUT 100 KOHM DC STEP8 DATA OUT 1 MOHM DC STEP9 DATA OUT 10 MA DC STEP10 10E 3 DATA OUT 100 MA DC STEP11 100E 3 DATA OUT 1A DC STEP12 1 DATA OUT 10 MV 1 KHZ AC STEP1 DATA OUT 100 MV 1 KHZ AC STEP2 DATA OUT 100 MV 50 KHZ AC STEP3 5 S 5 a ga Ie S 3 C 6 Calibration Program Model 2750 Multimeter Switch System Service Manual DAT DAT DAT DAT DAT DAT DAT DAT DAT DAT O O O O O O O O O O UT UT EO EZ pos UT UT 1 V 1 KHZ AC STEP4 1 V 50 KHZ AC STEP5 10 V 1 KHZ AC STEP6 10 V 50 KHZ AC STEP7 100 V 1 KHZ AC STEP8 100 V 50 KHZ AC STEP9 700 V 1 KHZ AC STEP10 100 MA 1 KHZ AC STEP11 1 1 KHZ AC STEP12 2 1 KHZ AC STEP13 Index Symbols OPC command B 26 OPC query B 25 AC STEP lt n gt B 14 AC STEP lt 14l15 gt B 15 CODE B4 B 17 COUNt B 4 B 17 DATE B 7 DATE B 18 B 19 DC STEPO B 15 INIT B 5 B 18 LOCK 5 B 18 LOCK B 6 B 19 NDUE B 7 RCOunt B 19 SAVE B 6 B 20 STEPO B 20 STEPI B 8 STEP10 B 11 STEP11 B 12 STEP12 B 12 STEP2 B 9 STEP3 B 9 STEPA B 9 STEPS B 10 8 6 B 10
158. r components rra 5 5 Instrument reassembly rra 5 6 Input terminal wire connections ra 5 6 Power module wire connections ra 5 7 Replaceable Parts Introduction uon e e E 6 2 Parts sees 6 2 Ordering information rra 6 2 Factory au 6 2 Component layouts earra dae parkera 6 3 Specifications Calibration Reference Intr d ctoni B 2 Command SUMMALY Tarea B 2 Miscellaneous calibration commands B 4 DC calibration Gorrondona B 8 AC calibration commands rrura B 13 Manufacturing calibration commands rra B 15 Model 7700 calibration commands B 16 Remote error reporting rra B 21 Error s mimary uuu u e pe RYE Dee Re RE EE ERE EU d B 21 ERROTEN E areta atarietara irae B 24 Status byte Error Available bit B 25 Generating an SRQ on error rra B 25 Detecting calibration step completion B 25 Using the OPC query B 25 Using the OPC command sr B 26 Generating an SRQ on calibration complete B 26 Calibration Program Hiero festo rpm C 2 Computer hardware requirements rra C 2 Software requirements ra C 2 Calibration equipment rra C 2 General program instructions rra C 3 List of Illustrations 1 Figure 1 1 Figure 1 2 Figure 1 3 Figure 1 4 Figure 1 5
159. ration functions such as program ming the calibration code and date These commands are discussed in detail in the follow ing paragraphs CODE CALibration PROTected CODE Purpose To program the calibration code or password so that you can perform the calibration procedures Format cal prot code char string Parameters Up to an 8 character string including letters and numbers Description The CODE command enables the Model 2750 calibration procedures when performing these procedures over the bus In general this com mand must be sent to the unit before sending any other comprehensive or manufacturing calibration command The default calibration code is 1 002750 NOTE CODE command should be sent only once before performing either the comprehensive or factory calibration Do not send CODE before each calibra tion step To change the code first send the present code then send the new code The code parameter must be enclosed in single quotes Example CAL PROT CODE KI002750 Send default code of KI002750 CALibration PROTected COUNt Purpose To determine how many times the Model 2750 has been calibrated Format cal prot coun Response n Calibration count Description The COUNt command allows you to determine how many times the Model 2750 has been calibrated NOTE Usethe COUNt command to help you monitor for unauthorized calibration procedures Example CAL PROT CO
160. rch Systems DS345 Function Generator 1V RMS 3Hz 5ppm 1V RMS 1kHz 5ppm Keithley Model 2001 or 2002 Digital Multimeter 1V 3Hz AC 0 13 Keithley 7797 Calibration Extender Board Extender board preparation Before performing manufacturing calibration short the output HI LO SHI and SLO ter minals of the 7797 Calibration Extender together using clean solid copper wires These connections will form a low thermal short necessary for the manufacturing calibration procedure The Calibration Extender Board should then be installed in scanner Slot 1 Model 2750 Multimeter Switch System Service Manual Calibration 2 21 Unlocking manufacturing calibration To unlock manufacturing calibration press and hold in the OPEN key while turning on the power Measuring function generator signal amplitude The 3Hz function generator signal amplitude must be accurately measured using the digi tal multimeter listed in Table 2 13 Proceed as follows 1 Connectthe function generator output to the digital multimeter INPUT jacks See Figure 2 5 for typical connections 2 Turnon the function generator and multimeter and allow a two hour warm up period before measuring 3 Set the function generator to output a 1V RMS sine wave at 3Hz measure and record the signal amplitude Front panel manufacturing calibration 1 Install the shorted calibration extender board see Extender board preparation earlier in this section in sc
