AMM25C | Yokogawa Thermocouple Multiplexer Module for CENTUM CS/VP

The Yokogawa AMM25C is a specialized mV input multiplexer module engineered for the CENTUM CS and CENTUM VP distributed control systems. It addresses the specific challenge of high-density temperature monitoring by supporting up to 15 thermocouple input channels within a single unit. By integrating a Reference Junction Compensation (RJC) interface, this module ensures precise temperature readings, compensating for ambient temperature fluctuations at the connection point. It is the ideal solution for process industries requiring reliable, isolated signal acquisition for thermocouples and low-voltage DC signals without the complexity of external conditioning hardware.

Technical Specifications

The AMM25C combines high-precision analog-to-digital conversion with robust isolation features suitable for industrial environments.

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: AMM25C

AMM25-AXX

• A (Suffix -C): Indicates the Connector Type.

• -C: Denotes that this module uses a connector interface (typically a 15-point connector) rather than a screw terminal block. This requires a specific mating connector or cable assembly (such as the KS1 cable) for field wiring.

• Note: This is distinct from the "T" (Terminal) version, which would have direct screw terminals.

Note: Always verify the physical interface (Connector vs. Terminal) before purchasing to ensure it matches your existing cabling or carrier setup.

Installation and Wiring Guidelines

To ensure accurate temperature measurement and system stability, follow these installation practices:

1. Carrier Compatibility: The AMM25C is designed to be installed in specific I/O carrier boxes (such as the AMN32). Ensure the module is fully inserted into the slot and the locking mechanism is engaged.

2. RJC Connection: This module features a specific Reference Junction Compensation (RJC) port. You must connect the RJC sensor (usually a thermistor or diode sensor provided with the system) to this port. This allows the module to measure the temperature at the cold junction and mathematically compensate the thermocouple reading for high accuracy.

3. Cable Connection: Since this is a connector type (-C), use the designated KS1 cable or mating connector. Ensure the cable is securely fastened to the module face to prevent signal interruption due to vibration.

4. Burnout Configuration: Configure the burnout detection direction (UP, DOWN, or OFF) via the system engineering software. This ensures that if a thermocouple wire breaks, the system registers a safe failure state rather than a random temperature reading.

5. Grounding: While the inputs are isolated, proper grounding of the control cabinet and the cable shield is recommended to minimize electromagnetic interference (EMI).

Frequently Asked Questions (FAQ)

Q: What is the function of the RJC port on the AMM25C?A: The RJC (Reference Junction Compensation) port connects to a sensor that measures the temperature at the module's terminal block. This is critical for thermocouple accuracy, as it compensates for the difference between the process temperature and the connection point temperature.

Q: How many channels does the AMM25C support?A: The AMM25C supports 15 input points, allowing for high-density monitoring of temperature or low-voltage signals in a single module slot.

Q: Can this module handle standard voltage inputs?A: Yes, in addition to thermocouples and mV signals, the AMM25C supports DC voltage inputs ranging from -10 V to +10 V, making it versatile for various analog signal types.

Q: Is the AMM25C compatible with CENTUM VP?A: Yes, it is fully compatible with both CENTUM CS and the newer CENTUM VP systems, facilitating seamless system upgrades and maintenance.