Rockwell Automation Allen-Bradley 1794-IRT8 User manual

User Manual Original Instructions
FLEX I/O Thermocouple/RTD/
Millivolt Input Module
Catalog Numbers 1794-IRT8,1794-IRT8XT

2Rockwell Automation Publication 1794-UM012D-EN-P - March 2023
FLEX I/O Thermocouple/RTD/Millivolt Input Module User Manual
Important User Information
Read this document and the documents listed in the additional resources section about installation, configuration, and operation of this equipment before you
install, configure, operate, or maintain this product. Users are required to familiarize themselves with installation and wiring instructions in addition to
requirements of all applicable codes, laws, and standards.
Activities including installation, adjustments, putting into service, use, assembly, disassembly, and maintenance are required to be carried out by suitably trained
personnel in accordance with applicable code of practice.
If this equipment is used in a manner not specified by the manufacturer, the protection provided by the equipment may be impaired.
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.
These labels may also be on or inside the equipment to provide specific precautions.
The following icon may appear in the text of this document.
Rockwell Automation recognizes that some of the terms that are currently used in our industry and in this publication are not in alignment with the
movement toward inclusive language in technology. We are proactively collaborating with industry peers to find alternatives to such terms and
making changes to our products and content. Please excuse the use of such terms in our content while we implement these changes.
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.
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.
IMPORTANT Identifies information that is critical for successful application and understanding of the product.
SHOCK HAZARD: Labels may be on or inside the equipment, for example, a drive or motor, to alert people that dangerous
voltage may be present.
BURN HAZARD: Labels may be on or inside the equipment, for example, a drive or motor, to alert people that surfaces may
reach dangerous temperatures.
ARC FLASH HAZARD: Labels may be on or inside the equipment, for example, a motor control center, to alert people to potential
Arc Flash. Arc Flash will cause severe injury or death. Wear proper Personal Protective Equipment (PPE). Follow ALL Regulatory
requirements for safe work practices and for Personal Protective Equipment (PPE).
Identifies information that is useful and can help to make a process easier to do or easier to understand.

Rockwell Automation Publication 1794-UM012D-EN-P - March 2023 3
Table of Contents
Preface
About This Publication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Download Firmware, AOP, EDS, and Other Files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Summary of Changes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Additional Resources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Chapter 1
Overview of FLEX I/O and Your
Thermocouple, RTD, and Millivolt
Input Module
Overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
The FLEX System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Types of Modules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
What the FLEX I/O Input Module Does . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
The FLEX I/O Module in a Logix Control System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Physical Features of Your Module . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Chapter 2
Install Your FLEX I/O Input
Module
Overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Before You Install Your Module . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Series A and Series B . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Power Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Install the Module . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Mount on a DIN Rail. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Mount on a Panel or Wall . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Mount the FLEX I/O Module on the Terminal Base Unit . . . . . . . . . . . . . . . . . . . . . . . . . 16
Wiring Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Connect Wiring to the FLEX I/O Module . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Identify RTD Wire Pairs. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Chapter 3
Configure Your FLEX I/O Module
with RSLogix 5000 Software
Overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Add and Configure the FLEX I/O Module . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Chapter 4
Read and Write Configuration
Maps for the FLEX I/O Module
Overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Configure Your Input Module . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Configurable Options and Their Effect on the Channels. . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Options that Affect All Channels. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Options that Affect Each Group of Four Inputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Sensor Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
Read Data From the Module. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
Map Data for the Module . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
Block-transfer Read and Write . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
Series A Functionality in a Series B Module . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

4Rockwell Automation Publication 1794-UM012D-EN-P - March 2023
Table of Contents
Chapter 5
Calibrate Your Module Overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
When and How to Calibrate Your FLEX I/O Module . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
Tools and Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
Calibrate Your Input Module. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
Calibration Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
Read and Write Words for Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
Offset Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
Gain Calibration. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
Current Source Calibration. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
Cold Junction Calibration. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
Channel Loop Compensation Calibration. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
Appendix A
Troubleshoot the Module Overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
Module Indicators. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
Appendix B
Electronic Data Sheet (EDS) Files Overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
Updating EDS File . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
EDS Installation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
Appendix C
Program Your Module with PLC
Family Processors
Overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
Enter Block Transfer Instructions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
PLC-2 Family Processor. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
PLC-3 Family Processor. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
PLC-5 Family Processor. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
PLC-5/250 Family Processor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
Appendix D
Resolution Curves for
Thermocouples
Type B Thermocouple . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
Type E Thermocouple . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
Type C Thermocouple . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
Type J Thermocouple . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
Type K Thermocouple . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
Type R Thermocouple . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
Type S Thermocouple. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
Type T Thermocouple. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
Type N Thermocouple . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
Type TXK/XK(L) Thermocouple . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
Index. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57

