HF scientific Micro100 Laboratory Turbidimeter - Manual (Page 20)

Micro 100 (5/10) Page 14
Rev. 3.3
Glossary
Formazin Turbidity Units (FTU): see Nephelometric Turbidity Units
Indexing a Cuvette: The United States Environmental Protection Agency (US EPA) recommends that
cuvettes used for turbidimeter calibration or sample measurement be indexed. To index a cuvette with
a sample in it, slowly rotate the cuvette throughout one complete revolution (360°). While rotating the
sample cuvette, observe the display and locate the position that the cuvette is in which provides the
lowest turbidity reading. This position is the indexed position of the cuvette.
Nephelometric Turbidity Units (NTU): Unit of measure used when comparing the light scattered by a
liquid media to the light scattered by a known concentration of Formazin Polymer. This unit of
measure is recognized as a measure of the optical clarity of an aqueous sample. NTU is the accepted
unit of measurement for turbidity.
Turbidity: 1) A measure of the attenuation of a radiant flux as it passes through a liquid media. 2)
Optical clarity of a liquid, 3) a phenomena caused by the presence of undissolved matter in a liquid
media.