7 PROBE MAINTENANCE
All the maintenance procedures necessary to keep the probe in its best operating conditions are
described in this section. The actions described mainly pertain to the sensors of the probe. In detail, this
section includes:
➢ Oxygen sensor.
➢ Reference sensor.
➢ pH sensor.
➢ Conductivity sensor.
➢ Redox sensor.
➢ Temperature sensor.
➢ Pressure sensor.
➢ Battery endurance and recharge.
➢ Routine maintenance schedule.
The following recommendations are to be followed when performing the sensor maintenance;
suggestions on maintenance frequency are provided in a dedicated section.
IMPORTANT NOTE
The following section 7.1 refers to the oxygen sensor – standard versions (150 and 700 bar) only. It is
not applicable when the probe is equipped with the MAINTENANCE-FREE DISSOLVED OXYGEN
SENSOR (5 bar) or the IDRONAUT BLUE CAP OPTICAL DISSOLVED OXYGEN SENSOR.
7.1 OXYGEN SENSOR
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.
7.1.1 Important remark on oxygen measurement
Most polarographic oxygen sensors take 5 to 10 minutes after they have been switched on to polarize
and become stable. To overcome this limitation, the Idronaut OS310 has been fitted with a small internal
rechargeable device, to maintain polarization of the oxygen sensor continuously. However, if the probe
is not used for several days, the polarizing device become completely discharged. It is recommended
that the probe should be switched ON (and streaming real-time data) for at least a few minutes to
completely charge the polarization device before proceeding with the calibration.
7.1.2 Green membrane
IDRONAUT green membrane is ideal for profiling acquisitions. To allow proper sample stirring, the
probe must be lowered at a rate of at least 0.2 m/sec. The following table shows the characteristics of the
green membrane:
Application Membrane colour Time Stirring Membrane material
const.(a) effect(b)
Profiling Green 3 sec. 5%(c) 25µ, Teflon®
Note
(a) Time constant = nitrogen to air.
(b) Stirring effect = measuring difference between a sample well stirred and a completely stagnant one.
(c) Algorithm compensates for this 5% reading decreasing.
All values of the table are given for a temperature of 25
o
C. The probe is delivered with the green membrane
installed.
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