AMM42T 2-wire Transmitter Input Multiplexer Module Yokogawa

Hardware Specifications

4-20 mA DCS Instrumentation Loop Characteristics

The AMM42T is designed for direct handling of two-wire transmitter current loops in Yokogawa process control systems. The module provides transmitter excitation through a 23.5 to 24.5 V DC supply output and measures 4-20 mA DC input signals through its multiplexing circuitry.

The input resistance is configured as 250 ohm for standard transmitter loop operation and can be changed to 70 ohm when connected with a barrier device. The module does not provide electrical isolation between field signals and the system side or between individual channels.

For process instrumentation applications, loop engineering must consider transmitter current consumption, barrier impedance, and grounding arrangement. Yokogawa analog input architectures commonly interface with conventional 4-20 mA instrumentation loops and may be integrated with HART-enabled field devices when compatible signal conditioning modules are applied.

Frequently Asked Questions

Q: Does the AMM42T provide channel-to-channel isolation?
A: No. The AMM42T specification states that there is no isolation between channels or between the field side and system side.

Q: What transmitter power supply range is provided by the AMM42T?
A: The module provides a transmitter power supply output of 23.5 to 24.5 V DC with an output power limit of 60 mA or less.

Q: Can the input resistance be modified for barrier connection?
A: Yes. The standard input resistance is 250 ohm and can be changed to 70 ohm when connected to a barrier.

Field Installation Guidelines

• Install the AMM42T in the designated Yokogawa I/O module nest position.
• Secure the module connection to the I/O module nest terminals using M4 screws as specified by the installation design.
• Route 4-20 mA signal wiring separately from high-voltage power cables and switching circuits to reduce electrical interference.
• Maintain correct transmitter loop polarity during field wiring.
• Apply appropriate shield grounding practices according to the overall DCS installation standard.
• Verify transmitter loop current, barrier impedance, and power supply loading before commissioning.
• Confirm that the absence of channel-to-channel isolation is considered in the field wiring and grounding design.