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Charger and Discharger Problems

This section details issues related to the corona chargers and dischargers.

Fluctuating Current

Symptom: The standard deviation of the charger or discharger current exceeds 5 nA.

Cause: Corona discharge is an inherently unstable process. The instrument's electronics continuously adjust the charger voltage to maintain a stable current. Over time, the corona needle can become contaminated with dust, making it difficult to maintain a constant current. This leads to fluctuations. In severe cases, the charger may "flicker," being completely off for periods and then periodically switching on for short bursts at a high frequency (roughly 10 Hz).

Solution: Clean the affected charger or discharger.

Low Current / Control at Maximum / Charger Disabled

Symptoms:

  • The charger current control signal is at its maximum, but the measured current remains too low.
  • The software log displays a "Charger disabled due to overload danger" warning.

Cause: These symptoms indicate that the instrument cannot produce sufficient charger current. This can happen when the corona needle is dirty or damaged. The "overload danger" warning occurs when the control voltage remains at maximum for several seconds without achieving the target current. To prevent damage, the instrument automatically disables the charger for the remainder of the measurement cycle. The charger is reset at the start of the next cycle and will be disabled again if the problem persists.

Impact:

  • A faulty discharger affects all operating modes by preventing a correct measurement of the electrometer signal offset.
  • A faulty main charger affects the "particles" and "alternating" charging modes.

Solution:

  1. Ensure all cables in the sample preconditioning unit are securely and correctly connected.
  2. Inspect the charger needle to confirm it is intact and straight.
  3. Check for any foreign objects in the small gap between the post-filter electrode and the charger current electrode.
  4. If the problem continues, contact Airel Support for further instructions.

High Current / Control at Minimum

Symptom: The charger current control signal is at its minimum, but the measured current is still higher than the target value.

Solution:

  1. First, check the software log for "charger overload danger" warnings. If these are present, the actual issue is insufficient current, and you should follow the solution for the "Low Current / Control at Maximum" problem instead.
  2. Ensure all cables in the sample preconditioning unit are securely and correctly connected.
  3. Check for any foreign objects in the small gap between the post-filter electrode and the charger current electrode.