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A l l t e s t I n s t r u me n t s , I n c .
5 0 0 C e n t r a l A v e .
F a r mi n g d a l e , N J 0 7 7 2 7
P : ( 7 3 2 ) 9 1 9 - 3 3 3 9
F : ( 7 3 2 ) 9 1 9 - 3 3 3 2
a l l t e s t . n e t
s s a l e s @ a l l t e s t . n e t
T h e t e s t & me a s u r e me n t
e q u i p me n t y o u n e e d a t
t h e p r i c e y o u w a n t .
A l l t e s t c a r r i e s t h e w o r l d ' s l a r g e s t s e l e c t i o n o f
u s e d / r e f u r b i s h e d b e n c h t o p t e s t & me a s u r e me n t
e q u i p me n t a t 5 0 % t h e p r i c e o f n e w .
O O u r e q u i p me n t i s g u a r a n t e e d w o r k i n g , w a r r a n t i e d , a n d
a v a i l a b l e w i t h c e r t i f i e d c a l i b r a t i o n f r o m o u r i n - h o u s e s t a f f
o f t e c h n i c i a n s a n d e n g i n e e r s .
• 1 0 + f u l l t i me t e c h n i c i a n s w i t h o v e r 1 5 0 y e a r s o f
s p e c i a l i z a t i o n
• 9 0 d a y w a r r a n t y & 5 d a y r i g h t o f r e t u r n o n a l l
e q u i p me n t
• • 1 - 3 y e a r w a r r a n t i e s f o r n e w a n d
p r e mi u m- r e f u r b i s h e d e q u i p me n t
• E v e r y u n i t t e s t e d t o O E M s p e c i f i c a t i o n s
• S a t i s f a c t i o n g u a r a n t e e d
Y o u h a v e p l a n s , w e w i l l h e l p y o u a c h i e v e t h e m.
A n y p r o j e c t . A n y b u d g e t .
t
G e t a q u o t e t o d a y !
C C a l l ( 7 3 2 ) 9 1 9 - 3 3 3 9 o r e ma i l s a l e s @a l l t e s t . n e t .

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Summary of Contents for Keithley SourceMeter 3A 2420

  • Page 1 T h e t e s t & me a s u r e me n t e q u i p me n t y o u n e e d a t t h e p r i c e y o u w a n t . A l l t e s t I n s t r u me n t s , I n c .
  • Page 2 Model 2420 3A SourceMeter ® Service Manual A G R E A T E R M E A S U R E O F C O N F I D E N C E...
  • Page 3 WARRANTY Keithley Instruments, Inc. warrants this product to be free from defects in material and workmanship for a period of 1 year 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.
  • Page 4 ® Model 2420 3A SourceMeter Service Manual ©1997, Keithley Instruments, Inc. All rights reserved. Cleveland, Ohio, U.S.A. Fifth Printing, October 2001 Document Number: 2420-902-01 Rev. E...
  • Page 5 Revision D (Document Number 2420-902-01) ..............June 2000 Revision E (Document Number 2420-902-01) ............October 2001 All Keithley product names are trademarks or registered trademarks of Keithley Instruments, Inc. Other brand names are trademarks or registered trademarks of their respective holders.
  • Page 6 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 tran- sient over-voltages.
  • Page 7 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 ap- provals, 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.
  • Page 8: Table Of Contents

    Table of Contents Performance Verification Introduction ..................1-2 Verification test requirements ..............1-2 Environmental conditions.............1-2 Warm-up period ................1-2 Line power ..................1-3 Recommended test equipment ............1-3 1Ω resistor characterization ............1-3 Verification limits ................1-4 Example limits calculation............1-4 Resistance limits calculation............1-4 Restoring factory defaults ..............1-5 Performing the verification procedures ..........1-5 Test summary................1-5 Test considerations ...............1-6...
  • Page 9 Changing the password ............... 2-6 Changing the password from the front panel ....... 2-6 Changing the password by remote ..........2-6 Resetting the calibration password............2-6 Viewing calibration dates and calibration count ......... 2-7 Calibration errors ................2-7 Front panel error reporting ............2-7 Remote error reporting ..............
  • Page 10 Disassembly Introduction ..................5-2 Handling and cleaning .................5-2 Handling PC boards ..............5-2 Solder repairs ................5-2 Static sensitive devices ................5-3 Assembly drawings ................5-3 Case cover removal ................5-3 Analog board removal .................5-4 Digital board removal ................5-5 Front panel disassembly ..............5-6 Removing power components..............5-6 Power module removal ..............5-6 Instrument re-assembly................5-7 Replaceable Parts...
  • Page 11 Calibration Programs Introduction..................C-2 Computer hardware requirements ............C-2 Software requirements................ C-2 Calibration equipment................ C-2 General program instructions............. C-2 Program C-1 Model 2420 calibration program ......C-4 Requesting calibration constants............C-7 Program C-2 Requesting calibration constants ......C-7...
  • Page 12 List of Illustrations Performance Verification Connections for voltage verification tests........1-9 Connections for10µA to 1A range current verification tests ..1-11 Connections for 3A range current verification tests ....1-12 Connections for resistance accuracy verification....... 1-15 Calibration Voltage calibration test connections..........2-8 10µA to 1A range current calibration test connections....
  • Page 13 List of Tables Performance Verification Recommended verification equipment ..........1-3 Maximum compliance values............1-8 Output voltage accuracy limits............1-10 Voltage measurement accuracy limits ..........1-11 Output current accuracy limits ............1-13 Current measurement accuracy limits ..........1-14 Ohms measurement accuracy limits..........1-16 Calibration Recommended calibration equipment ..........2-4 Calibration unlocked states ..............2-5 Front panel voltage calibration............2-10 Front panel current calibration ............2-13...
  • Page 14 Command Reference Remote calibration command summary ......... B-2 Recommended :CAL:PROT:SENS parameter ranges ....B-6 Recommended :CAL:PROT:SOUR parameter ranges ....B-7 Calibration errors ................B-9...
  • Page 15: Performance Verification

