A positioner is used to adjust the position of a linear or rotary valve actuator, in response to a signal received from a controller. They are very precise and thus are frequently used in control applications to increase response speeds and allow for quicker loading and venting. A positioner is mechanically connected to the stem or shaft of a valve, allowing a comparison of its actual position with the position programmed by the controller. If this position is different, the valve positioner conveys necessary feedback to the controller, which then moves the actuator until it reaches the correct position.
Valve positioners are available in several different types: