Extending the Faraday cup aerosol electrometer based calibration method up to 5 µm

A Faraday cup aerosol electrometer based electrical aerosol instrument calibration setup from nanometers up to micrometers has been designed, constructed, and characterized. The set-up utilizes singly charged seed particles, which are grown to the desired size by condensation of diethylhexyl sebacate. The calibration particle size is further selected with a Differential Mobility Analyzer (DMA). For micrometer sizes, a large DMA was designed, constructed, and characterized. The DMA electrical mobility resolution was found to be 7.95 for 20?L/min sheath and 2?L/min sample flows. The calibration is based on comparing the instrument’s response against the concentration measured with a reference Faraday cup aerosol electrometer. The set-up produces relatively high concentrations in the micrometer size range (more than 2500 1/cm³ at 5.3?µm). A low bias flow mixing and splitting between the reference and the instrument was constructed from a modified, large-sized mixer and a four-port flow splitter. It was characterized at different flow rates and as a function of the particle size. Using two of the four outlet ports at equal 1.5?L/min flow rates, the particle concentration bias of the flow splitting was found to be less than ±1% in the size range of 3.6?nm–5.3?µm. The developed calibration set-up was used to define the detection efficiency of a condensation particle counter from 3.6?nm to 5.3?µm with an expanded measurement uncertainty (k?=?2) of less than 4% over the entire size range and less than 2% for most of the measurement points.

Copyright © 2018 American Association for Aerosol Research     

Miniature differential mobility analyzer for compact field-portable spectrometers

A low-flow miniature differential mobility analyzer (mDMA) has been developed for compact field-portable mobility spectrometers to classify the submicrometer aerosol. The mDMA was designed for an ultra-low aerosol flow rate of 0.05 L/min. At a sheath flow rate of 0.2 L/min, the mDMA's upper size limit was estimated to be about 921 nm. The mDMA has a classification zone of 2.54 cm long, an outer diameter of 2.54 cm, and an inner diameter of 1.778 cm. The design allows low-cost fabrication and easy assembly. Tandem DMA measurements were carried out to evaluate the performance of the mDMA. Its transfer function was described using Stolzenburg's model. The experimentally measured transfer function shows close agreement with the theory. The transmission efficiency was comparable to that of the Knutson–Whitby DMA for particles in the range of 10–1000 nm. The mobility resolution was comparable to that of the TSI 3085 nanoDMA at the same aerosol flow rate. The design features and performance of the mDMA make it suitable for compact field portable mobility size spectrometers for measurement of nanoparticles and submicrometer aerosol.     

A light-weight,high-sensitivity particle spectrometer for PM2.5 aerosol measurements

A light-weight, low-cost optical particle spectrometer for measurements of aerosol number concentrations and size distributions has been designed, constructed, and demonstrated. The spectrometer is suitable for use on small, unmanned aerial vehicles (UAVs) and in balloon sondes. The spectrometer uses a 405 nm diode laser to count and size individual particles in the size range 140–3000 nm. A compact data system combines custom electronics with a single-board commercial computer. Power consumption is 7W at 9–15 V. 3D printing technology was used in the construction of the instrument to reduce cost, manufacturing complexity, and weight. The resulting Printed Optical Particle Spectrometer (POPS) instrument weighs about 800 g with an approximate materials cost of 2500 USD. Several POPS units have been constructed, tested in the laboratory, and deployed on UAVs. Here we present an overview of the instrument design and construction, laboratory validation data, and field engineering data for POPS.     

A multi-channel electrical mobility spectrometer with wedge geometry—Design and first evaluation

This paper presents a new design for a multi-channel electrical mobility spectrometer which measures the lognormal size distribution and number concentration of aerosol particles in the size range 5–300 nm with a short response time. The spectrometer charges particles in the test sample by unipolar corona discharge, they are then classified into 16 channels by electrical mobility. Charged particles are detected in the channels by individual aerosol electrometers, giving an electrical mobility spectrum for the sample.The main aspect of the spectrometer design is a wedge-shaped classifier with flat electrodes. This allows a flow to be drawn from the classifier at 16 different levels/channels with minimal disturbance to the remaining flow, hence filter based aerosol electrometers can be used for detection. The varying field within the classifier caused by the wedge shape is advantageous to the classification and optimised through the selection of the wedge angle.Also presented is an alternative technique for inferring the lognormal size distribution of an aerosol from a measured electrical mobility spectrum. This involves using a theoretical model of the instrument to simulate the output mobility spectra for a large number of aerosol samples with lognormal size distributions. The resulting data library can be searched against a measured electrical mobility spectrum to find the corresponding size distribution.The experimental work presented in this paper is a first evaluation of this spectrometer and includes measurement of the classifier transfer functions, basic calibration of the charger, and finally testing the spectrometer's performance on some simple unimodal lognormal aerosol samples.     

