Rockwell Automation 1762-IT4 User Manual

MicroLogix™ 1200 Thermocouple/mV Input Module

(Catalog Number 1762-IT4)

User 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 these products 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. In no event will Allen-Bradley be responsible or liable for indirect or consequential damage resulting from the use or application of these products.

Any illustrations, charts, sample programs, and layout examples shown in this publication are intended solely for purposes of 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 that 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 part, without written permission of Rockwell Automation, is prohibited.

Throughout this publication, notes may be used to make you aware of safety considerations. The following annotations and their accompanying statements help you to identify a potential hazard, avoid a potential hazard, and recognize the consequences of a potential hazard:

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.

IMPORTANT

Identifies information that is critical for successful application and understanding of the product.

Overview

Preface

Who Should Use This Manual . . . . . . . . . . . . . . . . . . . . . . P-1

How to Use This Manual. . . . . . . . . . . . . . . . . . . . . . . . . . P-1

Manual Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . P-1

Related Documentation . . . . . . . . . . . . . . . . . . . . . . . . P-2

Conventions Used in This Manual . . . . . . . . . . . . . . . . . . . P-2

Rockwell Automation Support . . . . . . . . . . . . . . . . . . . . . . P-3

Local Product Support . . . . . . . . . . . . . . . . . . . . . . . . . P-3

Technical Product Assistance . . . . . . . . . . . . . . . . . . . . P-3

Your Questions or Comments on the Manual . . . . . . . . P-3

Chapter 1

General Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1

Thermocouple/mV Inputs and Ranges . . . . . . . . . . . . . 1-1

Data Formats . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2

Filter Frequencies . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2

Hardware Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2

General Diagnostic Features. . . . . . . . . . . . . . . . . . . . . 1-4

System Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-4

System Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-4

Module Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5

Module Field Calibration . . . . . . . . . . . . . . . . . . . . . . . 1-6

Installation and Wiring

Chapter 2

Compliance to European Union Directives . . . . . . . . . . . . . 2-1

EMC Directive . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1

Low Voltage Directive . . . . . . . . . . . . . . . . . . . . . . . . . 2-2

Power Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-2

General Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-2

Hazardous Location Considerations . . . . . . . . . . . . . . . 2-3

Prevent Electrostatic Discharge . . . . . . . . . . . . . . . . . . . 2-3

Remove Power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-4

Selecting a Location . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-4

Mounting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-5

Minimum Spacing . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-5

DIN Rail Mounting. . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-5

Panel Mounting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-6

System Assembly. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-7

Field Wiring Connections . . . . . . . . . . . . . . . . . . . . . . . . . 2-7

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Table of Contents ii

Module Data, Status, and Channel Configuration

Wiring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-9

Terminal Block Layout . . . . . . . . . . . . . . . . . . . . . . . . . 2-9

Labeling the Terminals. . . . . . . . . . . . . . . . . . . . . . . . . 2-9

Wiring the Finger-Safe Terminal Block . . . . . . . . . . . . . 2-10

Wire Size and Terminal Screw Torque . . . . . . . . . . . . . 2-11

Terminal Door Label . . . . . . . . . . . . . . . . . . . . . . . . . . 2-11

Wiring the Module. . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-11

Wiring Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-13

Cold Junction Compensation . . . . . . . . . . . . . . . . . . . . . . . 2-13

Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-14

Chapter 3

Module Memory Map . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1

Accessing Input Image File Data . . . . . . . . . . . . . . . . . . . . 3-1

Input Data File . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-2

Input Data Values . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-2

General Status Bits (S0 to S4) . . . . . . . . . . . . . . . . . . . . 3-2

Open-Circuit Flag Bits (OC0 to OC4) . . . . . . . . . . . . . . 3-3

Over-Range Flag Bits (O0 to O4) . . . . . . . . . . . . . . . . . 3-3

Under-Range Flag Bits (U0 to U4). . . . . . . . . . . . . . . . . 3-3

Configuring Channels . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-4