161. resistance with external sense on Select the Model 2750 4 wire resistance function by pressing Q4 key Close Channel 1 by pressing the CLOSE key then ENTER for SINGLE channel and keying in 101 Set the Model 2750 for the 1Q range and make sure the FILTER is on Enable OCOMP offset compensated ohms by pressing SHIFT then OCOMP Use OCOMP for 1Q 10Q and 100 range verification Recalculate reading limits based on actual calibrator resistance values Model 2750 Multimeter Switch System Service Manual Performance Verification 1 27 Figure 1 13 Connections for Model 7700 resistance verification to ranges CH1 Sense HI Model 7700 Ag Resistance Calibrator L L J L Sense LO CH11 Note Use shielded low thermal cables to minimize noise Enable or disable calibrator external sense as indicated in procedure 7 Source the nominal full scale resistance values for the 1Q 10MQ ranges summa rized in Table 1 14 and verify that the readings are within calculated limits 8 Connect the Model 7700 CH1 and CH1
162. rized in Table 2 4 For each step Set the calibrator to the indicated value and place the unit in operate If the calibrator cannot output the exact resistance value use the Model 2750 left and right arrow keys and the range keys to adjust the Model 2750 display to agree with the actual calibrator resistance Press the ENTER key to calibrate each point Wait for the Model 2750 to complete each step before continuing Table 2 4 Ohms calibration summary Calibration Step 1000 10kQ 100kQ IMQ Calibrator Resistance 1000 10kQ 100kQ IMQ Allowable Range 900 to 1100 9kQ to 90kQ to 110kQ 0 9MQ to 1 1MQ Nominal resistance Adjust Model 2750 calibration parameter to agree with actual value Model 2750 Multimeter Switch System Service Manual Calibration 2 11 DC current calibration After the 1MQ resistance point has been calibrated the unit will prompt you to apply 10mA Follow these steps for DC current calibration 1 Connect the calibrator to the AMPS and INPUT LO terminals of the Model 2750 as shown in Figure 2 3 Figure 2 3 Connections for DC and AC amps calibration DC and AC Current Calibrator Model 2750 Front Panel f N Output Input LO HI E A gt e N N gt Note Be sure calibrator is set for normal current outpu
163. s finished with short circuit calibration it will display the following prompt OPEN CIRCUIT 4 Remove the calibration short and press ENTER During this phase the CALI BRATING message will be displayed NOTE Be sure to minimize movement near front input terminals Excessive movements can cause capacitive coupling errors which could affect calibration accuracy DC volts calibration After the front panel short and open procedure the unit will prompt you for the first DC voltage 10V Do the following 1 Connect the calibrator to the Model 2750 as shown in Figure 2 2 Wait three min utes to allow for thermal equilibrium before proceeding Figure 2 2 Connections for DC volts and ohms calibration Sense HI DC Voltage and Resistance Calibrator Model 2750 Front Panel LO Note Use shielded low thermal cables to minimize noise Enable or disable calibrator external sense as indicated in procedure Model 2750 Multimeter Switch System Service Manual Calibration 2 9 NOTE Although 4 wire connections are shown the sense leads are connected and dis connected at various points in this procedure by turning calibrator external sense on or off as appropriate If your calibrator does not have provisions for turning external sense on and off disconnect the sense leads when external sens ing is to be turned off and connect the sense leads when externa
164. se dates as follows 1 Atthe CAL DATE prompt use the left and right arrow keys and the range keys to set the calibration date then press ENTER 2 Theunit will then prompt you to enter the next calibration due date with this prompt CAL NDUE Use the left and right arrow keys and the range keys to set the calibration due date then press ENTER 3 The unit will prompt you to save new calibration constants with this message SAVE CAL YES To save the new constants press ENTER If you do not want to save the new constants press the down range key to toggle to NO then press ENTER NOTE Calibration constants calculated during the present calibration procedure will not be saved unless you choose the YES option Previous calibration constants will be retained if you select NO 2 14 Calibration Model 2750 Multimeter Switch System Service Manual Remote calibration Follow the steps in this section to perform comprehensive procedures via remote See Appendix B for a detailed list and description of remote calibration commands When sending calibration commands be sure that the Model 2750 completes each step before sending the next command You can do so either by observing the front panel CAL IBRATING message or by detecting the completion of each step over the bus See Appendix B Detecting calibration step completion The procedures for calibrating the Model 2750 via remote include Preparing the Model 2750 for calibration Fr
