Rockwell Automation 1794-IT8, D17946.5.7 User Manual

Allen-Bradley

Thermocouple/ Millivolt Input

User

Module

(Cat. No. 1794-IT8)

Manual

Important User Information

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.



The information below summarizes the changes to the company-wide templates since the last release.

New Information

Updated Information

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.

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1794-6.5.7 – April 1997

soc–ii Summary of Changes

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Overview of Flex I/O and your Thermocouple/mV Module

How to Install Your Thermocouple/mV Input Module

Chapter 1

Chapter Objectives The FLEX I/O System How

FLEX I/O Analog Modules Communicate with Programmable

Controllers

Typical

Communication Between an Adapter and a Module Features Chapter Summary

of your Modules

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Chapter 2

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Before Y European

Power Requirements

Installing Connecting

Module Chapter Summary

ou Install Y

Union Directive Compliance EMC Directive Low V

oltage Directive

Wiring

the T

the Module

Wiring for the Thermocouple/mV Module

Example

erminal Base Unit

Example

emperature T

Indicators

our Input Module

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erminal Base Units (1794-TB2 and -TB3 shown)

of Millivolt Input Wiring to a 1794-TB3 3-wire Thermocouple Wiring to a 1794-TB3T

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erminal Base Unit

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1–1 1–1

1–1 1–2 1–3 1–3

2–1 2–1 2–1 2–1 2–2 2–2 2–3 2–4 2–5

2–7 2–7

2–8 2–8

Module Programming

Chapter 3

Chapter Objectives Block

ransfer Programming

Sample

Chapter Summary

programs for FLEX I/O Analog Modules PLC-3 Programming PLC-5 Programming PLC-2 Programming

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3–1 3–1 3–2 3–2 3–3 3–4 3–4

Table of Contentsii

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

Chapter 4

Chapter Objectives Configuring Y Range Input

Scaling

Hardware

Throughput Reading Data From Y Mapping

Thermocouple/mV

Thermocouple/mV Input Module (1794-IT8) Read

Thermocouple/mV

Word/Bit Chapter Summary

our Thermocouple/mV Module

Selection

First Notch Filter

Data for the Analog Modules

Input Module

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in Normal Mode

our Module

Input Module (1794-IT8) Image T

Input Module (1794-IT8) W

Descriptions for the 1794-IT8 Thermocouple/mV

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Chapter 5

Chapter Objectives About DeviceNet Manager Polled I/O Structure

Adapter System Mapping

Thermocouple/mV

Defaults

Input Status W

Throughput

Data into the Image T

Thermocouple/mV Input Module (1794-IT8) Read Thermocouple/mV Word/Bit

Input Module

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ord

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able

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Input Module (1794-IT8) Image T

Input Module (1794-IT8) W

Descriptions for the 1794-IT8 Thermocouple/mV

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able Mapping

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rite

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able Mapping

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rite

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4–1 4–1 4–2 4–2 4–3 4–3 4–4 4–4 4–4 4–4 4–5

4–5 4–7

5–1 5–1 5–1 5–2 5–3 5–3 5–3 5–3 5–4

5–4 5–7

Calibrating Your Module

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Chapter 6

Chapter Objective General Tools Removing

Manually

Information

and Equipment

Lead Wire or Thermocouple Extension Wire Resistance

Method

1 6–2

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Method

2 6–3

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Calibrating your Thermocouple/mV Input Module

Flow

Chart for Calibration Procedure Calibration Wiring Read/Write W Offset Gain

Setups

Connections for the Thermocouple Module

Calibration

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ords for Calibration

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6–1 6–1 6–2 6–2

6–4 6–5 6–6 6–6 6–7 6–7 6–8

Table of Contents iii

Specifications

Calibrating Y

Software (Cat. No. 1787-MGR) Offset Gain

our Thermocouple/mV Module using DeviceNetManager

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Calibration

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Appendix A

Specifications Derating Curve

Resolution Curves for Thermocouples Type

B Thermocouple

Type

E Thermocouple

Type

C Thermocouple Type J Thermocouple Type

K Thermocouple Type

R Thermocouple Type

S Thermocouple Type

T Thermocouple Type

N Thermocouple Worst Case Accuracy for the Thermocouple/mV Module Error

Due to Open Circuit Current Through Loop Resistance Worst

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Case Repeatability for the Thermocouple/mV Input Module

