Galvanic Applied Sciences USA, Inc.
101 Billerica Ave, Bldg. 5, Suite 104.
North Billerica, MA. 01862
Tel: 978-848-2701
Fax: 978-848-2713
Email: [email protected]
10
Typical Measurement units
ppm:
P
arts
p
er
m
illion
FNU
1
:
F
ormazin
n
ephelometric
u
nit
FTU:
F
ormazin
T
urbidity
U
nit
mg/l: Milligram per liter
TEF:
T
rübungs
e
inheiten
F
ormazin (German for
FTU)
gr/l:
Gram per liter
EBC:
E
uropean
b
rewery
c
onvention
% TS: Percent total solids
NTU
1
:
N
ephelometric
t
urbidity
u
nit
The dependencies on the different measurement units
1 FTU = 1 TEF = 1 NTU
1
= 1 FNU
1
= 0,25 EBC
1
Nephelometry describes the method of side scatter turbidity measurement; these units are used at 90° side scatter turbidimeters only.
Based on correlation studies, using a 12° forward measurement system we have found the following
dependencies:
1 FTU = 1 TEF = 0.25 EBC = 2.25ppm = 2.05 mg/l = 0.00205 g/l = 0.00000205 % TS
* At a specific particle weight of 1 kg/dm, 1mg/l particles in 1 kg of water will correspond to 1 ppm.
Typical ranges
The original design of scatter light turbidimeters was used for the detection of low turbidities. The
resolution of these kinds of instruments is suited easily in ranges lower as 0.1 ppm (approx. 0.05 TEF /
FTU / FNU / NTU or approx. 0.01 EBC) and better. The maximum range is 200 ppm (500 ppm for some
applications; there are some systems available with a range of more than 8000 ppm.
Which measurement method to use
The 12° forward scatter method:
The forward scatter method is typically used at low turbidities and produces nearly mass related
measurement results. Main applications are quality control, filtration control, oil in water, etc.
The 90° side scatter method:
The side scatter method is also used at low turbidities. This principle of measurement will produce
measurement results related to the number of particles in the product.
The main application is the observation of small, well-distributed particles e.g. beyond a filter. The
second typical application is the monitoring of potable water as well as wastewater according ISO7027 or
according to the US- FDA requirements.
The measurement results of a 90° scatter light system has to be interpreted carefully, since turbidity
caused by many large particles can show a similar measurement result as a turbidity caused by the same
quantity of small particles.
The combined 12°/ 90° forward- / side- scatter method:
The 12° measurement method has greater sensitivity with large particles. The 90° measurement method has greater sensitivity
with small particles. The most common application for the combined systems is filtration control.
A filter break through is
recognized early, with the 12° forward scattered instrument. A small quantity of big particles inside the filtrate will raise the
12° measurement value significant.
The 90° side scattered method exhibits only a small increase of the turbidity measurement values when
some large particles pass the filter. Detection of a filter breakthrough would be delayed, since the number
of particles will not increase significantly when the filter starts to break.
Please note:
The combination of forward- and side- scatter turbidity measurement does not replace a particle size
analysis, but it can provide a tendency of the particle size distribution.
