and valuable Information regarding Turbidity measurement
Turbidity measuring is an important parameter for the quality assessment of liquids. Different standardized guidelines are published to guarantee the comparability of the measured turbidity values within the brew and water industry. There are only some company-, user- or application specific standard measurement procedures common in other industries, but the measurement methode is typically selected in accordance to the specific requirements of the various applications.
Turbidity measurement according to DIN/EN
Turbidity measurement according to EPA
Turbidity measurement according to MEBAK
Turbidity measurement according to EBC
Turbidity measurement according to ASBC
Turbidity measurement according to IOB
Formazin suspension and turbidity units based on Formazin
Kieselgur and turbidity units based on Kieselgur (DE diatomatious earth)
Direct light turbidity measurement and photometric turbidity units
International Organization for Standardization: ISO homepage
Deutsches Institut für Normung E. V. (German Institut for standardization): DIN/EN homepage
The standardisation work DIN supports the economical goal of a Common Market in Europe as well as a global market, free of technical obstacles. This requires an European and an international standardization. The European standardization is accomplished by three organizations CEN (Comité Européen deNormalisation), CENELEC (Comité Européen de Normalisation Electrotechnique) and ETSI (EuropeanTelecommunications Standards Institute). The national member organizations co-ordinate the European standards and implement these. The standardization organizations have - excluded ETSI - for each country only one member, who has to represent the entire interests of standardization of his country. The vote of the members during an election depends by the economic power of their nation. The German interests are represented by DIN (German Institut for standardization).
CEN homepage
CENELEC homepage
ETSI homepage
The DIN EN 27027 is the standard for turbidity measurement of potable water in Europe.
Turbidity measurement acccording EN 27027
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Turbidities lower than 40 FNU |
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Principle of measurement: |
ratio measurement: scatter light/transmission |
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Measurement angle: |
90° +-2,5° |
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Beam dimension: |
0° with maximum 1,5° convergence |
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Measurement wavelength: |
860nm / tolerance +-30nm |
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Calibration standard: |
Formazin |
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Turbidities higher than 40 FNU (see chapter "direct light tubidity" at the end of this page |
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Principle of measurement: |
Absorption (direct light measurement) |
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Measurement angle: |
180° |
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Beam dimension: |
0° with maximum 1,5° convergence |
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Measurement wavelength: |
860nm / tolerance +-30nm |
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Calibration standard: |
Formazin |
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Environmental Protection Agency EPA homepage
The US Environmental Protection Agency is an organization of the government of the United States, with the responsibility to coordinate and observe the protection of the environment and the protection of the human health. The EPA was founded under president Nixon on 2 December 1970. Seat of the organization is Washington, D.C. The administrator of the EPA is Stephen L. Johnson, its representative is Marcus Peacock. The organization counts currently approximately 17,000 employees.
One of the major areas of reposibility is to accomplish the environmental laws. The Office OF Criminal Enforcement, Forensics and training, shortened OCEFT, has its own execution and determination authority since 1982. It received the full police authorization in 1988. (OCEFT homepage)
The US EPA standard for turbidity measurement of potable water is different from the standard of the ISO/EN/ or DIN.
Turbidity measurement according US EPA.
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Principle of measurement: |
ratio measurement: scatter light/transmission |
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Measurement angle: |
90° (no tolerance specified) |
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Beam dimension: |
not specified |
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Measurement wavelength: |
full spectrum of a tungsten lamp |
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Calibration standard: |
Formazin |
Mitteleuropäische Brautechnische Analysenkommission
Central European brew-technical analysis commission MEBAK homepage
The MEBAK members are mainly the national and private brew-technical institutes of Germany, Austria, Czech republic and Switzerland as well as the national breweries and their suppliers.
The purpose of the association is the development of basic procedures to guarantee the quality of raw materials, intermediate, secondary and finished products as well as in the development of tools and equippement preferably used for malt- or beer production.
The MEBAK published a five volume edition of brew-technical analysis methods, which are internationally established and used as teaching material for the education and training of the brewers in institutes like technical university Munich Weihenstephan, Doemens institute or Charles university in Prague.
