Research Of β-ray-absorption Dust Concentration Monitoring Technology Based On PLC

With the development of modern industry, the dust harm is increasing. The dust could causevarious respiratory diseases, even brings on the safety accident. The accurate measurement ofthe dust concentration is the premise of preventing and controlling the harm. Compared withother measuring methods, β-ray-absorption-method has a more abroad application with theadvantages of wide measuring range and high measuring accuracy, obviously with the featurethat can get rid of the influence form the physical characteristics of the dust.At present, of all the dust concentration measuring instruments applying the β-ray-absorption-method，foreign products are high precision and stability, and the error is generally small, buthard to popularize because of the high price; Domestic products are also high accuracy andlow cost, generally using MCU or ARM as the instrument controller, but it brings on thefollowing disadvantages: complex configuration, large volume, high mass and low stability.Measuring instrument of design adopting PLC (Programmable Logic Controller) as thecontroller, has the following advantages: small size, high reliability, low power consumptionand strong ability of extension.Ensuring the safe operation in serious industrial conditions，PLC has laid a foundation for the high stability dust concentration measuring instrument.With rich and mature extension module, PLC can ensure the realization of the continuousonline monitoring system for dust concentration monitoring.At present, dust concentration monitoring system and continuous online monitoringtechnology are still not mature. Adopting PLC as the controller has been reported rarelyamong the existing β-ray-absorption dust concentration measuring instruments.Therefore, thethesis focus on the technology research of β-ray-absorption dust concentration monitoringbased on PLC, offering a primary design basic on Siemens Simatic S7-200PLC. Design usingTD400C as the HMI(Human Machine Interface) of the Slave machine (PLC), adopting VisualBasic6.0develops the HMI of host machine (PC). PLC using Free-Port communicationprotocol to connect with PC, and they compose a dust concentration monitoring system. This paper is divided into six chapters, the first chapter presents the research significance andthe current research state of this topic. In chapter2, the design scheme of β-ray-absorptiondust concentration measuring instrument based on Siemens Simatic S7-200PLC is introduced.In the3to5chapter, the details of design are described. The selection of PLC and theperipheral device have been completed, the interface problem between them has been solved.And the parameters for the calculating formula have been set.The program design isintroduced, including the control and data processing module, sampling module andcommunication module. Design of man-machine module of the PLC is described in detail.Chapter6presents a summing-up of the thesis.By means of the selection of hardware，the matching of the interface，simulation andcalculation, the technical research of β-ray-absorption dust concentration measuringinstrument have been completed. The preliminary and practicable design of the monitorsystem have been given.This thesis has laid a foundation for the developing of the automaticonline dust concentration monitoring system with proprietary intellectual property rights andthe advantages of high precision and stability.