A fast-response microthermocouple

Abstract

A fast-response chromel-alumel (and chromel-constantan) microthermocouple is described and its dynamic characteristics are measured. The microthermocouple features a microdisk junction 0.08 mm in diameter and 2.5 μm thick. Its time constant in turbulent flow of liquid Refrigerant-113 (a poor heat conductor) is measured to be ∼4.6 ms. This time constant was reduced to ∼3.4 ms with a phase-lead compensation circuit. It was possible to distinguish between vapor and liquid phase temperatures in turbulent subcooled boiling flow of Refrigerant-113 with the compensated microthermocouple.