Keithley 2425 Service Manual
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Keithley 2425 Service Manual

100w sourcemeter
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Model 2425
100W 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

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Summary of Contents for Keithley 2425

  • Page 1 Model 2425 100W 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 2 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 3 TAIWAN: 1FL., 85 Po Ai Street • Hsinchu, Taiwan, R.O.C. • 886-3-572-9077• Fax: 886-3-572-9031...
  • Page 4 Model 2425 100W SourceMeter ® Service Manual ©2000, Keithley Instruments, Inc. All rights reserved. Cleveland, Ohio, U.S.A. Second Printing, October 2004 Document Number: 2425-902-01 Rev. B...
  • Page 5 Revision A (Document Number 2425-902-01)............. August 2000 Revision B (Document Number 2425-902-01) ............October 2004 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 Measurement Category I and Measurement Category II, as described in the International Electrotechnical Commission (IEC) Standard IEC 60664. Most measurement, control, and data I/O signals are Measurement Category I and must not be directly connected to mains voltage or to voltage sources with high transient 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 ........... 1-3 Warm-up period ..............1-3 Line power ................1-3 Recommended test equipment ........... 1-4 1Ω resistor characterization ..........1-5 Verification limits ..............1-5 Example limits calculation ..........1-5 Resistance limits calculation ..........
  • Page 9 Unlocking calibration ..............2-5 Unlocking calibration from the front panel ......2-5 Unlocking calibration by remote ......... 2-6 Changing the password ............... 2-7 Changing the password from the front panel ...... 2-7 Changing the password by remote ........2-7 Resetting the calibration password ..........2-8 Viewing calibration dates and calibration count ......
  • Page 10 Troubleshooting ............... 4-13 Display board checks ............4-13 Power supply checks ............4-14 Digital circuitry checks ............. 4-15 Analog circuitry checks ............ 4-16 Battery replacement ..............4-16 Battery replacement precautions ........4-17 Battery replacement procedure ......... 4-17 No comm link error ..............4-18 Disassembly Introduction ................
  • Page 11 Introduction ................C-2 Computer hardware requirements ..........C-2 Software requirements ............... C-2 Calibration equipment ............... C-2 General program instructions ............ C-3 Program C-1 Model 2425 calibration program ....C-4 Requesting calibration constants ..........C-7 Program C-2 Requesting calibration constants ....C-7...
  • Page 12 List of Illustrations Performance Verification Figure 1-1 Connections for voltage verification tests ......1-10 Figure 1-2 Connections for 10µA to 1A range current verification tests ..........1-13 Figure 1-3 Connections for 3A range current verification tests .... 1-14 Figure 1-4 Connections for resistance accuracy verification ....
  • Page 13 List of Tables Performance Verification Table 1-1 Recommended verification equipment ........1-4 Table 1-2 Maximum compliance values ..........1-9 Table 1-3 Output voltage accuracy limits ..........1-11 Table 1-4 Voltage measurement accuracy limits ......... 1-12 Table 1-5 Output current accuracy limits ..........1-15 Table 1-6 Current measurement accuracy limits ........
  • Page 14 Replacement Parts Table 6-1 Analog board parts list ............6-3 Table 6-2 Digital board parts list ............6-13 Table 6-3 Display board parts list ............6-19 Table 6-4 Mechanical parts list ............6-20 Command Reference Table B-1 Remote calibration command summary ....... B-2 Table B-2 Recommended :CALibration:PROTected:SENSe parameter ranges ............

  • Page 16: Performance Verification

    Performance Verification...

  • Page 17: Introduction

    Performance Verification Model 2425 Service Manual Introduction Use the procedures in this section to verify that Model 2425 accuracy is within the limits stated in the instrument’s one-year accuracy specifications. You can perform these verifi- cation procedures: • When you first receive the instrument to make sure that it was not damaged during shipment.

  • Page 18: Environmental Conditions

    Also, allow the test equipment to warm up for the minimum time specified by the manu- facturer. Line power The Model 2425 requires a line voltage of 100 to 240V and a line frequency of 50 or 60Hz. Verification tests must be performed within this range.

  • Page 19: Recommended Test Equipment

    Keep in mind, however, that test equipment uncertainty will add to the uncertainty of each measurement. Generally, test equipment uncertainty should be at least four times better than corresponding Model 2425 specifications. Table 1-1 lists the specifications of the recommended test equipment, including maximum allowable uncertainty for alternate test equipment (shown in parentheses).

  • Page 20: 1Ω Resistor Characterization

    As an example of how verification limits are calculated, assume you are testing the 20V DC output range using a 20V output value. Using the Model 2425 20V range one-year accuracy specification of ±(0.02% of output + 2.4mV offset), the calculated output limits are: Output limits = 20V ±...

  • Page 21: Restoring Factory Defaults

    DC current measurement accuracy • Resistance measurement accuracy If the Model 2425 is not within specifications and not under warranty, see the calibration procedures in Section 2 for information on calibrating the unit. Test considerations When performing the verification procedures: •...

