AMM21T Yokogawa Thermocouple Input Multiplexer Module

Hardware Specifications

Yokogawa DCS Temperature Signal Processing and CJC Function

The AMM21T integrates thermocouple input multiplexing with Yokogawa DCS signal acquisition functions. Therefore, the module scans multiple thermocouple channels and transfers measured temperature data through the CENTUM control system interface.

The module supports multiple standard thermocouple types and applies integrated cold junction compensation (CJC) to correct temperature measurement errors caused by terminal temperature variation. In addition, channel-to-system isolation reduces interference from field wiring conditions and improves signal separation within process control installations.

The AMM21T does not provide direct 4-20 mA HART loop communication because it is designed specifically for thermocouple millivolt signal processing. However, it operates within Yokogawa process control architectures where field temperature signals are collected, converted, and processed by higher-level DCS functions.

Frequently Asked Questions

Q: How many thermocouple input channels does the Yokogawa AMM21T support?
A: The AMM21T supports 16 thermocouple input channels for multiplexed temperature measurement applications.

Q: Does the AMM21T include cold junction compensation?
A: Yes. The module includes integrated cold junction compensation to correct thermocouple measurement variations caused by reference terminal temperature changes.

Q: Can the AMM21T directly accept 4-20 mA transmitter signals?
A: No. The AMM21T is designed for thermocouple inputs and does not function as a current input module for 4-20 mA signals.

Field Installation Guidelines

• Install the AMM21T according to Yokogawa CENTUM CS or CENTUM VP hardware configuration requirements.
• Verify module slot allocation before connecting field thermocouple wiring.
• Use thermocouple extension cables that match the connected thermocouple type to prevent measurement deviation.
• Maintain separation between thermocouple signal wiring and high-voltage power cables to reduce electrical noise coupling.
• Connect cable shields according to the Yokogawa grounding specification for the installed control cabinet.
• Confirm correct polarity of thermocouple wiring before system commissioning.
• Check channel assignment and DCS database configuration before enabling temperature monitoring functions.
• Inspect terminal connections periodically to prevent loose contacts and signal instability.