The devices are equipped with a spring-loaded piston located in a cylindrical measuring tube with a defined orifice. When the STAN-P is in operation, the medium moves the piston against the restoring force of the spring, so that the piston position is directly dependent on the volumetric flow rate.

A magnet integrated into the piston transmits the movement contactlessly to a mechanical indicator mounted externally on the housing, enabling immediate reading of the flow rate from the scale.

A bistable reed switch (normally closed), mounted externally on the housing, closes when the magnetized piston passes. The monitored flow rate (switching point) can be continuously adjusted by moving this switch along an external scale.

The actual flow may exceed the set measuring range without damaging the device; however, pressure loss will increase.

The devices must only be operated with particle-free fluids and must be kept free from magnetic influences.