Characterization of nanosized silica size standards

Nanosized silica size standards produced with a sol–gel synthesis process were evaluated for particle size, effective density, and refractive index in this study. Particle size and effective density measurements were conducted following protocol from the National Institute of Advanced Industrial Science and Technology (AIST) in Japan. Particle sizes were measured via electrical mobility analysis using a differential mobility analyzer (DMA) at sheath flow rates (Q_sh) of 3.0 and 6.0 L/min and a constant aerosol flow rate (Q_a) of 0.3 L/min. The measured mean and mode diameters agreed well with the labeled sizes in the size range 40–200 nm, with differences ranging from 0.03% to 0.8%, well within the labeled expanded uncertainties (95% confidence intervals) of 1.8%–2.2%. The coefficient of variation (CV) of the size distribution was 0.012–0.027 for 40–200 nm. Particle sizes measured for 20 nm and 30 nm standards showed size differences with respect to the certified sizes of 1.7% and 8.3% at Q_sh = 6.0 L/min, but the size distributions were narrow, with CV = 0.047–0.064. The average effective density for the range 40–200 nm measured with an aerosol particle mass analyzer (APM) was 1.9 g/cm³. The real component of the refractive index measured with an optical particle counter (OPC) was 1.41 at a wavelength of 633 nm. All properties (size, effective density, and refractive index) were stable and could be measured with good repeatability. From these evaluations, it was found that the nanosized silica size standards have good characteristics for use as size standards and constitute a feasible alternative to PSL particles.

© 2017 American Association for Aerosol Research     

Near real-time measurement of carbonaceous aerosol using microplasma spectroscopy: Application to measurement of carbon nanomaterials

A sensitive, field-portable microplasma spectroscopy method has been developed for real-time measurement of carbon nanomaterials. The method involves microconcentration of aerosol on a microelectrode tip for subsequent analysis for atomic carbon using spark emission spectroscopy (SES). The spark-induced microplasma was characterized by measuring the excitation temperature (15,000–35,000 K), electron density (1.0 × 10¹⁷–2.2 × 10¹⁷ cm^?3), and spectral responses as functions of time and interelectrode distance. The system was calibrated and detection limits were determined for total atomic carbon (TAC) using a carbon emission line at 247.856 nm (C I) for various carbonaceous materials including sucrose, EDTA, caffeine, sodium carbonate, carbon black, and carbon nanotubes. The limit of detection for total atomic carbon was 1.61 ng, equivalent to 238 ng m^?3 when sampling at 1.5 L min^?1 for 5 min. To improve the selectivity for carbon nanomaterials, which mainly consist of elemental carbon (EC), the cathode was heated to 300°C to reduce the contribution of organic carbon to the total atomic carbon. Measurements of carbon nanotube aerosol at elevated electrode temperature showed improved selectivity to elemental carbon and compared well with the measurements from the thermal optical method (NIOSH Method 5040). The study shows the SES method to be an excellent candidate for development of low-cost, hand-portable, real-time instrument for measurement of carbonaceous aerosols and nanomaterials.     

A portable,four-wavelength,single-cell photoacoustic spectrometer for ambient aerosol absorption

Aerosols directly affect Earth's climate by scattering and absorbing solar radiation. Although they are ubiquitous in Earth's atmosphere, direct, in situ, wavelength-resolved measurements of aerosol optical properties remain challenging. As a result, the so-called aerosol direct effects are one of the largest uncertainties in predictions of Earth's future climate, and new instrumentation is needed to provide measurements of the absorption of sunlight by atmospheric particles. We have developed a portable, four-wavelength, single-cell photoacoustic spectrometer for simultaneous measurement of aerosol absorption at 406, 532, 662, and 785 nm, with an additional extinction measurement at 662 nm via a built-in cavity ringdown spectrometer. The instrument, dubbed MultiPAS-IV, is compact, robust, has low power requirements, and utilizes a multipass optical arrangement to achieve typical detection limits of 0.6–0.7 Mm^?1 for absorption (2σ, 2-min average). Tests with nigrosin aerosols show agreement with Mie theory calculations to within 2%, and comparison with a 7-wavelength aethalometer shows good correlation for ambient (Athens, GA, USA) aerosols. We demonstrate the utility of the broad spectral coverage and sensitivity of the MultiPAS-IV for calculating the absorption Ångström exponent of black carbon (AAE_BC, median value of 0.70) in ambient aerosols and use this value to derive the brown carbon contributions to absorption at 406 nm (43%) and 532 nm (13%) and its wavelength dependence (AAE_BrC = 6.3).

