DRZ
page 4
DRZ K03/0418
5. Operating
Principle
KOBOLD 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 continuous 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 counter is a pure mechanical instrument. 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-adapter in a ring chamber at
the bottom and top of the measuring-body and 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 spaces, it wants to increase these spaces and therefore
turns the piston. Until one after the other the volumes V1 and V2 are reached.
While moving ahead, these filled spaces are 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 centre. The
piston moves continuously depending to the measured flow.
One complete turn of the piston adapter end is equal to the flow of the measuring
chamber content (V1+V2). With the help of a located magnet and a Hall-type
sensor, it is possible to create a digital signal, which can be evaluated.
