Flowmeter

A flowmeter is an apparatus intended to measure the Débit of a fluid (liquid or gas);

According to the level of the flow, and the nature of the fluid, the principle of the adapted flowmeter is very variable;

some are based to the measure of the Speed of the fluid; one will use in this case a Tube of Pitot, a Débitmètre with turbine, a Débitmètre with ultrasounds, a ionic Débitmètre.
one can also use the measurement of the Pressure loss (loss of pressure) or differential pressure between a reference mark upstream and a reference mark downstream, this using a Plaque with opening, of a conduit (like in the case of a Débitmètre with tube of Venturi), of a electromagnetic Ratemeter or a Débitmètre for purpose vortex.
there exists also the mass Débitmètre.
finally, one can use the fluid to involve mobile mechanical devices quantitatively:

See also