Particle Sizing by Novel Scattered Light-Fluctuation Analysis
STEPHAN GROSSE, Lukas Oeser, Lars Hillemann, J. Lienig, ToPAS Inc., Minneapolis, USA
Abstract Number: 49
Working Group: Instrumentation and Methods
Abstract
Particle counting measurement methods such as the optical aerosol spectrometer can provide detailed information on the particle size distribution, but the coincidence error limits the maximum permissible number concentration to below 10E5 cm-3 [1]. At high concentrations, the measurement signal can only be analyzed photometrically (i.e. collectively). Classic photometers usually provide no particle size information.
A photometric measurement method for the simultaneous measurement of size and concentration was developed especially for absorbance arrangements [2]. It is obvious to combine the principle with an optical aerosol spectrometer. For a universal measuring device, only a scattered light arrangement can be considered, as such measuring setups are significantly more sensitive to small particles.
The work aims to develop such a method („fluctuation scattered light analysis “). Due to the random superposition of several scattered light pulses, the detector signal in the coincidence range appears at first glance to be noise. However, the signal contains information on the size and concentration of the particles. Both parameters can be extracted by a suitable regression of statistical signal parameters. Experimental investigations have shown that the accuracy of the new measurement method is better than 5% in terms of particle size and 10% in terms of number concentration. The scattered light fluctuation analysis therefore represents an opportunity to significantly extend the current range of applications for optical aerosol spectrometers.
The scope of this article will first explain in detail how the measurement method works, the measurement results will be subsequently discussed and application-specific challenges highlighted.
[1] Verein Deutscher Ingenieure, VDI 3867 Blatt 4, Berlin, Beuth Verlag GmbH, 2011.
[2] B. Wessely, Extinktionsmessung von Licht zur Charakterisierung disperser Systeme, Düsseldorf: VDI-Verl., 1999.
[3] German Patent Application DE 10 2023 111 793,9.