From Glossary of Meteorology


(Or impactometer.) A general term for instruments that sample particles suspended in the atmosphere by impaction.

This instrument is based on the principle that particles in an airstream will continue in a straight line due to their inertia when the flow of the air bends sharply; if a surface to which they can adhere is present, they will strike it and may stick.
See cascade impactor, rotating multicylinder;
compare collector.