Yokogawa AMM22T Thermocouple Input Multiplexer Module

The Yokogawa AMM22T, also cataloged as the AMM22T Thermocouple Input Multiplexer Module, operates as a dedicated hardware component for multi-channel temperature sensor signal acquisition and conditioning within Yokogawa process control platforms. It processes low-millivolt inputs from J, K, T, E, R, S, B, and N thermocouple sensors and converts them into standardized analog current output loop signals.

Hardware Specifications

Cold Junction Compensation and Signal Conditioning

The AMM22T incorporates internal cold junction compensation (CJC) circuitry alongside sensor linearization networks to correct for ambient temperature drifts across the terminal junction. Operating in conjunction with downstream analog input assemblies running 4-20 mA HART loop protocol communications, the multiplexer isolates input channels to suppress high common-mode voltages. Integrated signal conditioning and fault detection networks continually track thermocouple continuity, driving outputs to predefined fail-safe levels upon open-circuit detection.

Frequently Asked Questions

Q: How does the AMM22T maintain measurement accuracy during ambient temperature variations at the terminal blocks?

A: Integrated cold junction compensation (CJC) circuitry continuously measures ambient reference point temperatures and offsets thermo-electric voltage drifts prior to A/D conversion and output processing.

Q: What action does the AMM22T take when an open-circuit fault occurs on a thermocouple input?

A: The onboard fault detection and isolation logic identifies sensor burnout or wire breakage and forces the corresponding output channel into a configured out-of-range state.

Q: Can the AMM22T be configured for both 0-20 mA and 4-20 mA current loops?

A: Yes, output signal ranges can be selected between 0-20 mA and 4-20 mA with an overall output conversion accuracy of +/-0.25%.

Field Installation Guidelines

• ESD Protection: Always wear a grounded anti-static wrist strap when contacting the terminal block assembly or internal module electronics.
• Cold Junction Sensor Integrity: Ensure the internal CJC temperature sensor on the terminal block remains unshielded from ambient air but protected from direct external thermal radiation or heat sources.
• Shield Grounding: Connect thermocouple extension cable shields to a single dedicated system ground bar at the cabinet entry point to maintain high common-mode noise rejection.
• Wiring Separation: Route low-millivolt thermocouple leads in separate grounded conduit raceways isolated from high-voltage power lines and inductive switching loads.