Hach GA2X00 Manual Básico Del Usuario página 21

Problem
Shorter than expected
sensor operation in relatively
high dissolved O
2
concentration.
Unexpected or inaccurate
dissolved O readings.
2
Calibration is out of
specification or response
time is too slow.
Probable cause
High O
2
concentrations
generate deposits
more quickly.
Air leak on product
sample line.
High residual current.
Sensor incorrectly
setup.
Temperature
measurement
incorrect.
Barometric pressure
incorrect.
Cartridge incorrectly
assembled on sensor.
Sensor electrodes are
dirty.
Sensor maintenance is
required.
Possible solution
Install a less permeable membrane.
Turn off the analyzer when sensor is not in
a low O concentration.
2
Set flow rate to 100 mL/min. Wait until
stable, then slowly double the flow rate.
The stable value of dissolved O
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 and
wait for low reading.
Check concentration against low
measurement limit (refer to
membrane specifications
If concentration is significantly higher than
low limit, try replacing the membrane.
Check the sensor parameters on the
instrument.
Re-calibrate the sensor.
Control the temperature with an external
reference.
Re-calibrate the sensor.
Calibrate the barometric pressure sensor
using the instrument.
Re-calibrate the sensor.
Verify the cartridge assembly is firmly
screwed onto the sensor and that the
membrane is tight.
Re-calibrate the sensor.
Clean the sensor using the ORBISPHERE
32301 cleaning and regeneration center as
explained in this section.
Re-calibrate the sensor.
Replace the membrane by installing a new
sensor cartridge as explained in this
section.
Re-calibrate the sensor.
reading
2
Sensor
on page 4).
English 21