Yokogawa AMM42 2-Wire Transmitter Input Multiplexer Module

Hardware Specifications

4-20 mA Process Signal Interface Characteristics

The AMM42-S4 processes analog current inputs from 2-wire field transmitters and supplies loop excitation voltage to connected devices. The module handles transmitter signals within the 4-20 mA DC range and transfers measurement data to the Yokogawa control system with a 1 second update period per loop.

The input circuit provides a defined resistance path of 250 ohm for normal operation. When integrated with a safety barrier configuration, the input resistance can be modified to 70 ohm to match external interface requirements.

Frequently Asked Questions

Q: Does the AMM42-S4 provide channel-to-channel isolation?
A: No. The module specification states that signal isolation is not provided between channels or between the system side and field side.

Q: What type of field devices can be connected to the AMM42-S4?
A: The module is designed for 2-wire transmitters providing 4-20 mA DC analog signals, including typical process measurement transmitters.

Q: What power supply does the module provide to connected transmitters?
A: The module provides transmitter loop power at 23.5 to 24.5 VDC with an output power limit of 60 mA or less.

Field Installation Guidelines

• Install the module according to the Yokogawa DCS/FCS rack and cabinet installation requirements.
• Verify field wiring polarity before connecting 2-wire transmitter loops.
• Use shielded instrumentation cables where required by the site grounding standard.
• Connect cable shields according to the control system grounding design to reduce electrical noise interference.
• Separate analog signal wiring from high-voltage power cables and high-frequency switching circuits.
• Confirm transmitter loop current compatibility before commissioning the input channels.
• Ensure rack power loading remains within the specified 5.0 VDC backplane current consumption limit.