Description

• Model: MC-TAMT04
• Brand: Honeywell
• Series: LLMUX2 / Experion PKS
• Core Function: Terminates and multiplexes low-level thermocouple signals
• Type: Thermocouple Field Termination Assembly (FTA)
• Key Specs: 16 isolated channels, local CJR, conformally coated, single IOP interface
• Part Number: 51305890-175
• Application: xPM and Experion PMIO systems

Product Introduction

Honeywell MC-TAMT04 is an LLMUX2 Thermocouple Field Termination Assembly (FTA) designed for low-level temperature signal acquisition in Honeywell process-control systems. It provides 16 isolated thermocouple channels, local Cold Junction Reference (CJR), compression-terminal field wiring, and a single IOP interface. Honeywell’s LLMUX2 documentation identifies this configuration as conformally coated and CE compliant, with part number 51305890-175.

The newer LLMUX2 design replaced earlier LLMUX FTAs and uses solid-state circuitry instead of mercury-wetted relays. Honeywell specifies a 1-second input scan rate, 2 μV/bit resolution for thermocouple measurements, and a typical CJR compensation accuracy of ±0.5 °C. The FTA operates from a nominal 24 VDC external supply, with a documented 15–30 VDC range.

Key Technical Specifications

Honeywell documents the LLMUX2 family as a 16-channel, fully isolated temperature-input architecture supporting thermocouple and RTD variants. For the TC version, the published specifications include the local CJR range, electrical isolation, resolution, power requirements, environmental limits, and agency certifications.

Honeywell MC-TAMT04

Application and Selection Notes

This is a field termination assembly, not a standalone DCS analog input card. Its job is to connect low-level thermocouple wiring to the appropriate Honeywell I/O architecture and pass the signals through the LLMUX2 interface.

Typical applications include furnace temperature monitoring, process heating, boiler systems, turbine auxiliaries, and other plant areas where multiple thermocouples must be collected in a compact cabinet arrangement.

Honeywell states that LLMUX2 FTAs are intended for xPM and Experion PMIO applications and can be used for new installations, capacity upgrades, or replacement of older LLMUX FTAs. The updated design adds separate A/D conversion per channel at the FTA level, improved open-thermocouple detection, longer permissible field wiring, and onboard diagnostics.

One important procurement detail: MC-TAMT04 is the local-CJR thermocouple version. The remote-CJR version belongs to a different model designation. Do not mix them simply because the housing looks similar.

Advantages and Limitations

Advantages

• 16 thermocouple channels in one FTA.
• Fully isolated field inputs.
• Local cold-junction compensation.
• Solid-state architecture with onboard diagnostics.
• Conformal coating for the specified industrial configuration.
• Direct replacement path for several older LLMUX TC FTA configurations.

Limitations

• Intended for thermocouple applications, not a general 4–20 mA input card.
• Requires the correct Honeywell I/O architecture and interface hardware.
• Local-CJR and remote-CJR versions are different configurations.
• The published environmental rating is 0–50 °C operating temperature for the LLMUX2 FTA family.

Quality Inspection and Pre-Shipment Checks

1. Incoming inspection: Verify the Honeywell model, part number 51305890-175, board markings, compression terminals, connector condition, coating integrity, and signs of corrosion or previous repair.
2. Live test: Use an appropriate Honeywell PMIO/LLMUX2 test setup to verify startup, channel recognition, representative thermocouple inputs, open-wire detection, and diagnostic status. Record the results in a Test Report.
3. Electrical checks: Verify terminal continuity, isolation-related checks, supply paths, and connector integrity according to the approved test procedure.
4. Configuration verification: Record the associated IOP, FTA position, channel mapping, CJR configuration, and field wiring before shipment.
5. Final QC: Photograph the identification label and terminal arrangement, seal the unit in ESD-safe packaging, add cushioning, and retain the QC record.

Test photos and available Test Reports can be provided with the shipment when requested.

Technical Replacement Risks

Wrong FTA type. MC-TAMT04 is the thermocouple version with local CJR. The remote-CJR design uses a different configuration and additional hardware.

Terminal conversion mistakes. Older LLMUX installations can use different connector arrangements. Honeywell’s LLMUX2 manual even documents reworking older 4-pin wiring for the newer 6-pin connector arrangement. Check the actual installation drawing before moving conductors.

Temperature-range assumptions. The FTA electronics have a specified operating range of 0–50 °C. Do not confuse this with the much wider temperature range that an individual thermocouple sensor may measure.

I/O architecture mismatch. LLMUX2 was designed for xPM and Experion PMIO installations. It is not a universal thermocouple terminal board.

And yes—take a photo before disconnecting the old FTA. Especially the terminal blocks. That little habit saves a surprising amount of commissioning time.

Purchase and Logistics Notes

For international procurement, describe the item as Honeywell MC-TAMT04 LLMUX2 Thermocouple FTA, Local CJR, Conformally Coated, Part No. 51305890-175.

Clearly state the actual condition:

• New Original
• New Surplus
• Refurbished
• Repaired

Before shipment, request confirmation of the complete model, part number, revision, coating condition, functional-test status, warranty, country of origin, gross weight, and package dimensions.

Honeywell documentation identifies this exact configuration as a CE-compliant, conformally coated LLMUX2 TC FTA, and identifies 51305890-175 as the associated FTA part number.

For export packaging, protect the compression terminals from impact, keep the assembly dry, use ESD-safe protection for exposed electronics, and ensure the commercial invoice, packing list, and physical label all show the same part number.

Quick Conclusion

• MC-TAMT04 is a Honeywell LLMUX2 Thermocouple FTA with local CJR.
• It provides 16 fully isolated thermocouple channels for the applicable PMIO architecture.
• The documented part number is 51305890-175.
• It uses a 24 VDC nominal supply with a 15–30 VDC operating range.
• The unit is conformally coated and CE compliant in the documented configuration.
• Exact compatibility should be checked against the IOP, FTA wiring, CJR arrangement, and installed Experion/xPM architecture.

FAQ

What is Honeywell MC-TAMT04?

It is an LLMUX2 Thermocouple Field Termination Assembly used with Honeywell xPM and Experion PMIO systems.

How many thermocouple channels does it support?

The LLMUX2 TC FTA architecture supports 16 fully isolated channels.

Does it use local or remote cold-junction compensation?

MC-TAMT04 is the local CJR configuration. The remote-CJR variant uses a different model designation.

What is the associated part number?

Honeywell’s LLMUX2 manual identifies 51305890-175 as the FTA part number for this configuration.

What power supply does it require?

The documented external supply is 24 VDC nominal, with a 15–30 VDC range.

Can it directly replace an older LLMUX FTA?

Honeywell states that the LLMUX2 TC FTA is a direct replacement for several older LLMUX TC FTA configurations, but the connector and wiring arrangement must still be checked during replacement.