HF scientific Micro1000 Laboratory Turbidimeter - 0-10,000 NTU - Manual (Page 32)

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11. 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.
Formazin Nephelometric Units (FNU): see Nephelometric Turbidity Units
European Brewery Convention Units (EBC): A scale related to turbidity where 0.245 EBC’s = 1
NTU.
Nephelos: A scale related to turbidity where 6.7 Nephelos = 1 NTU.