EIJKELKAMP 18.50.01 Bedienungsanleitung Seite 137

• An upper part consisting of an anode, a cathode, and cable.
• A lower part consisting of a membrane cap, membrane, and electrolyte solution.
Oxygen diffuses through the membrane onto the cathode, where it is consumed. This process
produces an electrical current which flows through the cable to the meter. The electric current
produced is proportional to the oxygen that passes through the membrane and the layer of electrolyte.
This makes it possible to measure the partial pressure of oxygen in the sample at a given temperature.
Since the DO in the sample is consumed by the cathode it is essential that a new sample must flow
past the membrane of the probe to prevent the occurrence of false readings. The probe uses very little
oxygen for its measurement. This enables it to function correctly with liquid movement as low as 2.5
cm/sec. The permeability of the membrane to oxygen varies greatly with temperature. Therefore
compensation is needed for this variation. The DO probe comes with an inbuilt Temperature
Compensation for the membrane variation.
Probe Care
Under typical operating conditions, the probe should last for several years. Proper care and
maintenance will help you receive the maximum probe life and ensure more accurate readings. Since
any deposits on the membrane surface act as a barrier to oxygen diffusing through the membrane, the
membrane must be cleaned at regular intervals to assure maximum reliability. After using the probe,
rinse the probe in clean water and wipe it with a soft cloth or paper to avoid any hardening of deposits.
If growth develops on the probe, use a disinfecting chemical to clean.
NOTE: Although the membrane is strong and not easily damaged, wipe it gently while cleaning it. If
the membrane is damaged or torn, the probe will no longer function.
There are no special probe storage requirements.
Membrane Housing Replacement
Replacement of the membrane cap housing/ membrane is required only when you cannot calibrate the
probe, or if the membrane is damaged. Typical membrane damages are punctures or wrinkles caused
during measurements or cleaning. Your new DO probe comes with replacement membrane housing.
To order more replacement membrane housing, see the "Accessories" section page.
To replace the membrane cap (with pre-installed membrane)
1. Replacement is much easier with single membrane housing. Unscrew the old
membrane cap housing.
2. Hold the probe under hot running water and brush away the white oxide on the
cylindrical anode with a stiff plastic brush – do not use metal cleaning material.
3. If the cathode has any deposits, remove them with a light scouring powder. Do
not polish the cathode.
4. Fill the new membrane cap housing with electrolyte solution and inspect the
bottom for leaks. If the solution drops are leaking from the membrane, use new
cap housing.
5. If the assembly is leak-free, fill the membrane cap housing with electrolyte to the
brim.
6. Tap the side of the housing gently to remove any air bubble that may be sticking
to the membrane.
7. Screw the cap onto the probe. Excess electrolyte will drain out.
8. Replace probe guard.
9. Calibrate the probe after the % saturation readings have stabilised.
Membrane/O-ring Replacement (Optional Procedure)
It is recommended only experienced service personnel can perform this procedure.
This proced ure is OPTIONAL, and should only be performed if you have new
membrane and O-ring. You are also required to have a membrane installation tool. These items are
available as optional accessories in the "Accessories" section.
Pull off the probe guard.
1. Unscrew the membrane cap from the probe.
2. Hold the probe under hot running water and brush aw ay the white oxide on the cylindrical anode
with a stiff plastic brush – do not use metal cleaning material.
3. If the cathode has any deposits, remove them with a light scouring powder. Do not polish the
cathode.
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