ABSTRACT
Turbidity meters measure the cloudiness of a fluid by detecting the intensity of transmitted or reflected light. The cloudiness detected by turbidity meters is caused by suspended finely dispersed particles which when exposed to a visible or infrared light will scatter it. While the turbidity meter detects light scattering, the colorimeter measures light absorption. Different turbidity units have evolved in connection with the different designs. The various turbidity units all measure the amount of solid particles in suspension. Turbidity instruments utilize a light beam projected into the sample fluid to effect a measurement. For wastewater and biological sludge applications probe-type turbidity transmitters are preferred. The light beam is scattered by solids in suspension, and the degree of light attenuation or the amount of scattered light can be related to turbidity. When both color and solids are present, the total attenuation is the sum of absorption and scattering effects.
