Thermocouples in Resistive and Induction Furnaces Operated in Strong Magnetic Fields

Thermomagnetic processing methods require an understanding of the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">in-situ</i> temperatures experienced by the workpieces. When commonly used thermocouples are employed in induction furnaces, RF fields can contribute additional temperature uncertainties to the ones arising from the use of strong magnetic fields. Focusing on temperatures between 300 °C to 1000 °C produced by induction and resistive furnaces, the readings generated by Type-K thermocouples were contrasted to the ones produced by Type-S and Type-N sensors for magnetic fields up to 9 T. Overall, when comparing Type-K response to temperatures above 700 °C in both zero-field and high field (≤ 9 T), the differences amounted to less than 1%, and when continuously measured has a linear relationship to the strength of the applied field. The relative invariance of Type-N and Type-S thermocouples was confirmed. These findings suggest that the use of thermocouples in high magnetic fields remains a viable option for applications, although the precision depends on the type used.