Langasite SAW Pressure Sensor for Harsh Environments

Wireless pressure sensing in harsh environments at temperatures in excess of 200 degrees C has important applications in energy generation, aerospace, and industrial processing. Such environments restrict or prevent the use of silicon based technology and battery powered sensor devices. Microwave acoustics, in particular surface acoustic wave (SAW) technology, allows the design of wireless pressure sensors to operate battery-free in a harsh environment. Current SAW-based pressure sensors operate up to approximately 200 degrees C and 150 psi and typically employ quartz substrates. The Langasite (LGS) family of crystals retains their piezoelectric properties up to their melting point of approximately 1470 degrees C, thus opening up the possibility of designing and implementing very high temperature and harsh environment LGS SAW pressure sensors. A square shaped sealed cavity has been used in this work with sensors strategically placed at the edges of the cavity for improved differential sensitivity and temperature compensated response. The fabricated devices were tested up to 225 psia and 500 degrees C.