Flowable material level sensing with shaped electrodes

Abstract

Level sensing designs and techniques that inherently compensate for physical variations in the flowable material. An illustrative container includes an electrode arrangement having two electrodes along a vertical span creating corresponding capacitances indicative of a level of the material within that vertical span. Differing electrode shapes or positions provide the capacitances with different dependences on the level. A level detection method includes: (i) measuring a first capacitance between a drive electrode and a first sensing electrode; (ii) measuring a second capacitance between the drive electrode and a second sensing electrode; and (iii) determining a ratio of variances in the first and second capacitances, the variances being relative to first and second capacitances for a container empty of the material. The ratio is indicative of said level and insensitive to temperature and permittivity of the material.