    Performance Verification...
  • Page 16: Introduction

    NOTE If the instrument is still under warranty and its performance is outside specified limits, con- tact your Keithley representative or the factory to determine the correct course of action. Verification test requirements Be sure that you perform the verification tests: •...
  • Page 17: Line Power

    Performance Verification Line power The Model 2420 requires a line voltage of 90 to 250V and a line frequency of 50 to 60Hz. Verification tests must be performed within this range. Recommended test equipment Table 1-1 summarizes recommended verification equipment. You can use alternate equipment as long as that equipment has specifications at least as good as those listed in Table 1-1.
  • Page 18: 1Ω Resistor Characterization

    Performance Verification 1Ω resistor characterization The recommended 1Ω resistor should be characterized to ±300ppm or better before verifying the 3A current measurement range. (You need not characterize the resistor if you are checking only the 3A current source range.) Use the 4-wire ohms function of the DMM recommended in Table 1-1 to measure the resistance value, and then use that measured value to calculate the cur- rent during the 3A current measurement range test procedure.
  • Page 19: Restoring Factory Defaults

    Performance Verification Restoring factory defaults Before performing the verification procedures, restore the instrument to its factory front panel (bench) defaults as follows: Press the MENU key. The instrument will display the following prompt: MAIN MENU SAVESETUP COMMUNICATION CAL Select SAVESETUP, and then press ENTER. The unit then displays: SAVESETUP MENU GLOBAL SOURCE-MEMORY Select GLOBAL, and then press ENTER.
  • Page 20: Test Considerations

    Performance Verification Test considerations When performing the verification procedures: • Be sure to restore factory front panel defaults as previously outlined. • Make sure that the test equipment is properly warmed up and connected to the Model 2420 INPUT/OUTPUT jacks. Also be sure that the front panel jacks are selected with the TERMINALS key.
  • Page 21: Setting The Measurement Range

    Performance Verification Setting the measurement range When simultaneously sourcing and measuring either voltage or current, the measure range is coupled to the source range, and you cannot independently control the measure range. Thus, it is not necessary for you to set the measure range when testing voltage or current measurement accuracy.
  • Page 22: Maximum Compliance Values

    Performance Verification Maximum compliance values The maximum compliance values for the measurement ranges are summarized in Table 1-2. Table 1-2 Maximum compliance values Measurement Maximum range compliance value 200mV 210mV 2.1V 10µA 10.5µA 105 µA 100µA 1.05mA 10mA 10.5mA 100mA 105mA 1.05A 3.15A...
  • Page 23: Output Voltage Accuracy

    Performance Verification Output voltage accuracy Follow the steps below to verify that Model 2420 output voltage accuracy is within specified limits. This test involves setting the output voltage to each full-range value and measuring the voltages with a precision digital multimeter. With the power off, connect the digital multimeter to the Model 2420 INPUT/OUTPUT jacks, as shown in Figure 1-1.
  • Page 24: Voltage Measurement Accuracy

    1-10 Performance Verification Table 1-3 Output voltage accuracy limits Model 2420 Model 2420 output Output voltage limits source range voltage setting (1 year, 18°C-28°C) 200mV 200.000mV 199.360 to 200.640mV 2.00000V 1.99900 to 2.00100V 20.0000V 19.9936 to 20.0064V 60.0000V 59.9808 to 60.0192V Voltage measurement accuracy Follow the steps below to verify that Model 2420 voltage measurement accuracy is within specified limits.
  • Page 25: Output Current Accuracy

    Performance Verification 1-11 Table 1-4 Voltage measurement accuracy limits Model 2420 source Model 2420 voltage reading Source voltage* and measure range* limits (1 year, 18°C-28°C) 200mV 200.000mV 199.676 to 200.324mV 2.00000V 1.99946 to 2.00054V 20.0000V 19.9960 to 20.0040V 60.0000V 59.9880 to 60.0120V *Measure range coupled to source range when simultaneously sourcing and measuring voltage.
  • Page 26 1-12 Performance Verification Verify output current accuracy for the 10µA-1A range currents listed in Table 1-5. For each test point: • Select the correct source range. • Set the Model 2420 output current to the correct value. • Verify that the multimeter reading is within the limits given in the table. Repeat the procedure for negative output currents with the same magnitudes as those listed in Table 1-5.
  • Page 27: Current Measurement Accuracy

    Performance Verification 1-13 Table 1-5 Output current accuracy limits Model 2420 Model 2420 Output current limits source range output current setting (1 year, 18°C-28°C) 10µA 10.0000µA 9.9947 to 10.0053µA 100µA 100.000µA 99.949 to 100.051µA 1.00000mA 0.99946 to 1.00054mA 10mA 10.0000mA 9.9935 to 10.0065mA 100mA 100.000mA...
  • Page 28: Current Measurement Accuracy Limits