165. select your choice by pressing ENTER Table 2 2 Comprehensive calibration procedures Procedure Menu Choice Procedures Full calibration ALL All comprehensive calibration steps DC and AC DCV DCI and ohms DC DC voltage DC current and resistance calibration ACV and ACI AC AC voltage and AC current calibration Front panel short and open calibration At the Model 2750 prompt for a front panel short do the following 1 Connect the Model 8610 low thermal short to the instrument front panel INPUT and SENSE terminals as shown in Figure 2 1 Make sure the INPUTS button is not pressed in so that the front inputs are selected Wait at least three minutes before proceeding to allow for thermal equilibrium Figure 2 1 Low thermal short connections Model 2750 i93 SLOT 1 SLOT2 SLOT3 SLOT 4 EET KEITHLEY O MODEL 2750 MULTIMETERISWITGH SYSTEM e 00000088 A NAA Ses dra dede P eum e em EA G ws Gm 2771 NOTE sure to connect the low thermal short properly to the LO and SENSE ter minals Keep drafts away from low thermal connections to avoid thermal drift which could affect calibration accuracy 2 Press ENTER to start short circuit calibration While the unit is calibrating it will display CALIBRATING gt 2 N N g gt 2 8 Calibration Model 2750 Multimeter Switch System Service Manual 3 When the unit i
166. steps in the following paragraphs in the order shown for comprehensive DC only and AC only calibration procedures The procedures for front panel calibration include Preparing the Model 2750 for calibration Front panel short and open calibration DC voltage calibration Resistance calibration DC current calibration AC voltage calibration AC current calibration Setting calibration dates Preparing the Model 2750 for calibration 1 Turn on the Model 2750 and allow it to warm up for at least two hours before per forming a calibration procedure Start the calibration process as follows a Access the calibration menu by pressing SHIFT then TEST then display TEST CALIB using the up or down range key Press ENTER b Use the up or down range key to scroll through the available calibration menu items until the unit displays RUN then press ENTER c Atthe prompt enter the calibration code The default code is 002750 Use the left and right arrow keys to move among the digits use the up range key to increment numbers and press the down range key to specify alphabetic letters Confirm the code by pressing ENTER d Choose N at the prompt to proceed without changing the code then press ENTER Model 2750 Multimeter Switch System Service Manual Calibration 2 7 3 Choose which of the calibration tests summarized in Table 2 2 you want to run at the CAL RUN prompt Use the up and down range keys to scroll through the options
167. t 2 Calibrate each current step summarized in Table 2 5 For each step Set the calibrator to the indicated DC current and make sure the unit is in OPERATE Make sure the Model 2750 display indicates the correct calibration current Press ENTER to complete each step Allow the Model 2750 to finish each step NOTE Ifyou performing DC only calibration proceed to Setting calibration dates and saving calibration Table 2 5 DC current calibration summary Calibration Step Calibrator Current Allowable Range 10mA 10 00000mA 9mA to 11mA 100mA 100 0000mA 90mA to 110mA 1A 1 000000A 0 9A to 1 1A 2 12 Calibration Model 2750 Multimeter Switch System Service Manual AC voltage calibration Follow these steps for AC voltage calibration 1 Connect the calibrator to the Model 2750 INPUT HI and LO terminals as shown in Figure 2 4 Figure 2 4 Connections for AC volts calibration AC Voltage Calibrator Model 2750 Front Panel SENSE pen Input Output LO L 2 Perform the calibration steps summarized in Table 2 6 For each step Set the calibrator to the indicated value and make sure the calibrator is in OPERATE Press ENTER to complete each step Wait until the Model 2750 completes each step Table 2 6 AC voltage calibration summary Calibration Step Calibrator Voltage Frequency 10mV AC at 1kHz 100mV
168. tage to 50mV if the SENSE terminals are not connected to the DUT When either clamp acts to limit the voltage across the DUT the current source goes into compliance effectively turning the current source into a voltage source thus limiting the DUT voltage to 20mV or 50mV as the case be Note that a 0 8uF capacitor and 100kQ resistor are connected across the DUT during dry circuit ohms measurements for stabilization E oO E ge 4 12 Troubleshooting Model 2750 Multimeter Switch System Service Manual Figure 4 4 Simplified schematic of dry circuit ohms 20mV Reference Main Clamp Monitors SENSE HI Source 10uA OYY N 100HA gt 1mA 10mA 50mV Reference Secondary Clamp Monitors INPUT HI gt ON ON O O 1MQ INPUT Q DUT Converter Gain GEO LO SENSE ii 100kQ LO SSP Solid State Protection Circuit Model 2750 Multimeter Switch System Service Manual Troubleshooting 4 13 Troubleshooting Troubleshooting information for the various circuits is summarized below See Principles of operation for circuit theory Display board checks If the front panel DISP test indicates that there is a problem on the display board use Table 4 2 Table 4 2 Display board checks Step Item Component Required Condition Remarks 1 Front panel DISP test Verify that all segments operate Use front panel display test 2
