3. Remove the holding screw from the flow chamber assembly.
4. Holding the assembly between thumb and forefinger, gently ease it out of the instrument and
discard.
5. Replace the assembly with the new one from the maintenance kit, Put the new assembly back in
place in the instrument and secure with the holding screw. A guide rod is in place to ensure
correct positioning.
6. Replace the front guard and secure in place with the 2 screws underneath the instrument.
7. After changing the spot, a sensor calibration must be performed before using the instrument for
measurement purposes.
Troubleshooting
Measurement
Symptom Possible solution
Display appears to be frozen - no
active cursor
Check measurement mode (continuous or sample)
Display appears to be frozen out
of range
When “Out of Range”, measurement interval is 60 seconds
Degassing in flow meter Adjust flow rate to between 150 and 200 mL/min
Verify that the filter (if using) is not blocked
Measurement spiking Ensure all tubing is tightly and correctly connected to the sample inlet and
outlet connections
Remove any residual air bubbles from the sample line by turning the sample
inlet/outlet valve to the PURGE position for 5 seconds
Response time too long Use tubes supplied with instrument (low O
2
permeable material)
Check flow rate and connections
Prior to package sampling, purge the piercer with N
2
gas
Perform the monthly cleaning procedure
Channel out Change LDO spot
Contact Hach Lange service
Silver bead does not move freely
in the sample
Perform the monthly cleaning procedure
Zero calibration
Symptom Possible solution
Signal not in range - calibration
value very different from last
calibration value
Open sample flow adjustment valve completely
Calibration gas has too much oxygen, use quality 50 N
2
or CO
2
bottle
Oxygen leaks between reference bottle and instrument. Can be checked by
increasing gas flow rate and checking partial pressure (mbar) decrease
Stability not reached - signal not
stable
Wait for stability and check N
2
gas flow rate
Presence of liquid on LDO membrane. Check presence of liquid in flow
meter and if so, dry by injecting 20 mL of EtOH then 5 minutes of N
2
gas
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