Hach ORBISPHERE 31 Série Manuel D'utilisation Simplifié page 15

1. Fill the sensor electrolyte reservoir with a
solution of 25% by weight ammonium
hydroxide (NH OH) in water and leave for
4
10 minutes.
2. Rinse with tap water for at least one minute.
3. Inspect the sensor head. The counter
electrode should be a silver-white color.
4. If the counter electrode still shows deposits,
repeat the procedure.
Ammonia is dangerous! Please refer to the safety information from your chemical supplier.
6.3.3 Anode and cathode nitric acid cleaning
Note: Only use nitric acid to clean very dirty sensors.
1. Check for the absence of silver deposit on
the central guard ring electrode walls, as
such deposits can make contact with the
counter electrode.
2. To eliminate any silver residue inside the
sensor cell, it is sometimes required to
repeat the chemical cleaning using nitric acid
(HNO , not over 70% by weight).
3
3. Also, the 32301 electrochemical cleaning
does not remove deposit on the cell's plastic
parts, so nitric acid cleaning may be
required.
Note: This procedure is not recommended for normal
maintenance, and should not be used more often than twice
a year, as the acid degrades the metal of the counter
electrode, thus reducing the sensor's life.
4. Place concentrated nitric acid into the sensor
electrolyte reservoir, and add 1 drop on the
center electrode.
5. Leave for no longer than 3 seconds.
6. Quickly empty the acid and rinse thoroughly
under tap water for one minute.
Nitric acid is dangerous! Please refer to the safety information from your chemical supplier.
C A U T I O N
C A U T I O N
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