Strain gauge type pressure sensors are widely used in different branches of industry to measure pressure from very low to very high (1400 Mpa) values. This article investigates a strain gauge type pressure sensor that uses silicon oil within its housing to transmit working pressure from the external environment to a sensing plate. An important failure mode arises from loss/leakage of the silicon oil, whereby a portion of the internal volume is replaced by gas, usually air. Coupled nonlinear governing equations have been derived and solved in both static and dynamical states to describe the behavior of the external membrane, the interface oil including pockets of gas, and the sensing plate. Nonlinear behavior arises from the plate and membrane midplane stretching, and of course the behavior of the gas. The resulting model describes how oil loss affects the sensor performance and changes the sensor output and pressure measurable range.
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