Keithley 2425 Service Manual

Model 2425100W SourceMeter

®

Service Manual

A GREATER MEASURE OF CONFIDENCE

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.

During the warranty period, we will, at our option, either repair or replace any product that proves to be defective.

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 instruc­tions.

THIS WARRANTY IS IN LIEU OF ALL OTHER WARRANTIES, EXPRESSED OR IMPLIED, INCLUD­ING ANY IMPLIED WARRANTY 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
DAMAGES SHALL INCLUDE, BUT ARE NOT LIMITED TO: COSTS OF REMOVAL AND INSTALLA
TION, LOSSES SUSTAINED AS THE RESULT OF INJURY TO ANY PERSON, OR DAMAGE TO PROP­ERTY.

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Keithley Instruments, Inc. 28775 Aurora Road • Cleveland, Ohio 44139 • 440-248-0400 • Fax: [phone]

Sales Offices: BELGIUM: Bergensesteenweg 709 • B-1600 Sint-Pieters-Leeuw • 02-363 00 40 • Fax: [phone]

2892

CHINA: Yuan Chen Xin Building, Room 705 • 12 Yumin Road, Dewai, Madian • Beijing 100029 • 8610-6202-2886 • Fax: [phone]-

FINLAND: Tietäjäntie 2 • 02130 Espoo • Phone: [phone] • Fax: [phone]
FRANCE: 3, allée des Garays • 91127 Palaiseau Cédex • 01-64 53 20 20 • Fax: [phone]
GERMANY: Landsberger Strasse 65 • 82110 Germering • 089/84 93 07-40 • Fax: [phone]
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INDIA: Flat 2B, Willocrissa • 14, Rest House Crescent • Bangalore 560 001 • 91-80-509-1320/21 • Fax: [phone]
ITALY: Viale San Gimignano, 38 • 20146 Milano • 02-48 39 16 01 • Fax: [phone]
JAPAN: New Pier Takeshiba North Tower 13F • 11-1, Kaigan 1-chome • Minato-ku, Tokyo 105-0022 • 81-3-5733-7555 • Fax: [phone]
KOREA: 2FL., URI Building • 2-14 Yangjae-Dong • Seocho-Gu, Seoul 137-888 • 82-2-574-7778 • Fax: [phone]
NETHERLANDS: Postbus 559 • 4200 AN Gorinchem • 0183-635333 • Fax: [phone]
SWEDEN: c/o Regus Business Centre • Frosundaviks Allé 15, 4tr • 169 70 Solna • 08-509 04 679 • Fax: [phone]
SWITZERLAND: Kriesbachstrasse 4 • 8600 Dübendorf • 01-821 94 44 • Fax: [phone]

1-888-KEITHLEY (534-8453) • www.keithley.com

TAIWAN: 1FL., 85 Po Ai Street • Hsinchu, Taiwan, R.O.C. • 886-3-572-9077• Fax: [phone]

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

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 in­formation 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 Revi
sion 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 2425-902-01)............................................................. August 2000

Revision B (Document Number 2425-902-01) ............................................................October 2004

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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.

Safety Precautions

The following safety precautions should be observed before using this product and any associated instrumentation. 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 and follow all installation, operation, and maintenance information carefully before us­ing the product. Refer to the manual for complete product specifications.

If the product is used in a manner not specified, the protection provided by the product may be impaired.

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 properly, 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 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 products. Only properly
trained service personnel may perform installation and service procedures.

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. Measurement Category II connections require protection for high transient over-voltages often as
sociated with local AC mains connections. 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 connector jacks or test fixtures.
The American National Standards Institute (ANSI) states that a shock hazard 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.

Operators of this product must be protected from electric shock at all times. The responsible body must ensure that operators
are prevented access and/or insulated from every connection point. In some cases, connections must be exposed to potential
human contact. Product operators 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 receptacle. Inspect the con­necting cables, test leads, and jumpers for possible wear, cracks, or breaks before 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 ca

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5/03

bles or jumpers, installing or removing switching cards, 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 capable 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.

If a screw is present, connect it to safety earth ground using the wire recommended in the user documentation.

The ! symbol on an instrument indicates that the user should refer to the operating instructions located in the manual.

The symbol on an instrument shows that it can source or measure 1000 volts or more, including the combined effect of
normal and common mode voltages. Use standard safety precautions to avoid personal contact with these voltages.

The symbol indicates a connection terminal to the equipment frame.

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 accuracy 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 the instrument. Products 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 contaminated and operation is affected, the board should be returned to the factory for
proper cleaning/servicing.

Table of Contents

1 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 ............................................... 1-5

Restoring factory defaults .......................................................... 1-6

Performing the verification test procedures ............................... 1-6

Test summary ...................................................................... 1-6

Test considerations ............................................................. 1-6

Setting the source range and output value .......................... 1-7

Setting the measurement range ........................................... 1-8

Compliance considerations ........................................................ 1-8

Compliance limits ............................................................... 1-8

Types of compliance ........................................................... 1-8

Maximum compliance values ............................................. 1-9

Determining compliance limit ............................................ 1-9

Taking the SourceMeter out of compliance ...................... 1-10

Output voltage accuracy ........................................................... 1-10

Voltage measurement accuracy ............................................... 1-11

Output current accuracy ........................................................... 1-13

Current measurement accuracy ................................................ 1-16

Resistance measurement accuracy ........................................... 1-18

2 Calibration

Introduction ................................................................................ 2-2

Environmental conditions .......................................................... 2-2

Temperature and relative humidity ..................................... 2-2

Warm-up period .................................................................. 2-2

Line power .......................................................................... 2-2

Calibration considerations .......................................................... 2-3

Calibration cycle ................................................................. 2-3

Recommended calibration equipment ................................ 2-4

1Ω resistor characterization ................................................ 2-4

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 ........................ 2-8

Calibration errors ........................................................................ 2-8

Front panel error reporting .................................................. 2-8

Remote error reporting ........................................................ 2-9

Front panel calibration ................................................................ 2-9

Remote calibration .................................................................... 2-18

Remote calibration commands .......................................... 2-18

Recommended calibration parameters .............................. 2-19

Remote calibration procedure ........................................... 2-20

Single-range calibration ............................................................ 2-26

3 Routine Maintenance

Introduction ................................................................................ 3-2

Line fuse replacement ................................................................. 3-2

4 Troubleshooting

Introduction ................................................................................ 4-2

Safety considerations .................................................................. 4-2

Repair considerations ................................................................. 4-2

Power-on self-test ....................................................................... 4-3

Front panel tests .......................................................................... 4-3

KEYS test ............................................................................ 4-3

DISPLAY PATTERNS test ................................................ 4-4

CHAR SET test ................................................................... 4-4

Principles of operation ................................................................ 4-5

Overall block diagram ......................................................... 4-5

Analog circuits .................................................................... 4-7

Power supply ....................................................................... 4-8

Output stage ......................................................................... 4-9

A/D converter .................................................................... 4-11

Active guard ...................................................................... 4-11

Digital circuitry ................................................................. 4-11

Display board circuit theory .............................................. 4-12

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

5 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 .................................................................... 5-4

Analog board removal ................................................................ 5-5

Digital board removal ................................................................ 5-6

Front panel disassembly ............................................................. 5-7

Removing power components .................................................... 5-7

Power module removal ....................................................... 5-7

Instrument re-assembly .............................................................. 5-8

6 Replacement Parts

Introduction ................................................................................ 6-2

Parts lists .................................................................................... 6-2

Ordering information ................................................................. 6-2

Factory service ........................................................................... 6-2

Component layouts .................................................................... 6-2

A Specifications

Accuracy calculations ............................................................... A-6

Measurement accuracy ...................................................... A-6

Source accuracy ................................................................. A-6

B Command Reference

Introduction ............................................................................... B-2

Command summary ................................................................... B-2

Miscellaneous commands .......................................................... B-3

Detecting calibration errors ....................................................... B-9

Reading the error queue ..................................................... B-9

Error summary .................................................................... B-9

Status byte EAV (Error Available) bit ............................. B-10

Generating an SRQ on error ............................................. B-11

Detecting calibration step completion ..................................... B-11

Using the *OPC? query .................................................... B-11

Using the *OPC command ............................................... B-11

Generating an SRQ on calibration complete .................... B-12

C Calibration Programs

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

List of Illustrations

1 Performance Verification

Figure 1-1 Connections for voltage verification tests ........................... 1-10

Figure 1-2 Connections for 10µA to 1A range

Figure 1-3 Connections for 3A range current verification tests ............ 1-14

Figure 1-4 Connections for resistance accuracy verification ................ 1-18

2 Calibration

Figure 2-1 Voltage calibration test connections .................................... 2-10

Figure 2-2 10µA to 1A range current calibration test connections ....... 2-13

Figure 2-3 3A range current calibration test connections ..................... 2-15

3 Routine Maintenance

Figure 3-1 Rear panel .............................................................................. 3-2

4 Troubleshooting

Figure 4-1 Overall block diagram ........................................................... 4-6

Figure 4-2 Analog circuitry block diagram ............................................. 4-7

Figure 4-3 Power supply block diagram ................................................. 4-8

Figure 4-4 Output stage simplified schematic ....................................... 4-10

Figure 4-5 Digital circuitry block diagram ............................................ 4-12

current verification tests .............................................. 1-13

List of Tables

1 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 .................................. 1-17

Table 1-7 Ohms measurement accuracy limits ..................................... 1-19

2 Calibration

Table 2-1 Recommended calibration equipment .................................... 2-4

Table 2-2 Calibration unlocked states .................................................... 2-6

Table 2-3 Front panel voltage calibration ............................................. 2-12

Table 2-4 Front panel current calibration ............................................. 2-16

Table 2-5 Remote calibration command summary ............................... 2-18

Table 2-6 Recommended :CALibration:PROTected:SENse

Table 2-7 Recommended :CALibration:PROTected:SOURce

Table 2-8 Voltage calibration initialization commands ....................... 2-22

Table 2-9 Voltage range calibration commands ................................... 2-23

Table 2-10 Current calibration initialization commands ........................ 2-24

Table 2-11 Current range calibration commands ................................... 2-25

parameter ranges .......................................................... 2-19

parameter ranges .......................................................... 2-20

3 Routine Maintenance

Table 3-1 Power line fuse ....................................................................... 3-3

4 Troubleshooting

Table 4-1 Display board checks ........................................................... 4-13

Table 4-2 Power supply checks ............................................................ 4-14

Table 4-3 Digital circuitry checks ........................................................ 4-15

Table 4-4 Analog circuitry checks ........................................................ 4-16

6 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

B Command Reference

Table B-1 Remote calibration command summary ............................... B-2

Table B-2 Recommended :CALibration:PROTected:SENSe

parameter ranges .......................................................... B-7

Table B-3 Recommended :CALibration:PROTected:SOURce

parameter ranges .......................................................... B-8

Table B-4 Calibration errors ................................................................ B-10

1

Performance Verification

1-2 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.

• To verify that the unit meets factory specifications.

• To determine if calibration is required.

• Following calibration to make sure it was performed properly.

WARNING The information in this section is intended for qualified service per-

sonnel only. Do not attempt these procedures unless you are qualified
to do so. Some of these procedures may expose you to hazardous volt
ages, which could cause personal injury or death if contacted. Use
standard safety precautions when working with hazardous voltages.

NOTE If the 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.

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Verification test requirements

Be sure that you perform the verification tests:

• Under the proper environmental conditions.

• After the specified warm-up period.

• Using the correct line voltage.

• Using the proper test equipment.

• Using the specified output signals and reading limits.

Model 2425 Service Manual Performance Verification 1-3

Environmental conditions

Conduct your performance verification procedures in a test environment with:

• An ambient temperature of 18 to 28°C (65 to 82°F).

• A relative humidity of less than 70% unless otherwise noted.

Warm-up period

Allow the Model 2425 to warm up for at least one hour 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 manu­facturer.

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.

1-4 Performance Verification Model 2425 Service Manual

Recommended test equipment

Table 1-1 summarizes recommended verification equipment. You can use alternate equip­ment as long as that equipment has specifications comparable to those listed in Table 1-1.
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).

Table 1-1

Recommended verification equipment

Description Manufacturer/Model Specifications

Digital Multimeter Hewlett Packard

HP3458A

Resistance Calibrator Fluke 5450A Resistance

Precision Resistor

1

90-day, full-range accuracy specifications of ranges required for various measurement points.

2

90-day, ±5°C specifications of nominal resistance values shown. Use actual values for tests. Maximum uncertainty of alternate test
equipment shown in parentheses.

3

Required for verification of 3A current range. Characterize resistor to ±300ppm or better using recommended DMM before ver-

ifying 3A current measurement range.

3

Isotec RUG-Z-1R00-0.1 1Ω, ±0.1%, 100W

DC Voltage11V:

10V:
100V:

DC Current210μA:

100μA:
1mA:
10mA:
100mA:
1A:

2

1.9Ω:
19Ω:
190Ω:

1.9kΩ:
19kΩ:
190kΩ:

1.9MΩ:
19MΩ:

±5.6ppm
±4.3ppm
±6.3ppm

±25ppm
±23ppm
±20ppm
±20ppm
±35ppm
±110ppm

±65ppm (±460ppm)
±23ppm (±280ppm)
±10.5ppm (±230ppm)
±8ppm (±200ppm)
±7.5ppm (±195ppm)
±8.5ppm (±200ppm)
±11.5ppm (±180ppm)
±30ppm (±635ppm)

Model 2425 Service Manual Performance Verification 1-5

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. Then use that measured value
to calculate the current during the 3A current measurement range test procedure.

