| 摘要 |
An ultrasonic Doppler flowmeter in which a received signal processing part includes a reference signal generator for generating a reference signal corresponding to the magnitude of a received signal, and a comparator for comparing the received signal with the reference signal. The reference signal varies in accordance with the magnitude of the received signal, and further may possess a hysteresis width corresponding to the output of the comparator. Therefore, a noise signal is effectively removed from the received signal at the comparator, and only a Doppler shift frequency is detected.
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