Digital compensated capacitive pressure sensor using CMOS technology for low pressure measurements

A capacitive pressure sensor with digital output for low-pressure measurements has been fabricated using CMOS technology. The sensor output has been compensated and adjusted by a newly developed method. The sensor has the hybrid configuration of a sensor chip and a digital IC chip. The sensor chip consists of a sensor capacitor, a reference capacitor, and two capacitance-to-frequency converter circuits. The digital IC chip consists of a clock generator, a timing circuit, and a 12-b up/down counter. The thermal sensitivity shift and the thermal zero shift of the output were compensated at the sensor chip. The offset and full scale span of the output were compensated at the sensor chip. By using the novel compensation and adjustment technique, a thermal sensitivity shift of 0.026%F.S./ degrees C and a thermal zero shift of 0.013%F.S./ degrees C for a pressure range of 0-200 mmH/sub 2/O and a temperature range of 25-75 degrees C were obtained.<
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