What is a Thermocouple?

Thermocouples are the most common sensor used for exhaust gas temperature measuring

Thermocouples consist of a pair of dissimilar metal wires joined typically at one end, producing a net thermoelectric voltage between the open pair according to the size of the temperature difference between the ends, the relative Seebeck coefficient of the wire pair and the uniformity of the wire-pair relative to the Seebeck coefficient. Thermocouples measure a relative temperature not an absolute temperature. In other words, a thermocouple requires a reference of known temperature. Commonly commercialized thermocouples utilize and independent sensor, such as a thermister to provide the reading of the reference temperature.

The discovery of thermoelectricity is accredited to Thomas Johann Seebeck (1770-1831) Raised in Estonia, a son of a prominent merchant. In 1802 he became a medical doctor. In 1821 he discovered that a compass needle deflected when placed near a closed loop formed from two dissimilar metal conductors if the junctions were maintained at different temperatures. He also observed that the deflection of the compass needle was proportional to the temperature difference. Subsequently he described that it depended on the type of conducting materials used, and not on the temperature distributed along the conductors. The Seebeck coefficient is defined as the open circuit voltage produced between two points on a conductor, where a uniform temperature difference of 1K ohms exists between those points... Want to know more? Go to the web page