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Abstract

A pressure sensor (30) for sensing fluid pressure in harsh environments such as the air pressure in a tire by providing a chamber (58) partially defined by a flexible membrane (50). The flexible membrane (50) is at least partially formed from conductive material, and the chamber (58) contains a fluid at a reference pressure. The flexible membrane (50) deflects from any pressure difference between the reference pressure and the fluid pressure. A conductive layer (36) within the chamber spaced from the flexible membrane (50) and, associated circuitry (34) incorporating the flexible membrane (50) and the conductive layer (36). The conductive layer (36) and the flexible membrane (50) form capacitor electrodes and the deflection of the flexible membrane (50) changes the capacitance which the associated circuitry (34) converts into an output signal indicative of the fluid pressure. The conductive layer (36) is arranged so that fluid can be displaced from between the plates of the capacitor by the deflection of the flexible membrane (50).Venting the fluid between the electrodes to the other side of the fixed electrode, while keeping the chamber sealed, avoids the extreme fluid pressure that cause the squeeze film damping.

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First Claim