The valve positioner (also known as: pneumatic valve positioner) is the main accessory of the control valve. It is usually used in conjunction with the pneumatic control valve. It receives the output signal of the regulator, and then uses its output signal to control the pneumatic control valve. After the action, the displacement of the valve stem is fed back to the valve positioner through the mechanical device, and the valve position status is transmitted to the upper system through electrical signals.

In many control applications, the valve positioner is one of the most important accessories of the control valve. Especially for a specific application, if you want to choose the most suitable valve positioner, you should pay attention to the following factors:

1) Is it easy and convenient for the valve positioner to realize "Split_ranging" and "Split_ranging"? With the "split range" function, it means that the valve positioner only responds to a certain range of the input signal (for example: 4～12mA or 0.02～0.06MPaG). Therefore, if it is possible to "split range", it is possible to control two or more regulating valves one after the other with only one input signal according to actual needs.

2) Is it easy and convenient to adjust the zero point and range of the positioner? Can the zero point and span adjustment be completed without opening the box cover? But it is worth noting that: sometimes in order to avoid incorrect (or illegal) operations, this way of adjusting at will need to be prohibited.

3) How stable is the zero point and span of the valve positioner? If the zero point and span are prone to drift with changes in temperature, vibration, time or input pressure, the valve positioner needs to be re-adjusted frequently to ensure that the stroke action of the regulating valve is accurate.

4) The accuracy of the valve positioner is under ideal working conditions, corresponding to a certain input signal, the trim parts of the regulating valve (TrimParts, including sphere/spool, valve stem, valve seat, etc.) should be accurately positioned at the required level each time Regardless of the direction of the stroke or how much load the internal parts of the regulating valve bear.