Development Of Dust Concentration Monitoring System Based On Dual Light Path Method

Dust pollution has become increasingly serious and has attracted worldwide attention.Dust not only damages people's health,but also seriously pollutes the ecological environment,restricts the development of economic production and ecological civilization.And it affects all industries such as industry and agriculture,and transportation.Therefore,the monitoring of dust concentration has very important significance in environmental protection work and the protection of personal safety.Among many detection methods,optical detection methods are widely used in dust concentration monitoring because of their advantages such as low cost,high sensitivity,easy operation,and continuous on-line monitoring.The transmissive detection method is simple,the required measurement period is short,it does not interfere with the dust environment to be measured,and it is easy to implement real-time online monitoring.In order to meet the need of dust concentration monitoring in the atmosphere,a quantitative research work on dust particles was carried out.Based on the dual-optical path differential transmission method and related detection principles,a dual-optical transmission dust concentration detection device was established.A red laser diode with a wavelength of 650 nm was used as a measurement light source.The light intensity of the light source was modulated by a beam splitter and divided into two.One is the reference light and the other is the measurement light.The measured light was transmitted through the dust sample cell after being expanded by the light beam,collected by the focusing lens and converted into a current signal by the photodiode,and then subjected to signal processing and related detection to obtain a voltage signal proportional to the transmitted light intensity.The reference light was converted into a voltage signal proportional to the reference light intensity by another photoelectric conversion,processing and correlation detection circuit.The light path and hardware circuit design of the measurement system were described in detail.The soot particles were used for testing.The extinction coefficient of soot particles was obtained by the calibration method combined with least squares fitting.The continuous monitoring of soot particles with a known extinction coefficient was performed.The dust concentration value was calculated from Lambert-Beer law.The calculated results were compared with the dust concentration detector measurement results and it was found that the difference between the two results was within 5%.The factors that produce this error are analyzed.The research results show that the dual-optical path difference monitoring method combined with the relevant detection principle can accurately obtain the dust particle concentration with a known extinction coefficient,which can effectively reduce the influence of stray light,light source intensity fluctuation and other factors on the measurement results.The measuring device can realize real-time continuous monitoring of dust concentration in industrial production and provide technical support for dust concentration monitoring in complex environments.