Configuration Data File . . . . . . . . . . . . . . . . . . . . . . . . 3-4

Channel Configuration . . . . . . . . . . . . . . . . . . . . . . . . . 3-4

Enabling or Disabling a Channel (Bit 15) . . . . . . . . . . . 3-6

Selecting Data Formats (Bits 14 through 12) . . . . . . . . . 3-6

Selecting Input Type (Bits 11 through 8). . . . . . . . . . . . 3-8

Selecting Temperature Units (Bit 7) . . . . . . . . . . . . . . . 3-9

Determining Open-Circuit Response (Bits 6 and 5) . . . . 3-9

Selecting Input Filter Frequency (Bits 2 through 0) . . . . 3-10

Selecting Enable/Disable Cyclic Calibration

(Word 4, Bit 0) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-14

Determining Effective Resolution and Range . . . . . . . . . . . 3-14

Determining Module Update Time. . . . . . . . . . . . . . . . . . . 3-33

Effects of Autocalibration on Module Update Time . . . . 3-34

Calculating Module Update Time . . . . . . . . . . . . . . . . . 3-35

Impact of Autocalibration on Module Startup

During Mode Change. . . . . . . . . . . . . . . . . . . . . . . . . . 3-37

Diagnostics and Troubleshooting

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Chapter 4

Safety Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1

Indicator Lights . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1

Stand Clear of Equipment. . . . . . . . . . . . . . . . . . . . . . . 4-2

Program Alteration. . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-2

Safety Circuits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-2

Specifications

Table of Contents iii

Module Operation vs. Channel Operation . . . . . . . . . . . . . 4-2

Power-up Diagnostics . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-3

Channel Diagnostics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-3

Invalid Channel Configuration Detection. . . . . . . . . . . . 4-3

Over- or Under-Range Detection . . . . . . . . . . . . . . . . . 4-3

Open-Circuit Detection . . . . . . . . . . . . . . . . . . . . . . . . 4-4

Non-critical vs. Critical Module Errors . . . . . . . . . . . . . . . . 4-4

Module Error Definition Table . . . . . . . . . . . . . . . . . . . . . . 4-4

Module Error Field. . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-4

Extended Error Information Field . . . . . . . . . . . . . . . . . 4-5

Error Codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-6

Contacting Rockwell Automation . . . . . . . . . . . . . . . . . . . . 4-7

Appendix A

General Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-1

Input Specifications. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-2

Repeatability at 25°C (77°F) . . . . . . . . . . . . . . . . . . . . . . . A-3

Accuracy. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-4

Accuracy Versus Thermocouple Temperature and Filter

Frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-5

Two’s Complement Binary Numbers

Thermocouple Descriptions

Using Thermocouple Junctions

Appendix B

Positive Decimal Values . . . . . . . . . . . . . . . . . . . . . . . . . . B-1

Negative Decimal Values. . . . . . . . . . . . . . . . . . . . . . . . . . B-2

Appendix C

International Temperature Scale of 1990. . . . . . . . . . . . . . . C-1

Type B Thermocouples . . . . . . . . . . . . . . . . . . . . . . . . . . . C-1

Type E Thermocouples . . . . . . . . . . . . . . . . . . . . . . . . . . . C-3

Type J Thermocouples . . . . . . . . . . . . . . . . . . . . . . . . . . . C-5

Type K Thermocouples. . . . . . . . . . . . . . . . . . . . . . . . . . . C-7

Type N Thermocouples. . . . . . . . . . . . . . . . . . . . . . . . . . . C-9

Type R Thermocouples . . . . . . . . . . . . . . . . . . . . . . . . . . C-11

Type S Thermocouples . . . . . . . . . . . . . . . . . . . . . . . . . . C-12

Type T Thermocouples . . . . . . . . . . . . . . . . . . . . . . . . . . C-14

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-17

Appendix D

Using a Grounded Junction Thermocouple . . . . . . . . . . . . D-1

Using an Ungrounded (Isolated) Junction Thermocouple . . D-2

Using an Exposed Junction Thermocouple. . . . . . . . . . . . . D-3

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Table of Contents iv

Module Configuration Using MicroLogix 1200 and RSLogix 500

Appendix E

Module Addressing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . E-1

1762-IT4 Configuration File . . . . . . . . . . . . . . . . . . . . . E-2

Configuration Using RSLogix 500 Version 5.50 or Higher . . E-2

Generic Extra Data Configuration . . . . . . . . . . . . . . . . . E-6

Configuration Using RSLogix 500 Version 5.2 or Lower. . . . E-7

Glossary

Index

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Preface

Read this preface to familiarize yourself with the rest of the manual. This preface covers the following topics:

• who should use this manual

• how to use this manual

• related publications

• conventions used in this manual

• Rockwell Automation support

Who Should Use This Manual

How to Use This Manual

Use this manual if you are responsible for designing, installing, programming, or troubleshooting control systems that use Allen-Bradley MicroLogix™ 1200.