  • Page 22: Setting The Source Range And Output Value

    • Allow the Model 2425 output signal to settle before making a measurement. • Do not connect test equipment to the Model 2425 through a scanner, multiplexer, or other switching equipment. WARNING The maximum common-mode voltage (voltage between LO and chas- sis ground) is 250V peak.

  • Page 23: Setting The Measurement Range

    Performance Verification Model 2425 Service Manual 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 24: Maximum Compliance Values

    Model 2425 Service Manual 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 100V 105V 10μA 10.5μA 105 μA 100μA...

  • Page 25: Taking The Sourcemeter Out Of Compliance

    Output voltage accuracy Follow the steps below to verify that Model 2425 output voltage accuracy is within speci- fied limits. This test involves setting the output voltage to each full-range value and mea- suring the voltages with a precision digital multimeter.

  • Page 26: Voltage Measurement Accuracy

    99.968 to 100.032V Voltage measurement accuracy Follow the steps below to verify that Model 2425 voltage measurement accuracy is within specified limits. The test involves setting the source voltage to full-range values, as mea- sured by a precision digital multimeter, and then verifying that the Model 2425 voltage readings are within required limits.

  • Page 27: Table 1-4 Voltage Measurement Accuracy Limits

    • Select the correct source range. • Set the Model 2425 output voltage to the indicated value as measured by the digital multimeter. • Verify that the Model 2425 voltage reading is within the limits given in the table.

  • Page 28: Output Current Accuracy

    1-13 Output current accuracy Follow the steps below to verify that Model 2425 output current accuracy is within speci- fied limits. The test involves setting the output current to each full-range value and mea- suring the currents with a precision digital multimeter.

  • Page 29: Figure 1-3 Connections For 3A Range Current Verification Tests

    With the power off, connect the digital multimeter and the 1Ω resistor to the Model 2425 INPUT/OUTPUT jacks, as shown in Figure 1-3. Select the multimeter DC volts measuring function. Press the Model 2425 SOURCE I key to source current, and make sure the source output is turned on. Figure 1-3...

  • Page 30: Table 1-5 Output Current Accuracy Limits

    • Select the 3A source range. • Set the Model 2425 output current to the correct 3A output value. • Verify that the multimeter reading is within the 3A range limits given in Table 1-5. (Since the value of the 1Ω resistor value is assumed to be the same as its nominal value, the DMM voltage reading is the same as the sourced current.)

  • Page 31: Current Measurement Accuracy

    • Select the correct source range. • Set the Model 2425 source output to the correct value as measured by the digital mul- timeter. • Verify that the Model 2425 current reading is within the limits given in the table.

  • Page 32: Table 1-6 Current Measurement Accuracy Limits

    Verify measurement current accuracy for the 3A range as follows: • Select the 3A source range. • Set the Model 2425 source output to the correct 3A value as measured by the digital multimeter. • Note the DMM voltage reading, and then calculate the current from the voltage read- ing and characterized 1Ω...

  • Page 33: Resistance Measurement Accuracy

    Model 2425 Service Manual Resistance measurement accuracy Use the following steps to verify that Model 2425 resistance measurement accuracy is within specified limits. This procedure involves applying accurate resistances from a resistance calibrator and then verifying that Model 2425 resistance measurements are within required limits.

  • Page 34: Table 1-7 Ohms Measurement Accuracy Limits

    Select the appropriate ohms measurement range with the RANGE keys. • Verify that the Model 2425 resistance reading is within the limits given in the table. Repeat the entire procedure using the rear panel INPUT/OUTPUT and 4-WIRE SENSE jacks. Be sure to select the rear panel jacks with the front panel TERMI- NALS key.
  • Page 35 1-20 Performance Verification Model 2425 Service Manual...

  • Page 36: Calibration

    Calibration...

  • Page 37: Introduction

    Also, allow the test equipment to warm up for the minimum time specified by the manu- facturer. Line power Model 2425 requires a line voltage of 100 to 240V at line frequency of 50 or 60Hz. The instrument must be calibrated while operating from a line voltage within this range.

  • Page 38: Calibration Considerations

    • Always allow the source signal to settle before calibrating each point. • Do not connect test equipment to the Model 2425 through a scanner or other switching equipment. • If an error occurs during calibration, the Model 2425 will generate an appropriate error message.

  • Page 39: Recommended Calibration Equipment

    For optimum calibration accuracy, test equipment specifications should be at least four times better than corresponding Model 2425 specifications. Table 2-1 Recommended calibration equipment...

  • Page 40: Unlocking Calibration

    Model 2425 Service Manual Calibration Unlocking calibration Before performing calibration, you must first unlock calibration by entering or sending the calibration password as explained in the following paragraphs. Unlocking calibration from the front panel Press the MENU key, then choose CAL, and press ENTER. The instrument will...

