idronaut Ocean Seven 304Plus Operator's Manual page 65

APPENDIX A – DISSOLVED OXYGEN SENSOR
A.7.3 Membrane replacement (oxygen membrane cap)
Conditions which could require the membrane and electrolyte replacement are the following:
 Calibration is not systematically achieved (try at least three times) and "OXYGEN SENSOR
CALIBRATION ERROR" appears on screen.
 The oxygen sensor responds more slowly than usual or drifts.
 The membrane of the cap is mechanically damaged and shows leakage, holes or scratches.
 Read-out of over 0.2 ppm is displayed when carrying out the sensor check in the absence of
oxygen.
 The oxygen sensor, filled with electrolyte, has been stored for a long time at temperatures outside
those recommended (- 10 to 40
A.7.4 Replacement of membrane can be done using the OXYGEN SENSOR MAINTENANCE KIT:
 Locate and pull out the following parts from the maintenance kit:
 one oxygen measuring "green" membrane;
 one o-ring;
 o-ring mounting tool.
 Remove the protection ring from the membrane cap. Remove and discard the black o-ring and the
membrane(s).
 Fit the new o-ring over the mounting tool and roll it down to the widest part of the tool.
 Place the cap on a desk top with its narrow end facing up.
 Position the measuring membrane "green" on top of the cap.
 Place the widest part of the tool against the membrane. Slightly pressing the tool, slide the o-ring
carefully into the slot of the cap thus holding the membrane in position.
 Cut away excessive membrane, with fine scissors, far from the o-ring to avoid damaging the
membrane.
 Finally, recap the protective plastic ring.
A.7.5 Oxygen sensor cleaning
During the calibration procedure, the oxygen sensor current is shown:
Checking oxygen sensor:
Current: XXX nA. % of last calibration. XXX.X%
The acceptable current is 30-90 nA.
IDRONAUT – Brugherio (MB)
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OCEAN SEVEN 304Plus CTD
57
12-2015