Hanna offers turbidimeters based on the following two Methods:


  • ISO 7027 “Water Quality: Determination of Turbidity”
  • USEPA Method No.180.1, “Turbidity”

Specific wavelengths are recommended for each method. For the USEPA and Standard Methods, the wavelength in the visible range of the spectrum is recommended, where the European ISO method requires an infrared light source.

The Infrared Method (ISO 7027)

The ISO 7027 standard specifies the key parameters for the optical system to measure turbidity for drinking and surface water, using the formazin-based metric method. ISO turbidity meters operate by passing a beam of infrared light through a vial containing the sample to be tested. The light source is a High Emission Infrared LED. A sensor positioned at 90° with respect to the direction of the light detects the amount of light scattered by the undissolved particles present in the sample. A microprocessor converts these readings into FTU (FNU) values.

The US Environmental Protection Agency Approved Method (180.1)

The USEPA Method 180.1 specifies the key parameters for the optical system to measure turbidity for drinking, saline and surface water, in a 0 to 40 NTU range, using the nephelometric method.

Meters compliant with EPA approved methods are designed to meet or exceed the criteria specified by the USEPA Method 180.1 and Standard Method 2130 B.

Hanna Instruments offers a wide variety of instrumentation for measuring turbidity. Products include benchtop and portable meters that are based on ISO and EPA methodology. Specialized portable meters are available for monitoring bentonite in wine and haze in beer.


Benchtop Turbidity Meters

Benchtop turbidity meters include versions based ISO and EPA methods. Meters based on the EPA method have NTU, Nephelos, and EBC as units of measure. A benchtop based on the EPA method is also available to measure chlorine. Meters based on the ISO method can display results as FNU, FAU, NTU, and EBC.

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