AAAR 35th Annual Conference October 17 - October 21, 2016 Oregon Convention Center Portland, Oregon, USA
Abstract View
Testing Performance of a Scanning Mobility Particle Sizer System using Mobility Classified Challenge Aerosols
MARK R. STOLZENBURG, Peter H. McMurry, University of Minnesota
Abstract Number: 412 Working Group: Instrumentation and Methods
Abstract Scanning Mobility Particle Sizers (SMPS) are widely used to measure aerosol size distributions with respect to mobility equivalent diameter. This paper describes a technique for assessing the performance of the SMPS hardware and software. The technique involves sampling mobility classified particles in parallel with the SMPS system and a second CPC. The SMPS charger is replaced with a "dummy" neutralizer, and the SMPS software must be set for no neutralizer or to use charge fractions equal to 1. This separates particle losses from considerations of charge fractions. (This approach does not allow testing the performance of the charger or assumptions made about charged fractions, though methods described by Wiedensohler et al. (2012) allow for the latter.) Our approach tests the effects of particle losses and SMPS CPC detection efficiencies on the accuracy of concentrations measured with the SMPS. It also provides information on the accuracy of particle size and size resolution measured with the SMPS DMA. The method can be readily implemented in the field using equipment and software that is available in many aerosol laboratories.
The standard SMPS data analysis assumes that the size distribution being measured is broad with respect to the width of the SMPS DMA transfer function. The proposed mobility classified challenge aerosol violates this assumption. It is shown that the resulting fractional errors in the recovered total concentration and mean size are of the order of the square of the dimensionless width, as relative standard deviation S (Stolzenburg and McMurry, 2008), of the SMPS DMA transfer function. For typical SMPS operation, these errors can be limited to S$^2<0.7%.
Stolzenburg, M.R. and McMurry, P.H. (2008). Aerosol Sci. Technol., 42, 421-432.
Wiedensohler, A. et al. (2012). Atmos. Meas. Tech. 5: 657-685.