Copyright © 2018 American Association for Aerosol Research     

Brownian diffusion effect on nanometer aerosol classification in electrical mobility spectrometer

A multi-channel differential mobility analyzer (MCDMA) or aerosol spectrometer is widely used for classifying and measuring nanometer aerosol particles in the size range from 1 nm to 1 μm because of its better time response than a typical differential mobility analyzer. In the present study, the effect of Brownian diffusion on electrical mobility classification and trajectory of nanometer aerosol particles in an electrical mobility spectrometer developed at Chiang Mai University has been analytically investigated. Th Brownian diffusion of particles inside the spectrometer increased with decreasing particle size and flow rates of aerosol and clean sheath air, and with increasing inner electrode voltage, and also decreased with decreasing operating pressure. The particle trajectories considering Brownian diffusion motion inside the spectrometer were found to be broader than those under no Brownian diffusion. Smaller particles were found to have higher degree of broadening of trajectory than the larger particles. Brownian diffusion effect was found to be significant for particles smaller than 10 nm.     

Characterization of the TSI model 3086 differential mobility analyzer for classifying aerosols down to 1 nm

Measurement systems for particle sizing starting at 1 nm are used to bridge the gap between mass spectrometer measurements and traditional aerosol sizing methods, and thus to enable measurement of the complete size distribution from molecules and clusters to large particles. Such a measurement can be made using a scanning mobility particle sizer equipped with a diethylene glycol growth engine (e.g., TSI Model 3777 Nano Enhancer) along with a condensation particle counter, and a differential mobility analyzer (DMA) appropriate for such small sizes. Previous researchers have used high-resolution DMA (HRDMA) and also the TSI Nano-DMA (Model 3085) in such a scanning mobility particle sizer system. In this study, we evaluate the performance of the recently introduced TSI 1 nm-DMA (Model 3086). The transfer function was characterized using 1–2 nm monomobile molecular ion standards. The same measurements were repeated on a TSI Nano-DMA, with good agreement to previously published values. From the measured transfer function, the resolution of each DMA model was determined as a function of particle size and sheath flow rate. Resolution of the TSI 3086 in the 1–2 nm range was 10–25% higher than the TSI 3085. Measured resolutions of the TSI 3086 were 10–20% lower than theoretically predicted values, whereas those of the Model 3085 were 0–10% lower.

Copyright © 2018 TSI Inc.     

Ozone-free post-DBD aerosol bipolar diffusion charger: Evaluation as neutralizer for SMPS size distribution measurements

A postplasma neutralizer for submicron particles size measurements by mobility analysis has been evaluated. Bipolar ion currents have been measured downstream a dielectric barrier discharge (DBD) to estimate the ion fluxes at the inlet of charging volume and the n_i·τ product that define the theoretical maximal concentration that can be neutralized. Charge distributions were measured versus DBD voltage, aerosol diameter and concentration for monodisperse aerosols. It is confirmed that the charge distribution of particles depends on the ratio of initial positive and negative ion currents controlled by the DBD voltage leading to a tuneable mean charge of aerosol in this post-DBD bipolar charger. As expected from Gunn's law, the mean charge and the variance are proportional to particle diameter above 50 nm and independent of the aerosol concentration. The size distributions measured with ⁸⁵Kr and post-DBD neutralizer present the same modal diameters and a maximal overestimation of the total concentration of 10%, for aerosol from 15 to 730 nm with concentrations up to 6 × 10¹² m^?3. This post-DBD bipolar charger can be used for submicron aerosol neutralization and thus for scanning mobility particle sizer size distribution measurements in air as well as in nitrogen to suppress ozone downstream DBD.