169. tem Service Manual Calibration Reference 15 Manufacturing calibration commands NOTE To perform these steps manufacturing calibration must be enabled by pressing and holding the OPEN key while turning on the power See Section 2 Three calibration steps are only performed at the factory or when the unit has been repaired CALibration PROTected AC STEP14 1V AC at 3Hz CALibration PROTected AC STEP15 1V AC at 1kHz CALibration PROTected DC STEPO Rear scanner terminal short circuit AC STEP lt 141 15 gt CALibration PROTected AC STEP lt 14115 gt Purpose To program individual AC manufacturing calibration steps Format cal prot ac stepl4 Cal voltage cal prot ac stepl15 Cal frequency Parameters Cal voltage 1 1V nominal Cal frequency 1E3 1kHz nominal Description The AC STEP14 and AC STEP 15 commands program the two manufacturing AC calibration steps The appropriate signal must be connected to the instrument when programming each step as summa rized by the parameters listed above Example CAL PROT AC STEP14 1 Program AC step 14 CAL PROT AC STEP15 1 3 Program AC step 15 DC STEPO CALibration PROTected DC STEPO Purpose To perform rear scanner terminal short circuit calibration Format cal prot dc stepO Parameters None Description STEPO performs the rear scanner terminal short circuit calibration step in the manufacturing calibration procedure Install an extender card
170. the front panel terminals simultaneously with plug in modules all cable insulation voltage ratings must equal or exceed the maximum voltage applied to either the front panel terminals or the plug in module terminals 2 4 Calibration Model 2750 Multimeter Switch System Service Manual Calibration code Before performing comprehensive calibration you must first unlock calibration by enter ing the appropriate calibration code Front panel calibration code For front panel calibration follow these steps 1 Access the calibration menu by pressing SHIFT then TEST then use the up or down range key to display TEST CALIB Press ENTER and note that the instru ment displays the following CAL DATES Use the up or down range key to scroll through the available calibration items until the unit displays RUN then press ENTER The Model 2750 then prompts you to enter a code CODE 000000 The factory default code is 002750 Use the left and right arrow keys to move among the digits use the up range key to increment numbers and press the down range key to specify alphabetic letters Confirm the code by pressing ENTER The Model 2750 allows you to define a new calibration code Use the up and down range keys to toggle between yes and no Choose N if you do not want to change the code Choose Y if you want to change the code The unit then prompts you to enter a new code Enter the code and press ENTER Remote calibration code If
171. the instrument Prod ucts that consist of a circuit board with no case or chassis e g data acquisition board for installation into a computer should never require cleaning if handled according to instructions If the board becomes contami nated and operation is affected the board should be returned to the factory for proper cleaning servicing Rev 2 01 Table of Contents 1 Performance Verification UAU aA 1 2 Verification test requirements raa 1 3 Environmental conditions ra 1 3 Warmup period rr 1 3 1 3 Recommended test equipment 2 1 4 Verification limits uiii eere tp Et re ree tris 1 5 Example reading limit calculation rr 1 5 Calculating resistance reading limits ra 1 5 Restoring factory defaults 1 6 Performing the verification test procedures 1 6 Verification test summary rra 1 6 Test considerations rra 1 7 Model 2750 verification ra 1 8 Verifying DC voltage rr 1 8 Verifying AC voltage rru 1 10 Verifying DO current ungere tenens 1 11 Verifying AC current rru 1 13 Verifying normal resistance aa 1 14 Verifying dry circuit resistance ru 1 16 Verifying temperature rru 1 18 Verifying frequency 1 20 Model 7700 verification sr 1 20 Verifying DC voltage rru 1 21 Verifying AC voltage rra 1 22 Verifying DC current rru 1 24 Verifying
