A wireless fluid-level measurement technique

This paper presents the application of a recently developed wireless measurement acquisition system to fluid-level measurement that alleviates many shortcomings of fluid-level measurement methods currently being used, including limited applicability of any one fluid-level sensor design; necessity for power to be supplied to each sensor and for the measurement to be extracted from each sensor via a physical connection to the sensor and needing a data channel and signal conditioning electronics be dedicated to each sensor. Use of wires results in other shortcomings such as logistics needed to add or replace sensors, weight, potential for electrical arcing and wire degradations. The fluid-level sensor design is a simple passive inductor–capacitor circuit that is not subject to mechanical failure that is possible when float and lever-arm systems are used. Oscillating magnetic fields are used to power the sensor. Once electrically excited, the sensor produces a magnetic field response. The response frequency corresponds to the amount of fluid within the capacitor's electric field. The sensor design can be modified for measuring the level of any fluid or non-gaseous fluid substance that can be stored in a non-conductive reservoir. Methods are presented for using the sensor in caustic, acidic or cryogenic fluids. A method is also presented for calibrating the sensor response with respect to fractional fluid levels for different fluids using only the response when sensor is completely immersed in fluid and with it is not immersed in fluid. Results are presented for measuring the levels of hydrochloric acid, liquid nitrogen, sugar, ground corn, ammonia, bleach, water, salt water, oil, and transmission fluid.