Oxygen Sensor - Hach ORBISPHERE 31 Serie Manual De Instrucciones

In addition, the chemical reaction that takes place on the chloridized silver cathode leads to loss of
performance after a certain operation time.
As a result, a sensor service must be carried out to restore its original performance.
Method
The procedure for cleaning the H
32301 Sensor Cleaning and Regeneration Center. This procedure is explained in detail in the
32301 Operator's Manual.
As an overview, H
electrochemical sensor cleaning consists of the following sequence of operations:
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• Dechloridization of the cathode: This process removes the chloride film from the silver cathode
surface (carried out by the ORBISPHERE 32301).
• Rechloridization of the cathode: A layer of silver chloride is grown on the cathode's surface
(carried out by the ORBISPHERE 32301).
• Activation of the platinum anode: The center anode surface is polished, and treated with nitric acid.
Troubleshooting

Oxygen sensor

Problem
Sensor won't calibrate, even after
thorough servicing.
"0000" O levels displayed.
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Shorter than expected sensor
operation in relatively high dissolved
O concentration.
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Unexpected or inaccurate dissolved
O readings.
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16 English
electrochemical sensor requires the use of the ORBISPHERE
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Probable cause
Repeated calibrations go beyond
"expected limits" of instrument.
Instrument internal barometric
pressure sensor needs calibration.
Wet membrane interface.
"H S insensitivity" option enabled.
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Wrong reading scale "XXXX"
selected for display unit.
High O concentrations generate
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deposits more quickly.
Air leak on product sample line.
High residual current.
Possible solution
MOCA 3600 only: Select membrane
from "Options/Membrane" menu.
Then, calibrate the sensor.
Calibrate internal barometer against
a certified barometer. Do not correct
for sea level !
Wipe dry with a tissue and re-
calibrate.
Disable on the measuring
instrument.
Change reading scale by selecting
"X.XXX, XX.XX or XXX.X".
Install a less permeable membrane.
Turn off the analyzer when sensor is
not in a low O concentration.
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Set flow rate to 100 mL/min. Wait
until stable, then slowly double this
flow rate.
The stable value of dissolved O
reading must be the same as
before. A variation related to flow
rate is a clear sign of an air leak in
the line.
Place sensor in de-aerated sample;
wait for low reading:
Check concentration against low
measurement limit (see tables in
Sensor membrane specifications
on page 3). If concentration is
significantly higher than low limit, try
a sensor service.
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