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Stability of beer (90° Side scatter) Recommendation acc. brew-technical analysis methods volume II 2.15.1.2 |
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Principle of measurement: |
ratio measurement: scatter light/transmission |
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Measurement angle: |
90° +-2,5° |
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Beam dimension: |
0° with maximum +-1,5° tolerance |
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Measurement wavelength: |
650nm / tolerance +-30nm |
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Calibration standard: |
Formazin / alternative: AEPA- turbidity standard (Styrene Divinylbenzol) |
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. Filtration control (forward scatter) (in addition to the above specified 90° measuring angle) |
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Principle of measurement: |
ratio measurement: scatter light/transmission |
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Measurement angle: |
11° - 25° |
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Beam dimension: |
not specified |
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Measurement wavelength: |
not specified |
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Calibration standard: |
Formazin |
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. Lauter wort (forward scatter) Recommendation acc. brew-technical analysis methods volume II 1.3 |
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Principle of measurement: |
ratio measurement: scatter light/transmission |
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Measurement angle: |
11° - 25° |
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Beam dimension: |
not specified |
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Measurement wavelength: |
not specified |
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Calibration standard: |
Formazin |
European Brewery Convention EBC homepage
The European Brewery Convention was founded in 1947 and supports the brew-scientific activities in Europe. The goal of the EBC is, the development of analytic methods to guarantee beer quality and to ensure a continuously high quality of raw materials and brewing procedures. Parameter like turbidity, color and the bitter value of beer are measured in EBC units. The current technology and engineering forum has been founded in 1990 by the EBC, with the task to develope simple technical procedures to optimize production and quality management in malt-houses and breweries. The successful work has caused the standardisation of many processes as well as the optimization of the hygienic design of process equippement and therefore a rising product quality.
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Stability of beer (90° Side scatter) |
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Principle of measurement: |
ratio measurement: scatter light/transmission |
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Measurement angle: |
90° (no tolerance specified) |
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Beam dimension: |
not specified |
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Measurement wavelength: |
not specified |
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Calibration standard: |
Formazin / alternative: AEPA- turbidity standard (Styrol-Divinylbenzol) |
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. Filtration control (forward scatter) (in addition to the above specified 90° measuring angle) |
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Principle of measurement: |
ratio measurement: scatter light/transmission |
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Measurement angle: |
11° - 13° |
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Beam dimension: |
not specified |
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Measurement wavelength: |
not specified |
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Calibration standard: |
Formazin / alternative: AEPA- Standard (Styrol-Divinylbenzol) |
American Society of Brewing Chemists ASBC homepage
The ASBC publishes like the EBC standard procedures to ensure quality of raw materials, brewing procedures and beer. The ASBC turbidity unit is not common in Europe and has been replaced partially as well in the USA by the EBC turbidity unit.
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Principle of measurement: |
not specified |
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Measurement angle: |
not specified |
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Beam dimension: |
not specified |
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Measurement wavelength: |
580nm (no tolerance specified) |
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Calibration standard: |
Formazin / measuring unit ASBC1 |
1 conversion rate: 69 ASBC = 1 EBC
Institut of Brewing & Distilling IOB homepage
The Institute of Brewing & Distilling (IOB or IBD) is an organization engaged in the education of brewers and distillers. The IOB recommends as well as EBC and ASBC guidelines for turbidity measurement instruments, which agree with the EBC guidelines.
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Principle of measurement: |
ratio measurement: scatter light/transmission |
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Measurement angle: |
90° (no tolerance specified) |
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Beam dimension: |
not specified |
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Measurement wavelength: |
not specified |
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Calibration standard: |
Formazin / alternativ: AEPA- turbidity standard (Styrol-Divinylbenzol) |
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. Filtration control (forward scatter) (in addition to the above specified 90° measuring angle) |
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Principle of measurement: |
ratio measurement: scatter light/transmission |
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Measurement angle: |
11° - 13° |
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Beam dimension: |
not specified |
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Measurement wavelength: |
not specified |
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Calibration standard: |
Formazin / alternative: AEPA- turbidity standard (Styrol-Divinylbenzol) |
Formazin is a poisonous chemical substance!
Please take notice to the safety instructions before handling Formazine.
