Working Principle
The ZR22G operates on the zirconium dioxide (ZrO₂) solid electrolyte principle. When heated to approximately 700 °C, the zirconia sensor generates an EMF proportional to the difference in oxygen partial pressure between the process gas and the reference air.
This voltage is converted by the transmitter into oxygen concentration using the Nernst equation.
Main Components
- Zirconia sensor cell
- Heater assembly
- Reference air system
- In-situ probe assembly
- ZR transmitter / converter
- Signal and heater cabling
Calibration Procedure
- Ensure stable process conditions and normal sensor temperature
- Perform zero calibration using nitrogen or instrument air
- Apply span gas (typically 2–8% O₂)
- Allow readings to stabilize before accepting calibration
- Verify readings against expected values
Field tip:
Frequent calibration failures often indicate sensor aging,
blocked reference air, or heater degradation.
Major Troubleshooting Areas
- High drift: sensor aging, contamination, unstable reference air
- Calibration failure: incorrect gas, leaks, poor flow
- Heater alarms: heater burnout, wiring faults
- Low EMF: cracked sensor or process oxygen imbalance
- Signal noise: grounding or shielding issues