Tektronix 2500 Service Manual

Model 2500

Dual Photodiode Meter

Service Manual

Contains Calibrating and Servicing Information

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, non­rechargeable 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 INSTALLATION,
LOSSES SUSTAINED AS THE RESULT OF INJURY TO ANY PERSON, OR DAMAGE TO PROPERTY.

Keithley Instruments, Inc.

BELGIUM: Keithley Instruments B.V.
CHINA: Keithley Instruments China
FRANCE: Keithley Instruments Sarl
GERMANY: Keithley Instruments GmbH
GREAT BRITAIN: Keithley Instruments Ltd
INDIA: Keithley Instruments GmbH
ITALY: Keithley Instruments s.r.l.
NETHERLANDS: Keithley Instruments B.V.
SWITZERLAND: Keithley Instruments SA
TAIWAN: Keithley Instruments Taiwan

• 28775 Aurora Road • Cleveland, OH 44139 • 440-248-0400 • Fax: [phone] • http://www.keithley.com

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

Yuan Chen Xin Building, Room 705 • 12 Yumin Road, Dewai, Madian • Beijing 100029 • 8610-62022886 • Fax: [phone]

B.P. 60 • 3, allée des Garays • 91122 Palaiseau Cédex • 01 64 53 20 20 • Fax: [phone]

Landsberger Strasse 65 • D-82110 Germering • 089/84 93 07-40 • Fax: [phone]

The Minster • 58 Portman Road • Reading, Berkshire RG30 1EA • 0118-9 57 56 66 • Fax: [phone]
Flat 2B, WILOCRISSA • 14, Rest House Crescent • Bangalore 560 001 • 91-80-509-1320/21 • Fax: [phone]
Viale S. Gimignano, 38 • 20146 Milano • 02/48 30 30 08 • Fax: [phone]
Postbus 559 • 4200 AN Gorinchem • 0183-635333 • Fax: [phone]
Kriesbachstrasse 4 • 8600 Dübendorf • 01-821 94 44 • Fax: [phone]

1 Fl. 85 Po Ai Street • Hsinchu, Taiwan, R.O.C. • 886-3572-9077 • Fax: [phone]

10/99

Model 2500 Dual Photodiode Meter

Service Manual

©2000, Keithley Instruments, Inc.

All rights reserved.

Cleveland, Ohio, U.S.A.

First Printing, August 2000

Document Number: 2500-902-01 Rev. A

Manual Print History

The print history shown below lists the printing dates of all Revisions and Addenda created
for this manual. The Revision Level letter increases alphabetically as the manual undergoes
subsequent 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 Revision of the manual are incorporated into the new Revision of the manual. Each new
Revision includes a revised copy of this print history page.

Revision A (Document Number 2500-902-01).............................................................August 2000

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 the operating information carefully
before using the product.

The types of product users are:

Responsible body

ensuring that the equipment is operated within its specifications and operating limits, and for ensuring
that operators are adequately trained.

Operators

and proper use of the instrument. They must be protected from electric shock and contact with hazardous
live circuits.

Maintenance personnel

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

ucts. Only properly trained service personnel may perform installation and service procedures.

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.

practice is to expect that hazardous voltage is present in any unknown circuit before measuring

Users of this product must be protected from electric shock at all times. The responsible body must en­sure that users are prevented access and/or insulated from every connection point. In some cases, con­nections must be exposed to potential human contact. Product users in these circumstances must be
trained to protect themselves from the risk of electric shock. If the circuit is capable of operating at or
above 1000 volts,

As described in the International Electrotechnical Commission (IEC) Standard IEC 664, digital multi­meter measuring circuits (e.g., Keithley Models 175A, 199, 2000, 2001, 2002, and 2010) are Installation
Category II. All other instruments’ signal terminals are Installation Category I and must not be connect­ed to mains.

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.

For maximum safety, do not touch the product, test cables, or any other instruments while power is ap­plied to the circuit under test. ALWAYS remove power from the entire test system and discharge any
capacitors before: connecting or disconnecting cables or jumpers, installing or removing switching
cards, or making internal changes, such as installing or removing jumpers.

is the individual or group responsible for the use and maintenance of equipment, for

use the product for its intended function. They must be trained in electrical safety procedures

are trained to work on live circuits, and perform safe installations and repairs of prod-

no conductive part of the circuit may be exposed.

perform routine procedures on the product to keep it operating, for example,

A good safety

.

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

WARNING

read the associated information very carefully before performing the indicated procedure.

heading in a manual explains dangers that might result in personal injury or death. Always

The

CAUTION

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.

heading in a manual explains hazards that could damage the instrument. Such damage may

Rev. 10/99

T able of Contents

1 Performance V erification

Introduction ................................................................................ 1-2

Verification test requirements ..................................................... 1-2

Environmental conditions ................................................... 1-2

Warm-up period .................................................................. 1-3

Line power .......................................................................... 1-3

Recommended test equipment ................................................... 1-4

Verification limits ....................................................................... 1-4

Example limits calculation .................................................. 1-5

Restoring factory defaults .......................................................... 1-5

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

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

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

Current measurement accuracy .................................................. 1-6

Voltage bias accuracy ............................................................... 1-10

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

Calibration menu ........................................................................ 2-4

Unlocking calibration ................................................................. 2-5

Unlocking calibration from the front panel ........................ 2-5

Unlocking calibration by remote ........................................ 2-6

Changing the password .............................................................. 2-6

Changing the password from the front panel ...................... 2-6

Changing the password by remote ...................................... 2-6

Resetting the calibration password ............................................. 2-7

Viewing calibration dates and calibration count ........................ 2-7

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

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

Remote error reporting ........................................................ 2-8

Aborting calibration steps .......................................................... 2-8

Front panel calibration ............................................................... 2-8

Remote calibration ................................................................... 2-19

Remote calibration command summary ........................... 2-19

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

3 Routine Maintenance

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

Line voltage selection ................................................................. 3-2

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

4 T roubleshooting

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 ................................................. 4-3

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

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

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

Analog circuits .................................................................... 4-6

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

Digital circuitry ................................................................... 4-9

Troubleshooting ........................................................................ 4-10

Display board checks ........................................................ 4-10

Power supply checks ......................................................... 4-11

Digital circuitry checks ..................................................... 4-12

Analog circuitry checks ..................................................... 4-13

No comm link error .................................................................. 4-14

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

Input board removal .................................................................... 5-4

Mother board removal ................................................................ 5-5

Front panel disassembly ............................................................. 5-6

Removing power components .................................................... 5-6

Power supply module removal ............................................ 5-6

Power module removal ........................................................ 5-6

Power transformer removal ................................................. 5-7

6 Replaceable Parts

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

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

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

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

Component layouts .................................................................... 6-3

A Specifications

Accuracy calculations ............................................................... A-4

Measurement accuracy ....................................................... A-4

Voltage bias accuracy ......................................................... A-4

B Calibration Reference

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

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

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

Current measurement commands .............................................. B-6

Voltage bias commands ............................................................. B-7

Detecting calibration errors ....................................................... B-8

Reading the error queue ..................................................... B-8

Error summary ................................................................... B-8

Status byte EAV (Error Available) bit ................................ B-9

Generating an SRQ on error .............................................. B-9

Detecting calibration step completion ....................................... B-9

Using the *OPC? query ..................................................... B-9

Using the *OPC command ............................................... B-10

Generating an SRQ on calibration complete ................... B-10

C Calibration Program

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 2500 calibration program ........................ C-4

List of Illustrations

1 Performance Verification

Figure 1-1 Connections for channel 1 current verification tests .............. 1-7

Figure 1-2 Connections for channel 2 current verification tests .............. 1-9

Figure 1-3 Connections for channel 1 bias voltage verification tests .... 1-11

Figure 1-4 Connections for channel 2 bias voltage verification tests .... 1-12

2 Calibration

Figure 2-1 Channel 1 voltage calibration connections .......................... 2-11

Figure 2-2 Channel 2 voltage calibration connections .......................... 2-13

Figure 2-3 Channel 1 current calibration connections ........................... 2-16

Figure 2-4 Channel 2 current calibration connections ........................... 2-18

3 Routine Maintenance

Figure 3-1 Model 2500 rear panel ........................................................... 3-3

4 Troubleshooting

Figure 4-1 Overall block diagram ........................................................... 4-5

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

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

Figure 4-4 Digital circuitry block diagram .............................................. 4-9

List of Tables

1 Performance Verification

Table 1-1 Recommended verification equipment .................................. 1-4

Table 1-2 Current measurement verification limits ................................ 1-8

Table 1-3 Bias voltage accuracy limits ................................................ 1-12

2 Calibration

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

Table 2-2 Calibration menu ................................................................... 2-5

Table 2-3 Front panel calibration summary ........................................... 2-9

Table 2-4 Voltage bias calibration values ............................................. 2-11

Table 2-5 Current calibration values .................................................... 2-15

Table 2-6 Remote calibration command summary .............................. 2-20

Table 2-7 Remote calibration step summary ........................................ 2-21

Table 2-8 Channel 1 remote voltage bias calibration summary ........... 2-23

Table 2-9 Channel 2 remote voltage bias calibration summary ........... 2-24

Table 2-10 Channel 1 calibration currents and commands .................... 2-25

Table 2-11 Channel 2 calibration currents and commands .................... 2-27

3 Routine Maintenance

Table 3-1 Power line fuses ..................................................................... 3-3

4 Troubleshooting

Table 4-1 Display board checks ........................................................... 4-10

Table 4-2 Power supply checks ............................................................ 4-11

Table 4-3 Digital circuitry checks ........................................................ 4-12

Table 4-4 Analog circuitry checks ....................................................... 4-13

6 Replaceable Parts

Table 6-1 Mother board parts list ........................................................... 6-3

Table 6-2 Input board parts list .............................................................. 6-9

Table 6-3 Power board parts list .......................................................... 6-10

Table 6-4 Display board parts list ........................................................ 6-10

Table 6-5 Miscellaneous parts list ........................................................ 6-11

B Calibration Reference

Table B-1 Calibration commands .......................................................... B-2

Table B-2 Calibration errors .................................................................. B-8

1

Performance Verification

1-2 Performance Verification Model 2500 Service Manual

Introduction

Use the procedures in this section to verify that Model 2500 Dual Photodiode Meter accu­racy is within the limits stated in the instrument’s one-year accuracy specifications. Per­form these verification procedures:

• Upon receipt of the instrument make sure it was not damaged during shipment.

• Verify that the unit meets factory specifications.

• Determine if calibration is required.

• Follow calibration to make sure it was performed properly.

WARNING

NOTE

The information in this section is intended for qualified service person­nel only. Do not attempt these procedures unless you are qualified to do
so. Some of these procedures may expose you to hazardous voltages
which could cause personal injury or death if contacted. Use standard
safety precautions when working with hazardous voltages.

If the instrument is still under warranty and its performance is outside specified
limits, contact your Keithley representative, or the factory, to determine the cor­rect course of action.

Verification test requirements

Be sure to 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.

Environmental conditions

Conduct performance verification procedures in a test environment with:

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

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

Model 2500 Service Manual Performance Verification 1-3

Warm-up period

Allow the Model 2500 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 50°F (10°C) outside the specified
temperature range.

Allow the test equipment to warm up for the minimum time specified by the manufacturer.

Line power

The Model 2500 requires a line voltage of 100V / 120V / 200V / 240V (depending on rear
panel line frequency setting) and a line frequency of 50 or 60Hz. Verification tests must be
performed within this range. Make sure the line voltage setting seen through the small
window in the rear panel power module is at the required setting. If not, change the setting
as covered in Section 3.

1-4 Performance Verification Model 2500 Service Manual

Recommended test equipment

Table 1-1 summarizes recommended verification equipment and pertinent specifications.

You can use alternate equipment as long as that equipment has specifications at least as
good as 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 2500 specifications.

NOTE

The Calibrator/Source listed in Table 1-1 does not quite meet the recommended
four times better uncertainty for 19µA to 19mA output values. Factory calibra­tion uses a transfer standard technique that yields uncertainties better that 4:1
for all calibration points.

Table 1-1

Recommended verification equipment

Description Manufacturer/Model Specifications

Calibrator/Source Keithley 263 DC Current

1

1.9nA:
19nA:
190nA:

1.9µA:
19µA:
190µA:

1.9mA:
19mA2:

Digital Multimeter Keithley 2001 DC Voltage

3

20V:
200V:

1

90-day accuracy specifications at specified output for passive V/R amps mode except as noted.

2

90-day specifications at 19mA output for active amps mode.

3

90-day full-range accuracy specifications.

4

Ratio between test equipment uncertainty and Model 2500 uncertainty.

±0.068%
±0.068%
±0.04%
±0.03%
±0.03%
±0.03%
±0.03%
±0.04%

±22ppm
±30ppm

Uncertainty

4

Ratio

15:1

6:1

7.6:1

6.75:1

3.4:1

3.4:1

3.4:1

2.6:1

45:1
33:1

Verification limits

The verification limits listed in this section have been calculated using only the
Model 2500 one-year accuracy specifications, and they do not include test equipment
uncertainty. If a particular measurement falls outside the allowable range, recalculate new
limits based on Model 2500 specifications and corresponding test equipment
specifications.

Model 2500 Service Manual Performance Verification 1-5

Example limits calculation

As an example of how verification limits are calculated, assume you are testing the 2mA
range with a 1.9mA input current. Using the Model 2500 one-year accuracy specification
of ±(0.1% of reading + 50nA offset), the calculated reading limits are:

Limits = 1.9mA ± [(1.9mA × 0.1%) + 2µA]
Limits = 1.9mA ± (1.9µA + 2µA)
Limits = 1.9mA ± 3.9µA
Limits = 1.8961mA to 1.9039mA

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 and then press ENTER. The unit then displays:

SAVESETUP MENU

SAVE RESTORE POWERON RESET

3. Select RESET and then press ENTER. The unit displays:

RESET ORIGINAL DFLTS

BENCH GPIB

4. Select BENCH and then press ENTER to restore BENCH defaults.

4

1-6 Performance Verification Model 2500 Service Manual

Performing the verification test procedures

Test summary

• Current measurement accuracy

• Voltage bias accuracy

If the Model 2500 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 fully warmed up and properly connected to the
correct Model 2500 terminals as required.

• Allow signals to settle before making a measurement.

• Do not connect test equipment to the Model 2500 through a scanner, multiplexer,
or other switching equipment.

WARNING

CAUTION

The maximum common-mode voltage (voltage between LO and
chassis ground) is 200V DC. Exceeding this value may cause a shock
hazard.

Maximum signal on OUTPUT connectors is 100V @ 20mA DC.
Maximum signal on INPUT connectors is 20mA. Exceeding these
values may result in damage to the instrument.

Current measurement accuracy

Follow the steps below to verify that Model 2500 current measurement accuracy is within
specified limits. This test involves applying currents from a calibrator and verifying that
Model 2500 current readings are within required limits.

