AAAR 32nd Annual Conference
September 30 - October 4, 2013
Oregon Convention Center
Portland, Oregon, USA
Abstract View
Method for Calibration of the Detection Efficiency of Condensation Particle Counters at Concentrations as Low as 1 cm$^(-3) Using a Faraday-cup Aerosol Electrometer
HIROMU SAKURAI, Kensei Ehara, AIST
Abstract Number: 426 Working Group: Instrumentation and Methods
Abstract We developed a method to calibrate the detection efficiency of condensation particle counters (CPCs) that utilizes a Faraday-cup aerosol electrometer (FCAE) as reference at concentrations down to 1 cm$^(-3). In a conventional CPC calibration using an FCAE as reference, the CPC under calibration and the reference FCAE sample aerosols of the same concentration after the flow splitter, and the ratio of the concentration indicated by the CPC under calibration to that by the reference FCAE essentially gives the detection efficiency of the CPC under calibration if the reference FCAE is calibrated. In our method, a diluter is inserted between the inlet of the CPC under calibration and the flow splitter so the aerosol for the CPC under calibration can be diluted. The ratio of the concentrations read by the two instruments is no longer the detection efficiency, but is the product of the detection efficiency of the CPC under calibration and the dilution ratio. Our method, the detail of which will be explained in the presentation, allows evaluation of the change of the detection efficiency for different concentration levels, by using the known concentration linearity response of the reference FCAE, without requiring the knowledge of the dilution ratio of the diluter. By combining this technique with the conventional one, we can determine the absolute detection efficiency at different concentration levels. We are able to calibrate the detection efficiency of a CPC down to 1 cm$^(-3) with the relative expanded uncertainty of about 3 % with the coverage factor k = 2. Our method is similar in the calibration capability to the method by Owen et al. (Aerosol Sci. Technol. 46:444-450, 2012) and the differences between the two methods will be discussed in the presentation.