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Data
76
Measurement principle
Two detectors are used to detect the transmitted light and scattered light by using the blinking
LED light source. While light source L1 is blinking, detector D1 detects the transmitted light
and D2 detects the scattered light. The influence of the ambient light is eliminated by causing
the light sources to blink and by obtaining the difference between a turn-on signal and turn-off
signal.
Obtained signals are defined as follows:
S/T is calculated according to the obtained signal.
This S/T has the effect of eliminating the damping of light caused by variations in the light
sources, variations in the detectors, and local contamination.
The S/T obtained during zero water measurement is stored as S0/T0.
“S/T-S0/T0” is a relative value. It is multiplied by the coefficient
and is span-calibrated to
obtain a standard function value corresponding to the value of the turbidity.
Signal
Type
Light source
Detector
T
Transmitted light
L1
D1
S
Scattered light
L1
D2
D2
L1
D1
S/T
Scattered light S
Transmitted light T
Signal amount
relative value
Turbidity