1. With the power off, connect the calibrator to the INPUT CHANNEL 1 triax jack,
as shown in Figure 1-2.

2. Turn on the Model 2500 and calibrator, and allow them to warm up for at least one
hour.

3. Restore front panel (BENCH) defaults as outlined in “Restoring factory defaults.”

Model 2500 Service Manual Performance Verification 1-7

WARNING:

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

CAUTION:

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

4. Press the MSR1 key, then select the Model 2500 2nA range on channel 1 with the
RANGE  key.

5. Select the calibrator passive amps function, and choose the 2nA range.

6. Set the calibrator output to 1.90000nA, and turn the output on.

Figure 1-1

Connections for channel 1 current verification tests

OUTPUT

INPUT

200V
PEAK
100mA
PEAK

COMMON

350V
PEAK

PREAMP OUT

CALIBRATION

ENABLED

DISABLED

EXT

OUTPUT

200V PEAK

TRIAX

IEEE-488 INTERFACE

VOLTAGE

30V MAX

CALIBRATOR COMMON TO D.U.T. COMMON

OUTPUT

LINE

90-110V

180-220V

LINE
FUSE

105-125V

210-250V

SLOWBLOW

1/4A 90-125V

1/8A 180-250V

FOR GUARDED OPERATION CONNECT

ON

EXT

PREAMP

OFF

SOURCE

AMPS
COUL

100%

ON

GUARD

OFF

LINE RATING

50-60Hz AC ONLY

25 VA MAX

EXT

INPUT

PREAMP

OUT

AMPS V/R
COUL V/R

OMMS, VOLTS

COMMON

Triax

Cable

Model 263 Calibrator

Channel 1 INPUT

RATINGS MAX
100V @ 20mA

INPUT

CHANNEL 1

RATINGS MAX
100V @ 20mA

VOLTAGE SOURCE

OUTPUT CHANNEL 1

COMMON

MODE

200V

!

CAT I

VOLTAGE SOURCE

OUTPUT CHANNEL 2

INPUT

CHANNEL 2

MADE IN

U.S.A.

TRIGGER LINK

!

DIGITAL I/O

LINE RATING

50, 60Hz

60 VA MAX

FUSE LINE

630 mAT

(SB)

315 mAT

(SB)

RS-232

100 VAC
120 VAC

220 VAC
240 VAC

120

IEEE-488

(CHANGE IEEE ADDRESS

WITH FRONT PANEL MENU)

Model 2500

1-8 Performance Verification Model 2500 Service Manual

7. Verify that the Model 2500 current reading is within the limits for the 2nA range
shown in Table 1-2.

8. Repeat steps 4 through 7 for the 20nA through 20mA ranges. (Use the calibrator
active amps mode for the 20mA range.)

9. Repeat steps 4 through 8 for negative input currents of the same magnitude.

Table 1-2

Current measurement verification limits

Reading limits*

Model 2500 range Calibrator current

1 year, 65°F to 82°F (18˚C to 28˚C)

2nA 1.90000nA 1.87900 to 1.92100nA

20nA 19.0000nA 18.9220 to 19.0780nA

200nA 190.000nA 189.230 to 190.770nA

2µA 1.90000µA 1.89600 to 1.90400µA

20µA 19.0000µA 18.9610 to 19.0390µA

200µA 190.000µA 189.790 to 190.210µA

2mA 1.90000mA 1.89610 to 1.90390mA

20mA 19.0000mA 18.9790 to 19.0210mA

*Limits do not include calibrator uncertainty.

10. After verifying all ranges on channel 1, repeat the entire procedure for channel 2.
Connect the calibrator to the INPUT CHANNEL 2 jack, and select channel 2 by
pressing MSR2. (See Figure 1-2 for connections.)

Model 2500 Service Manual Performance Verification 1-9

WARNING:

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

CAUTION:

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

Figure 1-2

Connections for channel 2 current verification tests

OUTPUT

INPUT

200V
PEAK
100mA
PEAK

COMMON

350V
PEAK

PREAMP OUT

CALIBRATION

ENABLED

DISABLED

EXT

OUTPUT

200V PEAK

TRIAX

IEEE-488 INTERFACE

VOLTAGE

30V MAX

CALIBRATOR COMMON TO D.U.T. COMMON

OUTPUT

LINE

90-110V

180-220V

LINE
FUSE

105-125V

210-250V

SLOWBLOW

1/4A 90-125V

1/8A 180-250V

FOR GUARDED OPERATION CONNECT

ON

EXT

PREAMP

OFF

SOURCE

AMPS
COUL

100%

ON

GUARD

OFF

LINE RATING

50-60Hz AC ONLY

25 VA MAX

EXT

INPUT

PREAMP

OUT

AMPS V/R
COUL V/R

OMMS, VOLTS

COMMON

Triax

Cable

Model 263 Calibrator

Channel 2 INPUT

RATINGS MAX
100V @ 20mA

INPUT

CHANNEL 1

RATINGS MAX
100V @ 20mA

VOLTAGE SOURCE

OUTPUT CHANNEL 1

COMMON

MODE

200V

!

CAT I

VOLTAGE SOURCE

OUTPUT CHANNEL 2

INPUT

CHANNEL 2

MADE IN

U.S.A.

TRIGGER LINK

!

DIGITAL I/O

LINE RATING

50, 60Hz

60 VA MAX

FUSE LINE

630 mAT

(SB)

315 mAT

(SB)

RS-232

100 VAC
120 VAC

220 VAC
240 VAC

120

IEEE-488

(CHANGE IEEE ADDRESS

WITH FRONT PANEL MENU)

Model 2500

1-10 Performance Verification Model 2500 Service Manual

Voltage bias accuracy

Follow the steps below to verify that Model 2500 bias voltage accuracy is within specified
limits. This test involves setting the bias voltage to specific values and measuring the volt­ages with a DMM.

1. With the power off, connect the digital multimeter to the Model 2500 channel 1
INPUT and OUTPUT jacks, as shown in Figure 1-3. (Connect DMM INPUT HI to
the VOLTAGE SOURCE OUTPUT CHANNEL 1 jack, and connect DMM INPUT
LO to the inner ring (LO) of the INPUT CHANNEL 1 jack.)

2. Turn on the Model 2500 and DMM, and allow them to warm up for at least one
hour.

3. Restore BENCH defaults as covered in “Restoring factory defaults.”

4. Select the multimeter DC volts measuring function, and choose auto-range.

5. Press the SCR1 key, then select the Model 2500 10V bias range on channel 1 with
the RANGE

6. Set the channel 1 source voltage to +10.000V as follows:

• Press the SRC1 key. Note that the EDIT annunciator turns on, and a digit
blinks in the

• Set the source value in one of two ways: (1) key in the value using the numeric
keys, or (2) set the value using the EDIT keys. Use EDIT  and  to place the
cursor on the digit to be changed, and use EDIT  and  to increment or dec­rement the value.

7. Press the OUTPUT key to turn on the output.



key.

Src1:

display field to indicate the unit is in the edit mode.

Model 2500 Service Manual Performance Verification 1-11

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

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

Figure 1-3

Connections for channel 1 bias voltage verification tests

INPUT LO INPUT HI

SENSE

INPUT

Ω 4 WIRE

HI

PREV

DISPLAY

NEXT

POWER

2001 MULTIMETER

DCV ACV DCI ACI Ω2 Ω4

REL TRIG

INFO LOCAL EXIT ENTER

STORE RECALL

CHAN SCAN

FILTER MATH

CONFIG MENU

FREQ TEMP

Model 2001 DMM

Channel 1

INPUT

INPUT

CHANNEL 1

VOLTAGE SOURCE

OUTPUT CHANNEL 1

Channel 1

OUTPUT

RANGE

RANGE

RATINGS MAX
100V @ 20mA

COMMON

MODE

200V

!

CAT I

RATINGS MAX
100V @ 20mA

VOLTAGE SOURCE

OUTPUT CHANNEL 2

AUTO

CHANNEL 2

INPUT

350V
PEAK

INPUTS

FR

FRONT/REAR

CAL

MADE IN

U.S.A.

TRIGGER LINK

1100V

!

PEAK

LO

500V
PEAK

2A 250V

AMPS

LINE RATING

FUSE LINE

630 mAT

(SB)

!

315 mAT

(SB)

Model 2500

(Inner Shield)

DIGITAL I/O

RS-232

50, 60Hz

60 VA MAX

100 VAC
120 VAC

220 VAC
240 VAC

INPUT LO

Triax

Cable

120

IEEE-488

(CHANGE IEEE ADDRESS

WITH FRONT PANEL MENU)

8. Verify the bias voltage output is within the limits for the 10V range shown in

Table 1-3.

9. Repeats steps 6 and 8 for an output voltage of -10.000V.

10. Press the OUTPUT key to turn off the output.

11. Repeat steps 5 through 10 for the 100V bias voltage range with both +100.00V and

-100.00V output voltages.

1-12 Performance Verification Model 2500 Service Manual

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

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

Table 1-3

Bias voltage accuracy limits

Bias voltage limits

Model 2500 bias range Bias voltage

1 year, 65°F to 82°F (18˚C to 28˚C)

010V 10.000V 9.98 to 10.02V

100V 100.00V 99.65 to 100.35V

12. Repeat the entire procedure for channel 2 (Press SRC2 to select channel 2, and
make your connections to the channel 2 INPUT and OUTPUT jacks. See

Figure 1-4).

Figure 1-4

Connections for channel 2 bias voltage verification tests

INPUT LO INPUT HI

SENSE

INPUT

Ω 4 WIRE

HI

PREV

DISPLAY

NEXT

POWER

2001 MULTIMETER

DCV ACV DCI ACI Ω2 Ω4

REL TRIG

INFO LOCAL EXIT ENTER

STORE RECALL

CHAN SCAN

FILTER MATH

CONFIG MENU

FREQ TEMP

Model 2001 DMM

Channel 2 INPUT

INPUT

CHANNEL 1

VOLTAGE SOURCE

OUTPUT CHANNEL 1

Channel 2

OUTPUT

RANGE

RANGE

RATINGS MAX
100V @ 20mA

COMMON

MODE

200V

!

CAT I

RATINGS MAX
100V @ 20mA

VOLTAGE SOURCE

OUTPUT CHANNEL 2

AUTO

CHANNEL 2

INPUT

350V
PEAK

INPUTS

FR

FRONT/REAR

CAL

MADE IN

U.S.A.

TRIGGER LINK

1100V

!

PEAK

LO

500V

PEAK

2A 250V

AMPS

LINE RATING

FUSE LINE

630 mAT

(SB)

!

315 mAT

(SB)

Model 2500

(Inner Shield)

DIGITAL I/O

RS-232

50, 60Hz

60 VA MAX

100 VAC
120 VAC

220 VAC
240 VAC

INPUT LO

Triax

Cable

120

IEEE-488

(CHANGE IEEE ADDRESS

WITH FRONT PANEL MENU)

2

Calibration

2-2 Calibration Model 2500 Service Manual

Introduction

Use the procedures in this section to calibrate the Model 2500 Dual Photodiode Meter.
These procedures require accurate test equipment to supply precise currents and measure
accurate DC voltages. 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 person­nel only. Do not attempt these procedures unless you are qualified to do
so. Some of these procedures may expose you to hazardous voltages.

Environmental conditions

Temperature and relative humidity

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

Warm-up period

Allow the Model 2500 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 50°F (10°C) outside the specified
temperature range.

Allow the test equipment to warm up for the minimum time specified by the manufacturer.

Line power

The Model 2500 requires a line voltage of 100V / 120V / 200V / 240V (depending on line
voltage setting) at line frequency of 50 or 60Hz. The instrument must be calibrated while
operating from a line voltage within this range. Make sure the line voltage setting seen
through the small window in the rear panel power module is at the required setting. If not,
change the setting as covered in Section 3.

Model 2500 Service Manual Calibration 2-3

Calibration considerations

When performing the calibration procedures:

• Make sure the test equipment is properly warmed up and connected to the Model
2500 input or output terminals as required.

• Allow signals to settle before calibrating each point.

• Do not connect test equipment to the Model 2500 through a scanner or other
switching equipment.

• If an error occurs during calibration, the Model 2500 will generate an appropriate
error message. See Appendix B for more information.

WARNING

CAUTION

The maximum common-mode voltage (voltage between LO and
chassis ground) is 200V DC. Exceeding this value may cause a shock
hazard.

Maximum signal on OUTPUT connectors is 100V @ 20mA DC.
Maximum signal on INPUT connectors is 20mA. Exceeding these
values may result in damage to the instrument.

Calibration cycle

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

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 at least as good as those
listed in the table. For optimum calibration accuracy, test equipment specifications should
be at least four times better than corresponding Model 2500 specifications.

2-4 Calibration Model 2500 Service Manual

NOTE

The Calibrator/Source listed in Table 2-1 does not quite meet the recommended
four times better uncertainty for 19µA to 19mA output values. The Model 2500
may not meet factory calibration accuracy specifications on the 20
ranges unless further steps are taken to characterize the corresponding calibra­tor ranges using more accurate equipment. Factory calibration uses a transfer
standard technique that yields uncertainties better than 4:1 for all calibration
points.

Table 2-1

Recommended calibration equipment

Description Manufacturer/Model Specifications

Calibrator/Source Keithley 263 DC Current

1

1.9nA:
19nA:
190nA:

1.9µA:
19µA:
190µA:

1.9mA:
19mA2:

Digital Multimeter Keithley 2001 DC Voltage

3

20V:
200V:

1

90-day accuracy specifications at specified output for passive V/R amps mode except as noted.

2

90-day specifications at 19mA output for active amps mode.

3

90-day full-range accuracy specifications.

4

Ratio between test equipment uncertainty and Model 2500 uncertainty.

±0.068%
±0.068%
±0.04%
±0.03%
±0.03%
±0.03%
±0.03%
±0.04%

±22ppm
±30ppm

µA to 20mA

Uncertainty

4

Ratio

15:1

6:1

7.6:1

6.75:1

3.4:1

3.4:1

3.4:1

2.6:1

45:1
33:1

Calibration menu

Table 2-2 summarizes the main calibration menu selections. To enter the calibration menu,

press the MENU key, select CAL, then press ENTER. Use the EDIT keys to move the cur­sor and scroll through menu selections. Press ENTER to select a MENU item.

Model 2500 Service Manual Calibration 2-5

Table 2-2

Calibration menu

Menu selection Description

UNLOCK Unlock calibration using password (default: 002500).

EXECUTE

V-CAL

CHAN-1
CHAN-2

I-CAL

CHAN-1
CHAN-2

OFFSET

VIEW-DATES View calibration dates.

SAVE Save calibration constants.

LOCK Lock out calibration.

CHANGE-PASSWORD Change calibration password.

Execute calibration steps.
Voltage bias calibration.
Channel 1 voltage bias calibration.
Channel 2 voltage bias calibration.
Current measurement calibration.
Channel 1 current calibration.
Channel 2 current calibration.
Auto-zero input offset for both channels.

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 

SAVE LOCK CHANGE-PASSWORD



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

PASSWORD:

Use , , , , ENTER or EXIT.

3. Use the EDIT  and  keys to select the letter or number, and use the EDIT  and

 arrow keys to choose the position. (Press  for letters;  for numbers.) Enter the

present password on the display. (Front panel default: 002500.)

4. Once the correct password is displayed, press the ENTER key. You can then pro­ceed with the calibration procedure.

2-6 Calibration Model 2500 Service Manual

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 'KI002500'

Changing the password

The default password (002500) may be changed from the front panel or via remote as dis­cussed below.

Changing the password from the front panel

Follow these steps 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 

SAVE LOCK CHANGE-PASSWORD



2. Select UNLOCK then enter the password. (Default: 002500.)

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

New Pwd: 002500

Use , , , , ENTER or EXIT.

4. Using the EDIT 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 pass­word from the ‘KI002500’ remote default to ‘KI_CAL’:

:CAL:PROT:CODE 'KI002500'
: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.

Model 2500 Service Manual Calibration 2-7

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 (002500, front panel; KI002500, remote).

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 and then press ENTER. The Model 2500 will display the
next and last calibration dates and the calibration count as in the following
example:

NEXT CAL: 04/15/2001

Last cal: 04/15/2000 Count: 0001

2-8 Calibration Model 2500 Service Manual

Calibration errors

The Model 2500 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.

