| 摘要 |
A conventional flow velocity measuring apparatus constituted as an important element of almost flowmeter is subject to operate based on an ultrasonic transmitting time difference method, but it causes the larger measuring error of the ultrasonic transmitting time, because the intensity of the ultrasonic pulse is severely pulsated at the receiving point due to the fluid sate under the condition of transmitting and receiving the ultrasonic pulse, the concentration change of suspension particles, etc. A flow velocity measuring apparatus is to measure an ultrasonic transmitting time, transmitting and receiving ultrasonic continuous sinewave frequencymodulated in turn to time, in which one frequency discriminator detects the moment that a frequency of the ultrasonic beam is modulated upon the transmitting and receiving. Therefore, the error caused due to the detecting delay time is removed, because one frequency discriminator detects the receiving and transmitting signals, and the ultrasonic transmitting time measuring error is prevented, even through the amplitude of the receiving signal is severely pulsated. The flow velocity :measuring apparatus can be effectively used in an ultrasonic flowmeter for a larger calibration pipe and a larger river or sluice open channel.
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