Measuring system for liquid level determination based on linear electro-optical effect of liquid crystal

Abstract

This article describes an updated system for measuring and controlling the level of liquid media. Well-known capacitance method for determining the liquid level is modernised. The new scheme proposes the use of electro-optical cell with a nematic liquid crystal. Homeotropically oriented liquid crystal is sandwiched between two plates, one of which is glass, and the other – crystal – cadmium sulfide CdS photoconductor. liquid crystal cell serves as an indicator. Its light transmittance depends on the applied voltage. Cell is designed so that the dependence of the phase delay of the voltage is linear. The article describes a mathematical model showing linear dependence, confirmed experimentally. Application of linear electrooptic effect observed in liquid crystals, allows to improve the accuracy and speed of measurement of liquid media, as the liquid crystal is an anisotropic medium more sensitive than solid crystals. The relaxation time of the orientation effects in liquid crystals is ~10-6 s. From the point of view of practical significance, this method will be of interest for application in the fuel and energy complex, in particular, oil and gas industry for the commercial accounting of petroleum products.