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6–9 6–9

6–1

A–1 A–2 A–3 A–3 A–3 A–4 A–4 A–5 A–5 A–6 A–6 A–7 A–7 A–8 A–8

1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Thermocouple Restrictions (Extracted from NBS Monograph 125 (IPTS–68))

Appendix B

General

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

(Platinum – 30% Rhodium vs Platinum – 6% Rhodium) T

Thermocouples

E (Nickel–Chromium vs Copper–Nickel <Constantan*>) Type

Thermocouple J (Iron vs Copper–Nickel <Constantan*>) T K (Nickel–Chromium vs Nickel–Aluminum) T R

(Platinum–13% Rhodium vs Platinum) and

S (Platinum–10% Rhodium vs Platinum) T T (Copper vs Copper–Nickel <Constantan*>) T

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ype Thermocouple

ype Thermocouples

ype Thermocouple

ype

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. .

B–1 B–1 B–2

B–2 B–4

B–5 B–5

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Table of Contentsiv

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Using This Manual

Preface

Preface Objectives

Audience

Vocabulary

What This Manual Contains

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:

• DeviceNetManager

• Microsoft Windows

Software, cat. no. 1787-MGR

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

3 Module Programming

6 Calibrating Your Module

Appendix

A Specifications

B Thermocouple Restrictions Extracted from NBS Monograph 125 (IPTS–68)

Overview of Flex I/O and Your Thermocouple/mV Module

How to Install Your Thermocouple/mV Input Module

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

Describes features, capabilities, and hardware components.

Installation and connecting wiring

Block transfer programming and programming examples

Describes block transfer write and block transfer read configurations, including complete bit/word descriptions.

Describes communication over the I/O backplane between the module and the adapter, and how data is mapped into the image table.

Lists the tools needed, and the methods used to calibrate the thermocouple input module

Module specifications, derating curve, resolution curves for thermocouples, worst case accuracy and error due to open circuit current.

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1794-6.5.7 – April 1997

Using This ManualP–2

Catalog

Conventions

For Additional Information

Number

1787-MGR DeviceNetManager Software User Manual 1787-6.5.3

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

We use these conventions in this manual:

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

For additional information on FLEX I/O systems and modules, refer to the following documents:

Publications

Description

Industrial Automation Wiring and Grounding Guidelines 1770-4.1

Installation

Instructions

User

Manual

Summary

This preface gave you information on how to use this manual efficiently. The next chapter introduces you to the remote I/O adapter module.

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1794-6.5.7 – April 1997

Chapter

Overview of FLEX I/O and your Thermocouple/mV Module

Chapter Objectives

The FLEX I/O System

Adapter/Power Supply Terminal Base I/O Module

In this chapter, we tell you:

• what the FLEX I/O system is and what it contains

• how FLEX I/O modules communicate with programmable

controllers

• the features of your thermocouple module

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 I/O system contains the following components shown below:

How FLEX I/O Analog Modules Communicate with Programmable Controllers

20125

• adapter/power supply – powers the internal logic for as many as

eight I/O modules

• terminal base – contains a terminal strip to terminate wiring for

thermocouple or millivolt inputs.

• I/O module – contains the bus interface and circuitry needed to

perform specific functions related to your application

FLEX I/O thermocouple/mV modules are block transfer modules that interface analog signals with any Allen-Bradley programmable controllers that have block transfer capability. Block transfer programming moves input or output data words between the module’s memory and a designated area in the processor data table. Block transfer programming also moves configuration words from the processor data table to module memory.

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Overview of FLEX I/O and your Thermocouple/mV Module 1–2

The adapter/power supply transfers data to the module (block transfer write) and from the module (block transfer read) using BTW and BTR instructions in your ladder diagram program. These instructions let the adapter obtain input or output values and status from the module, and let you establish the module’s mode of operation. The illustration describes the communication process.

Typical Communication Between an Adapter and a Module

ADAPTER

ACTIVE FAULT

Allen-Bradley

LOCAL FAULT

The adapter transfers your configuration data to the module using a BTW.

Flexbus

POWER SUPPLY

RIO ADAPTER

1794-ASB

24VDC

Your ladder program instructs the adapter to perform a BTR of the values and stores them in a data table.

The adapter and module determine 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 written over by the transfer of new data in a subsequent transfer.

INPUT

+– +–

External devices transmit analog signals to the module.

Allen-Bradley

THERMOCOUPLE

INPUT 8 CHANNEL

INPUT 2 INPUT 4 INPUT 6INPUT 1 INPUT 3 INPUT 5 INPUT 7

+–+–+– +–+–+–

The module converts analog signals into binary format and stores these values until the adapter requests their transfer.

