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The intelligent valve positioner (http://yunrun.com.cn/tech/2358.html) consists of a signal conditioning section, a microprocessor, an electro-pneumatic conversion control section, and a valve position detection and feedback device, as shown in Figure 1. The input signal can be a 4-20mA signal or a digital signal. http://yunrun.com.cn/upload/201901/27/201901272205434164.png Figure 1: Block diagram of the principle of the intelligent valve positioner. The signal conditioning section converts the input signals and valve position feedback signals into digital signals that can be processed by the microprocessor. The microprocessor processes and compares these two digital signals to determine whether the valve opening corresponds to the input signal, and then outputs a control electrical signal to the electro-pneumatic conversion control unit, which converts it into a pneumatic signal that drives the actuator to operate. The valve position detection feedback device measures the displacement of the actuator’s valve stem and converts it into an electrical signal that is fed back to the signal conditioning circuit. Intelligent valve positioners usually come equipped with a liquid crystal display and manual operation buttons; the display is used to show various status information related to the valve positioner, while the manual operation buttons are used to enter configuration data and perform manual operations. Advantages of intelligent valve positioners: Intelligent valve positioners are based on microprocessors, and compared to many analog valve positioners, they have the following advantages: ① They have fewer mechanical moving parts; the comparison of input signals and feedback signals is done digitally, which makes them less susceptible to environmental influences. Their operational stability is high, and there is no issue of dead zones caused by mechanical errors, resulting in high positioning accuracy and reliability. ②Intelligent valve positioners generally include common functional modules for linear, logarithmic, and quick-open characteristics, and these can be set directly via buttons or a computer or handheld data setter, thus making it easy to modify the flow characteristics. ③Zero adjustment and range adjustment do not affect each other, so the adjustment process is simple and fast. Many types of intelligent valve positioners can not only automatically adjust the zero point and range, but also automatically identify the specifications of the actuator installed, such as the volume of the air chamber and the mode of operation, and make corresponding adjustments to ensure that the control valve is in its optimal operating condition. ④In addition to standard self-diagnosis functions, intelligent valve positioners can generate feedback signals corresponding to the actual operation of the control valve; they are of the intelligent type that can receive digital signals for remote monitoring of the control valve’s operating status. The valve positioner has bidirectional communication capabilities, allowing for the configuration, tuning, and diagnosis of the valve positioner locally or remotely using a host computer or a handheld operator. The control signal for intelligent valve positioners is 4-20mA; this signal typically comes from a PLC system, DCS system, PID regulator, or operator panel. For conventional instruments, a PID regulator is typically connected to the measurement signal of the controlled process. The controlled process, the measurement sensor, the control valve, and the PID regulator together form a closed-loop control system. The valve position feedback signal generated by the intelligent valve positioner is generally not fed into the PID regulator ； When the valve positioner is controlled by a manual operator, the operator can receive both automatic control signals and the valve position feedback signal output by the intelligent valve positioner.