Capacitance accelerometer

Abstract

A capacitive acceleration sensor using a common PWB as one of the plates of the capacitive transducer and the wiring connections thereto. An acceleration input moves a capacitor plate to produce a measurable change in capacitance. An electronic signal conditioner accurately converts the capacitance output to a voltage signal to provide an acceleration sensor featuring accurate DC performance. The transducer and electronics are disposed on a PWB making up a complete sensor package. In a first embodiment, the capacitor comprises a fixed electrode on the PWB and a movable acceleration responsive electrode secured to a support by a conductive resilient member, the support coupled to an electrically conductive region on the PWB spaced from the fixed electrode by a guard ring to minimize stray charge between the capacitor electrodes. In a second embodiment, the movable capacitor electrode is supported at its center by a pair of electrically conductive members, one coupled to an electrically conductive region on a substrate spaced from the movable electrode by a sealing spacer. The fixed capacitor electrode is disposed either on the same substrate or a separate substrate on the opposite side of the movable electrode spaced from the movable electrode by a sealing spacer and having the fixed capacitor electrode thereon. The movable capacitor electrode can be secured at its center or at an edge and can be produced by stamping and/or photoetching and provide a single element where plural elements were previously required.