Verification limits

The verification limits stated in this section have been calculated using only the Model
2425 one-year accuracy specifications, and they do not include test equipment uncer
tainty. If a particular measurement falls outside the allowable range, recalculate new limits
based on Model 2425 specifications and corresponding test equipment specifications.

Example limits calculation

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:

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Output limits = 20V ± [(20V × 0.02%) + 2.4mV]
Output limits = 20V ± (0.004 + 0.0024)
Output limits = 20V ± 0.0064V
Output limits = 19.9936V to 20.0064V

Resistance limits calculation

When verifying the resistance measurement accuracy, it will probably be necessary to
recalculate resistance limits based on the actual calibrator resistance values. You can cal
culate resistance reading limits in the same manner described above, but be sure to use the
actual calibrator resistance values and the Model 2425 normal accuracy specifications for
your calculations.

As an example, assume you are testing the 20kΩ range, and that the actual value of the
nominal 19kΩ calibrator resistor is 19.01kΩ. Using the Model 2425 20kΩ range one-year
normal accuracy specifications of ±(0.063% of reading + 3Ω), the recalculated reading
limits are:

Reading limits = 19.01kΩ ± [(19.01kΩ × 0.063%) + 3Ω]
Reading limits = 19.01kΩ ±15Ω
Reading limits = 18.9950kΩ to 19.0250kΩ

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1-6 Performance Verification Model 2425 Service Manual

Restoring factory defaults

Before performing the verification procedures, restore the instrument to its factory front
panel (bench) defaults as follows:

1. Press the MENU key. The instrument will display the following prompt:

MAIN MENU

SAVESETUP COMMUNICATION CAL

2. Select SAVESETUP, then press ENTER. The unit then displays:

SAVESETUP MENU

GLOBAL SOURCE-MEMORY

3. Select GLOBAL, then press ENTER. The unit then displays:

GLOBAL SETUP MENU

SAVE RESTORE POWERON RESET

4. Select RESET, then press ENTER. The unit displays:

RESET ORIGINAL DFLTS

BENCH GPIB

5. Select BENCH, then press ENTER to restore bench defaults.

©

Performing the verification test procedures

Test summary

• DC voltage output accuracy

• DC voltage measurement accuracy

• DC current output accuracy

• 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:

• 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 2425 INPUT/OUTPUT jacks. Also be sure that the front panel jacks are
selected with the TERMINALS key.

• Make sure the Model 2425 is set to the correct source range (see below).

• Ensure that the Model 2425 output is turned on before making measurements.

Model 2425 Service Manual Performance Verification 1-7

• Ensure the test equipment is set up for the proper function and range.

• 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. Exceeding this value may cause a breakdown
in insulation, creating a shock hazard.

CAUTION The maximum voltage between INPUT/OUTPUT HI and LO or

4-WIRE SENSE HI and LO is 125V peak. The maximum voltage
between INPUT/OUTPUT HI and 4-WIRE SENSE HI or between
INPUT/OUTPUT LO and 4-WIRE SENSE LO is 5V. Exceeding these
voltage values may result in instrument damage.

Setting the source range and output value

Before testing each verification point, you must properly set the source range and output
value as outlined below.

1. Press either the SOURCE V or SOURCE I key to select the appropriate source function.

2. Press the EDIT key as required to select the source display field. Note that the cur­sor will flash in the source field while its value is being edited.

3. With the cursor in the source display field flashing, set the source range to the low­est possible range for the value to be sourced using the up or down RANGE key.
For example, you should use the 20V source range to output a 20V source value.
With a 20V source value and the 20V range selected, the source field display will
appear as follows:

Vsrc: +20.0000 V

4. With the source field cursor flashing, set the source output to the required value using either:

• The SOURCE adjustment and left and right arrow keys.

• The numeric keys.

5. Note that the source output value will be updated immediately; you need not press
ENTER when setting the source value.

1-8 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.

Compliance considerations

Compliance limits

When sourcing voltage, you can set the SourceMeter to limit current from 10nA to 3.15A.
Conversely, when sourcing current, you can set the SourceMeter to limit voltage from

0.2mV to 105V. The SourceMeter output will not exceed the programmed compliance
limit.

Types of compliance

There are two types of compliance that can occur: “real” and “range.” Depending on
which value is lower, the output will clamp at either the displayed compliance setting
(“real”) or at the maximum measurement range reading (“range”).

The “real” compliance condition can occur when the compliance setting is less than the
highest possible reading of the measurement range. When in compliance, the source out
put clamps at the displayed compliance value. For example, if the compliance voltage is
set to 1V and the measurement range is 2V, the output voltage will clamp (limit) at 1V.

“Range” compliance can occur when the compliance setting is higher than the possible
reading of the selected measurement range. When in compliance, the source output
clamps at the maximum measurement range reading (not the compliance value). For
example, if the compliance voltage is set to 1V and the measurement range is 200mV, the
output voltage will clamp (limit) at 210mV.

-

Model 2425 Service Manual Performance Verification 1-9

Maximum compliance values

The maximum compliance values for the measurement ranges are summarized in
Table 1-2.

Table 1-2

Maximum compliance values

Measurement

range

200mV
2V
20V
100V

10μA
100μA
1mA
10mA
100mA
1A
3A

When the SourceMeter goes into compliance, the “Cmpl” label or the units label (i.e.,
“mA”) for the compliance display will flash.

210mV

2.1V
21V
105V

10.5μA
105 μA

1.05mA

10.5mA
105mA

1.05A

3.15A

Determining compliance limit

The relationships to determine which compliance is in effect are summarized as follows.
They assume that the measurement function is the same as the compliance function.

Maximum

compliance value

• Compliance Setting < Measurement Range = Real Compliance

• Measurement Range < Compliance Setting = Range Compliance

You can determine the compliance that is in effect by comparing the displayed compli­ance setting to the present measurement range. If the compliance setting is lower than the
maximum possible reading on the present measurement range, the compliance setting is
the compliance limit. If the compliance setting is higher than the measurement range, the
maximum reading on that measurement range is the compliance limit.

1-10 Performance Verification Model 2425 Service Manual

Taking the SourceMeter out of compliance

Verification measurements should not be made when the SourceMeter is in compliance.
For purposes of the verification tests, the SourceMeter can be taken out of compliance by
going into the edit mode and increasing the compliance limit.

NOTE Do not take the unit out of compliance by decreasing the source value or chang-

ing the range. Always use the recommended range and source settings when
performing the verification tests.

Output voltage accuracy

Follow the steps below to verify that Model 2425 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.

1. With the power off, connect the digital multimeter to the Model 2425 INPUT/ OUTPUT jacks, as shown in Figure 1-1.

2. Select the multimeter DC volts measuring function.

3. Press the Model 2425 SOURCE V key to source voltage, and make sure the source output is turned on.

Figure 1-1

Connections for voltage verification tests

EDIT

DISPLAY

TOGGLE

POWER

V

1

LOCAL

REL

67

DIGITS SPEED

I

MEAS

Ω

230

FILTER

89

RECALL

STORE

FCTN

LIMIT

V

4

TRIG

SWEEP

+/-

CONFIG MENU

I

5

Model 2425

Digital Multimeter

2425 100 W SourceMeter

SOURCE

EDIT

EXIT ENTER

RANGE

AUTO

RANGE

4- WIRE

INPUT/

SENSE

OUTPUT

HI

125V

PEAK

®

ON/OFF

OUTPUT

125V

5V

PEAK

PEAK

LO

250V
PEAK

!

TERMINALS

FRONT/

REAR

Input HI

Input LO

Model 2425 Service Manual Performance Verification 1-11

4. Verify output voltage accuracy for each of the voltages listed in Table 1-3. For each test point:

• Select the correct source range.

• Set the Model 2425 output voltage to the indicated value.

• Verify that the multimeter reading is within the limits given in the table.

5. Repeat the procedure for negative output voltages with the same magnitudes as those listed in Table 1-3.

6. Repeat the entire procedure using the rear panel INPUT/OUTPUT jacks. Be sure to select the rear panel jacks with the front panel TERMINALS key.

Table 1-3

Output voltage accuracy limits

Model 2425

source range

200mV
2V
20V
100V

Model 2425 output

voltage setting

200.000mV

2.00000V

20.0000V

100.000V

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.

1. With the power off, connect the digital multimeter to the Model 2425 INPUT/ OUTPUT jacks, as shown in Figure 1-1.

2. Select the multimeter DC volts function.

3. Set the Model 2425 to both source and measure voltage by pressing the SOURCE V and MEAS V keys, and make sure the source output is turned on.

Output voltage limits

(1 year, 18°C to 28°C)

199.360 to 200.640mV

1.99900 to 2.00100V

19.9936 to 20.0064V

99.968 to 100.032V

-

1-12 Performance Verification Model 2425 Service Manual

4. Verify output voltage accuracy for each of the voltages listed in Table 1-4. For each test point:

• 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.

NOTE It may not be possible to set the voltage source to the specified value. Use the

closest possible setting, and modify reading limits accordingly.

5. Repeat the procedure for negative source voltages with the same magnitudes as those listed in Table 1-4.

6. Repeat the entire procedure using the rear panel INPUT/OUTPUT jacks. Be sure to select the rear panel jacks with the front panel TERMINALS key select the rear panel jacks with the front panel TERMINALS key.

Table 1-4

Voltage measurement accuracy limits

Model 2425 source

1

and measure range

200mV
2V
20V
100V

1

Measure range coupled to source range when simultaneously sourcing and measuring voltage.

2

As measured by multimeter. Use closest possible value and modify reading limits accordingly.

Source voltage

200.000mV

2.00000V

20.0000V

100.000V

2

Model 2425 voltage reading

limits (1 year, 18°C to 28°C)

199.676 to 200.324mV

1.99946 to 2.00054V

19.9960 to 20.0040V

99.982 to 100.018V

Model 2425 Service Manual Performance Verification 1-13

Output current accuracy

Follow the steps below to verify that Model 2425 output current accuracy is within speci­fied limits. The test involves setting the output current to each full-range value and mea­suring the currents with a precision digital multimeter.

10μA to 1A range accuracy

1. With the power off, connect the digital multimeter to the Model 2425 INPUT/ OUTPUT jacks, as shown in Figure 1-2.

Figure 1-2

Connections for 10μA to 1A range current verification tests

4- WIRE

INPUT/

SENSE

OUTPUT

HI

EDIT

DISPLAY

TOGGLE

POWER

V

LOCAL

REL

67

DIGITS SPEED

125V
PEAK

5

SWEEP

SOURCE

I

2425 100 W SourceMeter

EDIT

EXIT ENTER

MEAS

Ω

230

FILTER

89

RECALL

STORE

FCTN

LIMIT

V

4

TRIG

+/-

CONFIG MENU

I

1

RANGE

AUTO

RANGE

®

ON/OFF

OUTPUT

Model 2425

PEAK

5V

LO

TERMINALS

125V
PEAK

250V
PEAK

!

FRONT/

REAR

Input LO

Amps

Digital Multimeter

2. Select the multimeter DC current measuring function.

3. Press the Model 2425 SOURCE I key to source current, and make sure the source output is turned on.

4. 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 2425 output current to the correct value.

• Verify that the multimeter reading is within the limits given in the table.

1-14 Performance Verification Model 2425 Service Manual

5. Repeat the procedure for negative output currents with the same magnitudes as those listed in Table 1-5.

6. Repeat the entire procedure using the rear panel INPUT/OUTPUT jacks. Be sure to select the rear panel jacks with the front panel TERMINALS key.

3A range accuracy

1. 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.

2. Select the multimeter DC volts measuring function.

3. Press the Model 2425 SOURCE I key to source current, and make sure the source output is turned on.

Figure 1-3

Connections for 3A range current verification tests

4- WIRE

INPUT/

SENSE

OUTPUT

HI

EDIT

DISPLAY

TOGGLE

POWER

V

1

LOCAL

REL

67

DIGITS SPEED

I

MEAS

Ω

230

FILTER

89

RECALL

STORE

FCTN

LIMIT

2425 100 W SourceMeter

SOURCE

I

V

4

5

TRIG

SWEEP

+/-

CONFIG MENU

EXIT ENTER

Model 2425

Digital Multimeter

125V
PEAK

®

EDIT

RANGE

AUTO

RANGE

ON/OFF

OUTPUT

PEAK

5V

LO

!

TERMINALS

FRONT/

REAR

PEAK

PEAK

125V

250V

1Ω Resistor

Input HI

Input LO

Model 2425 Service Manual Performance Verification 1-15

4. Verify output current accuracy for the 3A range. Be sure to:

• 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.)

5. Repeat the procedure for a negative 3A current output value.

6. Repeat the entire procedure using the rear panel INPUT/OUTPUT jacks. Be sure to select the rear panel jacks with the front panel TERMINALS key.

Table 1-5

Output current accuracy limits

Model 2425

source range

10mA
100mA
1mA
10mA
100mA
1A

1

3A

1

See separate procedure for 3A range. DMM voltage reading is same as sourced current.

