Abstract: A fringing-field capacitive liquid level sensor comprising an electrically insulating substrate, having a first and a second pattern of conductive capacitance plates plated on the substrate. Each pattern constitutes a fringing-field capacitor having a capacitance the value of which is both dependent on the liquid level and dependent on the dielectric constant of the liquid. The ratio of the two capacitances, however, is proportional to the liquid level and independent of the dielectric constant of the liquid. The fringing-field capacitive liquid level sensor may be used for measurement of liquids of substantially any dielectric constant without requiring full-scale calibration or knowledge of, and calibration for, dielectric constant of the liquid to be measured. Compensation for tilt angle can be provided through the addition of a second level sensor.

Abstract: A capacitive sensor for detecting raindrops on the external surface of a vehicular windshield, relying for its operation on the compensation of the capacitive signals which are due to variation of the dielectric constant of the windshield's glass with temperature, and on the elimination of capacitive signals which result from electrostatic interference or moisture deposition occurring at the inner surface of the windshield. The sensor includes electrodes printed on the internal surface of the windshield and is shielded by a grounded conducting enclosure. Another embodiment of the invention simultaneously senses raindrops on the external side of the window and moister on the internal surface of the windshield.