1794–IT8

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Your ladder program performs BTWs to the module only when you power it up, or any time you wish to reconfigure the module.

1794-6.5.7

Overview of FLEX I/O and your Thermocouple/mV Module 1–3

Features of your Modules

The module label identifies the keyswitch position, wiring and module type. A removable label provides space for writing individual designations per your application.

1794-IT8

Module Type

Allen-Bradley

INPUT

+– +–

THERMOCOUPLE

INPUT 2 INPUT 4 INPUT 6INPUT 1 INPUT 3 INPUT 5 INPUT 7

+– +– +– +–+–+–

INPUT 8 CHANNEL

Input Designators

1794–IT8

Removable Label

Keyswitch

Position Indicator (#3)

Power On Indicator

The thermocouple/mV module comes with 2 cold junction compensators. These are designed to mount in designated positions on the temperature terminal base unit (cat. no. 1794-TB3T). Refer to chapter 2 for installation instructions for the cold junction compensator assemblies.

Chapter Summary

In this chapter, you learned about the FLEX I/O system and the thermocouple module, and how they communicate with programmable controllers.

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Overview of FLEX I/O and your Thermocouple/mV Module 1–4

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Chapter

How to Install Your Thermocouple/mV Input Module

In this chapter, we tell you:

• how to install your module

• how to set the module keyswitch

• how to wire the terminal base

• about the indicators

Before You Install Your Input Module

European Union Directive Compliance

Before installing your thermocouple/mV module in the I/O chassis:

You need to: As described under:

Calculate the power requirements of all modules in each chassis.

Position the keyswitch on the terminal base Installing the Module, page 2–4

ATTENTION: The Thermocouple module does not receive power from the backplane. +24V dc power

If this product has the CE mark it is approved for installation within the European Union and EEA regions. It has been designed and tested to meet the following directives.

EMC Directive

This product is tested to meet Council Directive 89/336/EEC Electromagnetic Compatibility (EMC) and the following standards, in whole or in part, documented in a technical construction file:

• EN 50081-2EMC – Generic Emission Standard, Part 2 –

Industrial Environment

• EN 50082-2EMC – Generic Immunity Standard, Part 2 –

Industrial Environment

must be applied to your module before installation. If power is not applied, the module position will appear to the adapter as an empty slot in your chassis.

Power Requirements, page 2-2

This product is intended for use in an industrial environment.

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2–2

How to Install Your Thermocouple/mV Input Module

Low Voltage Directive

This product is tested to meet Council Directive 73/23/EEC Low Voltage, by applying the safety requirements of EN 61131–2 Programmable Controllers, Part 2 – Equipment Requirements and Tests.

For specific information required by EN 61131-2, see the appropriate sections in this publication, as well as the following Allen-Bradley publications:

• Industrial Automation Wiring and Grounding Guidelines For

Noise Immunity, publication 1770-4.1

• Guidelines for Handling Lithium Batteries, publication AG-5.4

• Automation Systems Catalog, publication B111

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 10A.

ATTENTION: Total current draw through the terminal base unit is limited to 10A. Separate power

connections may be necessary.

ATTENTION: Do not daisy chain power or ground from the thermocouple terminal base unit to any ac or dc discrete module terminal base unit.

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1794-6.5.7

How to Install Your Thermocouple/mV Input Module

Methods of wiring the terminal base units are shown in the illustration below.

Wiring the Terminal Base Units (1794-TB2 and -TB3 shown)

ATTENTION: Do not daisy chain power or

ground from the thermocouple terminal base unit to any ac or dc discrete module terminal base unit.

2–3

Daisy-chaining

Individual

24V dc or 120V ac

24V dc

Thermocouple

or Analog Module

24V dc

Thermocouple module wiring separate from discrete wiring.

Note: All modules must be analog modules for this configuration.

Wiring

when total current draw is less than 10A

Discrete

Module

Thermocouple

or Analog Module

Thermocouple

or Analog Module

Thermocouple

or Analog Module

Discrete

Module

Note: Use this configuration if using any “noisy” dc discrete I/O modules in your system.

