8
7.
The electrode exposed in this manner to the air reaches an
equilibrium corresponding to the partial pressure of oxygen and thus
to saturation in water at the given temperature. Alternatively, rinse the
electrode with distilled water and then dip it into freshly air saturated
distilled water for calibration. The advection rate must be at least 10
cm/s
(stir!)
. Air saturated water can be prepared by shaking or
vigorously stirring distilled water for 10 minutes with free access of
air. The instrument shows the measured saturation, e.g. [SAt.=8.3]
and will calibrate automatically when readings are stable ([=] stops
blinking).
8.
After rinsing the electrodes with distilled water, immerse them in the
samples and read the display. The advection rate must be at least 10
cm/s
(stir!)
.
Measurements
with 2-point
calibration
1.
Before making measurements, check that the membrane is
undamaged and that there are no gas bubbles present in the
electrolyte space.
2.
Connect the electrode and switch the instrument on. After a few
minutes, the electrode is polarised and ready for making
measurements.
3.
Select the ppm (mg/l) or % range by pressing
MODE
. The display will
immediately show the measured oxygen according to the previous
calibration. Should you want to restandardise, press
CAL
.
4.
The display shows the salinity correction, e.g. [SAL=2.1%]. Leave this
value to zero unless you are going to measure in heavily salted
solutions such as e.g. sea-water (3.5%). Pre-set the proper value with
¿
or
À
and press
CAL
or
MODE
to cancel.
5.
The display shows the pressure correction, e.g. [P=1023hP]. Pre-set
the actual air pressure (hP) with
¿
or
À
and press
CAL
or
MODE
to
cancel.
6.
Press
¿
or
À
until the display shows [2.Point]. Press
CAL
to start the
calibration procedure.
7.
Dip the electrode into a saturated sodium sulphite solution (without
stirring). The instrument shows the measured zero-current (nA) of the
electrode, e.g. [O2.o=1.3] and will calibrate automatically when
readings are stable ([=] stops blinking).
8.
Rinse the electrode with distilled water and cautiously dry it without
rubbing (use cotton wool or soft filter paper). The electrode exposed
in this manner to the air reaches an equilibrium corresponding to the
partial pressure of oxygen and thus to saturation in water at the given
temperature. Alternatively, rinse the electrode with distilled water and
then dip it into freshly air saturated distilled water for calibration. The
advection rate must be at least 10 cm/s
(stir!
). Air saturated water
can be prepared by shaking or vigorously stirring distilled water for 10
minutes with free access of air. The instrument shows the measured
saturation, e.g. [SAt.=8.3] and will calibrate automatically when
readings are stable ([=] stops blinking).
9.
After rinsing the electrodes with distilled water, immerse them in the
samples and read the display. The advection rate must be at least 10
cm/s
(stir!
).
