| 摘要 |
Apparatus is provided for measuring the velocity of a fluid, which may be, for example, a liquid, gas, blood or slurry, in a conduit which may, for example, be in the form of a pipe, tube, trough, or vessel. The velocity is measured by transmitting sonic power of frequency varying linearly with time, one electro-acoustic transducer being disposed at an upstream site and a second electro-acoustic transducer at a downstream site. In accordance with the theory of this invention account is taken of the signals in the fluid and also in the walls of the conduit. Associated with the transducers are driving and receiving circuits, the latter performing bandpass-amplification, envelope detection and processing of the fluctuations in the envelopes of the received signals to measure the periods or frequencies in upstream and in downstream transmission and to further determine and display the difference of the periods or frequencies as a voltage or number proportional to fluid velocity.
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