A laser fog nephelometer - Its description, calibration, and field testing

Laser fog nephelometer is an electrooptical device for direct measurement of atmospheric water drop size distribution, from which liquid water content and visibility are calculated. The nephelometer is designed to measure backscatter from the individual water droplets passing through the laser beam and electronically analyzes the resultant signal, producing real-time data. It is the subsequent handling of these data that provides information about visibility and liquid water content. Laser nephelometer calibration is described, and pertinent field test results are presented. It is shown that the described CW He-Ne laser fog nephelometer is a practical instrument for determining fog life cycles for water droplets with radii between 3 and 242 microns. A block diagram of the laser fog nephelometer system is included.