Performance Comparison of Scanning Electrical Mobility Spectrometers

Abstract

Scanning electrical mobility spectrometers (SEMS) are commonly used for near real-time ultrafine particle size distribution measurements. Analysis of SEMS measurements to calculate particle size distributions requires detailed understanding of instrument characteristics and operation. Varying instrument designs are used in the different commercial SEMS systems, and data analysis with these instruments requires accurate knowledge of their relative performance. In this study, an experimental approach to evaluate and reconcile differences between different SEMS instruments is established. This approach is used to characterize the relative performance of two SEMS systems-TSI's SMPS 3936-L22 and MSP's WPS XP1000-for particle sizes in the range of 20 to 300 nm. In these tests, the instruments were operated under a low flowrate condition with aerosol and sheath air flows of 0.3 and 3 LPM, respectively. Measurements show that the particle sizing characteristics of the instruments are very consistent with each other over the entire range of particle sizes studied. Particle number characteristics are dependent on the treatment of particle losses in the system and accounting of non-idealities of transfer function. The number concentrations reported by two instruments are generally consistent with each other and with an upstream reference counter for particle sizes larger than ∼90 nm. For smaller particles, the low flowrate operation of the two systems results in significant penetration losses. A net particle detection efficiency (NPDE) factor for the two systems was determined from experiments with monodisperse aerosol. This factor is seen to be effective in characterizing and reconciling measurements made with these two SEMS instruments.

A Handheld Electrostatic Precipitator for Sampling Airborne Particles and Nanoparticles

“…The gross and net efficiencies both showed a similar correlation with ESP voltage, with variations on the order of 5-15%. Since similar or larger discrepancies have been reported for comparison of nanoparticle measurements made with different brands of particle sizers (Rodrigue et al 2007), that level of accuracy may well be deemed acceptable by the industry.…”

“…One concern is that the absolute accuracy of particle sizers/counters is in question and there is no standard reference method for their calibration (Fierz et al 2007;Rodrigue et al 2007). There is also the possibility of particle losses within the collection system due to diffusion of particles onto surfaces of the flow channel or due to charged particles that blow-by or whose trajectories miss the sampling media but are caught by surfaces surrounding the media.…”

Experimental Comparison of Two Portable and Real-Time Size Distribution Analyzers for Nano/Submicron Aerosol Measurements

“…This paper thus examines the performance and monitoring capability of the two portable ultrafine to nanoparticle sizers in terms of particle sizing and counting, and compares them to a reference TSI SMPS 3936, the most commonly used electrical mobility particle spectrometer in aerosol science researches (Rodrigue et al, 2007). The National Institute of Standards and Technology (NIST) also applied a similar system to measure size 60 nm and 100 nm standard size reference materials (Mulholland et al, 2006).…”

A Wide-Range Particle Spectrometer for Aerosol Measurement from 0.010 µm to 10 µm

“…While the DMA performance is not ideal, if the measured size-dependent transfer functions are incorporated in the data reduction algorithm, the mobility-based size distribution measurement will be adequate for the majority of practical applications. This has been demonstrated in a recent performance comparison study of scanning electrical mobility spectrometers (Rodrigue et al, 2007).…”