172. the second consecutive press of EXIT aborts the test and returns the instrument to normal operation DISP test The display test allows you to verify that each segment and annunciator in the vacuum flu orescent display is working properly Perform the following steps to run the display test 1 Press SHIFT and then TEST to access the self test options 2 Use the up or down RANGE key to display TEST DISP 3 Press ENTER to start the test There are five parts to the display test Each time ENTER is pressed the next part of the test sequence is selected The five parts of the test sequence are as follows a All annunciators are displayed b The segments of each digit are sequentially displayed c The 12 digits and annunciators are sequentially displayed d The annunciators located at either end of the display are sequentially displayed e The LEDs are displayed 4 When finished abort the display test by pressing EXIT The instrument returns to normal operation E oO E ge 4 4 Troubleshooting Model 2750 Multimeter Switch System Service Manual Principles of operation The following information is provided to support the troubleshooting tests and procedures covered in this section of the manual Refer to the following block diagrams Figure 4 1 Power supply block diagram Figure 4 2 Digital circuitry block diagram Figure 4 3 Analog circuitry block diagram Power sup
173. then dis plays the thermocouple type TYPE K Select a type J temperature sensor then press ENTER The unit then displays the reference junction type JUNC SIM Make certain that the simulated reference junction type is selected then press ENTER The unit then displays the current simulated reference junction tem perature SIM 023 Using the cursor and range keys set the reference junction temperature to 0 C then press ENTER twice to complete the temperature configuration process 3 Select the temperature function by pressing the TEMP key 4 Source each of the voltages summarized in Table 1 8 and verify that the tempera ture readings are within limits Be sure to select the appropriate thermocouple type for each group of readings See step 2 above Model 2750 Multimeter Switch System Service Manual Performance Verification 1 19 Table 1 8 Thermocouple temperature verification reading limits N Applied DC a Thermocouple Type Voltage Reading Limits 1 year 18 C to 28 C lt J 7 659mV 190 2 to 189 9 C 3 0 2 to 0 2 C o 42 280mV 749 8 to 750 2 C 5 K 5 730mV 190 2 to 189 8 C 0 2 to 0 2 C 54 138mV 1349 8 to 1350 2 C Voltages shown are based on ITS 90 standard using 0 C reference junction temperature See text for proce dure to set reference junction temperature RTD temperature 1 Connect the precision decade resistance box listed in Table 1 1 to the Model
174. tion 2 19 preparing the Model 2700 2 14 Programming calibration dates 2 19 resistance 2 16 Saving calibration constants 2 19 short and open 2 15 Remote error reporting B 21 Repair considerations 4 2 Replaceable Parts 6 1 Resetting relay closure count 3 9 resistance A 14 A 15 verifying Model 2700 1 14 1 16 1 28 verifying Model 7700 1 26 RS 232 interface 4 8 Scanner card signals 4 11 Signal switching 4 10 Solder repairs 5 2 Specifications A 1 Static sensitive devices 5 3 Status byte EAV Error Available bit B 25 Switching device locations 4 23 Temperature A 14 A 15 temperature RTD Model 2700 1 19 RTD Model 7700 1 33 thermocouple Model 2700 1 18 thermocouple Model 7700 1 31 verifying Model 2700 1 18 verifying Model 7700 1 31 Trigger circuits 4 8 Troubleshooting 4 1 verification Model 2700 1 8 Model 7700 1 20 Verification limits 1 5 Verification test considerations 1 7 Model 2700 1 6 Model 7700 1 7 summary 1 6 verification test procedures 1 6 Verification test requirements 1 3 verifying AC current Model 7700 1 25 Warm up period calibration 2 2 Verification Procedures 1 3 Service Form Model No Serial No Date Name and Telephone No 2 Company List all control settings describe problem and check boxes that apply to problem Q Intermittent C Analog output follows display C Particular range or function bad specify IEEE failure Obvious problem on p
175. trument repeatedly blows fuses locate and correct the cause of the trouble before replacing the fuse 3 Remove the fuse and replace it with the same type 3A 250V fast blow Keithley part number FU 99 1 4 Install the new fuse by reversing the above procedure Figure 3 2 AMPS fuse Model 2750 EN INPUT A e KEITHLEY Oo PORUM qp M Rs ae MODEL 2750 MULTIMETER SWITCH SYSTEM 2 INTEGRA SERIES GS Ee EY GD o POWER SAVE EIE CONF Ga 19 CICE Ge Su Gal EO Ga ir m Rotate Counterclockwise Model 2750 Multimeter Switch System Service Manual Routine Maintenance 3 5 Replacing Model 7700 plug in module amps fuses WARNING The information in this section is intended only for qualified service personnel Do not perform these procedures unless you are qualified to do so WARNING Make sure that all plug in module connections are de energized and disconnected before replacing module amps fuses Turn off the power and disconnect the power line and external connections from the Model 7700 2 Open the Model 7700 top cover Locate the amps fuses for CH21 and CH22 Figure 3 3 3 4 Remove the circuit board from the bottom plastic housing by removing the two bottom screws Figure 3 3 Model 7700 amps fuses Model 7700 INPUT SENSE CH1 CH2 CH3 CH4 CH5 CH6 L H L H L H L H L H L H L HLH M HLHLHLHL 0 Setia u j COORG
