Massflow under control
Mass flow gas measurement is independant of temperature and pressure, thus controlling a process gas can be stable and reproduceable. Mass flow controllers contain a PID-controller and can be driven through norm signal or field bus. Mass flow meters are without actuators and are only for measuring massflow.
Control valve strokes proportionally
Positioning valves can be combined with pneumatic, motorized, piezoelectric or solenoid actuators. The main differences between the various actuation principles are type of media separation, dynamic and force properties. Solenoid-operated positioning valves are known in practice as proportional valves and cover the nominal diameter range below 25 mm. Open and closed control loops can be developed using proportional valves. Open control loops control the valve without feedback signal, while closed control loops control the difference between the set-point and actual values. Switching solenoid valves, which are normally closed, form the basis for Bürkert proportional valves. Direct-acting proportional valves receive their feed below their seat, while servo-assisted models receive their feed above their seat.
MFC/MFM And Proportional Valves