Q: Is there general guidance for creating the most accurate calibration curve for suspended solids?
A: Hach recommends selecting a calibration point with a value in the upper third of the range
expected. Start with a single point calibration in that range. In case a single point calibration is
not sufficient, the error “message Calibration insufficient –“or “Calibration insufficient +” will
guide you to set up an appropriate curve, thus will provide a more accurate measurement.
Q: Does Hach have a general statement that explains how the solids calibration correlates to
measured value?
A: Yes, A single point calibration draws a straight line from the probes zero point to the point of
calibration; however the mathematical transformation of the different signals of the different
detectors is nonlinear. When a calibration curve consists of 3 points the curve is created by
connecting the straight lines. The course may not hit the zero e.g. because the medium itself is
colored and absorbs light. \
Q: Is there any difference how the probe is operating when selecting between the turbidity units
FNU, NTU, and EBC?
A: FNU and NTU are equal and are just a different name for the unit of turbidity. EBC is the unit
for turbidity defined by the European Brewery Convention. It is meant to be used by breweries:
1 FNU = 0.25ECB
Q: Does the specification of 290 measurement values only include what is stored in the DATA menu?
A: The 290 measurement values are the summed values that can be stored in the calibration
and data menus.
Q: Does the air bubble compensation apply to both the turbidity and suspended solids measurement?
A: Yes, the software applies air bubble compensation to both types of measurements.
Q: How should the homogeneity % be interpreted?
A: The % homogeneity is an indicator for the quality of your sludge measurement. Between 80%
and 100% the result of your measurement is authentic. Homogeneity has nothing to do with the
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