Meteorological parameters such as relative humidity have a significant impact on the precision of PM2.5 measurement instruments based on light scattering. Instead of adding meteorological sensors or dehumidification devices used widely in commercial PM2.5 measurement instruments, a novel particle sensor based on multi-angle light scattering and data fusion is proposed to eliminate the effect of meteorological factors. Three photodiodes are employed to collect the scattered light flux at three distinct angles. Weather index is defined as the ratio of scattered light fluxes collected at the 40° and 55° angles, which can be used to distinguish the mass median diameter variation caused by different meteorological parameters. Simulations based on Lorenz-Mie theory and field experiments establish the feasibility of this scheme. Experimental results indicate that mass median diameter has less effect on the photodiode at the 55° angle in comparison with photodiodes at the 40° angle and 140° angle. After correction using the weather index, the photodiode at the 40° angle yielded the best results followed by photodiodes at the 55° angle and the 140° angle.

Direct-reading instruments which can provide real-time PM2.5 measurements are widely used because they are cheap and easy to use. However, these direct-reading instruments suffer from zero drift problems and have to be calibrated before use. Direct-reading instruments based on average value measurement can't give a correct assessment of PM2.5 mass concentrations when particles' diameter changes greatly. In this paper, a new particle sensor based on true RMS value measurement is designed. Three photodiodes are installed in the sensor at different scattering angles. The advantages of true RMS value measurement method are demonstrated from theory consideration. Field experiments have shown that: (1)PM2.5 mass concentrations based on true RMS value measurement are better than based on average value measurement, (2)PM2.5 mass concentrations got from different scattering angles are highly correlated, (3)this new particle sensor can achieve reasonable accuracy for running more than 120 hours.