Model 2425

output current setting

10.0000mA

100.000mA

1.00000mA

10.0000mA

100.000mA

1.00000A

3.00000A

Output current limits

(1 year, 18°C to 28°C)

9.9947 to 10.0053mA

99.949 to 100.051mA

0.99946 to 1.00054mA

9.9935 to 10.0065mA

99.914 to 100.086mA

0.99893 to 1.00107A

2.99543 to 3.00457A

1-16 Performance Verification Model 2425 Service Manual

Current measurement accuracy

Follow the steps below to verify that Model 2425 current measurement accuracy is within
specified limits. The procedure involves applying accurate currents from the Model 2425
current source and then verifying that Model 2425 current measurements are within
required limits.

10μA to 1A range accuracy

1. With the power off, connect the digital multimeter to the Model 2425 INPUT/ OUTPUT jacks, as shown in Figure 1-2.

2. Select the multimeter DC current function.

3. Set the Model 2425 to both source and measure current by pressing the SOURCE I and MEAS I keys, and make sure the source output is turned on.

4. Verify measure current accuracy for the 10μA-1A range currents listed in Table
1-6. For each measurement:

• 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.

NOTE It may not be possible to set the current source to the specified value. Use the

closest possible setting, and modify reading limits accordingly.

5. Repeat the procedure for negative calibrator currents with the same magnitudes as those listed in Table 1-6.

6. Repeat the entire procedure using the rear panel INPUT/OUTPUT jacks. Be sure to select the rear panel jacks with the front panel TERMINALS key.

3A range accuracy

NOTE The 1Ω resistor should be characterized to within ±300ppm before verifying the

3A 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.

1. With the power off, connect the 1Ω resistor and digital multimeter to the Model
2425 INPUT/OUTPUT jacks, as shown in Figure 1-3.

2. Select the multimeter DC volts function.

3. Set the Model 2425 to both source and measure current by pressing the SOURCE I and MEAS I keys, and make sure the source output is turned on.

Model 2425 Service Manual Performance Verification 1-17

4. 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 read­ing and characterized 1Ω resistance value as I = V/R, where V is the DMM voltage
reading and R is the characterized resistance value.

• Verify that the Model 2425 current reading is within the 3A limits given in Table 1-

6.

NOTE It may not be possible to set the current source to the specified 3A value. Use the

closest possible setting, and modify reading limits accordingly.

5. Repeat the procedure for a negative 3A current.

6. Repeat the procedure using the rear panel INPUT/OUTPUT jacks. Be sure to select the rear panel jacks with the front panel TERMINALS key.

Table 1-6

Current measurement accuracy limits

Model 2425 source

1

and measure range

10μA
100μA
1mA
10mA
100mA
1A
3A

1

Measure range coupled to source range when simultaneously sourcing and measuring current.

2

As measured by precision digital multimeter. Use closest possible value, and modify reading limits

accordingly if necessary.

3

Current calculated as follows: I = V/R, where V is the DMM voltage reading, and R is the

characterized value of the 1Ω resistor.

Source current

10.00000μA

100.000μA

1.00000mA

10.0000mA

100.000mA

1.00000A

3.00000A

Model 2425 current reading lim-

2

its (1 year, 18°C to 28°C)

9.9966 to 10.0034μA

99.969 to 100.031μA

0.99967 to 1.00033mA

9.9959 to 10.0041mA

99.939 to 100.061mA

0.99928 to 1.00072A

2.99673 to 3.00327A

3

1-18 Performance Verification 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.

CAUTION Before testing the 2Ω and 20Ω ranges, make sure your resistance cali-

brator can safely handle the default test currents for those ranges (see
Model 2425 and calibrator specifications). If not, use the CONFIG
OHMS menu to select the MANUAL source mode, then set the source
current to an appropriate safe value. When using the manual source
mode, total resistance reading uncertainty includes both Source I and
Measure V uncertainty (see specifications), and calculated reading
limits should take the additional uncertainty into account.

1. With the power off, connect the resistance calibrator to the Model 2425 INPUT/ OUTPUT and 4-WIRE SENSE jacks, as shown in Figure 1-4. Be sure to use the 4-wire connections as shown.

Figure 1-4

Connections for resistance accuracy verification

EDIT

DISPLAY

TOGGLE

POWER

V

LOCAL

REL

67

DIGITS SPEED

4- WIRE

INPUT/

SENSE

OUTPUT

HI

125V

PEAK

5

SWEEP

SOURCE

I

2425 100 W SourceMeter

EDIT

EXIT ENTER

MEAS

FCTN

I

Ω

1

230

FILTER

89

STORE

LIMIT

RECALL

V

4

TRIG

+/-

CONFIG MENU

Model 2425

RANGE

AUTO

RANGE

®

ON/OFF

OUTPUT

Output HI

125V

5V

PEAK

PEAK

LO

250V

PEAK

!

TERMINALS

FRONT/

REAR

Sense HI

Resistance Calibrator

Output LO

Sense LO

Model 2425 Service Manual Performance Verification 1-19

2. Select the resistance calibrator external sense mode.

3. Configure the Model 2425 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

©

• Select SENSE-MODE, then press ENTER. The following will be displayed:

SENSE-MODE

2-WIRE 4-WIRE

• Select 4-WIRE, then press ENTER.

• Press EXIT to return to normal display.

4. Press MEAS Ω to select the ohms measurement function, and make sure the source
output is turned on.

5. Verify ohms measurement accuracy for each of the resistance values listed in Table 1-7. For each measurement:

• Set the resistance calibrator output to the nominal resistance or closest available

value.

NOTE It may not be possible to set the resistance calibrator to the specified value. Use

the closest possible setting, and modify reading limits accordingly.

• 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.

6. 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.

Table 1-7

Ohms measurement accuracy limits

Calibrator

Model 2425 range

2Ω
20Ω
200Ω
2kΩ
20kΩ
200kΩ
2MΩ
20MΩ

1

Nominal resistance values.

2

Reading limits based on Model 2425 normal accuracy specifications and nominal resistance values. If
actual resistance values differ from nominal values shown, recalculate reading limits using actual calibrator
resistance values and Model 2425 normal accuracy specifications. See Verification limits earlier in this
section for details.

resistance

1.9Ω
19Ω
190Ω

1.9kΩ
19kΩ
190kΩ

1.9MΩ
19MΩ

1

Model 2425 resistance reading limits

(1 year, 18°C to 28°C)

1.89649 to 1.90351Ω

18.9784 to 19.0216Ω

189.824 to 190.176Ω

1.89845 to 1.90155kΩ

18.9850 to 19.0150kΩ

189.847 to 190.153kΩ

1.89861 to 1.90139MΩ

18.9517 to 19.0483MΩ

-

2

1-20 Performance Verification Model 2425 Service Manual

2

Calibration

2-2 Calibration Model 2425 Service Manual

Introduction

Use the procedures in this section to calibrate the Model 2425. 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.

WARNING The information in this section is intended for qualified service per-

sonnel only. Do not attempt these procedures unless you are qualified
to do so. Some of these procedures may expose you to hazardous volt
ages.

Environmental conditions

Temperature and relative humidity

Conduct the calibration procedures at an ambient temperature of 18 to 28°C (65 to 82°F)
with relative humidity of less than 70% unless otherwise noted.

-

Warm-up period

Allow the Model 2425 to warm up for at least one hour before performing calibration.

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 manu­facturer.

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.

Model 2425 Service Manual Calibration 2-3

Calibration considerations

When performing the calibration procedures:

• Ensure that the test equipment is properly warmed up and connected to the Model
2425 front panel INPUT/OUTPUT jacks. Also be certain that the front panel jacks
are selected with the TERMINALS switch.

• 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. See Appendix B for more information.

WARNING The maximum common-mode voltage (voltage between LO and chas-

sis ground) is 250V peak. Exceeding this value may cause a break­down in insulation, creating a shock hazard.

CAUTION The maximum voltage between INPUT/OUTPUT HI and LO or

4-WIRE SENSE HI and LO is 125V peak. The maximum voltage
between INPUT/OUTPUT HI and 4-WIRE SENSE HI or between
INPUT/OUTPUT LO and 4-WIRE SENSE LO is 5V. Exceeding these
voltage values may result in instrument damage.

Calibration cycle

Perform calibration at least once a year to ensure the unit meets or exceeds its specifica­tions.

2-4 Calibration Model 2425 Service Manual

Recommended calibration equipment

Table 2-1 lists the recommended equipment for the calibration procedures. You can use
alternate equipment as long as that equipment has specifications comparable to those
listed in the table. 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

Description Manufacturer/Model Specifications

Digital Multimeter Hewlett Packard

HP3458A

DC Voltage

1

1V:
10V:
100V:

±5.6ppm
±4.3ppm
±6.3ppm

DC Current

1

10μA:
100μA:
1mA:
10mA:
100mA:
1A:

Precision Resistor

1

90-day, full-range accuracy specifications of ranges required for various measurement points.

2

Necessary for calibration of 3A current range. Resistor must be characterized to ±300ppm or better using

recommended DMM before calibrating 3A range.

2

Isotec RUG-Z-1R00-0.1 1Ω, ±0.1%, 100W

1Ω resistor characterization

The 1Ω resistor must be characterized to ±300ppm or better before calibrating the 3A cur­rent 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 current during
the 3A current range calibration procedure.

±25ppm
±23ppm
±20ppm
±20ppm
±35ppm
±110ppm

Model 2425 Service Manual Calibration 2-5

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

1. Press the MENU key, then choose CAL, and press ENTER. The instrument will display the following:

CALIBRATION

UNLOCK EXECUTE VIEW-DATES ©

3 SAVE LOCK CHANGE-PASSWORD

2. Select UNLOCK, then press ENTER. The instrument will display the following:

PASSWORD:

Use ß, ©, ¹, ƒ, ENTER or EXIT.

3. 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. (Press down RANGE for letters; up
RANGE for numbers.) Enter the present password on the display. (Front panel
default: 002425.)

4. Once the correct password is displayed, press the ENTER key. If the password was correctly entered, the following message will be displayed:

CALIBRATION UNLOCKED

Calibration can now be executed.

5. Press EXIT to return to normal display. Calibration will be unlocked and assume
the states summarized in Table 2-2. Attempts to change any of the settings listed
with calibration unlocked will result in an error +510, “Not permitted with cal
un-locked.”

NOTE With calibration unlocked, the sense function and range track the source func-

tion and range. That is, when :SOUR:FUNC is set to VOLT, the :SENS:FUNC
setting will be 'VOLT:DC'. When :SOUR:FUNC is set to CURR, the
:SENS:FUNC setting will be 'CURR:DC'. A similar command coupling exists
for :SOUR:VOLT:RANG/:SENS:VOLT:RANG and
SOUR:CURR:RANG:SENS:CURR:RANG.

2-6 Calibration Model 2425 Service Manual

Table 2-2

Calibration unlocked states

Mode State Equivalent remote command

Concurrent Functions
Sense Function
Sense Volts NPLC
Sense Volts Range
Sense Current NPLC
Sense Current Range
Filter Count
Filter Control
Filter Averaging
Source V Mode
Volts Autorange
Source I Mode
Current Autorange
Autozero
Trigger Arm Count
Trigger Arm Source
Trigger Count
Trigger Source

OFF
Source

1.0
Source V

1.0
Source I
10
REPEAT
ON
FIXED
OFF
FIXED
OFF
ON
1
Immediate
1
Immediate

:SENS:FUNC:CONC OFF
:SENS:FUNC <source_ function>
:SENS:VOLT:NPLC 1.0
:SENS:VOLT:RANG <range>
:SENS:CURR:NPLC 1.0
:SENS:CURR:RANG <range>
:SENS:AVER:COUN 10
:SENS:AVER:TCON REPeat
:SENS:AVER:STAT ON
:SOUR:VOLT:MODE FIXED
:SOUR:VOLT:RANG:AUTO OFF
:SOUR:CURR:MODE FIXED
:SOUR:CURR:RANG:AUTO OFF
:SYST:AZERO ON
:ARM:COUNT 1
:ARM:SOUR IMMediate
:TRIG:COUNT 1
:TRIG:SOUR IMMediate

Unlocking calibration by remote

To unlock calibration via remote, send the following command:

:CAL:PROT:CODE '<password>'

For example, the following command uses the default password:

:CAL:PROT:CODE 'KI002425'

Model 2425 Service Manual Calibration 2-7

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:

1. Press the MENU key, then choose CAL and press ENTER. The instrument will display the following:

CALIBRATION

UNLOCK EXECUTE VIEW-DATES ©

3 SAVE LOCK CHANGE-PASSWORD

2. Select UNLOCK, then enter the password. (Default: 002425.)

3. Select CHANGE-PASSWORD, then press ENTER. The instrument will display the following:

New Pwd: 002425

Use ß, ©, ¹, ƒ, ENTER or EXIT.

4. Using the range keys and the left and right arrow keys, enter the new password on the display.

5. Once the desired password is displayed, press the ENTER key to store the new password.

Changing the password by remote

To change the calibration password by remote, first send the present password, and then
send the new password. For example, the following command sequence changes the pass
word from the 'KI002425' remote default to 'KI_CAL':

:CAL:PROT:CODE 'KI002425'

:CAL:PROT:CODE 'KI_CAL'

You can use any combination of letters and numbers up to a maximum of eight characters.

NOTE If you change the first two characters of the password to something other than

“KI”, you will not be able to unlock calibration from the front panel.

-

2-8 Calibration Model 2425 Service Manual

Resetting the calibration password

If you lose the calibration password, you can unlock calibration by shorting together the
CAL pads, which are located on the display board. Doing so will also reset the password
to the factory default (KI002425).

