Design and analysis of hairpin piezoresistive pressure sensor with improved linearity using square and circular diaphragms

A novel structure for piezoresistive pressure sensors is proposed. The structure comprises two piezo-resistors, one mounted on a flat diaphragm and the other mounted outside of the diaphragm so that a hairpin-shaped structure is formed. As a result, one of the piezo-resistors will be affected by the input pressure and the other one will not. Also an inverting Operational Amplifier (OP-AMP) amplifier is utilised. The proposed pressure sensor can be designed using both square diaphragm or circular diaphragm and it has the advantage of higher linearity for input pressure range of 1 MPa in comparison with conventional structures. The value of nonlinearity (NL) is decreased from 0.5515% full-scale (FS), for the conventional sensor, to 0.1138% FS (for the proposed sensor with square diaphragm) and 0.0761% FS (for the proposed sensor with circular diaphragm), which shows an improvement in reducing NL about 80% in square diaphragm and about 86% when circular diaphragm is employed. The proposed structure is analysed and simulated using COMSOL multiphysics software.