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 :SYST:ERR? query. The Model 2500 will
respond with the error number and a text message describing the nature of the error. See
Appendix B for details.

Aborting calibration steps

To abort a calibration step from the front panel, press the EXIT key. To abort a calibration
step via remote, send the :ABORt command.

Front panel calibration

The front panel calibration procedure described below calibrates all functions. Note that
each function and range is separately calibrated, and the procedure must be performed in
the order shown.

Step 1. Prepare the Model 2500 for calibration

1. Turn on the Model 2500 and the calibration equipment, 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 , , , , ENTER or EXIT.

Model 2500 Service Manual Calibration 2-9

3. Use the EDIT  and  keys to select the letter or number, and use the  and 
arrow keys to choose the position. (Press EDIT  for letters;  for numbers.)
Enter the present password on the display. (Front panel default: 002500.)

4. Press ENTER to complete the process.

5. Press EXIT to return to normal display.

Table 2-3

Front panel calibration summary

Function1Calibration step

2

Test connections

OFFSET INPUT offset voltage

calibration

V-CAL

CHAN-1

Voltage bias calibration
Channel 1 calibration
Positive full scale output
Zero output
Negative full scale output

CHAN-2

Channel 2 calibration
Positive full scale output
Zero output
Negative full scale output

I-CAL

CHAN-1

Current calibration
Channel 1 calibration
Positive full scale input
Zero input
Negative full scale input

CHAN-2

Channel 2 calibration
Positive full scale input
Zero input
Negative full scale input

1

CAL EXECUTION menu selections.

2

Steps repeated separately for each range.

Channel 1 and channel 2 INPUT jacks left open (capped).

DMM to channel 1 OUTPUT and INPUT jacks (Figure 2-1)
DMM to channel 1 OUTPUT and INPUT jacks (Figure 2-1)
DMM to channel 1 OUTPUT and INPUT jacks (Figure 2-1)

DMM to channel 2 OUTPUT and INPUT jacks (Figure 2-2)
DMM to channel 2 OUTPUT and INPUT jacks (Figure 2-2)
DMM to channel 2 OUTPUT and INPUT jacks (Figure 2-2)

Calibrator to channel 1 INPUT jack (Figure 2-3)
Calibrator to channel 1 INPUT jack (Figure 2-3)
Calibrator to channel 1 INPUT jack (Figure 2-3)

Calibrator to channel 2 INPUT jack (Figure 2-4)
Calibrator to channel 2 INPUT jack (Figure 2-4)
Calibrator to channel 2 INPUT jack (Figure 2-4)

Step 2. Input offset voltage calibration

1. Install a triax shielding cap on both INPUT jacks.

2. Select OFFSET from the CAL EXECUTION menu, then press ENTER. The unit
will display:

CURRENT OFFSET CAL

Input 0A then press ENTER

3. Press ENTER to complete input voltage calibration.

NOTE This step calibrates offset voltage for both channels.

2-10 Calibration Model 2500 Service Manual

Step 3. Channel 1 voltage source calibration

Follow the steps below to calibrate both channel 1 bias voltage ranges. Table 2-4 summa-
rizes calibration ranges and voltages.

1. Connect the DMM to the Model 2500 channel 1 INPUT and OUTPUT jacks, as
shown in Figure 2-1. (Connect DMM INPUT HI to the VOLTAGE SOURCE
OUTPUT CHANNEL 1 jack; connect DMM INPUT LO to the inner shield of the
INPUT CHANNEL 1 jack.)

2. Select the DMM DC volts function, and enable auto-range.

3. From normal display. Press the Model 2500 SRC1 key, then set the channel 1 volt­age bias source to the 10V range using the RANGE  key.

4. Press the MENU key, select CAL, then press ENTER.

5. Select EXECUTE, then press ENTER to enter the CAL EXECUTION menu.

6. Select V-CAL then press ENTER. The unit will display the following:

V-CAL CHANNEL SELECT

CHAN-1 CHAN-2

7. Select CHAN-1 then press ENTER. The instrument will prompt for +10V
calibration:

1

V-CAL

Press ENTER to Output +10.000 V

8. Press ENTER. The instrument will display the following message:

DMM RDG: 10.0000V

Use , , , , ENTER or EXIT.

9. Note the DMM voltage reading, then use the EDIT keys to adjust the Model 2500
display value to agree with that reading.

10. Press ENTER. The unit will prompt for the 0V calibration point:

11. Press ENTER. The instrument will display the following message:

12. Note the DMM voltage reading, then use the EDIT keys to adjust the Model 2500

13. Press ENTER. The unit will display the prompt for the -10V calibration point:

14. Press ENTER. The instrument will display the following message:

15. Note the DMM voltage reading, then use the EDIT keys to adjust the Model 2500

16. Press EXIT to return to normal display.

1

V-CAL

Press ENTER to Output 00.000V

DMM RDG: 00.00000 V

Use , , , , ENTER or EXIT.

display value to agree with the reading.

1

V-CAL

Press ENTER to Output -10.000V

DMM RDG: -10.00000 V

Use , , , , ENTER or EXIT.

display value to agree with the reading, and press ENTER.

Model 2500 Service Manual Calibration 2-11

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

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

17. Using the appropriate RANGE key, select the 100V bias voltage range.

18. Repeat steps 4 through 15 for the 100V bias voltage range.

Table 2-4

Voltage bias calibration values

Voltage bias range Calibration voltages

10V +10.0000V

0.0000V

-10.0000V

100V +100.000V

0.000V

-100.000V

Figure 2-1

Channel 1 voltage calibration connections

INPUT LO INPUT HI

SENSE

INPUT

Ω 4 WIRE

HI

PREV

DISPLAY

NEXT

POWER

2001 MULTIMETER

DCV ACV DCI ACI Ω2 Ω4

REL TRIG

INFO LOCAL EXIT ENTER

STORE RECALL

CHAN SCAN

FILTER MATH

CONFIG MENU

FREQ TEMP

Model 2001 DMM

Channel 1

INPUT

INPUT

CHANNEL 1

VOLTAGE SOURCE

OUTPUT CHANNEL 1

Channel 1

OUTPUT

RANGE

RANGE

RATINGS MAX

100V @ 20mA

COMMON

MODE

200V

!

CAT I

RATINGS MAX

100V @ 20mA

VOLTAGE SOURCE

OUTPUT CHANNEL 2

AUTO

CHANNEL 2

INPUT

350V

PEAK

INPUTS

FR

FRONT/REAR

CAL

MADE IN

U.S.A.

TRIGGER LINK

1100V

!

PEAK

LO

500V
PEAK

2A 250V

AMPS

LINE RATING

FUSE LINE

630 mAT

(SB)

!

315 mAT

(SB)

Model 2500

(Inner Shield)

DIGITAL I/O

RS-232

50, 60Hz

60 VA MAX

100 VAC
120 VAC

220 VAC
240 VAC

INPUT LO

Triax

Cable

120

IEEE-488

(CHANGE IEEE ADDRESS

WITH FRONT PANEL MENU)

2-12 Calibration Model 2500 Service Manual

Step 4. Channel 2 voltage source calibration

Follow the steps below to calibrate both channel 2 bias voltage ranges. Table 2-4 summa-
rizes calibration ranges and voltages.

1. Connect the DMM to the Model 2500 channel 2 INPUT and OUTPUT jacks, as
shown in Figure 2-2. (Connect DMM INPUT HI to the VOLTAGE SOURCE
OUTPUT CHANNEL 2 jack; connect DMM INPUT LO to the inner shield of the
INPUT CHANNEL 2 jack.)

2. Select the DMM DC volts function, and enable auto-range.

3. From normal display, press the Model 2500 SRC2 key, then set the channel 2 volt­age bias source to the 10V range using the RANGE  key.

4. Press the MENU key, select CAL, then press ENTER.

5. Select EXECUTE, then press ENTER to enter the CAL EXECUTION menu.

6. Select V-CAL then press ENTER. The unit will display the following:

V-CAL CHANNEL SELECT

CHAN-1 CHAN-2

7. Select CHAN-2, then press ENTER. The instrument will prompt for +10V
calibration:

2

V-CAL

Press ENTER to Output +10.000 V

8. Press ENTER. The instrument will display the following message:

DMM RDG: 10.0000V

Use , , , , ENTER or EXIT.

9. Note the DMM voltage reading, then use the EDIT keys to adjust the Model 2500
display value to agree with that reading.

10. Press ENTER. The unit will prompt for the 0V calibration point:

11. Press ENTER. The instrument will display the following message:

12. Note the DMM voltage reading, then use the EDIT keys to adjust the Model 2500

13. Press ENTER. The unit will display the prompt for the -10V calibration point:

2

V-CAL

Press ENTER to Output 00.000V

DMM RDG: 00.00000 V

Use , , , , ENTER or EXIT.

display value to agree with the reading.

2

V-CAL

Press ENTER to Output -10.000V

Model 2500 Service Manual Calibration 2-13

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

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

14. Press ENTER. The instrument will display the following message:

DMM RDG: -10.00000 V

Use , , , , ENTER or EXIT.

15. Note the DMM voltage reading, then use the EDIT keys to adjust the Model 2500
display value to agree with the reading and press ENTER.

16. Press EXIT to return to normal display.

17. Using the appropriate RANGE key, select the 100V bias voltage range.

18. Repeat steps 4 through 15 for the 100V bias voltage range.

Figure 2-2

Channel 2 voltage calibration connections

INPUT LO INPUT HI

SENSE

INPUT

Ω 4 WIRE

HI

PREV

DISPLAY

NEXT

POWER

2001 MULTIMETER

DCV ACV DCI ACI Ω2 Ω4

REL TRIG

INFO LOCAL EXIT ENTER

STORE RECALL

CHAN SCAN

FILTER MATH

CONFIG MENU

FREQ TEMP

Model 2001 DMM

Channel 2 INPUT

INPUT

CHANNEL 1

VOLTAGE SOURCE

OUTPUT CHANNEL 1

Channel 2

OUTPUT

RANGE

RANGE

RATINGS MAX

100V @ 20mA

COMMON

MODE

200V

!

CAT I

RATINGS MAX

100V @ 20mA

VOLTAGE SOURCE

OUTPUT CHANNEL 2

AUTO

CHANNEL 2

INPUT

350V

PEAK

INPUTS

FR

FRONT/REAR

CAL

MADE IN

U.S.A.

TRIGGER LINK

1100V

!

PEAK

LO

500V
PEAK

2A 250V

AMPS

LINE RATING

FUSE LINE

630 mAT

(SB)

!

315 mAT

(SB)

Model 2500

(Inner Shield)

DIGITAL I/O

RS-232

50, 60Hz

60 VA MAX

100 VAC
120 VAC

220 VAC
240 VAC

INPUT LO

Triax

Cable

120

IEEE-488

(CHANGE IEEE ADDRESS

WITH FRONT PANEL MENU)

2-14 Calibration Model 2500 Service Manual

Step 5. Channel 1 current calibration

Follow the steps below to calibrate all current ranges of channel 1. Table 2-5 summarizes
calibration ranges and currents.

1. Connect the calibrator to the Model 2500 INPUT CHANNEL 1 jack, as shown in

Figure 2-3.

2. Select the calibrator passive V/R amps function. Set the calibrator output to
+1.90000nA and turn on the output.

3. Press the Model 2500 MSR1 key, then set channel 1 to the 2nA current range using
the RANGE  key.

4. Press the MENU key, select CAL, then press ENTER.

5. Select EXECUTE, then press ENTER to enter the CAL EXECUTION menu.

6. Select I-CAL then press ENTER. The unit will display the following:

I -CAL CHANNEL SELECT

CHAN-1 CHAN-2

7. Select CHAN-1 then press ENTER. The instrument will prompt for the positive
full-range current:

I (+FS)1 = +2.000000nA

Use , , , , ENTER or EXIT.

8. Set the calibrator current to +1.90000nA.

9. Use the EDIT keys to adjust the Model 2500 display value to agree with the cali­brator current.

10. Press ENTER. The unit will prompt for the zero current:

I (0)1 = +0.000000nA

Use , , , , ENTER or EXIT.

11. Set the calibrator current to 0nA then press ENTER. The instrument will prompt
for the negative full-range current:

I(-FS)1 = -2.000000nA

Use , , , , ENTER or EXIT.

12. Set the calibrator current to -1.90000nA.

13. Adjust the displayed current to agree with the calibrator current, then press the
Model 2500 ENTER key to complete calibration of the present range.

14. Press EXIT to return to normal display.

15. Repeat steps 3 through 14 for the 20nA to 20mA ranges, using Table 2-5 as a
guide. Be sure to set the Model 2500 to the correct range using the RANGE  and

 keys, and use the corresponding calibrator currents for each range.

NOTE Use the calibrator active amps mode for the 20mA range to assure best

accuracy.

Model 2500 Service Manual Calibration 2-15

Table 2-5

Current calibration values

Current range Calibration currents

2nA +1.90000nA

0.0000nA

-1.90000nA

20nA +19.0000nA

0.0000nA

-19.0000nA

200nA +190.000nA

0.000nA

-190.000nA

2µA +1.90000µA

0.00000µA

-1.90000µA

20µA +19.0000µA

0.0000µA

-19.0000µA

200µA +190.000µA

0.000µA

-190.000µA

2mA +1.90000mA

0.00000mA

-1.90000mA

20mA +19.0000mA

0.0000mA

-19.0000mA

2-16 Calibration Model 2500 Service Manual

WARNING:

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

CAUTION:

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

Figure 2-3

Channel 1 current calibration connections

OUTPUT

INPUT

200V
PEAK
100mA
PEAK

COMMON

350V
PEAK

PREAMP OUT

CALIBRATION

ENABLED

DISABLED

EXT

OUTPUT

200V PEAK

TRIAX

IEEE-488 INTERFACE

LINE

VOLTAGE

30V MAX

FOR GUARDED OPERATION CONNECT

CALIBRATOR COMMON TO D.U.T. COMMON

OUTPUT

90-110V

180-220V

LINE
FUSE

105-125V

210-250V

SLOWBLOW

1/4A 90-125V

1/8A 180-250V

ON

EXT

OFF

ON

GUARD

OFF

PREAMP

SOURCE

AMPS
COUL

100%

LINE RATING

50-60Hz AC ONLY

25 VA MAX

EXT

INPUT

PREAMP

OUT

AMPS V/R
COUL V/R

OMMS, VOLTS

COMMON

Triax

Cable

Model 263 Calibrator

Channel 1 INPUT

RATINGS MAX

100V @ 20mA

INPUT

CHANNEL 1

RATINGS MAX

100V @ 20mA

VOLTAGE SOURCE

OUTPUT CHANNEL 1

COMMON

MODE

200V

CHANNEL 2

!

CAT I

VOLTAGE SOURCE

OUTPUT CHANNEL 2

INPUT

MADE IN

U.S.A.

TRIGGER LINK

!

DIGITAL I/O

LINE RATING

50, 60Hz

60 VA MAX

FUSE LINE

630 mAT

(SB)

315 mAT

(SB)

RS-232

100 VAC
120 VAC

220 VAC
240 VAC

120

IEEE-488

(CHANGE IEEE ADDRESS

WITH FRONT PANEL MENU)

Model 2500

Model 2500 Service Manual Calibration 2-17

Step 6. Channel 2 current calibration

Follow the steps below to calibrate all channel 2 current ranges. Table 2-5 summarizes cal-
ibration ranges and currents.

1. Connect the calibrator to the Model 2500 INPUT CHANNEL 2 jack, as shown in

Figure 2-4.

