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.