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The disc is mounted on a pole or line and lowered slowly down in the water. The depth at which the disk is no longer visible is taken as a measure of the transparency of the water. This measure is known as the Secchi depth and is related to water turbidity. Since its invention, the disk has also been used in a modified, smaller 20 cm (8 in ...
Turbidity is the cloudiness or haziness of a fluid caused by large numbers of individual particles that are generally invisible to the naked eye, similar to smoke in air.The measurement of turbidity is a key test of both water clarity and water quality.
Turbidity is a measure of the cloudiness of water based on light scattering by particles at a 90-degree angle to the detector. A turbidity sensor is placed in water with a light source and a detector at a 90-degree angle to one another. The light source is usually red or near-infrared light (600–900 nm).
More accurate measurements become important in the large volumes used in commercial food production. Also, a home cook can use greater precision at times. Water at 4.0 °C (39.2 °F) may be volumetrically measured then weighed to determine an unknown measuring-utensil volume [13] without the need for a water-density adjustment. [14]
Settleable solids are measured as the visible volume accumulated at the bottom of an Imhoff cone after water has settled for one hour. [2]: 89–98 Turbidity is a measure of the light scattering ability of suspended matter in the water. [2]: 131–137 Salinity measures water density or conductivity changes caused by dissolved materials.
The unit is called Formazin Turbidity Unit (FTU). Nephelometric Turbidity Units (NTU) specified by United States Environmental Protection Agency is a special case of FTU, where a white light source and certain geometrical properties of the measurement apparatus are specified. (Sometimes the alternate form "nephelos turbidity units" is used [7] [8])
Turbidity, or cloudiness, of water is a relative measure. It is an apparent optical property which varies depending on the properties of the suspended particles, illumination, and instrument characteristics. Turbidity is measured in nephelometer units referenced to a turbidity standard or in Formazin Turbidity Units. [20]
If the water has a large turbidity spike below 10 metres, the spike is unlikely to be seen by a satellite. For very shallow clear water there is a good chance the bottom may be seen. For example, in the Bahamas, the water is quite clear and only a few metres deep, resulting in an apparent high turbidity because the bottom reflects much band 1 ...