See Section 5 for details on disassembling the unit to access the CAL pads. Refer to the
display board component layout drawing at the end of Section 6 for the location of the
CAL pads.

Viewing calibration dates and calibration count

When calibration is locked, only the UNLOCK and VIEW-DATES selections will be
accessible in the calibration menu. To view calibration dates and calibration count at any
time:

1. From normal display, press MENU, select CAL, and then press ENTER. The unit will display the following:

CALIBRATION

UNLOCK EXECUTE VIEW-DATES ©

2. Select VIEW-DATES, then press ENTER. The Model 2425 will display the next and last calibration dates and the calibration count as in the following example:

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). The unit will then prompt you to repeat the
calibration step that caused the error.

Model 2425 Service Manual Calibration 2-9

Remote error reporting

You can detect errors while in remote by testing the state of EAV (Error Available) bit (bit

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.

Front panel calibration

The following front panel calibration procedure calibrates all ranges of both the current
and voltage source and measure functions. Note that each range is separately calibrated by
repeating the entire procedure for each range.

Step 1: Prepare the Model 2425 for calibration.

1. Turn on the Model 2425 and the digital multimeter, and allow them to warm up for at least one hour before performing calibration.

2. Press the MENU key, then choose CAL and press ENTER. Select UNLOCK, and then press ENTER. The instrument will display the following:

PASSWORD:

Use ß, ©, ¹, ƒ ENTER or EXIT.

3. 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. Enter the present password on the display. (Front panel default: 002425.) Press ENTER to complete the process.

4. Press EXIT to return to normal display. Instrument operating states will be set as summarized in Table 2-2.

2-10 Calibration Model 2425 Service Manual

Step 2: Voltage calibration.

Perform the steps below for each voltage range, using Table 2-3 as a guide.

1. Connect the Model 2425 to the digital multimeter, as shown in Figure 2-1. Select the multimeter DC volts measurement function.

Figure 2-1

Voltage calibration test connections

4- WIRE

INPUT/

SENSE

OUTPUT

HI

EDIT

DISPLAY

TOGGLE

POWER

V

LOCAL

REL

67

DIGITS SPEED

125V

PEAK

5

SWEEP

SOURCE

I

2425 100 W SourceMeter

EDIT

EXIT ENTER

MEAS

Ω

230

FILTER

89

RECALL

STORE

FCTN

LIMIT

V

4

TRIG

+/-

CONFIG MENU

I

1

RANGE

AUTO

RANGE

®

ON/OFF

OUTPUT

125V

5V

PEAK

PEAK

LO

250V
PEAK

!

TERMINALS

FRONT/

REAR

Model 2425

Input HI

Digital Multimeter

2. From normal display, press the SOURCE V key.

3. Press the EDIT key to select the source field (cursor flashing in source display field), and then use the down RANGE key to select the 200mV source range.

4. From normal display, press MENU.

5. Select CAL, then press ENTER. The unit will display the following:

CALIBRATION

UNLOCK EXECUTE VIEW-DATES ©

ß SAVE LOCK CHANGE-PASSWORD

Input LO

Model 2425 Service Manual Calibration 2-11

6. Select EXECUTE, then press ENTER. The instrument will display the following message:

V-CAL

Press ENTER to Output +200.00mV

7. Press ENTER. The Model 2425 will source +200mV and simultaneously display the following:

DMM RDG: +200.0000mV

Use ß, ©, ¹, ƒ, ENTER or EXIT.

8. Note and record the DMM reading, and then adjust the Model 2425 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 posi
tion (or use the number keys, 0-9, +/-). Note that the display adjustment range is
within ±10% of the present range.

9. 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

10. Press ENTER. The Model 2425 will source 0mV and at the same time display the following:

DMM RDG: +000.0000mV

Use ß, ©, ¹, ƒ, ENTER or EXIT.

11. Note and record the DMM reading, and then adjust the Model 2425 display to agree with the actual DMM reading. Note that the display value adjustment limits are within ±1% of the present range.

12. After adjusting the display value to agree with the DMM reading, press ENTER. The unit will then display the following:

V-CAL

Press ENTER to Output -200.00mV

13. Press ENTER. The Model 2425 will source -200mV and display the following:

DMM RDG: -200.0000mV

Use ß, ©, ¹, ƒ, ENTER or EXIT.

14. Note and record the DMM reading, and then adjust the Model 2425 display to agree with the DMM reading. Again, the maximum display adjustment is within ±10% of the present range.

15. After adjusting the display value to agree with the DMM reading, press ENTER and note that the instrument displays:

V-CAL

Press ENTER to Output +000.00mV

16. Press ENTER. The Model 2425 will source 0mV and simultaneously display the following:

DMM RDG: +000.0000mV

Use ß, ©, ¹, ƒ, ENTER or EXIT.

-

2-12 Calibration Model 2425 Service Manual

17. 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.

18. After adjusting the display to agree with the DMM reading, press ENTER to com­plete calibration of the present range.

19. Press EXIT to return to normal display, then select the 2V source range. Repeat steps 2 through 18 for the 2V range.

20. After calibrating the 2V range, repeat the entire procedure for the 20V and 100V ranges using Table 2-3 as a guide. Be sure to select the appropriate source range with the EDIT and RANGE keys before calibrating each range.

21. Press EXIT as necessary to return to normal display.

Table 2-3

Front panel voltage calibration

Source range1Source voltage Multimeter voltage reading

0.2V +200.00mV
+000.00mV

-200.00mV
+000.00mV

2V +2.0000V

+0.0000V

-2.0000V
+0.0000V

20V +20.000V

+00.000V

-20.000V
+00.000V

100V +100.00V

+000.00V

-100.00V
+000.00V

1

Use EDIT and RANGE keys to select source range.

2

Multimeter reading used in corresponding calibration step. See procedure.

___________ mV
___________ mV
___________ mV
___________ mV

___________ V
___________ V
___________ V
___________ V

___________ V
___________ V
___________ V
___________ V

___________ V
___________ V
___________ V
___________ V

2

Model 2425 Service Manual Calibration 2-13

Step 3: Current calibration.

Perform the following steps for each current range, using Table 2-4 as a guide.

1. 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

4- WIRE

INPUT/

SENSE

OUTPUT

HI

EDIT

DISPLAY

TOGGLE

POWER

V

LOCAL

REL

67

DIGITS SPEED

125V
PEAK

5

SWEEP

SOURCE

I

2425 100 W SourceMeter

EDIT

EXIT ENTER

MEAS

Ω

230

FILTER

89

RECALL

STORE

FCTN

LIMIT

V

4

TRIG

+/-

CONFIG MENU

I

1

RANGE

AUTO

RANGE

®

ON/OFF

OUTPUT

Model 2425

PEAK

5V

LO

TERMINALS

125V
PEAK

250V
PEAK

!

FRONT/

REAR

Input LO

Amps

Digital Multimeter

2. From normal display, press the SOURCE I key.

3. Press the EDIT key to select the source display field, and then use the down
RANGE key to select the 10μA source range.

4. From normal display, press MENU.

5. Select CAL, and then press ENTER. The unit will display the following:

CALIBRATION

UNLOCK EXECUTE VIEW-DATES ©

ß SAVE LOCK CHANGE-PASSWORD

2-14 Calibration Model 2425 Service Manual

6. Select EXECUTE, then press ENTER. The instrument will display the following message:

I-CAL

Press ENTER to Output +10.000μA

7. Press ENTER. The Model 2425 will source +10μA and simultaneously display the
following:

DMM RDG: +10.00000μA
Use ß, ©, ¹, ƒ, ENTER or EXIT.

8. Note and record the DMM reading, and then adjust the Model 2425 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 posi
tion (or use the number keys, 0-9, +/-). Note that the display adjustment range is
within ±10% of the present range.

9. 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

10. Press ENTER. The Model 2425 will source 0mA and at the same time display the following:

DMM RDG: +00.00000μA

Use ß, ©, ¹, ƒ, ENTER or EXIT.

11. Note and record the DMM reading, and then adjust the Model 2425 display to agree with the actual DMM reading. Note that the display value adjustment limits are within ±1% of the present range.

12. After adjusting the display value to agree with the DMM reading, press ENTER. The unit will then display the following:

I-CAL

Press ENTER to Output -10.000μA

13. Press ENTER. The Model 2425 will source -10μA and display the following:

DMM RDG: -10.00000μA

Use ß, ©, ¹, ƒ, ENTER or EXIT.

14. Note and record the DMM reading, and then adjust the Model 2425 display to agree with the DMM reading. Again, the maximum display adjustment is within ±10% of the present range.

15. After adjusting the display value to agree with the DMM reading, press ENTER and note that the instrument displays:

I-CAL

Press ENTER to Output +00.000μA

16. Press ENTER The Model 2425 will source 0μA and simultaneously display the
following:

DMM RDG: +00.00000μA

Use ß, ©, ¹, ƒ, ENTER or EXIT.

-

Model 2425 Service Manual Calibration 2-15

17. 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.

18. After adjusting the display to agree with the DMM reading, press ENTER to com­plete calibration of the present range.

19. Press EXIT to return to the normal display, and then select the 100μA source range
using the EDIT and up RANGE keys. Repeat steps 2 through 18 for the 100μA
range.

20. After calibrating the 100μA range, repeat the entire procedure for the 1mA through
1A ranges using Table 2-4 as a guide. Be sure to select the appropriate source
range with the EDIT and up RANGE keys before calibrating each range.

21. 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.

22. Select the DMM DC volts function.

23. Repeat steps 2 through 18 for the 3A range using Table 2-4 as a guide. When enter­ing the DMM reading, use the calculated current as follows: I = V/R, where V is
the DMM voltage reading, and R is the characterized value of the 1Ω resistor.

Figure 2-3

3A range current calibration test connections

EDIT

DISPLAY

TOGGLE

POWER

V

1

LOCAL

REL

67

DIGITS SPEED

I

MEAS

Ω

230

LIMIT

FILTER

89

RECALL

STORE

FCTN

2425 100 W SourceMeter

SOURCE

I

V

4

5

TRIG

SWEEP

+/-

CONFIG MENU

EXIT ENTER

Model 2425

Digital Multimeter

4- WIRE

INPUT/

SENSE

OUTPUT

HI

125V
PEAK

®

EDIT

RANGE

AUTO

RANGE

ON/OFF

OUTPUT

PEAK

LO

5V

!

TERMINALS

FRONT/

REAR

125V
PEAK

250V
PEAK

1Ω Resistor

Input HI

Input LO

2-16 Calibration Model 2425 Service Manual

Table 2-4

Front panel current calibration

Source range

1

Source current

10μA +10.000μA

+00.000μA

-10.000μA
+00.000μA

100μA +100.00μA

+000.00μA

-100.00μA
+000.00μA

1mA +1.0000mA

+0.0000mA

-1.0000mA
+0.0000mA

10mA +10.000mA

+00.000mA

-10.000mA
+00.000mA

100mA +100.00mA

+000.00mA

-100.00mA
+000.00mA

1A +1.0000A

+0.0000A

-1.0000A
+0.0000A

3

3A

+3.0000A
+0.0000A

-3.0000A
+0.0000A

Multimeter

current reading

___________ μA
___________ μA
___________ μA
___________ μA

___________ μA
___________ μA
___________ μA
___________ μA

___________ mA
___________ mA
___________ mA
___________ mA

___________ mA
___________ mA
___________ mA
___________ mA

___________ mA
___________ mA
___________ mA
___________ mA

___________ A
___________ A
___________ A
___________ A

___________ A
___________ A
___________ A
___________ A

2

1

Use EDIT and RANGE keys to select source range.

2

Multimeter reading used in corresponding calibration step. See procedure.

3

Current calculated as follows: I=V/R, where V is the DMM reading, and R is the

characterized value of the 1Ω resistor.

Model 2425 Service Manual Calibration 2-17

Step 4: Enter calibration dates and save calibration.

NOTE For temporary calibration without saving new calibration constants, proceed to

Step 5: Lock out calibration.

1. From normal display, press MENU.

2. Select CAL, and then press ENTER. The Model 2425 will display the following:

CALIBRATION

UNLOCK EXECUTE VIEW-DATES ©

ß SAVE LOCK CHANGE-PASSWORD

3. Select SAVE, then press ENTER. The unit will display the following message:

SAVE CAL

Press ENTER to continue; EXIT to abort calibration sequence

4. Press ENTER. The unit will prompt you for the calibration date:

CAL DATE: 12/15/2000

Use ß, ©, ¹, ƒ, ENTER or EXIT.

5. Change the displayed date to today's date, then press the ENTER key. Press ENTER again to confirm the date.

6. The unit will then prompt for the calibration due date:

NEXT CAL: 12/15/2001

Use ß, ©, ¹, ƒ, ENTER or EXIT.

7. Set the calibration due date to the desired value, then press ENTER. Press ENTER again to confirm the date.

8. Once the calibration dates are entered, calibration is complete, and the following message will be displayed:

CALIBRATION COMPLETE

Press ENTER to confirm; EXIT to abort

9. Press ENTER to save the calibration data (or press EXIT to abort without saving calibration data.) The following message will be displayed:

CALIBRATION SUCCESS

Press ENTER or EXIT to continue.

10. Press ENTER or EXIT to complete process.

Step 5: Lock out calibration.

