SYSTRONICS NEPHELO - TURBIDITY METER 135 is an accurate and elegant instrument designed for conducting nephelometric and turbidity measurements of suspended particles and colloids in solution. The principle of operation of this instrument is based on the well-known Tyndall effect. Abeam of light passing through a turbid liquid being tested, scatters the light which, in turn, is collected at right angles by a Photodiode and indicated in a display. The amount of scattered light is proportional to the turbidity of the solution under test. The applications of turbidity measurements are vast in Municipal, Public Health, Sewage Works and in Industrial Establishments for determining quality of water/waste water.