| 摘要 |
By means of sonic or ultrasonic energy, flow rate is determined as a linear function of the difference between two frequencies by taking measurements in the direction of flow and in the direction opposite thereto. Transducers are used alternately as generators and pickups. To this end, the transit time difference is determined by means of a phase detector, and the frequencies of two oscillators are readjusted in accordance with the results of the measurements. The difference frequency can be indicated and calibrated in flow rate, and the number of cycles can be counted, the flow volume being directly proportional thereto.
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