What factors should we consider when choosing a valve positioner?

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　　As is well known, valve positioners are one of the very important valve accessories in many applications. It is usually used in conjunction with pneumatic control valves. Its working principle is as follows: it receives the output signal from the controller, and then uses this signal to control the pneumatic control valve. When the control valve operates, the displacement of the valve stem is fed back to the valve positioner through a mechanical mechanism, and the valve position is transmitted to the higher-level system via electrical signals. Due to the numerous design parameters involved in selecting valve positioners, and considering the specific conditions of our actual operating environments, it is essential to choose a valve positioner that meets our actual needs. Therefore, it is important to pay attention to certain key factors when making such a selection! So, what factors should we consider when choosing a valve positioner? Today, we’ll give you a general overview. 　　Firstly, the valve positioner is subject to high loads. Under ideal operating conditions, for a given input signal, the internal components of the control valve (trim parts, including the ball/valve element, valve stem, valve seat, etc.) should always be positioned accurately at the desired location, regardless of the direction of movement or the amount of load on these internal components. 　　Secondly, what is the stability of the zero point and range of the valve positioner? 　　If the zero point and range of the valve positioner tend to drift due to changes in temperature, vibration, time, or input pressure, then the valve positioner needs to be recalibrated frequently to ensure that the actuation of the control valve is accurate. 　　Third, is it easy and convenient to adjust the zero point and range of the valve positioner? 　　Can the zero and span adjustments of the valve positioner be done without opening the cover? However, it is worth noting that sometimes, in order to avoid incorrect (or illegal) operations, such arbitrary adjustment also needs to be prohibited. 　　Fourth: Can the valve positioner achieve “split-ranging”? Can the valve positioner perform split-ranging? Is it easy and convenient to achieve “segmented routing”? ； The \"range division\" function means that the valve positioner responds only to a certain range of the input signal (e.g., 4–12 mA or 0.02–0.06 MPaG). Therefore, if it is possible to divide the process into stages, it is feasible to use just one input signal to control two or more control valves in sequence, depending on actual needs. The above are the key points we should keep in mind when choosing valve positioners today. It is hoped that by learning about the considerations for selecting valve positioners today, we can all choose the ideal valve positioner that suits our needs.