Rockwell Automation Allen-Bradley 794-IRT8 User manual

FLEXI/OThermocouple,RTD,andMillivolt
Input Modules
Catalog Numbers 1794-IRT8, 1794-IRT8K, 1794-IRT8XT
User Manual

Important User Information
Solid state equipment has operational characteristics differing from those of electromechanical equipment. Safety Guidelines for the Application,
Installation and Maintenance of Solid State Controls (publication SGI-1.1 available from your local Rockwell Automation sales office or online at
http://literature.rockwellautomation.com) describes some important differences between solid state equipment and hard-wired electromechanical
devices. Because of this difference, and also because of the wide variety of uses for solid state equipment, all persons responsible for applying this
equipment must satisfy themselves that each intended application of this equipment is acceptable.
In no event will Rockwell Automation, Inc. be responsible or liable for indirect or consequential damages resulting from the use or application of this
equipment.
The examples and diagrams in this manual are included solely for illustrative purposes. Because of the many variables and requirements associated
with any particular installation, Rockwell Automation, Inc. cannot assume responsibility or liability for actual use based on the examples and
diagrams.
No patent liability is assumed by Rockwell Automation, Inc. with respect to use of information, circuits, equipment, or software described in this
manual.
Reproduction of the contents of this manual, in whole or in part, without written permission of Rockwell Automation, Inc., is prohibited.
Throughout this manual, when necessary, we use notes to make you aware of safety considerations.
Allen-Bradley, Rockwell Automation, FLEX I/O, RSLinx, RSLogix 5000 and TechConnect are trademarks of Rockwell Automation, Inc.
Trademarks not belonging to Rockwell Automation are property of their respective companies.
WARNING
Identifies information about practices or circumstances that can cause an explosion in a hazardous environment, which may
lead to personal injury or death, property damage, or economic loss.
IMPORTANT
Identifies information that is critical for successful application and understanding of the product.
ATTENTION
Identifies information about practices or circumstances that can lead to: personal injury or death, property damage, or
economic loss. Attentions help you identify a hazard, avoid a hazard, and recognize the consequence.
SHOCK HAZARD
Labels may be on or inside the equipment, such as a drive or motor, to alert people that dangerous voltage may be present.
BURN HAZARD
Labels may be on or inside the equipment, such as a drive or motor, to alert people that surfaces may reach dangerous
temperatures.

iii Publication 1794-6.5.12 - September 2011
Summary of Changes
This manual contains new and updated information. Changes throughout this
revision are marked by change bars, as shown to the right of this paragraph.
New and Updated
Information
This table contains the changes made to this revision.
Additional less significant changes (such as improvement of drawings) have
been made throughout the document.
Changes Page
Addition of two catalogs – 1794-IRT8K and 1794-IRT8XT 1, 53
The following sections have been added to Chapter 1 – Overview of FLEX I/O
and Your Thermocouple, RTD, and Millivolt Input Module:
•The FLEX System
•Types of Modules
•What the FLEX I/O Input Module Does
•The FLEX I/O Module in a Logix Control System
1
The following section has been added to Chapter 2 – Install Your FLEX I/O Input
Module:
•Series A and Series B
8
The following new topics have been added:
•Configure Your FLEX I/O Module with RSLogix 5000 Software
(Chapter 3)
•Troubleshoot the Module (Chapter 6)
21
51
•Electronic Data Sheet (EDS) Files (Appendix B) 57
The following topic, previously Chapter 3 in the last revision, has been
relegated to the Appendices section:
•Program Your Thermocouple/RTD Input Module (Appendix C) 59

Publication 1794-6.5.12 - September 2011
iv Summary of Changes
Notes:

