Hach-Lange ORBISPHERE A1100 Family - Manual (Page 42)

40
Maintenance and Troubleshooting
5.2 Troubleshooting
Table 7 Troubleshooting
Problem Probable cause Possible solution
Sensor won't calibrate, even after
cleaning and/or membrane change.
Instrument internal barometric pressure
sensor needs calibration. Calibrate using a certified barometer. Do
not correct for sea level !
Wet membrane interface. Wipe dry with a tissue and recalibrate.
"H
2
S insensitivity" option enabled.
Disable from the menu on the
measuring instrument.
"0000" O
2
levels displayed.
Wrong reading scale "XXXX" selected
for display unit.
Change reading scale by selecting
"X.XXX, XX.XX or XXX.X" on the
instrument.
Shorter than expected sensor operation
in relatively high dissolved O
2
concentration.
High O
2
concentrations generate
deposits more quickly.
Install a less permeable membrane.
Turn off the analyzer when sensor is not
in a low O
2
concentration.
Unexpected or inaccurate dissolved O
2
readings.
Air leak on product sample line.
Set flow rate to 100 ml/min. Wait until
stable, then slowly double the flow rate.
The stable value of dissolved O
2
reading
must be the same as before. A variation
related to flow rate is a clear sign of an
air leak in the line.
High residual current.
Place sensor in de-aerated sample and
wait for low reading.
Check concentration against low
measurement limit (see tables in
Sensor
membrane specifications on page 11 ).
If concentration is significantly higher
than low limit, try replacing the
membrane.
Calibration is out of specification or
response time is too slow.
Sensor incorrectly setup.
Check the sensor parameters on the
instrument.
Recalibrate the sensor.
Temperature measurement incorrect.
Control the temperature with an external
reference.
Recalibrate the sensor.
Barometric pressure incorrect.
Calibrate the barometric pressure
sensor using the instrument.
Recalibrate the sensor.
Cartridge incorrectly assembled on
sensor.
Verify the cartridge assembly is firmly
screwed onto the sensor and that the
membrane is tight.
Recalibrate the sensor.
Sensor electrodes are dirty.
Clean the sensor using the
ORBISPHERE 32301 cleaning and
regeneration center as explained in this
section.
Recalibrate the sensor.
Sensor maintenance is required.
Replace the membrane by installing a
new sensor cartridge as explained in
this section.
Recalibrate the sensor.