    1-14 Performance Verification 3A range accuracy The 1 Ω resistor should be characterized to within ±300ppm before verifying the 3A NOTE current measurement range. Use the 4-wire ohms function of the DMM to measure the resistance value, and then use that measured value to calculate the current during the measurement procedure.
  • Page 29: Resistance Measurement Accuracy

    Performance Verification 1-15 Resistance measurement accuracy Use the following steps to verify that Model 2420 resistance measurement accuracy is within specified limits. This procedure involves applying accurate resistances from a resis- tance calibrator and then verifying that Model 2420 resistance measurements are within re- quired limits.
  • Page 30: Ohms Measurement Accuracy Limits

    1-16 Performance Verification Select the resistance calibrator external sense mode. Configure the Model 2420 ohms function for the 4-wire sense mode as follows: • Press CONFIG then MEAS Ω. The instrument will display the following: CONFIG OHMS SOURCE SENSE-MODE GUARD •...
  • Page 31: Calibration

    Calibration...
  • Page 32: Introduction

    Calibration Introduction Use the procedures in this section to calibrate the Model 2420. These procedures require accurate test equipment to measure precise DC voltages and currents. Calibration can be performed either from the front panel or by sending SCPI calibration commands over the IEEE-488 bus or RS-232 port with the aid of a computer.
  • Page 33: Calibration Considerations

    Calibration Calibration considerations When performing the calibration procedures: • Make sure that the test equipment is properly warmed up and connected to the Model 2420 front panel INPUT/OUTPUT jacks. Also be certain that the front panel jacks are selected with the TERMINALS switch. •...
  • Page 34: 1Ω Resistor Characterization

    Calibration Table 2-1 Recommended calibration equipment Description Manufacturer/Model Specifications Digital Multimeter Hewlett Packard DC Voltage* ±5.6ppm HP3458A 10V: ±4.3ppm 100V ±6.3ppm DC Current* 10µA: ±25ppm 100µA: ±23ppm 1mA: ±20ppm 10mA: ±20ppm 100mA: ±35ppm ±110ppm Precision Resistor** Isotec RUG-Z-1R00-0.1 1Ω, ±0.1%, 100W *90-day, full-range accuracy specifications of ranges required for various measurement points.
  • Page 35: Unlocking Calibration By Remote

    Calibration Once the correct password is displayed, press the ENTER key. If the password was cor- rectly entered, the following message will be displayed: CALIBRATION UNLOCKED Calibration can now be executed. Press EXIT to return to normal display. Calibration will be unlocked and assume the states summarized in Table 2-2.
  • Page 36: Changing The Password

    Calibration Changing the password The default password may be changed from the front panel or via remote as discussed below. Changing the password from the front panel Follow the steps below to change the password from the front panel: Press the MENU key, then choose CAL and press ENTER. The instrument will display the following: CALIBRATION UNLOCK EXECUTE VIEW-DATES...
  • Page 37: Viewing Calibration Dates And Calibration Count

    Calibration Viewing calibration dates and calibration count When calibration is locked, only the UNLOCK and VIEW-DATES selections will be acces- sible in the calibration menu. To view calibration dates and calibration count at any time: From normal display, press MENU, select CAL, and then press ENTER. The unit will display the following: CALIBRATION UNLOCK EXECUTE VIEW-DATES...
  • Page 38: Voltage Calibration Test Connections

    Calibration Press the MENU key, then choose CAL and press ENTER. Select UNLOCK, and then press ENTER. The instrument will display the following: PASSWORD: , ENTER or EXIT. Use the up and down range keys to select the letter or number, and use the left and right arrow keys to choose the position.
  • Page 39 Calibration Press ENTER. The Model 2420 will source +200mV and simultaneously display the fol- lowing: DMM RDG: +200.0000mV , ENTER, or EXIT. Note and record the DMM reading, and then adjust the Model 2420 display to agree exactly with the actual DMM reading. Use the up and down arrow keys to select the digit value, and use the left and right arrow keys to choose the digit position (or use the num- ber keys, 0-9, +/-).
  • Page 40: Front Panel Voltage Calibration

    2-10 Calibration Table 2-3 Front panel voltage calibration Source Multimeter voltage Source voltage range* reading** 0.2V +200.00mV ___________ mV +000.00mV ___________ mV -200.00mV ___________ mV -000.00mV ___________ mV +2.0000V ___________ V +0.0000V ___________ V -2.0000V ___________ V -0.0000V ___________ V +20.000V ___________ V +00.000V...
  • Page 41 Calibration 2-11 From normal display, press the SOURCE I key. Press the EDIT key to select the source display field, and then use the down RANGE key to select the 10µA source range. From normal display, press MENU. Select CAL, and then press ENTER. The unit will display the following: CALIBRATION UNLOCK EXECUTE VIEW-DATES SAVE LOCK CHANGE-PASSWORD...
  • Page 42: Range Current Calibration Test Connections

    2-12 Calibration Press ENTER The Model 2420 will source -0µA and simultaneously display the following: DMM RDG: +00.00000µA , ENTER, or EXIT. Note and record the DMM reading, and then adjust the display to agree with the DMM reading. Once again, the maximum adjustment is within ±1% of the present range. After adjusting the display to agree with the DMM reading, press ENTER to complete calibration of the present range.
  • Page 43: Front Panel Current Calibration

    Calibration 2-13 Table 2-4 Front panel current calibration Multimeter Source range* Source current current reading** ___________ µA 10µA +10.000µA ___________ µA +00.000µA ___________ µA -10.000µA ___________ µA -00.000µA ___________ µA 100µA +100.00µA ___________ µA +000.00µA ___________ µA -100.00µA ___________ µA -000.00µA +1.0000mA ___________ mA...
  • Page 44: Remote Calibration

