Measurements of Aerosol Particle Size: Improved Precision by Simultaneous Use of Optical Particle Counter and Nephelometer

Abstract

Improved accuracy and precision in size measurements of submicrometer volatile particles are achieved by reconciling simultaneous measurements by optical particle counter (OPC) and nephelometer. Reconciliation of data obtained from the two instruments required a careful calibration and measurement of relative humidity in both instruments. Correspondence between the nephelometer response and that calculated from the OPC size distribution provides a standard that limits uncertainty and inaccuracy in the OPC size measurement. This approach is demonstrated for size measurements of volatile submicrometer aqueous NaCl droplets, for which a least-squares regression of the data provided a 0.95 correlation coefficient. The quantitative reconciliation of the two optical measurements provides an experimental test of their accuracy.