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.

Designing an accurate system for temperature measurements

“…However, there is one considerable drawback such as degradation of TC legs [22,29,30]. Degradation processes are prone to all types of used TCs [31][32][33][34][35][36][37]. They appear due to long term use at high temperatures [29,36].…”

“…For the first time, the problem of thermoelectric inhomogeneity was considered in 1906 [43], but according to [29,30,32,44] it still remains one of the main sources of error in temperature measurements using TC. Despite the studies in this field [40,42,[44][45][46][47] the problem has still not been solved yet.…”

Theoretical and Experimental Research of Error of Method of Thermocouple with Controlled Profile of Temperature Field

“…Then we plug the values obtained in (11) to (8) and solve (8) for T for each experiment. As can be seen from Table 1.…”

“…Noble metal TCs are used mostly as reference sensors [1], [2], [10]. All TCs of all kinds without exception are prone to degradation processes of their thermoelectrodes [11]- [15].…”

“…A lot of time passed since then, but the problem is still topical [7] despite quite a big number of investigations of inhomogeneity of TCs [11]- [17], [25]- [27].…”