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

A flow velocity measuring method for measuring flow velocity of a fluid that flows, comprising:

• a step of allowing a signal sound to propagate to the upstream or downstream side in a fluid and detecting a phase difference between the signal sound and an original signal;
• a step of eliminating a phase difference detected in the step and svnchronizing the phases;
• a step of detecting time or oscillation frequency required to complete the phase synchronization in the step;
• and
• a step of calculating flow velocity of the fluid with reference to flow velocity preset in correspondence with the time or oscillation frequency on the basis of the time or oscillation frequency required to complete the phase synchronization in the step,
• wherein phase difference detection performed by making signal sound propagate to the upstream side in the fluid and phase difference detection performed by making signal sound propagate to the downstream side in the fluid are alternately switched, and a calibration signal is output at the time of switching to prevent a fluctuation at the time of switching.

A flow velocity measuring apparatus for measuring flow velocity of a fluid which flows, comprising:

• a plurality of signal sound transmitting/receiving units disposed in a fluid that flows, for transmitting/receiving a signal sound;
• a phase difference detecting unit for detecting a phase difference between a signal sound properly transmitted and received by the plurality of signal sound transmitting/receiving units to thereby allow the signal sound to propagate to the upstream or downstream side in the fluid and the original signal;
• a phase synchronizing unit for eliminating a phase difference detected by the phase difference detecting unit to obtain synchronization;
• a detecting unit for detecting time or oscillation frequency required to complete the phase synchronization in the phase synchronizing unit;
• and
• a flow velocity calculating unit for calculating flow velocity of the fluid by referring to, on the basis of the time or oscillation frequency detected by the detecting unit, flow velocity which is preset in correspondence with the time or oscillation frequency.

A flow rate measuring method comprising:

• a step of allowing a signal sound to propagate to the upstream or downstream side in a fluid and detecting a phase difference between the signal sound and an original signal;
• a step of eliminating a phase difference detected in the step and synchronizing the phases;
• a step of detecting time or oscillation frequency required to complete the phase synchronization in the step;
• and
• a step of calculating flow velocity of the fluid with reference to flow velocity preset in correspondence with the time or oscillation frequency on the basis of the time or oscillation frequency required to complete the phase synchronization in the step;
• and
• a flow rate measuring step of measuring a flow rate by multiplying the flow velocity obtained in the flow velocity measuring step with an internal diameter of a tube member through which a fluid flows.