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MR 29
Q: I am going to have a deployment in ocean water with constant salinity (35 ppt). Is it possible to pre-set the internal setting in the sensor, to avoid post
calibration?
A: Yes, this can be done. The default internal salinity is set to zero. If changing the internal salinity setting in the sensor (how this is done is described in the
operating manual) to the correct value the sensor should give the correct absolute saturation concentration in the salt water.
This means that when working in waters with a constant and known salinity this value can be entered into the sensor prior to deployment.
MR 30
Q: I measured dissolved oxygen in open water on a mooring with an Optode mounted on a SEAGUARD
10 cm/s) oxygen readings have a tendency to drop to lower readings (negative excursions). Is this indicating that these sensors have difficulties measuring
in low dynamic environments?
A: No, oxygen Optodes do not consume oxygen and are consequently not stirring sensitive.
Aluminium, Bronze) are normally corrosion protected by sacrificial anodes. As the anode disintegrates oxygen is consumed at all "naked" exposed metal
parts with which the anode is in electrical contact with. The oxygen consumption can be significant e.g. during its lifetime, normally 1-2 years, a 130 g Zn
anode mounted on a SEAGUARD
concentrations will form and can surround the oxygen sensors and lead to artificial dips in the oxygen readings. These effects are detectable in
environments in which oxygen is stable (e.g. less than 2 % variations over time periods of days-weeks) and when water currents are low (e.g. below 10
cm/s). In a vast majority of applications these effects are of low/no significance.
Mechanical and Maintenance
MM 1
Q: How do I clean the foil after a deployment if it has been fouled?
A: In all cases the cleaning procedure should be done with caution so that the protective foil coating (applies to slower responding foils) is not removed.
If the fouling is calcareous it can normally be dissolved with household vinegar (essig in German, eddik in Norwegian).
Another substance that can be used is commercially called muriatic acid, which is a 5% HCl solution (dilute solution by 50% should be tested to see how
well it dissolves growth before using a stronger concentration).
If needed, use cotton covered Q-tips (normally for cleaning of ears) to gently wipe of the remains after it has been softened by soaking in vinegar/HCl.
Optode can be submerged in vinegar/HCl overnight, or longer.
®
/RDCP/RCM pressure case can consume all oxygen in about 700 l of water. Water parcels with lower oxygen
®
Metal structures submerged in water (of e.g. Stainless Steel,
page 78 of 93
TD 269 OPERATING MANUAL
OXYGEN OPTODE 4330, 4831, 4835
June 2017
current meter. It seems that at low currents (below
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