1. From normal display, press MENU.

2. Select CAL, then press ENTER. The Model 2425 will display the following:

CALIBRATION

UNLOCK EXECUTE VIEW-DATES ©

ß SAVE LOCK CHANGE-PASSWORD

3. Select LOCK, then press ENTER to lock out calibration.

2-18 Calibration Model 2425 Service Manual

Remote calibration

Use the following procedure to perform remote calibration by sending SCPI commands
over the IEEE-488 bus or RS-232 port. The remote commands and appropriate parameters
are separately summarized for each step.

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

:PROTected

:CODE '<password>'

:COUNT?
:SAVE
:LOCK
:LOCK?
:DATE <y>,<m>,<d>
:DATE?
:NDUE <y>,<m>,<d>
:NDUE?
:SENSe <nrf>

:DATA?

:SOURce <nrf>

:DATA?

*Calibration data will not be saved if:

1. Calibration was not unlocked with :CODE command.

2. Invalid data exists. (For example, cal step failed or was aborted.)

3. Incomplete number of cal steps were performed. (For example, omitting a negative full-scale step.)

Ranges that calibrated successfully will be saved if calibration is unlocked. Ranges that failed will not be saved.

Calibration subsystem.

Cal commands protected by password.

Unlock cal; changes password if cal is already unlocked.

(Default password: KI002425.)
Query number of times 2425 has been calibrated.
Save calibration data to EEPROM.*
Lock calibration, inhibit SAVE command operation.
Request cal lock status.
Program calibration year, month, day.
Query calibration year, month, day.
Program calibration due year, month, day.
Query calibration due year, month, day.
Calibrate active measure range. (See Table 2-6 parameters.)

Query measurement cal constants for active range.
Calibrate active source range. (See Table 2-7 parameters.)

Query source cal constants for active range.

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. Note that
each sense range requires three parameters: zero, negative full scale, and positive full
scale. Similarly, each source range requires four parameters: two zero parameters, a posi
tive full-scale parameter, and a negative full-scale parameter.

Table 2-6

Recommended :CALibration:PROTected:SENse parameter ranges

-

Sense
range

0.2V
2V
20V
100V

10μA
100μA
1mA
10mA
100mA
1A
3A

First parameter

(zero)

-0.002 to +0.002

-0.02 to +0.02

-0.2 to +0.2

-1 to +1

-1E-7 to +1E-7

-1E-6 to +1E-6

-1E-5 to +1E-5

-1E-4 to +1E-4

-1E-3 to +1E-3

-1E-2 to +1E-2

-3E-2 to +3E-2

Second parameter

(negative full scale)

-0.18 to -0.22

-1.8 to -2.2

-18 to -22

-90 to -110

-9E-6 to -11E-6

-90E-6 to -110E-6

-0.9E-3 to -1.1E-3

-9E-3 to -11E-3

-90E-3 to -110E-3

-0.9 to -1.1

-2.7 to -3.15

Third parameter

(positive full scale)

+0.18 to +0.22
+1.8 to +2.2
+18 to +22
+90 to +110

+9E-6 to +11E-6
+90E-6 to +110E-6
+0.9E-3 to +1.1E-3
+9E-3 to +11E-3
+90E-3 to +110E-3
+0.9 to +1.1
+2.7 to +3.15

2-20 Calibration Model 2425 Service Manual

Table 2-7

Recommended :CALibration:PROTected:SOURce parameter ranges

First parameter

Source range

0.2V
2V
20V
100V

10μA
100μA
1mA
10mA
100mA
1A
3A

Note: Parameter steps for each range may be performed in any order, but all parameter steps for each range must be completed. For
optimum calibration, use parameters within recommended limits.

(negative full scale)

-0.18 to -0.22

-1.8 to -2.2

-18 to -22

-90 to -110

-9E-6 to -11E-6

-90E-6 to -110E-6

-0.9E-3 to -1.1E-3

-9E-3 to -1E-3

-90E-3 to -110E-3

-0.9 to -1.1

-2.7 to -3.15

Second parameter

(negative zero)

-0.002 to +0.002

-0.02 to +0.02

-0.2 to +0.2

-1 to +1

-1E-7 to +1E-7

-1E-6 to +1E-6

-1E-5 to +1E-5

-1E-4 to +1E-4

-1E-3 to +1E-3

-1E-2 to +1E-2

-3E-2 to +3E-2

Third parameter

(positive full scale)

+0.18 to +0.22
+1.8 to +2.2
+18 to +22
+90 to +110

+9E-6 to +11E-6
+90E-6 to +110E-6
+0.9E-3 to +1.1E-3
+9E-3 to +11E-3
+90E-3 to +110E-3
+0.9 to +1.1
+2.7 to +3.15

Fourth parameter

(positive zero)

-0.002 to +0.002

-0.02 to +0.02

-0.2 to +0.2

-1 to +1

-1E-7 to +1E-7

-1E-6 to +1E-6

-1E-5 to +1E-5

-1E-4 to +1E-4

-1E-3 to +1E-3

-1E-2 to +1E-2

-3E-2 to +3E-2

Remote calibration procedure

Step 1: Prepare the Model 2425 for calibration.

1. Connect the Model 2425 to the controller IEEE-488 interface or RS-232 port using a shielded interface cable.

2. Turn on the Model 2425 and the test equipment, and allow them to warm up for at least one hour before performing calibration.

3. If you are using the IEEE-488 interface, make sure the primary address of the
Model 2425 is the same as the address specified in the program you will be using
to send commands. (Use the MENU key and the COMMUNICATION menu to
access the IEEE-488 address.)

Step 2: Voltage calibration.

1. Connect the Model 2425 to the digital multimeter, and select the multimeter DC volts function. (Figure 1-2).

2. Send the commands summarized in Table 2-8 in the order listed to initialize volt­age calibration. (When the :CAL:PROT:CODE command is sent, the instrument
will assume the operating states listed in Table 2-2.)

Model 2425 Service Manual Calibration 2-21

3. 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
would be sent:

:SOUR:VOLT:RANG 2

• Program the source to output the negative full-range value using the
:SOUR:VOLT command. For example:

:SOUR:VOLT -2

• 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 2V range
would be:

:CAL:PROT:SOUR -1.998

:CAL:PROT:SENS -1.998

• Program the voltage source for 0V output using the :SOUR:VOLT 0.0 com­mand.

• Note the multimeter reading.

• Send the source and sense calibration commands using the multimeter reading
for the parameter. For example:

:CAL:PROT:SOUR1E-3

:CAL:PROT:SmENS1E-3

• Set the source to the positive full-range value using the :SOUR:VOLT com­mand. For example:

:SOUR:VOLT 2

• 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.

• Note and record the multimeter reading.

• Send the :CAL:PROT:SOUR command using the multimeter reading as the
command parameter. For example:

:CAL:PROT:SOUR -1.02E-3

2-22 Calibration Model 2425 Service Manual

Table 2-8

Voltage calibration initialization commands

Command Description

*RST
:SOUR:FUNC VOLT
:SENS:CURR:PROT 0.1
:SENS:CURR:RANG 0.1
:SOUR:VOLT:PROT MAX
:SYST:RSEN OFF
:CAL:PROT:CODE 'KI002425'
:OUTP:STAT ON

Restore GPIB defaults.
Activate voltage source.
Current limit when voltage source is active.
Make sure 1A range is not active.
Maximum allowable source voltage.
Disable remote sensing.
Unlock cal.
Turn source on.

Step 3: Current calibration.

1. Connect the Model 2425 to the digital multimeter (Figure 2-2), and select the mul­timeter DC current function.

2. Send the commands summarized in Table 2-10 in the order listed to initialize cur­rent calibration.

Model 2425 Service Manual Calibration 2-23

Table 2-9

Voltage range calibration commands

Step Command/procedure

1
2
3
4
5
6
7
8

9
10
11
12
13
14
15
16
17
18
19
20
21
22

:SOUR:VOLT:RANGE <Range>
:SOUR:VOLT -<Source_value>
Take DMM reading.

2

:CAL:PROT:SOUR <DMM_Reading>
Check 2425 for errors.

3

:CAL:PROT:SENS <DMM_Reading>
Check 2425 for errors.
:SOUR:VOLT 0.0
Take DMM reading.
:CAL:PROT:SOUR <DMM_Reading>
Check 2425 for errors.
:CAL:PROT:SENS <DMM_Reading>
Check 2425 for errors.
:SOUR:VOLT +<Source_value>
Take DMM reading.
:CAL:PROT:SOUR <DMM_Reading>
Check 2425 for errors.
:CAL:PROT:SENS <DMM_Reading>
Check 2425 for errors.
:SOUR:VOLT 0.0
Take DMM reading.
:CAL:PROT:SOUR <DMM_Reading>

1

Description

Select source range.
Establish negative full-range polarity.
Read actual output value.
Calibrate sense function negative full scale.

Calibrate source function negative full scale.

Set output to 0V.
Read actual output value.
Calibrate sense function negative zero.

Calibration source function negative zero.

Establish positive full-range polarity.
Read actual output value.
Calibrate sense function positive full scale.

Calibrate source function positive full scale.

Set output to 0V.
Read actual output value.
Calibrate source positive zero.

1

Perform complete procedure for each range, where <Range> = 0.2, 2, 20, and 100, and<Source_value> = 0.2, 2, 20, and 100.

2

<DMM_Reading> parameter is multimeter reading from previous step.

3

Use :SYST:ERR? query to check for errors.

3. Calibrate the 10μA to 1A current ranges using the procedure summarized in Table
2-11. For each range:

• Send the :SOUR:CURR:RANG command to select the source and sense range
being calibrated. For example, for the 1mA range, the command is:

:SOUR:CURR:RANG 1E-3

• 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.

2-24 Calibration Model 2425 Service Manual

• 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

• Program the current source for 0A output using the :SOUR:CURR 0.0 com­mand.

• Note the multimeter reading.

• Send the source and sense calibration commands using the multimeter reading
for the parameter. For example:

:CAL:PROT:SOUR 1E-6

:CAL:PROT:SENS 1E-6

• Set the source to the positive full-range value using the :SOUR:CURR com­mand. For example, for the 1mA range:

:SOUR:CURR 1E-3

• Note and record the multimeter reading.

• Send the source and sense commands using the multimeter reading as the
parameter. For example:

:CAL:PROT:SOUR 1.03E-3

:CAL:PROT:SENS 1.03E-3

• Send the :SOUR:CURR 0.0 command to set the source current to 0A.

• Note and record the multimeter reading.

• Send the :CAL:PROT:SOUR command using the multimeter reading as the
command parameter. For example:

:CAL:PROT:SOUR 1E-6

4. 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.

5. 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
resistor.

Table 2-10

Current calibration initialization commands

Command Description

:SOUR:FUNC CURR
:SENS:VOLT:PROT 20
:SENS:VOLT:RANG 20
:OUTP:STAT ON

Select source current mode.
Voltage limit when current source is active.
Make sure 100V range is not active.
Turn source on.

Model 2425 Service Manual Calibration 2-25

Table 2-11

Current range calibration commands

Step Command/procedure

1

:SOUR:CURR:RANGE <Range>

2

:SOUR:CURR -<Source_value>

3

Take DMM reading.

4

:CAL:PROT:SOUR <DMM_Reading>

5

Check 2425 for errors.

6

:CAL:PROT:SENS <DMM_Reading>

7

Check 2425 for errors.

8

:SOUR:CURR 0.0

9

Take DMM reading.

10

:CAL:PROT:SOUR <DMM_Reading>

11

Check 2425 for errors.

12

:CAL:PROT:SENS <DMM_Reading>

13

Check 2425 for errors.

14

:SOUR:CURR +<Source_value>

15

Take DMM reading.

16

:CAL:PROT:SOUR <DMM_Reading>

17

Check 2425 for errors.

18

:CAL:PROT:SENS <DMM_Reading>

19

Check 2425 for errors.

20

:SOUR:CURR 0.0

21

Take DMM reading.

22

:CAL:PROT:SOUR <DMM_Reading>

1

Perform complete procedure for each range, where <Range> and <Source_value> = 10E-6, 100E-6, 1E-3, 10E-3, 100E-3, 1, or 3.

2

<DMM_Reading> parameter is multimeter reading from previous step.

3

Use :SYST:ERR? query to check for errors.

2

3

1

Description

Select source range.
Establish negative full-range polarity.
Read actual output value.
Calibrate sense function negative full scale.

Calibrate source function negative full scale.

Set output to 0A.
Read actual output value.
Calibrate sense function negative zero.

Calibration source function negative zero.

Establish positive full-range polarity.
Read actual output value.
Calibrate sense function positive full scale.

Calibrate source function positive full scale.

Set output to 0A.
Read actual output value.
Calibrate source positive zero.

Step 4: Program calibration dates.

Use following commands to set the calibration date and calibration due date:

:CAL:PROT:DATE <year>, <month>, <day> (Calibration date)

:CAL:PROT:NDUE <year>, <month>, <day> (Next calibration due date)

Note that the year, month, and date must be separated by commas. The allowable range for
the year is from 1998 to 2097, the month is from 1 to 12, and the date is from 1 to 31.

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.

Step 6: Lock out calibration.

To lock out further calibration, send the following command after completing the calibra­tion procedure:

:CAL:PROT:LOCK

Single-range calibration

Normally, the complete calibration procedure should be performed to ensure that the
entire instrument is properly calibrated. In some instances, however, you may want to
calibrate only certain ranges. To do so, complete the entire procedure only for the range(s)
to be calibrated. Keep in mind, however, that you must complete all parameter steps for
each source or sense range. Also be sure to set calibration dates and save calibration after
calibrating the desired range(s).