    2-14 Calibration Select SAVE, and then press ENTER. The instrument will display the following message: SAVE CAL Press ENTER to continue; EXIT to abort calibration sequence. Press ENTER. The unit will prompt you for the calibration date: CAL DATE: 2/15/97 , ENTER, or EXIT.
  • Page 45: Remote Calibration Commands

    Calibration 2-15 Remote calibration commands Table 2-5 summarizes remote calibration commands. For a more complete description of these commands, refer to Appendix B. Table 2-5 Remote calibration command summary Command Description :CALibration Calibration subsystem. :PROTected Cal commands protected by password. :CODE '<password>' Unlock cal;...
  • Page 46: Calibration

    2-16 Calibration Table 2-6 Recommended :CALibration:PROTected:SENse parameter ranges Sense First parameter Second parameter Third parameter range (zero) (negative full scale) (positive full scale) 0.2V -0.002 to +0.002 -0.18 to -0.22 +0.18 to +0.22 -0.02 to +0.02 -1.8 to -2.2 +1.8 to +2.2 -0.2 to +0.2 -18 to -22 +18 to +22...
  • Page 47: Remote Calibration Procedure

    Calibration 2-17 Remote calibration procedure Step 1: Prepare the Model 2420 for calibration Connect the Model 2420 to the controller IEEE-488 interface or RS-232 port using a shielded interface cable. Turn on the Model 2420 and the test equipment, and allow them to warm up for at least one hour before performing calibration.
  • Page 48: Calibration

    2-18 Calibration • Note and record the multimeter reading. • Send the source and sense commands using the multimeter reading as the parameter. For example: :CAL:PROT:SOUR 1.997 :CAL:PROT:SENS 1.997 • Send the SOUR:VOLT 0.0 command to set the source voltage to 0V. •...
  • Page 49: Voltage Range Calibration Commands

    Calibration 2-19 Table 2-9 Voltage range calibration commands Step Command/procedure* Description :SOUR:VOLT:RANGE <Range> Select source range. :SOUR:VOLT -<Source_value> Establish negative full-range polarity. Take DMM reading. Read actual output value. :CAL:PROT:SOUR <DMM_Reading> Calibrate sense function negative full scale. Check 2420 for errors. :CAL:PROT:SENS <DMM_Reading>...
  • Page 50: Current Calibration Initialization Commands

    2-20 Calibration • Program the source to output the negative full-range value using the :SOUR:CURR command. For example: :SOUR:CURR -1E-3 • Note and record the multimeter reading. • Use the multimeter reading as the parameter for the :CAL:PROT:SOUR and :CAL:PROT:SENS commands. For example, a typical value for the 1mA range would be: :CAL:PROT:SOUR -1.025E-3 :CAL:PROT:SENS -1.025E-3...
  • Page 51: Current Range Calibration Commands

    Calibration 2-21 Table 2-11 Current range calibration commands Step Command/procedure* Description :SOUR:CURR:RANGE <Range> Select source range. :SOUR:CURR -<Source_value> Establish negative full-range polarity. Take DMM reading. Read actual output value. :CAL:PROT:SOUR <DMM_Reading> Calibrate sense function negative full scale. Check 2420 for errors. :CAL:PROT:SENS <DMM_Reading>...
  • Page 52: Single-Range Calibration

    2-22 Calibration NOTE Calibration will be temporary unless you send the SAVE command. Also, calibra- tion data will not be saved if (1) calibration is locked, (2) invalid data exists, or (3) all steps were not completed. Step 6: Lock out calibration To lock out further calibration, send the following command after completing the calibration procedure: :CAL:PROT:LOCK...
  • Page 53: Routine Maintenance

    Routine Maintenance...
  • Page 54: Introduction

    Routine Maintenance Introduction The information in this section deals with routine type maintenance that can be performed by the operator. Line fuse replacement WARNING Disconnect the line cord at the rear panel, and remove all test leads connect- ed to the instrument (front and rear) before replacing the line fuse. The power line fuse is accessible from the rear panel, just above the AC power receptacle (see Figure 3-1).
  • Page 55: Power Line Fuse

    If the power line fuse continues to blow, a circuit malfunction exists and must be corrected. Refer to the troubleshooting section of this manual for additional in- formation. Table 3-1 Power line fuse Line voltage Rating Keithley part no. 90-250V 250V, 3.15A, Slow FU-106-3.15 Blow 5 × 20mm...
  • Page 56: Routine Maintenance

    Routine Maintenance...
  • Page 57: Troubleshooting

    Troubleshooting...
  • Page 58: Introduction

    Troubleshooting Introduction This section of the manual will assist you in troubleshooting and repairing the Model 2420. Included are self-tests, test procedures, troubleshooting tables, and circuit descriptions. Note that disassembly instructions are located in Section 5, and component layout drawings are at the end of Section 6.
  • Page 59: Front Panel Tests

    Troubleshooting Front panel tests There are three front panel tests: one to test the functionality of the front panel keys and two to test the display. In the event of a test failure, refer to Display board checks for details on trou- bleshooting the display board.
  • Page 60: Char Set Test

    Troubleshooting CHAR SET test The character set test lets you display all characters. Perform the following steps to run the character set test: Display the MAIN MENU by pressing the MENU key. Select TEST, and press ENTER to display the SELF-TEST MENU. Select DISPLAY-TESTS, and press ENTER to display the following menu: FRONT PANEL TESTS KEYS DISPLAY-PATTERNS CHAR-SET...
  • Page 61: Overall Block Diagram

