Hach-Lange ORBISPHERE 31xxx Basic User Manual - Manual (Page 15)

Note: Install the membrane support with the groove on the upper side. The membrane support is individually
machined and paired with the sensor. Therefore make sure that the correct membrane support is used on the
correct sensor.
2. Insert the prongs of the membrane support removal tool into the membrane support holes.
3. Tighten the membrane support finger tight.
C A U T I O N
Too much torque will damage the sensor electrodes.
4. 5. 6. 7.
4. Place the dish with the polishing cloth on a flat surface. Spread a little polishing powder onto the
cloth. Mix with a few drops of water to get a grey, milky liquid. Make sure to use the correct
polishing powder for your application.
Note: Use one polishing cloth per sensor model, to prevent a possible contamination through metal particle
transfer.
5. Holding the sensor vertically, and using a circular motion, polish the sensor face for at least
30 seconds, until the electrodes are clean and shiny. This step may need to be repeated several
times. Make sure to avoid skin contact with the polishing cloth; it should be kept free of dust and
grease.
6. Remove the membrane support with installation tool. Rinse the support and sensor cavity with a
strong jet of clean water. Use distilled water if the water quality is doubtful.
7. Carefully inspect that the tiny groove between the center electrode and the guard ring electrode is
totally clean and free of polishing residue. Clean only with a strong water spray. The edge of a
paper sheet can be used to remove sticking residue.
O
3
Sensor only: final center electrode cleaning
Once the O
3
sensor has been successfully cleaned and polished, a final nitric acid treatment should
be applied, as follows:
1. Place the sensor in a vertical position on its base.
2. Fill the electrolyte reservoir with a few drops of
water, just enough to cover the outer electrode. The
center electrode must be kept dry.
3. Place a drop of nitric acid on the center electrode,
covering only the electrode and guard ring. Avoid
spilling acid into the water. Wait less than a minute,
then rinse thoroughly under tap water.
C A U T I O N
Nitric acid is dangerous! Please refer to the safety information from your chemical supplier.
Hydrogen sensor cell cleaning
Conditions
The hydrogen analyzer works on the principle that hydrogen molecules, passing through the
membrane, generate an electric current at the platinum anode surface. For this to take place, an
extremely clean metal surface is essential. If any film, grease or other impurity covers the platinum
surface, the reaction is impeded and may even be stopped.
English 15