3

Routine Maintenance

3-2 Routine Maintenance Model 2425 Service Manual

CAUTION:FOR CONTINUED PROTECTION AGAINST FIRE HAZARD,REPLACE FUSE WITH SAME TYPE AND RATING.

CAUTION:FOR CONTINUED PROTECTION AGAINST FIRE HAZARD,REPLACE FUSE WITH SAME TYPE AND RATING.

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.

The power line fuse is accessible from the rear panel, just above the AC power receptacle
(Figure 3-1).

Figure 3-1

Rear panel

WARNING: NO INTERNAL OPERATOR SERVICABLE PARTS, SERVICE BY QUALIFIED PERSONNEL ONLY.

5V

HI

125V
PEAK

4-WIRE
SENSE

WITH FRONT PANEL MENU)

5V

PEAK

LO

INPUT/

!

OUTPUT

IEEE-488

(ENTER IEEE ADDRESS

125V
PEAK

PK

250V
PEAK

PEAK

5V

V, Ω,

GUARD

GUARD
SENSE

RS232

TRIGGER

LINK

MADE IN

U.S.A.

LINE FUSE

SLOWBLOW

3.15A, 250V

LINE RATING

100-240VAC

50, 60HZ

250VA MAX

INTERLOCK-

DIGITAL I/O

Perform the following steps to replace the line fuse:

1. Carefully grasp and squeeze together the locking tabs that secure the fuse carrier to the fuse holder.

2. Pull out the fuse carrier, and replace the fuse with the type specified in Table 3-1.

Model 2425 Service Manual Routine Maintenance 3-3

CAUTION To prevent instrument damage, use only the fuse type specified in

Table 3-1.

3. Re-install the fuse carrier.

NOTE 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
information.

Table 3-1

Power line fuse

Keithley part

Line voltage Rating

no.

100-240V 250V, 3.15A, Slow Blow 5 × 20mm FU-106-3.15

3-4 Routine Maintenance Model 2425 Service Manual

4

Troubleshooting

4-2 Troubleshooting Model 2425 Service Manual

Introduction

This section of the manual will assist you in troubleshooting and repairing the Model

2425. Included are self-tests, test procedures, troubleshooting tables, and circuit descrip
tions. Note that disassembly instructions are located in Section 5, and component layout
drawings are at the end of Section 6.

-

Safety considerations

WARNING The information in this section is intended for qualified service

personnel only. 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.

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. 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
replacement 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 2425 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 parts, adhere to the handling
precautions and cleaning procedures explained in Section 5.

• Many CMOS devices are installed in the Model 2425. 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 2425
must be recalibrated. See Section 2 for details on calibrating the unit.

Model 2425 Service Manual Troubleshooting 4-3

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. In the event of a test failure, refer to Display board checks for
details on troubleshooting the display board.

KEYS test

The KEYS test lets you check the functionality of each front panel key. Perform the fol­lowing steps to run the KEYS test.

1. Display the MAIN MENU by pressing the MENU key.

2. Select TEST, and press ENTER to display the SELF-TEST MENU.

3. Select DISPLAY-TESTS, and press ENTER to display the following menu:

FRONT PANEL TESTS

KEYS DISPLAY-PATTERNS CHAR-SET

4. Select KEYS, and press ENTER to start the test. When a key is pressed, the label name for that key will be displayed to indicate that it is functioning properly. When the key is released, the message “No keys pressed” is displayed.

5. Pressing EXIT tests the EXIT key. However, the second consecutive press of EXIT aborts the test and returns the instrument to the SELF-TEST MENU. Continue pressing EXIT to back out of the menu structure.

4-4 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:

1. Display the MAIN MENU by pressing the MENU key.

2. Select TEST, and press ENTER to display the SELF-TEST MENU.

3. Select DISPLAY-TESTS, and press ENTER to display the following menu:

FRONT PANEL TESTS

KEYS DISPLAY-PATTERNS CHAR-SET

4. Select DISPLAY-PATTERNS, and press ENTER to start the display test. There
are five parts to the display test. Each time a front panel key (except EXIT) is
pressed, the next part of the test sequence is selected. The five parts of the test
sequence are as follows:

• Checkerboard pattern (alternate pixels on) and all annunciators.

• Checkerboard pattern and the annunciators that are on during normal opera­tion.

• Horizontal lines (pixels) of the first digit are sequenced.

• Vertical lines (pixels) of the first digit are sequenced.

• Each digit (and adjacent annunciator) is sequenced. All the pixels of the
selected digit are on.

5. When finished, abort the display test by pressing EXIT. The instrument returns to the FRONT PANEL TESTS MENU. Continue pressing EXIT to back out of the menu structure.

CHAR SET test

The character set test lets you display all characters. Perform the following steps to run the
character set test:

1. Display the MAIN MENU by pressing the MENU key.

2. Select TEST, and press ENTER to display the SELF-TEST MENU.

3. Select DISPLAY-TESTS, and press ENTER to display the following menu:

FRONT PANEL TESTS

KEYS DISPLAY-PATTERNS CHAR-SET

4. Select CHAR-SET, and press ENTER to start the character set test. Press any key except EXIT to cycle through all displayable characters.

5. When finished, abort the character set test by pressing EXIT. The instrument returns to the FRONT PANEL TESTS MENU. Continue pressing EXIT to back out of the menu structure.

Model 2425 Service Manual Troubleshooting 4-5

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 drawings:

Figure 4-1 — Overall block diagram

Figure 4-2 — Analog circuitry block diagram

Figure 4-3 — Power supply block diagram

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.

• Digital circuits — includes the microcomputer that controls the analog section,
front panel, and GPIB and RS-232 ports, as well as associated interfacing circuits.

• Power supplies — converts the AC line voltage into DC voltages that supply the
power for the digital and analog circuits, and the output stage.

-

4-6 Troubleshooting Model 2425 Service Manual

Figure 4-1

Overall block diagram

Analog Section

Display,

Keyboard

Digital

I/O

Trigger

Link

Front

Panel

Controller

Trigger,

Digital

I/O

DACs

Clamps

Feedback

A/D

Converter

Microcomputer

Output

Stage

RS-232

GPIB

Interface

Guard

Buffer

Output

Guard

RS-232 I/O

GPIB I/O

To Analog

Circuits

±15V

Analog

Power

Supply

Digital Section

Output Stage

+5V

±42V

Power Supply

To

±150V

Output

Stage

Power

Supply

Line In

To

Digital Circuits

+5V +12V

Digital

Power

Supply

Model 2425 Service Manual Troubleshooting 4-7

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. 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. If the unit is set for SV (source voltage), it
will source voltage until the compliance current is reached (as determined by the I DAC
setting), and the current loop will override the voltage loop. If, however, the unit is set for
SI (source current), it will source current until the compliance voltage is reached (as
determined by the V DAC setting), and the voltage loop will override the current loop. A
priority bit in the Vclamp/I clamp circuit controls these functions.

The error amplifier adds open-loop gain and slew-rate control to the system to assure
accuracy and provide a controllable signal for the output stage, which provides the
necessary voltage and current gain to drive the output. Sense resistors in the HI output lead
provide output current sensing, and a separate sense resistor is used for each current range.
The 1A and 3A ranges use 0.2V full-scale for a full-range output, while all other ranges
use 2V output for full-scale current. Voltage feedback is routed either internally or
externally.

Figure 4-2

Analog circuitry block diagram

V DAC

I DAC

Control

FB

VFB

A/D

There are four voltage ranges: 0.2V, 2V, 20V, and 100V. The feedback gain changes only
for the 20V and 100V ranges, resulting in three unique feedback gain values. A multi

IFB

V Clamp

I Clamp

+7

MUX

Stage

+42

+150

+

-

Sense

Resistors

Protection

Protection

O

Output

HI

S+

Output

LO

S-

Guard

Out

Guard

Sense

-42

-150

Error
Amp

VFB

IFB

S

Output

O

Remote

O

-

4-8 Troubleshooting Model 2425 Service Manual

plexer directs the voltage feedback, current feedback, reference, or ground signal to the
A/D converter. An opto-isolated interface provides control signals for both DACs, analog
circuit control, and 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. The +12VD supply is set to pro
gram the flash ROM. (See Digital circuitry below.)

A constant-frequency switching supply runs off the +24VD supplies and generates all the
floating and output supply voltages for the analog board: +5V and ±15V, ±42V and
±150V.

Figure 4-3

Power supply block diagram

-

Line
Neutral

Analog Board

+15V +5V

FF

Constant Frequency
Low Noise Floating
Switching Supply

PFC

D

DC/DC

Converter

F

+24Vdc

-15V

+24dc

F

DC

Regulators

Output Stage

-150V -42V +42V +150V

+12Vdc

+5Vdc

O

Digital

Circuits

D

D

Model 2425 Service Manual Troubleshooting 4-9

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.

Output transistors Q518 and Q521 are cascoded with output MOSFETs Q516 and Q523.
All other MOSFETs and transistors are slaves, and the voltages across these devices are
determined by the resistor-capacitor ladder circuits shown. High-current drive capability
is provided by Q500-Q511. Coarse current limits are built into the output stage.

-

4-10 Troubleshooting Model 2425 Service Manual

Figure 4-4

Output stage simplified schematic

+85V

Maindrive

O

+15Vf

300K

F

HI Drive

+

-

Q500

+42V

Q504

Q514

Q516

Q518

F

Q521

-15Vf

F

Q523

Q525

Q507

-42V

Q503

HI Drive

-85V

Model 2425 Service Manual Troubleshooting 4-11

A/D converter

The SourceMeter unit uses a multi-slope charge balance A/D converter with a single-slope
run-down. The converter is controlled by gate array U610. Commands are issued by the
MPU on the digital board through communications opto-isolators to U610, and U610
sends A/D reading data back through opto-isolators to the digital board for calibration and
processing.

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. If the unit is in the SI mode, the voltage on output HI is
equal to the source current multiplied by the external resistance value. An equivalent
voltage will be generated by the guard circuit, and a guard sense terminal is provided to
sense around the voltage drop in the guard leads since significant current can flow
(50mA).

Digital circuitry

Refer to Figure 4-5 for the following discussion on digital circuitry.

The core digital circuitry uses a Motorola 68332 microcontroller running at 16.78MHz.
The memory configuration includes two 256K × 8-bit flash EEPROMs and two 128K × 8­bit RAMs used in parallel to utilize the 16-bit data bus of the MPU. The RAM is battery
backed-up, providing continued storage of data buffer information during power-down
cycles, and flash ROM support allows internal firmware upgrades using either the serial or
GPIB port for downloading new firmware. All calibration constants and the save 0 setup
are stored in a separate serial EEPROM. Setups 1 through 4 are stored in battery backed­up RAM.

External communication is provided via GPIB and serial interfaces. A 9914 GPIB IEEE­488 standard interface IC is used for the GPIB, and a 68332 Queued Serial Module (QSM)
provides the serial UART. For internal communications, the Time Processing Unit (TPU)
is used for serial communications with the front panel display module, and both the TPU
and QSM handle digital-to-analog interfacing.

4-12 Troubleshooting Model 2425 Service Manual

Figure 4-5

Digital circuitry block diagram

A/D

Control/Data

Reset

2

E PROM

U17

A/D Interface

U9, U25

Voltage Source

Control

ROM

U15, U16

Microprocessor

U3

RAM

U12, U14

16.78MHz

Serial

Interface

U4

GPIB

U6, U13

U20

To Display

Board Controller

Trigger

U23

RS-232

Interface

IEEE-488
Interface

Trigger

Display board circuit theory

Display board components are shown in the digital circuitry block diagram in Figure 4-5.

U902 is the display microcontroller that controls the VFD (vacuum fluorescent display)
and interprets key data. The microcontroller has four peripheral I/O ports that are used for
the various control and read functions.

Display data is serially transmitted to the microcontroller from the digital board via the
TXB line to the microcontroller PD0 terminal. In a similar manner, key data is serially

Digital I/O

U7

Digital

I/O

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 char­acters. Each character is organized as a 5 × 7 matrix of dots or pixels and includes a long
under-bar segment to act as a cursor.

The display uses a common multiplexing scheme with each character refreshed in
sequence. U903 and U904 are the grid drivers, and U901 and U905 are the dot drivers.
Note that dot driver and grid driver data is serially transmitted from the microcontroller
(PD3 and PC1).

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
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.

Troubleshooting

Troubleshooting information for the various circuits is summarized below.

Display board checks

If the front panel display tests indicate that there is a problem on the display board, use
Table 4-1. See “Principles of operation” for display circuit theory.

Table 4-1

Display board checks

Step Item/component Required condition Remarks

1

Front panel test

2

J1033

3

U902, pin 1

4

U902, pin 43

5

U902, pin32

6

U902, pin 33

Verify that all segments operate.
+5V, ±5%
Goes low briefly on power up, and then

goes high.
4MHz square wave.
Pulse train every 1 ms.
Brief pulse train when front panel key is

pressed.

Use front panel display test.
Digital +5V supply.
Microcontroller RESET.

Controller 4MHz clock.
Control from main processor.
Key down data sent to main

processor.

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

1
2

3
4
5
6
7
8
9

Line fuse
Line power

TP502
TP503
TP504
TP505
TP507
TP508
TP510

Check continuity.
Plugged into live recepta-

cle, power on.

