21
•
Performing the measurement
Remove the protective cap of electrode, rinse it with distilled water; dab it with paper towel and dip in the
solution to analyse. Gently stir and wait until the value stability, when the icon
appears on the display,
take the reading.
Note
: the polarographic sensor tends to consume the oxygen, and thus reducing gradually the detected
value. Make sure that there is a minimum flow in the sample to analyse; if you are working in a laboratory,
keep the sample stirred.
•
Barometric pressure compensation
Since the measurement of the partial pressure of the dissolved oxygen is related to the barometric pressure,
this instrument is able to compensate each variation, thanks to the integrated barometric sensor.
In order to view the barometric pressure measured by the instrument, press the key
during
measurement and scroll through the measurement parameters: %O
2
↔
mg/l
↔
mbar.
Probe DO 7 maintenance
If the instrument does not calibrate or the reading does not stabilize, it is necessary to perform a
maintenance of the probe. In order to perform the maintenance, follow these steps in order:
•
Replacement of electrolyte
•
Cleaning of anode and cathode
•
Replacement of membrane
•
Electrolyte replacement
•
Remove the membrane cap from the sensor, check that it is not punctured or damaged; if it is
intact, it can be used again, otherwise it must be replaced.
•
Wash the membrane and the sensitive part of the sensor with distilled water; remove any salt
residue
and dry with paper towel.
Be very careful when handling the sensor and the membrane. Falls, shocks or crushing can damage
the sensor and/or membrane.
•
Fill the membrane cap with distilled water at half level and screw it on the sensor (pay attention in
the fixing phase, since the membrane does not have to be screwed strongly up to end run, because
it can be damaged). Stir gently, unscrew the membrane and empty it completely; in this way, any
traces of water or dust will be eliminated.
•
Refill the membrane with new electrolyte; this time, fill it completely and screw the sensor making
sure that no air bubbles appear inside. A light leakage of electrolyte during the screwing of
membrane, ensures that no air bubble will be created.
•
Wash the probe and leave it in distilled water for at least half an hour, in order to rehydrate the
membrane.
Perform the
Calibration of the sensor.
If it does not work, proceed with the
Maintenance of the anode and
the cathode.