| 摘要 |
<p>A sonic-type fluid flow measuring system wherein reflections or echoes of a burst (103) of ultrasonic energy from an ultrasonic acoustic emitter (9a) are sensed and typically comprise a number of frequencies representative of a number of discrete velocities of flow in a volume of fluid. A receiver transducer (13a) is gated to receive echoes from a selected volume of fluid (104) at a selected distance from a transducer (13a). Thereafter, this time domain signal sample is converted to a frequency domain sample whereby the presence and magnitude of each frequency component, or velocity component, is isolated, this being typically done by what is known as a Fast Fourier Transform unit, obtaining a frequency domain waveform representative of average flow velocity.</p> |
