What are the characteristics of pneumatic valve positioners? How to apply?

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This post was last edited by lilyqiu on 2019-4-10 at 20:24. There are mainly two types of valve positioners: \"pneumatic valve positioners\" and \"electro-pneumatic valve positioners\". When selecting a valve positioner, it is necessary to choose the appropriate one based on the different actuators and power sources available. As mentioned earlier, the characteristics and functions of electric-pneumatic valve positioners have been discussed; however, in many specific situations, we need to use pneumatic valve positioners as the positioning devices for valves. The input signal for pneumatic valve positioners generally comes from electro-pneumatic converters or pneumatic controllers. This input signal is usually a standard pressure of 20–100 kPa. Such positioners feature reliable operation, strong resistance to changes in temperature and humidity as well as electromagnetic interference; they also have inherent fire and explosion protection properties, are easy to maintain, and are inexpensive ； This article was first published on the WeChat official account: Self-Control Academy ； Its disadvantages are that it is not suitable for long-distance transmission, has a slow response time, and low precision; it is typically used in specific situations, such as those where electric-pneumatic valve positioners are not appropriate, for example when the environmental temperature, humidity, or level of vibration exceeds the limits tolerable by electronic components ； Due to its ease of maintenance and low cost, it is still widely used by many small and medium-sized enterprises in our country. In control systems, if electric instruments are used as controllers and the output signals are 0–10 mA ADC or 4–20 mA DC, we should use electrical converters to convert these 0–10 mA DC or 4–20 mA DC signals into 20–100 kPa signals, which are then fed into the pneumatic valve positioner in order to control the pneumatic actuator. In control systems, if pneumatic instruments are used as controllers and the output signal ranges from 20 to 100 kPa, this signal can be fed into a pneumatic valve positioner in order to control the pneumatic actuator.