2. Select the calibrator passive V/R amps function. Set the calibrator output to
+1.90000nA, and turn on the output.

3. Press the Model 2500 MSR2 key, then set channel 2 to the 2nA current range using
the RANGE  key.

4. Press the MENU key, select CAL, then press ENTER.

5. Select EXECUTE, then press ENTER to enter the CAL EXECUTION menu.

6. Select I-CAL then press ENTER. The unit will display the following:

I -CAL CHANNEL SELECT

CHAN-1 CHAN-2

7. Select CHAN-2 then press ENTER. The instrument will prompt for the positive
full-range current:

I (+FS)2 = +2.000000nA

Use , , , , ENTER or EXIT.

8. Set the calibrator current to +1.90000nA.

9. Use the EDIT keys to adjust the Model 2500 display value to agree with the cali­brator current.

10. Press ENTER. The unit will prompt for the zero current:

I (0)2 = +0.000000nA

Use , , , , ENTER or EXIT.

11. Set the calibrator current to 0nA then press ENTER. The instrument will prompt
for the negative full-range current:

I(-FS)2 = -2.000000nA

Use , , , , ENTER or EXIT.

12. Set the calibrator current to -1.90000nA.

13. Adjust the displayed current to agree with the calibrator current, then press the
Model 2500 ENTER key to complete calibration of the present range.

14. Press EXIT to return to normal display.

15. Repeat steps 3 through 14 for the 20nA to 20mA ranges, using Table 2-5 as a
guide. Be sure to set the Model 2500 to the correct range using the RANGE  and



keys, and use the corresponding calibrator currents for each range.

2-18 Calibration Model 2500 Service Manual

WARNING:

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

CAUTION:

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

Figure 2-4

Channel 2 current calibration connections

OUTPUT

INPUT

200V
PEAK
100mA
PEAK

COMMON

350V
PEAK

PREAMP OUT

CALIBRATION

ENABLED

DISABLED

EXT

OUTPUT

200V PEAK

TRIAX

IEEE-488 INTERFACE

LINE

VOLTAGE

30V MAX

FOR GUARDED OPERATION CONNECT

CALIBRATOR COMMON TO D.U.T. COMMON

OUTPUT

90-110V

180-220V

LINE
FUSE

105-125V

210-250V

SLOWBLOW

1/4A 90-125V

1/8A 180-250V

ON

EXT

OFF

ON

GUARD

OFF

PREAMP

SOURCE

AMPS
COUL

100%

LINE RATING

50-60Hz AC ONLY

25 VA MAX

EXT

INPUT

PREAMP

OUT

AMPS V/R
COUL V/R

OMMS, VOLTS

COMMON

Triax

Cable

Model 263 Calibrator

Channel 2 INPUT

RATINGS MAX

100V @ 20mA

INPUT

CHANNEL 1

RATINGS MAX

100V @ 20mA

VOLTAGE SOURCE

OUTPUT CHANNEL 1

COMMON

MODE

200V

CHANNEL 2

!

CAT I

VOLTAGE SOURCE

OUTPUT CHANNEL 2

INPUT

MADE IN

U.S.A.

TRIGGER LINK

!

DIGITAL I/O

LINE RATING

50, 60Hz

60 VA MAX

FUSE LINE

630 mAT

(SB)

315 mAT

(SB)

RS-232

100 VAC
120 VAC

220 VAC
240 VAC

120

IEEE-488

(CHANGE IEEE ADDRESS

WITH FRONT PANEL MENU)

Model 2500

Model 2500 Service Manual Calibration 2-19

Step 7. Enter calibration dates and save calibration

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

Step 8. Lock out calibration.

1. From the CALIBRATION menu, select SAVE, and then press ENTER. The unit
will prompt you for the calibration date:

CAL DATE: 02/15/2000

Use , , , , ENTER or EXIT.

2. Using the EDIT keys, change the displayed date to today’s date and press the
ENTER key. Press ENTER again to confirm the date.

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

NEXT CAL: 02/15/2001

Use , , , , ENTER or EXIT.

4. Set the calibration due date to the desired value and press ENTER. Press ENTER
again to confirm the date.

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

CALIBRATION COMPLETE

Press ENTER to save; EXIT to abort

6. Press ENTER to save the calibration data (or press EXIT to abort without saving
calibration data.)

Step 8. Lock out calibration

From the CAL EXECUTION menu select LOCK, and press ENTER to lock out calibra­tion. Press EXIT to return to normal display.

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 command summary

Table 2-6 summarizes only those remote calibration commands used in this section.

2-20 Calibration Model 2500 Service Manual

NOTE For a detailed description of all calibration commands and queries, refer to

Appendix B.

Table 2-6

Remote calibration command summary

Command Description

:CALibration

:PROTected

:CODE ‘<password>’
:SENSe[1] <NRf>
:SENSe2 <NRf>
:SOURce[1] <NRf>

:OFFSet

:SOURce2 <NRf>

:OFFSet
:DATE <yyyy>,<mm>,<dd>
:NDUE <yyyy>,<mm>,<dd>
:SAVE
:LOCK

Remote calibration procedure

Step 1. Prepare the Model 2500 for calibration

1. With the power off, connect the Model 2500 to the controller IEEE-488 interface or

2. Turn on the Model 2500 and the test equipment, and allow them to warm up for at

3. If you are using the IEEE-488 interface, make sure the primary address of the

Calibration subsystem.
Calibration commands protected by password.
Unlock calibration. (Default password: KI002500.)
Calibrate active range of channel 1 current measurement.
Calibrate active range of channel 2 current measurement.
Calibrate active channel 1 voltage bias range.
Calibrate channel 1 input voltage offset.
Calibrate active channel 2 voltage bias range.
Calibrate channel 2 input voltage offset.
Program calibration year, month, day.
Program calibration due year, month, day.
Save calibration data in EEPROM.
Lock out calibration.

RS-232 port using a shielded interface cable.

least one hour before performing calibration.

Model 2500 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.)

Model 2500 Service Manual Calibration 2-21

4. Send the following command to unlock calibration:

:CAL:PROT:CODE 'KI002500'

5. Table 2-7 summarizes the various calibration steps and associated commands,
which are covered in more detail throughout the procedure.

Table 2-7

Remote calibration step summary

Calibrated
function Calibration command* Test connections

Input offset
(ch. 1)

Voltage
bias (ch. 1)

Input offset
(ch. 2)

Voltage
bias (ch. 2)

Current
(ch. 1)

Current
(ch. 2)

*Procedure repeated separately for each range. Voltage <Range> = 10 or 100. Current <Range> = 2e-9 to 20e-3 in decade steps.

:CAL:PROT:SOUR1:OFFS

:OUTP1 ON
:SOUR1:VOLT:RANG <Range>
:SOUR1:VOLT <+FS>
:CAL:PROT:SOUR1 <DMM_Reading>
:SOUR1:VOLT 0
:CAL:PROT:SOUR1 <DMM_Reading>
:SOUR1:VOLT <-FS>
:CAL:PROT:SOUR1 <DMM_Reading>
:OUTP1 OFF
:OUTP2 ON
:SOUR2:VOLT:RANG <Range>
:SOUR2:VOLT <+FS>

:CAL:PROT:SOUR2:OFFS

:CAL:PROT:SOUR2 <DMM_Reading>
:SOUR2:VOLT 0
:CAL:PROT:SOUR2 <DMM_Reading>
:SOUR2:VOLT <-FS>
:CAL:PROT:SOUR2 <DMM_Reading>
:OUTP2 OFF

:SENS1:CURR:RANG <Range>
:CAL:PROT:SENS1 <+FS_current>
:CAL:PROT:SENS1 <Zero_current>
:CAL:PROT:SENS1 <-FS_current>
:SENS2:CURR:RANG <Range>

:CAL:PROT:SENS2 <+FS_current>
:CAL:PROT:SENS2 <Zero_current>
:CAL:PROT:SENS2 <-FS_current>

Triax shield cap on channel 1 INPUT jack.

DMM to channel 1 OUTPUT/INPUT LO (

DMM to channel 1 OUTPUT/INPUT LO (

DMM to channel 1 OUTPUT/INPUT LO (

DMM to channel 2 OUTPUT/INPUT LO (

Triax shield cap on channel 2 INPUT jack.

DMM to channel 2 OUTPUT/INPUT LO (

DMM to channel 2 OUTPUT/INPUT LO (

Calibrator to channel 1 INPUT (
Calibrator to channel 1 INPUT (
Calibrator to channel 1 INPUT (

Calibrator to channel 2 INPUT (
Calibrator to channel 2 INPUT (
Calibrator to channel 2 INPUT (

Figure 2-3)
Figure 2-3)
Figure 2-3)

Figure 2-4)
Figure 2-4)
Figure 2-4)

Figure 2-1)

Figure 2-1)

Figure 2-1)

Figure 2-2)

Figure 2-2)

Figure 2-2)

2-22 Calibration Model 2500 Service Manual

Step 2. Channel 1 input offset voltage calibration

1. Install a triax shielding cap on the channel 1 INPUT jack.

2. Send this command to calibrate channel 1 input offset voltage:

:CAL:PROT:SOUR1:OFFS

Step 3. Channel 1 voltage source calibration

Follow these steps to calibrate the channel 1 voltage bias source. Table 2-8 summarizes
channel 1 calibration voltages and commands.

1. Connect the DMM to the Model 2500 channel 1 OUTPUT and INPUT LO termi­nals, as shown in Figure 2-1.

2. Select the DMM DC voltage function and enable auto-range.

3. Send this command to turn on the channel 1 output:

:OUTP1 ON

4. Send the following command to select the channel 1 10V voltage bias range:

:SOUR1:VOLT:RANG 10

5. Send the following command to output +10V:

:SOUR1:VOLT 10

6. Note and record the DMM reading, and send that value as the parameter for the fol­lowing command:

:CAL:PROT:SOUR1 <DMM_Reading>

For example, if the DMM reading is 9.95V, the correct command is:

:CAL:PROT:SOUR1 9.95

7. Send the following command to output 0V:

:SOUR1:VOLT 0

8. Note and record the DMM reading, and send that value as the parameter for the fol­lowing command:

:CAL:PROT:SOUR1 <DMM_Reading>

9. Send the following command to output -10V:

:SOUR1:VOLT -10

10. Note and record the DMM reading, and send that value as the parameter for the fol­lowing command:

:CAL:PROT:SOUR1 <DMM_Reading>

11. Repeat steps 4 through 10 for the 100V range using Table 2-8 as a guide. Be sure
to:

• Select the 100V range using the :SOUR1:VOLT:RANG 100 command.

• Send the ±100V source values where appropriate.

12. Send this command to turn off the channel 1 output:

:OUTP1 OFF

Model 2500 Service Manual Calibration 2-23

Table 2-8

Channel 1 remote voltage bias calibration summary

Voltage bias
range

10V

100V

Calibration
voltages Calibration commands

:OUTP1 ON
:SOUR1:VOLT:RANG 10

+10V

0V

-10V

+100V

0V

-100V

:SOUR1:VOLT 10
:CAL:PROT:SOUR1 <DMM_Reading>
:SOUR1:VOLT 0
:CAL:PROT:SOUR1 <DMM_Reading>
:SOUR1:VOLT -10
:CAL:PROT:SOUR1 <DMM_Reading>

:SOUR1:VOLT:RANG 100
:SOUR1:VOLT 100
:CAL:PROT:SOUR1 <DMM_Reading>
:SOUR1:VOLT 0
:CAL:PROT:SOUR1 <DMM_Reading>
:SOUR1:VOLT -100
:CAL:PROT:SOUR1 <DMM_Reading>
:OUTP1 OFF

Step 4. Channel 2 input offset voltage calibration

1. Install a triax shielding cap on the channel 2 INPUT jack.

2. Send this command to calibrate channel 2 input offset voltage:

:CAL:PROT:SOUR2:OFFS

Step 5. Channel 2 voltage source calibration

Follow these steps to calibrate the channel 2 voltage bias source. Table 2-9 summarizes
channel 1 calibration voltages and commands.

1. Connect the DMM to the Model 2500 channel 2 OUTPUT and INPUT LO termi­nals, as shown in Figure 2-2.

2. Select the DMM DC voltage function, and enable auto-range.

3. Send this command to turn on the channel 2 output:

:OUTP2 ON

4. Send the following command to select the channel 2 10V voltage bias range:

:SOUR2:VOLT:RANG 10

5. Send the following command to output +10V:

:SOUR2:VOLT 10

2-24 Calibration Model 2500 Service Manual

6. Note and record the DMM reading, and send that value as the parameter for the fol­lowing command:

:CAL:PROT:SOUR2 <DMM_Reading>

7. Send the following command to output 0V:

:SOUR2:VOLT 0

8. Note and record the DMM reading, and send that value as the parameter for the fol­lowing command:

:CAL:PROT:SOUR2 <DMM_Reading>

9. Send the following command to output -10V:

:SOUR2:VOLT -10

10. Note and record the DMM reading, and send that value as the parameter for the fol­lowing command:

:CAL:PROT:SOUR2 <DMM_Reading>

11. Repeat steps 4 through 10 for the 100V range using Table 2-9 as a guide. Be sure
to:

• Select the 100V range using the :SOUR2:VOLT:RANG 100 command.

• Send the ±100V source values where appropriate.

12. Send this command to turn off the channel 1 output:

:OUTP2 OFF

Table 2-9

Channel 2 remote voltage bias calibration summary

Voltage bias
range

Calibration
voltages Calibration commands

:OUTP2 ON

10V

+10V

:SOUR2:VOLT:RANG 10
:SOUR2:VOLT 10
:CAL:PROT:SOUR2 <DMM_Reading>

0V

:SOUR2:VOLT 0
:CAL:PROT:SOUR2 <DMM_Reading>

-10V

:SOUR2:VOLT -10
:CAL:PROT:SOUR2 <DMM_Reading>

100V

+100V

:SOUR2:VOLT:RANG 100
:SOUR2:VOLT 100
:CAL:PROT:SOUR2 <DMM_Reading>

0V

:SOUR2:VOLT 0
:CAL:PROT:SOUR2 <DMM_Reading>

-100V

:SOUR2:VOLT -100
:CAL:PROT:SOUR2 <DMM_Reading>
:OUTP2 OFF

Model 2500 Service Manual Calibration 2-25

Step 6. Channel 1 current calibration

Follow these steps to calibrate channel 1 current measurements. Table 2-10 summarizes
channel 1 calibration currents and commands.

Table 2-10

Channel 1 calibration currents and commands

Current range Calibration currents Calibration commands

2nA

20nA

200nA

2µA

20µA

200µA

2mA

20mA

+1.90000nA

0.00000nA

-1.90000nA

+19.0000nA

0.0000nA

-19.0000nA

+190.000nA

0.000nA

-190.000nA

+1.90000µA

0.00000µA

-1.90000µA

+19.0000µA

0.0000µA

-19.0000µA

+190.000µA

0.000µA

-190.000µA

+1.90000mA

0.0000mA

-1.90000mA

+19.0000mA

0.0000mA

-19.0000mA

:SENS1:CURR:RANG 2e-9
:CAL:PROT:SENS1 1.9e-9
:CAL:PROT:SENS1 0
:CAL:PROT:SENS1 -1.9e-9

:SENS1:CURR:RANG 2e-8
:CAL:PROT:SENS1 1.9e-8
:CAL:PROT:SENS1 0
:CAL:PROT:SENS1 -1.9e-8

:SENS1:CURR:RANG 2e-7
:CAL:PROT:SENS1 1,9e-7
:CAL:PROT:SENS1 0
:CAL:PROT:SENS1 -1.9e-7

:SENS1:CURR:RANG 2e-6
:CAL:PROT:SENS1 1.9e-6
:CAL:PROT:SENS1 0
:CAL:PROT:SENS1 -1.9e-6

:SENS1:CURR:RANG 2e-5
:CAL:PROT:SENS1 1.9e-5
:CAL:PROT:SENS1 0
:CAL:PROT:SENS1 -1.9e-5

:SENS1:CURR:RANG 2e-4
:CAL:PROT:SENS1 1.9e-4
:CAL:PROT:SENS1 0
:CAL:PROT:SENS1 -1.9e-4

:SENS1:CURR:RANG 2e-3
:CAL:PROT:SENS1 1.9e-3
:CAL:PROT:SENS1 0
:CAL:PROT:SENS1 -1.9e-3

:SENS1:CURR:RANG 2e-2
:CAL:PROT:SENS1 1.9e-2
:CAL:PROT:SENS1 0
:CAL:PROT:SENS1 -1.9e-2

2-26 Calibration Model 2500 Service Manual

1. Connect the calibrator to the Model 2500 INPUT CHANNEL 1 jack, as shown in

Figure 2-3.

