Rev. 0-401
5
Model GLI-9143 Portable D.O. Meter
cally polarizes the probe when it is switched
on.
Calibration is simple and is recommended
every time the meter is switched on.
1.
Make sure the probe is ready for meas-
urement (see PROBE PREPARATION),
i.e. the membrane is filled with electrolyte
and the probe is connected to the meter
and properly polarized.
2.
Switch the meter on.
3.
"COND" appears on the
display to inform you
that the probe is in auto-
conditioning (automatic
polarization) mode.
4.
Once "COND" disappears, the probe is
polarized and the instrument can be cali-
brated.
5.
For an accurate calibration, it is recom-
mended to wait an additional
5 or 10 minutes to ensure
optimum conditioning of the
probe.
6.
Remove the protective cap.
7.
Press CAL. "----" appears
on the larger LCD to-
gether with "CAL" to
indicate that the instru-
ment is in calibration mode.
8.
The instrument will
automatically standard-
ize itself to the actual
saturation value. After
approximately 1 minute,
it will show "100%" on
the LCD and a small
"SAMPLE" to indicate
that the calibration is complete.
9.
Press FACTOR and ensure F1 and F2
are set to the appropriate altitude and
salinity values (see ALTITUDE and
SALINITY COMPENSATION).
NOTE:
The instrument must be calibrated
whenever the probe, membrane or
the electrolyte is changed.
To exit the calibration mode
during calibration, press CAL.
The display may be switched
from readings in % saturation
to ppm without re-calibration,
by simply pressing RANGE.
MEASUREMENT
Make sure the meter has been cali-
brated and the protective cap has
been removed. Immerse the tip of
the probe in the sample to be tested
and ensure that the temperature
sensor is also immersed.
To display values in % satura-
tion, press RANGE.
For accurate dissolved oxygen measure-
ments, a water movement of at least 30 cm
(12 inches)/sec is required. This is to ensure
that oxygen depleted on the membrane sur-
face is constantly replenished. A moving
stream will provide adequate circulation.
During field measurements, this condition
may be obtained by manually stirring the
probe. Accurate readings are not possible
while the liquid is stationary.
During laboratory measurements, the use of
a magnetic stirrer to ensure a certain agita-
tion of the fluid is recommended. This way,
any errors due to the presence of air bubbles
on the membrane surface are minimized.
