Window capacitive moisture sensor
OwnerYishay Netzerinventor
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Abstract
An apparatus for sensing condensed moisture on the inside of automotive windows with essentially no sensitivity to precipitation on the outside of the window. The apparatus senses the influence of the moisture on the impedance (mainly capacitive) between two electrodes. It is intended especially for rear windows where the sensing electrodes can be integrated with the resistive heater network printed on the internal side and activate it automatically. Similarly it can be used for front windows where it can automate the operation of electrical or hot-air defoggers.
Claims11
An capacitive moisture sensor for sensing moisture on a surface of a dielectric, which capacitive moisture sensor is insensitive to the presence of moisture on the other unsensed side of the dielectric, the capacitive moisture sensor comprising
- (a) at least one pair of capacitive electrode plates coated on the surface of the dielectric on which moisture is to be sensed, said at least one pair of capacitive electrode plates including at least one excitation and one signal capacitive electrode plates;
- (b) electronic circuitry for substantially ignoring a resistive component of impedance between said electrode plates.
A capacitive moisture sensor as in clam 1, wherein said electronic circuitry for substantially ignoring a resistive component of impedance between said electrode plates includes a synchronous demodulator.
A window moisture sensing and evaporating system including an capacitive moisture sensor for sensing moisture on a surface of a window, which moisture sensor is insensitive to the presence of moisture on the other unsensed side of the window, comprising
- (a) an electrical heater element on a window surface;
- and,
- (b) the moisture sensor including at least two capacitive electrodes, including at least one each excitation and signal capacitive electrode plates, on the surface of the window on which moisture is to be sensed, the moisture sensor for use for the control of said electrical heater element.
Dependencies are inferred from the claim text.