176. tthe calibrator output to 0 00000mV DC and allow the reading to settle 5 Enable the Model 2750 REL mode Leave REL enabled for the remainder of the DC volts verification test 6 Source positive and negative and full scale voltages for each of the ranges listed in Table 1 10 For each voltage setting be sure that the reading is within stated limits 7 Press the OPEN key to open Channel 1 J e e I EA e E 1 22 Performance Verification Model 2750 Multimeter Switch System Service Manual Table 1 10 Plug in module DCV reading limits Range Applied DC Voltage Reading Limits 1 year 18 to 28 C 100mV 100 0000mV 99 9935 to 100 0065mV IV 1 000000V 0 999963 to 1 000037V 10V 10 00000V 9 99965 to 10 00035V 100V 100 0000V 99 9946 to 100 0054V 1000V 300 000V 299 976 to 300 024V Source positive and negative values for each range Verifying AC voltage Check AC voltage accuracy by applying accurate AC voltages at specific frequencies from the AC voltage calibrator to the Model 7700 inputs and verifying that the displayed read ings fall within specified ranges CAUTION Do not exceed 300V RMS between the 7700 plug in module INPUT H and L terminals or between adjacent channels or 8 x 10 VHz input because instrument damage may occur Follow these steps to verify AC voltage accuracy 1 Connect the Model 7700 CH1 H and L INPUT terminals to the AC voltage calibra tor as shown in Fig
177. ultiplexing and gain rru 4 21 ACV and ACA signal multiplexing and gain 4 21 DCA signal multiplexing and gain rru 4 21 Q2 signal multiplexing and gain rru 4 22 Q4 signal multiplexing and gain rru 4 22 Q4 dry circuit signal multiplexing and gain 4 22 Switching device locations rr 4 23 Disassembly Input terminal wire colors rra 5 6 Power module wire colors rra 5 7 Replaceable Parts Model 2750 motherboard parts list 6 3 Model 2750 display board parts list 6 12 Model 2750 backplane board parts list 6 13 Model 2750 miscellaneous parts list 6 14 Model 7700 module parts list rr 6 15 Calibration Reference Remote calibration command summary B 2 DC calibration 2 B 8 AC calibration commands B 13 Model 7700 calibration commands B 16 laiatu Bara aA B 21 Performance Verification 1 2 Performance Verification Model 2750 Multimeter Switch System Service Manual Introduction Use the procedures in this section to verify that Model 2750 Multimeter Switch System accuracy is within the limits stated in the instrument s one year accuracy specifications You can perform these verification procedures Make sure that t
178. uracy Model 2750 Multimeter Switch System Service Manual Performance Verification 1 5 Verification limits The verification limits stated in this section have been calculated using only the Model 2750 one year accuracy specifications and they do not include test equipment uncertainty If a particular measurement falls slightly outside the allowable range recalculate new lim its based on both Model 2750 specifications and pertinent calibration equipment specifications Example reading limit calculation The following is an example of how reading limits have been calculated Assume you are testing the 10V DC range using a 10V input value Using the Model 2750 one year accu racy specification for 10V DC of 30ppm of reading 5ppm of range the calculated limits are Reading limits 10V 10V x 30ppm 10V x 5ppm Reading limits 10V 0 0003 0 00005 Reading limits 10V 0 00035V Reading limits 2 9 99965V to 10 00035V Calculating resistance reading limits Resistance reading limits must be recalculated based on the actual calibration resistance values supplied by the equipment manufacturer Calculations are performed in the same manner as shown in the preceding example except of course that you should use the actual calibration resistance values instead of the nominal values when performing your calculations For example assume that you are testing the 10kQ range using an actual 10 03kO calibra tion resistance va
179. ure 1 10 Figure 1 10 Connections for Model 7700 AC volts verification Amplifier Connect to calibrator TSEZ 5 o DI Shielded Model 7700 Cable Output Calibrator Output AC Voltage LO Model 2750 Multimeter Switch System Service Manual Performance Verification 1 23 2 Install the Model 7700 in Slot 1 of the Model 2750 then turn on the power and allow the unit to warm up for two hours before proceeding Be sure the front panel INPUTS switch is set to the REAR position 3 Selectthe AC volts function by pressing the ACV key Close Channel 1 by pressing the CLOSE key then ENTER for SINGLE channel and then keying in 101 4 Setthe Model 2750 for the 100mV range make sure that REL is disabled 5 Source 1kHz and 50kHz AC voltages for each of the ranges summarized in Table 1 11 and make sure that the respective Model 2750 readings fall within stated limits 6 Press the OPEN key to open Channel 1 J e e I t EA e E Table
