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Version 2.1
Update: April 2016
PONSEL Mesure
– Aqualabo Contrôle
35 Rue Michel Marion
– 56850 CAUDAN, FRANCE
Tel.: +33(0)2 97 89 25 30
– Fax: +33(0)2 97 76 55 72
7.2 Maintenance of digital sensors:
7.2.1 OPTOD sensor.
General description
Oxygen: luminescent membrane sensitive to the oxygen level in the medium
being analyzed. Gaseous exchange between the membrane’s material and
the medium.
Temperature: NTC thermistor.
Materials
316L stainless steel version: polyamide, silicone and quartz; polyurethane
sleeve around cable.
Titanium version: polyamide, silicone and quartz; polyurethane sleeve around
cable.
Precautions
The membrane is sensitive to:
-
chemicals (organic solvents, acids, hydrogen peroxide),
-
mechanical stresses (impacts, abrasion, tearing).
Measurement/Interference
When measuring, check that bubbles do not become trapped under the
membrane.
If chlorine is present, the quality of the measurement will be impaired
(overestimate of the level of dissolved oxygen).
When immersing the sensor in the medium to be measured, wait until the
sensor's temperature has stabilized before taking the reading.
To optimize the service life of the sensor, we recommend a measurement
interval (refresh rate) of more than 5 seconds.
Operating temperature
0 °C to 50 °C
Temperature compensation effective over the range 0-40 °C
Servicing
After each use, rinse the sensor and the membrane carefully in clean water.
If deposits such as biofilm or sludge persist, wipe the membrane carefully with
a soft cloth or absorbent paper.
Caution
: for the titanium version, clean the body of the sensor with acetone
(do not use methylated spirits, ethanol or methanol).
Caution
: only unscrew the sieve cap containing the DODISK when replacing
the disk.
If the sieve cap has to be replaced, screw the new sieve cap on slowly to
allow the air to escape slowly.
Storage
Keep the membrane hydrated using the protective bag and a dampened
absorbent wad of material (e.g. cotton wool. After being stored in dry
conditions, rehydrate the membrane for 12 hours by immersing the sensor in
water.
Storage temperature
- 10 °C to + 60 °C
Oxygen calibration
Using a clean sensor, occasionally check the 0% Sat value by immersing the
sensor in a sulfite solution in water (sulfite concentration <2%). If there is a
zero error, perform a complete calibration of the sensor.
Caution: do not allow the sensor to remain in contact with the sulfite solution
for more than 1 hour.
The 2-point calibration is performed using a sulfite solution (for the offset)
then, after rinsing and drying, the sensor’s gain is determined by exposing the
sensor to moisture-saturated air (or to clean water saturated with air).
Temperature calibration
The calibration of the temperature sensor is a 2-step process:
- step 1 (offset): the sensor is placed in a container containing a water bath
and ice,
