| 摘要 |
PURPOSE:To obtain a flow rate detecting element of high sensitivity by providing a semiconductor oscillation detecting plate on one side face parallel with the flow of fluid of a resonance box having an inflow port and an outflow port of prescribed sizes. CONSTITUTION:An oscillation detecting plate 14 is provided on one side face parallel with the flow of fluid of a resonance box 11 having a pipe 15 for gas inflow and a pipe 16 for outflow of an inside diameter larger than that thereof, and the length of the box 11 is made larger than twice the width thereof and the inside diameter of the pipe 15 so that it resonates to the frequencies of the best generation efficiency out of the ultrasonic waves generated near the port 12. The plate 14 is formed by providing a piezoelectric thin film 25 in the gate part of an MOS field transistor having, for example, a source electrode 22, a drain electrode 23 and a gate electrode 24. The gate part is oscillated by the resonance frequencies of the ultrasonic sounds produced by the inflow of fluid, and electric charge is generated in the film 25, by which the electric current corresponding to flow rate is flowed. Thereby, the flow rate detecting element of high sensitivity is obtained. |