    Troubleshooting Figure 4-1 Analog Section Overall block diagram Output Clamps DACs Output Stage Feedback Guard Guard Buffer Converter To Analog Circuits Output Stage Digital Circuits ±15V +5V ±42V ±85V +12V Front Display, Panel RS-232 I/O RS-232 Controller Keyboard Output Microcomputer Digital Analog Stage...
  • Page 62: Power Supply

    Troubleshooting D/A converters control the programmed voltage and current, or voltage compliance and current compliance. Each DAC has two ranges, a 10V full-scale output or a 1V full-scale output. The DAC outputs are fed to the summing node, FB. Either the V DAC or the I DAC has the ability to control the main loop.
  • Page 63: Output Stage

    Troubleshooting The offline switching power supply provides all power for the instrument while providing universal inputs and power factor correction for the 110/120V line. The digital board runs off of 5V and 12V supplies derived from the switcher. The +12VD supply is set to program the flash ROM.
  • Page 64: A/D Converter

    Troubleshooting The Model 2420 output stage serves two purposes: (1) it converts signals from floating com- mon to output common, and (2) it provides both voltage and current amplification. The output stage drive transistors are biased in class B configuration to prevent the possibility of thermal runaway with high-current output values.
  • Page 65: Display Board Circuit Theory

    Troubleshooting Figure 4-5 Digital circuitry block diagram U15, U16 U12, U14 Serial RS-232 Interface Interface Reset E PROM Microprocessor GPIB U6, U13 IEEE-488 Interface Control/Data A/D Interface U9, U25 To Display Board Controller 16.78MHz Voltage Source Trigger Control Trigger Digital I/O Digital Display board circuit theory Display board components are shown in the digital circuitry block diagram in Figure 4-5.
  • Page 66: Troubleshooting

    4-10 Troubleshooting The front panel keys (S901-S931) 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 strob- ing 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 encod- ing schemes.
  • Page 67: Power Supply Checks

    Troubleshooting 4-11 Power supply checks Power supply problems can be checked out using Table 4-2. See Principles of operation for circuit theory on the power supply. Table 4-2 Power supply checks Step Item.component Required condition Remarks Line fuse Check continuity. Remove to check.
  • Page 68: Analog Circuitry Checks

    “Reading buffer data lost” message shortly after the Model 2420 is switched on. The battery is a 3V wafer-type lithium cell, Panasonic type BR-2330 or equivalent (Keithley part number BA-46), which is located on the digital board. Replacement of the battery requires removal of the case cover and analog board assembly.
  • Page 69: Battery Replacement Procedure

    Troubleshooting 4-13 Battery replacement procedure Remove the case cover and analog board assembly as covered in Section 5. Locate the battery on the digital board. Carefully unsolder and remove the old battery. Install and solder the new battery in place. Re-assemble the instrument, and turn it on.
  • Page 70 4-14 Troubleshooting...
  • Page 71: Disassembly

    Disassembly...
  • Page 72: Introduction

    Disassembly Introduction This section explains how to handle, clean, and disassemble the Model 2420. 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.
  • Page 73: Static Sensitive Devices

    Disassembly 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 2420.
  • Page 74: Analog Board Removal

    Disassembly Remove mounting ears — Remove the screw that secures each mounting ear. Pull down and out on each mounting ear. NOTE When re-installing the mounting ears, make sure to mount the right ear to the right side of the chassis, and the left ear to the left side of the chassis. Each ear is marked “RIGHT”...
  • Page 75: Digital Board Removal

    Disassembly Remove screws. • Remove the two fastening screws that secure the analog board assembly to the chassis. These screws are located on the side of the board opposite from the heat sink. • Remove the two screws that secure the heat sink to the chassis. 4.
  • Page 76: Front Panel Disassembly

    Disassembly Front panel disassembly Use the following procedures to remove the display board and/or the pushbutton switch pad. Unplug the display board ribbon cables. Remove the front panel assembly. This assembly has four retaining clips that snap onto the chassis over four pem nut studs. Two retaining clips are located on each side of the front panel.
  • Page 77: Instrument Re-Assembly

    Disassembly Instrument re-assembly Re-assemble 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. To en- sure proper operation, replace the analog signal wire ferrite noise filters, and securely fasten the shield.
  • Page 78 Disassembly...
  • Page 84: Replaceable Parts

    Replaceable Parts...
  • Page 85: Parts Lists

    Component designation (if applicable) • Keithley part number Factory service If the instrument is to be returned to Keithley Instruments for repair, perform the following: • Call the Repair Department at 1-800-552-1115 for a Return Material Authorization (RMA) number. •...
  • Page 86: Analog Board Parts List

