Expansion CPC
An aerosol sample is humidified and led into a certain volume, which is connected via a solenoid valve to another certain volume that is evacuated. The solenoid valve switches rapidly to initiate expansion of air and particles start to grow to optically detectable sizes.
A laser beam illuminates the volume and the scattered light of the ensemble of growing particles is measured with a photomultiplier.
The scattered light curves are analyzed automatically and the total number concentration is calculated.