Yokogawa AMM42T 2-Wire Transmitter Input Multiplexer Module

The Yokogawa AMM42T is a specialized 2-wire transmitter input multiplexer module designed for the CENTUM CS and CENTUM VP distributed control systems. It addresses the critical need for high-density analog signal acquisition by allowing a single input channel to sequentially monitor multiple 4 to 20 mA DC loops. This module is essential for process industries where space is limited and loop density is high, offering a streamlined solution for connecting standard 2-wire transmitters while providing the necessary loop power (24 V DC) directly from the module.

Technical Specifications

The AMM42T is engineered to handle standard analog current loops with precise multiplexing capabilities.

Model Code Interpretation

For Yokogawa modules, the suffix code is critical as it defines the physical interface (connector vs. terminal) and the specific channel configuration.

Part Number: AMM42T

AMM42-AXX

• A (Suffix -T): Indicates the Terminal Type.

• -T: Denotes that this module features screw terminals for direct field wiring. This allows for easy connection of transmitter wires without the need for specialized mating connectors or cable assemblies.

• Note: This is distinct from the "-C" (Connector) version, which would require a specific cable harness.

Installation and Wiring Guidelines

To ensure reliable operation and accurate current loop measurement, follow these installation practices:

1. Carrier Compatibility: The AMM42T is designed to mount into specific I/O carrier boxes (such as the AMN34). Ensure the module is fully inserted into the slot and the locking mechanism is engaged to secure the connection to the backplane.

2. Loop Power Configuration: The module provides a 24 V DC supply (23.5 to 24.5 V DC) to power the 2-wire transmitters. Ensure that the total current draw of the connected transmitters does not exceed the output power limit of 60 mA.

3. Input Resistance Setting:

• The standard input resistance is 250 Ω, which converts the 4-20 mA current signal into a 1-5 V voltage signal for the system.

• If you are connecting the module to an intrinsic safety barrier, you may need to change the resistance setting to 70 Ω to ensure proper loop operation.

4. Grounding and Isolation: Note that there is no isolation between the system and the field, nor between channels. This means all connected transmitters must share a common ground reference. Failure to observe this can result in ground loops or signal errors.

Frequently Asked Questions (FAQ)

Q: What is the primary function of the AMM42T?A: The AMM42T acts as a multiplexer for 2-wire transmitters. It allows the control system to monitor multiple 4-20 mA loops using a single analog input channel, significantly reducing the hardware footprint.

Q: Does the AMM42T provide power to the transmitters?A: Yes, the module supplies 24 V DC (nominal) to power the connected 2-wire transmitters, eliminating the need for external power supplies for the field devices.

Q: Is the AMM42T compatible with CENTUM VP?A: Yes, the AMM42T is fully compatible with both CENTUM CS and the newer CENTUM VP systems, allowing for seamless integration and hardware upgrades.

Q: Can I use this module for isolated inputs?A: No. The technical specifications state there is no isolation between the system and field or between channels. If channel-to-channel isolation is required, you should consider using individual input modules or a different multiplexer architecture.