2. Select the calibrator passive V/R amps function. Set the output current to

1.90000nA, and turn on the calibrator output.

3. Send the following command to select the channel 1 2nA range:

:SENS1:CURR:RANG 2e-9

4. Send the following command to calibrate the positive full-range current point:

:CAL:PROT:SENS1 1.9e-9

5. Set the calibrator current output to 0nA.

6. Send the following command to calibrate the zero current point:

:CAL:PROT:SENS1 0

7. Set the calibrator current to -1.90000nA.

8. Send the following command to calibrate the negative full-range current point:

:CAL:PROT:SENS1 -1.9e-9

9. Repeat steps 3 through 8 for the 20nA to 20mA ranges using Table 2-10 as a guide.
Be sure to:

• Select the appropriate range using the :SENS1:CURR:RANG <Range>
command.

• Send the appropriate calibration current values with the :CAL:PROT:SENS1
<Current> command.

• Be sure to use the calibrator active amps mode for the 20mA range.

Step 7. Channel 2 current calibration

Follow these steps to calibrate channel 2 current measurements. Table 2-11 summarizes
channel 2 calibration currents and commands.

1. Connect the calibrator to the Model 2500 INPUT CHANNEL 2 jack, as shown in

Figure 2-4.

2. Select the calibrator passive V/R amps function. Set the output current to

1.90000nA, and turn on the calibrator output.

3. Send the following command to select the channel 2 2nA range:

:SENS2:CURR:RANG 2e-9

4. Send the following command to calibrate the positive full-range current point:

:CAL:PROT:SENS2 1.9e-9

5. Set the calibrator current to 0nA.

6. Send the following command to calibrate the zero current point:

:CAL:PROT:SENS2 0

7. Set the calibrator current to -1.90000nA.

8. Send the following command to calibrate the negative full-range current point:

:CAL:PROT:SENS2 -1.9e-9

Model 2500 Service Manual Calibration 2-27

9. Repeat steps 3 through 8 for the 20nA to 20mA ranges using Table 2-11 as a guide.
Be sure to:

• Select the appropriate range using the :SENS2:CURR:RANG <Range>
command.

• Send the appropriate calibration current values with the :CAL:PROT:SENS2
<Current> command.

• Use the calibrator active amps mode for the 20mA range.

Table 2-11

Channel 2 calibration currents and commands

Current range Calibration currents Calibration commands

2nA

20nA

200nA

2µA

20µA

200µA

2mA

20mA

+1.90000nA

0.0000nA

-1.90000nA

+19.0000nA

0.0000nA

-19.0000nA

+190.000nA

0.0000nA

-190.000nA

+1.90000µA

0.00000µA

-1.90000µA

+19.0000µA

0.00000µA

-19.0000µA

+190.000µA

0.0000µA

-190.000µA

+1.90000mA

0.0000mA

-1.90000mA

+19.0000mA

0.0000mA

-19.0000mA

:SENS2:CURR:RANG 2e-9
:CAL:PROT:SENS2 1.9e-9
:CAL:PROT:SENS2 0
:CAL:PROT:SENS2 -1.9e-9

:SENS2:CURR:RANG 2e-8
:CAL:PROT:SENS2 1.9e-8
:CAL:PROT:SENS2 0
:CAL:PROT:SENS2 -1.9e-8

:SENS2:CURR:RANG 2e-7
:CAL:PROT:SENS2 1.9e-7
:CAL:PROT:SENS2 0
:CAL:PROT:SENS2 -1.9e-7

:SENS2:CURR:RANG 2e-6
:CAL:PROT:SENS2 1.9e-6
:CAL:PROT:SENS2 0
:CAL:PROT:SENS2 -1.9e-6

:SENS2:CURR:RANG 2e-5
:CAL:PROT:SENS2 1.9e-5
:CAL:PROT:SENS2 0
:CAL:PROT:SENS2 -1.9e-5

:SENS2:CURR:RANG 2e-4
:CAL:PROT:SENS2 1.9e-4
:CAL:PROT:SENS2 0
:CAL:PROT:SENS2 -1.9e-4

:SENS2:CURR:RANG 2e-3
:CAL:PROT:SENS2 1.9e-3
:CAL:PROT:SENS2 0
:CAL:PROT:SENS2 -1.9e-3

:SENS2:CURR:RANG 2e-2
:CAL:PROT:SENS2 1.9e-2
:CAL:PROT:SENS2 0
:CAL:PROT:SENS2 -1.9e-2

2-28 Calibration Model 2500 Service Manual

Step 8. Program calibration dates

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

:CAL:PROT:DATE <yyyy>, <mm>, <dd> (Calibration date)
:CAL:PROT:NDUE <yyyy>, <mm>, <dd> (Next calibration due date)

Note that the year, month, and date must be separated by commas.

Step 9. 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.

Step 10. Lock out calibration

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

:CAL:PROT:LOCK

3

Routine Maintenance

3-2 Routine Maintenance Model 2500 Service Manual

Introduction

The information in this section deals with routine type maintenance that can be performed
by the operator and includes information on line voltage selection and line fuse
replacement.

Line voltage selection

WARNING Disconnect the line cord at the rear panel and remove all test leads

connected to the instrument before changing the line voltage.

The Model 2500 operates from a line voltage in the range of 100V / 120V / 220V / 240V,
±10% at a frequency of 50 or 60Hz. Before plugging in the unit, make sure the line voltage
setting seen through the small window in the power module (Figure 3-1) is correct for the
line voltage in your area.

WARNING Operating the instrument on an incorrect line voltage may cause dam-

age, possibly voiding the warranty.

If the voltage setting is not correct, change it as outlined below.

1. Pry the small tab that secures the fuse holder to the power module, then remove the
fuse holder.

2. Pull out and rotate the fuse carrier to the correct line voltage setting, then install it
in the fuse holder. Make sure the line voltage shown in the window is correct. Also
make sure the fuse rating for the expected line voltage is correct. (See “Line fuse
replacement.”)

3. Reinstall the fuse holder in the power module, making sure it is seated fully.

Line fuse replacement

WARNING Disconnect the line cord at the rear panel and remove all test leads

connected to the instrument before replacing the line fuse.

The power line fuse is accessible from the rear panel and is integral with the AC power
module (Figure 3-1).

Model 2500 Service Manual Routine Maintenance 3-3

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

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

Figure 3-1

Model 2500 rear panel

Model 2500

RATINGS MAX

100V @ 20mA

INPUT

CHANNEL 1

RATINGS MAX

100V @ 20mA

VOLTAGE SOURCE

OUTPUT CHANNEL 1

COMMON

MODE

200V

CHANNEL 2

!

CAT I

VOLTAGE SOURCE

OUTPUT CHANNEL 2

INPUT

MADE IN

U.S.A.

TRIGGER LINK

!

DIGITAL I/O

LINE RATING

50, 60Hz

60 VA MAX

FUSE LINE

630 mAT

(SB)

315 mAT

(SB)

RS-232

100 VAC
120 VAC

220 VAC
240 VAC

120

IEEE-488

(CHANGE IEEE ADDRESS

WITH FRONT PANEL MENU)

Line Voltage

Line Fuse

Setting

Perform the following steps to replace the line fuse:

1. Using a small flat-blade screwdriver, carefully release the locking tab that secures
the fuse carrier to the power module.

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

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

Table 3-1.

3. Reinstall the fuse carrier, pushing it in firmly until it locks into place.

NOTE If the power line fuse continues to blow, a circuit malfunction exists and must be

corrected. Refer to the troubleshooting information in Section 4 of this manual
for additional information.

Table 3-1

Power line fuses

Line voltage Fuse rating Keithley part no.

100V, 120V 0.630A Slo Blo, 250V, 5 × 20mm FU-106-.630

220V, 240V 0.315A Slo Blo, 250V, 5 × 20mm FU-106-.315

3-4 Routine Maintenance Model 2500 Service Manual

4

Troubleshooting

4-2 Troubleshooting Model 2500 Service Manual

Introduction

This section of the manual will assist you in troubleshooting and repairing the Model 2500
Dual Photodiode Meter. Included are self tests, test procedures, troubleshooting tables,
and circuit descriptions. Note that disassembly instructions are located in Section 5, and
component layout drawings are at the end of Section 6.

Safety considerations

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

nel 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 2500, 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 2500 are contained in Section 5 of this manual.

• Do not make repairs to surface mount PC boards unless equipped and qualified to
do so.

• When working inside the unit and replacing parts, be sure to adhere to the handling
precautions and cleaning procedures explained in Section 5.

• Many CMOS devices are installed in the Model 2500. 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 2500
must be recalibrated. See Section 2 for details on calibrating the unit.

Model 2500 Service Manual Troubleshooting 4-3

Power-on self test

During the power-on sequence, the Model 2500 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. Using the EDIT keys, 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.

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

4-4 Troubleshooting Model 2500 Service Manual

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.

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 — Digital circuitry block diagram

Model 2500 Service Manual Troubleshooting 4-5

Overall block diagram

Figure 4-1 shows an overall block diagram of the Model 2500. Circuitry may be divided

into two general areas:

• Analog circuits — includes measurement circuits such as the I/V converter, mux,
and A/D converter, as well as voltage bias circuits.

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

Figure 4-1

Overall block diagram

Front Panel

Keypad

2 Line VFD

MC68332

Microprocessor

OPTO

Interface

Digital I/O

Trigger Link

Channel 1

D/A

A/D

GPIB

RS-232

Voltage Source Channel 1

±10V, ±100V

20mA Max

I/V Converter Channel 1

(8 Current Ranges

2nA - 20mA)

OUTPUT 1

INPUT 1

OPTO

Interface

Channel 2

D/A

A/D

Voltage Source Channel 2

±10V, ±100V

20mA Max

I/V Converter Channel 2

(8 Current Ranges

2nA - 20mA)

OUTPUT 2

INPUT 2

4-6 Troubleshooting Model 2500 Service Manual

Analog circuits

Figure 4-2 shows a simplified block diagram of the analog circuits.

Current measurement circuits

Signal conditioning for the input current is provided by an I/V converter, which converts
the input signal current to voltage that can be used by the A/D converter. Current ranging
is provided by selecting various feedback resistors and switching in an X10 gain amplifier
at appropriate times. The multiplexer (not shown) switches among different signals during
the various phases of the measurement cycle, and passes the signal along to the A/D
converter.

A/D converter

Each Model 2500 channel uses a multi-slope charge balance A/D converter with a single­slope run-down. The converter is controlled by a gate array. Commands are issued by the
MPU to the gate array, and the gate array IC sends A/D reading data back to the MPU for
calibration and processing.

Bias voltage circuits

Each Model 2500 voltage bias source is a digitally controlled source that can source up to
±100V @ 20mA. Digital control information from the MPU is converted into an equiva­lent analog signal, which is amplified to provide the full ±100V, 20mA output capability.
Source ranging (10V or 100V) is performed by controlling the overall gain of the amplifier
stage. Compliance circuitry detects when the output current exceeds a fixed 20mA limit
and sends an over-compliance flag bit back to the MPU.

Model 2500 Service Manual Troubleshooting 4-7

Figure 4-2

Analog circuitry block diagram

R (Range 7 & 8)

R (Range 5 & 6)

Triax INPUT

20mA Max

Floating

Channel 1/2

Ground

R (Range 3 & 4)

R (Range 1 & 2)

I/V Converter

Voltage Bias Source

0 to ±10V, ±100V

20mA Max

Output
Enable

Earth

Connect

Current

Range

Switching

Voltage

Source

OUTPUT

X10

X10

Enable

To

A/D

Converter

Note: One channel shown

4-8 Troubleshooting Model 2500 Service Manual

Power supply

Figure 4-3 shows a block diagram of the Model 2500 power supply system.

NOTE There are two identical power supply systems in the Model 2500, one for each

channel. Only one power supply is shown in Figure 4-3.

Regulated circuits include ±5V and ±15V to power the analog circuits, and a separate
+5VD supply to power digital circuits. Unregulated ±110V supplies power to the bias
source output stages.

Figure 4-3

Power supply block diagram

Voltage

Channel 1 or 2
Analog Circuits

±5V

±15V

Source
Output

Stage

±110V

Digital

Circuits

+5VD

Line In

100/120/220/

240V AC

Line

Filter

Channel 1 or 2

Analog Supplies

Power

Transformer

Digital

Supply

Note: One channel shown

Model 2500 Service Manual Troubleshooting 4-9

Digital circuitry

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

The core digital circuitry uses a Motorola 68332 microcontroller running at 20MHz. The
memory configuration includes a flash EEPROM and a RAM. Flash ROM support allows
internal firmware upgrades using either the serial or GPIB port for downloading new firm­ware. All calibration constants and the saved setups are stored in a separate serial
EEPROM.

External communication is provided via GPIB and serial interfaces. A 9914 GPIB IEEE­488 with standard interface ICs are used for the GPIB, and an IC to provide the voltage
conversion for the RS-232 port.

Figure 4-4

Digital circuitry block diagram

Channel 1

Channel 2

Reset

2

E PROM

Channel 1

OPTO Interface

Channel 2

OPTO Interface

ROM RAM

Microprocessor

Front

Panel

Controller

32.768KHz

Serial

Interface

GPIB

Digital I/O

VFD

Keypad

Trigger

RS-232

Interface

IEEE-488
Interface

To Display

Board Controller

Trigger

Link

Digital

I/O

4-10 Troubleshooting Model 2500 Service Manual

Display board circuits

The display board includes a microcontroller that controls the Vacuum Fluorescent
Display (VFD) and interprets key data. The microcontroller has four peripheral I/O ports
that are used for the various control and read functions.

The VFD module can display up to 52 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.
Circuitry includes the grid drivers and dot drivers.

Troubleshooting

Troubleshooting information for the various circuits is summarized below. Refer to the
component layout drawings at the end of Section 6 for component locations.

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

Item/

Step

component Required condition Remarks

1

Front panel test

2

J1033

3

U902, pin 1

4

U902, pin 43

5

U902, pin 32

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 1ms.
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.

Model 2500 Service Manual Troubleshooting 4-11

Power supply checks

Power supply problems can be checked out using Table 4-2. See “Principles of operation”
for circuit theory on the power supply.

Table 4-2

Power supply checks

Step Item/component* Required condition Remarks

01

Line fuse

02

Line power

03

+5VDA TP

04

+5VA TP

05

-15VA TP

06

+5VA TP

07

-5VA TP

08

+110VA TP

09

-110VA TP

10

+5VDB TP

11

+5VB TP

12

-15VB TP

13

+5VB TP

14

-5VB TP

15

+110VB TP

16

-110VB TP

*Test points (TP) are marked on circuit board.

