Tektronix TX3, TX1 Service Manual

Service Manual

TX1 and TX3
True RMS Digital Multimeter

070-9893-01

Warning

The servicing instructions are for use by qualified
personnel only. To avoid personal injury, do not
perform any servicing unless you are qualified to
do so. Refer to all safety summaries prior to
performing service.

Copyright © T ektronix, Inc. All rights reserved.
T ektronix products are covered by U.S. and foreign patents, issued and pending. Information in this publication supercedes

that in all previously published material. Specifications and price change privileges reserved.
Printed in the U.S.A.
T ektronix, Inc., P.O. Box 1000, Wilsonville, OR 97070–1000
TEKTRONIX and TEK are registered trademarks of T ektronix, Inc.

WARRANTY

T ektronix warrants that the products that it manufactures and sells will be free from defects in materials and workmanship
for a period of three (3) years from the date of shipment. If a product proves defective during this warranty period,
T ektronix, at its option, either will repair the defective product without charge for parts and labor, or will provide a
replacement in exchange for the defective product.

In order to obtain service under this warranty, Customer must notify Tektronix of the defect before the expiration of the
warranty period and make suitable arrangements for the performance of service. Customer shall be responsible for
packaging and shipping the defective product to the service center designated by T ektronix, with shipping charges prepaid.
T ektronix shall pay for the return of the product to Customer if the shipment is to a location within the country in which the
T ektronix service center is located. Customer shall be responsible for paying all shipping charges, duties, taxes, and any
other charges for products returned to any other locations.

This warranty shall not apply to any defect, failure or damage caused by improper use or improper or inadequate
maintenance and care. T ektronix shall not be obligated to furnish service under this warranty a) to repair damage resulting
from attempts by personnel other than T ektronix representatives to install, repair or service the product; b) to repair
damage resulting from improper use or connection to incompatible equipment; c) to repair any damage or malfunction
caused by the use of non-T ektronix supplies; or d) to service a product that has been modified or integrated with other
products when the effect of such modification or integration increases the time or difficulty of servicing the product.

THIS WARRANTY IS GIVEN BY TEKTRONIX IN LIEU OF ANY OTHER WARRANTIES, EXPRESS OR
IMPLIED. TEKTRONIX AND ITS VENDORS DISCLAIM ANY IMPLIED WARRANTIES OF
MERCHANTABILITY OR FITNESS FOR A PAR TICULAR PURPOSE. TEKTRONIX’ RESPONSIBILITY TO
REP AIR OR REPLACE DEFECTIVE PRODUCTS IS THE SOLE AND EXCLUSIVE REMEDY PROVIDED TO
THE CUSTOMER FOR BREACH OF THIS WARRANTY. TEKTRONIX AND ITS VENDORS WILL NOT BE
LIABLE FOR ANY INDIRECT , SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES IRRESPECTIVE
OF WHETHER TEKTRONIX OR THE VENDOR HAS ADVANCE NOTICE OF THE POSSIBILITY OF SUCH
DAMAGES.

Service Assurance

If you have not already purchased Service Assurance for this product, you may do so at any time during the product’s
warranty period. Service Assurance provides Repair Protection and Calibration Services to meet your needs.

Repair Protection extends priority repair services beyond the product’s warranty period; you may purchase up to three
years of Repair Protection.

Calibration Services provide annual calibration of your product, standards compliance and required audit documentation,
recall assurance, and reminder notification of scheduled calibration. Coverage begins upon registration; you may purchase
up to five years of Calibration Services.

Service Assurance Advantages

H Priced well below the cost of a single repair or calibration
H Avoid delays for service by eliminating the need for separate purchase authorizations from your company
H Eliminates unexpected service expenses

For Information and Ordering

For more information or to order Service Assurance, contact your T ektronix representative and provide the information
below . Service Assurance may not be available in locations outside the United States of America.

Name VISA or Master Card number and expiration
Company date or purchase order number
Address Repair Protection (1,2, or 3 years)
City , State, Postal code Calibration Services (1,2,3,4, or 5 years)
Country Instrument model and serial number
Phone Instrument purchase date

Table of Contents

Specifications

Operating Information

General Safety Summary v. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Service Safety Summary vii. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Preface ix. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Manual Structure ix. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Manual Conventions x. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Related Manuals x. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Contacting T ektronix x. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Introduction xi. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Service Strategy xi. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Service Offerings xi. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Before You Begin xii. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Specifications 1–1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Operating Information 2–1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Front and Rear Panel Overview 2–1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Display Indicators 2–3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Measurement Function Knob 2–4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Input Connectors 2–5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Button and Softkey Overview 2–5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Softkeys 2–8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Setup Menu 2–8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Battery Replacement 2–10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Theory of Operation

Theory of Operation 3–1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Performance Verification

Performance Verification 4–1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

T est Equipment 4–2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Set Up 4–3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Verification Procedure 4–4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

TX1 Test Record 4–11. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

TX3 Test Record 4–17. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Adjustment Procedure

Adjustment Procedure 5–1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Options

Options 6–1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

TX1 and TX3 True RMS Digital Multimeter Service Manual

i

Table of Contents

Maintenance

Replaceable Parts

Maintenance 7–1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Related Maintenance Procedures 7–1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Preparation 7–2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Inspection and Cleaning 7–3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Disassembly and Assembly Procedures 7–5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Troubleshooting 7–18. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Repackaging Instructions 7–22. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Replaceable Parts 8–1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Parts Ordering Information 8–1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Using the Replaceable Parts List 8–2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

ii

TX1 and TX3 True RMS Digital Multimeter Service Manual

List of Figures

Table of Contents

Figure 2–1: Front panel overview 2–1. . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Figure 2–2: Rear panel overview 2–2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Figure 2–3: Display indicators 2–3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Figure 2–4: Measurement function knob 2–4. . . . . . . . . . . . . . . . . . . . . . .

Figure 2–5: Input connectors 2–5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Figure 2–6: Battery replacement 2–10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Figure 3–1: Simple block diagram 3–2. . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Figure 7–1: Opening and closing the case 7–6. . . . . . . . . . . . . . . . . . . . . . .

Figure 7–2: Internal assembly removal and installation 7–8. . . . . . . . . . .

Figure 7–3: Battery holder removal and installation 7–9. . . . . . . . . . . . . .

Figure 7–4: LCD bezel removal and installation 7–10. . . . . . . . . . . . . . . . .

Figure 7–5: LCD removal and installation 7–11. . . . . . . . . . . . . . . . . . . . . .

Figure 7–6: Circuit board tabs 7–12. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Figure 7–7: Circuit board removal and installation 7–13. . . . . . . . . . . . . .

Figure 7–8: Light diffuser removal and installation 7–14. . . . . . . . . . . . . .

Figure 7–9: Function knob removal 7–16. . . . . . . . . . . . . . . . . . . . . . . . . . .

Figure 7–10: Function knob and switch keypad installation 7–17. . . . . . .

Figure 7–11: Troubleshooting start 7–19. . . . . . . . . . . . . . . . . . . . . . . . . . . .

Figure 7–12: Troubleshooting two 7–20. . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Figure 7–13: Troubleshooting three 7–21. . . . . . . . . . . . . . . . . . . . . . . . . . . .

Figure 8–1: Exploded view 8–5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

TX1 and TX3 True RMS Digital Multimeter Service Manual

iii

Table of Contents

List of Tables

Table 1–1: General characteristics 1–1. . . . . . . . . . . . . . . . . . . . . . . . . . . .

Table 1–2: DC voltage characteristics 1–2. . . . . . . . . . . . . . . . . . . . . . . . .

Table 1–3: DC voltage range, resolution, and accuracy 1–2. . . . . . . . . . .

Table 1–4: AC voltage characteristics 1–2. . . . . . . . . . . . . . . . . . . . . . . . . .

Table 1–5: AC voltage range, resolution, and accuracy 1–3. . . . . . . . . . .

Table 1–6: DC current characteristics 1–4. . . . . . . . . . . . . . . . . . . . . . . . .

Table 1–7: DC current range, resolution, and accuracy 1–4. . . . . . . . . . .

Table 1–8: AC current characteristics 1–4. . . . . . . . . . . . . . . . . . . . . . . . .

Table 1–9: AC current range, resolution, and accuracy 1–5. . . . . . . . . . .

Table 1–10: Resistance (W) characteristics 1–5. . . . . . . . . . . . . . . . . . . . . .

Table 1–11: Resistance range, resolution, and accuracy 1–6. . . . . . . . . . .

Table 1–12: Continuity characteristics 1–6. . . . . . . . . . . . . . . . . . . . . . . . .

Table 1–13: Diode test characteristics 1–7. . . . . . . . . . . . . . . . . . . . . . . . .

Table 1–14: Capacitance range, resolution, and accuracy

(5,000 counts only) 1–7. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Table 1–15: Frequency characteristics, resolution, and accuracy 1–7. . .

Table 1–16: Frequency voltage range 1–8. . . . . . . . . . . . . . . . . . . . . . . . . .

Table 1–17: Duty factor characteristics 1–8. . . . . . . . . . . . . . . . . . . . . . . .

Table 1–18: Temperature characteristics 1–8. . . . . . . . . . . . . . . . . . . . . . .

Table 1–19: 1ms peak hold characteristics 1–8. . . . . . . . . . . . . . . . . . . . . .

Table 1–20: Physical characteristics 1–9. . . . . . . . . . . . . . . . . . . . . . . . . . .

Table 1–21: Environmental characteristics 1–9. . . . . . . . . . . . . . . . . . . . .

Table 1–22: Certifications and compliances 1–9. . . . . . . . . . . . . . . . . . . . .

Table 2–1: Setup prompts, definitions, and default values 2–9. . . . . . . . .

Table 4–1: Performance verification checks 4–1. . . . . . . . . . . . . . . . . . . .

Table 4–2: Test equipment 4–2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Table 4–3: TX1 test record results 4–11. . . . . . . . . . . . . . . . . . . . . . . . . . . .

Table 4–4: TX3 test record results 4–15. . . . . . . . . . . . . . . . . . . . . . . . . . . .

Table 7–1: Relative susceptibility to static-discharge damage 7–3. . . . . .

Table 7–2: List of tools 7–5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Table 8–1: Parts list column descriptions 8–2. . . . . . . . . . . . . . . . . . . . . . .

Table 8–2: Manufacturers cross index 8–3. . . . . . . . . . . . . . . . . . . . . . . . .

Table 8–3: Replaceable parts list 8–4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Table 8–4: Standard accessories 8–6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Table 8–5: Optional accessories 8–6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

iv

TX1 and TX3 True RMS Digital Multimeter Service Manual

General Safety Summary

Review the following safety precautions to avoid injury and prevent damage to
this product or any products connected to it. To avoid potential hazards, use this
product only as specified.

Only qualified personnel should perform service procedures.

To Avoid Fire or
Personal Injury

Connect and Disconnect Properly . Do not connect or disconnect probes or test

leads while they are connected to a voltage source.
Observe All Terminal Ratings. To avoid fire or shock hazard, observe all ratings

and markings on the product. Consult the product manual for further ratings
information before making connections to the product.

Do not apply a potential to any terminal, including the common terminal, that
exceeds the maximum rating of that terminal.

Replace Batteries Properly. Replace batteries only with the proper type and rating
specified.

Do Not Operate Without Covers. Do not operate this product with covers or panels
removed.

Use Proper Fuse. Use only the fuse type and rating specified for this product.
Avoid Exposed Circuitry. Do not touch exposed connections and components

when power is present.
Do Not Operate With Suspected Failures. If you suspect there is damage to this

product, have it inspected by qualified service personnel.

Do Not Operate in Wet/Damp Conditions.
Do Not Operate in an Explosive Atmosphere.
Keep Product Surfaces Clean and Dry .

Symbols and Terms

TX1 and TX3 True RMS Digital Multimeter Service Manual

T erms in this Manual. These terms may appear in this manual:

WARNING. Warning statements identify conditions or practices that could result
in injury or loss of life.

