The valve positioner is divided into a pneumatic valve positioner, an electric valve positioner and a smart valve positioner according to the input signal. The input signal of the pneumatic valve positioner is a standard gas signal, for example, a 20~100kPa air signal, and the 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, a 4~20mA current signal or a 1~5V voltage signal, etc., the electric signal is converted into an electromagnetic force inside the electric valve positioner, and then the gas signal is output to the toggle. Control valve. The intelligent electric valve positioner converts the current signal outputted by the control chamber into a gas signal for driving the regulating valve. According to the frictional force of the valve stem when the regulating valve is operated, the unbalanced force generated by the fluctuation of the medium pressure is offset, so that the valve opening degree corresponds to the control. The current signal output from the room. And the intelligent configuration can be set to the corresponding parameters to achieve the purpose of improving the performance of the control valve.

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

The gain symbol of the valve positioner output and the input signal is divided into a positive acting valve positioner and a reaction valve positioner. When the input signal of the positive acting valve positioner increases, the output signal also increases, so the gain is positive. When the input signal of the reaction valve positioner increases, the output signal decreases, so the gain is negative.

The input signal according to the valve positioner is an analog signal or a digital signal, which can be divided into a common valve positioner and a field bus electric valve positioner. The input signal of the ordinary valve positioner is analog air pressure or current, voltage signal, and the input signal of the field bus electric valve positioner is the digital signal of the field bus.

According to whether the valve positioner with CPU can be divided into ordinary electric valve positioner and intelligent electric valve positioner. Ordinary electric valve positioners do not have a CPU, so they are not intelligent and cannot handle related intelligent calculations. The intelligent electric valve positioner with CPU can handle intelligent calculations. For example, it can perform nonlinear compensation of the forward channel. The field bus electric valve positioner can also carry functional modules such as PID to realize the corresponding calculation.

The detection method according to the feedback signal can also be classified.

For example, a valve positioner that detects a valve position signal by a mechanical linkage method: a valve positioner that detects a displacement of a valve stem by a method of detecting a displacement by a Hull effect: a valve positioner that detects a displacement of a valve stem by an electromagnetic induction method.

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