Hanna Instruments HI 2400 - Manual (Page 8)

8
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
instrument 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 electrolyte 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 7), i.e. the membrane cap is filled with electrolyte
and the probe is connected to the meter and properly polarized.