How to choose electro pneumatic valve positioner
The first or economic considerations, the second is to achieve the requirements, and the third is to be durable. This is the basic criterion. Then select a in-depth understanding of the electrostatic valve positioner.
The valve positioner is divided into pneumatic valve positioner, an electro pneumatic 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, 20 to 100 kPa gas signal, and its output signal is also a standard gas signal. The input signal of the electro pneumatic valve positioner is a standard current or voltage signal, for example, 4 to 20 mA current signals or 1 to 5V voltage signals, etc., convert the electrical signal into electromagnetic force inside the electro pneumatic valve positioner, and then outputs gas signal to the dial Control valve. The intelligent electro pneumatic valve positioner converts the current signal output by the control chamber into a gas signal of the drive regulating valve. According to the modulating valve, the valve bar is frictional, and the imbalance generated by the medium pressure fluctuation, so that the valve opening degree corresponds to the control. Room output current signal. And the intelligent configuration settings can be performed to improve the purpose of improving the performance of the control valve. According to the direction of action, it can be divided into a one-way valve positioner and a two-way valve positioner. When a one-way valve positioner is used for a piston-type executive mechanism, the valve positioner acts only in one direction, and the bidirectional valve positioner acts on both sides of the piston-type actuator cylinder, in two directions. The gain symbols of the valve positioner output and the input signal are divided into positive acting valve positioners and reaction valve positioners. When the input signal of the valve positioner increases, the output signal also increases, and therefore, the gain is positive. When the input signal of the counter valve positioner increases, the output signal is reduced, so the gain is negative. Press the valve positioner input signal is an analog signal or a digital signal, which can be divided into a normal valve positioner and a fieldbus electrostatic valve positioner. The input signal of the ordinary valve positioner is an analog air pressure or current, a voltage signal, and an input signal of the fieldbus electro pneumatic valve positioner is a digital signal of the fieldbus. Press the valve positioner whether or not the CPU can be divided into a normal electro pneumatic valve positioner and a smart electro pneumatic valve positioner. The normal electro pneumatic valve positioner does not have a CPU, so it does not have intelligence and cannot handle related intelligent operations. Intelligent electro pneumatic valve positioner with CPU, can handle intelligent operations, for example, nonlinear compensation such as forward channels, etc., fieldbus electro pneumatic valve positioners can also bring PID and other functional modules to achieve corresponding operations. Classification can also be performed by the detection method of the feedback signal. For example, the valve positioner of the valve position signal is detected by the mechanical link mode: the method of detecting the valve bar displacement by the Horn effect detection of the valve positioner: detecting the valve positioner of the valve rod displacement by the electromagnetic induction method.
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