180. us registers Note that sending CLS will also clear the error queue and operation complete status Generating an SRQ on calibration complete An IEEE 488 bus SRQ service request can be used to detect operation complete instead of repeatedly polling the Model 2750 To use this method send both ESE 1 and SRE 32 to the instrument then include the OPC command at the end of each calibration com mand line as covered above Refer to your controller s documentation for information on detecting and servicing SRQs Calibration Program C 2 Calibration Program Model 2750 Multimeter Switch System Service Manual Introduction This appendix includes a calibration program written in BASIC to help you calibrate the Model 2750 Refer to Section 2 for more details on calibration procedures equipment and connections Computer hardware requirements The following computer hardware is required to run the calibration program IBM PC AT or compatible computer Keithley KPC 488 2 KPS 488 2 or KPC 488 2AT or CEC PC 488 IEEE 488 interface for the computer Two shielded IEEE 488 connecting cables Keithley Model 7007 Software requirements In order to use the calibration program you will need the following software Microsoft QBasic supplied with MS DOS 5 0 or later MS DOS version 5 0 or later HP style Universal Language Driver CECHP EXE supplied with Keithley and CEC interface cards listed above Cali
181. w dry the board with dry nitrogen gas After cleaning allow the board to dry in a 50 C low humidity environment for several hours Model 2750 Multimeter Switch System Service Manual Disassembly 5 3 Static sensitive devices CMOS devices operate at very high impedance levels Therefore any static that builds up on you or your clothing may be sufficient to destroy these devices if they are not handled properly Use the following precautions to avoid damaging them CAUTION Many CMOS devices are installed in the Model 2750 Handle all semi conductor devices as being static sensitive Transport and handle ICs only in containers specially designed to prevent static build up Typically you will receive these parts in anti static containers made of plastic or foam Keep these devices in their original containers until ready for installation Remove the devices from their protective containers only at a properly grounded work station Also ground yourself with a suitable wrist strap Handle the devices only by the body do not touch the pins Ground any printed circuit board into which a semiconductor device is to be inserted to the bench or table Use only anti static type desoldering tools Use only grounded tip soldering irons Once the device is installed in the PC board it is normally adequately protected and you can handle the boards normally Assembly drawings Use the following assembly drawings to assist you as you dis
182. wire Q when calibrating all resistance ranges Be sure that the calibrator external sense mode is turned on 2 Perform the calibration steps summarized in Table 2 9 For each step Set the calibrator to the indicated resistance and make sure the unit is in oper ate Use the recommended resistance or the closest available value Send the indicated programming command Change the command parameter if you are using a different calibration resistance than that shown Wait until the Model 2750 completes each step before continuing Table 2 9 Resistance calibration programming steps Calibration Calibrator Step Resistance Calibration Command Parameter Range 1000 1000 CAL PROT DC STEP6 100 90 to 110 10kQ 10k CAL PROT DC STEP7 10E3 9E3 to 11E3 100kQ 100kQ CAL PROT DC STEP8 100E3 90E3 to 110E3 IMQ IMQ CAL PROT DC STEP9 1E6 900E3 to 1 1E6 Use exact calibrator resistance value for parameter Model 2750 Multimeter Switch System Service Manual Calibration 2 17 DC current calibration After the 1MQ resistance point has been calibrated follow these steps for DC current calibration 1 Connect the calibrator to the AMPS and INPUT LO terminals of the Model 2750 as shown in Figure 2 3 2 Perform the calibration steps listed in Table 2 10 For each step Set the calibrator to the indicated current and make sure the unit is in operate Use the recommended current if possible Send the indicated programmin
