| 摘要 |
PROBLEM TO BE SOLVED: To provide an ultrasonic flow velocity measuring method capable of precisely obtaining the propagation time of ultrasonic waves and capable of precisely measuring a flow velocity without utilizing short-period clock waves when obtaining the propagation time of the ultrasonic waves by utilizing clock waves. SOLUTION: In this measuring method, the period from the time A when ultrasonic waves are transmitted to the time B when clock waves L rise immediately before a first zero-cross time D of received waves W is obtained by counting the clock waves L outputted simultaneously with the transmission of the ultrasonic waves. The fraction period Tx from the time B when the clock waves L rise immediately before the first zero-cross time D of the received waves W to the zero-cross time D of the received waves W is obtained based on the voltage value ratio V2/V1 of the received waves W at the rise time B and rise time C of the received waves W. When the period T and the fraction period Tx are added, the propagation timeπof the ultrasonic waves is accurately obtained, and the flow velocity can be precisely measured. |
