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9 REFERENCE
9.3
Turbidity Measurement
TW-150 operates using 90-degree light scattering method. Turbidity is calculated by
measuring the scattered light caused by the particles present in the water.
When light of constant intensity is passed through the turbid water layer, turbid particles in the
water will cause the light to scatter, which further increases the concentration of scattered
light.
The thickness of the water layer is proportional to the density (concentration) of the turbid
particles present in the water.
The light used in TW-150 has a wavelength of 870 nm, and is compliant to ISO 7027-1:2016.
9.4
Color Measurement
The transmitted light measurement method is used in TW-150. This method measures the
level of brownish-yellow in yellow-like colors shown in dissolution and colloidal materials
contained in water at a wavelength of 375 nm using absorptiometry.
Evaluating the color turbidity coefficient
In sample water measurement, read measured color value X
set to 0.000, and read measured color value X
Then, measure the sample water using a color meter other than that in this device and
evaluate X'.
Reference
See " 5.10.3 Correcting color using turbidity (page 102)".
This instrument is calibrated with the span calibration standard solution described above in
page 31 before sending for shipping inspection. Depending on the turbidity of the sample,
measurement result may deviate from the TCU*1 manually analyzed value if default factory
setting is used*2. In order to adjust the measured value of this device to the TCU measured
value obtained through manual analysis, substitute the manually analyzed value as X'. In
addition, since this instrument doesn't measure after filtration, deviations in measurement
value obtained by manual analysis may occur if there is a change in sample properties.
Perform readjustment according to the above procedure if deviations are present.
*1: TCU (True Color Unit): "True chromaticity" which is obtained by measuring the chromaticity
after filtration.
*2: For manual analysis, turbidity components are removed before measuring. However, TW-
150 is not equipped with a filtration feature. Instead it is equipped with turbidity compensation
feature. Turbidity compensation feature is disabled for default factory setting.
166
Turbidity coefficient =
when the turbidity coefficient is
0
when the turbidity coefficient is set to 1.000.
1
X'
X
0
X
X
0
1
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