Problem Probable cause Resolution
The measurement is
not accurate.
The permeability of the
membrane has changed (dirt
deposits).
Calibrate the sensor. Identify if the concentration
measurement is back to normal.
There is contamination in the
electrolyte.
Examine the screw-in parts (membrane, filling
screw, filling washer). Replace the electrolyte and
membrane.
There is an electrolyte leak.
Examine the screw-in parts (membrane, filling
screw, filling washer). Replace the electrolyte and
membrane.
There are interferences with the
measurement (primarily with
H
2
S).
If the level of H
2
S (or other contaminate) is stable,
adjust the dissolved oxygen measurement by the
concentration of the contaminate.
An error occurred during
calibration or the calibration is
incorrect.
Calibrate the sensor again to examine the
parameters. If the error continues, examine the
calibration current (too high, too low or unstable) and
the concentration in air. Refer to the previous
problems in this table.
There are air bubbles near the
cathode.
Refill with electrolyte. Make sure that there are no air
bubbles at the bottom of the sensor body.
The sample flow rate too low
(4 mL/h minimum).
Increase the sample flow rate.
The sample temperature or
sample pressure is not within the
instrument specifications.
Change the sensor location or adjust the sample so
that it is within specifications.
There is sludge or particles on
the cathode.
Clean the cathode with a soft and absorbent tissue.
Replace the membrane.
The sensor current is
0 mA during
measurement.
There is no electrolyte in the
sensor (leak).
Examine the screw-in parts (membrane, filling
screw, filling washer). Replace the electrolyte.
The sensor cable is disconnected
or not fully connected.
Examine the sensor cable connections at the
module in the controller and at the sensor.
The sensor current is
negative.
There is a connection problem to
the anode circuit (loose contact).
Examine the sensor cable connections at the
module in the controller and at the sensor.
There is a dark green deposit of
silver bromide (AgBr) on the
surface of the silver anode of the
electrode.
Do the steps in Replace the membrane on page 21
and Clean the electrode on page 22.
The sample
temperature is not
within specification.
There may be a short-circuit on
the temperature connection.
Examine the sensor cable connections at the
module in the controller and at the sensor.
The measurement
shown on the display
is not numeric.
The measured value is less than
0 ppb if negative signs are
displayed.
Do a zero calibration.
The measured value is more than
10,000 ppb.
Replace the controller.
The sensor is in standby mode,
because the measured value is >
2 ppm.
Do the steps in Exit standby mode on page 16.
English 25
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