Patent 5191791 Issued on March 9, 1993. Estimated Expiration Date: May 4, 2010. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.
The change in capacitance of a sensor is linearly proportional to ice thickness provided that the ice thickness is significantly less than the distance between the conductive electrodes. By employing sensors with different electrodes, the sensitivity to ice may be traded off against the ability to measure greater ice thickness. A sensor with small spacing between electrodes will exhibit a large change in capacitance when covered by a thin layer of ice, however, the capacitance change will be linear only for very thin layers of ice. A sensor with greater spacing between electrodes is less sensitive to ice accretion but has a correspondingly greater ice thickness measurement range. Accordingly, sensor (55) is relatively sensitive and is employed to determine whether or not ice or water is present. This is accomplished by circuit (60) determiniSTATEMENT REGARDING GOVERNMENT FUNDED RESEARCHThis invention was made with Government support under NAS1-18421, NAS2-12890 and NAS3-25618 awarded by the National Aeronautics and Space Administration. The Government has certain rights in this invention.
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