Research On Electronic Control System Of Chromatograph

As the second major pollutant of photochemical pollution in the atmosphere,peroxyacetyl nitrate（PAN）has almost no natural sources,and its concentration is closely related to human activities.In order to study it,reliable and stable measurement is required.Therefore,it is of great significance to study the PAN online analysis system.Relying on the NSFC project"Development of PAN/CCl₄/NOx Online Analyzers in the Atmosphere"declared by the Research Center for Ecological Environment of the Chinese Academy of Sciences,this article conducts research on the electronic control system of gas chromatographs.The system calibration process uses photochemical synthesis to generate quantitative PAN to periodically calibrate the GC-ECD,and its concentration is controlled by a flow meter.The electronic control structure of the system is a master-slave RS-485 structure,using a half-duplex RS-485 bus for communication,using an industrial computer as the master device,and mounting slave devices such as flow meters,temperature controllers,and FPGA control boards.A flow meter is used to control the gas flow during calibration.A temperature controller is used to control the temperature of acetone to ensure that the concentration of acetone is excessive during the reaction.The control board with altera’s EP4CE6E22C8N FPGA as the control chip,mainly controls high-interference devices such as solenoid valves and relays,by using Verilog HDL hardware logic programming language to write FPGA programs,and using Quartus II and Modelsim for development,debugging,simulation and burning.write.The host program is developed by NI’s Labview platform,the development language is the supporting G language,and the operating environment is Windows 7system.The automatic calibration control system of the gas chromatograph with the chromatographic workstation is designed,and the operation of its prototype and related verification work are realized.The system can run continuously when the initial file is configured to realize the functions of regular calibration,online analysis of the concentration of peroxyacetyl nitrate（PAN）in the atmosphere and generating.xls files.Online recognition of PAN peaks,area calculation,calibration and fitting processing in the system.And developed a small tool to facilitate manual data processing,so that the changes in the concentration of peroxyacetyl nitrate（PAN）in the atmosphere every day are imaged,reducing the workload of manual offline data processing.The system can realize fully automatic operation,and the results are used as scientific research equipment of the Ecological Environment Research Center of the Chinese Academy of Sciences,which helps to shorten the gap between domestic and foreign research instrument levels.