Hanna Instruments HI 88713 - Manual (Page 3)

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ABBREVIATIONS ABBREVIATIONS ABBREVIATIONS ABBREVIATIONS ABBREVIATIONS
NTU Nephelometric Turbidity Units
FAU Formazin Attenuation Units
FNU Formazin Nephelometric Units
ISO International Organization for
Standardization
LCD Liquid Crystal Display
RTC Real Time Clock
RH Relative Humidity
ID Identification
EBC European Brewery Comitee
Turbidity is the optical property that causes light to be scattered and absorbed, rather than transmitted.
The scattering of the light as it passes through a liquid is caused by the suspended solids. The higher the
turbidity, the greater the amount of scattered light. The molecules in a very pure fluid scatter light to a
certain degree, no solution will have zero turbidity.
The ISO 7027 Method specifies the key parameters for the optical system and the method to
measure the turbidity of water.
The HI 88713 Turbidity bench meter is designed to meet or exceed the criteria specified by the ISO
7027, DIN 38404 and NF EN 27027.
The light beam that passes through the sample is scattered in all directions. The intensity and pattern
of the scattered light is affected by many variables including the wavelenght of the incident light,
particle size and shape, refractive index and color.
The optical system of the HI 88713 turbidity bench meter uses an IR LED, a scattered light detector
(90
0 ) and a transmitted light detector (180 0 ).
PRINCIPLE OF OPERATION PRINCIPLE OF OPERATION PRINCIPLE OF OPERATION PRINCIPLE OF OPERATION PRINCIPLE OF OPERATION
The HI 88713 Turbidity bench meter features G.L.P. (Good Laboratory Practice) functions that allow
traceability of the calibration conditions. The last calibration points as well as time and date
The HI 88713 Turbidity bench meter has a user-friendly interface with an easy to understand,
graphical LCD. Comprehensive contextual help is available at a simple key press. All messages and
help screens are available in several languages. Furthermore, a tutorial mode guides the user step by
step through the analysis process.
The HI 88713
HI 88713 HI 88713 HI 88713 HI 88713 features a logging function that can hold up to 200 measurements in the internal
memory. Data can be viewed directly on the screen or it can be downloaded to a PC for further
analysis using the HI9200 Windows
® compatible software.
For the ratio turbidity mode, the microprocessor of the instrument calculates the NTU value, from the
signals that reaches the two detectors, by using an effective algorithm. The optical system and
measuring technique compensate the color interference and also the LED intensity fluctuations,
minimizing the need of frequent calibration.
For the FNU and NTU non ratio modes the turbidity is calculated from the signal that reaches the
scattered light detector (90°).
In FAU mode the turbidity is calculated from the signal that reaches the direct light detector, while
in NTU ratio mode the turbidity is obtained from signal ratio on scatter and transmitted light
detectors. The non ratio methods are more sensitive to the LED intensity fluctuations.
The lower detection limit of a turbidimeter is determined by the “stray light”. Stray light is the light that
reaches the detectors and is not caused by light scattering from suspended particles.
The optical system of HI 88713 instrument is designed to have very low stray light, providing accurate
results for low turbidity samples. However, special care must be taken when measuring low turbidities (see
page 9 “General Tips for an Accurate Measurement” for sample preparation and measuring techniques).
MEASUREMENT UNITS
The meter is using specific units according to the selected measurement mode. For NTU modes the
EBC unit option is available 1 EBC=0.245 NTU. When measuring in NTU modes a conversion to
EBC units is also available 0.245 NTU=1 EBC.