+150V, ±5%

-150V, ±5%
+38V, ±10%

-38V, ±10%
+15V, ±5%

-15V, ±5%
+5V, ±5%

Remove to check.
Check for correct power-up

sequence.
Referenced to TP501.
Referenced to TP501.
Referenced to TP501.
Referenced to TP501.
+15VF, referenced to

TP500.

-15VF, referenced to TP500.
+5VF, referenced to TP500.

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

1

Power-on test

2

U3 pin 19

3

U3 pin 7

4

U3 pin 68

5

U3, lines A0-A19

6

U3, lines D0-D15

7

U3 pin 66

8

U4 pin 7

9

U4 pin 8

10

U13 pins 34-42

11

U13 pins 26-31

12

U13 pin 24

13

U13 pin 25

14

U3 pin 43

15

U3 pin 44

16

U3 pin 45

17

U3 pin 47

RAM OK, ROM OK.
Digital common.
+5V
Low on power-up, then goes high.
Check for stuck bits.
Check for stuck bits.

16.78MHz.
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.

Verify that RAM and ROM are functional.
All signals referenced to digital common.
Digital logic supply.
MPU RESET line.
MPU address bus.
MPU data bus.
MPU clock.
RS-232 RX line.
RS-232 TX line.
IEEE-488 data bus.
IEEE-488 command lines.
IEEE-488 REN line.
IEEE-488 IFC line.
D_ADDATA
D_DATA
D_CLK
D_STB

4-16 Troubleshooting Model 2425 Service Manual

Analog circuitry checks

Table 4-4 summarizes analog circuitry checks.

Table 4-4

Analog circuitry checks

Step Item/component Required condition Remarks

TP200
TP201
TP202
TP203
TP213
TP218
TP219
TP214
TP232

1

1

1

1

1

2

2

2

1

>100V voltage protection
SOURCE +10V
SOURCE +10V (SVMI)
SOURCE +10V
SOURCE +10V
OUTPUT COM
OUTPUT COM
SVMI, OUTPUT ON, 20V
Bench defaults

-13V ±1V

-5V ±0.5V

-10V ±1V

-10.5V ±1V
0V ±0.1V
7V ±0.7V
7V ±0.7V
20V ±0.5V

6.4V ±0.6V

1
2
3
4
5
6
7
8
9

1

Measured with respect to FCOM (TP500).

2

Measured with respect to OCOM (TP501).

Battery replacement

WARNING 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. If the battery is absent
or totally exhausted, the display will show the “Reading buffer data lost” message shortly
after the Model 2425 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. (See Section 5.)

-

Model 2425 Service Manual Troubleshooting 4-17

Battery replacement precautions

WARNING The following precautions must be followed to avoid personal injury.

1. Wear safety glasses or goggles when working with lithium batteries.

2. Do not short the battery terminals together.

3. Keep lithium batteries away from all liquids.

4. Do not attempt to recharge lithium batteries.

5. Observe proper polarity when installing the battery.

6. Do not incinerate or otherwise expose the battery to excessive heat (>60°C).

7. Bulk quantities of lithium batteries should be disposed of as hazardous waste.

Battery replacement procedure

1. Remove the case cover and analog board assembly as covered in Section 5.

2. Locate the battery on the digital board.

3. Carefully unsolder and remove the old battery.

4. Install and solder the new battery in place.

5. Re-assemble the instrument, and turn it on. The “Reading buffer data lost” error message will be displayed.

6. Send the :SYST:MEM:INIT command via remote to perform the following:

• Clear the reading buffer.

• Initialize instrument setups 1 through 4 to present instrument settings.

• Initialize all 100 source memory locations to present instrument settings.

• Delete user math expressions.

4-18 Troubleshooting Model 2425 Service Manual

No comm link error

A “No Comm Link” error indicates that the front panel processor has stopped communi­cating 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
reseated as follows:

1. 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. Remove the analog board assembly as outlined in Section 5.

4. Locate the two firmware ROMS, U15 and U16, located on the digital board. These are the only ICs installed in sockets. (Refer to the component layout drawing at the end of Section 6 for exact locations.)

5. Carefully push down on each ROM IC to make sure it is properly seated in its socket.

CAUTION Be careful not to push down excessively; digital board could crack.

6. Connect the line cord, and turn on the power. If the problem persists, additional troubleshooting will be required.

5

Disassembly

5-2 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. Motherboard areas
covered by the shield have high-impedance devices or sensitive circuitry where contami
nation 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 you must solder 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
blow-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 2425 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 2425. Handle all

semiconductor 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 solder 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 assembly drawings located at the end of this section to assist you as you disassem­ble 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:

• Front panel assembly — 2430-040

• Analog board/heat sink/shield assembly — 2430-050

• Chassis assembly — 2430-051

• Chassis/analog board assembly — 2430-052

• Final chassis assembly — 2430-053

5-4 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.

1. Remove handle — The handle serves as an adjustable tilt-bail. Adjust its position

by gently pulling it away from the sides of the instrument case and swinging it up
or down. To remove the handle, swing the handle below the bottom surface of the
case and back until the orientation arrows on the handles line up with the orienta
tion arrows on the mounting ears. With the arrows lined up, pull the ends of the
handle away from the case.

2. 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” or “LEFT” on its inside surface.

-

3. Remove rear bezel — To remove the rear bezel, loosen the two screws that secure

the rear bezel to the chassis, then pull the bezel away from the case.

4. Remove grounding screws — Remove the two grounding screws that secure the

case to the chassis. They are located on the bottom of the case at the back.

5. Remove chassis — To remove the case, grasp the front bezel of the instrument,

and carefully slide the chassis forward. Slide the chassis out of the metal case.

NOTE To gain access to the components under the analog board shield, remove the

shield, which is secured to the analog board by a single screw.

Model 2425 Service Manual Disassembly 5-5

Analog board removal

Perform the following steps to remove the analog board. This procedure assumes that the
case cover is already removed.

1. Remove the small pulse board before removing the analog board.

2. Disconnect the front and rear input terminals. You must disconnect these input terminal connections for both the front and rear inputs:

• INPUT/OUTPUT HI and LO

• 4-WIRE SENSE HI and LO

•V, Ω, GUARD and GUARD SENSE (rear panel only)

Remove all the connections by pulling the wires off the pin connectors, then
remove the ferrite noise filters from the chassis. During re-assembly, use the fol
lowing table to identify input terminals:

Input terminals Front wire color Rear wire color

-

INPUT/OUTPUT HI
INPUT/OUTPUT LO
4-WIRE SENSE HI
4-WIRE SENSE LO
V, Ω, GUARD
GUARD SENSE

3. Unplug cables.

• Carefully unplug the ribbon cables at J1027, J1028, and J1029.

• Unplug the ON/OFF cable at J1034.

4. Remove screws.

• Remove 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 two screws that secure the heat sink to the chassis.

Red
Black
Yellow
Gray

-

-

White/Red
White/Black
White/Yellow
White/Gray
White
Blue/White

5-6 Disassembly Model 2425 Service Manual

5. Remove analog board assembly. After all screws have been removed, carefully lift the analog board assembly free of the main chassis.

6. Disassemble analog board assembly.

• Remove the screws that secure the analog board and heat sink to the analog
board subchassis.

• Carefully remove the heat sink by sliding the clips off the power transistors.

CAUTION Be careful not to damage the heat sink insulation layer.

• Remove the analog board from the subchassis.

• Remove four screws that secure the bottom cover, then remove the cover from
the bottom of the PC board.

NOTE When re-installing the heat sink, make sure that all clips are properly installed

and centered on each pair of output transistors.

Digital board removal

Perform the following steps to remove the digital board. This procedure assumes that the
analog board assembly is already removed.

NOTE In order to remove the digital board, the display board must first be removed.

1. Remove IEEE-488, Digital I/O, and RS-232 fasteners.

The IEEE-488, Digital I/O, and RS-232 connectors each have two nuts that secure the
connectors to the rear panel. Remove these nuts.

2. Remove POWER switch rod.

At the switch, place the edge of a flat-blade screwdriver in the notch on the pushrod.
Gently twist the screwdriver while pulling the rod from the shaft.

3. Unplug cables:

• Unplug the display board ribbon cable.

• Unplug the cables going to the power supply.

• Unplug the rear panel power module cable.

• The fan may need to be removed.

4. Remove digital board.

Slide the digital board forward until it is free of the guide pins, then remove the board.

During re-assembly, replace the board, and start the IEEE-488, Digital I/O, and RS-232
connector nuts and the mounting screw. Tighten all the fasteners once they are all in
place and the board is correctly aligned.

Model 2425 Service Manual Disassembly 5-7

Front panel disassembly

Use the following procedures to remove the display board and/or the pushbutton switch
pad:

1. Unplug the display board ribbon cables.

2. Remove 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. Pull the
retaining clips outward and, at the same time, pull the front panel assembly for
ward until it separates from the chassis.

3. Using a thin-bladed screwdriver, pry the plastic PC board stop (located at the bot-

tom of the display board) until the bar separates from the casing. Pull the display
board from the front panel.

4. Remove the switch pad by pulling it from the front panel.

-

Removing power components

The following procedures to remove the power supply and/or power module require that
the case cover and motherboard be removed, as previously explained.

Power module removal

Perform the following steps to remove the rear panel power module:

WARNING To avoid electrical shock, which could result in injury or death, the

ground wire of the power module must be connected to chassis
ground. When installing the power module, be sure to re-connect the
green and yellow ground wire to the threaded stud on the chassis.

1. Remove the analog board.

2. Unplug the cable connecting the power module to the digital board.

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.

5-8 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.

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 ensure proper operation, replace the analog signal wire ferrite noise filters, and
securely fasten the shield.

-

6

Replacement Parts

6-2 Replacement Parts Model 2425 Service Manual

Introduction

This section contains replacement parts information and component layout drawings for
the 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.

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 order­ing parts, be sure to include the following information:

• Instrument model number (Model 2425)

• Instrument serial number

• Part description

• 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.

• 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 ship­ping label.

Component layouts

The component layouts for the various circuit boards are provided on the following pages.
Drawings include:

• Analog board — 2430-100

• Display board — 2400-110

• Digital board — 2420-140

Model 2425 Service Manual Replacement Parts 6-3

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

CERAMIC
C215-C222,C611,C331,C332,C333,C334 CAP, 100PF, 5%, 100V, CERAMIC C-465-100P
C223,C224,C227-C230,C233C236,C239,

CAP, 33PF, 5%, 100V, CERAMIC C-465-33P

C240

C237,C238,C242,C243,C248,C249,C254,

CAP, .1UF, 10%, 25V, CERAMIC C-495-.1

C255
C241 CAP, 1000PF, 1%, 50V, CERAMIC C-347-1000P
C246,C336 CAP, 3300PF, 10%, 100V, CERAMIC C-430-3300P
C247 CAP, .01, 5%, 50V, NPO (1812) C-514-.01
C250,C251,C272,C297,C298,C299,C300,

CAP, .1UF, 10%, 25V, CERAMIC C-495-.1

C524
C258,C259,C260-C263,C269-C271,

CAP, .1UF, 10%, 25V, CERAMIC C-495-.1

C273-C282
C267,C268,C327 CAP, 1000P, 10%, 100V, CERAMIC C-451-1000P
C283 CAP, 100P, 10%, 100V, CERAMIC C-451-100P
C284-C291,C305C310,C321,C322,C548,

CAP, .1UF, 10%, 25V, CERAMIC C-495-.1

C558
C296,C330,C400 CAP, 270PF, 2.5%, 630V, POLYPRO-

C-405-270P

PYLENE
C311 CAP, 100UF, 20%, 16V, TANTALUM C-504-100
C312-C319 CAP, 10PF, 5%, 100V, CERAMIC C-372-10P
C320 CAP, 33PF, 5%, 100V, CERAMIC C-465-33P
C323,C324,C325,C326,C603,C604,C615 CAP, 47P, 5%, 100V, CERAMIC C-465-47P
C328 CAP, 22P, 2%, 200V, CERAMIC C-531-22P
C329 CAP, 220PF, 10%, 100V, CERAMIC C-451-220P
C409,C410 CAP, .15UF, 20%, 50V, CERAMIC C-418-.15
C412 CAP, 1UF, 20%, 35V, TANTALUM C-494-1
C501,C503 CAP, 3.3, 20%, 250V, ALUM ELEC-

C-400-3.3

TROLYTIC
C502,C504,C505,C506,C550,C551,C552,

CAP, .01U, 10%, 500V, CERAMIC C-497-.01

C553
C512,C514,C256,C257 CAP, 22PF, 10%, 100V, CERAMIC C-451-22P
C513 CAP, 560PF, 2.5%, 630V, POLYPRO-

C-405-560P

PYLENE

C515,C541 CAP, .1UF, 20%, 50V, CERAMIC C-418-.1

6-4 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

C664
C534,C535 CAP, 47U, 20%, 50V, ALUM C-579-47
C537,C538 CAP, 1UF, 10%, 500V, X7R (1825) C-525-.1
C539,C540 CAP, .1UF, 20%,100V, CERAMIC C-436-.1
C543 CAP, 10PF, 10%, 1000V, CERAMIC C-64-10P
C544,C545,C546,C547 CAP, .01U, 10%, 500V, CERAMIC C-497-.01
C556,C557,C559,C560,C562,C563,C616 CAP, 22UF, 20%, 25V, TANTALUM C-440-22
C565,C566,C581,C582,C600,C601,C602,

