flowmeter in which a tapered plug fits into a circular orifice in such a way that the area of the annular space is proportional to the lift of the plug, voomõõtur, mille kooniline kork/kolb sobib ümmarguse avaga nii, et moodustuv rõngakujulise ruumi pindala on proportsionaalne korgi tõusukõrgusega