Hach ORBISPHERE 31 Série Manuel D'utilisation Simplifié page 16

6.3.4 Sensor face polishing
1.
1. Once the sensor has been cleaned, the face of the center electrode must be polished together
with the membrane support.
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.
Too much torque will damage the sensor electrodes.
4.
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.
6.3.5 O Sensor only: final center electrode cleaning
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Once the O sensor has been successfully cleaned and polished, a final nitric acid treatment should
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be applied, as follows:
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2.
C A U T I O N
5.
3.
6. 7.