Copyright © 2017 American Association for Aerosol Research     

Design Considerations and Performance Evaluation of a Compact Aerosol Particle Mass Analyzer

A compact aerosol particle mass analyzer (APM) of which the size of the classifier was significantly reduced than that of the first commercial model (Kanomax Model 3600) was developed. Firstly, requirements for desired performance in classifying particle mass were set forth. Secondly, a theoretical framework for the design parameters of an APM that satisfies the requirements was formulated. Thirdly, the design parameters were determined that satisfies the requirements while reducing the instrument size. The requirements include the condition that the classification range covers from 0.001 to 1000 fg (approximately 12 to 1200 nm in size for spherical particles having the density of 1 g/cm³), and the condition that both the classification resolution and particle penetration in this mass range are higher than certain specified values. A prototype having the design parameters determined according to this theoretical framework was constructed, and its performance was evaluated experimentally. The external dimensions of the electrodes of the compact APM are approximately 140 mm in length and 60 mm in diameter. It was confirmed that the performance of the compact APM operated at the aerosol flow rate of 0.3 L/min was comparable to that of the Model 3600 APM operated at 1 L/min. Because of the reduced size and of the resultant improved portability, it is expected that the compact APM is readily applicable to field measurements.

Copyright 2013 American Association for Aerosol Research     

A novel quartz crystal cascade impactor for real-time aerosol mass distribution measurement

A quartz crystal microbalance (QCM) based instrument has been developed for real-time aerosol mass distribution measurement. It includes two key components: a six-stage QCM micro-orifice cascade impactor and a novel relative humidity (RH) conditioner. This instrument operates at a flow rate of 10 L·min^?1 and measures the mass of the collected particles in six aerodynamic diameter channels between 45 nm and 2.5 μm. The RH conditioner ensures that the aerosol particles are collected at an RH between 40% and 65%, which is critical for eliminating particle bounce and for ensuring optimal particle coupling with the QCM. The nozzles of the impactors are clustered in the center of the nozzle plates. Therefore, particles are deposited on the central electrode of the QCM, where the mass calculated from first principles (i.e., Sauerbrey equation) agrees with the actual collected mass. The QCM response is linear up to around 130 μg for solid particles and up to around 2 μg for liquid particles. The collection efficiency curves of the QCM impactor stages were measured experimentally with monodisperse aerosols, and the results agree with the predictions of established impactor theory. This QCM-based instrument has also been tested with ambient aerosols with varying temperature and relative humidity. The aerosol distributions measured by this new instrument are in good agreement with simultaneous independent measurements carried out with a wide-range particle spectrometer (MSP Model 1000XP WPS).

Copyright © 2016 American Association for Aerosol Research     

Retrieving the ion mobility ratio and aerosol charge fractions for a neutralizer in real-world applications

Abstract

Electrical mobility size spectrometers (with a neutralizer, an electrical mobility classifier, and a detector as key components) are widely used to measure aerosol size distributions. The performance of a neutralizer is often evaluated separately from the spectrometer. In real-world applications of a neutralizer, i.e., typically with uncontrolled composition of the neutralizer carrier gas including trace constituents that can lead to variabilities in properties of positive and negative ions, charge fractions may differ from those predicted by widely used aerosol charging models with fixed ion properties and subsequently cause significant uncertainties in reported aerosol size distributions. In this study, we proposed an empirical method to retrieve the variations in neutralizer ion properties and aerosol charge fractions when measuring aerosol size distributions. Our approach requires measuring both positively and negatively charged particles using the electrical mobility size spectrometer to provide information on the performance of the neutralizer. Bipolar diffusion charging theories were applied to illustrate that aerosol charge fractions are governed by the mobility ratio of positive and negative ions. Positively and negatively charged particles measured by the spectrometer can be used to estimate the mobility ratio of positive and negative ions for the neutralizer. A modified Gunn and Woessner’s formula can then be used to calculate aerosol charge fractions from the retrieved ion mobility ratio. These charge fractions can be used for size distribution data inversion. Both simulated aerosols and experiments were used to evaluate the proposed method. We found that this new method can capture the variations in neutralizer ion properties and aerosol charge fractions under various conditions and help to achieve more accurate measurement of aerosol size distributions.

