Hot Wire Liquid-Level Indicator

Abstract

The theory of the method of measurement of liquid level by measurement of the resistance of a heated wire is developed, and it is applied to the design of a liquid‐nitrogen‐level indicator having a power dissipation of 3.4 mw/in. of length and a deviation from linearity in the calibration of less than 0.1 in. over its working length of 2.0 in. The apparatus should be applicable to the measurement of level of low viscosity liquids and its sensitivity is limited only by the temperature coefficient of resistance of the heated wire.