As much as possible, we organized this manual to explain, in a task-by-task manner, how to install, configure, program, operate and troubleshoot a control system using the 1762-IT4.

Manual Contents

If you want... See

An overview of the thermocouple/mV input module Chapter 1 Installation and wiring guidelines Chapter 2 Module addressing, configuration and status information Chapter 3 Information on module diagnostics and troubleshooting Chapter 4 Specifications for the input module Appendix A Information on understanding two’s complement binary numbers Appendix B Thermocouple descriptions Appendix C Information on using the different types of thermocouple junctions Appendix D An example of configuration using RSLogix 500 Appendix E

1 Publication 1762-UM002A-EN-P - July 2002

Preface 2

Conventions Used in This Manual

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The following conventions are used throughout this manual:

• Bulleted lists (like this one) provide information not procedural

steps.

• Numbered lists provide sequential steps or hierarchical

information.

• Italic type is used for emphasis.

Preface 3

Rockwell Automation Support

Rockwell Automation offers support services worldwide, with over 75 Sales/Support Offices, 512 authorized distributors and 260 authorized Systems Integrators located throughout the United States alone, plus Rockwell Automation representatives in every major country in the world.

Local Product Support

Contact your local Rockwell Automation representative for:

• sales and order support

• product technical training

• warranty support

• support service agreement

Technical Product Assistance

If you need to contact Rockwell Automation for technical assistance, please review the information in Chapter 4, Diagnostics and Troubleshooting first. Then call your local Rockwell Automation representative.

Your Questions or Comments on the Manual

If you find a problem with this manual, please notify us. If you have any suggestions for how this manual could be made more useful to you, please contact us at the address below:

Rockwell Automation Automation Control and Information Group Technical Communication, Dept. A602V P.O. Box 2086 Milwaukee, WI 53201-2086

Publication 1762-UM002A-EN-P - July 2002

Preface 4

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Chapter

Overview

This chapter describes the 1762-IT4 Thermocouple/mV Input Module and explains how the module reads thermocouple or millivolt analog input data. Included is information about:

• the module’s hardware and diagnostic features

• system and module operation

• calibration

General Description

The thermocouple/mV input module supports thermocouple and millivolt signal measurement. It digitally converts and stores thermocouple and/or millivolt analog data from any combination of up to four thermocouple or millivolt analog sensors. Each input channel is individually configurable via software for a specific input device, data format and filter frequency, and provides open-circuit, over-range and under-range detection and indication.

Thermocouple/mV Inputs and Ranges

The table below defines thermocouple types and their associated full-scale temperature ranges. The second table lists the millivolt analog input signal ranges that each channel will support. To determine the practical temperature range your thermocouple supports, see the specifications in Appendix A.

Thermocouple Type °C Temperature Range °F Temperature Range

J -210 to +1200°C -346 to +2192°F K -270 to +1370°C -454 to +2498°F T -270 to +400°C -454 to +752°F E -270 to +1000°C -454 to +1832°F R 0 to +1768°C +32 to +3214°F S 0 to +1768°C +32 to +3214°F

B +300 to +1820°C +572 to +3308°F N -210 to +1300°C -346 to +2372°F C 0 to +2315°C +32 to + 4199°F

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1-2 Overview

Millivolt Input Type Range

± 50 mV -50 to +50 mV ± 100 mV -100 to +100 mV

Data Formats

The data can be configured on board each module as:

• engineering units x 1

• engineering units x 10

• scaled-for-PID

• percent of full-scale

• raw/proportional data

Filter Frequencies

The module uses a digital filter that provides high frequency noise rejection for the input signals. The filter is programmable, allowing you to select from six different filter frequencies for each channel:

• 10 Hz

• 50 Hz

• 60 Hz

• 250 Hz

• 500 Hz

• 1000 Hz

Hardware Features

Channels are wired as differential inputs. A cold junction compensation (CJC) sensor is attached to the terminal block to enable accurate readings from each channel. The sensor compensates for offset voltages introduced into the input signal as a result of the cold-junction where the thermocouple wires are connected to the module.

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Overview 1-3

The illustration below shows the module’s hardware features.

