PAC System Of Air Quality Detection Based On VPN

Nowadays, Environmental protection is an important aspect of sustainable development. Air quality testing is one of the very important parts. With " automatic system of air quality detection in Wuhan" project, our group gets a set of system solution, developed and put it into operation,through a large number of automation solutions research. We carry out research in embedded computer technology, network technology, analytical instruments, and environmental monitoring technology. Specific studies are as follows:First of all, briefly set out an overview of topics, significance and their development of home and abroad. Then, we gain focuses of the study and difficulties of the development. Secondly, understand the objectives and requirements of the system. Through summary of the development of automation and research of three classical systems, which are modern PLC control system, SCADA systems, and DCS control system. A suitable design of the overall system is put forward.Thirdly, start from the system network structure. By discussing the advantages and disadvantages of the physical channel, we discuss the network options. Innovatively bring forward embedded systems based on the ADSL / GPRS dual-network, which is in VPN solution. This network structure provides a strongly supportive network to application layer of the system.Fourthly, the system hardware design is studied. In particular, the PAC (Programmable Automatic Controller), used in sub-station, are provided performance advantages. Then, a suitable model is chosen in a variety of PAC.Finally, the design of system software is researched. Software design in sub-station is carried out, such as the data organization, data acquisition methods, calibration process. With Indusoft software, successfully achieve the system's function requirements in application layer.