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When it comes to valve positioners, I believe many front-line instrument workers know it. As the core auxiliary accessory of the regulating valve, it mainly improves the flow characteristics of the regulating valve to improve the positioning accuracy and reliability of the regulating valve. Now it has been widely used in many fields and occasions. There are many brands of valve positioners on the market, such as Fisher positioner from the United States, Siemens positioner from Germany, ABB positioner from Switzerland, and Yamatake positioner from Japan, all of which are world-renowned valve positioner brands. According to structure, valve positioners can be divided into pneumatic valve positioners, electro-pneumatic valve positioners and intelligent valve positioners. With so many brands and types available, when we choose to buy a valve positioner, we must choose the one that suits us. Today, the technical editor will explain to you what you need to pay attention to when choosing a valve positioner. Note 1. The accuracy of the positioner of large-load valves. Under ideal working conditions, corresponding to a certain input signal, the trim parts of the regulating valve (TrimParts, including the ball/valve core, valve stem, valve seat, etc.) should be accurately positioned at the required position every time, regardless of the direction of the stroke or how much load the trim parts of the regulating valve bear. Note 2. How stable is the zero point and range of the valve positioner? If the zero point and span are prone to drift with changes in temperature, vibration, time or input pressure, then the valve positioner needs to be recalibrated frequently to ensure that the control valve's stroke action is accurate. Note 3. Is it easy and convenient to adjust the zero point and range of the positioner? Is it possible to complete the zero point and span adjustment without opening the box cover? But it is worth noting that: Sometimes in order to avoid incorrect (or illegal) operation, this random adjustment method needs to be prohibited. Note 4. Whether the valve positioner can achieve "Split"_ranging)" Whether the valve positioner can achieve "Split_ranging)" is it easy and convenient to achieve "dividing" ； Having the "split range" function means that the valve positioner only responds to a certain range of the input signal (such as: 4～12mA or 0.02～0.06MPaG) with response. Therefore, if it can be "divided", only one input signal can be used to control two or more control valves one after another according to actual needs. The above content is what we are going to talk about today: "What necessary matters should be paid attention to when selecting a valve positioner". I hope that through today’s explanation, we can help our instrument workers to make a good choice of valve positioner, so that we can better match the needs of our regulating valves and actual working conditions in future use.