Rockwell Automation Publication 1794-UM012D-EN-P - March 2023 5
Preface
About This Publication 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.
Download Firmware, AOP,
EDS, and Other Files
Download firmware, associated files (such as AOP, EDS, and DTM), and access product release
notes from the Product Compatibility and Download Center at rok.auto/pcdc.
Summary of Changes This publication contains the following new or updated information. This list includes substantive
updates only and is not intended to reflect all changes.
Additional Resources These documents contain additional information concerning related products from Rockwell
Automation. You can view or download publications at rok.auto/literature.
Topic Page
Updated template throughout
Added inclusive terminology statement 2
Corrected wording in an Important table 18
Resource Description
FLEX I/O Thermocouple/RTD Input Analog Module Installation Instructions,
publication 1794-IN050 Information on how to install the Thermocouple/Millivolt Input Modules (1794-IRT8, 1794-IRT8XT).
EtherNet/IP Network Devices User Manual, publication ENET-UM006 Describes how to configure and use EtherNet/IP™ devices to communicate on the EtherNet/IP
network.
ControlNet Network Configuration User Manual, publication CNET-UM001 Describes how to use ControlNet® communication modules with Logix 5000® controllers.
Ethernet Reference Manual, publication ENET-RM002 Describes basic Ethernet concepts, infrastructure components, and infrastructure features.
Industrial Automation Wiring and Grounding Guidelines, publication 1770-4.1 Provides general guidelines for installing a Rockwell Automation industrial system.
Product Certifications website, rok.auto/certifications Provides declarations of conformity, certificates, and other certification details.

6Rockwell Automation Publication 1794-UM012D-EN-P - March 2023
Preface
Notes:

Rockwell Automation Publication 1794-UM012D-EN-P - March 2023 7
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 functions of
rack-based I/O. The FLEX system contains the following components shown:
• 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 that is needed to perform specific
functions that are related to your application.
The FLEX system consists of an adapter, terminal base unit, DIN rail, power supply, and adapter
cabling components. You can use up to eight terminal bases per adapter.
For detailed instructions on how to set up and install your module, see Install Your FLEX I/O Input
Module on page 11.
Types of Modules The module refers to the following catalogs:
The module accepts up to eight 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 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.
I/O moduleTerminal baseAdapter
1794-IRT8
2
+
2
+
Catalog Number Voltage Inputs Description
1794-IRT8 24V DC 8 Analog – 8 pt, 16 bit non-isolated RTD, thermocouple, and mV
Input module
1794-IRT8XT 24V DC 8 Analog – 8 pt, 16 bit non-isolated RTD, thermocouple, and mV
Input module designed for extended temperature.

8Rockwell Automation Publication 1794-UM012D-EN-P - March 2023
Chapter 1 Overview of FLEX I/O and Your Thermocouple, RTD, and Millivolt Input Module
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, overrange, and underrange 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 (catalog number 1794-CJC2) in thermocouple mode. Two cold
junction compensators are shipped with the 1794-IRT8.
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 Allen-Bradley® programmable controllers through a FLEX I/O adapter.
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.
• Establishing the mode of operation through a process called configuration.
Figure 1 shows the flow of communication between the adapter and the I/O module.
Figure 1 - 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
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 determines that the transfer was made
without error and input values are within specified
range.
Your ladder program can use “and/or” to 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
anytime during operation.
7
FLEX Adapters:
1794-ACN15
1794-ACNR15
1794-ACNR15K
1794-ADN
1794-AENT
1794-APBDPV1
1794-ASB
Adapter
1794-AENT
shown