CAUTION. Caution statements identify conditions or practices that could result in
damage to this product or other property.

v

General Safety Summary

T erms on the Product. These terms may appear on the product:
DANGER indicates an injury hazard immediately accessible as you read the

marking.
WARNING indicates an injury hazard not immediately accessible as you read the

marking.
CAUTION indicates a hazard to property including the product.
Symbols on the Product. The following symbols may appear on the product:

CAUTION

Refer to Manual

WARNING

High Voltage

Double

Insulated

vi

TX1 and TX3 True RMS Digital Multimeter Service Manual

Service Safety Summary

Only qualified personnel should perform service procedures. Read this Service
Safety Summary and the General Safety Summary before performing any service

procedures.
Do Not Service Alone. Do not perform internal service or adjustments of this

product unless another person capable of rendering first aid and resuscitation is
present.

Use Care When Servicing With Power On. Dangerous voltages or currents may
exist in this product. Disconnect power, remove battery (if applicable), and
disconnect test leads before removing protective panels, soldering, or replacing
components.

To avoid electric shock, do not touch exposed connections.

TX1 and TX3 True RMS Digital Multimeter Service Manual

vii

Service Safety Summary

viii

TX1 and TX3 True RMS Digital Multimeter Service Manual

Preface

Manual Structure

This section contains information needed to properly use this manual to service
the TX1 and TX3 True RMS Digital Multimeters as well as general information
critical to safe and effective servicing of multimeters.

This manual is divided into chapters, such as Specifications and Theory of
Operation. Further, it is divided into subsections, such as Product Description
and Disassembly and Assembly Procedures.

Sections containing procedures also contain introductions to those procedures. Be
sure to read these introductions because they provide information needed to do
the service correctly and efficiently. The following is a brief description of each
manual chapter.

H Specifications contains a product description and tables of the characteristics

and descriptions that apply to it.

H Operating Information includes general information and operating instruc-

tions at the level needed to safely service the multimeters. A statement of the
service strategy is in this section.

H Theory of Operation contains circuit descriptions down to the module level.
H Performance Verification contains a collection of procedures for confirming

that the multimeters function properly and meet warranted limits.

H Adjustment Procedure informs you how to obtain calibration services.
H Options lists the available options for the TX1 and TX3 meters.
H Maintenance contains information and procedures for doing preventive and

corrective maintenance. This includes cleaning instructions and disassembly
and assembly instructions.

H Replaceable Parts includes a table of all replaceable parts, their descriptions,

and their Tektronix part numbers.

TX1 and TX3 True RMS Digital Multimeter Service Manual

ix

Preface

Manual Conventions

This manual uses certain conventions which you should become familiar with
before doing service.

Safety

Symbols

Related Manuals

Contacting Tektronix

Symbols and terms related to safety appear in the Safety Summary found at the
beginning of this manual.

Refer to the Safety section in this manual to learn about the symbols used in this
manual.

The TX1 and TX3 digital multimeters are shipped with a user manual. Refer to
the user manual for detailed operating instructions.

Product
Support

For application-oriented questions about a Tektronix measure­ment product, call toll free in North America:
1-800-TEK-WIDE (1-800-835-9433 ext. 2400)
6:00 a.m. – 5:00 p.m. Pacific time

Or, contact us by e-mail:
[e-mail]

For product support outside of North America, contact your
local Tektronix distributor or sales office.

Service
Support

For other
information

To write us Tektronix, Inc.

x

Contact your local Tektronix distributor or sales office. Or, visit
our web site for a listing of worldwide service locations.

http://www.tektronix.com
In North America:

1-800-TEK-WIDE (1-800-835-9433)
An operator will direct your call.

P.O. Box 1000
Wilsonville, OR 97070-1000

TX1 and TX3 True RMS Digital Multimeter Service Manual

Introduction

Service Strategy

Service Offerings

This manual contains all the information needed for periodic maintenance of the
TX1 and TX3 True RMS Digital Multimeters.

All replaceable parts are listed in Table 8–3 Replaceable parts list. To remove and
replace any parts, follow the instructions in Dissasembly and Assembly Proce-
dures found in Chapter 7.

Tektronix provides service to cover repair under warranty as well as other
services that may provide a cost-effective answer to your service needs.

Whether providing warranty repair service or any of the other services listed
below, Tektronix service technicians, trained on Tektronix products, are best
equipped to service your TX1 and TX3 True RMS Digital Multimeters.
Tektronix technicians are apprised of the latest information on improvements to
the product as well as the latest options to the product.

Warranty Repair Service

Repair or Calibration

Service

Tektronix warrants this product for three years from date of purchase. (The
warranty appears after the title page and copyright page in this manual.)
Tektronix technicians provide warranty service at most Tektronix service
locations worldwide. Your Tektronix product catalog lists all service locations
worldwide.

The following services may be purchased to tailor repair and/or calibration of
your TX1 and TX3 True RMS Digital Multimeters to fit your requirements.

At-Depot Service. Tektronix offers several standard-priced adjustment (calibra­tion) and repair services:

H A single repair and/or adjustment.
H Calibrations using equipment and procedures that meet the traceability

standards specific to the local area.

H Annual maintenance agreements that provide for either calibration and repair

or calibration only.

TX1 and TX3 True RMS Digital Multimeter Service Manual

xi

Introduction

Of these services, the annual maintenance agreement offers a particularly
cost-effective approach to service for many owners. Such agreements can be
purchased to span several years.

Self Service

Before You Begin

Tektronix supports self service repair by providing replaceable parts. See the
Replaceable Parts chapter for a list of all replaceable parts.

This manual is for servicing the TX1 and TX3 True RMS Digital Multimeters.
To prevent injury to yourself or damage to the meter, do the following tasks
before you attempt service:

H Read the Safety Summary found at the beginning of this manual.
H Read Service Strategy in this section.

When using this manual for servicing, be sure to read and follow all warnings,
cautions, and notes.

xii

TX1 and TX3 True RMS Digital Multimeter Service Manual

Specifications

Specifications

All specifications are warranted, unless noted as typical, for the rated tempera­ture range of 23_ C

± 5_ C at less than 80% relative humidity.

T able 1–1: General characteristics

Characteristics Description

LCD display digits 3$@5 (default) or 4$@5

Display counts 5,000 (default) or 50,000

Bargraph 20 segment, updated 20 times per second

Memory locations TX1: 10, TX3: 30

Out of range indicator OL: overrange

Ur: underrange

Low voltage indicator Battery symbol shows on LCD at 2.0 V .

Meter powers down at 1.5 V .
Battery life 100 hours continuous use with backlight off (typical)
Auto-off Adjustable, 30 minute default
Power source Two AA 1.5 V alkaline batteries (IEC LRG or ANSI/NEDA

15A)
Maximum input voltage be-

tween terminals and between
terminals and earth

Maximum open circuit voltage
when utilizing the A terminal

Overload protection, V terminal 1000 V
F1 fuse protection 15 A (1000 V) fast
Backlight Green LEDs

1

If meter is exposed to water, have it inspected by qualified service personnel.

1000 V

600 V

Installation Category III (CAT III)

RMS

CAT III

RMS

(1500 Vpk) for all functions

RMS

1

TX1 and TX3 True RMS Digital Multimeter Service Manual

1–1

Specifications

R

e

T able 1–2: DC voltage characteristics

Characteristic Description

Settling time 3 readings (typical)
Reading rate 5,000 ct.: 4 readings per second

50,000 ct.: 1 reading per second

Rejection ratio

Common mode 120 dB at DC or 50 Hz or 60 Hz
Normal mode 60 dB at 50 Hz or 60 Hz

Input impedance 10 MW (typical)

T able 1–3: DC voltage range, resolution, and accuracy

Resolution Accuracy

1

ang

0.5 V 100 mV 10 mV
5 V 1 mV 100 mV

5,000 counts 50,000 counts TX1 TX3

± (0.07% + 1 ± (0.05% + 1
count) count)

50 V 10 mV 1 mV
500 V 100 mV 10 mV
1000 V 1 V 100 mV
T emperature coef ficient Add (0.005% + 0.1 ct.)/°C to accuracy

beyond rated temperature range.

1

Accuracy in 50,000-count mode is % + 10 counts.

T able 1–4: AC voltage characteristics

Characteristic Description

Input impedance 10 MW in parallel with <100 pF (typical)
Settling time 4 readings (typical)
Reading rate 5,000 ct.: 4 readings per second

50,000 ct.: 1 reading per second

Common mode

60 dB at DC to 60 Hz

rejection ratio
Crest factor, maximum Full scale: 3

Half scale: 6

1

AC+DC

total RMS volts

AC (RMS) accuracy + 0.1% + 1 count

accuracy

1–2

TX1 and TX3 True RMS Digital Multimeter Service Manual

T able 1–4: AC voltage characteristics (cont.)

R

e

±

±

s

s

Characteristic Description

1

AC DC

Upper display frequency
(5,000 counts)

dB reference
dBm reference

1
2

dual display accuracy DC Accuracy + 0.05% + 1 count

AC RMS Accuracy + 0.1% + 1 count

Accuracy ±(0.002% + 1 count) for 20 Hz to 20 kHz
Sensitivity 10% of selected voltage range

2

2

1 V

(adjustable)

RMS

775 mV across 600 W (1 mW)

5,000-count mode only.
dB readout = 20 log (main display readout/ref), where ref = 1 V is the default.

dBm readout = 10 log (main display readout2/R), where R=600 W.

Specifications

T able 1–5: AC voltage range, resolution, and accuracy

Resolution Accuracy

ang

0.5 V 100 mV 10 mV
5 V 1 mV 100 mV

5,000 counts 50,000 counts TX1 TX3

40 Hz – 20 kHz:

(0.6% + 2

counts)

50 V 10 mV 1 mV

2

500 V
1000 V

100 mV 10 mV

2

1 V 100 mV 40 Hz – 10 kHz:

± (0.6% + 2
counts)

T emperature coef ficient AC: Add (0.03% + 0.1 ct.)/°C beyond

rated temperature range.
AC+DC: Add (0.06% + 0.1 ct.)/°C

beyond rated temperature range.

1

Accuracy in 50,000-count mode is % + 20 counts.

2

For voltages u 100 V , the maximum volts–Hz product is t 10 MVHz.

1

40 Hz – 20 kHz:

(0.4% + 2

counts)

40 Hz – 10 kHz:
± (0.4% + 2
counts)

TX1 and TX3 True RMS Digital Multimeter Service Manual

1–3

Specifications

R

e

2

T able 1–6: DC current characteristics

Characteristics Description

Burden voltage 5 mA to 5 A: 0.3 V max.

10 A: 0.5 V max.

Percent 4-20 mA (calculated in
50 mA range)

4 mA = 0%

20 mA = 100%
Settling time 4 readings (typical)
Reading rate 5,000 ct.: 4 readings per second

50,000 ct.: 1 reading per second

T able 1–7: DC current range, resolution, and accuracy

Resolution Accuracy

ang

500 A 100 nA 10 nA ± (0.2% + 4 counts)
5 mA 1 A 100 nA
50 mA 10 A 1 A
500 mA 100 A 10 A
5 A 1 mA 100 A ± (0.4% + 2 counts)
10 A

(15 A for
3 minutes)

5,000 counts 50,000 counts TX1 TX3

± (0.2% + 2 counts)

10 mA 1 mA ±(0.8% + 2 counts)

1

2
2

1–4

T emperature coef ficient Add (0.05% + 0.1 ct.)/°C beyond rated

temperature range.

1

Accuracy in 50,000-count mode is % + 40 counts.

2

Accuracy in 50,000-count mode is % + 20 counts.

T able 1–8: AC current characteristics

Characteristics Description

Burden voltage 0.5 mA to 5 A: 0.9 V max.

10 A: 1.0 V max.

1

AC+DC

Accuracy AC RMS amps accuracy + DC amps accuracy

Upper display frequency

Accuracy ±(0.002% + 1 count) for 20 Hz to 5 kHz
Sensitivity 10% of range

TX1 and TX3 True RMS Digital Multimeter Service Manual

T able 1–8: AC current characteristics (cont.)

R

e

Characteristics Description

Settling time 4 readings (typical)
Reading rate 5,000 ct.: 4 readings per second

50,000 ct.: 1 reading per second

1

5,000-count mode only.

T able 1–9: AC current range, resolution, and accuracy

Specifications

Resolution Accuracy

ang

5,000 counts 50,000 counts TX1 TX3

0.5 mA 100 nA 10 nA
5 mA 1 mA 100 nA
50 mA 10 mA 1 mA

40 Hz – 1 kHz: ± (0.6% + 2 counts)
>1 kHz – 3 kHz: ± (1.0% + 2 counts)
>3 kHz – 5 kHz: ± (2.0% + 2 counts)

1,2

500 mA 100 mA 10 mA
5 A 1 mA 100 mA
10 A

10 mA 1 mA
(15 A for
3 minutes)

T emperature coef ficient Add (0.05% + 0.1 ct.)/°C beyond rated

temperature range.