Copyright © 2018 American Association for Aerosol Research     

Characterization of a dimer preparation method for nanoscale organic aerosol

Nanoscale dimers have application in studies of aerosol physicochemical properties such as aerosol viscosity. These particle dimers can be synthesized using the dual tandem differential mobility analyzer (DTDMA) technique, wherein oppositely charged particle streams coagulate to form dimers that can be isolated using electrostatic filtration. Although some characterization of the technique has been published, a detailed thesis on the modes and theory of operation has remained outside the scope of prior work. Here, we present new experimental data characterizing the output DTDMA size distribution and the physical processes underlying its apparent modes. Key experimental limitations for both general applications and for viscosity measurements are identified and quantified in six distinct types of DTDMA experiments. The primary consideration is the production of an adequate number of dimers, which typically requires high mobility-selected number concentration in the range 25,000–100,000?cm^?3. The requisite concentration threshold depends upon the rate of spontaneous monomer decharging, which arises predominately from interactions of the aerosol with ionizing radiation within the coagulation chamber and is instrument location dependent. Lead shielding of the coagulation chamber reduced the first-order decharging constant from ～2.0?×?10^?5 s^?1 to ～0.8?×?10^?5 s^?1 in our laboratory. Dimer production at monomer diameters less than 40?nm is hindered by low bipolar charging efficiency. Results from the characterization experiments shed light on design considerations for general applications and for characterization of viscous aerosol phase transitions.

Copyright © 2019 American Association for Aerosol Research     

Mobility Analysis of 2 nm to 11 nm Aerosol Particles with an Aspirating Drift Tube Ion Mobility Spectrometer

We describe the performance of a drift tube-ion mobility spectrometry (DT-IMS) instrument for the measurement of aerosol particles. In DT-IMS, the electrical mobility of a measured particle is inferred directly from the time required for the particle to traverse a drift region, with motion driven by an electrostatic field. Electrical mobility distributions are hence linked to arrival time distributions (ATDs) for particles reaching a detector downstream of the drift region. The developed instrument addresses two obstacles that have limited DT-IMS use for aerosol measurement previously: (1) conventional drift tubes cannot efficiently sample charged particles at ground potential and (2) the sensitivities of commonly used Faraday plate detectors are too low for most aerosols. Obstacle (1) is circumvented by creating a “sample volume” of aerosol for measurement, defined by the streamlines of fluid flow. Obstacle (2) is bypassed by interfacing the end of the drift region with a condensation particle counter. The DT-IMS prototype shows high linearity for arrival time versus inverse electrical mobility (R ² > 0.99) over the size range tested (2.2–11.1 nm), and measurements compare well with both analytical and numerical models of device performance. A dimensionless calibration curve linking drift time to inverse electrical mobility is developed. In less than 5 s, it is possible to measure 11.1 nm particles, while 2.2 nm particles are analyzable on a subsecond scale. The transmission efficiency is found to be dependent upon electrostatic deposition for short drift times and upon advective losses for long drift times.

Copyright 2014 American Association for Aerosol Research     

Theory and design of a new miniature electrical-mobility aerosol spectrometer

Theory and design of a new electrical-mobility based instrument for measurement of aerosol particle size distributions in real-time is presented. Miniature electrical aerosal spectrometer (MEAS) has a rectangular cross-section with two main regions: the electrostatic precipitator (ESP) and classifier sections. The ESP section enables charged particle injection into the classifier section in a narrow range of streamlines at the desired location. The injected charged particles are then segregated based on their electrical mobility in the classifier section and collected on a series of plates that are connected to electrometers. Real-time particle size distribution measurements can be inferred from the electrometer signal strengths with the knowledge of the instrument transfer function. A theoretical approach is developed to calculate MEAS transfer function considering the non-uniformity in the electric and flow fields inside the instrument, and accounting for the instrument dimensions and its operating conditions. The theoretical predictions of size classification characteristics are seen to compare well with numerical results. The modeling results suggest that an optimal operational domain exists for MEAS.     

New fast integrated mobility spectrometer for real-time measurement of aerosol size distribution—I: Concept and theory

A new instrument capable of measuring aerosol size distribution with high time and size resolution, and high signal-to-noise ratios is described. The instrument, referred to as Fast Integrated Mobility Spectrometer (FIMS), separates charged particles based on their electrical mobility into different trajectories in a uniform electric field. The particles are then grown into super-micrometer droplets, and their locations on the trajectories are recorded by a fast charge-coupled device (CCD) imaging system. Images captured by the CCD reveal mobility-dependent particle positions and their numbers, which are then used to derive a particle size distribution spectrum. By eliminating the need to scan over a range of voltages, FIMS significantly improves the measurement speed and counting statistics. A theoretical framework has been developed to quantify the measurement range, mobility resolution, and transfer function of FIMS. It is shown that FIMS is capable of measuring aerosol size distributions with high-time and size resolution.     

