Metrological Support of Liquid and Aerosol Particle Counters

The calibration and verification of liquid and aerosol particle counters are described. Aerosol particle counters are calibrated using latex spheres of known size. Depending on the design of the counters, the light scattered by the particles is detected at different angles. It is shown that detection of the scattered light at an angle of 90° leads to large measurement errors if the refractive index of the detected particles is not specified a priori. When the scattered light is detected over the entire solid angle, the error is substantially reduced. The metrological characteristics of counters with different designs are analyzed.