CHX900 Intelligent Electrical Valve Positioner Suitable for Pneumatic Control Valve Systemsw Product Summary The CHX900 intelligent valve positioner is a dual line instrument based on piezoelectric valve technology. It receives 4-20mA current control signals and accurately controls valve opening through the processing of a built-in high-performance microprocessor. The device adopts fuzzy PID optimal control internally and supports 4-20mA valve opening transmission function.