Detection near 1-nm with a laminar-flow,water-based condensation particle counter

Presented is a laminar-flow, water-based condensation particle counter capable of particle detection near 1 nm. This instrument employs a three-stage, laminar-flow growth tube with a “moderator” stage that reduces the temperature and water content of the output flow without reducing the peak supersaturation, and makes feasible operation at the large temperature differences necessary for achieving high supersaturations. The instrument has an aerosol flow of 0.3 L/min, and does not use a filtered sheath flow. It is referred to as a “versatile” water condensation particle counter, or vWCPC, as operating temperatures can be adjusted in accordance with the cut-point desired. When operated with wall temperatures of ～2°C, >90°C, and ～22°C for the three stages, respectively, the vWCPC detects particles generated from a heated nichrome wire with a 50% efficiency cut-point near 1.6 nm mobility diameter. At these operating temperatures, it also detects 10–20% of large molecular ions formed from passing filtered ambient air through a bipolar ion source. Decreasing the temperature difference between the first two stages, with the first and second stages operated at 10 and 90°C, respectively, essentially eliminates the response to charger ions, and raises the 50% efficiency cut-point for the nichrome wire particles to 1.9 nm mobility diameter. The time response, as measured by rapid removal of an inlet filter, yields a characteristic time constant of 195 ms.

Copyright © 2017 American Association for Aerosol Research     

Measuring aerosol active surface area by direct ultraviolet photoionization and charge capture in continuous flow

Abstract

Direct ultraviolet photoionization electrically charges particles using a mechanism distinct from diffusion charging. The purpose of this study is to evaluate aerosol photoemission theory as a function of aerosol particle size, concentration, material, and morphology. Particles are classified using an aerodynamic aerosol classifier (AAC) and subsequently measured with a scanning mobility particle sizer (SMPS) and photoionization measurement system in parallel. This configuration allows direct comparison of photo-emission from high concentrations of initially neutral, monodisperse aerosols with different morphologies or materials. Under all examined conditions, the overall photoelectric yields of particles of self-similar material (silver and unconditioned soot) and morphology (sintered spheres and agglomerates) are each linearly proportional to the second moment of the mobility-equivalent diameter distribution, even in the transition regime (mobility diameter 30–200?nm), with agglomerate silver particles resulting in 5× higher photoelectric yield than unconditioned soot from a propane flame. It is shown for the first time that the photoelectric yield is significantly higher (2.6×) for fractal-like agglomerate silver particles than sintered, close-packed spherical particles of the same material and mobility-equivalent diameter, which is inferred to be due to the larger material surface area exposed externally to the particle surroundings. It is demonstrated that photoelectric measurements of aerosols reflect the photoelectrically active surface area which depends on the particle morphology and therefore the state of sintering.

Copyright © 2019 American Association for Aerosol Research     

A new miniature electrical aerosol spectrometer (MEAS): Experimental characterization

Design and theory of a new compact ultrafine particle sizing instrument, called the miniature electrical-mobility aerosol spectrometer (MEAS), was recently introduced [Ranjan, M., & Dhaniyala, S. (2007). A new miniature electrical spectrometer: Theory and design. Journal of Aerosol Science, 39, 950–963]. In the MEAS, electrostatic precipitation technique is used for both generation of sheath flow and classification of particles based on their electrical mobility. An electrometer-array, connected to the collection electrodes in the classifier section, is used to measure the number of particles collected in the different mobility channels, and these data are inverted using MEAS transfer functions to obtain particle number size distributions. Design of a prototype MEAS and the experimental approach to validate the performance of the individual components of the instrument are presented. Particle size distributions obtained from MEAS measurements compare well with those obtained using a scanning mobility particle sizer (SMPS; TSI 3936), validating theoretical calculations of instrument transfer functions. The operational limits of MEAS are determined from the calculation of error in the inverted size distribution as a function of total particle concentration. This analysis suggests that the designed MEAS can be used for applications such as personal and ambient monitoring under conditions of moderate to high particle concentrations.