A Design and Analysis of a Square Diaphragm-Comb Structure Capacitive Pressure Sensor (SD-CSCPS)

This study illustrates the simulation and mathematical analysis of a square diaphragm-comb structure capacitive pressure sensor (SD-CSCPS).The detection of pressure ranges between 10 MPa and 100 MPa with linear output to the applied pressure is the primary emphasis of this research work.In this study, four square diaphragms of same length and breadth with different thickness of 25 m, 30 m, 35 m and 45m are studied.The construction and design method of a SD-CSCPS using a diaphragm are laid out step-by-step in the design chart.In this study, the square diaphragm is deflected due to applied pressure.This deflection is converted into linear displacement by a mechanical coupler so that the sensor output characteristic can be linearized.The analytical model has two components: the deflection model and the charge model.The deflection of the square diaphragm is computed in deflection model, as this deflection is used to move the movable comb structure.It is highly challenging to determine the absolute capacitance for such a complex construction; instead, the shift in capacitance is calculated in the charge model.The proposed 3D model of the SD-CSCPS was developed and simulated using COMSOL Multiphysics, which also validates the analytical model of SD-CSCPS.Among the various parameters that can increase SD-CSCPS sensitivity are the physical dimensions of the diaphragm, the number of interdigitated fingers of the comb, the dimension of the interdigital finger, the gap between the movable and stationary plates, Poison's ratio, and Young's modulus.In this study, the maximum sensitivity of the sensor with a diaphragm of 25 m was determined.The simulated and calculated sensitivity of the SD-CSCPS for a diaphragm thickness of 25 m are 0.253 fF/MPa and 0.319 fF/MPa, respectively.