The AM25T multiplexer has a built-in PRT temperature bridge circuit for accurate thermocouple cold junction compensation. It also has heat stabilization features designed to minimize temperature gradients across the wiring panel. The AM25T incorporates a large amount of thermal mass in a central concentrated area around the wiring panel terminals. The wiring terminals on the AM25T are located close to each other and close to the heat stabilization mass.
On the AM16/32B multiplexer, the wiring panel terminals are spread out across a larger area and do not have the large thermal mass design around the terminals that the AM25T has. Part of the thermal mass includes a heat bar that runs under the wiring panel connectors of which the PRT reference element is coupled to. The PRT element is incorporated into a precision full bridge circuit and calibrated for accurate reference temperature readings. The AM16/32B multiplexer does not have a built-in reference temperature PRT and heat bar design. When using AM16/32B multiplexers for thermocouple measurements, an external reference temperature measurement will need to be provided.
Because of its built-in reference temperature circuit and thermal stabilization features, the AM25T multiplexer is more suitable for thermocouple measurements.