wtw pHotoFlex, Operating Manual

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pHotoFlex / pHotoFlex Turb
110 ba75491e05 04/2009
Appendix 2: Turbidity values under 1 FNU/
NTU
With turbidity values (under 1 FNU/NTU), the measured value is
strongly influenced by the cell and its alignment.
In order to increase measuring accuracy with turbidity values under 1
FNU/NTU, calibration in the 0.02 FNU/NTU standard and later
measurement should be carried out in the same cell. For calibration in
the standards 10.0 and 1000 FNU/NTU follow the instructions on the
display.
Proceed as follows to measure turbidity values under 1 FU/NTU:
Calibration procedure:
Calibrate
z
after the calibration interval has expired
z
with a temperature change
Measuring
1 Press the <CAL/ZERO> key.
The menu-guided calibration begins.
2 Carry out calibration of the standards 1000 FNU/NTU and
10.0 FNU/NTU in a clean and unscratched cell according to
the menu guidance.
3 Fill the cleaned cell with the 0.02 FNU/NTU standard and
calibrate.
4 Mark the alignment of the cell.
5 Fill the marked and cleaned cell with test sample, align it
with the marking and measure.
6 If necessary, fill the marked and cleaned cell once more
with test sample and carry out further measurements.