Piston flow meters are direct volume counters, also called displacement counter (positive displacement meter).Its function is based on continuous limitation of a definite part-volume of the flow in a measuring cell through continu-ous filling and emptying of this measuring cell. The measuring cell consists of the measuring chamber and the moving part, the piston.
The piston is driven by the pressure difference between inlet and outlet of the measured media. The revolution is carried forward via a magnet and a magnet field sensor.
In cross section the u-formed piston is guided with its piston-and guiding-adaptor in a ring chamber at the bottom and top of the measuring-body and also with its slot at the baffle.
The inlet and outlet openings are located on both sides of the chamber’s wall. They are constantly sealed by the piston and the baffle.
The incoming measured media fills up the sickle shaped space, it wants to increase this space and therefore turns the piston, until one after the other the volumes V1 and V2 are reached. While moving ahead, these filled spaces get connected with the outlet and are emptied. Since both sickle shaped spaces - the inner and the outer - are displaced to one another, the piston movement will not have a dead center. The piston moves continuously depending to the measured flow.