Liquid level and quality measurement in reservoir. - uses processing unit with capacitative gauge which produces signals representing level and quality of liquid

摘要

The level monitoring device uses a gauge (11) which consists of four electrodes arranged as three capacitors. The capacitance of these capacitors indicate liquid level and dielectric constant or liquid quality. A modulator (12) produces charging times for each capacitance and these are used to shape a rectangular output (S1). A switching transistor (13) driven by the rectangular output (S1) modulates the impedance between the output terminals (1,2) by switching a resistance (14) and this is detected by a processing unit (20) which uses a high pass filter (22,23), comparator (24), demodulator (25) and microprocessor (26) to produce liquid level and quality.