Honeywell MC-TAMT04 (51305890-175) Experion PKS LLMUX2 Thermocouple Field Termination Assembly

The Honeywell MC-TAMT04 (Part Number 51305890-175) is a high-reliability, 16-channel LLMUX2 Thermocouple Field Termination Assembly (FTA) engineered for integration with Honeywell Experion PKS, xPM, and Experion PMIO architectures. Utilizing advanced solid-state technology, this module replaces legacy mercury-wetted relays, eliminating environmental hazards while drastically improving loop resistance tolerances to allow longer field thermocouple wiring runs. The assembly is equipped with an integrated local Cold Junction Reference (CJR), high-performance compression terminals, a single Input/Output Processor (IOP) interface, and a robust conformal coating for continuous duty in harsh, corrosive industrial environments.

Features

• Per-Channel Isolation: 16 fully-isolated channels providing robust channel-to-channel, channel-to-PM, and channel-to-power supply common separation.
• Solid-State Relay Architecture: Replaces traditional mercury-wetted components to provide enhanced stability and long-term operating life.
• Dedicated A/D Per Channel: High-performance analog-to-digital conversion circuits per channel ensure precise signal tracking.
• Fast Open-Thermocouple Detection: Built-in advanced diagnostics identify open-circuit faults within a fixed 1-second interval.
• Dual-Purpose Design: The same underlying 51305890-175 hardware handles both local and remote cold junction tracking through an on-board jumper configuration.
• Corrosive Environment Protection: Factory conformally coated to meet stringent industrial atmospheric standards and maintain CE compliance.

Applications

• Experion PKS distributed control systems (DCS) process monitoring.
• High-density temperature acquisition loops in hydrocarbon processing and petrochemical facilities.
• Thermal monitoring and profiling inside gas turbines, boilers, and heavy industrial furnaces.
• Corrosive chemical processing plants requiring conformally coated process interface equipment.

Technical Specifications Table

Alternative Models & Compatibility

The MC-TAMT04 serves as a direct form, fit, and functional replacement for legacy, obsolete LLMUX TC FTA variants. It seamlessly replaces non-CE compliant boards MU-TAMT02 (51401491-100) and MC-TAMT02 (51401491-150), alongside older CE-compliant models MU-TAMT03 (51309223-125) and MC-TAMT03 (51309223-175). Notably, the base board assembly (51305890-175) is identical to the one used in the remote cold junction reference model, MC-TAMT14.

Application Pitfalls & Engineering Notes

When evaluating field thermocouple loop resistances, the solid-state architecture of the LLMUX2 provides an expanded loop driving capability compared to old mercury systems, enabling longer field cable boundaries without signaling loss. However, engineers must carefully manage enclosure thermal metrics. The assembly dissipates up to 2.25 watts continuously, yielding a heat load of 7.68 Btu per hour. Ensure proper panel venting if multiple assemblies are grouped in dense Marshalling racks to avoid crossing the maximum 40 degC operational limit under high-humidity environments.

Commissioning & Wiring Tips

The unit utilizes a 6-pin compression plug for connection at the J6 port located at the top of the board assembly. If upgrading an older non-CE legacy cabinet setup that features a 4-pin plug, the internal wires must be extracted and reworked into the 6-pin connector provided in the MC-TAMT04 shipping container. Additionally, ensure the address jumper designated as "UNIT" is set correctly to '0' or '1' to mirror the address scheme of the existing system before connecting the 50-pin J1 cable interface to the Power Adapter.

Installation Guidelines