| 摘要 |
PURPOSE:To enable a clear response indication of oscillation phenomena when gas reaches a prescribed concentration by providing a semiconductor film on an elastic surface wave propagation path on a piezo-electric substrate. CONSTITUTION:An SnO2 film 14 is vacuum deposited on an elastic surface wave delaying line 21 and combined with an amplifier 23 and a variable attenuator 24 to construct an elastic surface wave oscillator which generate an oscillation at an attenuation level of 5.0dB. When oxygen lets flow from a nozzle 25, the oscillation output decreases with the increase of the outflow rate thereof and the oscillation stops at a given value thereof. The flow rate of the oxygen to stop the oscillation varies with the set attenuation level of the attenuator and the heating temperature of the film 14. Therefore, a given amount of oxygen can be detected depending on stoppage of the oscillation by proper selection of the attenuation level of the attenuator and the surface temperature of the SnO2 film. |
