Positive displacement measurement is based on dividing a flowing stream into known, repeatable portions. In a perfect flow meter, the displacement chambers would form and collapse without any liquid seeping between the moving parts. In a Max meter we have nearly achieved this level of perfection. First, we build our meters with a 0.0002” gap between the moving parts so that liquid cannot escape from the measurement chamber. Next, we support all of the moving parts on ball bearings so they turn smoothly without requiring a large pressure drop to make the meter turn. Finally, we seal the measurement chambers with a no-friction liquid seal that does not create any drag in the meter’s rotation. The sum of all of these refinements is a very low pressure drop which boosts the volumetric efficiency of the meter to more closely approximate the perfect meter.
See our sample calibration sheet (pdf).