Abstract: An apparatus is provided for measuring particle sizes between 5 and 50 microns in size and between 10 and 4,000 ppm in concentration prior to dilution of the sample, and upwards to at least 50,000 ppm with dilution of the sample. It is comprised of a laser light source, a square or rectangular sample cell and a photodetector which feeds data to some form of digital processor. The laser light is polarized and the return scattered light is polarized in the same plane. This device functions on the principle that particles in a light beam are capable of scattering the radiation in that beam and that the scattered radiation can be correlated to the physical properties of the scattering particles, specifically size and number.

Abstract: A suspended sediment sensor system for determining concentrations of particles and their size distribution in a submitted fluid sample. The particles being measured range from 50-1000 microns in dimensions and the concentrations range from <50 to 50,000 parts per million (ppm) of fluid. Equipment used includes a fall tube, laser light source, light scattering detector system, optical equipment, and a system to control the movement of the sample and other fluid past the laser and detector system. The detector system measures background scatter from particles impinged upon by the laser source at an angle of about 165.degree.. Contemplated to be used with the foregoing is a computer and associated controls to allow an unattended in situ system for a river, lake, etc.