Thermocouple

\ˈthәr-mә-ˌkә-pәl\ n (1890) (TC) A pair of connected, welded junctions formed by two wires of dissimilar metals such as iron and Constantan. If a temperature difference exists between the two junctions, a weak emf, 40-50 μV/K, is generated in nearly linear proportion to the ∆T. Originally, one junction was placed in an ice bath to serve as a reference. Then, the emf developed in the circuit was simply convertible to temperature. Modern thermocouples employ a single junction and the instrument to which the TC is connected senses its own temperature and compensates the incoming signal for the difference between that temperature and 0°C. Plain wire TCs respond very rapidly to temperature