vPublication 1794-6.5.12-EN-E - September 2011
Table of Contents
Summary of Changes
New and Updated Information. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iii
Preface
Who Should Use This Manual. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ix
Purpose of the Manual. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ix
About the Vocabulary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ix
Related Documentation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . x
Common Techniques Used in this Manual. . . . . . . . . . . . . . . . . . . . . . xii
Chapter 1
Overview of FLEX I/O and Your
Thermocouple, RTD, and
Millivolt Input Module
Overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
The FLEX System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Types of Modules. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
What the FLEX I/O Input Module Does . . . . . . . . . . . . . . . . . . . . . . . 2
The FLEX I/O Module in a Logix Control System . . . . . . . . . . . . . . . 3
Physical Features of Your Module . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Chapter Summary. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Chapter 2
Install Your FLEX I/O Input
Module
Overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Before You Install Your Module . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Series A and Series B . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Power Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Install the Module . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Mount on a DIN Rail . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Mount on a Panel or Wall . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Mount the FLEX I/O Module on the Terminal Base Unit . . . . . 14
Wiring Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Connect Wiring to the FLEX I/O Module . . . . . . . . . . . . . . . . . . 16
Identify RTD Wire Pairs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Chapter Summary. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Chapter 3
Configure Your FLEX I/O
Module with RSLogix 5000
Software
Overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Add and Configure the FLEX I/O Module. . . . . . . . . . . . . . . . . . . . . 21
Chapter Summary. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Chapter 4
Read and Write Configuration
Maps for the FLEX I/O Module
Overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
Configure Your Input Module . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
Configurable Options and Their Effect on the Channels . . . . . . . . . . 27
Options that Affect All Channels . . . . . . . . . . . . . . . . . . . . . . . . . . 27
Options that Affect Each Group of Four Inputs . . . . . . . . . . . . . 28
Sensor Types. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Read Data From the Module. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

Publication 1794-6.5.12-EN-E - September 2011
vi Table of Contents
Map Data for the Module . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Thermocouple and RTD Input Module Image Table
Mapping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
Block Transfer Read and Write . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
Bit/Word Descriptions for the Input Module Block Transfer
Read Words . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
Using Series A Functionality in a
Series B Module . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
Chapter Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
Chapter 5
Calibrate Your Module Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
When and How to Calibrate Your FLEX I/O Module. . . . . . . . . . . . 39
Tools and Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
Calibrate Your Input Module. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
Calibration Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
Wiring Connections for Calibrating the Thermocouple and
RTD Input Module . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
Read and Write Words for Calibration. . . . . . . . . . . . . . . . . . . . . . 42
EDT Calibration Command and Command Data Summary . . . . 44
Offset Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
Gain Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
Current Source Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
Cold Junction Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
Channel Loop Compensation Calibration . . . . . . . . . . . . . . . . . . . 49
Chapter Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
Chapter 6
Troubleshoot the Module Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
Module Indicators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
Chapter Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
Appendix A
Specifications Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
General Specifications. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
Environmental Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
Certifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
Appendix B
Electronic Data Sheet (EDS)
Files
Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
Updating EDS File . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
EDS Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58

Publication 1794-6.5.12-EN-E - September 2011
Table of Contents vii
Appendix C
Programming Your Module
with PLC Family Processors
Overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
Enter Block Transfer Instructions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
PLC-2 Family Processor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
PLC-3 Family Processor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
PLC-5 Family Processor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
PLC-5/250 Family Processor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62
Appendix D
Safety Approvals European Hazardous Location Approval. . . . . . . . . . . . . . . . . . . . . . . 65
North American Hazardous Location Approval . . . . . . . . . . . . . . . . . 66
Index

Publication 1794-6.5.12-EN-E - September 2011
viii Table of Contents
Notes:

ix Publication 1794-6.5.12 - September 2011
Preface
Read this preface to familiarize yourself with the rest of the manual. It provides
information concerning:
• who should use this manual
• the purpose of this manual
• related documentation
• conventions used in this manual
• terminology used in this manual
Who Should Use This
Manual
We assume that you have previously used an Allen-Bradley programmable
controller, that you are familiar with its features, and that you are familiar with
the terminology we use. If not, read the user manual for your processor before
reading this manual.
Purpose of the Manual
This manual is a reference guide for the FLEX I/O Thermocouple, RTD,
Millivolt Input Modules. It describes the procedures for installing, configuring
and troubleshooting your module. For more information, consult the
following chapters.
About the Vocabulary
This manual covers the 1794-IRT8, 1794-IRT8K, and 1794-IRT8XT modules,
which are identical, except that the 1794-IRT8K is conformally coated.
In this manual, we refer to:
• the individual Thermocouple, RTD, and mV module as the “module,”
or “TC, RTD, and mV module.”
• the programmable controller as the “controller” or the “processor.”
Topic See
Overview of FLEX I/O and Your Thermocouple, RTD, and Millivolt Input Module Chapter 1
Install Your FLEX I/O Input Module Chapter 2
Configure Your FLEX I/O Module with RSLogix 5000 Software Chapter 3
Read and Write Configuration Maps for the FLEX I/O Module Chapter 4
Calibrate Your Module Chapter 5
Troubleshoot the Module Chapter 6
Specifications Appendix A
Electronic Data Sheet (EDS) Files Appendix B
Programming Your Module with PLC Family Processors Appendix C
Safety Approvals Appendix D