  • Page 41: Unlocking Calibration By Remote

    Calibration Model 2425 Service Manual Table 2-2 Calibration unlocked states Mode State Equivalent remote command Concurrent Functions :SENS:FUNC:CONC OFF Sense Function Source :SENS:FUNC <source_ function> Sense Volts NPLC :SENS:VOLT:NPLC 1.0 Sense Volts Range Source V :SENS:VOLT:RANG <range> Sense Current NPLC :SENS:CURR:NPLC 1.0...

  • Page 42: Changing The Password

    Model 2425 Service Manual Calibration Changing the password The default password may be changed from the front panel or via remote as discussed next. 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.

  • Page 43: Resetting The Calibration Password

    NEXT CAL: 12/15/1999 Last calibration: 12/15/1999 Count: 0001 Calibration errors The Model 2425 checks for errors after each calibration step, minimizing the possibility that improper calibration may occur due to operator error. Front panel error reporting If an error is detected during comprehensive calibration, the instrument will display an appropriate error message (see Appendix B).

  • Page 44: Remote Error Reporting

    2) in the status byte. (Use the *STB? query to request the status byte.) Query the instrument for the type of error by using the appropriate :SYST:ERR? query. The Model 2425 will respond with the error number and a text message describing the nature of the error. See Appendix B for details.

  • Page 45: Figure 2-1 Voltage Calibration Test Connections

    Step 2: Voltage calibration. Perform the steps below for each voltage range, using Table 2-3 as a guide. Connect the Model 2425 to the digital multimeter, as shown in Figure 2-1. Select the multimeter DC volts measurement function. Figure 2-1...
  • Page 46 After adjusting the display to agree with the DMM reading, press ENTER. The instrument will then display the following: V-CAL Press ENTER to Output +000.00mV Press ENTER. The Model 2425 will source 0mV and at the same time display the following: DMM RDG: +000.0000mV , ENTER or EXIT.

  • Page 47: Table 2-3 Front Panel Voltage Calibration

    2-12 Calibration Model 2425 Service Manual 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 com- plete calibration of the present range.

  • Page 48: Figure 2-2 10Μa To 1A Range Current Calibration Test Connections

    Step 3: Current calibration. Perform the following steps for each current range, using Table 2-4 as a guide. Connect the Model 2425 to the digital multimeter, as shown in Figure 2-2. Select the multimeter DC current measurement function. Figure 2-2 10μA to 1A range current calibration test connections...
  • Page 49 After adjusting the display to agree with the DMM reading, press ENTER. The instrument will then display the following: I-CAL Press ENTER to Output +00.000μA Press ENTER. The Model 2425 will source 0mA and at the same time display the following: DMM RDG: +00.00000μA , ENTER or EXIT.

  • Page 50: Figure 2-3 3A Range Current Calibration Test Connections

    EDIT and up RANGE keys before calibrating each range. After calibrating the 1A range, connect the 1Ω characterized resistor and DMM to the Model 2425 INPUT/OUTPUT jacks, as shown in Figure 2-3. Select the DMM DC volts function.

  • Page 51: Table 2-4 Front Panel Current Calibration

    2-16 Calibration Model 2425 Service Manual 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...
  • Page 52 NOTE For temporary calibration without saving new calibration constants, proceed to Step 5: Lock out calibration. From normal display, press MENU. Select CAL, and then press ENTER. The Model 2425 will display the following: CALIBRATION UNLOCK EXECUTE VIEW-DATES © SAVE LOCK CHANGE-PASSWORD ß...

  • Page 53: Remote Calibration

    Cal commands protected by password. :CODE '<password>' Unlock cal; changes password if cal is already unlocked. (Default password: KI002425.) :COUNT? Query number of times 2425 has been calibrated. :SAVE Save calibration data to EEPROM.* :LOCK Lock calibration, inhibit SAVE command operation.

  • Page 54: Recommended Calibration Parameters

    Model 2425 Service Manual Calibration 2-19 Recommended calibration parameters The maximum calibration command parameter ranges are: 75% to 150% of full scale for positive and negative full scale calibration points; ± zero calibration steps have ±50% of full scale for valid entry ranges. However, for optimum calibration, it is recommended that you use calibration points within the ranges listed in Table 2-6 and Table 2-7.

  • Page 55: Remote Calibration Procedure

    Connect the Model 2425 to the controller IEEE-488 interface or RS-232 port using a shielded interface cable. Turn on the Model 2425 and the test equipment, and allow them to warm up for at least one hour before performing calibration.
  • Page 56 Model 2425 Service Manual Calibration 2-21 Perform the range calibration steps listed in Table 2-9 for all ranges. For each range: • Send the :SOUR:VOLT:RANG command to select the source and sense range being calibrated. For example, for the 2V range, the following command...

