SETUP & PRINCIPLE OF OPERATION Using a white light source, a precise calibration curve without ambiguity can be achieved, resulting in an extremely high size resolution. The patented T-aperture leads to an accurately defined optical measurement volume and permits a particle measurement without border-zone-errors and therefore a precise size measurement. The new and quick digitalised signal electronic analysis allows the identification and correction of coincidence. For the conversion of the measured indicators into mass or mass fractions, each value of the high resolution particle size distribution is multiplied with a correlation factor. In this way which shows that the aerosol particulate is made up of different sources. (e.g. combustion aersols, tire abrasion, pollen) according to its particle size (figure 3). A mass fraction is achieved by applying an additional separation curve (e.g. DIN EN 481) to the determined particle size distribution. Due to the different measurement principle (equivalence measurement method) an exact matching to gravimetry cannot be guaranteed in every case. At the same time, several separation curves can be used for the size distribution, which enables the simultaneous output of PM 10 , PM 2,5 , PM 1 (and others). Downstream to the optical sensor there is a filter holder for an optional gravimetric validation of measured data. Fig. 3 Comparison of algorithms for the conversion of particle size distribution according to PM factors. Fidas ® PM 2.5 FDMS PM 2.5 50 µg / m 3 Classical PM-analysis with constant density R 2 = 0.5 0 µg / m 3 50 µg / m 3 Algorithm for the emission measurement with a specific calibration curve & size dependent weighting of the particle R 2 = 0.95 mass for PM 1 , PM 2.5 , PM 4 & PM 10 0 µg / m 3 Comparison of PM 2.5 - measurements (3h-average) of FDMS & Fidas ® over 22 days Fig. 4 Comparison of 1-h measurements for PM 2.5 and PM 10 of Fidas ® 200 S with a TEOM FDMS of a measurement campaign in a city in Northern Germany during the time from August until November 2010 Fidas ® PM 2.5 70 60 50 40 30 y = 1.0301x - 1.2208 R 2 = 0.9688 Fidas ® PM 10 70 60 50 40 30 y = 0.9844x - 0.743 R 2 = 0.9583 20 20 10 10 0 0 0 10 20 30 40 50 60 70 0 10 20 30 40 50 60 70 FDMS PM 2.5 FDMS PM 10
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- Tim Cannon – Research and Development Manager; Pecan Engineering Pty Ltd