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Each turbidity calibration mode has a default unit:
Nephelometric Mode: NTU (2020t) or FNU (2020i)
Ratiometric Mode: NTRU (2020t) or FNRU (2020i)
Attenuation Mode: AU (2020t) or FAU (2020i)
The meter will permit the user to choose to report results in any of the other available
calibration units (NTU, FNU, AU, FAU, NTRU or FNRU) other than the default unit. It also
allows the brewing industry to check process water in the nephelometric mode and choose
to have results reported in American Society of Brewing Chemists (ASBC) or European
Brewery Convention (EBC) units.
Acronyms
Defi nitions
Notes
Regulatory
Method
NTU
Nephelometric
Turbidity Units
Incandescent white light between
400 and 600 nm, 90° detection,
2020t
EPA 180.1
FNU
Formazin
Nephelometric Units
IR LED (usually) 860 nm, bandwidth
less than 60 nm, 90° detection,
2020i
ISO 7027
AU
Attenuation Units
Incandescent white light between
400 and 600 nm, 180° detection,
2020t
Not applicable
FAU
Formazin Attenuation
Units
IR LED (usually) 860 nm, bandwidth
less than 60 nm, 180° detection,
2020i
ISO 7027
NTRU
Nephelometric
Turbidity Ratio Units
Incandescent white light between
400 and 600 nm, 90° and 180°
detection, 2020t
EPA 180.1
FNRU
Formazin
Nephelometric Ratio
Units
IR LED (usually) 860 nm, bandwidth
less than 60 nm, 90° and 180°
detection, 2020i
Not applicable
ASBC
American Society of
Brewing Chemists
2020t/i Not
applicable
EBC
European Brewery
Convention
2020t/i Not
applicable
For more information see ASTM 07726-4 Standard Guide for the Use of Various Turbidimeter Technologies for the
Measurement of Turbidity in Water.
TAKING TURBIDITY WATER SAMPLES
Clean plastic or glass containers may be used for turbidity samples. Ideally, samples should
be tested soon after collection and at the same temperature as when collected.