idronaut Ocean Seven 304Plus Operator's Manual page 64

APPENDIX A – DISSOLVED OXYGEN SENSOR
For example, on entering a correction coefficient of 10, the read-out will be multiplied by a factor of
10. For instance, to apply a double compensation due to the barometric effect and to the oxygen
depletion, the following operation must be used
i.e. __________
1.05 x 1.216 = 1.2768 total coefficient to be applied.
A.7 MAINTENANCE (required for the standard oxygen sensor only)
To ensure the best performance of the oxygen sensor, frequent full replacement of electrolyte (every
month) and membrane (every 6 months) is to be performed.
A.7.1 Available membrane
The performance of the oxygen sensor depends on the type of membrane being used.
IDRONAUT uses a proprietary 25µ,Teflon® membrane.
A.7.2 Refilling oxygen sensor cap with electrolyte
 Switch the CTD ON and, if possible, achieve oxygen calibration.
 Locate the oxygen sensor on the CTD; then unscrew and remove the cap. Pay attention not to
damage the glass tip of the sensor.
 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.
 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 read-out is higher, there is most probably a film of moisture still in contact with the
sensor tip. Carefully dry the sensor tip.
 Carefully fill the membrane cap with the O
deposited directly into the 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.
 Gently screw the membrane cap onto the sensor body, thus allowing the electrolyte in excess to be
drained, then securely tighten the membrane cap.
 Dry the sensor, and the membrane in particular, with a lint-free paper towel.
Note
After electrolyte refilling, recalibrate the oxygen channel.
IMPORTANT
 Maximum stability of read-out is achieved 30 minutes after the membrane cap and/or electrolyte
replacement, thus enabling
however, be carried out within a few minutes after the membrane cap replacement provided that a
calibration is performed.
 While the CTD is not used, the oxygen sensor polarization remains active since the necessary
power is provided by a rechargeable battery placed inside the CTD. Battery back-up is performed
when the CTD is switched ON.
 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 sensor life.
 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.
IDRONAUT – Brugherio (MB)
760
= Barometric correction coefficient = 1.216
625
1.05 = Stirring effect or oxygen depletion coefficient standard value (5%)
the sensor to reach a good polarization level. Oxygen analysis can,
electrolyte; do this in such a way that drops are
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OCEAN SEVEN 304Plus CTD
56
12-2015