Publication 1794-6.5.12 - September 2011
x Preface
Related Documentation
The following documents contain additional information about Rockwell
Automation products. To obtain a copy, contact your local
Rockwell Automation office or distributor.
Resource Description
FLEX I/O Product Profile, publication 1794-PP019 xxxxx Comprehensive product profile for the FLEX I/O product line.
FLEX I/O ControlNet Redundant Media Adapter,
publication 1794-5.18 x xxxx
Information on how to install the FLEX I/O ControlNet Redundant Media
Adapter (1794-ACNR).
FLEX I/O EtherNet/IP Adapter Module Installation
Instructions, publication 1794-IN082 x xxxx
Information on how to install the FLEX I/O EtherNet/IP Adapter Module
(Catalog No. 1794-AENT).
FLEX I/O ControlNet Adapter Module Installation
Instructions, publication 1794-IN128 x xxxx
Information on how to install the ControlNet Adapter Modules
(Catalog No. 1794-ACN15, 1794-ACN15K, 1794-ACNR15, 1794-ACNR15XT,
Series D).
FLEX I/O DeviceNet Adapter Module Installation
Instructions, publication 1794-IN099 x xxxxxxxxxxxxx
Information on how to install the FLEX I/O DeviceNet Adapter Modules
(Catalog No. 1794-ADN, 1794-ADNK).
Remote I/O Adapter Modules Installation Instructions,
publication 1794-IN098 x xxxxxxxxxxxxx
Information on how to install the Remote I/O Adapter Modules
(Catalog No. 1794-ASB, 1794-ASB2, 1794-ASBK, 1794-ASB2K).
Remote I/O Adapter Module User Manual, publication
1794-UM009 x xxxxxxxxxxxxx
Information on how to use the Remote I/O Adapter Module
(Catalog No. 1794-ASB).
FLEX I/O PROFIBUS Adapter Module Installation
Instructions, publication 1794-IN087 x xxxxxxxxxxxxx
Information on how to install the FLEX I/O PROFIBUS Adapter
(Catalog No. 1794-APB).
FLEX I/O PROFIBUS Adapter Module User Manual,
publication 1794-UM057 x xxxxxxxxxxxxx
Information on how to use the FLEX I/O PROFIBUS Adapter Module
(Catalog No. 1794-APB).
Flex I/O Digital Input Modules Installation Instructions,
publication 1794-IN093 x xxxxxxxxxxxxx
Information on how to install the Flex I/O Digital Input Modules
(Catalog No. 1794-IB8, 1794-IB16, 1794-IB16K, 1794-IB32).
Flex I/O Digital DC Sourcing Input and Sinking Output
Modules Installation Instructions,
publication 1794-IN095 x xxxxxxxxxxxxx
Information on how to install the Flex I/O Digital DC Sourcing Input and
Sinking Output Modules (Catalog No. 1794-IV16, 1794-OV16, 1794-OV16P).
Flex I/O Digital DC Sourcing Output Modules Installation
Instructions, publication 1794-IN094 x xxxxxxxxxxxxx
Information on how to install the Flex I/O Digital DC Sourcing Output Modules
(Catalog No. 1794-OB8, 1794-OB8EP, 1794-OB16, 1794-OB16P, 1794-OB32P).
Flex I/O Input/ Output Module Installation Instructions,
publication 1794-IN083 x xxxxxxxxxxxxx
Information on how to install the Flex I/O Input/ Output Modules
(Catalog No. 1794-IB16XOB16P, 1794-IB10XOB6).
Flex I/O 8 Output Relay Module Installation Instructions,
publication 1794-IN019 x xxxxxxxxxxxxx
Information on how to install the Flex I/O 8 Output Relay Modules
(Catalog No. 1794-OW8, 1794-OW8K, 1794-OW8XT).
FLEX I/O Input, Output and Input/Output Analog Modules
Installation Instructions, publication 1794-IN100 xxxxxxx
Information on how to install the FLEX I/O Input, Output and Input/Output
Analog Modules (Catalog No. 1794-IE8, 1794-IE4XOE2, 1794-OE4, 1794-IE8K,
1794-OE4K).
FLEX I/O Analog Module User Manual,
publication 1794-6.5.2 x xxxxxxxxxxxxx
Information on how to install the FLEX I/O Analog Modules
(Catalog No. 794-OE4, 1794-IE8, 1794-IE12, 1794-OE12, 1794-IE4XOE2,
1794-IE8XOE4, 1794-IE4XOE2XT, 1794-IE8XT, 1794-OE4XT).
FLEX I/O Isolated Analog Output Module Installation
Instructions, publication 1794-IN037 x xxxxxxxxxxxxx
Information on how to install the FLEX I/O Isolated Analog Output Module
(Catalog No. 1794-OF4I).

