The Yokogawa AMM21 Thermocouple Input Multiplexer Module is a multi-channel temperature input module designed for Yokogawa CENTUM CS and CENTUM VP Distributed Control Systems (DCS). The module acquires multiple thermocouple signals through multiplexing technology, allowing numerous temperature measurement points to be connected to a single analog acquisition circuit while maintaining high measurement accuracy and system reliability. It is intended for industrial process temperature monitoring in applications such as furnaces, boilers, reactors, heat exchangers, and process vessels. The AMM21 is one of Yokogawa’s 16-point terminal-type thermocouple input multiplexer modules for RIO systems.

Contents

• 1. Product Overview
• 2. Main Features
• 3. Typical Applications
• 4. Installation Preparation
• 5. Module Installation
• 6. Thermocouple Wiring
• 7. Module Configuration
• 8. Commissioning Procedure
• 9. Functional Verification
• 10. Preventive Maintenance
• 11. Practical Installation Case
• 12. Frequently Asked Questions

Product Overview

The AMM21 scans multiple thermocouple channels sequentially and converts temperature measurements into digital process values for the Yokogawa controller. It supports various industrial thermocouple types and provides reliable temperature acquisition for distributed process control applications.

Main Features

• Thermocouple input multiplexer module
• Supports multiple temperature measurement channels
• Compatible with Yokogawa CENTUM CS and CENTUM VP
• Supports standard industrial thermocouple types
• High measurement accuracy
• Built-in multiplexed channel scanning
• Diagnostic monitoring capability
• Designed for continuous industrial operation

Typical Applications

• Distributed Control Systems (DCS)
• Boiler temperature monitoring
• Furnace temperature measurement
• Reactor temperature control
• Heat exchanger monitoring
• Petrochemical plants
• Power generation facilities
• Steel manufacturing
• Chemical processing plants
• Water treatment systems

Installation Preparation

• Verify the AMM21 module model.
• Review system wiring drawings.
• Confirm thermocouple type for each channel.
• Inspect thermocouple extension cables.
• Follow ESD protection procedures.

Module Installation

1. Power down the controller if required.
2. Insert the AMM21 into the designated I/O slot.
3. Secure the retaining mechanism.
4. Connect thermocouple wiring.
5. Verify terminal tightness.
6. Restore controller power.

Thermocouple Wiring

• Verify thermocouple polarity.
• Use matching thermocouple extension wire.
• Avoid unnecessary junctions.
• Separate thermocouple cables from power wiring.
• Verify cable shielding and grounding.
• Minimize electrical interference sources.

Module Configuration

• Select thermocouple type for each channel.
• Configure engineering units.
• Assign measurement ranges.
• Configure alarm limits.
• Verify channel assignments.
• Download controller configuration.

Commissioning Procedure

VERIFY MODULE INSTALLATION
CHECK THERMOCOUPLE WIRING
VERIFY SENSOR POLARITY
CONFIGURE CHANNEL TYPES
CHECK TEMPERATURE VALUES
VERIFY DIAGNOSTICS
TEST ALARMS
CONFIRM NORMAL OPERATION

Functional Verification

• Verify all temperature channels operate correctly.
• Compare readings with calibrated instruments.
• Confirm alarm operation.
• Review diagnostic information.
• Monitor temperature stability.

Preventive Maintenance

• Inspect thermocouple wiring periodically.
• Verify terminal tightness.
• Inspect extension cable condition.
• Review module diagnostics.
• Verify sensor calibration during scheduled maintenance.

Practical Installation Case

During the commissioning of a refinery furnace control system, an AMM21 module was installed to acquire temperature measurements from multiple Type K thermocouples installed throughout the combustion chamber.

Following configuration and commissioning:

• All temperature channels operated normally.
• Measured values agreed with portable calibration equipment.
• Temperature alarms responded correctly.
• The DCS maintained stable temperature monitoring during continuous production.

Frequently Asked Questions

What is the function of the AMM21?

The AMM21 acquires multiple thermocouple temperature signals through multiplexed scanning and transfers accurate temperature measurements to the Yokogawa control system.

Which thermocouple types are supported?

The module supports standard industrial thermocouple types configured on a per-channel basis, including common types such as K, J, T, E, R, S, B, and N, depending on the system configuration.

What should be verified after installation?

Verify module installation, thermocouple wiring, polarity, channel configuration, measured temperatures, diagnostic status, alarm functions, and controller communication before placing the system into normal operation.

Summary

Proper installation of the Yokogawa AMM21 Thermocouple Input Multiplexer Module ensures accurate multi-channel temperature acquisition for Yokogawa CENTUM Distributed Control Systems. Correct thermocouple wiring, proper sensor selection, systematic commissioning, and routine preventive maintenance maximize measurement accuracy, reliability, and long-term industrial process performance.