AAAR 35th Annual Conference October 17 - October 21, 2016 Oregon Convention Center Portland, Oregon, USA
Abstract View
Design and Optimization of a Compact Low-Cost Optical Particle Sizer
TOMAS NJALSSON, Emily Roach, Igor Novosselov, University of Washington
Abstract Number: 707 Working Group: Instrumentation and Methods
Abstract Quantifying personal exposure to particulate matter is an important part of health risk assessment. Upon inhalation, particulate matter may deposit in the respiratory system potentially causing adverse health effects. When assessing personal exposure, temporal data of particle concentration and size distribution is useful but difficult to gather. Large form factor optical particle counters (OPC) can accurately determine particle size and concentration but they have limited applications due to their size and cost. Smaller OPCs generally have large uncertainties associated with particle sizing due to ambiguity in the optical properties of the particles. These devices use assumptions about the particles' refractive indices and therefore may not be accurate over a broad range of environmental aerosols.
We present the design of a compact low-cost OPC capable of sizing particles based on their physical dimensions. The combination of an optimized geometry and an efficient sizing algorithm minimizes the uncertainty caused by variations in the refractive indices of particles, allowing for more accurate measurements over a broader range of environmental aerosols. The photodetector position (proximity and angle) and the sizing algorithm are optimized using numerical simulations based on Mie scattering of spherical particles. The simulations show that by using the optimized design, instances where particles are sized incorrectly can be reduced by 54% on average over the 1-10 micro-meter range when compared to a non-optimized design (photodetector at 90°). An experimental setup utilizing low-cost components is used to validate and test the performance of the design against monodisperse aerosols.