Apparatus for generating an electrical signal indicative of liquid level

Abstract From the Canadian patent

Apparatus for generating an electrical signal indicative of the level of a liquid stored in a reservoir. The apparatus includes first and second probes spaced from one another and extending into the reservoir. Each of the probes includes a metal electrode surrounded by a preferably dielectric material. The liquid to be measured contacts the dielectric material, but does not directly contact the electrodes. A preferably alternating voltage is applied across the electrodes and the impedance therebetween is sensed. The impedance between the electrodes varies as a function of the level of the liquid in the reservoir and this impedance is substantially greater than the impedance between the …