    Replaceable Parts Table 6-1 Analog board parts list Keithley Circuit designation Description part no. C200-203,205-210,225,226,231, CAP, .1UF, 10%, 25V, CERAMIC C-495-.1 232,237,238 C204,411,608,609 CAP, .01UF, 10%, 50V CERAMIC C-491-.01 C211-214 CAP, 1000PF,10%, 50V, MONO CERAMIC C-452-1000P C215-222,611 CAP,100PF, 5%, 100V, CERAMIC...
  • Page 87 Replaceable Parts Table 6-1 (cont.) Analog board parts list Keithley Circuit designation Description part no. C513 CAP,560PF,2.5%,630V,POLYPROPYLENE C-405-560P C515,541 CAP,.1UF, 20%,50V,CERAMIC C-418-.1 C522,523,526,527 CAP, 3300P, 10%, 500V, CERAMIC C-497-3300P C528,533 CAP, 3300P, 10%, 500V, CERAMIC C-497-3300P C534,535 CAP, 470UF, 20%, 63V ALUM ELEC...
  • Page 88 Replaceable Parts Table 6-1 (cont.) Analog board parts list Keithley Circuit designation Description part no. K200-205 N.C RELAY, 1 FORMB, AQV214S RL-176 K206,207,208 RELAY RL-207 K211 RELAY, SURFACE MOUNT RL-188 L201,500,501 CHOKE, SHIELD BEAD CH-52 L600,601,602 FERRITE CHIP 600 OHM BLM32A07...
  • Page 89 Replaceable Parts Table 6-1 (cont.) Analog board parts list Keithley Circuit designation Description part no. Q521 TRANSISTOR TG-357 Q522,524,600 TRANS, NPN, MMBT3904 TG-238 Q526,527,530,531 TRANS, N CHANNEL MOSFET, TG-302 SI9410DY Q532 TRANS,N-CHANNEL FET,IRF630 TG-214 Q533 TRANS,P-CHANNEL 200V FET,IRF9630 TG-215 R117-128,133-136,141-144...
  • Page 90 Replaceable Parts Table 6-1 (cont.) Analog board parts list Keithley Circuit designation Description part no. R272,273,346-348,511,512 RES, 249K, 1%, 100MW, THICK FILM R-418-249K R280 RES,4.02K,1%,100MW, THICK FILM R-418-4.02K R283,287,297,299,349,350- RES, 30.1K, 1%, 100MW, THICK FILM R-418-30.1K 352,457,461 R284-286,288,301,358,504, RES, 10K, 1%, 100MW, THICK FILM...
  • Page 91 Replaceable Parts Table 6-1 (cont.) Analog board parts list Keithley Circuit designation Description part no. R454,455,469,470,471,467,468 RES, 100, .1%, 1/10W, METAL FILM R-263-100 R463,479,473 RES, 30.1K, 1%, 100MW, THICK FILM R-418-30.1K R472,478,466,355,290,344,309 RES, 1K, 1%, 100MW, THICK FILM R-418-1K R474 RESISTOR R-473-.2...
  • Page 92 Replaceable Parts Table 6-1 (cont.) Analog board parts list Keithley Circuit designation Description part no. R614,615,553 RES, 2.21K, 1%, 100MW, THICK FILM R-418-2.21K R618 RES, 34K, 1%, 100MW, THICK FILM R-418-34K R619 RES, 4.75K, 1%, 100MW, THICK FILM R-418-4.75K R620 RES, 82.5, 1%, 100MW, THICK FILM...
  • Page 93 6-10 Replaceable Parts Table 6-1 (cont.) Analog board parts list Keithley Circuit designation Description part no. U228,263 IC, OP-AMP, LOW NOISE LT1007CS8 IC-949 U231,219,235,234,262 IC, OP AMP, LOW POWER AD795JR IC-1052 U238,201 IC, CMOS ANA SWITCH SPST IC-909 MAX326CSE U239...
  • Page 94 Replaceable Parts 6-11 Table 6-1 (cont.) Analog board parts list Keithley Circuit designation Description part no. VR202,203,407-409,506,507 DIODE,ZENER 5.1V, BZX84C5V1 DZ-88 VR214,215 DIODE, ZENER, 8.2V, MMBZ5237 DZ-92 VR400,401 DIODE, ZENER 4.7V, IN4732A DZ-67 VR410,601,604 DIODE, ZENER 3.3V, MMBZ5226BL DZ-94 VR500,501 DIODE, ZENER 6.0V, BZX84B6V2...
  • Page 95: Digital Board Parts List

    6-12 Replaceable Parts Table 6-2 Digital board parts list Keithley Circuit designation Description part no. BATTERY BA-46 C1,3,77,11,14,16,17,20,22,23,25,26,30 CAP, .1UF, 10%, 25V, CERAMIC C-495-.1 C103 CAP, 100UF, 20%, 10V, ALUM ELEC C-483-100 C104 CAP,10UF,20%,63V,ALUM ELEC C-403-10 C105,108,109,111 CAP, 47UF, 20%, 100V ALUM ELEC...
  • Page 96 Replaceable Parts 6-13 Table 6-2 (cont.) Digital board parts list Keithley Circuit designation Description part no. C84,6,7,9,18,90,52,70,71,73,64,102 CAP, .1UF, 10%, 25V, CERAMIC C-495-.1 CAP, 470UF, -20+100%, 16V ALUMINUM C-313-470 C96,106,112,118 CAP, 22UF, -10+100%, 35v ELECTRO- C-309-22 LYTIC CAPACITOR, POLYESTER C-553-.47 CAP, .01uF, 20%, 50V, CERAMIC...
  • Page 97 6-14 Replaceable Parts Table 6-2 (cont.) Digital board parts list Keithley Circuit designation Description part no. P1035 LATCHING HEADER,FRICTON, SGL CS-724-3 POWER SUPPLY PS-54-2A Q1,3,4,5,6 TRANS, N-MOSFET, VN0605T TG-243 TRANS, NPN, MMBT3904 TG-238 TRANSISTOR TG-338 Q7,12,8 POWER MOSFET IRFZ346 TG-313...
  • Page 98 Replaceable Parts 6-15 Table 6-2 (cont.) Digital board parts list Keithley Circuit designation Description part no. RESISTOR, METAL FILM R-464-100K RES, 8.06K, 1%, .1W THICK FILM R-418-8.06K R73,74,76,78-81,83,7,60,69,71,85-89 RES, 10K, 1%, 100MW, THICK FILM R-418-10K RES, 15k, 1%, 100MW, THICK FILM...
  • Page 99 6-16 Replaceable Parts Table 6-2 (cont.) Digital board parts list Keithley Circuit designation Description part no. IC, MICROMANAGER, DS12365-10 IC-884 IC,OCTAL INTERFACE BUS,75160 IC-646 IC, DUAL POWER MOSFET DRIVER, IC-437 TSC426 IC, DUAL D-TYPE F/F, 74HC74 IC-773 U23,25 IC,POS NAND GATES/INVERT,74HCT14...
  • Page 100: Display Board Parts List

