Modelling Fluid Loss Faults in Piezoresistive Pressure Sensors

The efficient operation of industrial processes requires the timely and accurate diagnosis of faults in process equipment, particularly sensors, as acting on faulty measurement data can result in inefficient or dangerous operation. A common fault mode in industrial pressure sensors is mechanical damage resulting in the leakage of the internal oil (used to transmit external pressure to the sensing element) and the development of an air pocket within the device. In previous work, we have experimentally determined the faulty measurement characteristics of a commercial pressure sensor, where the sensor manufacturer has provided modified sensors with calibrated degrees of oil loss. The current paper develops a mathematical model of this tenso-resistive pressure sensor, which describes and explains the impact that oil loss, and hence the presence of an air pocket, has on the static measurement response.