Abstract: A method of analyzing suspended solids, particularly in flowing liquids, in which a plurality of light sources and photodetectors are employed in predetermined arrangement to provide a relatively short light path and a relatively long light path for each photodetector, with the light sources being actuated in predetermined off-on sequence, to provide corresponding periods of illumination from each light source and intermediate periods of no illumination, with the no illumination value representing ambient light, and so combining the respective light values so obtained to provide values representing not only the suspended solid content but also comparison values indicating the presence of failures of the respective light sources and photodetectors, and apparatus for practicing the method.

Abstract: A device for measuring particles in a liquid, utilizing a light source for the illumination of two detectors, one through a relatively short distance and the other through a relatively long distance, with liquid to be measured passing between the light source and the two detectors. A reference signal produced by the first cell is supplied to an amplifier and indicator, and a measurement signal produced by the second detector is supplied to the amplifier and indicator, with such amplifier and indicator producing a visual indication of the concentration of particles suspended in the liquid. The two detectors and light source are contained in a small housing, remote from the amplifier and indicator, and connected to it by a flexible cable.