Surface-acoustic-wave pressure and temperature sensors

A sensitive sensor for the measurement of pressure and temperature is created by fabricating a surface-acoustic-wave (SAW) delay path on the surface of a thin diaphragm which, in turn, is in contact with the medium to be measured. The SAW delay path and associated electroacoustic transducers are utilized as the feedback circuit in a miniature electronic oscillator. Since the SAW time delay varies almost linearly with diaphragm temperature and pressure induced strain, the oscillator frequency is also a predominantly linear function of pressure and temperature. A frequency output sensor is desirable both for high-measurement resolution and for compatibility with digital data processors. Sensor configurations are discussed which can be optimized for independent measurement of either temperature or pressure.