Capacitor pressure transducer with housing

Abstract

An improved ceramic capacitive pressure transducer adaptable for use in automobiles is disclosed. The pressure transducer comprises a thin flexible diaphragm disc having a capacitor electrode deposited on it. A thick cylindrical base substrate has a top surface with a second capacitor electrode deposited thereon and the diaphragm is bonded to the top surface of the base substrate by an annular glass ring such that the first and second electrodes are separated from each other and face each other directly across an air gap. The diaphragm, the top surface of the base substrate and the annular glass ring form an internal cavity in which a reference vacuum is stored. In response to pressure changes outside of this cavity, the diaphragm will flex and thereby change the capacitance created by the first and second electrodes. The base substrate has an integral annular flange laterally extending with respect to and beyond the top surface of the base and located below the top surface and between the top and bottom surfaces. A sealing rubber O-ring is mounted on the flange and is used to sealingly mount the transducer to a housing wall without applying stress to the diaphram.