Patent ID: 8701466

Claim:
A device for characterizing the evolution over time of a size distribution of electrically-charged airborne particles in an airflow, comprising: an air inlet for entry of airborne particles in an airflow, a particle charging unit arranged to create electrically-charged airborne particles by electrically charging airborne particles having a size distribution entering the device, a concentration variation section to cause a variation of the concentration of electrically-charged particles between at least a first concentration level and a second concentration level during at least one time interval, a particle sensing section to produce a first measurement signal corresponding with the first concentration level, and a second measurement signal corresponding with the second concentration level, and a data evaluation unit being arranged to infer a particle number concentration and an average particle diameter of the size distribution of electrically-charged airborne particles from the first measurement signal and the second measurement signal and a reference particle diameter, wherein the data evaluation unit rejects the inferred average particle diameter when the change of the inferred average particle diameter with respect to the reference particle diameter exceeds a set maximum change.