A new piezoresistive high pressure sensor utilizing combination of three-axis normal stress components

A piezoresistive high pressure sensor utilizing a combination of three-axis normal stress components has been developed. Firstly, the principle, FEM analysis, fabrication and characteristics of a newly developed piezoresistive force sensor are briefly summarized. Secondly, the force sensor is adopted as the sensing unit of a high pressure sensor. The pressure sensor is composed of an embedded force sensor unit, a metal diaphragm and a metal case. Pressure is transmitted into force which is applied to piezoresistors on a sensor chip through a force transmission rod. Stresses in piezoresistors depend on the diameter, height and Young´s modulus of the rod, and the diaphragm thickness of the sensor chip. In order to obtain large resistance changes in piezoresistors, the optimum combination of these parameters was investigated. A prototype pressure sensor having an SUS630 stainless steel diaphragm of 10 mm-diameter and 1 mm-thickness was fabricated. An output voltage of more than 50 mV/5 V at 150 MPa and a sensitivity temperature characteristic of 0.11% F.S/°C in the range from room temperature to 150°C were realized