Rockwell Automation Publication 1794-UM012D-EN-P - March 2023 9
Chapter 1 Overview of FLEX I/O and Your Thermocouple, RTD, and Millivolt Input Module
Figure 2 shows a broader view of how the FLEX I/O module interfaces with the different elements in
a Logix system.
Figure 2 - FLEX I/O Modules in a Logix System
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 about the prerequisites and steps to configure your FLEX I/O module using Studio 5000
Logix Designer® application(1), 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.
Figure 3 - Module Label and Indicators
Bridge
PanelView
TM
terminal
Ethernet
PC running
controller and
Rockwell Automation
configuration software
1794 adapter
1794 FLEX I/O module
FLEX system
Logix 5000 controller
(1) Studio 5000 Logix Designer is the replacement for RSLogix 5000® (version 20 or later). It provides one software package for
discrete, process, batch, motion, safety, and drive-based applications.
ATTENTION: The following publications provide more information about
EtherNet/IP, and ControlNet modules in a Logix 5000 system:
• EtherNet/IP Network Devices User Manual, publication ENET-UM006.
• ControlNet Network Configuration User Manual, publication CNET-UM001.
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

10 Rockwell Automation Publication 1794-UM012D-EN-P - March 2023
Chapter 1 Overview of FLEX I/O and Your Thermocouple, RTD, and Millivolt Input Module
Notes:

Rockwell Automation Publication 1794-UM012D-EN-P - March 2023 11
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 must:
• Verify that a suitable enclosure is available for installation of the module, and
• Position the keyswitch on the terminal base.
Series A and Series B
Table 1 describes the differences between Series A and Series B of the FLEX I/O Thermocouple, RTD,
and mV Input modules.
ATTENTION:
• These modules do not receive primary operational power from the backplane.
You must apply 24V DC power to your module before installation. If you don’t apply
power, the module position may appear to the adapter as an empty slot in your
chassis.
• 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.
Table 1 - 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 an open sensor is detected, data defaults to minimum value
ATTENTION:
• In the Studio 5000 Logix Designer application, if you use a series B product to
replace a series A product, the module is accepted without an electronic key
mismatch warning.
• This is true for 1794-IRT8 and 1794-IRT8XT modules that are installed on
EtherNet/IP, ControlNet, or Remote I/O networks.
• The CJC Status bit, Read Word 9, Bit 3 are added with 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.
• If a CJC temperature is overrange or underrange 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.

12 Rockwell Automation Publication 1794-UM012D-EN-P - March 2023
Chapter 2 Install Your FLEX I/O Input Module
Power Requirements The wiring of the terminal base unit is determined by the current draw through the terminal base.
Verify that the current draw does not exceed 10 A.
Methods of wiring the terminal base units are shown in Figure 4.
Figure 4 - Terminal Base Wiring
Install the Module Installation of the FLEX I/O module consists of:
• Mounting the terminal base unit
• Installing the Thermocouple, RTD, and mV module into the terminal base unit
• Installing the connecting wiring to the terminal base unit
ATTENTION:
• Total current draw through the terminal base unit is limited to 10 A. Separate
power connections may be necessary.
• Do not daisychain power or ground from the terminal base unit to any AC or DC
digital module terminal base unit.
ATTENTION: Note the following considerations for each type of wiring
configuration:
• Daisychain – All modules must be analog or Thermocouple, RTD, and mV modules
for this configuration.
• Individual – Use this type of configuration for any "noisy" DC digital I/O modules in
your system.
• Combination – All modules that are powered by the same power supply must be
analog or Thermocouple, RTD, and mV modules for the combination type of
configuration.
Digital Input
Module
Analog
Module
Analog
Module
Analog
Module
Digital Output
Module
Digital Input
Module
TC/RTD/mV
Module
Analog
Module
TC/RTD/mV
Module
TC/RTD/mV
Module
TC/RTD/mV
Module
TC/RTD/mV
Module
Daisychain
Individual
Combination
24V DC
24V DC
24V DC
24V DC
24V DC
24V DC
Wiring when total current draw is less than 10 A
Wiring when total current draw is less than 10 A
Thermocouple, RTD, Millivolt wiring separate from digital wiring.
Total current draw through any base unit must not be greater than 10 A

