Allen-Bradley 1794-IT8 User manual

User
Manual
Thermocouple/
Millivolt Input
Module
(Cat. No. 1794-IT8)
Allen-Bradley

Because of the variety of uses for the products described in this
publication, those responsible for the application and use of this
control equipment must satisfy themselves that all necessary steps
have been taken to assure that each application and use meets all
performance and safety requirements, including any applicable laws,
regulations, codes and standards.
The illustrations, charts, sample programs and layout examples
shown in this guide are intended solely for example. Since there are
many variables and requirements associated with any particular
installation, Allen-Bradley does not assume responsibility or liability
(to include intellectual property liability) for actual use based upon
the examples shown in this publication.
Allen-Bradley publication SGI–1.1, “Safety Guidelines For The
Application, Installation and Maintenance of Solid State Control”
(available from your local Allen-Bradley office) describes some
important differences between solid-state equipment and
electromechanical devices which should be taken into consideration
when applying products such as those described in this publication.
Reproduction of the contents of this copyrighted publication, in
whole or in part, without written permission of Allen–Bradley
Company, Inc. is prohibited.
Throughout this manual we make notes to alert you to possible
injury to people or damage to equipment under specific
circumstances.
!ATTENTION: Identifies information about practices
or circumstances that can lead to personal injury or
death, property damage, or economic loss.
Attention helps you:
•identify a hazard
•avoid the hazard
•recognize the consequences
Important: Identifies information that is especially important for
successful application and understanding of the product.
Important: We recommend you frequently backup your application
programs on appropriate storage medium to avoid
possible data loss.
DeviceNet, DeviceNetManager, and RediSTATION are trademarks of Allen-Bradley Company, Inc.
PLC, PLC–2, PLC–3, and PLC–5 are registered trademarks of Allen-Bradley Company, Inc.
Windows is a trademark of Microsoft.
Microsoft is a registered trademark of Microsoft
IBM is a registered trademark of International Business Machines, Incorporated.
All other brand and product names are trademarks or registered trademarks of their respective companies.
Important User Information


Publication 1794-6.5.7 – April 1997

The information below summarizes the changes to the
company-wide templates since the last release.
The following new information has been added to this manual:
•the “L” type thermocouple selection has been added for use in
some European markets.
Calibration procedures have been revised to eliminate 1 method in
order to better control calibration results.
Change Bars
The areas in this manual which are different from previous editions
are marked with change bars (as shown to the right of this paragraph)
to indicate the addition of new or revised information.
New Information
Updated Information

soc–ii Summary of Changes
Publication 1794-6.5.7 – April 1997

Publication 1794-6.5.7
Chapter 1
Chapter Objectives 1–1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
The FLEX I/O System
1–1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
How
FLEX I/O Analog Modules Communicate with Programmable
Controllers 1–1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Typical
Communication Between an Adapter and a Module 1–2 . . .
Features
of your Modules 1–3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Chapter Summary
1–3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Chapter 2
2–1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Before Y
ou Install Y our Input Module 2–1 . . . . . . . . . . . . . . . . . . . . . . .
European
Union Directive Compliance 2–1 . . . . . . . . . . . . . . . . . . . . . .
EMC Directive
2–1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Low V
oltage Directive 2–2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Power Requirements
2–2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Wiring
the T erminal Base Units (1794-TB2 and -TB3 shown) 2–3 . .
Installing
the Module 2–4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Connecting
Wiring for the Thermocouple/mV Module 2–5 . . . . . . . . . . .
Example
of Millivolt Input Wiring to a 1794-TB3
T erminal Base Unit 2–7 . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Example
3-wire Thermocouple Wiring to a 1794-TB3T
T emperature T erminal Base Unit 2–7 . . . . . . . . . . . . . . . . . . .
Module
Indicators 2–8 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Chapter Summary
2–8 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Chapter 3
Chapter Objectives 3–1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Block
T ransfer Programming 3–1 . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Sample
programs for FLEX I/O Analog Modules 3–2 . . . . . . . . . . . . . . .
PLC-3 Programming
3–2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
PLC-5 Programming
3–3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
PLC-2 Programming
3–4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Chapter Summary
3–4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Overview of Flex I/O and
your Thermocouple/mV
Module
How to Install Your
Thermocouple/mV Input
Module
Module Programming
Table of Contents

Table of Contentsii
Publication 1794-6.5.7
Chapter 4
Chapter Objectives 4–1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
ConfiguringY
our Thermocouple/mV Module 4–1 . . . . . . . . . . . . . . . . .
Range
Selection 4–2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Input
Scaling 4–2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Hardware
First Notch Filter 4–3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Throughput
in Normal Mode 4–3 . . . . . . . . . . . . . . . . . . . . . . . . .
Reading Data From Y
our Module 4–4 . . . . . . . . . . . . . . . . . . . . . . . . .
Mapping
Data for the Analog Modules 4–4 . . . . . . . . . . . . . . . . . . . . . .
Thermocouple/mV
Input Module (1794-IT8) Image T able Mapping 4–4
Thermocouple/mV Input Module (1794-IT8) Read 4–4 . . . . . . . . . .
Thermocouple/mV
Input Module (1794-IT8) W rite 4–5 . . . . . . . . . .
Word/Bit
Descriptions for the 1794-IT8 Thermocouple/mV
Input Module 4–5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Chapter Summary
4–7 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Chapter 5
Chapter Objectives 5–1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
About DeviceNet Manager
5–1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Polled I/O Structure
5–1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Adapter
Input Status W ord 5–2 . . . . . . . . . . . . . . . . . . . . . . . . . . . .
System
Throughput 5–3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Mapping
Data into the Image T able 5–3 . . . . . . . . . . . . . . . . . . . . . . . .
Thermocouple/mV
Input Module (1794-IT8) Image T able Mapping 5–3
Thermocouple/mV Input Module (1794-IT8) Read 5–3 . . . . . . . . . .
Thermocouple/mV
Input Module (1794-IT8) W rite 5–4 . . . . . . . . . .
Word/Bit
Descriptions for the 1794-IT8 Thermocouple/mV
Input Module 5–4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Defaults
5–7 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Chapter 6
Chapter Objective 6–1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
General
Information 6–1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Tools
and Equipment 6–2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Removing
Lead Wire or Thermocouple Extension Wire Resistance 6–2 .
Method
1 6–2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Method
2 6–3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Manually
Calibrating your Thermocouple/mV Input Module 6–4 . . . . . . .
Flow
Chart for Calibration Procedure 6–5 . . . . . . . . . . . . . . . . . . . . .
Calibration
Setups 6–6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Wiring
Connections for the Thermocouple Module 6–6 . . . . . . . . . . .
Read/Write W
ords for Calibration 6–7 . . . . . . . . . . . . . . . . . . . . . . .
Offset
Calibration 6–7 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Gain
Calibration 6–8 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Writing Configuration to
and Reading Status from
your Module with a Remote
I/O Adapter
How Communication Takes
Place and I/O Image Table
Mapping with the
DeviceNet Adapter
Calibrating Your Module

