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3. Calibration and turbidity units
3.1 Calibration principle
For turbidity measurements to be comparable, they need to be referenced to an international standard or reference material, and formazine was chosen.
It was proposed as a standard in 1926, but not recognized until 1960. It has the advantage of being reproducible using pure chemicals as reference material, thus enabling certified uncertainty to be obtained.
Before the adoption of formazine, other "standards" existed, such as silica, Fuller's earth, kaolin, diatomaceous earth and acid-purified sediments. The results were not very satisfactory, but they enabled turbidimeters to be "calibrated" for specific applications. What's more, these standards were not international.
In the water sector,...
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Calibration and turbidity units
Optical measurement techniques
Bibliography
References
Glossary
Turbidity: the reduction in transparency of a liquid due to the presence of undissolved matter (NF EN ISO 7027 standard).
The definitions below are taken from FD ISO GUIDE 30.
Reference material (RM): material or substance for which one or more property values are sufficiently homogeneous and well defined to enable it to...
Regulations
Ministerial Order of February 2, 1998, published in the Journal Officiel of March 3, 1998
* Section III – Surface water pollution
Article 31
For receiving waters to which the provisions of Decree no. 91-1283 of December 19, 1991 apply, the effects of discharge must comply with the following provisions: no increase of more than 30% in suspended solids.
...
Standardization
- Water quality – Turbidity determination. - NF EN ISO 7027 - (mars 2000)
- Qualité de l'eau. Échantillonnage. Partie 1 : lignes directrices pour la conception des programmes et des techniques d'échantillonnage. - NF EN ISO 5667-1 - 2007
- Qualité de l'eau. Échantillonnage. Partie 3 : lignes directrices pour la conservation et la manipulation des échantillons d'eau. - NF EN ISO 5667-3 - 2004
- Qualité de l'eau....
Manufacturers and distributors
Table 1 lists the main equipment manufacturers and their distributors.
Organizations
Association of Measurement, Control and Automation Equipment Operators (Exera) http://www.exera.com/
ISA Instrumentation, Systems and Automation Society http://www.isa.org
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