Operation
Turb
®
750 T
10
ba77234e04
07/2022
measuring with the aid of arrows printed on or markings. This refers to
sample cells and cells for calibration standards.
Prior to using a cell for the first time, the suitable position of the cell in the cell
shaft is determined and marked to make sure the optical path is not
disturbed. For the following measurements, the cell marking can just be
aligned with the meter marking.
The cell marking should be checked regularly and renewed as necessary.
The cell can be used until no suitable position for the optical path can be
found.
Determining a
suitable position in
the cell shaft
Marking a cell
Preparing the
sample
Air bubbles in the sample affect the measuring result to a massive extent
because they have a large scattering effect on the incident light. Larger air
bubbles cause sudden changes in the measured values whereas smaller air
bubbles are recorded by the instrument as turbidity. Therefore, avoid or
remove air bubbles:
We recommend that you do not treat any scratches in the cell
with oily liquids (not even with so-called "special silicone oils").
They could unnecessarily soil the meter and your working envi-
ronment. The optimum measurement accuracy is ensured by
aligning the cells. Scratched cells have to be replaced.
1 Clean the cell.
2 Stick the label for the marking onto the cell cap.
3 Fill the cell with a homogeneous solution (e.g. calibration standard
10.0 NTU).
4 Insert the cell.
5
Press and hold the
<START/ENTER
(.)
>
key.
Turn the cell slowly and check the measured value:
– The measured value at the position should be no maximum.
– At the directly neighboring positions there should not be any
sudden changes of the measured values. The deviations of
measured values at the neighboring positions should not
exceed the following values:
Measured value < 1 NTU: max. +/- 0.02 NTU
Measured value > 1 NTU: max. +/- 2 %
6 Release the
<START/ENTER
(.)
>
key.
Measurement starts. The measured value is displayed.
7 Mark the determined position (aligning) of the cell on the label.
The cell is now prepared for all following measuring and calibration
actions.
