Gear flow meters (ZHM) are positive displacement meters. Two precise gears rotate freely inside the measuring chamber. Sealed cavities are created between the gears and the housing. The measured media causes the rotation of the gears. The flowing medium is distributed evenly in the measuring chamber and causes the rotation of the gears. The gear wheels rotate freely and undamped in the media flow. Their rotational frequency is proportional to the flow rate and is measured by non-intrusive sensors (pickups) through the housing wall.

These meters are suitable for accurate measurement of different liquids with viscosities of approximately 1 to 25,000 mm²/s.