15
10.
Glossary
Formazin Nephelometric Units (FNU):
see Nephelometric Turbidity
Units
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. Refer to section 4.2 of this manual to
learn how to index a cuvette in this instrument.
Nephelometric Turbidity Units (NTU):
Unit of measure used when
relating 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.