1

Accuracy in 50,000-count mode is % + 20 counts.

2

5% of range.

T able 1–10: Resistance (W) characteristics

Characteristics Description

Update rate 5,000 ct.: 2 readings per second

50,000 ct.: 1 reading per second
50 MW: 1 reading per second

Settling time 50 W to 5 MW range: 3 readings (typical)

50 MW range: 4 readings (typical)
Compliance voltages (typical) 0.6 V (50 W and 500 W range is 1.3 V)
Common mode rejection ratio 60 dB at DC, 50 Hz, or 60 Hz
Normal mode rejection ratio 20 dB at  50 Hz

TX1 and TX3 True RMS Digital Multimeter Service Manual

1–5

Specifications

R

e

T able 1–11: Resistance range, resolution, and accuracy

Resolution Accuracy

ang

50  0.01 
500  0.1  0.01  ± (0.1% + 4 counts)
5 k 1  0.1 

5,000 counts 50,000 counts TX1 TX3

1

–– ± (0.1% + 10 counts)

± (0.1% + 2 counts)

2
3

50 k 10  1 
500 k 100  10 
5 M 1 k 100  ± (0.4% + 4 counts)
50 M 10 k

1

–– ± (1.0% + 4 counts)

2

2

T emperature coef ficient 50  to 500 k: Add (0.03% + 0.1

ct.)/°C beyond rated temperature range.
5 M to 50 M: Add (0.2% + 0.1 ct.)/°C

beyond rated temperature range.

1

5,000 count mode only.

2

Accuracy in 50,000-count mode is % + 40 counts.

3

Accuracy in 50,000-count mode is % + 20 counts.

T able 1–12: Continuity characteristics

Characteristics Description

Continuity threshold Beeper sounds when resistance is 100  or less (typical)
Response time 1 ms

T able 1–13: Diode test characteristics

Characteristics Description

Test current (typical) 0.35 mA
Test voltage 2.8 V maximum, open circuit
Accuracy ± 1.0%

1–6

TX1 and TX3 True RMS Digital Multimeter Service Manual

Specifications

R

e

Resoluti

1

T able 1–14: Capacitance range, resolution, and accuracy (5,000 counts
only)

Accuracy

ang

on

TX1 TX3

5 nF 1 pF ± (1.0% + 5 counts) (using D mode)
50 nF 10 pF ± (1.0% + 3 counts) (using D mode)

2

500 nF 100 pF

± (1.0% + 3 counts)
5 mF 1 nF
50 mF 10 nF

± (3.0% + 3 counts)
500 mF 100 nF
5 mF 1 mF
50 mF 10 mF
T emperature coef ficient Add (0.05% + 0.1 ct.)/°C beyond rated

temperature range.

1

5,000 count mode only.

2

1% of range.

T able 1–15: Frequency characteristics, resolution, and accuracy

Characteristics Description

Signal coupling AC
Minimum frequency 0.5 Hz
Maximum frequency 1 MHz
Accuracy ±(0.002%) + 1 count
Best resolution 10,000 count: 0.01 Hz

T emperature coef ficient Add 0.00004%/(°C)2 beyond rated temperature range.

T able 1–16: Frequency voltage range

Range Sensitivity, 10 Hz - 100 kHz Sensitivity, 1 MHz

500 mV 100 mV ––
5 V 500 mV 2 V
50 V 5 V 20 V

TX1 and TX3 True RMS Digital Multimeter Service Manual

100,000 count: 0.001 Hz

1

1–7

Specifications

T able 1–16: Frequency voltage range (Cont.)

Range Sensitivity, 1 MHz

Sensitivity, 10 Hz - 100 kHz

1

500 V 50 V ––

1

For voltages  100 V , the maximum volts–Hz product is  10 MVHz.

T able 1–17: Duty factor characteristics

Characteristics Description

Range 1 Hz to 100 kHz
Accuracy ±(0.1% + 0.05% per kHz) for 5 V input (logic signals only)
Signal coupling DC
Resolution 0.1%
Sensitivity 30% of range

T able 1–18: Temperature characteristics

Characteristics Description

Main display

Range –50_ C to +980_ C
Accuracy ±3_C

1

(typical)

Thermocouple type K

Upper display

Accuracy ± 3_C of ambient temperature (typical)

1

Use the water and ice offset calibration method on page 2–9 for accuracy to ±1.0 °C.

T able 1–19: 1ms peak hold characteristics

Characteristics Description

Accuracy

1

1

5,000-count mode only.

Specified voltage or current measurement ±30 counts of the
peak value of a single 1ms pulse.

1–8

TX1 and TX3 True RMS Digital Multimeter Service Manual

T able 1–20: Physical characteristics

Characteristic Description

Dimensions (H  W  D) 38 mm  88 mm  183 mm

(without holster)

Weight (with batteries) 383 g (13.5 oz)

With holster 539 g (1 lb 3 oz)

T able 1–21: Environmental characteristics

Characteristic Description

Temperature

Operating –10 to +50_ C
Non-operating (storage) –40 to +60_ C

Humidity –40 to +35_ C: 80%

+35 to +40_ C: 70%
+40 to +60_ C: 55%

Specifications

Altitude

Operating 2,000m (6,562 ft)

For altitudes from 2,000 m up to 5,000 m (16,404 ft) derate
voltage input to 600 VAC CAT III.

Non-operating (storage) 12,300 m (40,354 ft)

Vibration

Operating 2.66 g
Non-operating 3.48 g

, 5 to 500 Hz, 3 axes (10 minutes each)

RMS

, 5 to 500 Hz, 3 axes (10 minutes each)

RMS

TX1 and TX3 True RMS Digital Multimeter Service Manual

1–9

Specifications

T able 1–22: Certifications and compliances

Category Standards or description

EC Declaration of Conformity
– EMC

Australia/New Zealand Decla­ration of Conformity – EMC

Meets intent of Directive 89/336/EEC for Electromagnetic
Compatibility. Compliance was demonstrated to the following
specifications as listed in the Official Journal of the European
Union:

EN 55011 Class A Radiated Emissions
EN 50082-1 Immunity:

IEC 801-2 Electrostatic Discharge Immunity
IEC 801-3 RF Electromagnetic Field

Immunity

1

Add 25 counts (250 counts in 50,000 count mode) to
the accuracy specifications when in the presence of
an RF field as defined in IEC801–3.

2

Amps DC: Add 60 counts (600 counts in 50,000 count
mode) to the amps accuracy specifications when in
the presence of an RF field as defined in IEC801–3.

Complies with EMC provision of Radiocommunications Act
per the following standard(s):

1,2

AS/NZS 2064.1/2 Industrial, Scientific, and Medical
Equipment: 1992

EC Declaration of Conformity
– Low Voltage

Compliance was demonstrated to the following specification
as listed in the Official Journal of the European Union:

Low Voltage Directive 73/23/EEC, amended by 93/69/EEC
EN 61010-1/A2:1995

Safety requirements for electrical equipment for
measuring control, and laboratory use.

U.S. Nationally Recognized
Testing Laboratory Listing

UL31 11-1 – Standard for electrical measuring and test
equipment.

Canadian Certification CAN/CSA C22.2 No. 1010.1

Safety requirements for electrical equipment for
measurement, control, and laboratory use.

Additional Compliance IEC61010-1/A2:1995

Safety requirements for electrical equipment for
measurement, control, and laboratory use.

1–10

TX1 and TX3 True RMS Digital Multimeter Service Manual

T able 1–22: Certifications and compliances (cont.)

ree

Category Standards or description

Installation Category
Descriptions

Terminals on this product may have different installation
(overvoltage) category designations. The installation
categories are:

CA T III

Distribution-level mains (usually permanently connected).
Equipment at this level is typically in a fixed industrial
location.

CA T II

Local-level mains (wall sockets). Equipment at this level
includes appliances, portable tools, and similar products.
Equipment is usually cord-connected.

CA T I

Secondary (signal level) or battery operated circuits of
electronic equipment.

Specifications

Pollution Deg

A measure of the contaminates that could occur in the
environment around and within a product. Typically the
internal environment inside a product is considered to be the
same as the external. Products should be used only in the
environment for which they are tested.

Pollution Degree 2

Normally only dry, nonconductive pollution occurs.
Occasionally a temporary conductivity that is caused by
condensation must be expected. This location is a typical
office/home environment. Temporary condensation
occurs only when the product is out of service.

TX1 and TX3 True RMS Digital Multimeter Service Manual

1–11

Specifications

1–12

TX1 and TX3 True RMS Digital Multimeter Service Manual

Operating Information

Operating Information

This chapter provides basic information about the controls and functions of the
TX1 and TX3 meters. For more detailed operating information, refer to the User
manual supplied with the meter.

Front and Rear Panel Overview

1

2
3
4
5

6
7

8
9

10

FUSED 600V

15A/3MINUTES

CATIII

10A

1000V

1 Extra large LCD display with dual numeric readout.
2 Measurement function knob – Use to select a measurement.
3 Blue Button – Use to access 1ms, MEM, and Setup menu.
4 RANGE Button – Use to set measurement range.
5 M/M/A Button – Use to set meter to MIN/MAX/AVG or 1ms modes.
6 Softkeys – Use with measurement function knob to select measurements.
7 Backlight Button – Use to turn backlight on and off.
8 HOLD Button – Use to freeze display.
9 D Button – Use to make relative measurements and access the memory.

10 Input connectors.

Figure 2–1: Front panel overview

TX1 and TX3 True RMS Digital Multimeter Service Manual

2–1

Operating Information

1

Auto Off



2

3

4

5

1 Press and hold options – Activate by holding down the specified button for two

seconds while the meter is on.

2 Power-up options – Activate by holding down the specified button while turning

on the meter.

3 Compliance and battery and fuse replacement information.
4 Serial number and barcode tag.

5 Removable battery cover.

2–2

Figure 2–2: Rear panel overview

TX1 and TX3 True RMS Digital Multimeter Service Manual

Display Indicators

Operating Information

6

1

2

3
4

5

1

Special feature indicators

2 Low battery indicator
3 Delta indicator
4 Blue button and memory

mode indicators

5 Bargraph

7

8

9

10

11

6 Upper display

7 Upper display units
8 Main display
9 Main display units

10 Range indicators

11 Softkey menus

Figure 2–3: Display indicators

TX1 and TX3 True RMS Digital Multimeter Service Manual

2–3

Operating Information

Measurement Function Knob

TX1

TX3

Figure 2–4: Measurement function knob

OFF Turns off the meter. Setup parameters and stored measurements are saved.

V. Volts AC RMS, Volts DC, Volts AC DC dual display, Volts AC+DC total

RMS, dB, and dBm.

Hz. Frequency measurements. Duty factor also shows if it is turned on in the
Setup menu.

W/

. Access to resistance and continuity measurements and diode test.

. Capacitance measurements.

_C. Temperature measurements in degrees Celsius or Fahrenheit.

A. Amps AC RMS, Amps DC, Amps AC + DC total RMS, Amps AC DC dual

display, and Amps DC 4-20 mA% (process control loop measurement).

2–4

TX1 and TX3 True RMS Digital Multimeter Service Manual

Input Connectors

Operating Information

FUSED 600V

10A

15A/30 SECONDS

CATIII

1000V

Figure 2–5: Input connectors

A. Input connector for current measurements up to 15 A (10 A continuous, or

15 A for 3 minutes on and 10 minutes off). Successive high current measure­ments (above 10 A) require a 10 minute cooling time between measurements.
Rating is 600 V open circuit voltage.

COM. Common connector. All measurements are referenced to this connector.

V. Input connector for volts, frequency, ohms, continuity, diode, capacitance, and

temperature measurements. Rating is 1000 V CAT III for all V input connector
measurements.

WARNING. To avoid personal injury, do not attach meter leads with the battery
cover removed.

CAUTION. To avoid damaging the meter, do not attempt to measure current with
the batteries removed.

TX1 and TX3 True RMS Digital Multimeter Service Manual

2–5

Operating Information

Button and Softkey Overview

Blue Button

RANGE Button

M/M/A (Minimum,

Maximum, and Average)

Button

1ms (1 ms Peak Hold)

T o access functions in blue text, press the blue button and then press a function button
while the indicator is on. The indicator shows on the display for five
seconds.