  • Page 57: Table 2-8 Voltage Calibration Initialization Commands

    :OUTP:STAT ON Turn source on. Step 3: Current calibration. Connect the Model 2425 to the digital multimeter (Figure 2-2), and select the mul- timeter DC current function. Send the commands summarized in Table 2-10 in the order listed to initialize cur-...

  • Page 58: Table 2-9 Voltage Range Calibration Commands

    Model 2425 Service Manual Calibration 2-23 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.

  • Page 59: Table 2-10 Current Calibration Initialization Commands

    For example: :CAL:PROT:SOUR 1E-6 Connect the 1Ω resistor and DMM to the Model 2425 INPUT/OUPUT jacks, as shown in Figure 2-3. Select the DMM DC volts function. Repeat step 3 for the 3A range using the calculated current as follows: I = V/R, where V is the DMM voltage reading, and R is the characterized value of the 1Ω...

  • Page 60: Table 2-11 Current Range Calibration Commands

    Model 2425 Service Manual Calibration 2-25 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.

  • Page 61: Single-Range Calibration

    2-26 Calibration Model 2425 Service Manual Step 5: Save calibration constants. Calibration is now complete, so you can store the calibration constants in EEROM by sending the following command: :CAL:PROT:SAVE NOTE Calibration will be temporary unless you send the SAVE command. Also, calibration data will not be saved if (1) calibration is locked, (2) invalid data exists, or (3) all steps were not completed.

  • Page 62: Routine Maintenance

    Routine Maintenance...

  • Page 63: Introduction

    Routine Maintenance Model 2425 Service Manual 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 connected to the instrument (front and rear) before replacing the line fuse.

  • Page 64: Table 3-1 Power Line Fuse

    Model 2425 Service Manual Routine Maintenance CAUTION To prevent instrument damage, use only the fuse type specified in Table 3-1. Re-install the fuse carrier. NOTE If the power line fuse continues to blow, a circuit malfunction exists and must be corrected.
  • Page 65 Routine Maintenance Model 2425 Service Manual...

  • Page 66: Troubleshooting

    Troubleshooting...

  • Page 67: Introduction

    Use caution when working with hazardous voltages. Repair considerations Before making any repairs to the Model 2425, 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.

  • Page 68: Power-On Self-Test

    Model 2425 Service Manual Troubleshooting Power-on self-test During the power-on sequence, the Model 2425 will perform a checksum test on its EPROM and test its RAM. If one of these tests fails, the instrument will lock up. 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.

  • Page 69: Display Patterns Test

    Troubleshooting Model 2425 Service Manual DISPLAY PATTERNS test The display test lets you verify that each pixel and annunciator in the vacuum fluorescent display is working properly. Perform the following steps to run the display test: Display the MAIN MENU by pressing the MENU key.

  • Page 70: Principles Of Operation

    Figure 4-4 — Output stage simplified schematic Figure 4-5 — Digital circuitry block diagram Overall block diagram Figure 4-1 shows an overall block diagram of the Model 2425. Circuitry may be divided into three general areas: • Analog circuits — includes sourcing circuits such as the DACs, clamps, output stage, and feedback circuits, as well as measurement circuits such as the A/D con- verter.

  • Page 71: Figure 4-1 Overall Block Diagram

    Troubleshooting Model 2425 Service Manual Figure 4-1 Overall block diagram Analog Section Output DACs Clamps Output Stage Feedback Guard Guard Buffer Converter Front Display, Panel RS-232 I/O RS-232 Keyboard Controller Microcomputer Digital Trigger, GPIB GPIB I/O Digital Interface Trigger Link...

  • Page 72: Analog Circuits

    Model 2425 Service Manual Troubleshooting Analog circuits Figure 4-2 shows a block diagram of the analog circuits. 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.

  • Page 73: Power Supply

    A/D converter communication to the digital section. Power supply Figure 4-3 shows a block diagram of the Model 2425 power delivery system. The offline switching power supply provides all power for the instrument while providing universal inputs and power factor correction for the 120/240V line. The digital board runs off of 5V and 12V supplies derived from the switcher.

  • Page 74: Output Stage

    Output stage Figure 4-4 shows a simplified schematic of the output stage. The Model 2425 output stage serves two purposes: (1) it converts signals from floating common 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 possi- bility of thermal runaway with high-current output values.

  • Page 75: Figure 4-4 Output Stage Simplified Schematic

    4-10 Troubleshooting Model 2425 Service Manual Figure 4-4 Output stage simplified schematic +85V Q500 HI Drive +42V Q504 Q514 Q516 +15Vf Q518 Maindrive 300K Q521 -15Vf Q523 Q525 Q507 -42V Q503 HI Drive -85V...

  • Page 76: A/D Converter

    Active guard The Model 2425 has an active guard or “six-wire ohms” circuit used to measure complex devices. This circuitry provides a low-current (50mA) equivalent of the voltage on output HI. If the unit is in the SV mode, the low-current equivalent of the source voltage will appear on the guard terminal.

