Enhancement of turbidimeter performance with optical fiber, grin lenses, and diode lasers

Abstract

A commercial turbidimeter, the Claritek Model SM8830 was updated by the utilization of more modern electro-optical components. Various diode lasers were tested as incident light sources with and without fiber optic collimators. These sources were tested in combination with phototransistor, photodiode and a light intensity-to-frequency converter integrated circuit detectors. The integrated circuit detector and photodiode were tested with and without a multiple fiber light guide. Testing consisted of correlating the detector response to an incrementally changing concentration of diatomaceous earth slurry. Results are presented as graphs of detector response vs slurry concentration. The best performance was realized with a 10 mW diode laser fitted with a multimode fiber collimator in combination with the light intensity-to-frequency converter I.C. fitted with a multiple fiber light guide. These component subassemblies were used in constructing a prototype sensing head suitable for adaptation to the model SM8830 suspended solids monitor.