A robust pressure sensor for harsh environmental applications

Due to economical and environmental requirements there is a strong need both to increase the efficiency and to monitor the actual status of gas turbines, rocket engines and deep drilling systems. For these applications a micromachined pressure sensor based on a sapphire body and a platinum thin film metallization is presented to withstand harsh environments such as high temperature levels, aggressive media and/or high pressure loads. For pre-evaluation purposes, a reusable packing is used enabling the device characterization in a very efficient way up to temperatures of 440 °C and pressures of 30 bar, respectively. As expected, the output signals of the Wheatstone bridge increase with higher pressures, but decrease with enhanced temperature levels. Furthermore, these characteristics show a sensitivity of about 10 μV/(V bar) in this temperature range and a negative drift in the offset when no pressure load is applied with increasing temperature. This effect is predominantly caused by the mismatch of the temperature coefficients of expansion associated with the device and the housing leading to a pre-stressed membrane.