Hach-Lange TSS PORTABLE Handheld Instrument for Turbidity_Suspended Solids Manual - Manual (Page 23)

Figure 8 Homogeneity in %
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Section 5 Operation
5.1 Calibration
Turbidity measurements do not need to be calibrated, as a standardized calibration curve
according to ISO 7027 is stored in the instrument. It is possible to create a
customer-specific calibration of the turbidity curve. If the standard curve has been altered,
a star (*) appears before the measurement point.
Solids measurements must be calibrated on site. It is not possible to define a general
standard for this as the type and composition of the solid particles can differ greatly.
5.1.1 Important notes for calibration
Calibration containers 
In order to avoid reflections of the measurement beam on the base and walls of the
container, a black—or at the very least dark-colored—container should be used for
calibration.
The probe can also remain in the tank so long as a representative laboratory sample can
be taken at this point.
Measured variable (homogeneity)
100 % represents a homogeneous measurement medium. After approximately
10 seconds, this measured variable provides a representative statement about the
homogeneity of the measurement medium. The homogeneity is displayed as a
percentage value after an individual measurement (
Figure 8 ).
Replacing the probe
As the calibration is carried out for the measuring system (meter and probe), only the
probe supplied may be used for the measurements. If a different probe is used, the
equipment must be recalibrated.
Note: If you have changed the probe, the error message "Incorrect probe" is displayed. Register the
new probe under
MENU > SYSTEM with the code 390 (see section 3.4.1, page 14 ). This releases all
the calibration curves for the solid matter measurement. The instrument then needs to be
recalibrated.
1 Homogeneity