7.1.3 Refilling oxygen sensor cap with electrolyte
1) Switch the probe ON and, if possible, achieve oxygen calibration.
2) Locate the oxygen sensor on the probe, then unscrew and remove the cap. Pay attention not to
damage the glass tip of the sensor.
3) Wash the silver and glass assembly with distilled water and dry it with a lint-free paper towel. Do
not touch the internal parts of the sensor with the fingers.
4) In this condition, with the sensor tip duly dried and cleaned, the sensor should read less than 0.2
ppm (if calibration has been previously achieved). The sensor should not be touched during this
check. If the readout is higher, there is most probably a film of moisture still in contact with the
sensor tip. Carefully dry the sensor tip.
5) Carefully fill the membrane cap with the O2 electrolyte; do this in such a way that drops are
deposited directly into bottom of the membrane in order to prevent the formation of big air bubbles
in the cap. To eliminate trapped air bubbles, gently tap the membrane cap.
6) Gently screw the membrane cap onto the sensor body, thus allowing the electrolyte in excess to be
drained and then securely tighten the membrane cap.
7) Dry the sensor, and the membrane in particular, with a lint-free paper towel.
Note
After electrolyte refilling, recalibrate the oxygen channel.
IMPORTANT
A. Maximum stability of readout is achieved 30 minutes after the membrane cap and/or electrolyte
replacement, thus enabling the sensor to reach a good polarization level. Oxygen analysis can,
however, be carried out within a few minutes after the membrane cap replacement, provided that a
calibration is performed.
B. While the probe is not used, oxygen sensor polarization remains active since the necessary power is
provided by a rechargeable battery placed inside the probe. Battery back-up is performed when the
probe is switched ON.
C. If necessary, the whole electrolyte must be replaced. ”Topping-up” with fresh electrolyte must not
be carried out since the solution would be contaminated by the old one thus resulting in a reduction
of life.
D. It is recommended that only the IDRONAUT electrolyte be used, since its composition and pH
guarantee the best performance and minimize the formation and growing of silver chloride on the
anode.
7.1.4 Membrane replacement (oxygen membrane cap)
Conditions which could require the membrane and electrolyte replacement are the following:
1) Calibration is not systematically achieved (try at least three times) and ”OXYGEN SENSOR
CALIBRATION ERROR” appears on screen.
2) The oxygen sensor responds more slowly than usual or drifts.
3) The membrane of the cap is mechanically damaged and shows leakage, holes or scratches.
4) Readout of over 0.2 ppm is displayed when carrying out the sensor check in the absence of oxygen.
5) The oxygen sensor, filled with electrolyte, has been stored for a long time at temperatures outside
those recommended (- 10 to 40
o
C).
7.1.5 Replacement of membrane(s) using the OXYGEN SENSOR MAINTENANCE KIT:
1) Locate and pull out the following parts from the maintenance kit:
❖ One oxygen measuring ”green” membrane (internal).
❖ One O-ring.
❖ O-ring mounting tool.
2) Remove the protection ring from the membrane cap. Remove and discard the black o-ring and the
membrane.
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