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This paper describes a crash detection system developed for use in automotive passive restraint applications. The system is unique in that the small, rugged module performs all of the functions necessary to determine when airbag deployment is required. Because it is designed to be mounted near the impact zone, the system is well suited to three difficult crash discrimination situations: front impacts in body-on-frame vehicles such as light trucks, side impacts in any automobile, and crash severity discrimination for future adaptive restraint systems.

Hundreds of millions of micromachined, piezoresistive Manifold Absolute Pressure (MAP) sensors have been produced to reduce pollution and improve fuel efficiency in engine control systems. Other vehicle applications for micromachined pressure sensors include monitoring turbo pressure, barometric pressure, fuel tank leakage, fuel rail pressure and tire pressure. Exhaust gas recirculation and even door compression for side impact detection are employing micromachined silicon pressure sensors. Piezoresistive pressure sensors have dominated the automotive market to date. Practical micromachined capacitive pressure sensors have recently been developed and could replace the piezoresistive sensor in many applications. This paper will examine the advantages of both pressure sensing technologies, and discuss applications that an inexpensive capacitive pressure sensor will open up.