Check continuity.
Plugged into live receptacle, power on.
+5V, ±5%
+15V ±5%

-15V, ±5%
+5V, ±5%

-5V, ±5%
+110V, ±20%

-110V, ±20%
+5V, ±5%
+15V ±5%

-15V, ±5%
+5V, ±5%

-5V, ±5%
+110V, ±20%

-110V, ±20%

Remove to check.
Check for correct power-up sequence.
Referenced to GND DA TP.
Referenced to GND A TP.
Referenced to GND A TP.
Referenced to GND A TP.
Referenced to GND A TP.
Referenced to GND A TP.
Referenced to GND A TP.
Referenced to GND DB TP.
Referenced to GND B TP.
Referenced to GND B TP.
Referenced to GND B TP
Referenced to GND B TP.
Referenced to GND B TP.
Referenced to GND B TP.

4-12 Troubleshooting Model 2500 Service Manual

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

01

Power-on test

02

U163 pin 19

03

U163 pin 7

04

U163 pin 68

05

U163, A0-A19

06

U163, D0-D15

07

U163 pin 66

08

U166 pin 7

09

U166 pin 8

10

U167 pins 34-42

11

U167 pins 26, 27,

29-32

12

U167 pin 24

13

U167 pin 25

14

U163 pin 43

15

U171 pin 4

16

U163 pin 45

17

U163 pin 47

18

U165 pin 48

RAM OK, ROM OK.
Digital common.
+5V
Low on power-up, then goes high.
Check for stuck bits.
Check for stuck bits.
20MHz.
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.
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 TX line.
RS-232 RX line.
IEEE-488 data bus.
IEEE-488 command lines.

IEEE-488 REN line.
IEEE-488 IFC line.
ADRXB
ADTX
AD_CLK
AD_TS
ADSEL

Model 2500 Service Manual Troubleshooting 4-13

Analog circuitry checks

Table 4-4 summarizes analog circuitry checks.

Table 4-4

Analog circuitry checks

Step Item/component Required condition* Remarks

01

INPUT #1

02

TP312

03

TP318

04

INPUT #2

05

TP512

06

TP518

07

Source 1

08

TP308

09

TP306, TP311

10

Source 1

11

TP308

12

TP306, TP311

13

Source 2

14

TP508

15

TP506, TP511

16

Source 2

17

TP508

18

TP506, TP511

*Voltage source steps (8-18) are with OUTPUT ON. Source 1 voltages reference to A_GND TP. Source 2 voltages referenced to

B_GND TP.

Apply +20mA

-10V
Pulses
Apply +20mA

-10V
Pulses
10V range, output

-2V
+10V
100V range, output

-2V
+100V
10V range, output

-2V
+10V
100V range, output

-2V
+100V

Select chan 1 20mA range.
Chan 1 I/V converter output.
Chan 1 A/D input signal(s).
Select chan 2 20mA range.
Chan. 2 I/V converter output.
Chan 2 A/D input signal(s).
Set channel 1 source to +10V.
Ch. 1 DAC output.
Ch. 1 source output.
Set channel 1 source to +100V.
Ch. 1 DAC output.
Ch. 1 source output (OUTPUT ON).
Set channel 2 source to +10V.
Ch. 2 DAC output.
Ch. 2 source output (OUTPUT ON).
Set channel 2 source to +100V.
Ch. 2 DAC output.
Ch. 2 source output (OUTPUT ON).

4-14 Troubleshooting Model 2500 Service Manual

No comm link error

A “No Comm Link” error message indicates that the front panel processor has stopped
communicating with the main processor, which is located on the mother board. This error
indicates that the main processor ROMs may require reseating in their sockets. The 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. Locate the firmware ROMs located on the digital section of the mother board.
These ROMs are the only IC installed in a socket. (Refer to the 2500-100 compo­nent layout drawing at the end of Section 6 for exact location.)

CAUTION Be careful not to push down excessively, or you might crack the mother

board.

4. Carefully push down on the ROM ICs to make sure it is properly seated in its
socket.

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

5

Disassembly

5-2 Disassembly Model 2500 Service Manual

Introduction

This section explains how to handle, clean, and disassemble the Model 2500 Dual Photo­diode Meter. 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. The preamp boards
and certain mother board areas have high-impedance devices or sensitive circuitry where
contamination could cause degraded performance.

Handling PC boards

Observe the following precautions when handling PC boards:

• Wear cotton gloves.

• Only handle PC boards by the edges and shields.

• Do not touch any board traces or components not associated with repair.

• Do not touch areas adjacent to electrical contacts.

• Use dry nitrogen gas to clean dust off PC boards.

Solder repairs

Observe the following precautions when 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 122°F (50°C), low-humidity environ­ment for several hours.

Model 2500 Service Manual Disassembly 5-3

Static sensitive devices

CAUTION Many CMOS devices are installed in the Model 2500. Handle all semi-

conductor devices as being static sensitive.

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:

• 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. 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 reassemble the Model 2500. Refer to these drawings for information about the
Keithley part numbers of most mechanical parts in the unit. Assembly drawings include:

• Front panel assembly — 2500-040

• Chassis/power module assembly — 2500-050

• Front panel/chassis assembly — 2500-051

• Chassis assembly — 2500-052

• Final inspection — 2500-080

5-4 Disassembly Model 2500 Service Manual

Case cover removal

WARNING Before removing the case cover, disconnect the line cord and any test

leads from the instrument.

Follow the steps below to remove the case cover to gain access to internal parts.

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 orienta­tion 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 reinstalling 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 bottom screws — Remove the four screws that secure the case to the

chassis. They are located on the bottom of the case.

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.

Input board removal

Perform the following steps to remove the two input boards. This procedure assumes that
the case cover is already removed.

1. Remove the INPUT jack nuts.

Each INPUT jack has a nut that secures the jack to the rear panel. Remove these
two nuts and lock washers.

2. Remove input board bracket mounting screws.

Remove the two mounting screws that secure the input board support bracket to the
chassis.

Model 2500 Service Manual Disassembly 5-5

3. Unplug cables:

• Unplug the connecting cable at the rear of each input board.

• Disconnect the input board connecting cables from the mother board at J301
and J501.

4. Remove input board assembly.

Slide the input board assembly forward until the INPUT jacks clear the mounting
holes in the rear panel, then remove the assembly.

Mother board removal

Perform the following steps to remove the mother board. This procedure assumes that the
case cover and input boards are already removed.

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

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

2. Remove mother board mounting screws.

Remove the four mounting screws that secure the mother board to the chassis.

3. Unplug cables:

• Unplug the display board ribbon cable from J1014.

• Unplug the cable going to the power supply module from J104.

• Unplug the cables going to the power transformers from J305 and J505.

• Unplug the cable going to the OUTPUT indicator from J105.

• Unplug the wires going to the rear panel VOLTAGE SOURCE OUTPUT jacks
from J302 and J502.

4. Remove mother board.

Slide the mother board forward slightly until the rear panel connectors clear the
holes in the rear panel, then remove the board.

During reassembly, replace the mother board, and start the IEEE-488, DIGITAL
I/O, and RS-232 connector screws and the board mounting screws. Tighten all the
fasteners once they are all in place and the board is correctly aligned. Be sure to
plug in all cables.

5-6 Disassembly Model 2500 Service Manual

Front panel disassembly

Use the following procedure to remove the display board and/or the pushbutton switch
pad.

1. Remove the power switch rod. Carefully disconnect the power switch rod from the
power switch mounted on the rear panel power module. Slide the rod toward the
rear until it clears the access hole in the front panel, then remove the rod.

2. Remove the front panel assembly. This assembly has four retaining clips that snap
onto the chassis over four pem nut studs. Two retaining clips are located on each
side of the front panel. Pull the retaining clips outward and, at the same time, pull
the front panel assembly forward until it separates from the chassis.

3. Unplug the display board ribbon cables.

4. Using a thin-bladed screw driver, pry the plastic PC board stop (located at the bot­tom of the display board) until the bar separates from the casing. Pull the display
board from the front panel.

5. 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 mother board be removed, as previously explained.

Power supply module removal

Perform the following steps to remove the power supply module:

1. Disconnect and remove the cables that connect the power supply module on the
bottom of the chassis to the power transformer and rear panel power module.

2. Remove the screws that secure the power supply to the chassis bottom, then
remove the module.

Power module removal

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

1. Disconnect the power module's ground wire. This green and yellow wire connects
to a threaded stud on the chassis with a kep nut.

2. Squeeze the latches on either side of the power module while pushing the module
from the access hole.

Model 2500 Service Manual Disassembly 5-7

Power transformer removal

To remove the power transformers, simply remove the screws that secure the transformers
to the bottom of the chassis, then remove the transformers.

Instrument reassembly

WARNING To ensure continued protection against electrical shock, verify that

power line ground (green and yellow wire attached to the power mod­ule) is connected to the chassis. Make sure the ground wires are
attached to the power transformer mounting screws.

Make sure the four bottom case screws are properly installed to secure
and ground the case cover to the chassis.

Reassemble the instrument by reversing the previous disassembly procedures. Make sure
that all parts are properly seated and secured, and that all connections are properly made.

5-8 Disassembly Model 2500 Service Manual

6

Replaceable Parts

6-2 Replaceable Parts Model 2500 Service Manual

Introduction

This section contains replacement parts information and component layout drawings for
the Model 2500 Dual Photodiode Meter.

Parts lists

The electrical parts lists for the Model 2500 are listed in the 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 2500)

• 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.

Model 2500 Service Manual Replaceable Parts 6-3

Component layouts

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

• Mother board — 2500-100

• Display board — 2400-110

• Input board — 2500-120

• Power board — 2500-130

Table 6-1

Mother board parts list

Keithley

Circuit designation Description

C217,C218,C266,C384,C584 CAP, 1000PF, 10%, 50V, MONO

CERAMIC
C219,C221,C222,C227,C233,C234,C238-C241 CAP, .1UF, 10%, 25V, CERAMIC C-495-.1
C220,C225,C226,C229-C232,C235,C242,C245 CAP, .01UF, 10%, 50V, CERAMIC C-491-.01
C223 CAP, 47PF, 10%, 100V, CERAMIC C-451-47P
C224,C228 CAP, 15P, 1%, 100V, CERAMIC C-512-15P
C236,C304,C309,C313,C386,C402,C405,C504 CAP, 22UF, 20%, 25V, TANTALUM C-440-22
C237,C385,C585,C400,C401,C403,C404,C600 CAP, .1UF, 10%, 25V, CERAMIC C-495-.1
C243,C246,C253,C255-C258,C262-C264,C267 CAP, .1UF, 10%, 25V, CERAMIC C-495-.1
C251,C311,C312,C511,C512 CAP, 1UF, 20%, 50V, CERAMIC C-519-1
C259,C268,C371,C373,C381,C392,C399,C599 CAP, 47P, 5%, 100V, CERAMIC C-465-47P
C265 CAP, 100P, 10%, 100V, CERAMIC C-451-100P
C279 CAP, .1UF, 20%, 100V, CERAMIC C-436-.1
C280,C283-C289,C291,C293,C294,C301-C303 CAP, .1UF, 10%, 25V, CERAMIC C-495-.1
C282 CAP, .01UF, 10%, 50V, CERAMIC C-491-.01
C290 CAP, 1UF, 20%, 35V, TANTALUM C-494-1
C292 CAP, 100P, 10%, 100V, CERAMIC C-451-100P
C305-C307,C310,C314,C320,C321,C331,C332 CAP, .1UF, 10%, 25V, CERAMIC C-495-.1
C308,C317,C319,C508,C517,C519 CAP, 1000UF, 20%, 35V, ALUM ELEC C-468-1000
C323,C324,C356,C357,C364,C408,C409,C411 CAP, 1UF, 10%, 500V, X7R C-525-.1
C325,C326,C525,C526 CAP, 220U, 20%, 160V, ALUM C-584-220
C342,C343,C346,C349-C355,C358,C363 CAP, .1UF, 10%, 25V, CERAMIC C-495-.1
C344,C359,C362,C544,C559,C562 CAP, 10UF, 20%, 25V, TANTALUM C-440-10
C345,C545,C328,C365,C528,C565 CAP, 100PF, 5%, 100V, CERAMIC C-465-100P
C360,C560 CAP, 100P, 5%, 500V, CERAMIC C-590-100P
C366,C372,C374-C379,C391,C393,C395 CAP, .1UF, 10%, 25V, CERAMIC C-495-.1
C367,C567,C347,C348,C369,C547,C548,C569 CAP, 1UF, 10%, 500V, X7R C-525-.1
C380,C383,C580,C583 CAP, 2200P, 10%, 100V, CERAMIC C-430-2200P
C382,C582 CAP, 100PF, 5%, 100V, CERAMIC C-465-100P
C388,C588 CAP, .1UF, 20%, 50V, CERAMIC C-418-.1

part no.

C-452-1000P

6-4 Replaceable Parts Model 2500 Service Manual

Table 6-1 (cont.)

Mother board parts list

Keithley

Circuit designation Description

C394,C396,C594,C596 CAP, .01UF, 10%, 50V, CERAMIC C-491-.01
C397,C597 CAP, 47P, 5%, 100V, CERAMIC C-465-47P
C398,C598 CAP, 100UF, 20%, 16V, TANTALUM C-504-100
C406,C407,C606,C607 CAP, 100UF, ±20%, 200V, ALUM ELECT C-498-100
C412,C413,C612,C613 CAP, 47U, +50%, -20%, 160V, ALUM

ELEC
C414,C415,C418,C419,C614,C615,C618,C619 CAP, 2.2UF, ±20%, 200V, ALUM ELECT C-498-2.2
C416,C417,C616,C617 CAP, .01UF, 10%, 200V, CERAMIC C-472-.01
C501-C503,C505-C507,C510,C514,C520,C521 CAP, .1UF, 10%, 25V, CERAMIC C-495-.1
C509,C513,C586,C602,C605 CAP, 22UF, 20%, 25V, TANTALUM C-440-22
C523,C524,C556,C557,C564,C608,C609,C611 CAP, 1UF, 10%, 500V, X7R C-525-.1
C531,C532,C542,C543,C546,C549-C555,C558 CAP, .1UF, 10%, 25V, CERAMIC C-495-.1
C563,C566,C572,C574-C579,C591,C593 CAP, .1UF, 10%, 25V, CERAMIC C-495-.1
C570 CAP, .1UF, 10%, 25V, CERAMIC C-495-.1
C571,C573,C581,C592 CAP, 47P, 5%, 100V, CERAMIC C-465-47P
C587,C589,C590,C387,C389,C390 CAP, .1UF, 20%, 50V, CERAMIC C-418-.1
C595,C318,C322,C327,C370,C518,C522,C527 CAP, .1UF, 10%, 25V, CERAMIC C-495-.1
C601,C603,C604,C281,C315,C316,C515,C516 CAP, .1UF, 10%, 25V, CERAMIC C-495-.1
CR115,CR116,CR122-CR129 DIODE, DUAL SWITCHING, BAV99L RF-82
CR117,CR118,CR119,CR120,CR121 DIODE, DUAL COMMON ANODE

BAW56LT2
CR302,CR502,CR303,CR503 ULTRA FAST BRIDGE RECTIFIER,

EDF1BM
CR304,CR504 DIODE, CRB2-100 RF-148
CR309-CR312,CR314-CR319,CR509-CR512 DIODE, SWITCHING, MMBD914 RF-83
CR313,CR513 DIODE, DUAL HSM-2822T31 RF-95
CR514-CR519 DIODE, SWITCHING, MMBD914 RF-83
F101 POLYSWITCH, SMD030-2 FU-103
HS301-HS303,HS501-HS503 HEAT SINK HS-55
HS314,HS514 HEAT SINK HS-39
J1006 CONN, CIRCULAR DIN CS-762
J1007 CONN, D-SUB DUAL STACK M-F CS-1072-1
J1008 CONN, RIGHT ANGLE, 24 PIN CS-501
J101,J103 CONN, BERG CS-339
J1014 CONN, HEADER STRAIGHT SOLDER

PIN
J102 CONN, HEADER STRAIGHT SOLDER

PIN
J104 CONNECTOR, HEADER CS-784-4
J105,J302,J502 LATCHING HEADER, FRICTON, SGL

ROW

part no.