Item Description

1a upper panel mounting tab 1b lower panel mounting tab 2 power diagnostic LED 3 module door with terminal identification label 5 bus connector cover 6 flat ribbon cable with bus connector (female) 7 terminal block 8 DIN rail latch 9 pull loop

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1-4 Overview

General Diagnostic Features

The module contains a diagnostic LED that helps you identify the source of problems that may occur during power-up or during normal channel operation. The LED indicates both status and power. Power-up and channel diagnostics are explained in Chapter 4,

Diagnostics and Troubleshooting.

System Overview

The modules communicate to the controller through the bus interface. The modules also receive 5 and 24V dc power through the bus interface.

System Operation

At power-up, the module performs a check of its internal circuits, memory, and basic functions. During this time, the module status LED remains off. If no faults are found during power-up diagnostics, the module status LED is turned on.

After power-up checks are complete, the module waits for valid channel configuration data. If an invalid configuration is detected, the module generates a configuration error. Once a channel is properly configured and enabled, it continuously converts the thermocouple or millivolt input to a value within the range selected for that channel.

Each time a channel is read by the input module, that data value is tested by the module for an over-range, under-range, open-circuit, or “input data not valid” condition. If such a condition is detected, a unique bit is set in the channel status word. The channel status word is described in Input Data File on page 3-2.

Publication 1762-UM002A-EN-P - July 2002

Using the module image table, the controller reads the two’s complement binary converted thermocouple or millivolt data from the module. This typically occurs at the end of the program scan or when commanded by the control program. If the controller and the module determine that the data transfer has been made without error, the data is used in the control program.

Overview 1-5

Module Operation

When the module receives a differential input from an analog device, the module’s circuitry multiplexes the input into an A/D converter. The converter reads the signal and converts it as required for the type of input. The module also continuously samples the CJC sensor and compensates for temperature changes at the terminal block cold junction, between the thermocouple wire and the input channel. See the block diagram below.

4 Thermocouple/mV

Inputs

CJC Sensor

A/D

Converter

AIN + AIN -

Multiplexer

Terminal Block

AIN + AIN -

MCU

+15V

+5V

A-GND

-15V

Optocoupler

Supply

Isolated Power

1762 Bus ASIC

MicroLogix 1200 Controller

+24V

S-GND

Each channel can receive input signals from a thermocouple or millivolt analog input device, depending upon how you configured the channel.

When configured for thermocouple input types, the module converts the analog input voltages into cold-junction compensated and linearized digital temperature readings. The module uses the National Institute of Standards and Technology (NIST) ITS-90 standard for linearization for all thermocouple types (J, K, T, E, R, S, B, N, C).

When configured for millivolt inputs, the module converts the analog values directly into digital counts.

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1-6 Overview

Module Field Calibration

The module provides autocalibration, which compensates for offset and gain drift of the A/D converter caused by a temperature change within the module. An internal, high-precision, low drift voltage and system ground reference is used for this purpose. The input module performs autocalibration when a channel is initially enabled. In addition, you can program the module to perform a calibration cycle once every 5 minutes. See Selecting Enable/Disable Cyclic Calibration (Word 4, Bit 0) on page 3-14 for information on configuring the module to perform periodic autocalibration.

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Installation and Wiring

This chapter tells you how to:

• determine the power requirements for the modules

• avoid electrostatic damage

• install the module

• wire the module’s terminal block

• wire input devices

Chapter

Compliance to European Union Directives

This product is approved for installation within the European Union and EEA regions. It has been designed and tested to meet the following directives.

EMC Directive

The 1762-IT4 module 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 50081-2

EMC – Generic Emission Standard, Part 2 - Industrial Environment

• EN 50082-2

EMC – Generic Immunity Standard, Part 2 - Industrial Environment

This product is intended for use in an industrial environment.

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2-2 Installation and Wiring

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 EN61131-2, 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

• Automation Systems Catalog, publication B113

Power Requirements

General Considerations

The module receives power through the bus interface from the +5V dc/+24V dc system power supply. The maximum current drawn by the module is shown in the table below.

Module Current Draw at 5V dc at 24V dc

40 mA 50 mA

1762 I/O is suitable for use in an industrial environment when installed in accordance with these instructions. Specifically, this equipment is intended for use in clean, dry environments (Pollution

degree 2

(1)

) and to circuits not exceeding Over Voltage Category II

(IEC 60664-1).

(3)

(2)

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(1) Pollution Degree 2 is an environment where, normally, only non-conductive pollution occurs except that

occasionally a temporary conductivity caused by condensation shall be expected.

