PLCs, Power Supplies & Others

Precision Measurement Overview

The Yokogawa AMM22C operates as a dedicated millivolt input multiplexer for the CENTUM CS and VP series systems. This module handles low-level analog signals from thermocouples, RTDs, and other mV-generating sensors. It provides high amplification and noise rejection for accurate temperature measurements. Process plants use this module for reliable thermal process monitoring.

Technical Specifications

The AMM22C measures 128 mm in height and 33 mm in width. Its compact design fits standard Yokogawa I/O rack configurations. The module weighs approximately 0.25 kilograms. It draws 430 mA from the +5V DC and 50 mA from the ±15V DC supplies.

Low-Level Signal Amplification

This module specializes in amplifying millivolt signals with minimal drift. A precision instrumentation amplifier provides the first stage of signal conditioning. The programmable gain settings range from 10 to 1000 for optimal scaling. This amplification allows accurate measurement of thermocouple and RTD outputs. The module achieves 120 dB of line frequency noise rejection. This rejection eliminates 50/60 Hz interference from industrial power sources.

Channel Architecture and Multiplexing

The Yokogawa AMM22C handles sixteen single-ended or eight differential input channels. Differential mode provides better common-mode noise immunity for low-level signals. A dedicated cold junction sensor compensates for thermocouple reference errors. Two multiplexer ICs switch channels with minimal thermal offset. Each channel completes a measurement cycle within 90 microseconds. A 47 μF tantalum capacitor filters supply noise for stable amplification.

Connectivity and System Integration

Installing the AMM22C requires one slot in the Yokogawa I/O rack. The module connects to thermocouple or RTD wiring via the 50-pin ribbon cable. A green LED confirms power and a yellow LED indicates active channel scanning. The module interfaces with the field control unit via the backplane bus. It operates reliably between 0°C and 50°C ambient temperatures. Using shielded thermocouple extension wire preserves signal integrity.

Reliability and Calibration

The Yokogawa AMM22C maintains measurement accuracy with factory-stored calibration data. The module performs automatic zero calibration on each channel. Regular verification against a millivolt calibrator ensures ongoing precision. The solid-state design eliminates mechanical failures for extended service life.

Details