A device for measuring temperatures, consisting of two dissimilar metals which produce an electromotive force roughly proportional to the temperature difference between their hot and cold junction ends.

Cold Junction
The reference junction of a thermocouple which is kept at a constant temperature.
ThermocoupleJunction MaterialsTemperature Range °C
E-TypeChromel-Constantan0 to 800
J-TypeIron-Constantan0 to 750
K-TypeChromel-Alumel-200 to 1200
N-TypeNicrosil-Nisil-200 to 1200
T-TypeCopper-Constantan-200 to 400

The ANSI established colour code for thermocouple wires in the negative lead is always red. Colour Code for base metal thermocouples is yellow for Type K, black for Type J, purple for Type E and blue for Type T.

See also: Cold Junction Compensation, E-Type Thermocouple, J-Type Thermocouple, K-Type Thermocouple, N-Type Thermocouple, Seebeck Effect, Thermal Electromotive Force, Thermopile.

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