Measurement Problems
This section addresses issues observed in the measured size distributions and concentrations.
No Cluster Ions Visible
Symptom: The data does not show the presence of cluster ions (i.e., small ions).
Particle Loss Before Instrument Entry
Cause: Particles are lost in the inlet tubing. This can be due to an improperly grounded inlet or an excessively long inlet tube.
Solution: Ensure the instrument inlet is properly grounded and use the shortest possible inlet tube.
Particle Loss Inside Instrument
Cause: Particles are lost internally before reaching the mobility analyzer. This is often due to incorrect electrical connections in the sample preconditioning unit.
Solution:
- Verify that all plugs in the sample preconditioning unit are connected to the correct sockets.
- Confirm a solid electrical connection between the filter electrode and its corresponding socket.
- Check the electrical connections of other components (charger needle, charger current electrode, post-filter electrode, discharger needle, discharger current electrode). Note that most of these faults would also trigger other diagnostic warnings.
Incorrect Offset Measurement
Cause: The "offset" operating mode is not functioning correctly, leading to an incorrect offset value being subtracted from the "ions" or "particles" mode signal.
Solution: Investigate and resolve any issues with the offset measurement mode.
Missing 9V Central Electrode Voltage
Cause: The 9V supply to the central electrode may be missing.
Solution: Check the relevant cable connections. If the issue persists, contact Airel Support.
Significant Difference Between Positive and Negative Concentrations
Symptom: There is a large, unexpected difference between the measured positive and negative particle/ion concentrations.
Solution:
- Check the software for any diagnostic warnings.
- Verify that all airflow tubes are correctly and securely connected, especially the sheath flow tubes running from the sheath air filters to the top of the analyzer.