device which is inserted in a conduit to create a pressure difference the measurement of which, together with a knowledge of the fluid conditions and of the geometry of the device and the conduit, enables the flow-rate to be calculated, seade, mis sisestatakse torusse rõhuerinevuse tekitamiseks, mille mõõtmine koos vedeliku tingimuste ja seadme ning toru geomeetria tundmisega võimaldab arvutada voomahtu