| 摘要 |
PROBLEM TO BE SOLVED: To provide a ultrasonic flowmeter, which is simple and low cost have a small current consumption and which can accurately detect the flow rate change frequency and a flow rate, and to provide a flow rate change detector for the ultrasonic flowmeter used therefor. SOLUTION: The flow rate change detector for the ultrasonic flowmeter comprises a transmitting circuit 5 for repeating the transmission and the reception of the ultrasonic waves in a faster period than that of the changing flow rate occurring in the flow by transmitting and receiving the wave between at least two vibrators 1 and 2 provided at the upstream side and the downstream side to the flow, a receiving wave detector 7, a time-measuring circuit 9 and a microcomputer 10 for detecting the fluctuation period of the flow rate, based on the propagation times of the transmitted and received ultrasonic waves.
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