  • Page 77: Display Board Circuit Theory

    4-12 Troubleshooting Model 2425 Service Manual Figure 4-5 Digital circuitry block diagram U15, U16 U12, U14 Serial RS-232 Interface Reset Interface E PROM Microprocessor GPIB IEEE-488 U6, U13 Interface A/D Interface Control/Data U9, U25 To Display Board Controller 16.78MHz Voltage Source...

  • Page 78: Troubleshooting

    Model 2425 Service Manual Troubleshooting 4-13 sent back to the digital board through the RXB line via PD1. The 4MHz clock for the microcontroller is generated on the digital board. DS901 is the VFD (vacuum fluorescent display) module, which can display up to 49 char- acters.

  • Page 79: Power Supply Checks

    4-14 Troubleshooting Model 2425 Service Manual Power supply checks Power supply problems can be checked 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.

  • Page 80: Digital Circuitry Checks

    Model 2425 Service Manual Troubleshooting 4-15 Digital circuitry checks Digital circuit problems can be checked out using Table 4-3. See “Principles of operation” for a digital circuit description. Table 4-3 Digital circuitry checks Step Item/component Required condition Remarks Power-on test RAM OK, ROM OK.

  • Page 81: Analog Circuitry Checks

    Disconnect the instrument from the power line and all other equip- ment before changing the battery. The volatile memories of the Model 2425 are protected by a replaceable battery when power is off. Typical battery life is approximately 10 years. The battery should be sus- pected if the instrument no longer retains buffer data or user-defined operating parameters such as instrument setups, source memory, and math expressions.

  • Page 82: Battery Replacement Precautions

    Model 2425 Service Manual Troubleshooting 4-17 Battery replacement precautions WARNING The following precautions 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.

  • Page 83: No Comm Link Error

    4-18 Troubleshooting Model 2425 Service Manual No comm link error A “No Comm Link” error indicates that the front panel processor has stopped communi- cating with the main processor, which is located on the digital board. This error indicates that one of the main processor ROMs may require re-seating in its socket. ROMs may be...

  • Page 84: Disassembly

    Disassembly...

  • Page 85: Introduction

    Disassembly Model 2425 Service Manual Introduction This section explains how to handle, clean, and disassemble the Model 2425. 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 86: Static Sensitive Devices

    Use the assembly drawings located at the end of this section to assist you as you disassem- ble and re-assemble the Model 2425. Also, refer to these drawings for information about the Keithley part numbers of most mechanical parts in the unit. Assembly drawings include: •...

  • Page 87: Case Cover Removal

    Disassembly Model 2425 Service Manual 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.

  • Page 88: Analog Board Removal

    Model 2425 Service Manual Disassembly Analog board removal Perform the following steps to remove the analog board. This procedure assumes that the case cover is already removed. Remove the small pulse board before removing the analog board. Disconnect the front and rear input terminals.

  • Page 89: Digital Board Removal

    Disassembly Model 2425 Service Manual Remove analog board assembly. After all screws have been removed, carefully lift the analog board assembly free of the main chassis. Disassemble analog board assembly. • Remove the screws that secure the analog board and heat sink to the analog board subchassis.

  • Page 90: Front Panel Disassembly

    Model 2425 Service Manual 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 front panel assembly. This assembly has four retaining clips that snap onto the chassis over four pem nut studs.

  • Page 91: Instrument Re-Assembly

    Disassembly Model 2425 Service Manual Instrument re-assembly WARNING To ensure continued protection against electrical shock, verify that power line ground (green and yellow wire attached to the power mod- ule) is connected to the chassis. Also make sure the two bottom case screws are properly installed to secure and ground the case cover to the chassis.

  • Page 92: Replacement Parts

    Replacement Parts...

  • Page 93: Introduction

    Model 2425. Parts lists The electrical parts lists for the Model 2425 are shown in tables at the end of this section. For part numbers to the various mechanical parts and assemblies, use the Miscellaneous parts list and the assembly drawings provided at the end of Section 5.

