than spherical particles, while angular shapes have intermediate scattering efficiency. Turbidity
sensors are very sensitive to shape effects and this makes it very important to calibrate with
material from the monitoring site. It is also essential that particle shape remains constant during
the monitoring period.
B.4 High-sediment concentrations
At high sediment concentrations, particularly in suspensions of clay and silt, the infrared radiation
from the emitter can be so strongly attenuated along the path connecting the emitter, the
particle, and the detector, that backscatter decreases exponentially with increasing sediment
concentration. For mud, this occurs at concentrations greater than about 5,000 mg/l. Do not
exceed the specified turbidity or suspended-sediment ranges because the interpretation of the
signal can be ambiguous.
B.5 Water color
Although organic and inorganic infrared-absorbing, dissolved matter has visible color, its effect
on turbidity measurements is small unless the colored compounds are strongly absorbing at the
sensor wavelength (850 nm) and are present in high concentrations. Only effluents from mine-
tailings produce enough color to absorb measurable infrared. In river, estuary, and ocean
environments, concentrations of colored materials are too low by at least a factor of ten to
produce significant errors.
ClariVUE™10 Side-Scatter Turbidity Sensor
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