The positioner is the main accessory of the valve. It is usually applied with the pneumatic valve. It receives the output signal of the regulator and then controls the pneumatic valve with its output signal. When the valve moves, the displacement of the valve stem is fed back to the positioner through the mechanical device, and the status of the valve position is transmitted to the upper system through the signal.
The positioner is the main accessory of the valve. It takes the displacement signal of the valve stem as the input feedback measurement signal and the output signal of the controller as the setting signal. When there is a deviation between the two signals, it changes the output signal to the actuator to make the actuator act, and establishes the one-to-one correspondence between the displacement multiple of the valve stem and the output signal of the controller. Therefore, the positioner consists of a feedback control system which takes the displacement of the valve stem as the measurement signal and the output of the controller as the setting signal. The control variable of the control system is the output signal of the locator to the actuator.