Publication 1794-6.5.12 - September 2011
Preface xi
FLEX I/O 4 Isolated Input Module Installation Instructions,
publication 1794-IN038 x xxxxxxxxxxxxx
Information on how to install the FLEX I/O 4 Isolated Input Module
(Catalog No. 1794-IF4I).
FLEX I/O 2 In/2 Out Isolated Analog Combo Module
Installation Instructions, publication 1794-IN039 x
xxxxxxxxxxxxx
Information on how to install the FLEX I/O 2 In/2 Out Isolated Analog Combo
Module (Catalog No. 1794-IF2XOF2I).
FLEX I/O Isolated Analog Modules User Manual,
publication 1794-6.5.8 x xxxxxxxxxxxxx
Information on how to use the FLEX I/O Isolated Analog Modules
(Catalog No. 1794-IF4I, 1794-OF4I, 1794-IF2XOF2I, 1794-IF4IXT, 1794-IF4ICFXT,
1794-OF4IXT, 1794-IF2XOF2IXT).
FLEX I/O 8 Thermocouple Input Module Installation
Instructions, publication 1794-IN021 x xxxxxxxxxxxxx
Information on how to install the FLEX I/O 8 Thermocouple Input Modules
(Catalog No. 1794-IT8, 1794-IR8).
FLEX I/O 8 Input RTD Module User Manual,
publication 1794-6.5.4 x xxxxxxxxxxxxx
Information on how to use the FLEX I/O 8 Input RTD Module
(Catalog No. 1794-IR8).
FLEX I/O Thermocouple/Millivolt Input Module User
Manual, publication 1794-6.5.7 x xxxxxxxxxxxxx
Information on how to use the Thermocouple and Millivolt Input Module
(Catalog No. 1794-IT8).
FLEX I/O Thermocouple/RTD Input Analog Module
Instructions, publication 1794-IN050 x xxxxxxxxxxxxx
Information on how to install the Thermocouple/Millivolt Input Modules
(Catalog No. 1794-IRT8, 1794-IRT8K, 1794-IRT8XT).
2-Input Frequency Module Installation Instructions,
publication 1794-IN049 x xxxxxxxxxxxxx
Information on how to install the 2-Input Frequency Module
(Catalog No. 1794-IJ2, 1794-IJ2K, 1794-IJ2XT).
FLEX I/O Frequency Input Module User Manual,
publication 1794-6.5.11 x xxxxxxxxxxxxx
Information on how to use the FLEX I/O Frequency Input Module
(Catalog No. 1794-IJ2).
24V FLEX I/O 2 Channel Incremental Encoder Module
Installation Instructions, publication 1794-IN063 x
xxxxxxxxxxxxx
Information on how to install the 24V FLEX I/O 2 Channel Incremental Encoder
Module (Catalog No. 1794-ID2).
FLEX Integra Analog Module User Manual,
publication 1793-6.5.1 x xxxxxxxxxxxxx
Information on how to install the FLEX Integra Analog Module (Catalog No.
1793-IE2X0E1,1793-IE2XOE1S, 1793-IE4, 1793-IE4S, 1793-OE2, 1793-OE2S).
FLEX I/O 4 Channel Pulse Counter Module Installation
Instructions, publication 1794-IN064 x xxxxxxxxxxxxx
Information on how to install the 24V DC FLEX I/O 4-Channel Module
(Catalog No. 1794-IP4).
FLEX I/O Very High Speed Counter Module Installation
Instruction, publication 1794-IN067 x xxxxxxxxxxxxx
Information on how to install the Very High Speed Counter Module
(Catalog No. 1794-VHSC).
FLEX I/O 48V DC Input and Output Modules Installation
Instructions, publication 1794-IN105 x xxxxxxxxxxxxx
Information on how to install the FLEX I/O 48V DC Input and Output Modules
(Catalog No. 1794-IC16, 1794-OC16).
FLEX I/O AC Digital Input Modules Installation
Instructions, publication 1794-IN102 x xxxxxxxxxxxxx
Information on how to install the FLEX I/O AC Input Modules
(Catalog No. 1794-IA8, 1794-IA8I, 1794-IA16).
FLEX I/O Digital AC Output Modules Installation
Instructions, publication 1794-IN103 x xxxxxxxxxxxxx
Information on how to install the FLEX I/O Digital AC Output Modules
(Catalog No. 1794-OA8, 1794-OA8K, 1794-OA8I, 1794-OA16).
FLEX I/O 220V AC Input and Output Modules Installation
Instructions, publication 1794-IN104 x xxxxxxxxxxxxx
Information on how to install the FLEX I/O 220V AC Input and Output Modules
(Catalog No. 1794-IM8, 1794-OM8).
FLEX I/O Terminal Base Units Installation Instructions,
publication 1794-IN092 x xxxxxxxxxxxxx
Information on how to install the FLEX I/O Terminal Base Units
(Catalog No. 1794-TB2, 1794-TB3, 1794-TB3K, 1794-TB3S, 1794-TB32,
1794-TB3G, 1794-TB3GK, 1794-TB3GS, 1794-TB3T, 1794-TB3TS, 1794-TBN,
1794-TBNK, 1794-TBNF).
Interconnect Cable Installation Instructions,
publication 1794-5.12 x xxxxxxxxxxxxx
Information on how to install the Interconnect Cable
(Catalog No. 1794-CE1, 1794-CE3).
Resource Description

Publication 1794-6.5.12 - September 2011
xii Preface
Common Techniques Used
in this Manual
The following conventions are used throughout this manual:
• Bulleted lists such as this one provide information, not procedural steps.
• Numbered lists provide sequential steps or hierarchical information.
•Italic type is used for emphasis.
FLEX I/O DC Power Supply Installation Instructions,
publication 1794-IN069 x xxxxxxxxxxxxx
Information on how to install the FLEX I/O DC Power Supply
(Catalog No. 1794-PS13, 1794-PS3).
Industrial Automation Wiring and Grounding Guidelines,
publication 1770-4.1 x xxxxxxxxxxxxx
In-depth information on grounding and wiring Allen-Bradley programmable
controllers.
Rockwell Automation Industrial Automation Glossary,
AG-7.1 x xxxxxxxxxxxxx
A glossary of industrial automation terms and abbreviations.
Resource Description

1Publication 1794-6.5.12 - September 2011
Chapter 1
Overview of FLEX I/O and Your Thermocouple,
RTD, and Millivolt Input Module
Overview
This chapter provides a description of the FLEX I/O Thermocouple, RTD,
and Millivolt Input module and an overview of how it communicates with
programmable controllers.
The FLEX System
FLEX I/O is a small, modular I/O system for distributed applications that
performs all of the functions of rack-based I/O. The FLEX system contains
the following components shown below:
• Adapter – transfers read and write configuration data to and from the
I/O module
• Terminal base – contains a terminal strip to terminate wiring for two- or
three-wire devices
• I/O module – contains the bus interface and circuitry needed to
perform specific functions related to your application
Topic Page
The FLEX System 1
Types of Modules 2
What the FLEX I/O Input Module Does 2
The FLEX I/O Module in a Logix Control System 3
Physical Features of Your Module 4
Chapter Summary 5
I/O moduleTerminal baseAdapter
1794-IRT8
2
+
2
+
45374

