What is a thermocouple made of?
A thermocouple has two different metal alloys joined in a circuit. The alloys respond differently to thermal gradients and a net mV signal is generated. This is read by a sensitive instrument. See the peak sensors link.There is variety of metals to manufacture thermocouple to deal with range of temperature. There are eight types of thermocouples generally used in the industries considering characteristics of the material. Each type is denoted by a letter.Type of ThermocoupleMaterialTemperature Range ( °C )Noble MetalS typePt -10% Rh Vs Pt0 to 1450R typePt -13% Rh Vs Pt0 to 1450B typePt -30% Rh Vs Pt -6% Rh0 to 1750Base MetalE typeNi -10% Cr Vs Constantan0 to 1000J typeFe Vs Constantan0 to 760K typeNi -10% Cr Vs Ni-5% ( Al, Si )0 to 1150N typeNi -14% Cr -1.5% Si Vs Ni -4.5% Si -0.1%Mg0 to 1150T typeCu Vs Constantan0 to 400Read like: Type S thermocouple is manufactured using a platinum/10% rhodium for positive arm and pure platinum for negative arm.Check the other related link for a thermocouple calibration and validation procedure article