defr Glossar

To facilitate practical interpretation of the turbidity value, turbidimeters are calibrated with a standard suspension. Hence the reading is shown not in the form of the measured light intensity, but as a concentration of the calibration suspension. When a given suspension is measured, therefore, the reading shown means that the liquid in question scatters the same amount of light as the standard suspension of the concentration indicated.

The internationally accepted turbidity standard is formazine. The most common units are:

  • ASBC – “American Society of Brewing Chemists”.American unit used in breweries.

  • EBC (turbidity) – “European Brewery Convention”. European unit used in breweries.

  • FAU – “Formazine Attenuation Units”. Unit used in water treatment for transmitted light measurement (angle 0°) as prescribed by standard ISO 7027.

  • FNU – “Formazine Nephelometric Units”. Unit used in water treatment for measurement at 90° as prescribed by standard ISO 7027.

  • FTU – “Formazine Turbidity Unit”. Unit used in water treatment.

  • NTU – “Nephelometric Turbidity Unit”.

Unit used in water treatment for measurement at 90°
as prescribed by the U.S. EPA (Environmental Protection Agency).

  • TE/F - “Trübungseinheit/Formazin”.German designation used in water treatment.

Conversion table: turbidity units based on formazine:

1 EBC 1 FNU
1 NTU
1 FTU
1 ASBC
EBC 1 0.25 0.014
FNU
NTU
FTU
4 1 0.057
ASBC 70 17.5 1

Due to multiple scatter when measuring high turbidity, the concentration of the calibration suspension shows a non-linear dependence on the measured light intensity.

Figure 7 shows that the curve flattens at high turbidities. SIGRIST instruments therefore save some measuring values on this curve as supporting points in a table. This curve is internally reconstructed from this linearization table by linear interpolation of each supporting point. For this, two adjacent supporting points are each connected by a straight line, as is depicted in Figure 7.

Linear interpolation of the connection between the scattered light intensity and the effective turbidity values of a standard solution in FNU
Fig. 7: Linear interpolation of the connection between the scattered light intensity and the effective turbidity values of a standard solution in FNU

As an example, the light intensity measured in Fig. 7 at 2.4 is depicted as the turbidity value 2708 FNU.

Index

Contact distribution partner

{{selectedCountry.Name}} {{country.Name}}

Please select your businessarea

{{ba.Name}}

Please select

{{area.Name}}

Please select your businessarea

{{ba.Name}}
{{selectedCountry.Name}} {{country.Name}}
{{vm.getBusinessAreaStringByVendor(vendor)}} {{area.Name}}
{{vm.getBusinessAreaStringByVendor(vendor)}}
Leonardo Pio
Responsible for applications: Water, beverages & food, industrial processes for the cantons: AG, BE-DE, BL, BS, LU, NW, OW, TI, UR, SO, TI, VS-DE & ZG
Jacques Savary
Responsible for applications: Water, Beverages & Food, Industrial Processes for the cantons: BE-FR, FR, GE, JU, NE, VD & VS-FR
Vakant
Responsible for applications: Water, beverages & food, industrial processes for the cantons: AI, AR, FL, GL, GR, SH, SG, SZ & TG
Ihr Businesspartner für Getränke & Lebensmittel:
Für Wasser, Industrielle Prozesse, Verkehr & Umwelt kontaktieren Sie unseren Hauptsitz.

Your distribution partner for beverages & food:
For water, industrial processes, traffic & environment please contact our headquarters

Ihr Businesspartner für Getränke & Lebensmittel:
Für Wasser, Industrielle Prozesse, Verkehr & Umwelt kontaktieren Sie unseren Hauptsitz.

Your distribution partner for beverages & food:
For water, industrial processes, traffic & environment please contact our headquarters

Contact headquarters

Ralf Isenberg
Sales Manager ScrubberGuard
Öffnungszeiten:
Montag–Freitag 08:00–12:00 und 13:30–17:00
Feiertage & Betriebsferien:
Seppitag: 19. März 2026, Ostern: 03. – 06. April 2026, Auffahrt: 14. Mai 2026, Pfingstmontag: 25. Mai 2026, Fronleichnam: 4. Juni 2026, Bundesfeiertag: 01. August 2026, Maria Himmelfahrt: 15. August 2026, Allerheiligen: 01. November 2026, Maria Empfängnis: 08. Dezember 2026, Betriebsferien: 24. Dezember 2026 – 03. Januar 2027
Opening hours:
Monday–Friday 08:00am–12:00pm und 1:30pm–5:00pm
Public & company holidays:
St Joseph's Day: 19 March 2026, Easter: 03 – 06 April 2026, Ascension Day: 14 May 2026, Whit Monday: 25 May 2026, Corpus Christi: 4 June 2026, Federal Holiday: 01 August 2026, Assumption Day: 15 August 2026, All Saints Day: 01 November 2026, Conception of Mary: 08 December 2026, Company holidays: 24 December 2026 – 03 January 2027