How PD meter measures flow 1. Fluid enters the inlet. 2. Fluid fills the spaces between gear teeth and casing. 3. Flow forces the gears to rotate. 4. A fixed volume is trapped in each gear cavity. 5. Trapped fluid is carried around the gear perimeter. 6. Tight clearances prevent backflow through the center. 7. Gear teeth re-mesh at the outlet. 8. Trapped fluid is displaced out of the meter. 9. Each gear rotation equals a known volume. 10. Rotations are counted by the sensor. #instrumentation #pr