| 摘要 |
Fluid flow measuring apparatus comprises two ultrasonic transducers (1, 2) between which an ultrasonic energy beam is transmitted through the fluid. The beam is frequency modulated (4, 5) by an audio signal, and the relationship between the frequency or phase of the received modulation signal (6, 7, 8) and that of the transmitted modulation signal gives a measure (10) of the speed of flow of the fluid. Beams of ultrasonic energy are preferably fed in two mutually opposite directions, for example by switching (3) the transducers to act alternately as transmitter and receiver, and the measurement is computed from the two relationships. An anemometer (FIG. 7) comprises two such systems arranged to produce mutually perpendicular ultrasonic beams, and a computer (25) to compute wind speed (28) and direction (29) from the frequency or phase relationships. |
