EN ISO 7027-1:2016

European foreword
Foreword
Introduction
1 Scope
2 Normative references
3 Terms and definitions
4 Sampling and samples
5 Quantitative methods of turbidity measurement using optical
  nephelometers
Annex A (informative) - Results of an interlaboratory
        collaborative trial to evaluate the suitability of a
        synthetic polymer for use as a secondary standard
        to formazin in turbidity measurements
Bibliography

ISO 7027-1:2016 specifies two quantitative methods using optical turbidimeters or nephelometers for the determination of turbidity of water:
a) nephelometry, procedure for measurement of diffuse radiation, applicable to water of low turbidity (for example drinking water);
b) turbidimetry, procedure for measurement of the attenuation of a radiant flux, more applicable to highly turbid waters (for example waste waters or other cloudy waters).
Turbidities measured according to the first method are presented as nephelometric turbidity units (NTU). The results typically range between