EXCITATION OF POLYSILICON-BASED PRESSURE SENSORS

摘要

The object of this invention is to eliminate long-term transient behavior up on electrical excitation of polycrystalline silicon and provide electrical excitation with a minimal stabilization period and utilizing micro-power consumption. This invention comprises an electronic excitation circuit for a polycrystalline silicon sensor that detects the pressure of a process flow. The sensor consists of polycrystalline silicon piezoresistors (22) deposited onto a polycrystalline silicon sensing diaphragm (14) having a dielectric layer (18) interposed in between. Electrical excitation of the piezoresistor s is accomplished by an alternating electrical waveform having a constant amplitude of less than 10 volts and at a frequency of less than 100k Hz. The waveform is applied to a first input terminal (40a) of a Wheatstone bridge with an opposite polarity to a second input terminal (40b) of the bridge. Th e resultant voltage difference between the output terminals is used to detect an imbalance in the electrical resistors induced by applied pressure. The volta ge level and frequency range chosen is such that the circuit utilized approximately 1 mW of power.