An improved fast-response microthermocouplea)

Abstract

An improved wire-type chromel–alumel microthermocouple with a disk-shaped junction is described. In this design, the 20 μm diameter thermocouple wires are installed taut between two 127 μm diameter prongs, one of chromel and the other of alumel. The disk junction, of 0.1 mm diameter and 4 μm thick, is located approximately midway between the prong tips. Time constants of two microthermocouples are reported. The two microthermocouples differ from each other primarily in the length of the prongs. The microthermocouple with the longer prongs exhibits faster response, its time constant in turbulent flow of liquid Refrigerant-113 (a poor conductor of heat) being less than 2 ms.