placed in water, very small bubbles may remain attached to the platinum ring electrodes (seven). If
such a thing happens, the measured value of conductivity will be lower than the true one. To remove
these air bubbles, degrease the inside of the conductivity cell using cotton buds wetted with the
Conductivity Sensor Cleaning Solution or with liquid soap. Gently rotate the cotton bud against the
whole internal surface of the quartz cell. This will wet the platinum electrodes thus reducing the
surface tension of the cell and considerably decreasing the risk of trapped air bubbles.
This wetting operation must be always carried out before laboratory calibration tests.
7.4.2 Conductivity sensor cleaning
To clean the conductivity cell, use cotton buds and wet them with the CONDUCTIVITY SENSOR
CLEANING SOLUTION gently rotating the cotton bud against the platinum ring surfaces. Replace the
cotton bud after each ring cleaning. Repeat the above operation until the cotton buds used come out
perfectly cleaned. If the above cleaning solution is not available, use common liquid soap (and cotton
buds). If the above cleaning procedure is not enough to completely remove the contamination (for
instance carbonate), rotate inside the cell a small swab (10 mm diameter) wetted with 10% concentration
of hydrochloric acid. Even a maximum 30 % concentration can be used, if necessary.
7.5 REDOX SENSOR
The redox sensor can be contaminated by fouling or if some mud accidentally covers its sensitive tip.
In this case, it is wise to clean the sensor tip before each series of measurements. Use the abrasive paper
(which must be wet) provided in the OXYGEN SENSOR MAINTENANCE KIT. It is sufficient to
slightly rub the glass tip (where, at its centre, the platinum wire is placed) on the abrasive surface of the
paper two or three times. Wash the sensor tip with distilled water to remove residues.
7.6 TEMPERATURE SENSOR
The temperature sensor provides, via software, also the automatic temperature compensation for both
pH and oxygen channels. The temperature sensor is almost maintenance free; however, we suggest
cleaning it once a year with sandpaper (3M, 400 grid), included in the Oxygen Maintenance Kit, to
remove carbonate which, if present, will greatly increase its time constant.
7.7 PRESSURE SENSOR
The pressure sensor is almost a maintenance free device meeting the highest reliability standards and
thus reducing the chance of possible failure. Replacement of the pressure transducer could however
become necessary if an extension of the operating range (depth) is required. In that case, the whole
probe must be returned to Idronaut to allow replacement, calibration and performance check of the
sensor. The pressure transducer is located at the centre of the probe bottom flange. Protection against
fast thermal variation of water sample (thermocline) is obtained by means of a plastic o-ring cap
provided with a small hole in the centre. Lack of the protective cap may generate spikes of the signal
generated by the transducer when severe thermoclines are encountered.
7.8 INTERNAL BATTERY
The OCEAN SEVEN 310 CTD housing has, in its upper part, enough space to accommodate an internal
battery pack. The OS310 is powered by three 1.5V batteries or a single 3.6V battery but different types
of battery can be installed in the CTD housing.
➢ 3 x size “AA” Alkaline 1.5V battery assembled in a single pack 5V
➢ 1 x size "AA" Lithium non rechargeable battery 3.6V, 2.4Ah
➢ 1 x size “C”
Lithium non rechargeable battery 3.6V, 8.4Ah
➢ NiMH rechargeable IDRONAUT custom battery pack (3x1.2 AA) 3.6V, 2.6 Ah
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