Design and testing of piezoelectric resonant pressure sensor

Abstract

A stainless steel resonant pressure sensor with a new design is proposed with piezoelectric excitation and detection. The sensor consists of a sensing diaphragm, inclined trusses, vertical mounts and a resonating beam. The deflection of the diaphragm is transferred to the resonating beam via specially designed inclined trusses and vertical mounts. The analytical model of the sensor is developed using Ritz method and direct stiffness method for the non uniform sensing diaphragm and resonating beam respectively. The relation between strain due to applied pressure and change in the resonance frequency is derived. The sensor is also modelled numerically using MEMS CAD Tool CoventorWare. The sensor is fabricated with three different grades of stainless steel namely SS 304, SS 431, 15-5 PH, using Electrical Discharge Machining (EDM) and wire cut EDM process. The sensors are tested for its characteristics for an input pressure of 0–25bar. The sensor fabricated using 15-5 PH is found to have good linearity, repeatability, higher sensitivity and low hysteresis compared to the sensors fabricated with SS 304 and SS 431. The sensor design is simple, fabrication involves well known machining process, self packed and hence cost effective.