Publication 1794-6.5.12 - September 2011
2 Overview of FLEX I/O and Your Thermocouple, RTD, and Millivolt Input Module
The FLEX system consists of an adapter module, terminal base unit, DIN rail,
power supply, and adapter cabling components. You can use up to 8 terminal
bases per adapter module.
For detailed instructions on how to set up and install your module, refer to the
topic, Install Your FLEX I/O Input Module, on page 7.
Types of Modules
The module refer to the following catalogs.
The module accepts up to 8 thermocouple or RTD inputs. The inputs are
nonisolated and are selected with analog multiplexers. The inputs accept
millivolt or resistive inputs. Default input spans are -40.00 mV… +100.00 mV
or 0.0…500.0 Ω. Fault indicators are located on the field side.
No switches or jumpers are used on the TC and RTD Input module. The
inputs have both fixed hardware filters and selectable firmware digital filters.
What the FLEX I/O Input
Module Does
The module is a high-speed, high-accuracy temperature and millivolt
measuring module that accepts thermocouple inputs, 2-, 3-, and 4-wire RTD
inputs, and mV source inputs.
It offers the following:
• wire-off, over-range, and under-range detection
• good common mode rejection
• usage with long thermocouple wiring
• usage with grounded or ungrounded thermocouples
The Series B version of 1794-IRT8 provides capability to work with grounded
thermocouples.
Use cold junction compensators (cat. no. 1794-CJC2) in thermocouple mode.
Two cold junction compensators are shipped with the 1794-IRT8.
Catalog No. Voltage Inputs Description
1794-IRT8 24V DC 8 Analog – 8-pt, 16 bit non-isolated RTD,
thermocouple and mV Input module
1794-IRT8K 24V DC 8 Analog – 8-pt, 16 bit non-isolated RTD,
thermocouple and mV Input module.
Conformally coated module.
1794-IRT8XT 24V DC 8 Analog – 8-pt, 16 bit non-isolated RTD,
thermocouple and mV Input module designed
for extended temperature.

Publication 1794-6.5.12 - September 2011
Overview of FLEX I/O and Your Thermocouple, RTD, and Millivolt Input Module 3
The FLEX I/O Module in a
Logix Control System
The FLEX I/O Thermocouple, RTD, and Millivolt modules are intelligent
modules that interface analog signals with Rockwell Automation
programmable controllers through a FLEX I/O adapter module.
The adapter transfers data to and from the module. These transfers allow:
• the adapter to obtain input or output values and status from the module
• the user to establish the mode of operation through a process called
configuration
The following illustration shows the flow of communication between the
adapter and the I/O module.
Typical Communication Between the Adapter and a Module
IN 0 IN 2 IN 4 IN 6IN 1 IN 3 IN 5 IN 7
TC RTD INPUT 8 CHANNEL
3
1794-IRT8
PWR
FF F F F F F F
45316
The adapter transfers your configuration data.
FlexBus
External devices transmit
analog signals to the
module.
The module converts
analog signals into binary
format and stores these
values until the adapter
requests their transfer.
The adapter receives data
from the modules and stores
it in the data table.
The adapter module determines that the
transfer was made without error and
input values are within specified range.
Your ladder program can use and/or
move the data (if valid) before it is
overwritten by the transfer of new data
in a subsequent transfer.
1
4
5
6
2
3
New configuration data can be sent to
the module any time during operation.
7
1794-ACN15
1794-ACNR15
1794-ACNR15K
1794-ADN
1794-AENT
1794-APBDPV1
1794-ASB
1794-APB
Adapter
1794-AENT shown

Publication 1794-6.5.12 - September 2011
4 Overview of FLEX I/O and Your Thermocouple, RTD, and Millivolt Input Module
A broader view of how the FLEX I/O module interfaces with the different
elements in a Logix system is shown in the sample illustration below.
In this example, the FLEX I/O module communicates with the controller
through the adapter. The controller can produce and consume tags. It can
initiate MSG instructions that send and receive data or configure devices.
Configuration of devices and the network is done through the personal
computer running the controller and configuration software.
To learn the prerequisites and steps to configure your FLEX I/O module
using RSLogix 5000 software, see Configure Your FLEX I/O Module with
RSLogix 5000 Software on page 21.
.
Physical Features of Your
Module
The module label identifies the keyswitch position, wiring and module type. A
removable label provides space for writing individual designations per your
application. Indicators are provided to identify input fault conditions, and to
show when power is applied to the module.
Bridge
PanelView Station
Ethernet
PC running
controller and
Rockwell Automation
configuration software
1794 adapter
1794 FLEX I/O module
FLEX System
45567
ATTENTION
The following publications provide more information about
EtherNet/IP, and ControlNet modules in a Logix5000 system:
•EtherNet/IP Modules in Logix5000 Control Systems,
publication ENET-UM001
•ControlNet Modules in Logix5000 Control Systems,
publication CNET-UM001

