Valve positioner, according to the structure of pneumatic valve positioner, electric-pneumatic valve positioner and intelligent valve positioner, is the main accessory of regulating valve, usually used with pneumatic regulating valve, it accepts the output signal of regulator, and then control the pneumatic regulating valve with its output signal, when the regulating valve moves, the displacement of valve stem is fed back to the valve positioner through mechanical device, and the valve position condition is transmitted to the upper system through electric signal.
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