A thermocouple, or thermoelectric couple, consists of two conductive metal wires different. The wires are connected by two types of welds, hot spot and cold spot, also called a reference junction. When the hot junction is exposed to a temperature change, an electric voltage is created. We will then measure the electrical potential difference between the hot junction and the cold junction to measure the temperature. This is called the Seebeck thermoelectric effect, named after the German physicist Thomas Johann Seebeck who theorized this phenomenon in 1821.
The voltage generated in the conductive metal wires as a function of the temperature variation is measured by a voltmeter. We calculate the potential difference (electromotive force) between the hot junction and the cold junction, then this data is converted into degrees Celsius by a temperature transmitter. The conversion from voltage to temperature is done using a reference table and depends on the types of metals that make up the thermocouple. Indeed, the thermoelectric sensitivity of each metal is different. A Seebeck coefficient was assigned to each material based on this sensitivity.