OX400 — Calibration Failure (Decision Tree)
Use when calibration doesn’t complete, won’t stabilize, or cannot reach span/zero.
Most common causes: wrong gas/concentration, insufficient flow, leaking cal manifold, probe fouling.
Decision Tree
1) Analyzer stable before calibration?
If unstable → fix unstable reading first (probe/purge/leaks).
If unstable → fix unstable reading first (probe/purge/leaks).
2) Gas correct?
Confirm cylinder label, concentration, regulator type, correct connection point.
Confirm cylinder label, concentration, regulator type, correct connection point.
3) Gas flow adequate?
Confirm flow reaches probe (no blocked tube, no kinked line, regulator not closed).
Confirm flow reaches probe (no blocked tube, no kinked line, regulator not closed).
4) Leak test calibration path
Leak test fittings/valves/manifold. Air ingress causes failure and wrong spans.
Leak test fittings/valves/manifold. Air ingress causes failure and wrong spans.
5) Probe fouling
Clean/inspect probe tip and protective cap. Heavy fouling prevents stable calibration.
Clean/inspect probe tip and protective cap. Heavy fouling prevents stable calibration.
6) Stabilization time
Allow enough time after switching gas. Avoid calibrating during process swings.
Allow enough time after switching gas. Avoid calibrating during process swings.
7) Still failing?
Check diagnostics for sensor health, wiring faults, or configuration mismatch. Escalate.
Check diagnostics for sensor health, wiring faults, or configuration mismatch. Escalate.
Quick Checks
- Correct standard gas and regulator
- Gas flowing to probe (confirm physically)
- No leak in cal line/manifold
- Probe tip not fouled/plugged