| 摘要 |
PURPOSE:To perform reliable detection through simple circuit constitution by blocking the part where two pressure conduit parts formed in a vortex generating body communicate with each other by a semiconductor pressure sensor, and detecting a pressure ripple. CONSTITUTION:When a piezo-resistance element 10 which varies in electric resistance when a semiconductor of silicon is strained mechanically is arranged at the communication part between the pressure conduits 5 and 6, the element 10 varies in resistance value with the pressure difference between the conduits 5 and 6. In this case, the pressure difference pulsates at a frequency based upon vortex generation and is inverted in polarity alternately. The output of this element 10 is supplied to an operational amplifier 7 to extract a pressure ripple accompanying the vortex generation. The output of the amplifier 7 is supplied to a comparator 8 and compared with a reference voltage VR to obtain Vout, whose frequency corresponds to the generation frequency of vortexes, so the suction amount of air is calculated. |
