| 摘要 |
A flow meter for measuring the velocity of surrounding fluid, comprising a rotatable member rotatably coupled to a shaft member, wherein the shaft member comprises a measuring electrical circuit comprising an AC power supply and a primary coil, the rotatable member comprising a passive non-permanent magnet marker responsive to a magnetic field, the arrangement being such that when the circuit is powered by the AC supply the coil generates a magnetic field and the marker is positioned on the rotatable member such that rotation of the rotatable member in response to fluid drag on the member causes the distance between the marker and the coil to oscillate, the marker interacting with the magnetic field at its closest approach to the coil, thereby to cause a measurable electrical response in the circuit. Thus, the speed of rotation of the rotatable member can be determined by measuring an electrical response in the circuit without physically contacting the rotatable member and without involving a permanent magnet is provided. |
