| The pollution of the PM2.5is becoming more and more serious, it threatens thevisibility of atmosphere and the healthy of people. Monitoring accurately of thePM2.5is the premise of the PM2.5pollution control. As the concentration of thePM2.5in China is generally higher, from those automatic monitor methods usedaround the world, only the method of β-ray-absorption combine with the dynamicheating system can be used on the monitoring of PM2.5in China. But the compositionof the PM2.5is complex, it contains a lot of volatilize particles, when we measurePM2.5with the method of β-ray-absorption combine with the dynamic heating system,the volatilize particles in the PM2.5will lost during the heating of sampling, so themeasure result is error. To solve this problem， we design a sampler oftheβ-ray-absorption PM2.5monitor in this paper, which contains the compensation ofvolatilize particles. It samples the volatilize particles by condensing and impacting,combined with the dual-channel impactor and electrical-heating method, it can sampleand measure continuously.This paper is divided into six chapters: the first chapter introduces the composition,source and the harm of the PM2.5simply, and then introduces the situation, advantageand disadvantage of the PM2.5monitor methods used around the world in detail. Thesecond chapter presents the design of sampler for theβ-ray-absorption PM2.5monitor,which contains the compensation of volatilize particles. It contains the integralstructure of the sampler, focus on the theory of impactor, calculating of the parametersand the continuous measurement scheme in volatilize particles measurement. In thethird chapter, we designed and machined some mechanical parts based on theprinciple of β-ray-absorption measurement, parameters of the impactor and therequirements of continuous measurement. The mechanical parts include fixed steel plate, sampling tube, container of source and detector, impactor, the cutaway views isshowed in the appendix. In the forth chapter, the output signal processing circuit ofG-M counter is introduced, the signal can be sent to the scaler for counting afterdifferential, pole-zero cancellation, voltage follower, voltage amplification anddiscriminating, so that it can measure the intensity of β-ray. The test result is showedthat it has reached the requirement of the design. The fifth chapter describes thedesigning of control circuit and the programs for SCM based on the requirements oftheβ-ray-absorption PM2.5monitor containing the compensation of volatilizeparticles. The control circuit includes four parts：filter transmission circuit feedingback by the photoelectric encoder, the up-and-down of sampling tube is controlled bythe stepper motor, flow control circuit for the pump controlled by PWM and feedingback by the flow sensor, switchover circuit of the tube controlled by electricalthree-way ball valve and electrical-heating control circuit in the impactor. After thesoftware simulating and the actual testing for the four circuits, it is showed that thesecontrol circuits can achieve the automation of the sampler. The sixth chapter is thesummary and outlook.In this paper, we designed a sampler for theβ-ray-absorption PM2.5monitor, whichcontains the compensation of volatilize particles by designing a scheme, designingand machining the critical part, designingã€simulating and testing the control circuit. Itis the basis for developing the β-ray-absorption PM2.5monitor containingcompensation of volatilize particles. |