Rockwell Automation Publication 1794-UM012D-EN-P - March 2023 13
Chapter 2 Install Your FLEX I/O Input Module
If you are installing your module into a terminal base unit that is already installed, proceed to the
section, Mount the FLEX I/O Module on the Terminal Base Unit on page 16.
Mount on a DIN Rail
Install the Terminal Base Unit
1. Remove the cover plug in the male connector of the unit to which you are connecting this
terminal base unit.
2. Make sure that the 16 pins in the male connector on the adjacent device are straight and in
line so that the mating connector on this terminal base unit mate correctly.
Verify that the female Flexbus connector is fully retracted into the base unit.
3. Position the terminal base at a slight angle and hooked over the top of the 35 x 7.5 mm DIN
rail (Allen-Bradley part number 199-DR1; 46277-3).
4. Slide the terminal base over tight against the adapter, or proceeding terminal base. Make
sure the hook on the terminal base slides under the edge of the adapter, or proceeding
terminal base, and the Flexbus connector is fully retracted.
5. Rotate the terminal base onto the DIN rail with the top of the rail hooked under the lip on the
rear of the terminal base.
Make sure that the female Flexbus connector does not strike any of the pins in the mating
connector.
ATTENTION: Do not remove or replace a terminal base unit when power is
applied. Interruption of the Flexbus can result in unintended operation or machine
motion.
1
2
3
4
6
7
7
8
90
2
+
2
+
2
+
2
+

14 Rockwell Automation Publication 1794-UM012D-EN-P - March 2023
Chapter 2 Install Your FLEX I/O Input Module
6. Press down on the terminal base unit to lock the terminal base on the DIN rail. If the terminal
base does not lock into place, use a screwdriver or similar device to open the locking tab,
press down on the terminal base until flush with the DIN rail and release the locking tab to
lock the base in place.
Gently push the Flexbus connector into the side of the adapter, or proceeding terminal base,
to complete the backplane connection.
For specific wiring information, see the installation instructions for the module you are
installing in this terminal base unit.
7. Repeat the above steps to install the next terminal base unit.
Ensure that the cover of the Flexbus connector on the last terminal base unit is in place.
Mount on a Panel or Wall
Installation of a FLEX system on a wall or panel consists of:
• Laying out the drilling points on the wall or panel
• Drilling the pilot holes for the mounting screws
• Mounting the adapter mounting plate
• Installing the terminal base units and securing them to the wall or panel
If you are installing your module into a terminal base unit that is already installed, proceed to Mount
the FLEX I/O Module on the Terminal Base Unit on page 16.
Use the mounting kit Catalog Number 1794-NM1 for panel or wall mounting.
2
+
2
+
2
+
2
+

Rockwell Automation Publication 1794-UM012D-EN-P - March 2023 15
Chapter 2 Install Your FLEX I/O Input Module
To install the mounting plate on a wall or panel:
1. Lay out the required points on the wall or panel as shown in Figure 5.
Figure 5 - Drilling Dimensions for Panel or Wall Mounting
2. Drill the necessary holes for the #6 self-tapping mounting screws.
3. Mount the mounting plate for the adapter using two #6 self-tapping screws – 18 screws are
included for mounting up to 8 modules and the adapter.
4. Hold the adapter at a slight angle and engage the top of the mounting plate in the indention
on the rear of the adapter.
5. Press the adapter down flush with the panel until the locking lever locks.
6. Position the terminal base unit up against the adapter and push the female bus connector
into the adapter.
7. Secure to the wall with two #6 self-tapping screws.
8. Repeat for each remaining terminal base unit.
(1.4)
35.5
017
2
3
4
6
7
8
9
2
+
2
+
1
2
3
4
Millimeters
(Inches)
Description Description
1 Mounting plate for adapter 3 Terminal base unit (not included)
2 #6 Self-tapping screws 4 Adapter (not included)
21 (0.83)
58.5
(2.3)
58.5
(2.3)
35.5
(1.4)
35.5
(1.4)
35.5
(1.4)
Millimeters
(Inches)
IMPORTANT Verify that the mounting plate is properly grounded to the panel. See
Industrial Automation Wiring and Grounding Guidelines, publication
1770-4.1.

