| 摘要 |
An ultrasonic flow velocity measuring method comprises a phase difference flow velocity measuring method irrelevant to the change of the sound velocity, if a flow velocity is measured based on a phase difference method without transmitting/receiving an ultrasonic pulse in a river, an open sluice channel or a pile having a large inner diameter, including amplitude-modulating at least one continuous ultrasonic sine waves of a carrier frequench ƒC into signals of an amplitude-modulated frequench ƒM, if at least one phase difference DELTAphiC transited and received in directions similar and contrary to the flow velocity is equal to npi+api, obtaining npi, using the signal of the amplitude-modulation ƒM; and measuring a part of api<pi, obtaining the phase difference between the signals of the carrier frequench ƒC and obtaining the total phase differences DELTAphiC precisely.
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