Method and apparatus for measuring flow velocity and method and apparatus for measuring flow rate

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. A flow velocity measuring apparatus is realized by hardware having the functions of the above steps. A flow rate is obtained by multiplying the measured flow velocity with the internal diameter of a tube member.