Press and hold the blue button for two seconds to access the Setup menu. See
page 2–8 for more information about the Setup menu.

Use the RANGE button to manually select a range. Press and hold RANGE for
two seconds to return the meter to auto range mode. The meter is in auto range
mode when the

The range and units are displayed above the
bargraph.

Press this button to scroll through the live, maximum, minimum, maximum–
minimum, and average values. The elapsed time between the last recorded event
and the start of the test shows in the upper display.

Press and hold the M/M/A button for two seconds to exit M/M/A mode.

1ms (1 ms Peak Hold)

indicator is on.

indicator, to the right of the

Backlight Button

To activate 1 ms peak hold, first press the blue button and then the M/M/A
button while the
LCD displays the
is 5,000 counts. Live and average (AVG) readings are not available in 1ms peak
hold mode.

You can use 1ms peak hold when you take AC or DC measurements. The meter
only records events that have a pulse width that is greater than 1 ms.

Press the M/M/A button to view 1ms peak hold minimum and maximum values.
The MAX value shown is the value of the positive peaks and the MIN value
shown is the value of the negative peaks.

Press and hold the M/M/A button for two seconds to exit 1ms peak hold mode.

Press the
the Setup menu to adjust the backlight timeout setting. Use the Setup menu
information on page 2–8 to adjust the setting for the backlight.

button to turn the backlight on or off. Adjust the LOFF setting in

indicator shows on the display. When in 1 ms mode, the

and indicators. Display resolution in 1ms peak hold

2–6

TX1 and TX3 True RMS Digital Multimeter Service Manual

Operating Information

HOLD Button

Auto Hold

D Button (Making Relative

Measurements)

Press HOLD to turn hold mode on and off. When you activate the hold feature,
the meter beeps, freezes the display, and displays the
freezes the display so you can remove the probes from the test points without
losing the measurement reading.

To activate auto hold, press down on the HOLD button until
the display. Auto hold is not available for capacitance or AC DC measurements.

In auto hold mode the display automatically freezes and the meter beeps when
the measurement reading stabilizes. The displayed value will be updated when
the meter stabilizes on a new measurement value.

Auto hold is useful when it is not possible for you to press the HOLD button or
see the meter display while probing and taking measurements.

Use this button to set the meter to delta (D) mode and make relative measure­ments. The reference value for the D measurement can be a measured, a stored,
or a programmed value.

D Relative to a Measured Value. When you take the measurement and the meter
settles on the measurement value, press the D button.

indicator. Hold mode

appears on

For subsequent readouts, the measured reference value is subtracted from the
actual measurement.

D Relative to a Saved Value. Use the measurement function knob and softkeys to
set the meter to the measurement function you want. Use the memory informa­tion on page 2–8 to recall (RCL) a reference value from memory, then press the
D button. To exit delta mode, press the D button.

For subsequent readouts, the recalled reference value is subtracted from the
actual measurement.

D Relative to a Programmed Value. Use the measurement function knob and
softkeys to set the meter to the measurement function and range you want and
then press the D button. While the meter is in delta mode, press and hold the
blue button until the Setup menu appears. Use the softkeys to edit rEF to the
desired value and press softkey 4 for OK. To exit delta mode, press the D button.

For subsequent readouts the programmed reference value is subtracted from the
actual measurement. The programmed reference value is lost when you turn off
the meter.

You can also use the D button to make relative dB (DdB) measurements.

TX1 and TX3 True RMS Digital Multimeter Service Manual

2–7

Operating Information

MEM (Memory)

Use the memory mode to store and recall measurement values. No data is lost
during power cycles.

To activate the MEM (memory) mode, press the blue button and then the 
button while
selections: STO, RCL, CLR, and EXIT.

STO. Select STO to store the held value in the next available memory location.
The memory location number momentarily shows on the upper display. If no
memory locations are available, FULL shows on the upper display for two
seconds and nothing is stored.

To overwrite an existing memory value, recall the memory location using the
RCL button, press CLR, then press STO to store the new value in this location.

RCL. Select RCL to scroll through the stored values in reverse order. The upper
display momentarily shows the memory location while the main display shows
the value stored in that location.

CLR. Select CLR to clear the currently selected memory location. The location is
replaced with “-----”.

shows on the LCD display. The display shows four softkey

Softkeys

Setup Menu

To clear all memory locations, press and hold the CLR button for five seconds.

?

A

shows on the display next to the CLR enunciator. The word donE shows on

the display indicating that all memory locations are clear and you can release the
button. If you release the button before the word donE shows, no data is cleared
from the memory.

EXIT. Select EXIT to exit memory mode. You can also exit memory mode by
pressing any button.

Each setting on the measurement function knob may activate one or more
softkey settings on the LCD. If there is more than one measurement for a
function knob setting, a softkey menu appears on the display. Press the corre­sponding softkey to select the desired measurement.

The Setup menu allows you to customize default settings. To activate the Setup
menu, press and hold the blue button for two seconds.

Use the softkeys as shown in the following table to edit setup values. Setup
menu values are saved when you turn off the meter, except for reference values.

2–8

TX1 and TX3 True RMS Digital Multimeter Service Manual

Operating Information

Softkey

Function Press to increase

+

setting value.

–

Press to decrease
setting value.

←

Press to step to
next digit in setting
value.

OK

Press to save set­ting and move to
next setup parame­ter.

The following table lists the setup menu prompts, the definition of parameters,
and default values.

T able 2–1: Setup prompts, definitions, and default values

Upper dis­play prompt

POFF Sets auto-off time (in minutes). 30 minutes
LOFF Sets backlight auto-off time (in seconds). 60 seconds
bEEP Toggles beeper on and off. ON
HrES Changes display to 50,000 counts. OFF
POL (Duty) Scrolls through OFF, POS (positive duty factor), and

EdGE (Hz) Toggles between POS (positive edge) and NEG

1

rEF

(D)rEF(dB) 1Changes the reference value for dB measurements. 1 V

1

Meter must be in D or dB mode to access these setup parameters.

Definition of parameter
(press OK to cycle through parameters)

NEG (negative duty factor).

(negative edge) triggering in Hz measurement.
Changes the reference value for delta measurements. Value before 

Default
value

OFF

Positive (rising)

button is pressed

Helpful Tip: Increased

Temperature Accuracy

To achieve high accuracy temperature measurements to ±1.0 °C it is necessary to
calibrate the meter to account for any thermocouple offset. Temperature accuracy
without performing the following calibration is ±3 °C:

1. Turn on the meter in the environment you will make the measurements.

2. Fill a wide, shallow container with ice and water. Stir the ice and water

mixture for two or three minutes to evenly distribute the temperature of the
mixture. Place the container next to the meter and submerge the tip of the
bead probe in the ice and water.

3. While in °C or °F mode, allow the temperature reading to stabilize on a
value (this value should be very close to 0 °C for °C mode or 32.0 °F for °F
mode). Any deviation from 0 °C or 32 °F represents the thermocouple’s
offset.

4. Once the reading stabilizes, press and hold softkey 1 for °C mode or softkey
2 for °F mode for five seconds until the display shows 0000 or 0032.

TX1 and TX3 True RMS Digital Multimeter Service Manual

2–9

Operating Information

Battery Replacement

This calibrates the meter for the operating environment.  shows in the upper
display. If you hear an error beep, the offset is greater than ±5 °C. You can repeat
this calibration at any time. To undo this calibration, return the meter to factory
settings by pressing both the blue button and M/M/A button while powering up
the meter.

To insure accuracy of temperature measurements, you should follow this
procedure when using other K-type thermocouple probes with the TX Series
True RMS Digital Multimeters because accuracy specifications vary in different
types of probes.

NOTE. Observe proper polarity on the probe adapter and do not calibrate the
offset immediately following high amperage measurements.

Batteries (2 AA alkaline or
rechargeable)

Battery cover

Figure 2–6: Battery replacement

When you replace a battery the meter calibration is not affected and the stored
data is not lost.

Remove the battery cover only in a clean, dry environment.
See the Specifications chapter for the description and part numbers of the

replaceable batteries.

2–10

TX1 and TX3 True RMS Digital Multimeter Service Manual

Theory of Operation

Theory of Operation

This chapter provides a simple operating diagram of the TX1 and TX3 meters
using the major circuit blocks.

General Description

As illustrated with the block diagram, the TX1 and TX3 meters have five main
elements in the signal path.

H Signal conditioning
H A chip
H B chip
H Microprocessor
H Display

Signal Conditioning

A Chip

B Chip

Microprocessor

LCD

The attenuators (compensated with parallel capacitors) condition (divide) the
input signal to a level appropriate for the ICs. The conditioning includes
transforming all inputs to voltage. The current shunts (selected by FET switches)
provide the correct voltage drops. For ohms and capacitance, the inputs are
configured as current sources and the voltage drop across the input impedance is
measured.

Chip A works with the attenuator and input conditioners to transform the signal
to levels appropriate for chip B. Chip A has multiple inputs and three outputs. A
0.5 V analog signal is sent to chip B for analog-to-digital conversion.

Chip B does the analog-to-digital conversion, provides all calculations, and sends
the digital signals to the microprocessor.

The microprocessor controls chips A and B and all relays upon receiving
commands from the function switch and buttons (or the infrared PC interface
port).

The liquid crystal display is a 160 segment, dual display capable of displaying
50,000 counts in the main display and 5,000 counts in the upper display. The
backlight is provided by LEDs located on the circuit board.

TX1 and TX3 True RMS Digital Multimeter Service Manual

3–1

Theory of Operation

10 M

5 V

A Chip

Digital

register

5 V 3 V

B Chip

A/D

Converter

2

Digital

register

5 V 3 V

°C

3 V 3 V

EEPROM

32.7 kHz

5 MHz

4

4

Micro-

processor

SD

40

4

Mux

2

5 V

Display

160

segments

IR Port

Switch and

push

buttons

VOLTS

AMPS

50 

0.5 

0.005 

COMM

Figure 3–1: Simple block diagram

3–2

1 M  100 k  10 k  1 k 

To B chip

To B chip

To B chip

TX1 and TX3 True RMS Digital Multimeter Service Manual

Performance Verification

Performance Verification

This section contains procedures to verify that the TX1 or TX3 True RMS
Digital Multimeters perform as warranted. If a meter fails any of these tests, it
needs calibrated and/or repaired.

The performance verification procedures confirm electrical characteristics under
the following conditions:

H The meter operates in an 18_ to 28_

C (64_ to 82_ F) ambient environment

with a relative humidity of less than 80%.

H The meter stabilizes in the stated ambient temperature for one hour.
H The meter warms up for 30 seconds.
H Allow the meter to settle to its final value before taking the measurement.
H The meter remains fully assembled and in the protective boot.

The performance verification consists of the tests listed in Table 4–1.

T able 4–1: Performance verification tests

AC Volts Test
AC Volts Frequency Test
DC Volts Test
Volts Peak Hold Test
AC DC Volts Test
AC+DC Volts and Frequency Test
Frequency Test
Duty Factor Test
 Test
Continuity Test
Diode Test
Capacitance T est
DC Current Test
AC Current Test

The performance verification procedure should be performed annually.

TX1 and TX3 True RMS Digital Multimeter Service Manual

4–1

Performance Verification

Á

Á

Á

Á

Á

Á

Test Equipment

The performance verification procedures use external traceable test equipment to
test warranted characteristics.

Alternative test equipment must meet or exceed the intended minimum
requirements listed in Table 4–2. If you substitute equipment, you may need to
modify the procedures.

NOTE. Before beginning the performance verification procedures, warm up the
test equipment according to the manufacturer’s recommendations.

T able 4–2: Test equipment

Description Minimum requirements Example product

Universal Calibration
System

ББББББ

ББББББ

Resolution & accuracy 4 times
greater than the meter display

БББББББ

reading.

БББББББ

AC and DC volts measurement

1

AC and DC current measurement

Wavetek 9100 with 9105 work
mat/lead set.

БББББББ

БББББББ

Fluke 5500A

Resistance measurement

1

Capacitance measurement
Sinewave generation

Squarewave generation

Capacitance Standard Optional

1

Choose 4-wire measurement setup if available.

4–2

TX1 and TX3 True RMS Digital Multimeter Service Manual

Set Up

Performance Verification

Prepare the meter for the performance verification with the following steps.

