Displacer-Type Liquid Level Sensor with Liquid Density Auto-Compensation

Abstract

In the classic displacer-type liquid level measuring method, liquid level is calculated via the buoyancy force exerted by the liquid on a displacer. This technology has high linearity, precision, accuracy, ease of installation and low cost. Nonetheless, displacer level sensors have significant sensitivity to variations in liquid density, which hinder its use in industrial applications that such quantity is not held constant. In this paper a novel displacer-type liquid level sensor is presented and analyzed. The method consists of adding another displacer and thus calculating the new measured value by the quotient of the buoyancy forces of both displacers. Therefore, the new measurement is ideally insensitive to the variations in liquid density. A prototype was built and prototype results presented high linearity, being able to mitigate the sensitivity to the liquid density, increasing accuracy in the measurements.