A thermocouple consists of two dissimilar wires welded together at one end to form a:

A thermocouple operates based on the principle of thermoelectricity, which involves the production of a voltage that is dependent on the temperature difference between two different metals. The two dissimilar wires that are welded together at one end create what is known as the hot junction. When the temperature at this junction changes, a voltage is generated that varies according to the specific properties of the materials used.

The hot junction is critical in determining the temperature measurement of the thermocouple, as it is the junction where heat is applied (or where the temperature is being measured). The other end of the thermocouple is referred to as the cold junction, where the temperature is typically held constant or is at a known reference temperature.

The distinction of the hot junction is crucial for interpreting temperature readings accurately, as the voltage produced will provide an indication of the temperature at this junction relative to the reference junction. Understanding this concept is key for correctly utilizing thermocouples in various applications, such as temperature control and monitoring in industrial environments.