H36.0.01.6C-13
Operating Manual GMH 3610
page 7 of 12
7 The Oxygen Electrode
7.1
Electrode design
7.2
Electrode Maintenance
If electrode can no longer be calibrated, it needs maintenance.
Attention! The electrolyte is a corrosive.
To maintain electrode please proceed as follows:
1. Unscrew diaphragm head and wipe clean of electrolyte solution using a paper cloth. Do not touch electrolyte If
your skin had contact with electrolyte, immediately rinse thoroughly with clear water.
2. Clean silver cathode with sand paper (grain size 240). Do not polish silver cathode, surface should stay rough.
Remove all dust.
3. Remove filling screw and top up lost electrolyte (e.g. using disposable syringe))
4. Put back and tighten filling screw.
5. Top up diaphragm head with electrolyte avoiding air bubbles and place on table (cover table with absorbent
paper first).
6. Keep electrode in a vertical position and screw diaphragm head to the electrode from the bottom. Electrolyte
will be forced out of the diaphragm head and spill over (put on disposable gloves or use paper towel to touch
diaphragm head).
7. Wipe up excess electrolyte with paper cloth.
8. Check cathode for air bubbles.
If there are large air bubbles, remove diaphragm head again and repeat process as of point 5. If O-ring has
been damaged, it has to be replaced.
When maintenance has been completed plug on protective flask. Re-connect electrode to measuring device and
wait for at least 3 hours till electrode can be calibrated.
The oxygen electrode is an active electrode consisting of a silver cathode and a
lead anode with the electrolyte being potassium hydroxide (KOH). In case of oxy-
gen being present it will be reduced at the silver cathode, i.e. the electrode sup-
plies a current. No oxygen means no current either. The oxygen measurements
use up both the silver cathode as well as the lead anode. The electrode is subject
to ageing. Therefore, we recommend to maintain the electrode at monthly intervals
(p.r.t. 'Electrode maintenance')
Please note: Make it a rule to always store the electrode in a humid
environment.
- in the storage flask filled with water
- in another container filled with water
If electrode has not been used for some time, clean diaphragm with
soft cloth and remove deposits, if any (algae, bacteria etc.).
Aufbau der Elektrode
The electrode housing is made of PVC. With the exception of the electrode shaft
all parts need to be maintained regularly and be replaced if necessary.
o Protective flask
: The protective flask is used to moisten the diaphragm. The
prolongs service life of the electrode. The protective flask contains water. At-
tention! Use water only; never use potassium chloride (KCI); this is only re-
quired for storage of pH-electrode.
o Diaphragm head
: the diaphragm head is covered with a teflon diaphragm. It
will be filled with KOH electrolyte and screwed onto the electrode shaft (no
air bubbles). Damages in the diaphragm, large air bubbles or air bubble rings
in the diaphragm head will result in erroneous measurements. This may also
be the reason for errors in the calibration. The diaphragm head is a spare
part and can be ordered individually.
o Filling hole
: If the electrode is used at high temperatures or if it has been
stored without its protective flask for a longer period of time, some electrolyte
will be lost due to evaporation. During maintenance make it a rule to unscrew
diaphragm head, remove locking screws and top up electrolyte using a sy-
ringe. Replace and tighten locking screws.
Attention when working with electrolyte! The electrolyte is cor-
rosive! (strong base, KOH)
Filling hole
Electrode shank
O-ring
Diaphragm cap