AAAR 31st Annual Conference
October 8-12, 2012
Hyatt Regency Minneapolis
Minneapolis, Minnesota, USA
Abstract View
Calibration of a Condensation Particle Counter by Aerosol Particle Number Concentration System with Uncertainty Analysis
GUO-DUNG CHEN, Ta-Chang Yu, Center for Measurement Standards, ITRI, Taiwan
Abstract Number: 161 Working Group: Instrumentation and Methods
Abstract The measurement of aerosol particles number is important for environmental studies, clean room technology, human health, and environment safety. Therefore, the calibration of particles counter must be addressed. In this study, calibration of a commercial particles counter, such as condensation particle counter (CPC), by aerosol particle number concentration system was described. The system setup and measurement procedure were briefly introduced. The system consisted of electrospray aerosol generator, differential mobility analyzer (DMA), and Faraday-cup aerosol electrometer (FCAE). The electrospray generated aerosol particles from the liquid solution. Then, the particles were charged and classified by a differential mobility analyzer (DMA). Downstream of the DMA, the monodisperse aerosol was diluted in a mixing tube and equally flowed to the condensation particle counter (CPC) under calibration and Faraday-cup aerosol electrometer (FCAE). The Faraday-cup aerosol electrometer (FCAE) was calibrated by a traceable standard current source which was produced from voltage source (mV) and a nominal 100G ohm resistor. Both the voltage source and resistor properties were calibrated from National Measurement Laboratory, R.O.C. Besides, we generated the concentration with well-controlled flows and nominal size 100 nm polystyrene latex (NIST SRM 1963a) for calibration. The main contributions to the total uncertainty of the system included the uncertainty of the current measurement by Faraday-cup aerosol electrometer (FCAE), the uncertainty in splitting ratio at flow splitter, the uncertainty of difference in losses in tubes, and the variation of concentration due to instability. The measurement accuracy of the system are further identified and improved through uncertainty analysis. In our study, the expanded relative uncertainty of the concentration system was 10 % for particle concentrations of approximately 10$^3 particles / cm$^3.