1. Allow the meter to stabilize at the ambient temperature for one hour before
testing.

2. Turn the meter on by rotating the function knob to any position other than
OFF.

3. Warm up the meter for 30 seconds.

NOTE. The auto power off time is adjustable using the setup menu. You can
disable the auto power off by pushing the HOLD button when turning the function
knob from the OFF position.

4. Connect the calibrator test leads to the meter inputs observing the color
coded leads and inputs (for example: yellow to A, red to V, and black to

COM).

FUSED 600V

15A/30 SECONDS

Yellow Black Red NOTE. Test lead colors from

CATIII
1000V

10A

calibration equipment may vary

WARNING. To avoid electric shock, avoid touching exposed connections.

5. Keep the meter in the low resolution 5,000-count mode unless instructed
otherwise.

6. Pages 4–11 through 4–21 contain test records for the TX1 and TX3 meters.
Each model has its own test record. Photocopy the test record pages for your
model to record your test results.

NOTE. If stability of the display reading causes questionable accuracy of a test,
set the meter to Average mode.

TX1 and TX3 True RMS Digital Multimeter Service Manual

4–3

Performance Verification

Verification Procedure

Implement the following tests to verify the performance of your TX1 or TX3
meter. The procedures are written with the intent that all tests are made from
beginning to end.

AC Volts Test

AC Volts Frequency Test

Perform the following steps to verify the AC voltage measurement accuracy.

1. Set the function knob to V.

2. Press softkey 1 to select AC (default setting).

3. Connect the calibrator outputs to the meter V and COM input connectors.

4. Set the calibrator to the first value in the AC volts test record.

5. Turn the calibrator output on.

6. Verify that the meter reads within the specified Display minimum and

maximum limits for each of the values in the AC volts test record.

7. Turn the calibrator output off.

Perform the following steps to verify the AC voltage frequency measurement
accuracy.

1. Set the function knob to V.

2. Press softkey 1 to select AC (default setting).

3. Connect the calibrator outputs to the meter V and COM input connectors.

4–4

DC Volts Test

4. Set the calibrator to the first value in the AC volts frequency test record.

5. Turn the calibrator output on.

6. Verify that the meter reads within the specified Display minimum and

maximum limits for each of the values in the AC volts frequency test record.

7. Turn the calibrator output off.

Perform the following steps to verify the DC volts measurement accuracy.

1. Set the function knob to V in the high resolution 50,000-count mode (using

the following sub-steps).

a. Set the function knob to OFF.
b. Press and hold the BLUE button while setting the function knob to V.

2. Press softkey 2 to select DC.

TX1 and TX3 True RMS Digital Multimeter Service Manual

Performance Verification

3. Set the calibrator to the first value in the DC volts test record.

4. Turn the calibrator output on.

5. Verify that the meter reads within the specified Display minimum and

maximum limits for each of the values in the DC volts test record.

6. Turn the calibrator output off.

Volts Peak Hold Test

AC DC Volts Test

Perform the following steps to verify the DC volts peak measurement accuracy.

1. Set the function knob to V.

2. Press softkey 2 to select DC.

3. Press the BLUE button and then the M/M/A button to select the 1 ms Peak

Hold function.

4. Connect the yellow, red, and black calibrator outputs to the meter A, V, and
COM input connectors.

5. Set the calibrator to the first value in the Volts peak hold test record.

6. Turn the calibrator output on.

7. Verify that the meter reads within the specified Display minimum and

maximum limits for each value in the Volts peak hold test record.

8. Turn the calibrator output off.

Perform the following steps to verify the AC DC voltage measurement accuracy.

1. Set the function knob to V.

2. Press softkey 3 repeatedly to select AC DC.

3. Set the calibrator to the first value in the AC DC volts test record.

4. Turn the calibrator output on.

5. Verify that the meter reads within the specified Display minimum and

maximum limits for each of the values in the AC DC volts test record.

6. Turn the calibrator output off.

TX1 and TX3 True RMS Digital Multimeter Service Manual

4–5

Performance Verification

AC+DC Volts and

Frequency Test

Frequency Test

Perform the following steps to verify the AC + DC voltage measurement
accuracy.

1. Set the function knob to V.

2. Press softkey 3 repeatedly to select AC + DC.

3. Set the calibrator to the first value in the AC+DC volts and frequency test

record.

4. Turn the calibrator output on.

5. Verify that the meter reads within the specified Display minimum and

maximum limits for each of the values in the AC+DC volts and frequency
test record.

6. Turn the calibrator output off.

Perform the following steps to verify the frequency measurement accuracy.

1. Set the function knob to Hz in the high resolution 50,000-count mode (using

the following sub-steps).

a. Set the function knob to OFF.
b. Press and hold the BLUE button while setting the function knob to Hz.

2. Verify that duty factor mode is off (using the following sub-steps).

a. If % DUTY is displayed in the upper display, press and hold the BLUE

button for two seconds.

b. Press softkey 4 until POL is displayed in the upper display.
c. Press softkey 1 until OFF is displayed in the main display.
d. Press the BLUE button to exit the setup mode.

3. Set the calibrator to the value in the Frequency test record.

4. Turn the calibrator output on.

5. Verify that the meter reads within the specified Display minimum and

maximum limits.

6. Turn the calibrator output off.

4–6

TX1 and TX3 True RMS Digital Multimeter Service Manual

Performance Verification

Duty Factor Test

Perform the following steps to verify the duty factor measurement accuracy.

1. Set the function knob to Hz.

2. Set the trigger edge polarity to positive (using the following sub-steps).
a. Press and hold the BLUE button for two seconds.
b. Press softkey 4 until POL is displayed in the upper display.
c. Press softkey 1 until POS is displayed in the main display.
d. Press the BLUE button to exit the setup mode.

3. Set the calibrator to the value in the Duty factor test record.

4. Turn the calibrator output on.

5. Verify that the meter reads within the specified Display minimum and

maximum limits for each value in the Duty factor test record.

6. Turn the calibrator output off.

7. Restore default to frequency (using the following sub-steps).
a. Press and hold the BLUE button for two seconds.

W Test

b. Press softkey 4 until POL is displayed in the upper display.
c. Press softkey 1 until OFF is displayed in the main display.
d. Press the BLUE button to exit the setup mode.

Perform the following steps to verify the resistance measurement accuracy in 
mode.

1. Set the function knob to /

2. Set the calibrator to the first value in the  test record.

3. Turn the calibrator output on.

4. Verify that the meter reads within the specified Display minimum and

maximum limits for each value in the  test record.

5. Turn the calibrator output off.

6. Set the function knob to OFF.

.

TX1 and TX3 True RMS Digital Multimeter Service Manual

4–7

Performance Verification

Continuity Test

Diode Test

Perform the following steps to verify continuity accuracy.

1. Set the function knob to /

2. Select

3. Set the calibrator to the first value in the Continuity test record.

4. Turn the calibrator output on.

5. Verify proper operation for each value in the Continuity test record.

6. Turn the calibrator output off.

7. Disconnect the calibrator from the meter.

8. Insert the meter test leads into the V and COM input connectors of the meter.

9. Short the test leads together and check for proper operation.

10. Disconnect the meter test leads and reconnect the V and COM input connec-

tors to the calibrator.

Perform the following steps to verify the diode test accuracy.

1. Set the function knob to /

with the softkeys.

.

.

Capacitance Test

2. Press softkey 3 to select the diode test mode.

3. Set the calibrator to the first value in the Diode test record.

4. Turn the calibrator output on.

5. Verify that the meter reads within the specified Display minimum and

maximum limits for each value in the Diode test record.

6. Turn the calibrator output off.

Perform the following steps to verify the capacitance measurement accuracy.

1. Set the function knob to

2. Disconnect the test leads from the meter input connectors.

3. Record the reading in the Capacitance test record.

.

4–8

TX1 and TX3 True RMS Digital Multimeter Service Manual

Performance Verification

4. Null the residual DMM and lead capacitance offset as described here
depending on the type of test equipment (using the following sub-steps).

a. Using Wavetek 9100 with 9105 work mat and lead set:

H Connect the black lead from the calibrator output to the meter COM

input.

H Press the meter  button.
H Connect the red lead from the calibrator output to the meter V input.

b. Using Fluke 5500A or Wavetek 9100 without the work mat and lead set:

H Connect the black lead from the calibrator output to the meter COM

input.

H Connect the red lead to the meter V input. (Do not connect the red

lead to the calibrator output yet.)

H Press the meter  button.

DC Current Test

H Connect the red lead to the calibrator output.

5. Set the calibrator to the first value in the Capacitance test record.

6. Turn the calibrator output on.

7. Verify that the meter reads within the specified Display minimum and

maximum limits for each value in the Capacitance test record.

8. Turn the calibrator output off.

Perform the following steps to verify the DC current measurement accuracy.

1. Set the function knob to A.

2. Set the calibrator to the first value in the DC current test record.

3. Turn the calibrator output on.

4. Verify that the meter reads within the specified Display minimum and

maximum limits for each value in the DC current test record.

5. Turn the calibrator output off.

TX1 and TX3 True RMS Digital Multimeter Service Manual

4–9

Performance Verification

AC Current Test

Perform the following steps to verify the AC current measurement accuracy.

1. Set the function knob to A.

2. Select AC with the softkeys.

3. Set the calibrator to the first value in the AC current test record.

4. Turn the calibrator output on.

5. Verify that the meter reads within the specified Display minimum and

maximum limits for each value in the AC current test record.

6. Turn the calibrator output off.

7. Disconnect the calibrator from the meter.

4–10

TX1 and TX3 True RMS Digital Multimeter Service Manual

TX1 and TX3 Performance Verification

Á

Á

Á

Á

Á

Á

Á

Á

Á

Á

Á

Á

Á

Á

TX1 Test Record

Serial number Procedure performed by Date

T able 4–3: TX1 test record results

Test input Tolerance Display minimum Test result Display maximum

AC volts test

0.0000 V

50.00 mV

460.0 mV

4.600 V

ÁÁÁÁ

46.00 V

460.0 V

1000 V

ÁÁÁÁ

1

1

60 Hz
60 Hz
20 kHz
40 Hz

ÁÁ

1 kHz
10 kHz
20 kHz
60 Hz
20 kHz
60 Hz
20 kHz
60 Hz

ÁÁ

10 kHz

–

± 2 counts
±(0.6% + 2 counts)
±(0.6% + 2 counts)
±(0.6% + 2 counts)
±(0.6% + 2 counts)

ББББББ

±(0.6% + 2 counts)
±(0.6% + 2 counts)
±(0.6% + 2 counts)
±(0.6% + 2 counts)
±(0.6% + 2 counts)
±(0.6% + 2 counts)
±(0.6% + 2 counts)
±(0.6% + 2 counts)

ББББББ

±(0.4% + 2 counts)

0.0 mV

49.5 mV

457.0 mV

457.0 mV

4.570 V

ÁÁÁÁ

4.570 V

4.570 V

4.570 V

45.70 V

45.70 V

457.0 V

457.0 V
992 V

ÁÁÁÁ

992 V

The upper display readout is ±1 counts corresponding to the input frequency.

0.2 mV

50.5 mV

463.0 mV

463.0 mV

БББББББÁÁÁÁÁ

4.630 V

4.630 V

4.630 V

4.630 V

46.30 V

46.30 V

463.0 V

463.0 V

БББББББÁÁÁÁÁ

1008 V
1008 V

AC volts frequency test (upper display readout)

100.0 mV

500.0 mV

ÁÁÁÁÁÁÁ

2

Manually select the 5 V range.

40 Hz
20 kHz

2

40 Hz
20 kHz

± 1 count
± 1 count
± 1 count
± 1 count

ББББББ

39.99 Hz

19.99 kHz

39.99 Hz

19.99 kHz

TX1 and TX3 True RMS Digital Multimeter Service Manual

ÁÁÁÁ

40.01 Hz

20.01 kHz

40.01 Hz

БББББББÁÁÁÁÁ

20.01 kHz

4–11

TX1 and TX3 Performance Verification

Á

Á

Á

Á

Á

Á

Á

Á

Á

Á

Á

Á

Á

Á

Á

Á

Á

Á

Á

Á

Á

Á

Á

Á

Á

Á

Á

Á

Á

Á

Á

Á

Á

Á

Á

T able 4–3: TX1 test record results (cont.)

