Development of a Capacitive Pressure Sensor Based on Havar Alloy Diaphragm

摘要

This paper proposes a new pressure sensor using Havar alloy film as the sensing diaphragm, which has higher strength and toughness, better corrosion resistance and magnetic resistance as compared to traditional films. 2D distribution graphs of stress and strain of the diaphragm under a given pressure are analyzed with ANSYS Workbench. The diaphragm sensitivity and nonlinear error can be calculated by constructing the curve of the displacement of diaphragm center varied with input pressures. Two key parameters, thickness and diameter of the diaphragm are solved by minimizing the nonlinear error of diaphragm. C/F and F/V conversion techniques are used in capacitance detection circuit for converting weak capacitive signal to voltage signal. A prototype sensor is constructed and the calibration experiment is conducted. Calibration data analyzing shows that the linearity of the pressure sensor is 0.03% in the working range of 0 to 35kPa, which indicates that the proposed capacitive pressure sensor using Havar alloy diaphragm possesses high accuracy.