Hanna Instruments HI2400 Instruction Manual page 9

INSTRUMENT START-UP
• Turn the instrument on by pressing the ON/OFF switch.
• All LCD tags are displayed and a beep is generated while the instru‑
ment performs a self test.
• The instrument will display " " blinking until initialization is
complete.
• After a few seconds "Cond" message appears on the LCD to inform the
user that the probe is in auto‑conditioning (automatic polarization)
mode.
• When this message disappears, the probe is polarized and the
instrument can be calibrated.
• If the probe is disconnected, the meter will display "----".
PROBE POLARIZATION
The probe is under polarization with a fixed voltage of approximately
800 mV. Probe polarization is essential for stable measurements with
the same recurring degree of accuracy.
With the probe properly polarized, oxygen is continually consumed when
it passes through the sensitive diaphragm and dissolves in the electrolyte
solution contained in the probe. If polarization is interrupted, the elec‑
trolyte solution continues to be enriched with oxygen until it reaches an
equilibrium with the surrounding solution.
Whenever measurements are taken with a non‑polarized probe, the
oxygen level revealed is both that of the tested solution, as well as that
present in the electrolyte solution. This reading is incorrect.
The calibration of this instrument is very simple. Before proceeding with
the calibration, make sure the probe is ready for measurements (see
page 8), i.e. the membrane cap is filled with electrolyte and the probe
is connected to the meter and properly polarized.
For an accurate calibration, it is recommended to wait at least 15 minutes
to ensure precise conditioning of the probe. Keep the protective cap on
during polarization time and remove it for calibration and measurements.
Follow the calibration procedure (see page 11).
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