9 Reference Data
106
9.4
TURB (turbidity) Measurement
TURB measurement is performed by using the visible light (VIS) absorbance.
The measurement method is the transmitting absorption method.
Calibration with the standard solution enables a simple measurement of TURB.
Measure in the measurement range of 200 or below. If measuring in a measurement range
that exceeds the specified value, the linearity deteriorates due to the scattering light influence.
9.5
How to Calculate the COD Conversion Factor
If it is judged that there is obviously a linear function between the measurement concentration
Xi (i = 1, 2,
n) and corresponding manual analysis value Y i (i = 1, 2,
n), the calibration
curve formula (regression formula) is expressed as follows.
Y = a + bX
The gradient of this regression line X-axis (b) and the Y-axis segment (b) can be calculated by
using the measurement value and the least-square method as in the following formula.
“a” and “b” are rounded to a value which is larger by 1 digit according to the number of
significant figures of the measurement value.
b =
a = Y - bX
Σ
（
X
i
- X
）
（
Y
i
- Y
）
Σ
（
X
i
- X
）
2
n
Σ
X
i
Y
i
- (
Σ
X
i
）
（
Σ
Y
i
）
n
Σ
X
i
2
-
（
Σ
X
i
）
2
=
