Abstract: An flow rate measurement method and a ultrasonic flow meter is provided, which can measure a flow velocity accurately by utilizing a ultrasonic wave having a frequency by which a phase difference becomes zero. According to the flow rate measurement method, a reference ultrasonic velocity is prepared such that the fluid is in a standard condition, firstly. Then, an absolute ultrasonic velocity in the fluid and a temporary flow velocity V0 in the fluid are obtained. Then, the temporary flow velocity V0 is corrected by using the difference between the reference ultrasonic velocity and the absolute ultrasonic velocity thereby to determine an accurate flow velocity of the fluid, and to determine a flow rate of the fluid by using the accurate flow velocity and a cross section area of the conduit.

Abstract: Disclosed is a method and apparatus for measuring flow velocity and flow rate of a fluid in a tube member or the like with high precision. A flow vel0ocity measuring method has: a step of allowing a signal sound of ultrasound to propagate through a fluid in a tube member or the like and detecting a phase difference between the signal sound and an original signal; a step of eliminating a phase difference detected in the step to obtain synchronism; a step of detecting time or oscillation frequency required to complete the phase synchronization in the step; and a step of, on the basis of the time or oscillation frequency required to complete phase synchronization in the step, calculating flow velocity by referring to flow velocity which is preset in a table in correspondence with the time or frequency. In the table, flow velocities corresponding to changes in temperature, pressure, and kind of a fluid may be preset together with the time or oscillation frequency.

Abstract: Disclosed is a method and apparatus for measuring flow velocity and flow rate of a fluid in a tube member or the like with high precision. A flow vel0ocity measuring method has: a step of allowing a signal sound of ultrasound to propagate through a fluid in a tube member or the like and detecting a phase difference between the signal sound and an original signal; a step of eliminating a phase difference detected in the step to obtain synchronism; a step of detecting time or oscillation frequency required to complete the phase synchronization in the step; and a step of, on the basis of the time or oscillation frequency required to complete phase synchronization in the step, calculating flow velocity by referring to flow velocity which is preset in a table in correspondence with the time or frequency. In the table, flow velocities corresponding to changes in temperature, pressure, and kind of a fluid may be preset together with the time or oscillation frequency.

Abstract: An flow rate measurement method and a ultrasonic flow meter is provided, which can measure a flow velocity accurately by utilizing a ultrasonic wave having a frequency by which a phase difference becomes zero. According to the flow rate measurement method, a reference ultrasonic velocity is prepared such that the fluid is in a standard condition, firstly. Then, an absolute ultrasonic velocity in the fluid and a temporary flow velocity V0 in the fluid are obtained. Then, the temporary flow velocity V0 is corrected by using the difference between the reference ultrasonic velocity and the absolute ultrasonic velocity thereby to determine an accurate flow velocity of the fluid, and to determine a flow rate of the fluid by using the accurate flow velocity and a cross section area of the conduit.