C-354-47

RF-98

RF-123

CS-368-16

CS-368-10

CS-724-3

Model 2500 Service Manual Replaceable Parts 6-5

Table 6-1 (cont.)

Mother board parts list

Keithley

Circuit designation Description

part no.

J301,J305,J501,J505 LATCHING HEADER, FRICTION,

SINGLE ROW
K306,K506 RELAY, SURFACE MOUNT RL-188
K307,K308,K507,K508 NON LATCHING RELAY RL-242
L101 FERRITE BEAD CH-91
L102,L304-L308,L504-L508,L310,L510 FERRITE CHIP 600 OHM BLM32A07 CH-62
L301-L303,L501-L503,L309,L509,L311,L511 FERRITE CHIP 600 OHM BLM32A07 CH-62
Q118,Q120-Q125,Q309,Q310,Q321-Q324,Q509 TRANS, N-MOSFET, VN0605T TG-243
Q312,Q330,Q512,Q530,Q316,Q516 TRANS, NPN, CXTA42 TG-327
Q313,Q513 TRANS, NPN, MMBT3904 TG-238
Q314,Q514 TRANS, PMP, MJE5731A (TO-220) TG-315
Q315,Q327,Q515,Q527,Q311,Q511 TRANS, PNP, CXTA92 TG-328
Q318,Q518 TRANS, NPN, TIP48 (TO-220) TG-314
Q319,Q320,Q325,Q328,Q519,Q520,Q525,Q528 TRANS, NPN, MMBT3904 TG-238
Q326,Q329,Q526,Q529 TRANS, PNP, MMBT3906L TG-244
Q510,Q521-Q524 TRANS, N-MOSFET, VN0605T TG-243
R205 RES, .0499, 1%, 100MW, THICK FILM R-418-.0499
R206,R209,R219,R220,R222,R235,R236,R216 RES, 10K, 1%, 100MW, THICK FILM R-418-10K
R210,R211,R221,R228,R230,R231,R267,R272 RES, 1K, 1%, 100MW, THICK FILM R-418-1K
R213,R215,R217,R237,R232-R234,R372,R384 RES, 475, 1%, 100MW, THICK FILM R-418-475
R226,R227,R293,R295,R297,R299,R378,R578 RES, 5.11K, 1%, 100MW, THICK FILM R-418-5.11K
R229,R239,R278,R294,R296,R298,R304,R381 RES, 100, 1%, 100MW, THICK FILM R-418-100
R238 RES, 15k, 1%, 100MW, THICK FILM R-418-15K
R240 RES, 332K, 1%, 100MW, THICK FILM R-418-332K
R241-R244,R249-R251,R253,R263-R266,R268 RES, 10K, 1%, 100MW, THICK FILM R-418-10K
R245,R246 RES, 10K, 1%, 100MW, THICK FILM R-418-10K
R247,R248 RES, 2K, 1%, 100MW, THICK FILM R-418-2K
R252 RES, 10M, 1%, 125MW, THICK FILM R-418-10M
R254,R270 RES, 4.75K, 1%, 100MW, THICK FILM R-418-4.75K
R255-R257,R279,R284,R367,R368,R567,R568 RES, 2.21K, 1%, 100MW, THICK FILM R-418-2.21K
R258-R262,R376,R576 RES, 1K, 1%, 100MW, THICK FILM R-418-1K
R269,R271,R274-R276,R285-R290,R369,R218 RES, 10K, 1%, 100MW, THICK FILM R-418-10K
R273 RES, 100, 5%, 250MW, METAL FILM R-376-100
R280,R281,R291,R292,R323,R328,R329,R344 RES, 1K, 1%, 100MW, THICK FILM R-418-1K
R282 RES, 475, 1%, 100MW, THICK FILM R-418-475
R317,R424,R517,R624 RES, 1K, 1%, 100MW, THIN FILM R-438-1K
R322,R522 RES, 110K, 1%, 100MW, THICK FILM R-418-110K
R324,R524 RES, 48.1K, .1%, 1/10W, METAL FILM R-263-48.1K
R325,R525 RES, 5.62K, .1%, 1/10W, METAL FILM R-263-5.62K
R326,R526 RES, 392, 1%, 100MW, THICK FILM R-418-392
R327,R330,R333,R335,R527,R530,R533,R535 RES, 69.8K, 1%, 1W, THICK FILM R-418-69.8K

CS-724-12

6-6 Replaceable Parts Model 2500 Service Manual

Table 6-1 (cont.)

Mother board parts list

Keithley

Circuit designation Description

R332,R334,R532,R532 RES, 4.75M, 1%, 100MW, THICK FILM R-418-4.75M
R336,R339,R536,R539 RES, 10, 10%, 100MW, THICK FILM R-418-10
R342,R343,R345,R346,R542,R543,R545,R546 RES, 20K, 5%, 250MW, METAL FILM R-376-20K
R349,R549,R425,R625 RES, 100K, .1%, 1/10W, METAL FILM R-263-100K
R351,R355,R389,R395,R551,R555,R589,R595 RES, 100K, 1%, 100MW, THICK FILM R-418-100K
R356,R357,R523,R528,R529,R544,R556,R557 RES, 1K, 1%, 100MW, THICK FILM R-418-1K
R358-R365,R558-R565 RES, 4.99K, 1%, 100MW, THICK FILM R-418-4.99K
R366,R566 RES, 1.28M, .1%, 1/8W, METAL FILM R-176-1.28M
R370,R570 RES, 49.9K, 1%, 100MW, THICK FILM R-418-49.9K
R371,R383,R398,R569,R571,R583,R598 RES, 10K, 1%, 100MW, THICK FILM R-418-10K
R373,R573 RES, 34K, 1%, 100MW, THICK FILM R-418-34K
R374,R574 RES, 82.5, 1%, 100MW, THICK FILM R-418-82.5
R375,R575 RES, 4.75K, 1%, 100MW, THICK FILM R-418-4.75K
R377,R577 RES, 100, 1%, 100MW, THICK FILM R-418-100
R379,R579 RES, 470, 5%, 125MW, METAL FILM R-375-470
R380,R580 RES, 10, 5%, 125MW, METAL FILM R-375-10
R382,R392,R582,R592 RES, .0499, 1%, 100MW, THICK FILM R-418-.0499
R385,R386,R585,R586 RES, 6.04K, 1%, 100MW, THICK FILM R-418-6.04K
R387,R587 RES, 2.49K, 1%, 125MW, METAL FILM R-391-2.49K
R388,R588 RES, 4.99K, 1%, 125MW, METAL FILM R-391-4.99K
R390,R590 RES, 6.04K, 1%, 125MW, THIN FILM R-423-6.04K
R391,R591 RES NET TF-245
R396,R399,R596,R599,R319,R320,R519,R520 RES, 24.9, 1%, 100MW, THICK FILM R-418-24.9
R397,R409,R410,R597,R609,R610 RES, 10, 5%, 250MW, METAL FILM R-376-10
R401,R601 RES, 909, 1%, 1W, THICK FILM R-418-909
R403,R603 RES, 100K, 1%, .1W, THIN FILM R-438-100K
R405-R408,R572,R584,R605-R608,R207,R208 RES, 475, 1%, 100MW, THICK FILM R-418-475
R411,R415,R611,R615 RES, 1K, 5%, 250MW, METAL FILM R-376-1K
R412,R413,R416,R417,R612,R613,R616,R617 RES, 20K, 5%, 250MW, METAL FILM R-376-20K
R414,R418,R614,R618 RES, 11K, 5%, 250MW, METAL FILM R-376-11K
R419,R619 RES, 20K, 1%, 100MW, THIN FILM R-438-20K
R420,R620 RES, 2.21K, 1%, 100MW, THIN FILM R-438-2.21K
R423,R623 RES, 11.8K, 1%, 100MW, THIN FILM R-438-11.8K
R426-R430,R626-R630 RES, 174K, 1%, 100MW, THIN FILM R-438-174K
R540,R541,R547,R548,R318,R422,R518,R622 RES, 1K, 1%, 100MW, THICK FILM R-418-1K
R581 RES, 100, 1%, 100MW, THICK FILM R-418-100
R594,R394,R331,R340,R341,R347,R348,R531 RES, 1K, 1%, 100MW, THICK FILM R-418-1K
RV301,RV501 VARISTOR SMT VR-27
RV302,RV502 VARISTOR VR-23
SA301,SA501 SURGE ARRESTOR CG2-300L SA-2
SO120,SO121 SOCKET PLCC-032-T-A SO-143-32

part no.

Model 2500 Service Manual Replaceable Parts 6-7

Table 6-1 (cont.)

Mother board parts list

Keithley

Circuit designation Description

U120 PROGRAMMED ROM 2500-800*
U121 PROGRAMMED ROM 2500-801*
U150 64K BIT SERIAL FRAM IC-1381
U154,U161 IC, 2 INPUT NAND GATE, NC7S00 IC-1181
U155 IC, OCT BFR/LINE DRIVE, 74HCT244 IC-651
U159,U165 IC, POS NAND GATES/INVERT,

74HCT14
U160,U162 IC, 256K X 16 BIT CMOS RAM 17NS LSI-249-1
U163 IC, 32-BIT MICROCONTROLLER

20MHZ
U164 IC, PROTECTED QUAD POWER

DRIVERS
U166 IC, +5V RS-232 TRANSCEIVER,

MAX202
U167 IC, GPIB ADAPTER, 9914A LSI-123
U169 IC, OCTAL INTER BUS TRANS, 75161 IC-647
U170 IC, OCTAL INTERFACE BUS, 75160 IC-646
U171 IC, 2-INPUT OR GATE IC-1206
U301,U501 IC, +5V VOLTAGE REGULATOR,

LM2940CT
U302,U502 IC, POS VOLTAGE REG +15V, 60MA,

LM2940CT-15
U303,U503 IC, NEG VOLTAGE REG -15V, 50MA,

LM2990T-15
U304,U305,U504,U505 IC, OPTOCOUPLER, 2611 IC-690
U308,U508 IC, CMOS ANALOG SWITCH IC-1395
U309,U509 IC, +5V 16 BIT DAC, MAX542ACSD IC-1176
U310,U510 IC, VOLTA GE REFERENCE IC-1065
U312,U512 IC, DIFFERENTIAL AMP, INA117P IC-889
U313,U513 IC, DUAL OP-AMP, LF353M IC-842
U314,U514 IC, OP AMP, LOW POWER AD795JR IC-1052
U315,U316,U515,U516 IC, 8 STAGE SHIFT C074HC409AM IC-1026
U317,U517 IC, 8-CHAN ANA MULTIPLEXER,

DG408DY
U318,U518 IC, OP-AMP, LOW NOISE LT1007CS8 IC-949
U319,U519 IC, QUAD D FLIP FLOP W/CLK, RESET

74HC175
U320,U321,U520,U521 IC, QUAD 2 IN NOR, 74HCT02 IC-809
U322,U522 IC, NCHAN LAT DMOS QUADFET,

SD5400CY
U323,U523,U311,U511 IC, OPA177GS IC-960

part no.

IC-656

LSI-203-20

IC-1212

IC-952

IC-576

IC-1186

IC-1187

IC-844

IC-923

IC-893

6-8 Replaceable Parts Model 2500 Service Manual

Table 6-1 (cont.)

Mother board parts list

Keithley

Circuit designation Description

part no.

U324,U524 IC, PRECISION BIFET OPAMP IC-1194
U325,U525 IC, OP-AMP, NE5534D IC-802
U326,U526 IC, VOLT. COMPARATOR, LM311M IC-776
U327,U527 PROGRAM 2000-802*
U328,U528 IC, DUAL BIPOLAR OP-AMP,

IC-955

LT1124CS8
U329,U529 IC, +5V 12 BIT DAC IC-1329
U330,U530 IC, SUPPLY VOLT SUPERVISOR,

IC-860

TL7705A
U331,U531 IC, VOLTA GE REGULA T OR IC-1132
U332,U532 IC, -5V VOLTAGE REGULATOR IC-1134
U334,U534,U333,U533 IC, DUAL HIGH CMR/SPEED OPTO,

IC-588

HCPL-2631
VR101 DIODE, ZENER 30V BZX84C30 DZ-106-30
VR303,VR304,VR503,VR504 DIODE, ZENER MM524694 TI DZ-113
VR308,VR309,VR508,VR509 DIODE, ZENER, 6.2V MMSZ6V2 DZ-97
VR310,VR510 DIODE DZ-127
Y101 CRYSTAL, FSM327 CR-41
Y301,Y501 OSCILLATOR HIGH SPEED CMOS

CR-37

12MHZ

*Order current firmware revision. For example, 2500-801A01.

Model 2500 Service Manual Replaceable Parts 6-9

Table 6-2

Input board parts list

Keithley

Circuit designation Description

part no.

C327 CAP, .01UF, 10%, 200V, CERAMIC C-472-.01
C328,C337 CAP, 1000P, 10%, 100V, CERAMIC C-451-1000P
C329 CAP, 33PF, 10%, 100V, CERAMIC C-451-33P
C330 CAP, 10PF, 5%, 100V, CERAMIC C-372-10P
C333,C336,C338,C341 CAP, .1UF, 10%, 25V, CERAMIC C-495-.1
C334,C335 CAP, .33U, 10%, 16V, TANTALUM C-585-3.3
C339,C340 CAP, 10UF, 20%, 25V, TANTALUM C-440-10
C342 CAP, 100PF, 5%, 100V, CERAMIC C-465-100P
C345 CAP, 47P, 5%, 100V, CERAMIC C-465-47P
CR305,CR306,CR307,CR308,CR309,

DIODE, SWITCHING, MMBD914 RF-83

CR310
J100 CONN, MALE 12 PIN RT ANGLE CS-612-12
J303 TRIAX RECEPTACLE, PCB MOUNT CS-995
K301 RELAY, 1FORMA, COTO 1203-0147 RL-181
K302,K303,K304,K305 RELAY, SURFACE MOUNT RL-188
Q301,Q302 TRANS, N-MOSFET, VN0605T TG-243
Q305,Q306 TRANS, N CHANNEL FET, 2N4392 TG-128-1
R300,R301,R302,R303 RES, 500, .1%, 1/10W, METAL FILM R-263-500
R308 RES, 50K, .1%, 1/10W, METAL FILM R-263-50K
R310,R315,R316 RES, 10K, 1%, 100MW, THICK FILM R-418-10K
R312 RES, 5M, 1%, 1W, METAL FILM R-502-5M
R313 RES, 500M, 1%, 1W, METAL FILM R-502-500M
R314,R305,R306,R311 RES, 392, 1%, 100MW, THICK FILM R-418-392
R317,R404,R406,R405 RES, 1K, 1%, 100MW, THICK FILM R-418-1K
R318,R323 RES, 24.9K, 1%, 100MW, THICK FILM R-418-24.9K
R319 RES, 71.5K, 1%, .1W, THIN FILM R-438-71.5K
R320 RES, 150, 1%, 100MV, THIN FILM 0805 R-438-150
R321 RES, 1.37K, 1%, .1W, THICK FILM R-418-1.37K
R407 RES, 100, 1%, 100MW, THICK FILM R-418-100
TP305,TP306 SURFACE MOUNT PCB TEST POINT CS-1026
U303,U304,U305 IC, CMOS ANALOG SWITCH IC-1395
U306 IC, 25 FEMTO-AMP ELECTRO AMP

IC-1207

LMC6001AIN
U307 IC, OP-AMP, NE5534D IC-802
VR301,VR302 DIODE, ZENER 10V, MMSZ5240B DZ-99

6-10 Replaceable Parts Model 2500 Service Manual

Table 6-3

Power board parts list

Keithley

Circuit designation Description

part no.

