Thermocouple （TC） Level Meter for Liquid Nitrogen Low Heat Leak, Calibration-Free, and Low-Cost Level Meter

Abstract

We developed a simple level meter for a small cryostat, using the thermocouples （TCs）. It comprises one bamboo bar axis （BBA）, four K-type TCs, and one T-type TC connected to the BBA at the same distance. It is an inexpensive calibration-free level sensor. We estimated and measured the heat leaks of a small stainless-steel cryostat and the TC level meter during the design phase and the experiments. We used the integration of thermal conductivity from the Handbook and estimated the heat leaks for Alumel, Chromel, Constantan, and bamboo from similar materials in the Handbook. The heat leak of the small S/S cryostat is 1 ~ 2 W, but the level meterʼs heat leak was ~ 1/1000 that of the other cryostats. Therefore, we can disregard its heat leak. Since the new level meter is simple and cheap, it is easy to use.