American Association for Aerosol Research - Abstract Submission

AAAR 39th Annual Conference
October 18 - October 22, 2021

Virtual Conference

Abstract View


Simplified Calibration of CPC Detection Efficiency Using Mono-Disperse Aerosols

DEREK OBERREIT, Siqin He, Kanomax FMT, Inc.

     Abstract Number: 487
     Working Group: Instrumentation and Methods

Abstract
Measurements of Condensation Particle Counter (CPC) detection efficiencies (Nsampled/N­detected) traditionally use a High Resolution Ion Mobility Classifier (HRIMC) to provide an aerosol with a known range of electrical mobilities and a faraday cup electrometer (FCE) to measure the charge concentration of the classified aerosol; however there are several sources of measurement error using this method. While corrections can be made to the measurements, these corrections depend on the raw particle size distribution and an assumption that the charge distribution matches empirically measured values. Existing methods also do not allow for calibration of the activation efficiency independent of transport efficiency, latter of which is size dependent and can skew the result. The transport efficiency of the FCE also leads to errors that are difficult to correct for. Mitigation of these concerns facilitates repeatable, high accuracy calibrations of detection efficiencies.

In this work, we describe a method for calibrating CPC detection efficiencies to fixed diameters using near monodisperse aerosolized proteins with a moderate resolution IMC. We show that these materials can be aerosolized with negligible interference by multiply charged particles or errors due to skewness of the challenge aerosol. We also show concentration as a function of condenser temperature profiles for several different materials and how variations in the stability of the challenge aerosol concentration can be corrected using a reference detector. We also show that by measuring the asymptote of these profiles, the activation efficiency as a function of condenser temperature can be determined. With this method, the transport efficiency and activation efficiency can be decoupled effectively eliminating this source of error from the reference detector.