CAP, .1UF, 10%, 25V, CERAMIC C-495-.1

C605
C583,C584 CAP, 1000PF, 20%, 50V, CERAMIC C-418-1000P
C606,C607,C613,C614,C617,C618,C619,

CAP, .1UF, 10%, 25V, CERAMIC C-495-.1

C620
C610,C612 CAP, 2200P, 10%, 100V, CERAMIC C-430-2200P
C621,C622,C623,C624,C625,C650,C651,

CAP, .1UF, 10%, 25V, CERAMIC C-495-.1

C652
C659-C662 CAP, .1UF, 10%, 25V, CERAMIC C-495-.1
CR200-CR205,CR207,CR208,

DIODE, SWITCHING, MMBD914 RF-83

CR210-CR213
CR206,CR209,CR222,CR223, CR230-

DIODE, 1N3595 RF-43

CR233
CR216-CR221,CR235,CR236,CR239,

DIODE, SWITCHING, MMBD914 RF-83

CR518
CR224,CR225 SCHOTTKY BARRIER RECTIFIER RF-119
CR237,CR523 DIODE, DUAL SWITCHING,

RF-82

BAV99L
CR400,CR401 DIODE, 1N3595 RF-43
CR517,CR519 DIODE, SCHOTTKY BARRIER,

RF-132

200V, MBRB20200CT
CR522,CR524,CR525 DIODE, SWITCHING, MMBD914 RF-83
CR600 DIODE, DUAL HSM-2822T31 RF-95
CR601 DIODE, SCHOTTKY, SD103C RF-113
CR602 SCHOTTKY DIODE RF-125
HS1,HS2,HS3,HS4,HS5,HS6,HS7 HEAT SINK HS-55
J1027,J1036 CONN, HEADER STRAIGHT

CS-368-16

SOLDER PIN

Model 2425 Service Manual Replacement Parts 6-5

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 RL-176
K206,K207,K208 FORM 2A2B POLARIZED RELAY,

RL-207

S28B-5V
K211,K500 RELAY, SURFACE MOUNT RL-188
L201,L500,L501 CHOKE, SHIELD BEAD CH-52
L600,L601,L602 FERRITE CHIP, 600 OHM,

CH-62

BLM32A07
L603 FERRITE CHIP 600, OHM,

CH-62

BLM32A07
Q200,Q201,Q202,Q203,Q204,Q205,Q206,

Q207

Q208,Q210,Q212,Q214,Q216,Q218 TRANS, NPN CATV SILICON,

TRANS, N CHANNEL JFET,

SNJ132199

TG-294

TG-221

MPSH17
Q209,Q211,Q213,Q215,Q217,Q219 TRANS, CURR REG, CDLL5313 TG-321
Q220 TRANS, NPN SILICON, MJE340 TG-209
Q221 TRANS, PNP POWER, MJE350 TG-210
Q222,Q224 TRANS, N-CHAN JFET, SST4393 TG-263
Q223,Q229,Q234,Q239,Q244,Q245,Q246,

TRANS, N-MOSFET, VN0605T TG-243

Q255
Q225 TRANS, NPN SILICON, MJD340 TG-373
Q226 TRANS, PNP SILICON, MJD350 TG-374
Q227,Q257,Q501,Q510,Q515,Q517,Q519,

TRANS, NPN, MMBT3904 TG-238

Q522
Q228,Q247,Q248,Q520,Q601 TRANS, PNP, MMBT3906L TG-244
Q240,Q241 TRANS, N CHANNEL JFET,

TG-294

SNJ132199

Q242,Q243 TRANS, N-CHAN MOSFET,

TG-274

TN254ON8
Q249,Q528 TRANS, NPN SILICON, BC846BL, TG-278
Q250,Q529 TRANS PNP, BC856BL TG-287
Q256,Q258,Q401,Q404,Q405,Q410,Q411,

TRANS, N-MOSFET, VN0605T TG-243

Q420

6-6 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

TG-377

MOSFET, IRFR5305
Q417,Q419 TRANS, N CHANNEL MOSFET,

TG-339

RFD16N05LSM
Q418,Q542,Q230 TRANS, P-CHAN MOSFET,

TG-259

TP0610T
Q500,Q503 TRANS, POWER MOSFET,

TG-372

IRF3415S
Q502,Q540,Q541,Q602-Q605 TRANS, N-MOSFET, VN0605T TG-243
Q504,Q514,Q516,Q518 N CHANNEL POWER MOSFET TG-349
Q507,Q521,Q523,Q525 P CHANNEL POWER MOSFET TG-348
Q524,Q534,Q535,Q537,Q538,Q600 TRANS, NPN, MMBT3904 TG-238
Q526,Q527,Q530,Q531 TRANS, N CHANNEL MOSFET,

TG-302

SI9410DY
Q532,Q536 TRANS, N-CHANNEL FET, IRF630 TG-214

Q533,Q539 TRANS, P-CHANNEL, 200V, FET,

TG-215

IRF9630
R117-R128,R133-R136,R141-R144 RES, 10K, 5%, 250MW, METAL

R-376-10K

FILM
R129,R155,R211,R224-R229,R234-R237 RES, 10K, 1%, 100MW, THICK FILM R-418-10K
R130 RES, 10K, 1%, 100MW, THICK FILM R-418-10K
R137-140,R145-149,R713,R714 RES, 10K, 5%, 250MW, METAL

R-376-10K

FILM
R150,R151,R389,R390,R451,R520,R531,

RES, 1K, 1%, 100MW, THICK FILM R-418-1K

R559
R152,R656 RES, 4.99K, .1%, .125W, THIN FILM R-456-4.99K
R153,R154,R240,R243,R248,R251,R253,

R254

RES, 4.99K, 1%, 100MW, THICK

FILM

R-418-4.99K

R200,R201,R203,R232,R238 RESISTOR NETWORK, 10K-10K TF-236
R202,R204,R252,R255,R256,R259,R260,

R263
R205,R310,R485,R552,R595,R598,R723,

R724

RES, 100K, 1%, 100MW, THICK

FILM

RES, .0499, 1%, 100MW, THICK

FILM

R-418-100K

R-418-.0499

R207 RES, 20K, .1%, .125W, THIN FILM R-456-20K

Model 2425 Service Manual Replacement Parts 6-7

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 TF-243-5K
R216,R221,R223,R274,R275,R276,R277,

RES, 20K, 1%, 100MW, THICK FILM R-418-20K

R278

R217 RES, 121K, 1%,100MW, THICK

R-418-121K

FILM

R218 RES, 80.6K, 1%, 100MW, THICK

R-418-80.6K

FILM

R219,R220,R222,R230,R231,R373,R374,

R616

R241,R242,R249,R250,R653,R664 RES, 140K, 1%, 100MW, THICK

RES, 49.9K, 1%, 100MW, THICK

FILM

R-418-49.9K

R-418-140K

FILM

R244-R247,R281,R282,R284-R286,R288,

RES, 10K, 1%, 100MW, THICK FILM R-418-10K

R301

R257,R258,R261,R262,R265,R266,R311,

R312

R264,R267,R345,R364,R370,R371,R372,

R402

R272,R273,R347,R348,R511,R512,R589 RES, 249K, 1%, 100MW, THICK

RES, 4.99K, 1%, 100MW, THICK

FILM

RES, 100K, 1%, 100MW, THICK

FILM

R-418-4.99K

R-418-100K

R-418-249K

FILM
R279 RES, 20K, 1%, 100MW, THICK FILM R-418-20K
R280,R516,R523 RES, 4.02K, 1%, 100MW, THICK

R-418-4.02K

FILM
R283,R287,R297,R299,R349,R350,R351,

R352

RES, 30.1K, 1%, 100MW, THICK

FILM

R-418-30.1K

R289,R303,R681,R684 RES, 20K, .1%, .125W, THIN FILM R-456-20K
R290,R309,R336,R340,R343,R344,R353,

RES, 1K, 1%, 100MW, THICK FILM R-418-1K

R355
R291,R293,R682,R685 RES, 42.7K, .1%, .125W, THIN FILM R-456-42.7K
R292,R338,R527,R528,R533,R535,R544,

R546

RES, 100K, 1%, 100MW, THICK

FILM

R-418-100K

R294,R295,R296 RES, 100K, .1%, .125W, THIN FILM R-456-100K
R298,R300 RES, 150K, 1%, 100MW, THICK

R-418-150K

FILM

R302,R667 RES, .0499, 1%, 100MW, THICK

R-418-.0499

FILM
R304,R305,R306,R548 RES, 33, 5%, 250MW, METAL FILM R-376-33
R307,R413,R652,R665 RES, 357, 1%, 100MW, THICK FILM R-418-357

6-8 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,

R337

RES, 4.99K, 1%, 100MW, THICK

FILM

R-418-4.99K

R318,R563 RES, 15K, 1%, 100MW, THICK FILM R-418-15K
R332,R423,R430,R604,R606,R436 RES, 499, 1%, 100MW, THICK FILM R-418-499
R339,R357,R366,R367,R424,R425,R426,

R429

RES, 4.99K, 1%, 100MW, THICK

FILM

R-418-4.99K

R341,R342,R505 RES, 13K, 1%, 100MW, THICK FILM R-418-13K
R346 RES, 402K, 1%, 100MW, THICK

R-418-402K

FILM

R354,R437 RES, 560K, 5%, 250MW, METAL

R-376-560K

FILM

R356,R359,R361,R362,R365,R369,R418,

RES, 1K, 1%, 100MW, THICK FILM R-418-1K

R419

R358,R482,R484,R487 RES, 6.04K, 1%, 100MW, THICK

R-418-6.04K

FILM
R363 RES NET, VARIOUS, .1%, .1W TF-274
R368,R212 RES, 332, 1%, 100MW, THICK FILM R-418-332
R375,R376,R576,R578,R536,R537 RES, 10, 10%, 100MW, THICK FILM R-418-10
R388,R393-R399,R411,R412,R699 RES, 357, 1%, 100MW, THICK FILM R-418-357
R403,R404,R416,R417,R459,R488,R560,

R561

R420,R421,R456,R458,R460,R462,R466,

RES, 100K, 1%, 100MW, THICK

R-418-100K

FILM

RES, 1K, 1%, 100MW, THICK FILM R-418-1K

R472

R422 RES, 4.7K, 5%, 250MW, METAL

R-376-4.7K

FILM
R432,R433,R434 RES, 1K, 1%, 100MW, THICK FILM R-418-1K
R435,R504,R590,R673,R688,R689,R716,

RES, 10K, 1%, 100MW, THICK FILM R-418-10K

R715

R438,R439,R592,R617,R622,R654,R655,

RES, 10K, 1%, 100MW, THICK FILM R-418-10K

R687

R450 RES, 200K, .1%, 1/10W, METAL

R-263-200K

FILM
R452 RES, 21.93K, .1%, 1/10W, METAL

R-263-21.93K

FILM
R453 RES, 1.82K, .1%, 1/10W, METAL

R-263-1.82K

FILM
R454,R455,R467,R468,R469,R470,R471 RES, 100, .1%, 1/10W, METAL FILM R-263-100

Model 2425 Service Manual Replacement Parts 6-9

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 R-418-1K

R704
R483,R691,R695,R721 RES, 2K, 1%, 100MW, THICK FILM R-418-2K
R490 RES, 205, .1%, 1/10W, METAL FILM R-263-205
R503,R545,R587 RES, 15K, 1%, 100MW, THICK FILM R-418-15K
R508,R509,R506,R507 RES, 150K, 5%, 250MW, METAL

R-376-150K

FILM

R517,R524,R564,R565,R566,R567 RES, 12.1, 1%, 125MW, METAL

R-391-12.1

FILM
R521,R658 RES, 2M, 1%, 100MW, THICK FILM R-418-2M
R525,R526 RES, 1.21K, 1%, 100MW, THICK

R-418-1.21K

FILM
R530,R532,R534,R712 RES, 1K, 1%, 100MW, THICK FILM R-418-1K
R538,R539,R540,R541,R542,R543,R568,

RES, .5, 5%, 1W, METAL FILM R-444-.5

R569

R547,R588 RES, 100K, 1%, 100MW, THICK

R-418-100K

FILM
R553,R554 RES, 75K, 1%, 100MW, THICK FILM R-418-75K
R561,R562,R600,R500,R515,R722 RES, 100K, 1%, 100MW, THICK

R-418-100K

FILM
R570,R571,R573,R581,R705 RES, 249,1%, 100MW, THICK FILM R-418-249
R572,R574,R580,R582 RES, 200K, 1%, 100MW, THICK

R-418-200K

FILM
R575,R579,R614,R615 RES, 2.21K, 1%, 100MW, THICK

R-418-2.21K

FILM
R583,R584,R585,R586 RES, 10, 5%, 125MW, METAL FILM R-375-10
R601,R603,R605,R608,R626,R702,R703 RES, 4.99K, 1%, 100MW, THICK

R-418-4.99K

FILM
R602,R607 RES, 150, 5%, 250MW, METAL

R-376-150

FILM
R609 RES NET TF-245
R610 RES, 1.28M, .1%, 1/8W, METAL

R-176-1.28M

FILM
R611,R621 RES, 475, 1%, 100MW, THICK FILM R-418-475
R612 RES, 5.11K, 1%, 100MW, THICK

R-418-5.11K

FILM