Table of Contents iii
Publication 1794-6.5.7
CalibratingY our Thermocouple/mV Module using DeviceNetManager
Software (Cat. No. 1787-MGR) 6–9 . . . . . . . . . . . . . . . . . . . . . . . .
Offset
Calibration 6–9 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Gain
Calibration 6–1 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Appendix A
Specifications A–1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Derating Curve
A–2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Resolution Curves for Thermocouples
A–3 . . . . . . . . . . . . . . . . . . . .
Type
B Thermocouple A–3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Type
E Thermocouple A–3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Type
C Thermocouple A–4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Type J Thermocouple
A–4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Type
K Thermocouple A–5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Type
R Thermocouple A–5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Type
S Thermocouple A–6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Type
T Thermocouple A–6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Type
N Thermocouple A–7 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Worst Case Accuracy for the Thermocouple/mV Module
A–7 . . . . . . .
Error
Due to Open Circuit Current Through Loop Resistance A–8 . . . .
Worst
Case Repeatability for the Thermocouple/mV Input Module A–8
Appendix B
General B–1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
B
(Platinum – 30% Rhodium vs Platinum – 6% Rhodium) T ype
Thermocouples
B–1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
E (Nickel–Chromium vs Copper–Nickel <Constantan*>) Type
Thermocouple
B–2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
J (Iron vs Copper–Nickel <Constantan*>) T
ype Thermocouple B–2 . . .
K (Nickel–Chromium vs Nickel–Aluminum) T
ype Thermocouple B–4 . .
R
(Platinum–13% Rhodium vs Platinum) and
S (Platinum–10% Rhodium vs Platinum) T ype Thermocouples B–5
T (Copper vs Copper–Nickel <Constantan*>) T ype Thermocouple B–5
Specifications
Thermocouple Restrictions
(Extracted from NBS
Monograph 125 (IPTS–68))

Table of Contentsiv
Publication 1794-6.5.7

Preface
Publication 1794-6.5.7 – April 1997
Using This Manual
Read this preface to familiarize yourself with this manual and to
learn how to use it properly and efficiently.
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.
In addition, if you are using this module in a DeviceNet system, you
must be familiar with:
•DeviceNetManagerTM Software, cat. no. 1787-MGR
•Microsoft WindowsTM
In this manual, we refer to:
•the individual thermocouple/mV module as the “module.”
•the programmable controller as the “controller” or the
“processor.”
The contents of this manual are as follows:
Chapter Title What’s Covered
1Overview of Flex I/O and Your
Thermocouple/mV Module Describes features, capabilities, and hardware components.
2How to Install Your
Thermocouple/mV Input Module Installation and connecting wiring
3Module Programming Block transfer programming and programming
examples
4Writing Configuration to and Reading Status from Your Module with a
Remote I/O Adapter
Describes block transfer write and block transfer read
configurations, including complete bit/word descriptions.
5How Communication Takes Place and I/O Image Table Mapping with
the DeviceNet Adapter
Describes communication over the I/O backplane
between the module and the adapter, and how data is
mapped into the image table.
6Calibrating Your Module Lists the tools needed, and the methods used to
calibrate the thermocouple input module
Appendix
A Specifications Module specifications, derating curve, resolution curves for thermocouples, worst case accuracy and error due
to open circuit current.
BThermocouple Restrictions Extracted from NBS Monograph 125 (IPTS–68)
Preface Objectives
Audience
Vocabulary
What This Manual
Contains

Using This ManualP–2
Publication 1794-6.5.7 – April 1997
We use these conventions in this manual:
In this manual, we show: Like this:
that there is more information about a topic
in another chapter in this manual
that there is more information about the
topic in another manual More
For additional information on FLEX I/O systems and modules, refer
to the following documents:
Catalog
Descr pt on
Publications
Catalog
Number Description Installation
Instructions User Manual
1787-MGR DeviceNetManager Software User Manual 1787-6.5.3
Industrial Automation Wiring and Grounding Guidelines 1770-4.1
1794 1794 FLEX I/O Product Data 1794-2.1
1794-ADN DeviceNet Adapter 1794-5.14 1794-6.5.5
1794-ASB/C Remote I/O Adapter 1794-5.46 1794-6.5.9
This preface gave you information on how to use this manual
efficiently. The next chapter introduces you to the remote I/O
adapter module.
Conventions
For Additional Information
Summary