(2) Over Voltage Category II is the load level section of the electrical distribution system. At this level transient

voltages are controlled and do not exceed the impulse voltage capability of the product’s insulation.

(3) Pollution Degree 2 and Over Voltage Category II are International Electrotechnical Commission (IEC)

designations.

Installation and Wiring 2-3

Hazardous Location Considerations

This equipment is suitable for use in Class I, Division 2, Groups A, B, C, D or non-hazardous locations only. The following WARNING statement applies to use in hazardous locations.

WARNING

EXPLOSION HAZARD

• Substitution of components may impair suitability

for Class I, Division 2.

• Do no replace components or disconnect

equipment unless power has been switched off or the area is known to be non-hazardous.

• Do not connect or disconnect components unless

power has been switched off or the area is known to be non-hazardous.

• This product must be installed within an

enclosure.

• All wiring must comply with N.E.C. article

501-4(b).

Prevent Electrostatic Discharge

ATTENTION

Electrostatic discharge can damage integrated circuits or semiconductors if you touch bus connector pins. Follow these guidelines when you handle the module:

• Touch a grounded object to discharge static

potential.

• Wear an approved wrist-strap grounding device.

• Do not touch the bus connector or connector

pins.

• Do not touch circuit components inside the

module.

• If available, use a static-safe work station.

• When not in use, keep the module in its

static-shield box.

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2-4 Installation and Wiring

Remove Power

ATTENTION

Remove power before removing or installing this module. When you remove or install a module with 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

• causing an explosion in a hazardous

• causing permanent damage to the module’s

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

Selecting a Location

field devices, causing unintended machine motion

environment

circuitry

Reducing Noise

Most applications require installation in an industrial enclosure to reduce the effects of electrical interference. Analog inputs are highly susceptible to electrical noise. Electrical noise coupled to the analog inputs will reduce the performance (accuracy) of the module.

Group your modules to minimize adverse effects from radiated electrical noise and heat. Consider the following conditions when selecting a location for the analog module. Position the module:

• away from sources of electrical noise such as hard-contact

switches, relays, and AC motor drives

• away from modules which generate significant radiated heat.

Refer to the module’s heat dissipation specification.

In addition, route shielded, twisted-pair analog input wiring away from any high voltage I/O wiring.

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Mounting

ATTENTION

Do not remove protective debris strip until after the module and all other equipment near the module is mounted and wiring is complete. Once wiring is complete and the module is free of debris, carefully remove protective debris strip. Failure to remove strip before operating can cause overheating.

Minimum Spacing

Installation and Wiring 2-5

Top

Maintain spacing from enclosure walls, wireways, adjacent equipment, etc. Allow

50.8 mm (2 in.) of space on all sides for adequate ventilation, as shown:

TIP

ATTENTION

1762 expansion I/O may be mounted horizontally only.

During panel or DIN rail mounting of all devices, be sure that all debris (metal chips, wire strands, etc.) is kept from falling into the module. Debris that falls into the module could cause damage when power is applied to the module.

MicroLogix

Side Side

1200

1762 I/O

Bottom

1762 I/O

DIN Rail Mounting

The module can be mounted using the following DIN rails: 35 x 7.5 mm (EN 50 022 - 35 x 7.5) or 35 x 15 mm (EN 50 022 - 35 x 15).

Before mounting the module on a DIN rail, close the DIN rail latch. Press the DIN rail mounting area of the module against the DIN rail. The latch will momentarily open and lock into place.

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2-6 Installation and Wiring

Use DIN rail end anchors (Allen-Bradley part number 1492-EA35 or 1492-EAH35) for environments with vibration or shock concerns.

End Anchor

TIP

For environments with extreme vibration and shock concerns, use the panel mounting method described below, instead of DIN rail mounting.

Panel Mounting

Use the dimensional template shown below to mount the module. The preferred mounting method is to use two M4 or #8 panhead screws per module. M3.5 or #6 panhead screws may also be used, but a washer may be needed to ensure a good ground contact. Mounting screws are required on every module.

For more than 2 modules: (number of modules - 1) x 40.4 mm (1.59 in.)

14.5 (0.57)

40.4 (1.59)

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NOTE: Hole spacing tolerance: ±0.4 mm (0.016 in.).