Thermocouple

or Analog Module

Discrete

Module

Combination

24V dc 24V dc

iring when total current draw is greater than 10A

Discrete

Module

Note: All modules powered by the same power supply must be analog modules for this configuration.

otal current draw through any base unit must not be greater than 10A

Thermocouple

or Analog Module

Thermocouple

or Analog Module

Thermocouple

or Analog Module

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2–4

How to Install Your Thermocouple/mV Input Module

Installing the Module

The thermocouple/mV module mounts on a 1794-TB2, -TB3 or

-TB3T terminal base unit. Important: You must use a 1794-TB3T terminal base unit if you

are using the thermocouple/mV module for thermocouple inputs. You can use the 1794-TB2 or

-TB3 terminal base for millivolt inputs only.

1. Rotate the keyswitch (1) on the terminal base unit (2) clockwise

to position 3 as required for the thermocouple/mV module.

2. Make certain the flexbus connector (3) is pushed all the way to

the left to connect with the neighboring terminal base/adapter.

You cannot install the module unless the connector is fully extended.

ATTENTION: Remove field-side power before removing or inserting the module. This module is

designed so you can remove and insert it under backplane power. When you remove or insert a

module with field-side power applied, an electrical arc may occur. An electrical arc can cause personal injury or property damage by:

• sending an erroneous signal to your system’s field

devices causing unintended machine motion

• causing an explosion in a hazardous environment

Repeated electrical arcing causes excessive wear to contacts on both the module and its mating connector. Worn contacts may create electrical resistance.

3. Before installing the module, check to make sure that the pins on

the bottom of the module are straight so they will align properly with the female connector in the base unit.

4. Position the module (4) with its alignment bar (5) 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 (7) is locked into the module.

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6. Repeat the above steps to install the next module in its terminal

base unit.

1794-6.5.7

How to Install Your Thermocouple/mV Input Module

2–5

Connecting Wiring for the Thermocouple/mV Module

1794-TB2

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

COM COM

V = 24V dc COM

= 24V dc common

These

and 1794-TB3

terminals on 1794-TB3 only

Thermocouple/mV module wiring is made through the terminal base unit on which the module mounts. The module comes with 2 cold junction compensators for use when using the thermocouple module in the thermocouple mode.

Compatible terminal base unit are:

Module 1794-TB2 1794-TB3 1794-TB3T

1794-IT8 Yes

The

1794-TB3T terminal base unit contains connections for cold junction

compensation for use with thermocouple modules.

For millivolt inputs only

Yes

1794-TB3T

–15

16–33

34–51

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

C N0 C N1 C N2 C CN3 C N4 C N5 C N6 C N7

VCJC CJCV

Where:

V = 24V dc C = 24V dc common CJC = cold junction compensation

Yes

N = additional input

Connecting Wiring using a 1794-TB2, -TB3 and -TB3T Terminal Base Units

= chassis ground

1. Connect the individual signal wiring to numbered terminals on the 0–15 row (A) on the terminal base unit. Connect the high side (+) to the even numbered terminals, and the low side (–) to the odd numbered terminals. See Table 2.A.

2. Connect shield return to the associated terminal on row B, as shown in Table 2.A.

• On 1794-TB2 and -TB3 bases only: terminate shields to the

associated shield return terminals on row (B).

• On 1794-TB3T bases only: terminate shields to terminals 39

to 46 on row C.

3. Connect +24V dc to terminal 34 on the 34-51 row (C), and 24V common to terminal 16 on the B row.

Important: To reduce susceptibility to noise, power analog modules

and discrete modules from separate power supplies.

ATTENTION: Do not daisy chain power or ground from the thermocouple terminal base unit to any ac or

dc discrete module terminal base unit.

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Thermocouple

inals 36, 37, 38 and 47, 48, 49 are cold junction

How to Install Your Thermocouple/mV Input Module

Cold Junction Compensator Pt.No. 969424-01

ATTENTION: The Thermocouple/mV module does not receive power from the backplane. +24V dc power

must be applied to your module before installation. If power is not applied, the module position will appear to the adapter as an empty slot in your chassis.

4. On 1794-TB3T terminal base units: Connect the cold junction

compensation (CJC) wiring to terminals 36, 37 and 38 for inputs 0 through 3, and terminals 47, 48 and 49 for inputs 4 through 7.

Connect the tail of the cold junction compensator to any of the associated thermocouple input terminals: 0 through 7 for CJC connected to 36, 37 and 38; or 8 through 15 for CJC connected to 47, 48 and 49. The tail of the cold junction compensator shares

a terminal with an input.

5. If daisy chaining the +24V dc power to the next base unit,

connect a jumper from terminal 51 on this base unit to terminal 34 on the next base unit.