    Replaceable Parts 6-17 Table 6-3 Display board parts list Keithley Circuit designation Description part no. C901 CAP,22UF, 20%, 6.3,TANTALUM C-417-22 C902,904,907,908,910 CAP, .1UF, 20%,100V, CERAMIC C-436-.1 C903,905,906,909,911 CAP,.1UF, 20%,50V,CERAMIC C-418-.1 C912 CAP, 2.2UF, 20%,100V, ALUM ELEC C-503-2.2 C913,914 CAP,100UF,20%,16V, TANTALUM...
  • Page 101: Rear Panel

    6-18 Replaceable Parts Table 6-4 Mechanical parts list Description Keithley part no. FN-33-2 LINE FILTER LF-11 LU-88 LED, HIGH POWER PL-94 CHASSIS ASSEMBLY 2420-302A REAR PANEL 2400-303B CHASSIS 2420-301A BANANA JACK, PUSH-IN BLACK BJ-14-0 BANANA JACK, PUSH-IN RED BJ-14-2 BANANA JACK, PUSH-IN BLUE...
  • Page 107 Specifications...
  • Page 108 2400, 2400-C, 2410, 2410-C, SourceMeter Line Specifications ® 2420, 2420-C, 2425, 2425-C, 2430, 2430-C, 2440, 2440-C SOURCE SPECIFICATIONS ADDITIONAL SOURCE SPECIFICATIONS TRANSIENT RESPONSE TIME: 30µs minimum for the output to recover VOLTAGE PROGRAMMING ACCURACY (Local or Remote Sense) to its spec. following a step change in load. ACCURACY (1 Year) NOISE COMMAND PROCESSING TIME: Maximum time required for the output...
  • Page 109 2400, 2400-C, 2410, 2410-C, SourceMeter Line Specifications ® 2420, 2420-C, 2425, 2425-C, 2430, 2430-C, 2440, 2440-C 1, 2, 7 MEASURE SPECIFICATIONS CONTACT CHECK SPECIFICATIONS VOLTAGE MEASUREMENT ACCURACY (Local or Remote Sense) SPEED: 350µs for verification and notification. ACCURACY (1 Year) CONTACT CHECK: 2Ω...
  • Page 110 ACCESSORIES SUPPLIED: Model 1754 Universal Test Lead Kit, User’s Manual, tery life). Service Manual, LabVIEW and TestPoint Drivers. Specifications subject to change without notice. SourceMeter is a registered trademark of Keithley Instruments, Inc. ® Rev. A All other trademarks are the property of their respective companies. 5/17/01...
  • Page 111 Specifications Accuracy calculations The information below discusses how to calculate accuracy for both measurement and source functions. Measurement accuracy Measurement accuracy is calculated as follows: Accuracy = ±(% of reading + offset) As an example of how to calculate the actual reading limits, assume that you are measuring 10V on the 20V range.
  • Page 112 Specifications...
  • Page 113 Command Reference...
  • Page 114 Command Reference Introduction This appendix contains detailed information on the various Model 2420 remote calibration commands, calibration error messages, and methods to detect the end of each calibration step. Section 2 of this manual covers detailed calibration procedures. Command summary Table B-1 summarizes Model 2420 calibration commands.
  • Page 115 Command Reference Miscellaneous commands Miscellaneous commands are those commands that perform such functions as saving calibra- tion constants, locking out calibration, and programming date parameters. :CODE (:CALibration:PROTected:CODE) Purpose To unlock calibration so that you can perform the calibration procedures. Format :cal:prot:code '<password>' Parameter Up to a 8-character string including letters and numbers.
  • Page 116 Command Reference Description The :LOCK command allows you to lock out comprehensive calibration af- ter completing those procedures. Thus, :LOCK performs the opposite of sending the password with the :CODE command. The :LOCK? query returns calibration lock status. Note To unlock calibration, send the :CODE command with the appropriate pass- word.
  • Page 117 Command Reference :NDUE (:CALibration:PROTected:NDUE) Purpose To send the next calibration due date to the instrument. Format :cal:prot:ndue <year>, <month>, <day> Parameters <year> = 1997 to 2096 <month> = 1 to 12 <day> = 1 to 31 Query :cal:prot:ndue? Response <year>, <month>, <day> Description The :NDUE command allows you to store the date when calibration is next due in instrument memory.
  • Page 118 Command Reference Table B-2 Recommended :CALibration:PROTected:SENSe parameter ranges Sense First parameter Second parameter Third parameter range (zero) (negative full scale) (positive full scale) 0.2V 0.002 to +0.002 -0.18 to -0.22 +0.18 to +0.22 0.02 to +0.02 -1.8 to -2.2 +1.8 to +2.2 0.2 to +0.2 -18 to -22 +18 to +22...
  • Page 119 Command Reference Note that parameters for a given source function and range may be sent in any order; however, once one :CAL:PROT:SOUR command executes, the other three must also be executed, or an error number -200, "Execution error" will occur when the :CAL:PROT:SAVE command is processed at the end of the calibration procedure.
  • Page 120 Command Reference :DATA? (:CALibration:PROTected:SENSe:DATA?) (:CALibration:PROTected:SOURce:DATA?) Purpose To request the calibration constants for the active range. Format :cal:prot:sens:data? :cal:prot:sour:data? Response Four comma-separated ASCII floating-point constants Description The :CAL:PROT:SENS:DATA? and :CAL:PROT:SOUR:DATA? queries re- quest the calibration constants for the active range of the sense and source functions respectively.
