Secondary Diaphragm Thickness Effects and Improved Pressure Measurements in an Expansion Tube

摘要

In this Note, practical information has been presented on acquiring pressure measurements in impulse flow facilities, specifically, an expansion tube. It has been shown that noise in pressure measurements corresponds to secondary diaphragm fragments impacting with structures into which transducers are mounted, and noise in two different types of transducers as a function of secondary diaphragm thickness has been quantified. It was observed that noise decreases with decreasing diaphragm thickness, and that piezoresistive transducers are less susceptible to vibration-induced noise than piezoelectric transducers. As a derivative result, it was concluded that secondary diaphragm thickness has no observable impact on test gas conditions, as inferred from shock Mach numbers. It has also been shown that piezoresistive transducer measurement quality depends on the material into which the sensor is mounted and whether or not the sensor circuit is grounded.