The Honeywell 51301874-100 is the thermocouple mux board for the Low Energy PIU. This board contains the reed relays which can switch up to 16 thermocouple inputs to the LEPIU CCFA. The LEPIU can linearize type J, K, T, S, E, and R thermocouples.

The relays on this mux board have a finite lifetime. As the relays approach their lifetime limit of cycles, the mux boards become less reliable. WPC has put a lot of effort into improving the reliability of these mux boards.

This relay board is used with Honeywell's 51301880-100 or WPC's 51301880-101 terminal board, which provides the cold junction reference.