Effects of an additional air chamber on the sensitivity of a capacitive pressure sensor

This study demonstrates the effect of an additional air chamber on the sensitivity of an air-sealed capacitive pressure sensor. This effect is investigated by theoretical analysis, finite element analysis, and experimental validation. First, the variation in sensitivity of the capacitive pressure sensor with air chambers of various volumes was investigated by an analytical method as a theoretical approach and by FEM simulation. The results showed that the sensitivity of an air-sealed capacitive pressure sensor with a flexible diaphragm could be enhanced by adopting an additional air chamber. In this process, the variation in the ambient temperature was also considered. Experimental validation was conducted by fabricating a sensor to consider the previous result. The results of the experimental validation of the air-sealed capacitive pressure sensor with natural rubber latex (NRL) diaphragm showed that the sensitivity increased more than 15-fold by adopting the additional air chamber compared to the NRL sensor without the air chamber. Consequently, the NRL sensor with the additional air chamber measured a pressure sensitivity of 8986 ppm/kPa and a pressure responsivity of 1.391 MHz/kPa in the applied pressure range of 1–10 kPa. Finally, the effect of the variation in ambient temperature on the sensitivity of an air-sealed capacitive pressure sensor was measured and compared with the theoretical and FEM simulation results.