183. with low thermal shorts on the output terminals installed in Slot 1 and select the rear scanner inputs before sending this command oO oO e oO Example CAL PROT DC STEPO Perform rear short circuit calibration B 16 Calibration Reference Model 2750 Multimeter Switch System Service Manual Model 7700 calibration commands Table B 4 summarizes calibration commands for the Model 7700 plug in module Note that CARD1 commands calibrate the card in Slot 1 while CARD commands request cali bration count date and reference temperature information from a card in Slot 1 through Slot 5 NOTE A Model 7700 must be installed in Slot 1 through a Model 7797 calibration extender card to be calibrated See Section 2 Model 7700 calibration Table B 4 Model 7700 calibration commands Command Description CALibration Calibration root command PROTected All commands in this subsystem are protected by the calibration lock except queries and CODE CODE up to 8 char string gt Send calibration code Default KI002750 CARDI Path to calibrate card in slot 1 NITiate Initiate card calibration RCOunt Reset card calibration count to 0 DATE Request card cal date SSAVE Save cal constants to card EEPROM LOCK Lock out calibration LOCK Request cal lock state 0 locked 1 unlocked STEPO lt NRf gt Temperature sensor cold calibration lt NRf gt temperature
184. xcept that AC specifications are given as follows Accuracy of reading of range As an example of how to calculate the actual reading limits assume that you are measur ing 120V 60Hz on the 750V range You can compute the reading limit range from ACV one year accuracy specifications as follows Accuracy 0 06 of reading 0 03 of range 0 0006 x 120V 0 0003 x 750V 0 072V 0 225V 0 297V In this case the actual reading range is 120V 0 297V or from 119 703V to 120 297V AC current calculations are performed in exactly the same manner using the pertinent specifications ranges and input signal values A 10 Specifications Model 2750 M ultimeter Switch System Service M anual Calculating dBm characteristics accuracy As an example of how to calculate the actual reading limits for a 13dBm measurement with a reference impedance of 50Q assume an applied signal 0 998815V The relationship between voltage and dBm is as follows 2 Vin dBm 10log oy From the previous example on calculating DC characteristics accuracy it can be shown that a measurement of 0 998815V on the 1V range has an uncertainty of 36 9644mV 0 998778V to 0 998852V using one year specifications Expressing 0 998778V as dBm 0 998778 2 500 dBm 10log inw 12 99968dBm and expressing 0 998852V as dBm 0 998852 V 500 dB ENA 13 00032dBm Thus the actual reading range is 1
185. y off Limits off Trigger delay 0 Includes measurement and binary data transfer out GPIB Reading Element only 8 0 0196 of step settling error Trigger delay 400ms 9 Auto Zero off 10 Sample count 1024 11 DETector BANDwidth 300 with nPLC 0 01 12 Maximum useful limit with trigger delay 175ms 13 For Auto Delay On 1 8 s 14 For signal levels gt 2 2 add additional 0 4 to of reading uncertainty GENERAL SPECIFICATIONS EXPANSION SLOTS 5 POWER SUPPLY 100V 120V 220V 240V 10 LINE FREQUENCY 45Hz to 66Hz and 360Hz to 440Hz automatically sensed at power up POWER CONSUMPTION 80VA OPERATING ENVIRONMENT Specified for 0 C to 50 C Specified to 80 RH at 35 C STORAGE ENVIRONMENT 40 C to 70 C BATTERY Lithium battery backed memory 3 years 9 23 WARRANTY 3 years EMC Conforms to European Union Directive 89 336 EEC EN61326 1 SAFETY Conforms to European Union Directive 73 23 EEC EN 61010 1 CAT 1 VIBRATION MIL PRF 28800F Class 3 Random WARM UP 2 hours to rated accuracy DIMENSIONS Rack Mounting 89mm high x 485mm wide x 370mm deep 3 5 in x 19in x 14 563 in Bench Configuration with handle and feet 104mm high x 485mm wide x 370mm deep 4 125 in x 19 in x 14 563 in SHIPPING WEIGHT 13kg 28 Ibs DIGITAL 1 0 2 inputs 1for triggering and 1for hardware interlock 5 outputs 4 for Reading Limits and 1 for Master Limit Outputs are TTL com patible or can sink 250mA diode clamped to 4
186. you are performing calibration over the IEEE 488 bus or the RS 232 port send this command to unlock calibration CAL PROT CODE lt 8 character string The default code command is CAL PROT CODE K1002750 To change the code via remote simply send the CAL PROT CODE command twice first with the present code then with the new code Model 2750 Multimeter Switch System Service Manual Calibration 2 5 Comprehensive calibration The comprehensive calibration procedure calibrates the DCV DCI ACV ACI and ohms functions You can also choose to calibrate only the DCV DCI and resistance or ACV ACI functions These procedures are usually the only calibration required in the field Manufacturing cal ibration is normally done only at the factory but it should also be done in the field if the unit has been repaired See Manufacturing calibration at the end of this section for more information Calibration cycle Perform comprehensive calibration at least once a year or every 90 days to ensure the unit meets the corresponding specifications Recommended equipment Table 2 1 lists the recommended equipment you need for comprehensive DC only and AC only calibration procedures You can use alternate equipment such as a DC transfer standard and characterized resistors as long as the equipment has specifications at least as good as those listed in the table In general equipment uncertainty should be at least four times better t

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