Continuously adjustable valves generally have internal feedback of force and position feedback, which monitor the position in a corresponding to ensure the most precise possible correlation between the setpoint and the actual value (exception: simple proportional valves and single-layer servo valves).
Primarily, three systems are used as feedback systems for continuously adjustable valves:
- Barometric feedback– the simplest form of feedback.
- Mechanical feedback – primarily used in servo valves.
- Electric feedback– primarily used in proportional valves.
The type of feedback system has a very strong impact on the dynamic behaviour of the internal (Figure R 37).
Figure R 37: Effect of the type of feedback on the bode diagram