Thermocouple
A loop consisting of two kinds of wire, joined at the hot, or measuring, junction and at the cold junction in the instrument. The voltage difference between the two junctions is proportional to the temperature difference between the junctions. In order for the current to be meaningful, the resistance of the thermocouple is critical, and the leads are designed for a specific installation. Their length should not be altered. Thermocouples used to measure cylinder head temperature are usually made of iron and constantan, and thermocouples that measure exhaust gas temperature for turbine engines are made of chromel and alumel.
Aviation Maintenance Technician Handbook — Airframe, p. G-36
Also defined in 1 more source
A device used to generate an electrical current. A thermocouple is made of two dissimilar metal wires whose ends are welded together to form a loop. A voltage exists in the loop proportional to the difference in temperature of the junctions at which the wires are joined. The amount of current flowing in the loop is determined by the types of metals used for the wires, the temperature difference between the junctions, and the resistance of the wires.
Aviation Maintenance Technician Handbook — Powerplant, p. G-27
Taught in PP-D Concepts, AF-H Quick reference, PP-D Procedures, PP-D Quick reference, AF-M Concepts, PP-E Quick reference and 2 more.