  • Page 121 Command Reference Error 505 — Will occur when a :CAL:PROT:SOUR command generates an invalid source off- set calibration constant. Error 506 — Will occur when a :CAL:PROT:SOUR command generates an invalid source gain calibration constant. Error 507 — Will occur when a :CAL:PROT:SENS command generates an invalid measure- ment offset calibration constant.
  • Page 122 B-10 Command Reference Detecting calibration step completion When sending remote calibration commands, you must wait until the instrument completes the current operation before sending another 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 out- put queue when it has completed each step.
  • Page 123 Command Reference B-11 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 2420. 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 command line, as covered above.
  • Page 124 B-12 Command Reference...
  • Page 125 Calibration Programs...
  • Page 126 The following computer hardware is required to run the calibration programs: • IBM PC 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 programs, you will need the following computer software: •...
  • Page 127 Calibration Programs Make sure the digital multimeter primary address is set to its factory default setting (22). Make sure that the computer bus driver software (CECHP.EXE) is properly initialized. Enter the QBasic editor, and type in the program below. Be sure to change the OneOhm parameter to the characterized value of 1 Ω resistor. NOTE (See Section 2 for details.) Check thoroughly for errors, then save it using a convenient filename.
  • Page 128 Calibration Programs Program C-1 Model 2420 calibration program ' Model 2420 calibration program for use with the HP3458A Digital Multimeter. ' Rev. 1.0, 1/16/97 ' 2420 primary address = 24. HP3458A primary address = 22. OPEN "IEEE" FOR OUTPUT AS #1 ' Open IEEE-488 output path.
  • Page 129 Calibration Programs GOSUB CalEnd CASE 5, 11 PRINT #1, "OUTPUT 24;"; Cmd$ GOSUB ReadDMM CASE 8 PRINT #1, "OUTPUT 24;"; Cmd$; Source GOSUB ReadDMM END SELECT NEXT I Range = Range * 10 IF J = 1 AND Range = 200 THEN Range = 60 IF J = 2 AND Range >...
  • Page 130 Calibration Programs INPUT #2, S RETURN ErrCheck: ' Error check routine. PRINT #1, "OUTPUT 24;:SYST:ERR?" ' Query error queue. PRINT #1, "ENTER 24" INPUT #2, E, Err$ IF E <> 0 THEN PRINT Err$: GOTO EndProg' Display error. RETURN ReadDMM: ' Get reading from DMM.
  • Page 131 Calibration Programs Requesting calibration constants Program C-2 listed below demonstrates how to request the calibration constants from the Model 2420. The program requests and displays the calibration constants for all ranges of both the volts and current source and measurement functions. Program C-2 Requesting calibration constants ' Example program to request calibration constants.
  • Page 132 Calibration Programs LINE INPUT #2, Data$ PRINT Data$ Range = Range * 10 IF Range > 9 AND Range < 11 THEN Range = 3 LOOP WHILE Range <= 3 PRINT #1, "OUTPUT 24;:CAL:PROT:LOCK" ' Lock out calibration. PRINT #1, "OUTPUT 24;*RST" PRINT #1, "LOCAL 24"...
  • Page 133 Index Display board checks 4-10 Display board circuit theory 4-9 DISPLAY PATTERNS test 4-3 1Ω resistor characteristics 1-3, 2-4 Environmental conditions 1-2, 2-2 A/D converter 4-8 Error summary B-8 Accuracy calculations A-10 Example limits calculation 1-4 Active guard 4-8 Analog board removal 5-4 Analog circuitry checks 4-12 Factory service 6-2 Analog circuits 4-4...
  • Page 134 No comm link error 4-13 Setting the measurement range 1-7 Setting the source range and output value 1-6 Single-range calibration 2-22 Software requirements C-2 Ordering information 6-2 Solder repairs 5-2 Output current accuracy 1-11 Source accuracy A-10 Output stage 4-7 Specifications A-1 Output voltage accuracy 1-9 Static sensitive devices 5-3...
  • Page 135 Service Form Model No. ______________ Serial No.___________________Date ________________ Name and Telephone No. _________________________________________________ Company ______________________________________________________________ List all control settings, describe problem and check boxes that apply to problem. _________________________ __________________________________________________________________________________________ __________________________________________________________________________________________ Intermittent Analog output follows display Particular range or function bad; specify _______________________________ IEEE failure Obvious problem on power-up...
  • Page 136 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 Instruments, Inc. 28775 Aurora Road • Cleveland, Ohio 44139 • 440-248-0400 • Fax: 440-248-6168 1-888-KEITHLEY (534-8453) www.keithley.com...

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