| 摘要 |
An ultrasonic flow velocity measuring method comprises an ultrasonic transit time difference flow velocity measuring method, without transmitting/receiving an ultrasonic pulse and measuring the ultrasonic transit time if a flow velocity is measured in a river, an open sluice way channel and a pipe of a larger inner diameter based on the ultrasonic transit time difference method, including steps of amplitude-modulating a continuous ultrasonic sinewave f C into a frequency f M, transiting/receiving the amplitude-modulated signal and using the amplitude-modulation wave in measuring the ultrasonic transit time; and a phase difference flow velocity measuring method irrelevant to the change of the sound velocity, if the flow velocity is measured based on the phase difference method, including steps of amplitude-modulating an ultrasonic wave into a predetermined frequency f M, if a phase difference .DELTA.~C transited in the directions similar and contrary to the flow velocity is equal to n.pi. + a.pi., obtaining n.pi. using the signal f M and measuring a part a.pi. in that a.pi. < .pi., obtaining the phase difference between the signals f C and obtaining the total phase differences .DELTA.~C, precisely.
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