A Displacement Volumetric Meter is a device which measures total volume. It can operate on the principle of the fluid sweeping out a fixed calibrated volume, which produces a rotation of a calibrated gauge. By maintaining constant conditions and taking readings over a prescribed period the flow rate can be calculated for the specific operating conditions. The instrument essentially measures total volume.
Some water meters work on the principal to measure fixed volumes of water for billing. These are commonly referred to as "positive displacement meter".