Publication 1794-6.5.12 - September 2011
Overview of FLEX I/O and Your Thermocouple, RTD, and Millivolt Input Module 5
Module Label and Indicators
Chapter Summary
In this chapter, you were introduced to the FLEX I/O system and the
Thermocouple, RTD, and mV input module, and how it communicates with
programmable controllers.
IN 0 IN 2 IN 4 IN 6IN 1 IN 3 IN 5 IN 7
TC RTD INPUT 8 CHANNEL
3
1794-IRT8
PWR
FF F FF F F F
1794-IRT8
Input designators
Module type
Removable label
Keyswitch
position indicator (#3)
Power on indicator
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6 Overview of FLEX I/O and Your Thermocouple, RTD, and Millivolt Input Module
Notes:

7Publication 1794-6.5.12 - September 2011
Chapter 2
Install Your FLEX I/O Input Module
Overview
This chapter provides you with pre-installation requirements and instructions
on how to install your FLEX I/O Thermocouple, RTD, and Millivolt Input
module.
Before You Install Your
Module
Before installing your FLEX I/O Thermocouple, RTD, and mV module, you
need to:
• verify that a suitable enclosure is available for installation of the module,
and
• position the keyswitch on the terminal base.
Topic Page
Before You Install Your Module 7
Series A and Series B 8
Power Requirements 8
Install the Module 10
Mount on a DIN Rail 10
Mount on a Panel or Wall 13
Mount the FLEX I/O Module on the Terminal Base Unit 14
Wiring Information 16
Chapter Summary 20
ATTENTION
These modules do not receive primary operational power from the
backplane. 24V DC power must be applied to your module before
installation. If power is not applied, the module position may appear
to the adapter as an empty slot in your chassis.
ATTENTION
If using a Series B product to replace a Series A product, connect a
wire between terminals 39 and 48 on the 1794-TB3G or 1794-TB3GS
terminal base unit. If not connected, the Series B product defaults to
Series B functionality.

Publication 1794-6.5.12 - September 2011
8 Install Your FLEX I/O Input Module
Series A and Series B
The table, Series A and Series B Differences, describes the differences between
Series A and Series B of the FLEX I/O Thermocouple, RTD, and mV Input
modules.
Power Requirements
The wiring of the terminal base unit is determined by the current draw
through the terminal base. Make certain that the current draw does not
exceed 10 A.
Series A and Series B Differences
Mode 1794-IRT8 Series A 1794-IRT8, 1794-IRT8XT
Series B
Isolation Between user side and
system side
Between user 24V DC and
user I/O; between user side
and system side
Common Mode Range +4V DC +15V DC
Thermocouple Mode
Wire-off Detection
When an open sensor is
detected, data defaults to
maximum value
When open sensor is
detected, data defaults to
minimum value
ATTENTION
In the RSLogix 5000 software, if using a series B product to replace a
series A product, the module will be accepted without an electronic
key mismatch warning.
This is true for 1794-IRT8 and 1794-IRT8XT modules installed on
Ethernet/IP, ControlNet, or Remote I/O networks.
ATTENTION
The CJC Status bit, Read Word 9, Bit 3 is added with the Firmware C
release of the 1794-IRT8 Series B module.
The CJC Status bit is turned On when the temperature between the
CJCs is greater than 6 °C but less than 12 °C.
When this temperature difference is above 12 °C, then the CJC Alarm
bits are set.
Also, if a CJC temperrature is over-range or under-range, then the
associated CJC Alarm bit is set. In this condition, the CJC Status bit is
not set.
The CJC Status bit did not exist in Series A.
ATTENTION
Total current draw through the terminal base unit is limited to 10 A.
Separate power connections may be necessary.