Aerosols are often represented through their size distributions according to their particle diameter. Particle size distributions are measurable with a scanning mobility particle sizer (SMPS). An SMPS consists of an electrostatic classifier and a condensation particle counter (CPC). The classifier consists of an impactor, which removes particles that are larger than the upper measurement limit; a neutraliser, which ensures that the particles have uniform charge distribution; and a differential mobility analyser (DMA). A DMA sorts the particles by their electrical mobility, which is dependent on the particle size. From the DMA, which has sorted the particles, the particles enter the CPC. A CPC measures the number of particles by enlarging submicrometer particles to larger particles, which are optically detectable. 

SMPS systems are widely applied in atmospheric measurement of both particle number concentrations and particle mass concentrations in both ambient air and in simulations in atmospheric simulation facilities, such as AURA.