Alarm: No Oxygen Signal
Manufacturer: Yokogawa
Alarm Description
The No Oxygen Signal alarm indicates that the analyzer is not receiving a valid measurement signal from the zirconia sensor. The output may be fixed, zero, or marked invalid.
Typical Symptoms
- Oxygen value fixed at 0%, 21%, or last known value
- Sensor or signal error displayed
- Calibration cannot be performed
- Signal loss after shutdown or maintenance
Probable Causes (Most Common First)
- Heater not operating or analyzer not fully warmed up
- Reference air supply blocked or missing
- Zirconia sensor probe failure
- Signal cable or terminal wiring fault
- Converter electronics failure
Field Checks
- Verify heater operation and sensor temperature
- Check reference air flow and filters
- Inspect probe condition and contamination
- Measure sensor output at converter terminals
- Check wiring continuity between probe and converter
Corrective Actions
- Allow full warm-up or restore heater operation
- Restore reference air supply
- Replace zirconia probe if no output is present
- Repair or replace damaged signal wiring
- Replace converter electronics if required
Impact on Measurement
Without a valid oxygen signal, analyzer output must not be used for combustion control or emissions monitoring. Normal operation must be restored before relying on analyzer data.