What is a Valve Positioner?

As a common control valve accessory, the valve positioner delivers pressurized air to the valve actuator so that the position of the valve stem or shaft corresponds to the set point from the control system. Valve positioners are typically pneumatic or analog I/P and are used when a valve requires throttling action. They require position feedback from the valve stem or shaft and deliver pneumatic pressure to the actuator to open and close the valve