Particle counters are used to count a certain type of particle in a variety of material types. Aerosol counters determine size and number of particles in the air and are often used to determine air quality or check clean rooms for contamination. Liquid counters count particles in liquid such as when analyzing drinking water quality or purity of aqueous drugs. Finally, solid counters measure dry particles and are often used to analyze protein aggregation or material quality in industrial labs.
Based on the type of material and the size of the particles being analyzed, instruments differ in the detection method employed. These methods include: light blocking or scattering, the Coulter principle which is based on changes in electrical impedance, and direct imaging. Choice of detection method will depend on the application the counter is being used for.