A method for evaluation of the inhomogeneity of thermoelements

Abstract

Thermoelectric inhomogeneity is the spatial variation of the Seebeck coefficient along a thermoelement. It is often considered to be the largest contribution of an uncertainty budget in thermocouple calibration. In this work, investigations of inhomogeneities were performed on single thermoelements, using a heater with short movable heating zones (two-gradient method). We chose platinum wires which are commonly used in noble metal thermocouples and copper wires which are available in good homogeneity and which are commonly used in base metal thermocouples. The results of different investigations of the thermoelements are presented.