An instrumentation grade wall shear stress sensing system

This paper describes development of a MEMS wall shear stress sensor system to be used in wind tunnel applications. An analog synchronous modulation and demodulation interface circuit allows for both ac and dc measurement of varying capacitance, yielding real-time dynamic and mean flow information with a low noise floor. Directional information of the input flow is retained throughout the system with minimal phase delay. A sensitivity of 3.45mV/Pa at 1.128kHz and a DC stability of 0.2mV indicate minimum resolution of mean shear values of 58mPa. Physical resonance of 3.5kHz and a pressure rejection ratio of 72dB are also observed.