42
Maintenance and Troubleshooting
6.2.2 Measurement troubleshooting
6.2.3 O
2
zero calibration troubleshooting
6.2.4 High level calibration troubleshooting
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 3100 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 as described in Maintenance
schedule on page 39
Channel out
Change LDO spot
Contact Hach service
Silver bead does not move freely in the sample
Perform the monthly cleaning procedure as described in Maintenance
schedule on page 39
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 3100. 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
Symptom Possible solution
Signal not in range - calibration value very
different from last calibration value
Check your theoretical sample O
2
content and reference configuration
If gas bottle calibration, completely open the sample flow adjustment valve
to avoid gas overpressure in 3100, hence wrong O
2
concentration
Stability not reached - signal not stable
Wait for stability and check reference gas or liquid 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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