Product Overview

The Allen-Bradley 1746-NT8​ is an 8-channel thermocouple and millivolt input module from Rockwell Automation’s SLC 500 (1746) family. Its purpose is to take the low-level signals produced by thermocouples and mV transmitters and convert them into usable temperature or voltage data for the SLC 500 processor. In a legacy SLC 500 rack, the 1746-NT8​ is the temperature interface: up to eight thermocouples can be landed on one module, each channel converted at 15-bit resolution, with the cold-junction compensation and linearization handled on the module rather than in the ladder logic.The module accepts eight differential inputs and supports a wide range of thermocouple types — B, E, J, K, L, N, R, S, T, U and W — together with a direct millivolt mode. This range is what makes the 1746-NT8​ usable across applications rather than tied to one sensor family: a furnace application can mix type K on the hot zones with type J on the auxiliary circuits, while a test rig can use the mV mode to read a non-thermocouple transducer. The cold-junction compensation is built in, so the terminal-block temperature is measured and used to correct the thermocouple reading — a necessary step, because a thermocouple measures a temperature difference, not an absolute temperature, and an uncompensated reading drifts with the cabinet temperature.For plants still operating SLC 500 systems, the value of the 1746-NT8​ is continuity. These are mature installations in heat treatment, plastics, furnaces, ovens, process skids, and machine-tool thermal monitoring, where replacing the controller would cost more than the value of the upgrade. A verified spare with the correct channel configuration is what keeps such a system running; the module’s straightforward mapping means a replacement can be dropped in without re-engineering the rack. Because the module is obsolete and has no direct replacement, procurement should be treated as verified spare stock rather than new-system design.

Technical Specifications