J1001,J1002,J1003,J1004 CONN, RT ANGLE, MALE MOLEX, .156 CS-715-6
RV101 VARISTOR VR-26

Table 6-4

Display board parts list

Keithley

Circuit designation Description

part no.

C901 CAP, 22UF, 20%, 6.3, TANTALUM C-417-22
C902,C904,C907,C908,C910 CAP, .1UF, 20%, 100V, CERAMIC C-436-.1
C903,C905,C906,C909,C911 CAP, .1UF, 20%, 50V, CERAMIC C-418-.1
C912 CAP, 2.2UF, 20%, 100V, ALUM ELEC C-503-2.2
C913,C914 CAP, 100UF, 20%, 16V, TANTALUM C-504-100
C915,C916 CAP, 33PF, 10%, 100V, CERAMIC C-451-33P
CR901,CR902,CR903,CR904 DIODE, SWITCHING, 250MA, BAV103 RF-89
CR905,CR906 DIODE, SWITCHING, MMBD914 RF-83
DS901 VACUUM FLUORESCENT DISPLAY DD-51C
J1032 CONN, BERG CS-339
J1033 CONN, HEADER STRAIGHT SOLDER PIN CS-368-16
Q901,Q902 TRANS, NPN GEN PURPOSE, BC868 TG-293
R901 RES NET, 15K, 2%, 1.875W TF-219-15K
R902 RES, 13K, 5%, 125MW, METAL FILM R-375-13K
R903,R904 RES, 4.7K, 5%, 250MW, METAL FILM R-376-4.7K
R905 RES, 1M, 5%, 125MW, METAL FILM R-375-1M
R906 RES, 1K, 5%, 250MW, METAL FILM R-376-1K
R907 RES, 240, 5%, 250MW, METAL FILM R-376-240
R908 RES, 10M, 5%, 125MW, METAL FILM R-375-10M
T901 TRANSFORMER, TDK, ER14.5 SERIES TR-300
U901,U904,U905 IC, LATCHED DRIVERS, UCN-5812EPF-1 IC-732
U902 PROGRAMMED ROM 7001-800A02
U903 IC, 32-BIT, SERIAL UCN5818EPF-1 IC-830
VR901 DIODE, ZENER, 8.2V, MMBZ5237 DZ-92
Y901 CRYSTAL, 4MHZ CR-36-4M

Model 2500 Service Manual Replaceable Parts 6-11

Table 6-5

Miscellaneous parts list

Qty Description Keithley part no.

2 BANANA JACK, PUSH-IN RED BJ-14-2
1 BEZEL, REAR 428-303D
1 CABLE ASSEMBLY CA-239-1A
1 CONDUCTIVE RUBBER SWITCH 2500-315A
1 COVER 2500-317A
1 DISPLAY LENS 2500-311A
2 FOOT 428-319A
2 FOOT, EXTRUDED FE-22A
2 FOOT, RUBBER FE-6
1 FRONT PANEL, MODIFIED 2400-318B
1 FUSE HOLDER FH-35-1
1 FUSE, .630A, 250V, SLO BLO FUSE FU-106-.630
1 HANDLE 428-329F
1 LABEL MC-233A
1 LED, HIGH POWER PL-94
1 LENS, LED 6517-309B
1 LINE CORD CO-7
1 LINE MODULE PM-1-1B
1 MEMBRANE SWITCH, FRONT PANEL 6430-313A
1 MOUNTING EAR, LEFT 428-338B
1 MOUNTING EAR, RIGHT 428-328E
2 PC BOARD STOP 2001-371A
1 POWER ROD 2001-320A
1 POWER SUPPLY PS-75-1A
1 SUPPORT BAR 2500-318A
2 TRANSFORMER TR-342B

6-12 Replaceable Parts Model 2500 Service Manual

A

Specifications

A-2 Specifications

The Model 2500 Dual Photodiode Meter can measure and display either photodiode current or optical power for
two photodiodes with appropriate user-supplied optical power gain/wavelength calibration factors.

Measurement Specifications

TEMPERATURE

ACCURACY

1,2

COEFFICIENT DC INPUT

MAXIMUM 23°C ±5°C 0°–18°C & 28°–50°C IMPEDANCE

3

RANGE RESOLUTION ±(% rdg.+ offset) ±(%rdg. + offset)/°C (Maximum)

2.000000 nA 1 fA 1.00% + 2 pA 0.01 + 200 fA 20 kΩ

20.00000 nA 10 fA 0.40% + 2 pA 0.01 + 200 fA 20 kΩ

200.0000 nA 100 fA 0.30% + 200 pA 0.02 + 20 pA 200 Ω

2.000000 µA 1 pA 0.20% + 200 pA 0.02 + 20 pA 200 Ω

20.00000 µA 10 pA 0.10% + 20 nA 0.01 + 2 nA 2.0 Ω

200.0000 µA 100 pA 0.10% + 20 nA 0.01 + 2 nA 2.0 Ω

2.000000 mA 1 nA 0.10% + 2 µA 0.02 + 200 nA 0.2 Ω

20.00000 mA 10 nA 0.10% + 2 µA 0.02 + 200 nA 0.2 Ω

MAXIMUM INPUT: ±20.0mA.

T ypical Speed and Noise Rejection

4

READINGS/s

DIGITS GPIB (SCPI) GPIB (488.1) NPLC NMRR

41⁄

2

700 900 0.01 —

5

1

⁄

2

460 475 0.1 —

61⁄

2

58 58 1 60 dB

Photodiode Voltage Bias Specifications

2

ACCURACY MAXIMUM LOAD TEMPERATURE

RANGE RESOLUTION 23°C ±5°C CURRENT REGULATION5COEFFICIENT

0 to ±10 V <400 µV ±(0.15% of setting 20 mA < 0.30%, 150 ppm/°C

+ 5 mV) 0 to 20 mA

0 to ±100 V <4 mV ±(0.3% of setting 20 mA < 0.30%, 300 ppm/°C

+ 50 mV) 0 to 20 mA

Specifications A-3

General

Typical Noise Floor Measurement Specification

6

TYPICAL NOISE FLOOR

RMS (1 STDEV), 100 SAMPLES

RANGE 0.01 NPLC 0.1 NPLC 1.0 NPLC 10 NPLC

2.000000 nA 2 pA 1 pA 40 fA 15 fA

20.00000 nA 2 pA 1 pA 40 fA 15 fA

200.0000 nA 200 pA 100 pA 2 pA 500 fA

2.000000 µA 200 pA 100 pA 2 pA 500 fA

20.00000 µA 20 nA 10 nA 200 pA 50 pA

200.0000 µA 20 nA 10 nA 200 pA 50 pA

2.000000 mA 2 µA 1 µA 25 nA 5 nA

20.00000 mA 2 µA 1 µA 25 nA 5 nA

SOURCE CAPACITANCE: Stable to 10.0nF typical.
INPUT BIAS CURRENT

7

: 50fA max. @ 23°C.

INPUT VOL T AGE BURDEN

8

: 4.0mV max.
VOLTAGE SOURCE SLEW RATE: 3.0ms/V typical.
COMMON MODE VOLTAGE: 200VDC.
COMMON MODE ISOLATION:Typically 10

9

Ω in parallel with 150nF.

OVERRANGE: 105% of measurement range.
MEMORY BUFFER:6000 readings (two 3000 point buffers). Includes selected measured value(s) and time stamp.
PROGRAMMABILITY:IEEE-488 (SCPI-1995.0), RS-232, five user-definable power-up states plus factory default and *RST.
DIGITAL INTERFACE:

Enable: Active low input.
Handler Interface: Start of test, end of test, 3 category bits. +5V @ 300mA supply.

Digital I/O: 1 trigger input, 4 TTL/Relay Drive outputs (33V @ 500mA, diode clamped).
POWER SUPPLY: 100V/120V/220V/240V ±10%
LINE FREQUENCY:50, 60Hz.
POWER DISSIPATION: 60VA.
WARRANTY: 1 year.
EMC: Complies with European Union Directive 89/336/EEC.
VIBRATION:MIL-T-28800F Random Class 3.
SAFETY:Complies with European Directive 73/23/EEC.
WARM-UP:1 hour to rated accuracy.
DIMENSIONS: 89mm high ×213mm wide × 370mm deep (3

1

⁄2in × 83⁄8in × 149⁄16in). Bench configuration (with handle and feet): 104mm high ×

238mm wide × 370mm deep (4

1

⁄8in × 93⁄8in × 149⁄16in).

WEIGHT: 23.1kg (10.5 lbs).
ENVIRONMENT:Operating: 0°–50°C, 70% R.H. up to 35°C non-condensing. Derate 3% R.H./°C, 35°–50°C. Storage:–25°to 65°C, non-condensing.

NOTES:

1. Speed = Normal (1.0 NPLC), Filter On.

2. 1 year.

3. Measured as ∆V

in

/∆Iinat full scale (and zero) input currents.

4. Dual channel, internal trigger, measure only, display off, Autorange off, Auto Zero off, source delay = 0, filters off, limits off, CALC5 and CALC6 off, 60Hz.

5. Measured as ∆V

in

/∆Iinat full scale (20mA) and zero load currents.

6. Noise floor measured as rms (1 standard deviation), 100 samples, Filter off, open (capped) input.

7. Specification by design.

8. Measured (at input triax) as ∆V

in

at full scale (20mA) vs. zero input currents.

Specifications subject to change without notice.

A-4 Specifications Model 2500 User’s Manual

Accuracy calculations

The following information discusses how to calculate accuracy for both current measure­ment and voltage bias functions.

Current measurement accuracy

Current measurement accuracy is calculated as follows:
Accuracy = ±(% of reading + offset)
As an example of how to calculate the actual reading limits, assume that you are measur-

ing 1mA on the 2mA range. You can compute the reading limit range from one-year mea­surement specifications as follows:

Accuracy = ±(% of reading + offset)

=± [(0.1% × 1mA) + 50nA]
= ±(1 µ A + 50nA)
= ±1.05 µ A

Thus, the actual reading range is 1mA ±1.05 µ A or from 0.99895mA to 1.00105mA.

V oltage bias accuracy

Voltage bias accuracy is calculated similarly, except that voltage bias specifications are
used. As an example of how to calculate the actual source output limits, assume that you
are sourcing 5V on the 10V range. You can compute the output limits from voltage bias
one-year accuracy specifications as follows:

Accuracy = ±(0.05% of setting + 5mV offset)

=± [(0.05% × 5 V ) + 5 mV )]
= ±(2.5mV + 5mV)
= ±7.5mV

In this case, the actual voltage output range is 5V ±7.5mV or from 4.9925V to 5.0075V.

B

Calibration Reference

B-2 Calibration Reference Model 2500 Service Manual

Introduction

This appendix contains detailed information on the various Model 2500 Dual Photodiode
Meter remote calibration commands, calibration error messages, and methods to detect the
end of each calibration step.

Section 2 of this manual covers detailed calibration procedures.

Command summary

Table B-1 summarizes Model 2500 calibration commands. These commands are covered

in detail in the following paragraphs.

Table B-1

Calibration commands

Command Description

:CALibration

:PROTected

:CODE ‘<password>’
:CODE?
:SENSe[1] <NRf>

:DATA <NRf>
:DATA?

:SOURce[1] <NRf>

:DATA <NRf>
:DATA?
:OFFSet

:SENSe2 <NRf>

:DATA <NRf>
:DATA?

:SOURce2 <NRf>

:DATA <NRf>
:DATA?

:OFFSet
:DATE <yyyy>,<mm>,<dd>
:DATE?
:NDUE <yyyy>,<mm>,<dd>
:NDUE?
:SAVE
:LOCK
:LOCK?
:COUNt?

Calibration subsystem.
Calibration commands protected by password.
Unlock calibration. (Default password: KI002500.)
Query calibration code/password.
Calibrate active channel 1 current measurement range.
Set channel 1 current measurement calibration constants.
Query channel 1 current measurement calibration constants.
Calibrate channel 1 active voltage bias range.
Set channel 1 voltage bias calibration constants.
Query channel 1 voltage bias calibration constants.
Calibrate channel 1 input offset voltage.
Calibrate active channel 2 current measurement range.
Set channel 2 current measurement calibration constants.
Query channel 2 current measurement calibration constants.
Calibrate channel 2 active voltage bias range.
Set channel 2 voltage bias calibration constants.
Query channel 2 voltage bias calibration constants.
Calibrate channel 2 input voltage offset.
Program calibration year, month, day.
Query calibration date.
Program calibration due year, month, day.
Query calibration due date.
Save calibration data in EEPROM.
Lock out calibration.
Query if calibration is locked (1 = locked; 0 = unlocked).
Query number of times Model 2500 has been calibrated.

Model 2500 Service Manual Calibration Reference B-3

Miscellaneous commands

Miscellaneous commands are those commands that perform such functions as unlocking
calibration, saving calibration constants, locking out calibration, and programming date
parameters.

:CODE

(:CALibration:PROTected:CODE)

Purpose To unlock calibration so that you can perform the calibration procedures.

Format :cal:prot:code '<password>'

Parameter Up to an 8-character string including letters and numbers.

Description The :CODE command sends the password/code and enables calibration

when performing these procedures via remote. The correct password
must be sent to the unit before sending any other calibration command.
The default remote password is KI002500.

Note • The :CODE command should be sent only once before performing cali-

bration. Do not send :CODE before each calibration step.

• To change the code, first send the present code, then send the new code.

• The password parameter must be enclosed in single quotes.

• 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.

Example :CAL:PROT:CODE 'KI002500' Send default code of KI002500.

:COUNT?

(:CALibration:PROTected:COUNT?)

Purpose To request the number of times the Model 2500 has been calibrated.

Format :cal:prot:count?

Response Number of times calibrated.

Description The :COUNT? query may be used to determine the total number of

times the Model 2500 has been calibrated.

Example :CAL:PROT:COUNT? Request calibration count.

B-4 Calibration Reference Model 2500 Service Manual

:LOCK

(:CALibration:PROTected:LOCK)

Purpose To lock out calibration.

Format :cal:prot:lock

Query :cal:prot:lock?

Response 0 Calibration unlocked

1 Calibration locked

Description The :LOCK command allows you to lock out calibration after complet-

ing the procedure. Thus, :LOCK performs the opposite of sending the
password with the :CODE command. The :LOCK? query returns cali­bration lock status.

Note To unlock calibration, send the :CODE command with the appropriate

password.

Example :CAL:PROT:LOCK Lock out calibration.

:SAVE

(:CALibration:PROTected:SAVE)

Purpose To save calibration constants in EEROM after the calibration procedure.

Format :cal:prot:save

Description The :SAVE command stores internally calculated calibration constants

derived during calibration in EEROM. EEROM is non-volatile memory,
and calibration constants will be retained indefinitely once saved. Gen­erally, :SAVE is sent after all other calibration steps (except for
:LOCK).

Note Calibration will be only temporary unless the :SAVE command is sent to per-

manently store calibration constants. Calibration data will not be saved if cal­ibration was not unlocked by sending the :CODE command or if invalid
calibration data exists.

Example :CAL:PROT:SAVE Save calibration constants.