20
SECTION 2, continued
intermediate results. The initial value is displayed after about
11 seconds and the display is updated every 1.2 seconds until all ten
measurements are taken (about 20 seconds). After this, the lamp turns
off, but the final measured turbidity value continues to be displayed
until another key is pressed.
When not in signal average mode, the final value is displayed after
about 13 seconds.
Accurate turbidity measurement depends on good measurement
technique by the analyst, such as using clean sample cells in
good condition and removing air bubbles (degassing).
Refer to Section 2.3 on page 22 for a detailed discussion
of measurement techniques.
2.2.1 Turbidity Measurement Procedure
1. Collect a representa-
tive sample in a clean
container. Fill a sample
cell to the line (about
15 mL), taking care to
handle the sample cell by
the top. Cap the cell. (See
Section 2.3 on page 22
for more information
about collecting a
representative sample).
Note: The instrument auto-
matically shuts off after
5.5 minutes if no key-
strokes occur. To resume
operation, press
I/O.
2. Wipe the cell with
a soft, lint-free cloth to
remove water spots and
fingerprints.
3. Apply a thin film of
silicone oil. Wipe with a
soft cloth to obtain an
even film over the entire
surface.
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