Sensor quality for low pressure indication - research and solutions

In order to analyze the processes during the gas exchange in the engine, knowledge of pressure states in both inlet and outlet is required. This pressure measuring is known as "low pressure indication ". In the presented work, three examples of controlling the quality of low pressure measurement are presented. The projects performed during the collaboration with Kistler showed the high demands regarding accuracy, dimensions and lifetime of measuring chains and piezoresistive sensors for low pressure measurement. To gain reliable resultsfor use in simulation tools for calculating and modeling gas exchange phase the sensor and measuring chain must be designed in order to consider all possible influences on the signal such as thermal and mechanical stress, electrical parasitic induction and gas dynamic effects. The increasing demand regarding accuracy and low thermal drift for highly dynamic measurements and the restricted space available in most applications are further challenges. It was shown that: a small inaccuracy of measurement, lower than 10 mbar can be attained, the asymmetric course of the exhaust pulse can clearly be verified, and a protection screen for a sensor exposed to the exhaust blow-off pressure wave can be a tool to optimize between longlife and accuracy.