  • Page 94: Table 6-1 Analog Board Parts List

    Model 2425 Service Manual Replacement Parts Table 6-1 Analog board parts list Keithley Circuit designation Description part no. C200-C203,C205,C210,C225,C226,C231, CAP, .1UF, 10%, 25V, CERAMIC C-495-.1 C232 C204,C411,C608,C609 CAP, .01UF, 10%, 50V, CERAMIC C-491-.01 C211,C212,C213,C214,C301,C302 CAP, 1000PF, 10%, 50V, MONO C-452-1000P...
  • Page 95 Replacement Parts Model 2425 Service Manual Table 6-1 (cont.) Analog board parts list Keithley Circuit designation Description part no. C522,C523,C526,C527 CAP, 3300P, 10%, 500V, CERAMIC C-497-3300P C525,C542,C549,C561,C564,C585 CAP, .1UF, 10%, 25V, CERAMIC C-495-.1 C528,C533,C567,C568,C569,C570,C663, CAP, 3300P, 10%, 500V, CERAMIC C-497-3300P...
  • Page 96 Model 2425 Service Manual Replacement Parts Table 6-1 (cont.) Analog board parts list Keithley Circuit designation Description part no. J1028 CONNECTOR, HEADER CS-368-14 STRAIGHT SOLDER PIN J1029 CONN, MALE, 5-PIN (MOLEX CS-784-5 42491) J1034,J1037,J1038 LATCHING HEADER, FRICTON, CS-724-3 SGL ROW K200-K205 N.C RELAY, 1 FORMB, AQV214...
  • Page 97 Replacement Parts Model 2425 Service Manual Table 6-1 (cont.) Analog board parts list Keithley Circuit designation Description part no. Q402,Q409,Q259 TRANS, N-CHAN DMOS FET, TG-261 TN2504N8 Q403,Q406,Q407,Q408 TRANS, N-CHAN JFET, SST109 TG-266 Q412,Q414 TRANS, N-MEGAFET, TG-267 RFD14N05LSM Q415,Q416 TRANS, HEXFET POWER...
  • Page 98 Model 2425 Service Manual Replacement Parts Table 6-1 (cont.) Analog board parts list Keithley Circuit designation Description part no. R208,R210 RES, 768, 1%, 100MW, THICK FILM R-418-768 R209,R268,R269,R270,R271 RES, 1M, 1%, 100MW, THICK FILM R-418-1M R213 RES NET 5K, .1%, 668A...
  • Page 99 Replacement Parts Model 2425 Service Manual Table 6-1 (cont.) Analog board parts list Keithley Circuit designation Description part no. R308,R379-R387,R391,R392 RES, 475, 1%, 100MW, THICK FILM R-418-475 R313,R314,R315,R316,R317,R334,R335, RES, 4.99K, 1%, 100MW, THICK R-418-4.99K R337 FILM R318,R563 RES, 15K, 1%, 100MW, THICK FILM...
  • Page 100 Model 2425 Service Manual Replacement Parts Table 6-1 (cont.) Analog board parts list Keithley Circuit designation Description part no. R457,R461,R463,R473,R479,R697,R698 RES, 30.1K, 1%, 100MW, THICK R-418-30.1K FILM R475 RES, 1, 1%, 1/5W, WIRE R-501-1 R478,R481,R489,R502,R510,R558,R675, RES, 1K, 1%, 100MW, THICK FILM...
  • Page 101 6-10 Replacement Parts Model 2425 Service Manual Table 6-1 (cont.) Analog board parts list R613,R624,R659,R660 RES, 100, 1%, 100MW, THICK FILM R-418-100 Keithley Circuit designation Description part no. R618 RES, 34K, 1%, 100MW, THICK FILM R-418-34K R619 RES, 4.75K, 1%, 100MW, THICK R-418-4.75K...
  • Page 102 Model 2425 Service Manual Replacement Parts 6-11 Table 6-1 (cont.) Analog board parts list U201,U238 IC, CMOS ANA SWITCH SPST IC-909 MAX326CSE U202,U203,U650 IC, OP AMP LT1112 IC-1048 U204,U229 IC, 8-CHAN ANA MULTIPLEXER, IC-844 DG408DY Keithley Circuit designation Description part no.
  • Page 103 6-12 Replacement Parts Model 2425 Service Manual Table 6-1 (cont.) Analog board parts list U503 IC, +5V VOLTAGE REGULATOR, IC-576 LM2940CT U504 IC, POS VOLTAGE REG +15V, IC-194 500MA, 78M15 Keithley Circuit designation Description part no. U505 IC, NEG VOLTAGE REG -15V,...

