A thermocouple is an electrical device consisting of two different conductors forming electrical junctions at differing temperatures. A thermocouple produces a temperature-dependent voltage as a result of the thermoelectric effect, and this voltage can be interpreted to measure temperature. Thermocouples are a widely used type of temperature sensor. 

Specially designed for measuring the temperature of air, e,g, in heating or air conditioning ducts. A very sensitive, high quality sensor which responds more rapidly than a general purpose probe.