Test input Display maximum Test resultDisplay minimumTolerance

DC volts test

0.0000 V

БББББББ

46.00 mV

460.0 mV
–460.0 mV

4.600 V

46.00 V

460.00 V

1000.0 V
–1000.0 V

БББББББ

3

Use the high resolution 50,000-count mode.

3

± 10 counts

БББББ

±(0.07% + 10 counts)
±(0.07% + 10 counts)
±(0.07% + 10 counts)
±(0.07% + 10 counts)
±(0.07% + 10 counts)
±(0.07% + 10 counts)
±(0.07% + 10 counts)
±(0.07% + 10 counts)

БББББ

–0.10 mV

ÁÁÁÁ

45.87 mV

459.58 mV
–460.42 mV

4.5958 V

45.958 V

459.58 V

998.3 V
–1001.7 V

ÁÁÁÁ

Volts peak hold test

3.2 V 4 ,
500 Hz square

ÁÁÁ

wave

ÁÁÁ

3.2 V 4 ,
500 Hz square

ÁÁÁ

wave

4

Set input voltage to 6.4 V square wave if using a Fluke 5500A calibrator.

MAX

ÁÁÁ

ÁÁÁ

MIN

ÁÁÁ

± 30 counts

БББББ

БББББ

± 30 counts

БББББ

3.167 V

ÁÁÁÁ

ÁÁÁÁ

–3.233 V

ÁÁÁÁ

БББББББÁÁÁÁÁ

0.10 mV

46.13 mV

460.42 mV
–459.58 mV

4.6042 V

46.042 V

460.42 V

1001.7 V

БББББББÁÁÁÁÁ

–998.3 V

3.233 V

БББББББ

БББББББ

ÁÁÁÁ

ÁÁÁÁ

–3.167 V

БББББББÁÁÁÁÁ

AC DC volts test

32 mV

ÁÁÁ

460 mV

5

The voltage is shown in the upper display readout.

DC

ÁÁÁ

40 Hz

±(0.7% + 3 counts)

БББББ

±(0.7% + 3 counts)

AC+DC volts & frequency test

–1.000 V

1.000 V

1.000 V

ÁÁÁ

500.0 mV

6

Manually select the 5 V range.

7

The frequency is shown in the upper display readout.

DC
DC
60 Hz

6

ÁÁÁ

20 kHz ± 1 count 19.99 kHz

±(0.7% + 3 counts)
±(0.7% + 3 counts)
±(0.7% + 3 counts)

БББББ

4–12

31.8 mV

456.5 mV

0.990 V

0.990 V

0.990 V

5

ÁÁÁÁ

5

ÁÁÁÁ

7

БББББББÁÁÁÁÁ

32.2 mV

463.5 mV

1.010 V

1.010 V

БББББББÁÁÁÁÁ

1.010 V

20.01 kHz

7

TX1 and TX3 True RMS Digital Multimeter Service Manual

T able 4–3: TX1 test record results (cont.)

Á

Á

Á

Á

Á

Á

Á

Á

Á

Á

Á

Á

Á

Á

Á

Á

Á

Á

Á

Á

Á

Test input Display maximum Test resultDisplay minimumTolerance

TX1 and TX3 Performance Verification

Frequency test

990.00 kHz

ÁÁÁÁ

8

Use the high resolution 50,000-count mode.

9

The Wavetek 9100 (see Test Equipment table) is the recommended test equipment to accurately perform this test.

Duty factor test

10.0%

ÁÁÁÁ

ÁÁÁÁ

10

The duty factor is shown in the upper display readout.

8,9

2.82 V

ÁÁ

10

5 V

p-p

ÁÁ

100 Hz, 10%
DF pulse

ÁÁ

p-p

,

±(0.002% + 1 count)

ББББББ

±(0.1% + 0.05% per

ББББББ

kHz + 1 count)

ББББББ

989.97 kHz

ÁÁÁÁ

9.9 %

ÁÁÁÁ

ÁÁÁÁ

БББББББÁÁÁÁÁ

БББББББ

БББББББ

W test

11

0.00 W

40.00 W

400.0 W

4.000 kW

БББББББ

12
11

40.00 kW

400.0 kW

± 4 counts
±(0.1% + 10 counts)
±(0.1% + 4 counts)
±(0.1% + 2 counts)

ББББББ

±(0.1% + 2 counts)
±(0.1% + 2 counts)

0.0 W

39.86 W

399.2 W

3.994 kW

ÁÁÁÁ

39.94 kW

399.4 kW

БББББББÁÁÁÁÁ

990.03 kHz

10.1 %

ÁÁÁÁ

ÁÁÁÁ

0.4 W

40.14 W

400.8 W

4.006 kW

40.06 kW

400.6 kW

4.000 MW

40.00 MW

11

Use Delta mode.

12

Select 50 ohm range using soft key 4 for this range only

±(0.4% + 4 counts)
±(1% + 4 counts)

3.980 MW

39.56 MW

Continuity test

50 W
150 W

Beeper sounds
Beeper does not sound

–
–

Multimeter leads shorted Beeper sounds – –

Diode test

0.5 V

± 1%

0.495 V

TX1 and TX3 True RMS Digital Multimeter Service Manual

4.020 MW

40.44 MW

–
–

0.505 V

4–13

TX1 and TX3 Performance Verification

Á

Á

Á

Á

Á

Á

Á

Á

T able 4–3: TX1 test record results (cont.)

Test input Display maximum Test resultDisplay minimumTolerance

Capacitance test

4.000 nF

БББББББ

40.00 nF

400.0 nF

4.000 F

40.00 F

400.00 F

4.000 mF

40.00 mF

13

Variations in test equipment can cause erroneous readings. Use a fixed value capacitance standard if instability occurs.

14

Set the DMM to Delta mode. Delta mode removes stray capacitance for low capacitance measurements.

15

Wavetek 9100 only.

DC current test

0.0 A

460.0 A
–460.0 A

БББББББ

4.600 mA

13,14

±(1% + 5 counts)

БББББ

±(1% + 3 counts)
±(1% + 3 counts)
±(1% + 3 counts)
±(3% + 3 counts)
±(3% + 3 counts)

15
15

±(3% + 3 counts)
±(3% + 3 counts)

± 4 counts
±(0.2% + 4 counts)
±(0.2% + 4 counts)

БББББ

±(0.2% + 2 counts)

3.955 nF

ÁÁÁÁ

39.57 nF

395.7 nF

3.957 F

38.77 F

387.7 F

3.877 mF

38.77 mF

–0.4 A

458.7 A
–461.3 A

ÁÁÁÁ

4.589 mA

БББББББÁÁÁÁÁ

4.045 nF

40.43 nF

404.3 nF

4.043 F

41.23 F

412.3 F

4.123 mF

41.23 mF

0.4 A

461.3 A

БББББББÁÁÁÁÁ

–458.7 A

4.61 1 mA

46.00 mA

0.4600 A

4.600 A

10.00 A

4–14

±(0.2% + 2 counts)
±(0.2% + 2 counts)
±(0.4% + 2 counts)
±(0.8% + 2 counts)

45.89 mA

458.9 mA

4.580 A

9.90 A

46.1 1 mA

461.1 mA

4.620 A

10.10 A

TX1 and TX3 True RMS Digital Multimeter Service Manual

T able 4–3: TX1 test record results (cont.)

Á

Á

Á

Á

Á

Á

Á

Á

Á

Test input Display maximum Test resultDisplay minimumTolerance

TX1 and TX3 Performance Verification

AC current test

0.0 A

ÁÁÁÁ

460.0 A

4.600 mA

46.00 mA

460.00 mA

ÁÁÁÁ

16

ÁÁÁББББББ

60 Hz
5 kHz
60 Hz
5 kHz
60 Hz
3 kHz
5 kHz
60 Hz

ÁÁ

3 kHz

±2 counts
±(0.6% + 2 counts)
±(2% + 2 counts)
±(0.6% + 2 counts)
±(2% + 2 counts)
±(0.6% + 2 counts)
±(1.0% + 2 counts)
±(2% + 2 counts)
±(0.6% + 2 counts)

ББББББ

±(1.0% + 2 counts)

0.0 A

ÁÁÁÁ

457.0 A

450.6 A

4.570 mA

4.506 mA

45.70 mA

45.52 mA

45.06 mA

457.0 mA

ÁÁÁÁ

455.2 mA

БББББББÁÁÁÁÁ

0.2 A

463.0 A

469.4 A

4.630 mA

4.694 mA

46.30 mA

46.48 mA

46.94 mA

БББББББÁÁÁÁÁ

463.0 mA

464.8 mA

5 kHz ±(2% + 2 counts) 450.6 mA 469.4 mA

4.600 A 60 Hz ±(0.6% + 2 counts) 4.570 A 4.630 A
5 kHz ±(2% + 2 counts) 4.506 A 4.694 A

10.00 A

60 Hz

±(0.6% + 2 counts)

9.92 A

10.08 A

5 kHz ±(2% + 2 counts) 9.78 A 10.22 A

16

The upper display readout is ±1 count corresponding to the input frequency.

TX1 and TX3 True RMS Digital Multimeter Service Manual

4–15

TX1 and TX3 Performance Verification

4–16

TX1 and TX3 True RMS Digital Multimeter Service Manual

TX1 and TX3 Performance Verification

Á

Á

Á

Á

Á

Á

Á

Á

Á

Á

Á

Á

Á

Á

TX3 Test Record

Serial number Procedure performed by Date

T able 4–4: TX3 test record results

Test input Tolerance Display minimum Test result Display maximum

AC volts test

0.0000 V

50.00 mV

460.0 mV

4.600 V

ÁÁÁÁ

46.000 V

460.00 V

1000.0 V

ÁÁÁÁ

1

1

60 Hz
60 Hz
20 kHz
40 Hz

ÁÁ

1 kHz
10 kHz
20 kHz
60 Hz
20 kHz
60 Hz
20 kHz
60 Hz

ÁÁ

10 kHz

–

± 2 counts
±(0.4% + 2 counts)
±(0.4% + 2 counts)
±(0.4% + 2 counts)
±(0.4% + 2 counts)

ББББББ

±(0.4% + 2 counts)
±(0.4% + 2 counts)
±(0.4% + 2 counts)
±(0.4% + 2 counts)
±(0.4% + 2 counts)
±(0.4% + 2 counts)
±(0.4% + 2 counts)
±(0.4% + 2 counts)

ББББББ

±(0.4% + 2 counts)

0.0 mV

49.6 mV

458.0 mV

458.0 mV

4.580 V

ÁÁÁÁ

4.580 V

4.580 V

4.580 V

45.80 V

45.80 V

458.0 V

458.0 V
994 V

ÁÁÁÁ

994 V

The upper display readout is ±1 count corresponding to the input frequency.

0.2 mV

50.4 mV

462.0 mV

462.0 mV

БББББББÁÁÁÁÁ

4.620 V

4.620 V

4.620 V

4.620 V

46.20 V

46.20 V

462.0 V

462.0 V

БББББББÁÁÁÁÁ

1006 V
1006 V

AC volts frequency test (upper display readout)

100.0 mV

500.0 mV

ÁÁÁÁÁÁÁ

2

2

Manually select the 5 V range.

40 Hz
20 kHz
40 Hz
20 kHz

± 1 count
± 1 count
± 1 count
± 1 count

ББББББ

39.99 Hz

19.99 kHz

39.99 Hz

19.99 kHz

TX1 and TX3 True RMS Digital Multimeter Service Manual

ÁÁÁÁ

40.01 Hz

20.01 kHz

40.01 Hz

БББББББÁÁÁÁÁ

20.01 kHz

4–17

TX1 and TX3 Performance Verification

Á

Á

Á

Á

Á

Á

Á

Á

Á

Á

Á

Á

Á

Á

Á

Á

Á

Á

T able 4–4: TX3 test record results (cont.)

Test input Display maximum Test resultDisplay minimumTolerance

DC volts test

0.0000 V

БББББББ

46.00 mV

460.00 mV
–460.00 mV

4.6000 V

46.000 V

460.00 V

1000.0 V
–1000.0 V

БББББББ

3

3

± 10 counts

БББББ

±(0.05% + 10 counts)
±(0.05% + 10 counts)
±(0.05% + 10 counts)
±(0.05% + 10 counts)
±(0.05% + 10 counts)
±(0.05% + 10 counts)
±(0.05% + 10 counts)
±(0.05% + 10 counts)

БББББ

Use the high resolution 50,000-count mode.

