Valve positioners are classified into pneumatic valve positioners, electrical valve positioners and intelligent valve positioners according to input signals. The input signal of the pneumatic valve positioner is a standard gas signal, for example, a 20~100kPa gas signal, and its output signal is also a standard gas signal. The input signal of the electric valve positioner is a standard current or voltage signal, for example, 4-20mA current signal or 1~5V voltage signal, etc. The electric signal is converted into electromagnetic force inside the electric valve positioner, and then the air signal is output to the toggle Control valve.

According to the direction of action, it can be divided into one-way valve positioner and two-way valve positioner. When the one-way valve positioner is used in a piston type actuator, the valve positioner only works in one direction, and the two-way valve positioner acts on both sides of the cylinder of the piston type actuator and works in two directions.

According to the gain sign of the valve positioner output and input signal, it is divided into positive acting valve positioner and reverse acting valve positioner. When the input signal of a positive-acting valve positioner increases, the output signal also increases, so the gain is positive. When the input signal of the counteracting valve positioner increases, the output signal decreases, so the gain is negative.

According to the input signal of the valve positioner is analog signal or digital signal, it can be divided into ordinary valve positioner and fieldbus electric valve positioner. The input signal of ordinary valve positioner is analog air pressure or current, voltage signal, and the input signal of field bus electrical valve positioner is the digital signal of field bus.