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Check the probe's status
The glass body covering the cathode of the polarographic probe and the membrane on the probe's
head should not be damaged.
If there are cracks in the glass body, the probe must be replaced. If the Oxygen-permeable
membrane is damaged, dirty or obstructed it must be replaced. When the probe's head is
unscrewed, the body in glass is not protected. Handle it with care to avoid collisions that could
damage irreparably the glass covering the cathode.
Control the zero of the probe
Compensation of the zero (offset) of the probe is already done in the factory.
The user can control the offset by immersing the probe in the 0.0% dissolved Oxygen solution (DO
9700):
•
Pour a small quantity of 0.0% dissolved Oxygen solution into a container, after suitably washing
the container with distilled water,
•
Insert the probe in the zero solution and wait at least 5 minutes,
•
The instrument should indicate a saturation index < 0.3%.
Dissolved Oxygen probe storage
When the dissolved Oxygen probe is not used for long periods, it should be disconnected from the
instrument to avoid useless consumption of the electrolyte solution.
Always keep the electrode wet using the special cap provided with the probe and filled with distilled
water.
Polarographic probe and galvanic probe: differences
To help choosing between the use of polarographic or galvanic probe, the following table
summarizes the main differences between the two probes.
Polarographic probe
Galvanic probe
Polarization time
After connecting the probe to the
instrument it is necessary to wait
at least 5-10 minutes before
taking the measurement.
Polarization is not needed. After
connecting the probe to the
instrument it is possible to take
the measurement immediately.
Power consumption
If connected to the instrument, the
probe is also powered when the
instrument is off, decreasing the
life of the batteries.
Power is not needed. Longer life
of the batteries, feature important
in field measurements.
Cleaning
Requires frequent cleaning of the
anode.
Maintenance of the electrodes is
not needed.
Electrolyte replacement
Requires frequent replacement of
the electrolyte solution.
It can also work months without
replacing the electrolyte solution.
Drift
The measurement of the zero has
the tendency to drift.
The measurement of the zero is
stable. Higher accuracy when
measuring low oxygen
concentrations.