1234567891011121314150

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33

1 51

0 –15 16–33 34–51

1794-TB2

1234567891011121314150

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33

35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51

0 16–33 34–51

1794-TB3, -TB3T

–15

A B C

Table 2.A

Wiring

connections for the 1794-IT8 Thermocouple Input Module

Shield

Return

Channel

1794-TB2, -TB3 Terminal Base Units 1794-TB3T Terminal Base Unit

High Signal Terminal (+)

Low Signal

Terminal (–)

Shield

Return

High Signal Terminal (+)

Low Signal

Terminal (–)

0 0 1 17 0 1 39 1 2 3 19 2 3 40 2 4 5 21 4 5 41 3 6 7 23 6 7 42 4 8 9 25 8 9 43 5 10 11 27 10 11 44 6 12 13 29 12 13 45 7 14 15 31 14 15 46

24V dc Common 16 thru 33 16, 17, 19, 21, 23, 25, 27, 29, 31 and 33

+24V dc power 1794-TB2 – 34 and 51; 1794-TB3 – 34 thru 51 34, 35, 50 and 51

Terminals

39 to 46 are chassis ground.

erm

compensator terminals.

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How to Install Your Thermocouple/mV Input Module

ATTENTION: The thermocouple/mV modules do not receive power from the backplane. +24V dc power

must be applied to your module before operation. If power is not applied, the module position will appear to the adapter as an empty slot in your chassis. If the adapter does not recognize your module after installation is completed, cycle power to the adapter.

ATTENTION: Total current draw through the terminal base unit is limited to 10A. Separate power

connections to the terminal base unit may be necessary.

Example of Millivolt Input Wiring to a 1794-TB3 Terminal Base Unit

12 34567891011121314150

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33

35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51

2–7

–15 16–33 34–51

1794-TB3

Millivolt Source

–

Millivolt input Channel 1

Channel 0 (Terminals 0, 1 and 17)

Example of 3-wire Thermocouple Wiring to a 1794-TB3T Temperature Terminal Base Unit

12 34567891011121314150

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33

35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51

CJC CJC

–

1794-TB3T

0 16–33 34–51

Cold

Junction Compensator

Allen-Bradley PN 969424–01

(2 supplied with module)

–15

Channel 0 (Terminals 0, 1 and 39)

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Module Indicators

The thermocouple/mV module has one status indicator that is on when power is applied to the module. This indicator has 3 different states:

Allen-Bradley

THERMOCOUPLE INPUT 8 CHANNEL

INPUT

+– +–

A = Status Indicator – indicates diagnostic results and configuration status B = Insertable label for writing individual input designations

Color State Meaning

Red On Indicates a critical fault (diagnostic failure, etc.)

Blinking Indicates a noncritical fault (such as open sensor, input out of range, etc.)

Green On Module is configured and fully operational

Blinking Module is functional but not configured Off Module not powered

INPUT 2 INPUT 4 INPUT 6INPUT 1 INPUT 3 INPUT 5 INPUT 7

+– +–+– +–+–+–

1794–IT8

Chapter Summary

In this chapter, you learned how to install your thermocouple/mV module in an existing programmable controller system and how to wire to the terminal base units.

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Chapter

Chapter Objectives

Block Transfer Programming

In this chapter, we tell you about:

• block transfer programming

• sample programs for the PLC-3 and PLC-5 processors

Your thermocouple/mV module communicates with the processor through bidirectional block transfers. This is the sequential operation of both read and write block transfer instructions.

A configuration block transfer write (BTW) is initiated when the thermocouple module is first powered up, and subsequently only when the programmer wants to enable or disable features of the module. The configuration BTW sets the bits which enable the programmable features of the module, such as scaling, alarms, ranges, etc. Block transfer reads are performed to retrieve information from the module.

Block transfer read (BTR) programming moves status and data from the module to the processor’s data table. The processor user program initiates the request to transfer data from the module to the processor. The transferred words contain module status, channel status and input data from the module.

ATTENTION: If the thermocouple/mV module is not powered up before the remote I/O adapter, the

The following sample programs are minimum programs; all rungs and conditioning must be included in your application program. You can disable BTRs, or add interlocks to prevent writes if desired. Do not eliminate any storage bits or interlocks included in the sample programs. If interlocks are removed, the program may not work properly.

Your program should monitor status bits and block transfer read activity.

adapter will not recognize the module. Make certain that the thermocouple/mV module is installed and powered before or simultaneously with the remote I/O adapter. If the adapter does not establish communication with the module, cycle power to the adapter.

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