Principles of Operation

Turbidity is the optical property that causes light to

be scattered and absorbed, rather than transmitted. The scattering of the light that passes through a liquid is primarily caused by the suspended solids. The higher the turbidity, the greater the amount of scattered light. Because even the molecules in a very pure fluid scatter light to a certain degree, no solution will have zero turbidity.

The USEPA Method 180.1 specify the key parameters for the optical system to measure turbidity for drinking, saline and surfacewater in a 0 to 40 NTU (Nephelometric Turbidity Unit) range, using the nephelometric method.

The light beam that passes through the sample is scattered in all directions. The intensity and pattern of the scattered light is affected by many variables like wavelength of the incident light, particle size and shape, refractive index and colour. 

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