1. Pneumatic valve positioner: Pneumatic valve positioner accepts standard gas signal as input, such as 20~100kPa gas signal. It adjusts the output air signal to the actuator according to the input signal, thus controlling the valve position. Pneumatic valve positioner usually works according to the principle of torque balance, when the input signal changes, through the internal mechanical structure to change the output gas pressure, so that the actuator action.

2. Electrical valve positioner: Electrical valve positioner accepts standard current or voltage signal as input, such as 420mA current signal or 15V voltage signal. Inside the electrical valve positioner, the electrical signal is converted into an electromagnetic force, which then outputs a gas signal to the actuator. Electrical valve positioners typically have higher accuracy and stability and can be adjusted and calibrated electronically.

3. Intelligent Valve Positioner: Intelligent Valve Positioner comes with a CPU that can handle intelligent arithmetic and advanced control functions. It not only receives and converts signals, but also performs self-diagnostics, adaptive control and other functions. Intelligent valve positioners usually have higher performance and more functions, and are suitable for occasions with higher requirements for control accuracy and stability.