DESIGN AND OPTIMIZATION OF A COMPACT LOW-COST OPTICAL PARTICLE SIZER

Area of Science:

• Environmental Science
• Optical Engineering
• Aerosol Science

Background:

• Accurate measurement of particulate matter (PM) is crucial for air quality studies and pollution monitoring.
• Optical particle counters (OPCs) offer a low-cost, compact solution for PM measurements, but their accuracy can be affected by the particle complex refractive index (CRI).

Purpose of the Study:

• To develop a methodology for optimizing OPC sensor design and operation parameters to minimize CRI-induced sizing errors.
• To identify an optimal detector angle for OPCs that ensures accurate particle sizing across a range of sizes and materials.

Main Methods:

• Utilizing Monte Carlo numerical simulations with Mie scattering calculations to explore the sensor parameter space.
• Determining the optimal detector angle (θ = 48°) by minimizing CRI dependency for particle sizes from 0.5 to 10 microns.
• Experimentally validating numerical results using monodisperse silica, PSL, and alumina particles at optimized and other detector angles.

Main Results:

• The optimized detector position (θ = 48°) demonstrated the lowest dependency on CRI across the 0.5-10 micron size range.
• Experimental comparisons showed the optimized angle yielded the best accuracy for silica and alumina particles, while perpendicular angles offered better precision but lower accuracy.
• Numerical simulations closely matched experimental data for various particle types and detector configurations.

Conclusions:

• A CRI-independent particle sizing methodology for OPCs has been successfully developed and validated.
• Compact and accurate OPCs can be realized using low-cost components and optimized design parameters.
• The optimized detector angle (48°) is key to achieving high accuracy in PM sizing for diverse aerosol compositions.