  • Page 104: Table 6-2 Digital Board Parts List

    Model 2425 Service Manual Replacement Parts 6-13 Table 6-2 Digital board parts list Keithley part Circuit designation Description C1,C3,C77,C11,C14,C16,C17,C20,C22, CAP, .1UF, 10%, 25V, CERAMIC C-495-.1 C103 CAP, 100UF, 20%, 10V, ALUM C-483-100 ELEC C104 CAP, 10UF, 20%, 63V, ALUM ELEC...
  • Page 105 6-14 Replacement Parts Model 2425 Service Manual Table 6-2 (cont.) Digital board parts list C57,C58,C38,C48 CAP, 1000PF,10%, 50V, MONO C-452-1000P CERAMIC Keithley Circuit designation Description part no. C62,C91 CAP, 10UF,20%, 25V, TANTALUM C-440-10 CAP, .022UF, 10%, 50V, CERAMIC C-491-.022 C72,C86...
  • Page 106 Model 2425 Service Manual Replacement Parts 6-15 Table 6-2 (cont.) Digital board parts list FERRITE CHIP, 600 OHM, CH-62 BLM32A07 Keithley Circuit designation Description part no. COMBINATION LINE FILTER CH-81 CHOKE L4,L5,L6,L7 INDUCTOR CH-89-1 BEEPER, 5V, 30MA, QMX-05 EM-6 P1027,P1033...
  • Page 107 6-16 Replacement Parts Model 2425 Service Manual Table 6-2 (cont.) Digital board parts list R116 RES, 4.99K, 1%, 100MW, THICK R-418-4.99K FILM Keithley Circuit designation Description part no. R118 RES, 49.9K, 1%, 100MW, THICK R-418-49.9K FILM R121 RES, 215, 1%, 100MW, THICK FILM...
  • Page 108 Model 2425 Service Manual Replacement Parts 6-17 Table 6-2 (cont.) Digital board parts list R77,R205,R211 RES, 15k, 1%, 100MW, THICK FILM R-418-15K R8,R155,R119,R200 RES, 1K, 1%, 100MW, THICK FILM R-418-1K Keithley Circuit designation Description part no. RES, 499, 1%, 100MW, THICK FILM...
  • Page 109 6-18 Replacement Parts Model 2425 Service Manual Table 6-2 (cont.) Digital board parts list U22,U1 IC, DUAL D-TYPE F/F, 74HC74 IC-773 U23,U25,U29 IC, POS NAND GATES/INVERT, IC-656 74HCT14 Keithley Circuit designation Description part no. IC, TRIPLE 3 IN NAND, 74F10...

  • Page 110: Table 6-3 Display Board Parts List

    Model 2425 Service Manual Replacement Parts 6-19 Table 6-3 Display board parts list Keithley Circuit Designation Description part no. C901 CAP, 22UF, 20%, 6.3 TANTALUM C-417-22 C902,C904,C907,C908, C910 CAP, .1UF, 20%,100V, CERAMIC C-436-.1 C903,C905,C906,C909, C911 CAP, .1UF, 20%, 50V, CERAMIC C-418-.1...
  • Page 111 6-20 Replacement Parts Model 2425 Service Manual Table 6-3 Display board parts list * Order current firmware revision, for example 7001-800A01.

  • Page 112: Table 6-4 Mechanical Parts List

    Model 2425 Service Manual Replacement Parts 6-21 Table 6-4 Mechanical parts list Qty. Description Keithley part no. 5X20MM SLO-BLO FUSE FU-106-3.15 BANANA JACK, PUSH-IN BLACK BJ-14-0 BANANA JACK, PUSH-IN BLUE BJ-14-6 BANANA JACK, PUSH-IN RED BJ-14-2 BANANA JACK, PUSH-IN WHITE...
  • Page 113 6-22 Replacement Parts Model 2425 Service Manual...

  • Page 114: Specifications

    Specifications...

  • Page 115: Accuracy Calculations

    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 116: Command Reference

    Command Reference...

  • Page 117: Introduction

    Command Reference Model 2425 Service Manual Introduction This appendix contains detailed information on the various Model 2425 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.

  • Page 118: Miscellaneous Commands

    Example Send default code of KI002425. :CAL:PROT:CODE 'KI002425' :COUNT? (:CALibration:PROTected:COUNT?) Purpose To request the number of times the Model 2425 has been calibrated. Format :cal:prot:count? Response Number of times calibrated. Description The :COUNT? query may be used to determine the total number of times the Model 2425 has been calibrated.
  • Page 119 Command Reference Model 2425 Service Manual :LOCK (:CALibration:PROTected:LOCK) Purpose To lock out calibration. Format :cal:prot:lock Query :cal:prot:lock? Response 0 Calibration unlocked 1 Calibration locked Description The :LOCK command allows you to lock out comprehensive calibration after completing those procedures. Thus, :LOCK performs the opposite of sending the password with the :CODE command.
  • Page 120 Model 2425 Service Manual Command Reference :DATE (:CALibration:PROTected:DATE) Purpose To program the calibration date. Format :cal:prot:date <year>, <month>, <day> Parameters <year> = 1994 to 9999 <month> = 1 to 12 <day> = 1 to 31 Query :cal:prot:date? Response <year> , <month> , <day>...
  • Page 121 Table B-2. Note When the Model 2425 receives this command, it will attempt to place the parameter into one of three parameter ranges summarized in Table B-2, depending on the active :SENS:FUNC and range. If the parameter does not fit into any of the three allowed ranges, an error number -222, “Parameter data...

  • Page 122: Table B-2 Recommended :Calibration:protected:sense Parameter Ranges

    :CAL:PROT:SOUR command for each parameter listed in Table B-3. Note When the Model 2425 receives this command, it will attempt to place the parameter into one of the four parameter ranges summarized in Table B-3, depending on the active :SOUR:FUNC and range. If the parameter does not fit into any of the four allowed ranges, an error number -222, “Parameter data...

