Capacitative pressure sensor with close electrodes

Abstract

A pressure sensor (30) for harsh environments such as vehicle tires, formed from a chamber (58) partially defined by a flexible membrane (50), the chamber (58) containing a fluid at a reference pressure. In use, the flexible membrane (50) deflects due to pressure differentials between the reference pressure and the fluid pressure, the membrane being at least partially formed from conductive material. A conductive layer (36) is deposited within the chamber (58) spaced from the flexible membrane (50) such that they form opposing electrodes of a capacitor. Associated circuitry (34) is also deposited for converting the deflection of the flexible membrane (50) into an output signal indicative of the fluid pressure. The conductive layer (36) is less than 50 microns from the membrane in its undeflected state because capacitative sensors with closely spaced electrodes can have small surface area electrodes while maintaining enough capacitance for the required operating range. Furthermore, small electrodes reduce the power consumption of the sensor which in turn reduces the battery size needed for the operational life of the sensor.

Dependencies are inferred from the claim text.