Information for accurate measurements
52
Span calibration
Prior to span calibration, it is necessary to select standard turbidity substances.
Conventionally, refined powders of Kaolin and Formazin have been used. For tap water,
Polystyrene Latex (PSL) has been adopted.
For these turbidity standard substances, please use marketed products or HORIBA Advanced
Techno’s supplementary products.
Moreover, an optional span calibration bottle for span calibration is also available from
HORIBA Advanced Techno. If a span calibration bottle is used, signals as a substitute for a
standard solution can be obtained simply by shaking and mixing the span calibration bottle
strongly. However, even if an already-known liquid of turbidity is poured into a span calibration
bottle, span calibration cannot be performed at that value.
To use a span calibration bottle, attach the span calibration bottle to the turbidity meter
calibrated by turbidity standard substances beforehand. Test a measured value that is
indicated at that time, and perform span calibration by the operation that will be matched with
that value from next time.
The liquid components of a span calibration bottle are refined Kaolin, a trace amount of
dispersant (sodium pyrophosphate), and a sterilizing agent (hydrogen peroxide).
Place the span calibration bottle in zero water.The value of the span calibration bottle does not
remain unchanged. So replace the span calibration bottle with a new one once a year.
For span calibration of turbidity, use a standard solution of two degrees or higher. There is a
possibility that errors become larger in a standard solution that is near zero point.
Note
Place the span calibration bottle in zero water.If a span calibration bottle is placed in air, calibration
becomes impossible.
A solution of 0.3 to 0.9 times the measurement range is suitable for the turbidity of a span calibration
liquid.
Prior to span calibration, wash the inside of the cell adequately, and rinse it with clean water.
Perform calibration with a span calibration liquid of an already-known turbidity.
At the time of shipment from the factory, the span calibration liquid has been calibrated by
Formazin. Other turbidity standard substances may be calibrated and shipped upon request.
They are need to be calibrated by the user.
Adjust the coefficient to a turbidity given by Measured value x Span coefficient = Standard
solution.
Tip
After calibration, for details about preparation procedures, see “ Preparation method Formazin 4000
FTU ” (page 65) and “ Preparation method of Kaolin standard solution ” (page 66).