16 Rockwell Automation Publication 1794-UM012D-EN-P - March 2023
Chapter 2 Install Your FLEX I/O Input Module
Mount the FLEX I/O Module on the Terminal Base Unit
The Thermocouple, RTD, and mV input module mounts on a 1794-TB3G or 1794-TB3GS terminal base
unit.
1. Rotate keyswitch (3) on terminal base unit (4) clockwise to position 3 as required for the
module.
Do not change the position of the keyswitch after wiring the terminal base unit.
2. Verify that the Flexbus connector (1) is pushed all the way to the left to connect with the
neighboring terminal base or adapter.
You cannot install the module unless the connector is fully extended.
3. Make sure the pins on the bottom of the module are straight so that they align properly with
the connector in the terminal base unit.
4. Position the module (8) with its alignment bar (7) aligned with the groove (6) on the terminal
base.
5. Press firmly and evenly to seat the module in the terminal base unit.
The module is seated when the latching mechanism is locked into the module.
6. Remove the cap plug and attach another terminal base unit to the right of this terminal base
unit if necessary.
Make sure that the last terminal base has the cap plug in place.
Description Description
1 Flexbus connector 5 Base unit
2 Latching mechanism 6 Alignment groove
3 Keyswitch 7 Alignment bar
4 Cap plug 8 Module
If you remove or insert the module while the backplane power is on, an electric
arc can occur. This could cause an explosion in hazardous location installations.
Be sure that power is removed or the area is nonhazardous before proceeding.
IMPORTANT The adapter is capable of addressing eight modules. Do not exceed a
maximum of eight terminal base units in your system.
1
2
3
4
5
6
7
8
Label here or under here

Rockwell Automation Publication 1794-UM012D-EN-P - March 2023 17
Chapter 2 Install Your FLEX I/O Input Module
Wiring Information Wire the module using a 1794-TB3G, 1794-TB3GK, or 1794-TB3GS terminal base unit.
Figure 6 - 1794-TB3G, 1794-TB3GK, and 1794-TB3GS Wiring
Connect Wiring to the FLEX I/O Module
Wire the Thermocouple, RTD, and mV module through the terminal base unit on which the module
mounts.
The module is compatible with the 1794-TB3G, 1794-TB3GK, and 1794-TB3GS terminal base units.
Connect Wiring Using a 1794-TB3G, 1794-TB3GK, or 1794-TB3GS Terminal Base Unit
1. Connect individual signal wiring to numbered terminals on 0…15 row (A), and 17…32 row (B),
on the terminal base unit as indicated in Table 2 on page 18. Use a Belden 8761 cable for mV
signal wiring, or the appropriate thermocouple wire for your thermocouples.
Signal wiring shields can be connected to terminals 16 or 33 on row B or terminals 40…45 on
row C.
2. Connect the +V DC power lead to terminal 34 on row C, terminals 34…51.
3. Connect the -V DC common (return-) to terminal 35 on row C, terminals 34…51.
4. If daisychaining power to the next terminal base unit, connect a jumper from terminal 50
(+V DC) on this base unit to the +V terminal on the next terminal base unit.
5. Connect a jumper from terminal 51 (-V DC common) to the -V DC common terminal on the
next terminal base unit.
6. If using cold junction compensators, make these connections as shown in the Table 3 on
page 18.
Identify RTD Wire Pairs
If the RTD wires are color-coded, the wires that are the same color are connected together. If the
wires are not color-coded, use an ohmmeter to determine the pairs.
How to Connect a 4-wire RTD
If the 4-wire RTD wires are all different colors, use an ohmmeter to determine which leads are
connected together. One of the leads in each pair is the compensation lead. Either lead of the pair
can be the compensation lead. Attach one pair to terminals L and -, and the other pair to + and H.
0123456789101112131415
16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33
34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51
A
B
C
A
B
C
1794-TB3G or 1794-TB3GK
1794-TB3GS
0...15
34...51
16...33
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
18 19 20 21 22 23 3324 25 26 27 28 29 30 31 3217
35 36 37 38 47 48 49 5034 51
16
39 40 41 42 43 44 45 46
Label placed at top of wiring area
34 and 50 = 24V DC
35 and 51 = Common
16 and 33 = Chassis
40…45 = Chassis ground
35 and 51 = Common
34 and 50 = 24V DC
16 and 33 = Chassis ground
40…45 = Chassis ground
ATTENTION: Do not daisychain power or ground from this terminal base unit to
any AC or DC digital module terminal base units.