Formazine is an aqueous suspension of an insoluble polymer and results from the reaction between a Hydraziniumsulfate and a Hexamethylentetramine. The median particle size of Formazin is 1,5 µm and the standard deviation of size is 0,6 µm.
A 1000 EBC / 4000 FTU Formazine suspension is recommended to make calibration standards for turbidimeters. The 1000 EBC / 4000 FTU suspension has a better shelf-life of up to 6 months compared to lower concentrations. In case you follow EN27027 (ISO 7027) you have to use a 400 TEF suspension to prepare your calibration standards*.
The stability of the Formazine suspension depends on the storage conditions. Formazine should be stored in darkness at a temperature of 8°C - 10°C to guarantee maximum stability.
The suspension has to be shaked carefully for at least 3 minutes before use. After shaking you have to wait for approximately 15 minutes to allow a degassing of the suspension. Than you have to stirr the suspension carefully for homogenisation. Make sure that no air bubbles occur during stirring of the suspension. Now you can make calibration standards with turbidities lower than 1000 EBC / 4000 FTU by diluting the suspension.
Please take notice:
- It is very difficult to prepare calibration standards lower than 0,5 EBC, this standards will be typically made by using specially distilled and filtered water and a high precision scale.
- The diluted calibration standards are substantially less stable than the 1000 EBC suspension. They should prepared and used immediately at the same day*.
- The turbidity of Formazine is named in different measurement units (see .
Turbidity units based on Formazine
The undiluted suspension has a turbidity value of:
1000 EBC (European Brewery Convention)
4000 TEF (Trübungseinheiten Formazin)
4000 FTU (Formazin Turbidity Units)
4000 FNU (Formazin Nephelometric Units / unit used for 90° side scatter turbidimeter only!)
4000 FAU (Formazin Attenuation Units /according to EN27027 direct light/absorption for turbidity >40 FNU)
40000 Helm units
69000 ASBC (American Society of Brewing Chemists)
* suspension of 100 EBC (400 FTU) has a shelf-life of maximum 2 weeks according DIN/EN 27027 (ISO 7027) guideline.
Please take notice to the safety instructions before handling of Kieselgur
Kieselgur (diatomatious earth, DE), is a whitish, powdered substance, which consists mainly of the silica dioxide shells of fossil algae (Diatomeen).
Kieselgur is used frequently for the calibration of turbidimeter. You can find different conversion factors in the literature compaired with formazine, because kieselgur is available in different qualities and particle sizes. The dry kieselgur powder has the advantage that it can be stored for an almost unlimited period of time. You can use the prepared calibration standard for 1-2 hours only, because kieselgur pours in water. Take notice to a homogenious diviation during a calibration with Kieselgur (frequently stirring) because Kieselgur has the tendency to sedimentate. Kieselgur is available from different vendors in different qualities and particle sizes you have to use the same vendor, quality, particle size and batch number to reproduce your calibration.
Typical calibration standards based on Kieselgur:
JTU* (Jackson Turbidity Unit)
JCU* (Jackson Candle Units
ppb (parts per billion)
ppm (parts per million)
g/l (gram per litre)
mg/l (milligram per litre)
%TS (percent total solids)
* The units JTU and JCU are based on the Jackson Candle Turbidimeter (Jackson candle tube) the forerunner of modern forward scattered light turbidimeter and not very common anymore.
The direct beam turbidity measurement is probably the most used turbidity measuring technique and is suitable for measuring ranges of approximately 40 up to 40000 TEF. The turbidity is measured typically in NIR spectrum at a wavelength of approximately 750nm, then color influences (colors absorb within the visible spectrum between 400-700nm only) cannot affect the turbidity values. These measuring method is e.g. recommendet in the German standard DIN 38404 part 2 and its European version EN 27027.
The standard recommends a manual measurement method to measure turbidities above 40 NTU, using a transparent cylinder and an insertable disc. The 90° scattered light method is recommended to measure lower turbidity values.
The standard contains as well a detailed procedure for the production of a 400 NTU formazine suspension and a guideline for the calibration of turbidimeters.
Typical turbidity units based on the principle of direct light measurement:
% (percent transmission)
A* (spectral Absorption value)
* The spectral Absorption value will be also designated as EXT (Extinktion), CU (Concentation Unit),
AU (Absorption Unit).