–0.10 mV

ÁÁÁÁ

45.88 mV

459.67 mV
–460.33 mV

4.5967 V

45.967 V

459.67 V

0998.5 V
–1001.5 V

ÁÁÁÁ

Volts peak hold test

3.2 V 4, 500 Hz
square wave

ÁÁÁ

3.2 V 4, 500 Hz
square wave

ÁÁÁ

4

Set input voltage to 6.4 V square wave if using a Fluke 5500A calibrator.

MAX

ÁÁÁ

MIN

ÁÁÁ

± 30 counts

БББББ

± 30 counts

БББББ

3.167 V

ÁÁÁÁ

–3.233 V

ÁÁÁÁ

БББББББÁÁÁÁÁ

0.10 mV

46.12 mV

460.33 mV
–459.67 mV

4.6033 V

46.033 V

460.33 V

1001.5 V

БББББББÁÁÁÁÁ

–0998.5 V

3.233 V

БББББББÁÁÁÁÁ

–3.167 V

БББББББÁÁÁÁÁ

AC DC volts test

32 mV
460 mV

5

The voltage is shown in the upper display readout.

DC
40 Hz

±(0.5% + 3 counts)
±(0.5% + 3 counts)

AC+DC volts and frequency test

–1.000 V

1.000 V

1.000 V

500.0 mV

6

Manually select the 5 V range.

7

The frequency is shown in the upper display readout.

DC
DC
60 Hz

6

20 kHz ± 1 count 19.99 kHz

±(0.7% + 3 counts)
±(0.7% + 3 counts)
±(0.7% + 3 counts)

4–18

31.8 mV

457.4 mV

0.990 V

0.990 V

0.990 V

5

5

32.2 mV

462.6 mV

1.010 V

1.010 V

1.010 V

7

20.01 kHz

7

TX1 and TX3 True RMS Digital Multimeter Service Manual

T able 4–4: TX3 test record results (cont.)

Á

Á

Á

Á

Á

Á

Á

Á

Á

Á

Á

Á

Á

Á

Á

Á

Á

Á

Á

Á

Á

Á

Á

Á

Á

Test input Display maximum Test resultDisplay minimumTolerance

TX1 and TX3 Performance Verification

Frequency test

990.00 kHz

ÁÁÁÁ

8

Use the high resolution 50,000-count mode.

9

The Wavetek 9100 (see Test Equipment table) is the recommended test equipment to accurately perform this test.

Duty factor test

10.0%

ÁÁÁÁ

ÁÁÁÁ

8,9

2.82 V

10

5 V
100 Hz,
10% DF

p-p

ÁÁ

,

p-p

ÁÁ

ÁÁ

±(0.002% + 1 count)

ББББББ

±(0.1% + 0.05% per

ББББББ

kHz + 1 count)

ББББББ

989.97 kHz

ÁÁÁÁ

9.9 %

ÁÁÁÁ

ÁÁÁÁ

БББББББÁÁÁÁÁ

БББББББ

БББББББ

pulse

10

The duty factor is shown in the upper display readout.

W test

11

0.00 W

40.00 W

400.0 W

4.000 kW

40.00 kW

12
11

± 4 counts
±(0.1% + 10 counts)
±(0.1% + 4 counts)
±(0.1% + 2 counts)
±(0.1% + 2 counts)

0.0 W

39.86 W

399.2 W

3.994 kW

39.94 kW

990.03 kHz

10.1 %

ÁÁÁÁ

ÁÁÁÁ

0.4 W

40.14 W

400.8 W

4.006 kW

40.06 kW

400.0 kW

БББББББ

4.000 MW

40.00 MW

11

Use Delta mode.

12

Select 50 ohm range using soft key 4 for this range only

±(0.1% + 2 counts)

ББББББ

±(0.4% + 4 counts)
±(1% + 4 counts)

399.4 kW

ÁÁÁÁ

3.980 MW

39.56 MW

БББББББÁÁÁÁÁ

Continuity test

50 W

БББББББ

150 W

Beeper sounds

ББББББ

Beeper does not sound

–

ÁÁÁÁ

–

БББББББÁÁÁÁÁ

Multimeter leads shorted Beeper sounds – –

Diode test

0.5 V

TX1 and TX3 True RMS Digital Multimeter Service Manual

± 1%

0.495 V

400.6 kW

4.020 MW

40.44 MW

–
–

0.505 V

4–19

TX1 and TX3 Performance Verification

Á

Á

Á

Á

Á

Á

Á

Á

T able 4–4: TX3 test record results (cont.)

Test input Display maximum Test resultDisplay minimumTolerance

Capacitance test

4.000 nF

БББББББ

40.00 nF

400.0 nF

4.000 F

40.00 F

400.00 F

4.000 mF

40.00 mF

13

Variations in test equipment can cause erroneous readings. Use a fixed value capacitance standard if instability occurs.

14

Set the DMM to Delta mode. Delta mode removes stray capacitance for low capacitance measurements.

15

Wavetek 9100 only.

13,14

±(1% + 5 counts)

БББББ

±(1% + 3 counts)
±(1% + 3 counts)
±(1% + 3 counts)
±(3% + 3 counts)
±(3% + 3 counts)

15
15

±(3% + 3 counts)
±(3% + 3 counts)

3.955 nF

ÁÁÁÁ

39.57 nF

395.7 nF

3.957 F

38.77 F

387.7 F

3.877 mF

38.77 mF

БББББББÁÁÁÁÁ

4.045 nF

40.43 nF

404.3 nF

4.043 F

41.23 F

412.3 F

4.123 mF

41.23 mF

DC current test

0.0 A

460.0 A
–460.0 A

БББББББ

4.600 mA

± 4 counts
±(0.2% + 4 counts)
±(0.2% + 4 counts)

БББББ

±(0.2% + 2 counts)

–0.4 A

458.7 A
–461.3 A

ÁÁÁÁ

4.589 mA

0.4 A

461.3 A

БББББББÁÁÁÁÁ

–458.7 A

4.61 1 mA

46.00 mA

460.00 mA

4.600 A

10.00 A

4–20

±(0.2% + 2 counts)
±(0.2% + 2 counts)
±(0.4% + 2 counts)
±(0.8% + 2 counts)

45.89 mA

458.9 mA

4.580 A

9.90 A

46.1 1 mA

461.1 mA

4.620 A

10.10 A

TX1 and TX3 True RMS Digital Multimeter Service Manual

T able 4–4: TX3 test record results (cont.)

Á

Á

Á

Á

Á

Á

Á

Á

Á

Á

Á

Á

Á

Á

Test input Display maximum Test resultDisplay minimumTolerance

TX1 and TX3 Performance Verification

AC current test

0.0 A

ÁÁÁÁ

460.0 A

4.600 mA

46.00 mA

460.0 mA

ÁÁÁÁ

16

ÁÁÁББББББ

60 Hz
5 kHz
60 Hz
5 kHz
60 Hz
3 kHz
5 kHz
60 Hz

ÁÁ

3 kHz

± 2 counts
±(0.6% + 2 counts)
±(2% + 2 counts)
±(0.6% + 2 counts)
±(2% + 2 counts)
±(0.6% + 2 counts)
±(1.0% + 2 counts)
±(2.0% + 2 counts)
±(0.6% + 2 counts)

ББББББ

±(1.0% + 2 counts)

0.0 A

ÁÁÁÁ

457.0 A

450.6 A

4.570 mA

4.506 mA

45.70 mA

45.52 mA

45.06 mA

457.0 mA

ÁÁÁÁ

455.2 mA

5 kHz ±(2% + 2 counts) 450.6 mA 469.4 mA

4.600 A

60 Hz

±(0.6% + 2 counts)

4.570 A

5 kHz ±(2% + 2 counts) 4.506 A 4.694 A

10.00 A

ÁÁÁÁ

60 Hz

ÁÁ

±(0.6% + 2 counts)

ББББББ

9.92 A

ÁÁÁÁ

5 kHz ±(2% + 2 counts) 9.78 A 10.22 A

16

The upper display readout is ±1 count corresponding to the input frequency.

БББББББÁÁÁÁÁ

0.2 A

463.0 A

469.4 A

4.630 mA

4.694 mA

46.30 mA

46.48 mA

46.94 mA

БББББББÁÁÁÁÁ

463.0 mA

464.8 mA

4.630 A

10.08 A

БББББББÁÁÁÁÁ

TX1 and TX3 True RMS Digital Multimeter Service Manual

4–21

TX1 and TX3 Performance Verification

4–22

TX1 and TX3 True RMS Digital Multimeter Service Manual

Adjustment Procedure

Adjustment Procedure

Adjustment of the TX1 and TX3 meters should only be performed if the
Performance Verification procedure indicates that adjustment is necessary.

There are no internal adjustments. Contact Tektronix for adjustment information.
See page x for methods for contacting Tektronix.

TX1 and TX3 True RMS Digital Multimeter Service Manual

5–1

Adjustment Procedure

5–2

TX1 and TX3 True RMS Digital Multimeter Service Manual

Options

Options

There are no options available for the TX1 and TX3 meters. For a list of
available accessories, refer to the Replaceable Parts chapter.

TX1 and TX3 True RMS Digital Multimeter Service Manual

6–1

Options

6–2

TX1 and TX3 True RMS Digital Multimeter Service Manual

Maintenance

Maintenance

This chapter contains the information needed to do periodic and corrective
maintenance on the TX Series True RMS Digital Multimeters. The following
sections are included:

H Preparation refers you to important information contained elsewhere in this

manual.

H Preventing ESD provides general information on preventing damage to

internal modules when doing maintenance.

H Cleaning provides procedures for cleaning the exterior of the meter.
H Drying Procedure provides instructions to dry the meter should it be exposed

to water.

H Disassembly/Assembly Procedures provide procedures for the disassembly

and reassembly of the meter.

H Troubleshooting provides information to help isolate failed modules.
H Repackaging Instructions provides packaging information for shipment or

storage.

Related Maintenance Procedures

The following sections contain information and procedures related to mainte­nance.

H Chapter 2, Operating Information, covers instructions useful when operating

the meter in order to troubleshoot it.

H Chapter 3, Theory of Operation, contains a circuit description at the block

level.

H Chapter 4, Performance Verification, contains procedures that may be useful

in isolating problems by testing performance.

H Chapter 5, Adjustment Procedure, addresses after repair adjustment and the

interval between periodic adjustments.

H Chapter 8, Parts List, lists all replaceable parts with part numbers.

TX1 and TX3 True RMS Digital Multimeter Service Manual

7–1

Maintenance

Preparation

Only qualified service personnel should perform service procedures. Read the
Service Safety Summary, the General Safety Summary, and the ESD information
below before performing any service procedures.

CAUTION. Static discharge can damage any semiconductor component in this
meter.

Preventing ESD

When performing any service which requires internal access to the meter, adhere
to the following precautions to avoid damaging internal components due to
electrostatic discharge (ESD).

1. Minimize handling of static-sensitive modules.

2. Transport and store static-sensitive modules in their static protected

containers or on a metal rail. Label any package that contains static-sensitive
modules.

3. Discharge the static voltage from your body by wearing a grounded antistatic

wrist strap while handling these modules. Service static-sensitive devices
only at a static-free work station.

4. Nothing capable of generating or holding a static charge should be allowed

on the work station surface.

5. Handle circuit boards by the edges when possible.

6. Do not slide boards or components over any surface.

7. Avoid handling in areas that have a floor or work-surface covering capable of

generating a static charge.

7–2

Susceptibility to ESD. Table 7–1 lists the relative susceptibility of various classes

of semiconductors. Static voltages of 1 kV to 30 kV are common in unprotected
environments.

TX1 and TX3 True RMS Digital Multimeter Service Manual

T able 7–1: Relative susceptibility to static-discharge damage

Relative susceptibility

1

Semiconductor classes

MOS or CMOS microcircuits or discrete circuits, or linear
microcircuits with MOS inputs (most sensitive)

ECL 2
Schottky signal diodes 3
Schottky TTL 4
High-frequency bipolar transistors 5
JFET 6
Linear microcircuits 7
Low-power Schottky TTL 8
TTL (least sensitive) 9

1

Voltage equivalent for levels (voltage discharged from a 100pF capacitor through
resistance of 100 ohms):

1 = 100 to 500 V 6 = 600 to 800 V
2 = 200 to 500 V 7 = 400 to 1000 V (est.)
3 = 250 V 8 = 900 V
4 = 500 V 9 = 1200 V
5 = 400 to 600 V

levels

1

Maintenance

Inspection and Cleaning

General Care

This section describes how to inspect for dirt and damage and how to clean the
exterior. Inspection and cleaning are done as preventive maintenance. Preventive
maintenance, when done regularly, may prevent malfunction and enhance its
reliability.

Preventive maintenance consists of periodic inspection and cleaning and using
general care when operating.

How often to do maintenance depends on the severity of the environment in
which the meter is used. A proper time to perform preventive maintenance is just
before adjustment.

The boot helps protect the meter from damage due to bumps and drops. It’s
recommended to leave the boot on during normal use of the meter. The case
keeps out dust and moisture and should be in place when ever operating the
meter.

Protect the meter from adverse weather conditions.
Do not expose the LCD display to direct sunlight for long periods of time.

TX1 and TX3 True RMS Digital Multimeter Service Manual

7–3

Maintenance

Inspection and Cleaning

Procedures

Internal Cleaning

Procedures

Inspect and clean the meter as often as operating conditions require.
Clean the exterior of the meter by removing dust with a lint-free cloth. Use care

to avoid scratching the clear plastic display filter.
For further cleaning, use a soft cloth or paper towel dampened with water. You

can use an alcohol-free glass cleaner for more efficient cleaning.

CAUTION. To avoid damage to the surface of the meter, do not use abrasive or
chemical cleaning agents.

WARNING. The meter is not protected from exposure to water. Exposing the meter
to water can create a shock hazard.

In rare cases, the interior of the meter may require cleaning.
Clean the interior by using the disassembly procedures in this chapter. Use a soft

lint-free cloth dampened with water. If more efficient cleaning of the LCD
contacts and function knob contacts on the circuit board is required, a 75%
isopropyl alcohol solution can be used.

Drying Procedure

Lubrication

If the meter is exposed to water, open the case and allow the meter to fully dry.
To open the meter, use the procedure in the Disassembly/Assembly Procedur es
section. Before reassembling the meter, check that all seams, battery compart­ment, and input connectors are dry.

There is no periodic lubrication required.

7–4

TX1 and TX3 True RMS Digital Multimeter Service Manual

Disassembly and Assembly Procedures

The following procedures are ordered in the logical sequence of disassembly.
You will usually need to start from the beginning and continue until you reach
the objective. Reassemble the meter by following the procedures in the reverse
order. Use the exploded view of the meter on page 8–5 as an overall guide in
both the disassembly and assembly of the meter.

T able 7–2: List of tools

Flat blade screwdriver
#10 Torx tip screwdriver

CAUTION. The internal components and contacts are adversely affected by skin
oil. Take precautions to avoid direct skin contact when performing these
procedures. Refer to Internal Cleaning Procedures on page 7–4 if you need to
clean components before reassembling the meter.

Maintenance

TX1 and TX3 True RMS Digital Multimeter Service Manual

7–5

Maintenance

Meter Case

Use the following procedure to gain access to the service replaceable fuse and all
replaceable modules. You must first remove the protective boot to open the meter
case. You will need a small flat blade screwdriver and a #10 torx tip screwdriver.

Opening.

1. Remove the battery cover. Remove the batteries and the two screws (one on

each side of the batteries).

2. Carefully insert a screw driver between the gasket and meter case and gently

lift and remove the gasket.

Screws (2)

Batteries

Gasket

Figure 7–1: Opening and closing the case

Battery cover

Fuse F1

7–6

TX1 and TX3 True RMS Digital Multimeter Service Manual

Maintenance

CAUTION. Opening the case allows a “pogo stick” type electrical contact pin to
fall out of its holder. Use care not to lose the contact or allow it to remain loose
in the instrument when reinstalling the bottom case half. See Figure 7–2 for the
location of this pin.

3. From the end near the batteries, carefully lift the case half up until the

opposite end snaps loose.

WARNING. Installing improper fuses can cause injury and product damage.

The internal fuse (F1) is accessible at this time. If replacing the fuse, see the

Replaceable Parts chapter for the proper replacement fuse.

Closing.

1. Check that all seals and contacts are in place.

Internal Assembly

2. Slip the end of the bottom case half (opposite end from the batteries) into the

top case half.

3. Pivot the bottom case half down and press firmly together.

4. Secure the case halves together with the two screws.

5. Install the battery cover gasket. Install the gasket so that its shape matches

the shape of the meter case and the bumps on the gasket point towards the
batteries.

NOTE. It’s important to install the battery cover gasket correctly to retain the
stated environmental characteristics.

6. Insert batteries and slide the battery cover on.

The internal assembly is comprised of the circuit board and display assembly.
The internal assembly must be removed from the case half as a unit.

Removal.

1. Disconnect the battery cable from the circuit board. Do not pull on the wires.

2. Remove the two screws securing the internal assembly to the top case.

3. From the front of the top case half, push in on the input connectors to loosen

the assembly from the case half.

TX1 and TX3 True RMS Digital Multimeter Service Manual

7–7

Maintenance

4. Lift the entire assembly straight up out of the case half.

NOTE. The easiest method to lift the assembly out is to grasp the large component
on the circuit board and lift straight up.

Battery connector

Top case

Remove screws (2)

Pogo stick pin

Battery cable

Use component to lift internal

assembly straight up

Push up on the

input connectors.

7–8

Figure 7–2: Internal assembly removal and installation

Installation.

1. Hold the entire assembly directly above the top case half.

2. Lower the assembly down into the case half and seat the assembly firmly

into the case half.

3. Reinstall the two screws to secure the internal assembly to the top case half.

4. Connect the battery cable to the circuit board.

TX1 and TX3 True RMS Digital Multimeter Service Manual

Maintenance

Battery Holder

The battery holder slides off the top case half after disengaging the two securing
tabs. The internal assembly must be removed first to allow room for the securing
tabs to disengage. Refer to Figure 7–3.

Removal.

1. Remove the internal assembly (see page 7–7).

2. Disconnect the battery cable from the circuit board.

3. Locate the two tabs securing the battery holder to the top case half.

Battery holder

Top case

Figure 7–3: Battery holder removal and installation

4. Disengage the tabs and slide the battery holder off the top case half.

TX1 and TX3 True RMS Digital Multimeter Service Manual

Slot

Tab

7–9

Maintenance

Installation.

1. Slide the battery holder down onto the top case half ensuring the two slides

on the battery holder engage the matching slots in the top case half.

2. Slide the holder down until the two securing tabs lock into place.

LCD Assembly

The LCD assembly can be accessed after the internal assembly is removed from
the top case half.

NOTE. It is not necessary to remove the circuit board to remove the LCD
assembly.

Removal.

1. Remove the internal assembly (see page 7–7).

2. Using a small flat blade screwdriver, disengage the four tabs (at the top end

of the assembly) securing the display bezel.

Display bezel

7–10

Disengage tabs (4)

Figure 7–4: LCD bezel removal and installation

3. Lift the top end of the display bezel up until the four tabs (at the bottom end

of the display assembly) disengage.

4. The LCD display and contacts can be lifted out of the display housing.

TX1 and TX3 True RMS Digital Multimeter Service Manual

LCD contact

strips

Maintenance

LCD display

Small bump

Housing cutout

Figure 7–5: LCD removal and installation

Installation.

1. Install the two LCD contact strips into the display housing.

2. Place the LCD into the display housing.

NOTE. Place the LCD into the assembly so that the side with the small bump is
aligned with the cutout in the housing and the contacts are facing the contact
strips.

3. Press the bottom of the LCD bezel down until the bottom four tabs snap into

place.

4. Place the top of the LCD bezel over the display and push down to snap the

top four tabs into place.

NOTE. Before proceeding, check to make sure all eight tabs securing the LCD
bezel are seated properly. The display may have moved if all the tabs do not
engage. Remove the bezel, check that the display is seated properly and try
again.

TX1 and TX3 True RMS Digital Multimeter Service Manual

7–11

Maintenance

Circuit Board

The circuit board can be removed from the internal assembly after the internal
assembly is removed from the top case half.

NOTE. It is not necessary to remove the circuit board to remove the LCD
assembly.

Removal.

1. Remove the internal assembly (see page 7–7) and LCD assembly (see page

7–10).

2. Disengage the two tabs protruding through the middle of the circuit board.

3. Disengage the four tabs at the top end of the circuit board (the end without

the input connectors).

Disengage tabs (2)

Disengage tabs (4)

Figure 7–6: Circuit board tabs

Internal assembly

7–12

TX1 and TX3 True RMS Digital Multimeter Service Manual

4. Lift the circuit board off of the assembly

Circuit board

Maintenance

EMI clip

Contact spring

LCD contact strips

Figure 7–7: Circuit board removal and installation

Installation.

1. Ensure that the contacts listed are in place before installing the circuit board.

H Contact spring
H LCD contact strips (two)
H EMI clip

2. Lower the circuit board straight down onto the assembly ensuring that all six

securing tabs lock into place.

NOTE. Installing a new circuit board requires that the meter be re-calibrated.
Refer to the Adjustment chapter for calibration.

TX1 and TX3 True RMS Digital Multimeter Service Manual

7–13

Maintenance

Light Diffuser

The light diffuser can only be removed after removing the circuit board and LCD
assembly. Refer to Figure 7–8.

Removal.

1. Remove the internal assembly (see page 7–7), LCD assembly (see page

7–10), and circuit board (see page 7–12).

1. Grasp the housing and flex the corner, causing the light diffuser corner to pop

up.

2. Flip the diffuser up and slide it out through the slot in the housing.

Diffuser will

pop up

7–14

Rotate and

slide down

Figure 7–8: Light diffuser removal and installation

TX1 and TX3 True RMS Digital Multimeter Service Manual

Maintenance

Installation.

1. From the back of the housing, slide the light diffuser up through the slot and

flip it down into the LCD compartment.

2. Press the diffuser down to ensure it is seated into the LCD compartment.

Switch Keypad

Function Knob

The internal assembly must be removed to gain access to the switch keypad. The
keypad is easily lifted out or placed in the top case half. Refer to Figure 7–10.

NOTE. Avoid touching the keypad contacts on either the keypad or the circuit
board.

The internal assembly must be removed to gain access to the function knob
assembly. Refer to Figures 7–9 and 7–10.

Removal.

1. Hold the top case half in the palm of your hand (or support both ends of the

top case half, allowing the function knob room to be removed).

2. Insert a narrow object (such as a small screwdriver) into the hole in the back

side of the function knob and press down until the knob assembly snaps
apart.

CAUTION. Take extreme care not to damage the contacts on the clicker. This will
need to be replaced if the contacts are bent.

TX1 and TX3 True RMS Digital Multimeter Service Manual

7–15

Maintenance

Screwdriver

Top case

Knob
assembly

Supports

Figure 7–9: Function knob removal

Installation.

1. Place the function knob into the top case half. Place the knob so that it is able

to rotate to all functions. Ensure that the o-ring is in place on the function
knob.

2. From inside the case half, place the clicker onto the function knob (use the

key for alignment) and press down until it snaps into place.

7–16

TX1 and TX3 True RMS Digital Multimeter Service Manual

Switch keypad

Top case

Maintenance

Alignment key

Clicker

O-ring

Function knob

Figure 7–10: Function knob and switch keypad installation

TX1 and TX3 True RMS Digital Multimeter Service Manual

7–17

Maintenance

Troubleshooting

This section contains a troubleshooting tree divided into three sections to help
isolate problems to the most probable cause.

In most cases the easiest method to use the trees is to begin with the first tree at
“Start Here.”

WARNING. Before doing this or any other procedure in this manual, read the

General Safety Summary and Service Safety Summary found at the beginning of
this manual. Also, to prevent possible injury to service personnel or damage to
electrical components, read Preventing ESD and Inspection and Cleaning in this
chapter.

Some checks require partial disassembly of the meter. Read the Safety Summa­ries at the beginning of this manual and then see the section Disassembly and
Assembly Procedures in this chapter for instructions.

Adjustment After Repair

NOTE. The battery cover must be in place for the meter to operate.

Refer to the chapter Adjustment Procedure if you replace the circuit board.

7–18

TX1 and TX3 True RMS Digital Multimeter Service Manual