100 (3.94)

90 (3.54)

MicroLogix 1200

40.4 (1.59)

Expansion I/O

MicroLogix 1200

Expansion I/O

MicroLogix 1200

Expansion I/O

Installation and Wiring 2-7

System Assembly

The expansion I/O module is attached to the controller or another I/O module by means of a ribbon cable after mounting as shown below.

TIP

ATTENTION

Use the pull loop on the connector to disconnect modules. Do not pull on the ribbon cable.

EXPLOSION HAZARD

Field Wiring Connections

• In Class I, Division 2 applications, the bus

connector must be fully seated and the bus connector cover must be snapped in place.

• In Class I, Division 2 applications, all modules

must be mounted in direct contact with each other as shown on page 2-5. If DIN rail mounting is used, an end stop must be installed ahead of the controller and after the last 1762 I/O module.

General

• Power and input wiring must be in accordance with Class 1,

Division 2 wiring methods, Article 501-4(b) of the National Electric Code, NFPA 70, and in accordance with the authority having jurisdiction.

• Channels are isolated from one another by ±10 Vdc maximum.

• If multiple power supplies are used with analog millivolt inputs,

the power supply commons must be connected.

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2-8 Installation and Wiring

Terminal Block

• Do not tamper with or remove the CJC sensor on the terminal

block. Removal of the sensor reduces accuracy.

• For millivolt sensors, use Belden 8761 shielded, twisted-pair

wire (or equivalent) to ensure proper operation and high immunity to electrical noise.

• For a thermocouple, use the shielded, twisted-pair

thermocouple extension lead wires specified by the thermocouple manufacturer. Using the incorrect type of thermocouple extension wire or not following the correct polarity will cause invalid readings.

• To ensures optimum accuracy, limit overall cable impedance by

keeping a cable as short as possible. Locate the module as close to input devices as the application permits.

Grounding

ATTENTION

• This product is intended to be mounted to a well-grounded

mounting surface such as a metal panel. Additional grounding connections from the module’s mounting tabs or DIN rail (if used) are not required unless the mounting surface cannot be grounded.

• Under normal conditions, the drain wire (shield) should be

connected to the metal mounting panel (earth ground). Keep shield connection to earth ground as short as possible.

• Ground the shield drain wire at one end only. The typical

location is as follows.

– For grounded thermocouples or millivolt sensors, this is at the

sensor end.

– For insulated/ungrounded thermocouples, this is at the

module end. Contact your sensor manufacturer for additional details.

The possibility exists that a grounded or exposed thermocouple can become shorted to a potential greater than that of the thermocouple itself. Due to possible shock hazard, take care when wiring grounded or exposed thermocouples. See Appendix D, Using Thermocouple Junctions.

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Installation and Wiring 2-9

• If it is necessary to connect the shield drain wire at the module

end, connect it to earth ground using a panel or DIN rail mounting screw.

• Refer to Industrial Automation Wiring and Grounding

Guidelines, Allen-Bradley publication 1770-4.1, for additional

information.

Noise Prevention

• Route field wiring away from any other wiring and as far as

possible from sources of electrical noise, such as motors, transformers, contactors, and ac devices. As a general rule, allow at least 15.2 cm (6 in.) of separation for every 120V of power.

• Routing field wiring in a grounded conduit can reduce electrical

noise.

• If field wiring must cross ac or power cables, ensure that they

cross at right angles.

Wiring

• To limit the pickup of electrical noise, keep thermocouple and

millivolt signal wires as far as possible from power and load lines.

• If noise persists for a device, try grounding the opposite end of

the cable shield. (You can only ground one end at a time.)

Terminal Block Layout

CJC CJC

IN2 +

IN2 -

IN3 +

IN3 -

IN 0 + IN 0 IN1 + IN1 -

Labeling the Terminals

A write-on label is provided with the module. Mark the identification of each terminal with permanent ink, and slide the label back into the door.

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2-10 Installation and Wiring

Wiring the Finger-Safe Terminal Block

ATTENTION

Be careful when stripping wires. Wire fragments that fall into a module could cause damage when power is applied. Once wiring is complete, ensure the module is free of all metal fragments.

When wiring the terminal block, keep the finger-safe cover in place.

1. Route the wire under the terminal pressure plate. You can use

the stripped end of the wire or a spade lug. The terminals will accept a 6.35 mm (0.25 in.) spade lug.

2. Tighten the terminal screw making sure the pressure plate

secures the wire. Recommended torque when tightening terminal screws is 0.904 Nm (8 in-lbs).

