Hanna Instruments HI 9146-04 - Manual (Page 5)

8 9
• For an accurate calibration, it is recom-
mended to wait an additional 5 or 10 min-
utes to ensure optimum conditioning of the
probe.
• Remove the protective cap.
• Press CAL. "----" appears
on the larger LCD together
with "CAL" to indicate that
the instrument is in calibra-
tion mode.
• The instrument will auto-
matically standardize itself
to the actual saturation
value. After approx. 1
minute it will show "100%"
on the LCD and a small
"SAMPLE" to indicate that
the calibration is complete.
• Press FACTOR and ensure F1 and F2 are
set to the appropriate altitude and salinity
values (pages 10-11).
Notes: • 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 mg/
L without recalibration,
by simply pressing
RANGE.
CALIBRATION
PROBE POLARIZATION
The probe is under polarization with a fixed
voltage of approximately 800 mV.
Probe polarization is essential for stable mea-
surements with the same recurring degree of
accuracy.
With the probe properly polarized, oxygen is
continually "consumed" by passing through
the sensitive diaphragm and dissolving in the
electrolyte solution contained inside the probe.
If this operation is interrupted, the electrolyte
solution continues to be enriched with oxygen
until it reaches an equilibrium with the sur-
rounding solution. Whenever measurements
are taken with a non-polarized probe, the
oxygen level indicated is that of the test solu-
tion as well as any oxygen present in the
electrolyte solution. This reading is obviously
incorrect. The Hanna oxygen meter shown
here automatically polarize the probe when
they are switched on.
Calibration is simple and is recommended
every time the meter is switched on.
•
Make sure the probe is ready for measure-
ment (see page 5), i.e. the membrane is
filled with electrolyte and probe is con-
nected to the meter and properly polarized.
• Switch the meter on.
• "COND" appears on the
display to inform you that
the probe is in auto-condi-
tioning (automatic polariza-
tion) mode.
• Once "COND" disappears
the probe is polarized and
instrument can be calibrated.
ON/OFF
CAL
CAL
SAMPLE
%
°C
CAL
RANGE