| 摘要 |
PURPOSE:To make it possible to detect the generation frequency of a Karman vortex from a low flow amount region to a high flow amount region, by altering the amplifying ratio of an AC amplifier for amplifying a vortex signal corresponding to the sucking amount of air. CONSTITUTION:A hot wire type vortex detector 2 is arranged in the downstream side of the vortex body placed in a flowline and a current is supplied to said hot wire type vortex detector 2 by a current amplifier 7. A bridge circuit 1 generates an output signal corresponding to the generation frequency of a Karman vortex from the change in the resistance of the hot wire type vortex detector 2 and outputs the same to BPF8 through a differential amplifier 6. BPF8 permits only the passage of vortex generation frequency and supplies said frequency to an AC amplifier 11. The AC amplifier 11 amplifies said vortex signal to output the same to a terminal C through a comparator 17. A change- over switch 13 is provided to the feedback route of the amplifier 11 and changed over corresponding to the output of a flow amount discrimination circuit 14, that is, the sucking amount of air to alter the amplifying degree of the amplifier 11 to the value corresponding to the sucking amount of air. |
