Maintenance
57
Dissolved
Oxygen
Probe
Maintenance
The DO probe body is made of PEI.
A temperature sensor provides temperature measurements of the sample. Use
the protective cap when the probe is not in use. To replace the membrane or
refill with electrolyte, proceed as follows:
For a new probe, remove the protective shipping tube by gently
twisting and pulling it off the body of the probe (see fig. 1).
If the membrane was previously installed, unscrew the membrane
cap by turning it clockwise (see fig. 2).
The new membrane cap should be rinsed with electrolyte solution.
Refill with clean electrolyte solution.
Gently tap the sides of the membrane cap to ensure that no air
bubbles remain trapped. Do not tap the bottom directly with your
finger, as this will damage the membrane.
Make sure that the rubber O-ring sits properly inside the membrane
cap. With the sensor facing down, slowly screw the membrane cap
clockwise. Some electrolyte will overflow.
The platinum cathode (DO Probe Diagram, page 47) should always be bright
and untarnished. If it is tarnished or stained, the cathode should be cleaned.
You can use a clean lint-free cardboard or cloth. Rub the cathode very gently
side to side 4-5 times. This will be enough to polish and remove any stains
without damaging the platinum tip. Afterwards, rinse the probe with deionized
or distilled water and install a new membrane cap using fresh electrolyte and
follow DO Probe Preparation page 46.
Important
In order to have accurate and stable measurements, it is important that the
membrane surface is in perfect condition. This semipermeable membrane
isolates the sensor elements from the environment but allows oxygen to
enter. If any dirt is observed on the membrane, rinse carefully with distilled or
deionized water. If imperfections still exist, or any damage is evident (such as
wrinkles or tears-holes), the membrane should be replaced. Make sure that the
O-Ring sits properly in the membrane cap.
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