3. After wiring is complete, remove the debris shield.

TIP

If you need to remove the finger-safe cover, insert a screw driver into one of the square wiring holes and gently pry the cover off. If you wire the terminal block with the finger-safe cover removed, you will not be able to put it back on the terminal block because the wires will be in the way.

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Installation and Wiring 2-11

Wire Size and Terminal Screw Torque

Each terminal accepts up to two wires with the following restrictions:

Wire Type Wire Size Terminal Screw Torque

Solid Cu-90°C (194°F) #14 to #22 AWG 0.904 Nm (8 in-lbs) Stranded Cu-90°C (194°F) #16 to #22 AWG 0.904 Nm (8 in-lbs)

Terminal Door Label

A removable, write-on label is provided with the module. Remove the label from the door, mark your unique identification of each terminal with permanent ink, and slide the label back into the door. Your markings (ID tag) will be visible when the module door is closed.

Wiring the Module

ATTENTION

To prevent shock hazard, care should be taken when wiring the module to analog signal sources. Before wiring any module, disconnect power from the system power supply and from any other source to the module.

After the module is properly installed, follow the wiring procedure on page 2-12, using the proper thermocouple extension cable, or Belden 8761 for non-thermocouple applications.

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2-12 Installation and Wiring

cable

signal wire

drain wire

To wire your module follow these steps.

1. At each end of the cable, strip some casing to expose the

individual wires.

2. Trim the signal wires to 2-inch (5 cm) lengths. Strip about 3/16

inch (5 mm) of insulation away to expose the end of the wire.

ATTENTION

Be careful when stripping wires. Wire fragments that fall into a module could cause damage at power up.

foil shield

signal wire

Cut foil shield and drain wire

signal wire

3. At one end of the cable, twist the drain wire and foil shield

together, bend them away from the cable, and apply shrink wrap. Then earth ground at the preferred location based on the type of sensor you are using. See Grounding on page 2-8.

4. At the other end of the cable, cut the drain wire and foil shield

back to the cable and apply shrink wrap.

5. Connect the signal wires to the terminal block. Connect the

other end of the cable to the analog input device.

6. Repeat steps 1 through 5 for each channel on the module.

TIP

See Appendix D Using Thermocouple Junctions for additional information on wiring grounded, ungrounded, and exposed thermocouple types.

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Wiring Diagram

Installation and Wiring 2-13

ungrounded thermocouple

CJC sensor

CJC+

CJC -

IN 2+

IN 2-

IN 3+

IN 3-

TIP

IMPORTANT

IN 0+ IN 0-

IN 1 + IN 1-

grounded thermocouple

within 10V dc

When using an ungrounded thermocouple, the shield must be connected to ground at the module end.

When using grounded and/or exposed thermocouples that are touching electrically conductive material, the ground potential between any two channels cannot exceed ±10V dc, or temperature readings will be inaccurate.

grounded thermocouple

Cold Junction Compensation

To obtain accurate readings from each of the channels, the temperature between the thermocouple wire and the input channel must be compensated for. A cold junction compensating thermistor has been integrated in the terminal block. The thermistor must remain installed to retain accuracy.

ATTENTION

If the thermistor assembly is accidentally removed, re-install it by connecting it across the pair of CJC terminals.

Do not remove or loosen the cold junction compensating thermistor assembly. This assembly is critical to ensure accurate thermocouple input readings at each channel. The module will operate in the thermocouple mode, but at reduced accuracy if the CJC sensor is removed. See Determining Open-Circuit Response (Bits 6 and 5) on page 3-9.

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2-14 Installation and Wiring

Calibration

The thermocouple module is initially calibrated at the factory. The module also has an autocalibration function.

When an autocalibration cycle takes place, the module’s multiplexer is set to system ground potential and an A/D reading is taken. The A/D converter then sets its internal input to the module’s precision voltage source, and another reading is taken. The A/D converter uses these numbers to compensate for system offset (zero) and gain (span) errors.

Autocalibration of a channel occurs whenever a channel is enabled. You can also program your module to perform cyclic calibration cycles, every five minutes. See Selecting Enable/Disable Cyclic Calibration (Word 4, Bit 0) on page 3-14.

To maintain optimal system accuracy, periodically perform an autocalibration cycle.

IMPORTANT

The module does not convert input data while the calibration cycle is in progress following a change in configuration. Module scan times are increased by up to 112 ms during cyclic autocalibration.

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