Surface acoustic wave gas flow rate sensor with self-heating feature.

摘要

A surface acoustic wave device for measuring the mass flow rate of a gas includes a surface acoustic wave delay line formed of a piezoelectric substrate and having a temperature coefficient of delay on the order of 10<-><4>/ DEG C. The substrate has disposed thereon a transmitting and a receiving interdigital transducer, the transducers being configured to have an operating frequency in the range of from 10MHz to 1000MHz. That portion of the substrate located between the transducers defines a propagation region and has a medium deposited thereon for absorbing a portion of the acoustical and/or electrical energy flowing thereacross. This absorbed energy increases the temperature of the propagation region over that of the surrounding ambient. A mass flow of the gas across the sensor will decrease its temperature and result in an upward shift in the resonant frequency. A suitable amplifier and resonant frequency detector may be coupled to the sensor for detecting the change in resonant frequency, thereby permitting mass flow rate measurement.