Piezoelectric pressure sensors for hypersonic flow measurements at high-temperatures

We present a microelectromechanical-systems (MEMS) piezoelectric pressure sensor designed for hypersonic flow measurements at extreme temperatures (>1000 °C). The sensing diaphragms have 700-μm diameter and are surface- and bulk-micromachined. The sensor employs aluminum nitride as a sensing layer due to its capability for high-temperature operation. We present the latest measurement results from a Ludwieg Mach-6 quiet tunnel, where prototype sensor data are compared against data from a state-of-the-art commercial sensor present in the same test. The prototype captures salient features of hypersonic flows including shock waves and second-mode instabilities indicative of laminar-to-turbulent transition. The prototype sensor also demonstrates superior signal-to-noise ratio in many test conditions. Prototypes have also demonstrated high-temperature operation by capturing audio while immersed in a butane flame (∼1200 °C).