18 Rockwell Automation Publication 1794-UM012D-EN-P - March 2023
Chapter 2 Install Your FLEX I/O Input Module
How to Connect a 3-wire RTD
If the 3-wire RTD wires are all different colors, use an ohmmeter to determine which leads are
connected together. Either lead of the pair can be the compensation lead. Attach one lead of the
pair to terminal L, and the other to +. Attach the single lead to -.
Table 2 - Wiring Connections for the FLEX I/O Input Module
Input Types Connect the Following:
HL+- Shield(1)
(1) Terminals 37, 38 and 39 and 46, 47 and 48 are for cold junction compensation, with 38 and 47 as chassis ground.
RTD – 2-wire 1 2
RTD – 3-wire 3 1 2
RTD – 4-wire 1a 2a 1 2
Thermocouple 1 2
Millivolt 1 2
Table 3 - CJC Sensor Connections
CJC Sensor
Input + Chassis Ground - CJC Tail(1)
(1) Terminals 37, 38, and 39, and 46, 47, and 48 are for cold junction compensation, with 38 and 47 as chassis ground. Connect the tail
of CJC1 to terminal 5 and CJC2 to terminal 12 if channels 0…3 or 0…7 are configured for thermocouples. Connect the tail of CJC1 to
terminal 22 and CJC2 to 29 if channels 4…7 are configured for thermocouples.
CJC1 C-37 C-38 C-39 A-5 (B-22)
CJC2 C-46 C-47 C-48 A-12 (B-29)
Table 4 - Terminal Base Unit Wiring Connections
RTD or TC Channel
1794-TB3G, 1794-TB3GK, and 1794-TB3GS Terminal Base Units(1)
(1) Terminals 37, 38, and 39, and 46, 47 and 48 are for cold junction compensation. Terminals 16, 33 and 40…45 are chassis ground.
Connect the tail of CJC1 to terminal 5 and CJC2 to 12 if channels 0…3 or 0…7 are thermocouples. Connect the tail of CJC1 to terminal
22 and CJC2 to 29 only if channels 4…7 are used.
High Signal
Terminal (H)
Low Signal
Terminal (L)
RTD Source
Current (+)
Signal
Return (-)
0A-1A-2A-0A-3
1A-5A-6A-4A-7
2 A-9 A-10 A-8 A-11
3 A-13 A-14 A-12 A-15
4 B-18 B-19 B-17 B-20
5 B-22 B-23 B-21 B-24
6 B-26 B-27 B-25 B-28
7 B-30 B-31 B-29 B-32
+24V DC Power 34 and 50
24V DC Common 35 and 51
IMPORTANT • Disconnecting and reconnecting RTDs, Thermocouples, or CJCs with power
applied temporarily disturbs the channel steady state data. Allow 2 minutes
for settling time after finishing connections.
• If using RTD isolators, use 2- or 4-wire configurations only, and add digital
filtering to the inputs.
1
2
1
3
2
1
1a
2
2a
1
2
1
2
2-wire
3-wire
4-wire
Thermocouple
RTD
Millivolt
+
-
mV

Rockwell Automation Publication 1794-UM012D-EN-P - March 2023 19
Chapter 2 Install Your FLEX I/O Input Module
Figure 7 - 2-, 3-, and 4-wire RTD and Thermocouple Wiring to a 1794-TB3G Terminal Base Unit
Figure 8 - Millivolt Wiring to a 1794-TB3G Terminal Base Unit
17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32
33
01 2 34567 8910 11 12 13 14 15
16
1234567891011121314150
35 36 37 38 39 40 41 42 43 44 45 46
48
49 50 5134
1794-TB3G
0...15
34...51
16...33
A
B
C
4-wire RTD channel 3
2-wire RTD channel 1
3-wire RTD channel 2
+
-
CJC
Thermocouple channel 4
1
2
2
1
1
3
2
1
1a
2a
2
47
ATTENTION: Keep exposed area of inner conductor as short as possible.
17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33
01234
5678
910
11 12 13 14 15
16
1234567891011121314150
35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 5134
Millivolt
source Millivolt
source
Millivolt
source
Millivolt
source
+-
+-
+-
+-
0...15
34...51
16...33
A
B
C

20 Rockwell Automation Publication 1794-UM012D-EN-P - March 2023
Chapter 2 Install Your FLEX I/O Input Module
Notes: