Omega Products TX91 Installation Manual

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TX91

Thermocouple Two-Wire
Temperature Transmitter

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Servicing

North America:

U.S.A.:

ISO 9001 Certified

OMEGA Engineering, Inc., One Omega Drive,
P.O. Box 4047, Stamford, CT 06907-0047 USA
Toll-Free: 1-800-826-6342 TEL: [phone]
FAX: [phone] e-mail: [e-mail]

Canada:

976 Bergar
Laval (Quebec), H7L 5A1 Canada
Toll-Free: 1-800-826-6342 TEL: [phone]
FAX: [phone] e-mail: [e-mail]

For immediate technical or

application assistance:

U.S.A. and Canada:

Sales Service: 1-800-826-6342/1-800-TC-OMEGA
Customer Service: 1-800-622-2378/1-800-622-BEST
Engineering Service: 1-800-872-9436/1-800-USA-WHEN

Mexico/Latin America:

En Español: 001 [phone]
FAX: [phone]
e-mail: [e-mail]

[e-mail]

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Benelux:

Managed by the United Kingdom Office
Toll-Free: 0800 099 3344 TEL: [phone]
FAX: [phone] e-mail: [e-mail]

Czech Republic:

Frystatska 184, 733 01 Karviná, Czech Republic
Toll-Free: 0800-1-66342 TEL: [phone]
FAX: [phone]
e-mail: [e-mail]

It is the policy of OMEGA Engineering, Inc. to comply with all worldwide safety and EMC/EMI regulations that apply. OMEGA is constantly pur­suing certification of its products to the European New Approach Directives. OMEGA will add the CE mark to every appropriate device upon
certification.

The information contained in this document is believed to be correct, but OMEGA accepts no liability for any errors it contains,
and reserves the right to alter specifications without notice.
WARNING: These products are not designed for use in, and should not be used for, human applications.

Direct all warranty and r epair requests/ inquirie s to the O MEGA Cus tomer Se rvice De partment. BEFORE RETURNING ANY
PRODUCT(S) TO OMEGA, PURCHASER MUST OBTAIN AN AUTHORIZED RETURN (AR) NUMBER FROM OMEGA’S CUSTOMER
SERVICE DEPARTMENT (IN ORDER TO AVOID PROCESSING DELAYS). The assigned AR number should then be marked on the
outside of the return package and on any correspondence. The purchaser is responsible for shipping charges, freight, insurance
and proper packaging to prevent breakage in transit.

FOR WARRANTY RETURNS, please have the following
information available BEFORE contacting OMEGA:

1.Purchase Order number under which the product was
PURCHASED,

2.Model and serial number of the product under warranty, and

3.Repair instructions and/or specific problems relative to the
product.

OMEGA’s policy is to make running changes, not model changes, whenever an improvement is possible. This affords our customers
the latest in technology and engineering.OMEGA is a registered trademark of OMEGA ENGINEERING, INC.
© Copyright 2010 OMEGA ENGINEERING, INC. All rights reserved. This document may not be copied, photocopied, reproduced,
translated, or reduced to any electronic medium or machine-readable form, in whole or in part, without the prior written consent of
OMEGA ENGINEERING, INC.

Servicing Europe:

France:

Managed by the United Kingdom Office
Toll-Free: 0800 466 342 TEL: [phone]
FAX: [phone] e-mail: [e-mail]

Germany/Austria:

Daimlerstrasse 26
D-75392 Deckenpfronn, Germany
Toll-Free: 0800 6397678 TEL: [phone]
FAX: [phone] e-mail: [e-mail]

RETURN REQUESTS / INQUIRIES

FOR NON-WARRANTY REPAIRS,
for current repair charges. Have the following
information available BEFORE contacting OMEGA:

1. Purchase Order number to cover the COST of the repair,

2.Model and serial number of the product, and

3.Repair instructions and/or specific problems relative to the
product.

United Kingdom: ISO 9001 Certified

OMEGA Engineering Ltd.
One Omega Drive, River Bend Technology
Centre, Northbank, Irlam, Manchester
M44 5BD United Kingdom
Toll-Free: 0800-488-488
TEL: [phone]
FAX: [phone]
e-mail: [e-mail]

consult OMEGA

TABLE OF

CONTENTS

TX91
Miniature Two-Wire Thermocouple Transmitter

Page

Section 1 Introduction 1

1.1 General Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

1.2 Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

1.3 Models Available . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Section 2 Unpacking Instructions 9
Section 3 Installation 11

3.1 Mounting the TX91 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

3.2 Wiring the TX91 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

i

TABLE OF

CONTENTS

TX91
Miniature Two-Wire Thermocouple Transmitter

Page

Section 4 Calibration Instructions 18

4.1 Equipment Required . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

4.2 Set-up of Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

4.3 Calibration Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

Section 5 Troubleshooting Guide 25
Section 6 Accessories 26
Section 7 Specifications 27
Appendix A

Intrinsically Safe Interconnection Diagram . . . . . . . . . . . . . . . . . . . . . 30

ii

1

Introduction

1.1 General Description

The OMEGA®TX90 Series Temperature Transmitters consist of the
TX91 Miniature Two-Wire Thermocouple Transmitter and the
TX92 Miniature Two-Wire RTD Transmitter. This manual is written
for the OMEGA TX91 Thermocouple Transmitter.

The TX91 Transmitter accepts thermocouple sensor types J, K, T,
or E and will produce a standard 4-20 mA output signal propor­tional to that produced by its attached input temperature sensor.
Transmission of the proportional current output may be
accomplished by using copper wires.

1

Introduction 1

(For Mounting)

Figure 1-1. Photo of TX90 Series Transmitter
Figure 1-2. General Dimensions (in inches)

12

1 Introduction

The TX91 transmitter is normally powered by an unregulated DC
power supply as shown in Figure 1-3. The proportionally-transmit­ted signal begins at 4 mA, at the low end of its temperature range,
and increases to 20 mA, at the high end of its temperature range.
(There are various temperature ranges and thermocouple types
available for the TX91. To order, refer to Section 1.3 for correct
Model Numbers and Range Codes.)

THERMOCOUPLE

TX91

THERMOCOUPLE

TRANSMITTER

Input

3

Figure 1-3. TX91 Thermocouple Transmitter

COPPER

WIRES

DC SUPPLY
11-44 VDC

Introduction 1

The TX91 two-wire transmitter receives and measures signals from
thermocouples and sends an output current of 4-20 mA which is directly
proportional to the thermocouple millivolt input. It is designed to
connect with only two copper wire leads that will supply the voltage to
operate the transmitter from a DC power supply, and also carry the
output current. The output current is then used for recording, computing
or controlling.

If the TX91 is mounted inside a protection head, such as the OMEGA
NB1 Protection Head (see Figure 3-1), the thermocouple extension wires
are replaced by two copper wires that carry the 4-20 mA signal and DC
voltage to operate the transmitter. (Refer to the OMEGA Temperature
Handbook for information on NB1 Thermocouple Assembly.)

04

Introduction 1

The TX91 has reverse supply polarity protection and will operate with a
wide range of supply voltages (11 to 44VDC). It has an input sensor
break-protection circuit that forces the output current to go upscale when
the thermocouple wire opens. It also is provided with a screw terminal,
where the output current can be measured without interrupting the
power loop. The TX91 does NOT provide isolation between its input and
the 4-20 mA output; therefore, an undergrounded thermocouple junction
is suggested to prevent possible ground loops.

Note that most thermocouple transmitters with 4-20 mA outputs,
including the TX91, are proportional with respect to the thermocouple
input voltage. However, the relationship between temperature and
millivolt for all the thermocouple types is somewhat non-linear. This
leads to maximum error at approximately the midpoint of the range as

05

shown in Figure 1-4.

1 Introduction

Figure 1-4. Straight line Approximation of Curve

06