A thermocouple is a sensor used to measure temperature. It consists of two dissimilar metals joined together at one end. When the junction of the two metals is heated or cooled, a voltage is generated. This voltage is proportional to the temperature difference between the junction and the other end of the thermocouple.
Thermocouples are used in a wide variety of applications, including industrial processes, power plants, and scientific research. They are relatively inexpensive and easy to use, and they can measure temperatures over a wide range.