Hach ORBISPHERE Series Basic User Manual page 21

Problem
Unexpected or inaccurate
dissolved O readings.
2
Calibration is out of specification
or response time is too slow.
Probable cause
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
Set flow rate to 100 mL/min. Wait until stable, then
slowly double the flow rate.
The stable value of dissolved O
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 Sensor membrane specifications
on page 4).
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 must be
2
English 21