A sensitivity enhanced touch mode capacitive pressure sensor with double cavities

A sensitivity enhanced touch mode capacitive pressure sensor with double cavities is proposed to improve sensitivity of pressure wave detection in this paper. The double cavities and the small gap structure reduce the influence of the thermal expansion of gas and slow the air exchange by the gap, which increases the pressure sensing ability of the sensor. The top and bottom cavities have the same pressure but different volumes. Due to the slow fluid in the gap, the amplitude of the bottom cavity diaphragm is amplified to improve the sensitivity of the capacitance. Besides, the plate may touch the bottom to increases the amount of capacitance which can play a key role of protecting sensor for over-range loads. COMSOL Multiphysics simulation is used to verify the feasibility of the model. The experimental results show that the capacitance of the sensor increases with the diameter of the top cavity. The threshold voltage is small and the sensitivity of the sensor increases. The volume ratio between the top and the bottom cavities of the sensor has a significant influence on the pressure sensitivity from both theoretical and experimental aspects. The plate touch capacitor can effectively improve the sensitivity of pressure detection. Consequently, the test result of the sensor with double cavities shows the sensitivity of the sensor in the working range which is 0.3–0.7 N is 1003210.27 ppm/kPa and the maximum hysteresis error is 0.15 pF. In addition, folded diaphragm for the sensor is more conducive to detecting micro signals.