Abstract

The Wide-range Particle Spectrometer (WPS™) is a recently introduced commercial instrument with the unique capability to measure size distributions of aerosols from 0.01 to 10 µm in diameter. The instrument includes a Scanning Mobility Spectrometer (SMS) comprised of a Differential Mobility Analyzer (DMA) and a Condensation Particle Counter (CPC) for particle measurement from 0.01 to 0.5 µm and a Laser Particle Spectrometer (LPS) for measurement in the ~0.4 to 10 µm range. These components are small enough to fit into a small portable cabinet (~26 kg) with all accompanying control hardware and electronics. No external pumps are required and power consumption is only about 150 W. The DMA is calibrated with Standard Reference Materials (SRM) from the U.S. National Institute of Standards and Technology (NIST), including SRM 1691 and SRM 1963a. These are uniform size polystyrene latex (PSL) spheres available from NIST with mean diameters of 0.269 µm and 0.1018 µm respectively. The CPC has a dual reservoir design to prevent the working fluid from being contaminated by water due to moisture condensation in the condenser. The LPS is calibrated with four NIST-traceable PSL sphere sizes. Calibration curves are generated not only for PSL (real refractive index of 1.585), but also for discrete values real refractive index ranging from 1.30 to 1.60. This procedure allows the user to select the most appropriate curve for determination of the light-scattering-equivalent sphere size that takes into account the effect due to refractive index of real aerosols. The LPS has a wide-angle collection optics design to produce a monotonic response curve for routine measurement in the field.

Highlights

  • The Wide-range Particle Spectrometer (WPSTM) is a new aerosol-measuring instrument that combines several aerosol sizing techniques to measure aerosols over a wide particle size range

  • The main objective of this paper is to describe the overall design of the WPSTM and of its main components

  • 0.70 liter per minute (L/min) is sampled into the Laser Particle Spectrometer (LPS) and the remaining 0.30 L/min is sampled for electrical mobility classification by the Differential Mobility Analyzer (DMA) followed by single-particle counting by the Condensation Particle Counter (CPC)

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Summary

INTRODUCTION

The Wide-range Particle Spectrometer (WPSTM) is a new aerosol-measuring instrument that combines several aerosol sizing techniques to measure aerosols over a wide particle size range. The individual sizing techniques are well known and have been available for some years in stand-alone instruments. Investigators had to combine several stand-alone instruments to form a system to measure aerosols over a wide size range. Substantial effort is required to synchronize data collection from different instruments and to synthesize the data to produce meaningful measurements. Modern advances in microelectronics have allowed us to develop the WPSTM into a compact instrument with user-friendly features and advanced measurement capabilities

The techniques used in the WPSTM include laser light
WPSTM SYSTEM OVERVIEW
Flow Loop
DIFFERENTIAL MOBILITY ANALYZER
Dp is the particle diameter φ is the gas viscosity
CONDENSATION PARTICLE COUNTER
Measured DMA Size Distribution
LASER PARTICLE SPECTROMETER
High Gain Amp
Findings
Examples of Aerosol Size Distributions Measured with the WPS
Full Text
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