Why this matters

Your ppm is only as good as your sensors. Calibrate fast, log results, and you’ll spend less time chasing “phantom” issues.

What you’re measuring

  • O₂ (ppm): galvanic cell output ∝ oxygen partial pressure. Cells age; expect drift.
  • Dew point (°C): chilled-mirror = best accuracy; polymer probes = cheaper, drift faster.
Image credit: Peter Southwood, “Oxygen cells P4260436,” via Wikimedia Commons, CC BY-SA 4.0 (cropped & resized).

2-point calibration (use this every quarter)

For O₂ analyzers

  1. Zero with high-purity N₂/Ar (specified flow).
  2. Span on air (20.9% O₂) or certified span gas.
  3. Verify at the ppm range you operate (1–5 ppm). Sluggish? Plan a cell swap.

For dew point

  • Chilled mirror: clean mirror → verify control loop → compare to certificate/reference.
  • Polymer probe: cross-check vs chilled mirror or salt standard; apply offset only if repeatable.

Quick fixes: symptom → cause → action

  • O₂ stuck low or noisy → cell near end-of-life / poor flow → replace cell; check plumbing.
  • O₂ spikes after transfers → sloppy load-lock → run three vacuum cycles.
  • Dew point creeps up → solvents or saturated sieve → cover solvents; schedule regeneration.
  • Both trending up → leak / glove nick → do a pressure test; inspect O-rings & gloves.

Operating targets (set alarms)

  • O₂: ≤ 1–5 ppm (alarm 5–10 ppm)
  • Dew point: ≤ −40 °C
  • Overpressure: +3 to +8 mbar
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Older Glove Box Inert Gas Choice: Argon vs Nitrogen (Key Points)