In gear flow meters, closed, medium-filled cavities are created between the teeth and the housing. The flowing measuring medium causes the gear pair to rotate freely and without braking. Turbine flowmeters measure using a high-precision turbine wheel. The medium flows against the turbine wheel in the axial direction and makes it rotate. In screw flow meters, the volume flow of the fluid is measured using the screw wheel principle. Inside the housing are two overlapping screw spindles. Media-filled cavities are created between the flanks of the spindle and the housing.