| 摘要 |
PROBLEM TO BE SOLVED: To effectively reduce influence of noise due to reflection or reverberation of ultrasonic waves in a flow passage in a pulse Doppler ultrasonic flow meter. SOLUTION: In this ultrasonic flow meter, scattered waves generated when ultrasonic waves 4 emitted from an ultrasonic wave transmitting/receiving means 3 are scattered in fluid are received in a plurality of measurement positions individually with gate time control by means of a gate circuit 15, and on the basis of Doppler deviation caused in the received scattered wave in each of the measurement positions, a flow velocity distribution in the flow passage is found, and then, a flow rate is found from the flow velocity distribution. The ultrasonic flow meter is provided with a storing means 11 taking in a signal waveform of noise due to reflection or reverberation of ultrasonic waves and storing it as a canceling noise signal and a computing means 13 finding a difference between a measured signal and the canceling noise signal, and a noise signal can be removed from the measurement signal by this differential processing.
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