Selection of multi-angle combination in precise turbidity measurement

Turbidity is an obvious and direct indicator of water quality which embodies the existence and concentration of certain particles in water sample to some extent. Quantitative measurement of turbidity by methods with a light intensity sensor at a single angle has been studied adequately whereas the study is rare on methods involving multi-angle light intensity signals. In this paper, an optimization on angle selection of an existing four-angle turbidity measurement method has been discussed. Experiments have been conducted using an 850 nm laser and a power meter. Scattering light intensities at a series of angles are collected to estimate turbidity. Results show that the accuracy can be further improved by using proper angle combinations. Relative estimation error by using optimized angle combination is only about 36% of the existing method in average for the test samples.