The NTU , abbreviation of Nephelometric Turbidity Unit , is a measure of the turbidity (turbidity) of a liquid .
The method of measurement of the NTU is based on the reflecting power of the settleable difficult or completely colloidal particles in the liquid. During the measurement, a beam of light shone on the fluid and perpendicular to this the light volume measured. The more light the more it is measured by the particle is reflected. A direct correlation between the amount of particles and the measured NTU is not to explain since the reflection, shape and color of the particles may vary.