Calibration of Condensation Particle Counters

Condensation particle counters (CPCs) have been used extensively during the past decade to measure the particle number concentration and, as part of a scanning mobility particle sizer (SMPS™) spectrometer, the size distribution of ultrafine and fine particle emissions from a wide range of spark ignition and diesel engines (Bischof and Horn 1999). This paper illustrates a method of calibrating the CPC particle counting efficiency, determination of the smallest particle size detection limit, and particle concentration linearity, by generating ultrafine particles with a novel, commercially available electrospray aerosol generator and using a sensitive aerosol electrometer as the traceable reference. The counting efficiencies of several TSI model 3010 CPCs were calibrated against the electrometer using monodisperse particles in the size range of 4.5 to 95 nm. Results from the tests show that the counting efficiencies of the CPCs are in close agreement with each other. The concentration linearity response of the CPCs was tested with monodisperse 50 nm particles and compared against the aerosol electrometer at six particle concentration levels roughly equally spaced across the CPCs' measurement range. The test results demonstrate a linear measurement response of each CPC with correlation coefficients (R²) greater than 0.99. This paper also demonstrates that the lower detection limit of the CPC can be desensitized by adjusting the internal operating parameters of the CPC.