| 摘要 |
A flow transducer of the turbine type comprises a tube (11) of plastics or glass through which flows liquid to be measured. Mounted within the tube 11 is a helically vaned rotor (28) whose rotation is sensed by light emitting and photosensitive devices (40, 41) located on opposite sides of the tube (11). The devices (40, 41) are disposed and directed, and the refractive index of the tube (11) is chosen so that light from the light emitting device (40) will be received by the device (41) when liquid is present in the tube and not received when there is an air or vapour bubble present. Preferably, the devices are located in line directly opposite each other and the refractive index of the tube (11) is substantially the same as that of the liquid whose flow is to be measured. |