  • Page 123: Table B-3 Recommended :Calibration:protected:source Parameter Ranges

    Because the source is calibrated for both positive and negative values, two zero calibration points are required. The Model 2425 automatically uses the appropriate zero parameter based on whether the source polarity is positive or negative.

  • Page 124: Detecting Calibration Errors

    Several methods to detect calibration errors are discussed below. Reading the error queue As with other Model 2425 errors, any calibration errors will be reported in the error queue. (You can read the error queue by using the :SYST:ERR? query.) Error summary Table B-4 summarizes calibration errors.

  • Page 125: Status Byte Eav (Error Available) Bit

    DAC setting. All of the source/compliance DAC calibration constants are verified each time a :CAL:PROT:SOUR command is processed and when the Model 2425 is first turned on. This error generally occurs when the Model 2425 source circuitry is defective.

  • Page 126: Generating An Srq On Error

    Model 2425 Service Manual Command Reference B-11 Generating an SRQ on error To program the instrument to generate an IEEE-488 bus SRQ (Service Request) when an error occurs, send the following command: *SRE 4. This command will enable SRQ when the EAV bit is set.

  • Page 127: 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 2425. 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.

  • Page 128: Calibration Programs

    Calibration Programs...

  • Page 129: Introduction

    This appendix includes a calibration program written in BASIC to help you calibrate the Model 2425, as well as an example program that demonstrates how to request calibration constants. Refer to Section 2 for more details on calibration procedures, equipment, and connections.

  • Page 130: General Program Instructions

    Model 2425 and the multimeter to warm up for at least one hour before performing calibration. Make sure the Model 2425 is set for a primary address of 24. (Use the front panel MENU/GPIB selection to check or change the address.) Ensure the digital multimeter primary address is set to its factory default setting (22).

  • Page 131: Program C-1 Model 2425 Calibration Program

    Model 2425 Service Manual Program C-1 Model 2425 calibration program Model 2425 calibration program for use with the HP3458A Digital Multimeter. ' Rev. 1.0, 7/1/00 ' 2425 primary address = 24. HP3458A primary address = 22. OPEN "IEEE" FOR OUTPUT AS #1 ' Open IEEE-488 output path.
  • Page 132 IF J = 2 AND Range > 9 AND Range < 11 THEN Range = 3 PRINT #1, "OUTPUT 24;:OUTP:STAT OFF" PRINT #1, "OUTPUT 22;FUNC DCV,AUTO" PRINT "Connect 1 Ohm resistor and DMM volts input to 2425." GOSUB KeyCheck PRINT #1, "OUTPUT 24;:OUTP:STAT ON" END IF...
  • Page 133 Calibration Programs Model 2425 Service Manual INPUT #2, S PRINT #1, "SPOLL 24" ' Clear SRQ. 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 <>...

  • Page 134: Requesting Calibration Constants

    Requesting calibration constants Program C-2 listed below demonstrates how to request the calibration constants from the Model 2425. 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 135 Calibration Programs Model 2425 Service Manual ' Loop for all current ranges. PRINT #1, "OUTPUT 24;:SOUR:CURR:RANGE "; Range PRINT #1, "OUTPUT 24;:CAL:PROT:SENS:DATA?" PRINT #1, "ENTER 24" LINE INPUT #2, Data$ PRINT Data$ PRINT #1, "OUTPUT 24;:CAL:PROT:SOUR:DATA?" PRINT #1, "ENTER 24"...
  • Page 136 Index Calibration Considerations 2-3 Symbols Cycle 2-3 Equipment 2-4, C-2 10μA to 1A range accuracy 1-16 Errors 2-8, B-9 1Ω resistor characterization 1-5, 2-4 Parameters 2-19 3A range current calibration test Remote 2-18 connections 2-15 Remote command summary 2-18 :CALibration:PROTected:CODE B-3 Remote calibration command :CALibration:PROTected:COUNT? B-3 summary B-2...
  • Page 137 Current measurement Error reporting 2-8 Accuracy 1-11 Tests 4-3 Accuracy limits 1-12 Voltage calibration 2-10 Current range calibration commands 2-25 General program instructions C-3 Generating an SRQ on calibration Detecting calibration complete B-12 Errors B-9 Generating an SRQ on error B-11 Step completion B-11 Determining compliance limit 1-8 Digital...

  • Page 138: Program C-2 Requesting Calibration Constants

    Ohms measurement accuracy limits 1-19 Setting the measurement range 1-8 Ordering information 6-2 Setting the source range and output Output value 1-7 Current accuracy 1-16 Single-range calibration 2-26 Current accuracy limits 1-17 Software requirements C-2 Stage 4-9 Solder repairs 5-2 Stage simplified schematic 4-10 Source accuracy A-6 Voltage accuracy 1-11...
  • Page 140 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. _________________________ __________________________________________________________________________________________ __________________________________________________________________________________________ q Intermittent q Analog output follows display q Particular range or function bad;...

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