Critical control or monitoring of a process variable may require "dual validation" where two sensors are used to ensure contingency in the event of a sensor failure.

MEDACS and a TFML module can read the input from two sensors, averaging them to provide an output. Should a sensor fail or the difference between readings exceed a chosen value….the unit will recognise this, and choose to display the reading from the individual sensor closest to the previous average. An alarm relay will inform the operator.