OX400 — Unstable O₂ Reading (Decision Tree)
Use when O₂ fluctuates, spikes, or won’t stabilize.
Golden rule: Unstable O₂ is often due to probe fouling, leaky calibration path, or purge problems.
Decision Tree
1) Process stable?
Confirm combustion/process stable (draft, fuel/air, load changes). If process is unstable, O₂ will be unstable.
Confirm combustion/process stable (draft, fuel/air, load changes). If process is unstable, O₂ will be unstable.
2) Probe condition / filter
Inspect and clean/replace if dust/ash buildup. Plugging creates slow and unstable behavior.
Inspect and clean/replace if dust/ash buildup. Plugging creates slow and unstable behavior.
3) Purge air (if equipped)
Confirm purge air pressure/flow and purge valve operation. No purge → probe fouls quickly.
Confirm purge air pressure/flow and purge valve operation. No purge → probe fouls quickly.
4) Calibration manifold leak
A leaking cal valve/fitting can allow air ingress causing unstable O₂. Leak test cal line and isolate.
A leaking cal valve/fitting can allow air ingress causing unstable O₂. Leak test cal line and isolate.
5) Electronics / grounding
Check cable shielding, grounding, loose terminals, moisture ingress. Electrical noise can create fluctuations.
Check cable shielding, grounding, loose terminals, moisture ingress. Electrical noise can create fluctuations.
6) Still unstable?
Verify sensor health via diagnostics, compare with portable reading after stabilizing, then escalate.
Verify sensor health via diagnostics, compare with portable reading after stabilizing, then escalate.
Fast Checks
- Probe cap/filter condition
- Purge air pressure/flow
- Cal line valves/fittings leak test
- Grounding/shielding and terminal tightness