Working Principle
In the documented ZR22G detector / ZR402G converter system, the zirconia cell operates at 750 °C. Its voltage depends on the logarithm of the oxygen partial-pressure ratio between reference air and sample gas (the Nernst relationship). The converter calculates oxygen concentration from this voltage.
Main Components
- Zirconia sensor cell
- Heater assembly
- Reference air system
- In-situ probe assembly
- ZR transmitter / converter
- Signal and heater cabling
Calibration — ZR22G / ZR402G
The manual describes a low-oxygen “zero” gas (typically about 1% O₂ in nitrogen) and an air “span” gas (about 21% O₂). Enter the actual gas concentrations and follow the applicable flow, stabilization and calibration sequence in chapter 9.
Reference air serves the reference side of the cell; calibration gas is introduced to the measurement side. They have different functions. Nitrogen alone is not the generic zero-gas instruction for this system.
Major Troubleshooting Areas
- High drift: sensor aging, contamination, unstable reference air
- Calibration failure: incorrect gas, leaks, poor flow
- Heater alarms: heater burnout, wiring faults
- Cell voltage: interpret with measured oxygen, temperature and the chapter 12 diagnostics; voltage alone does not establish a failed cell.
- Signal noise: grounding or shielding issues
Quick Navigation
Technical references
Updated against manufacturer documentation. Match the document to the installed model and options.
- Yokogawa: ZR22G / ZR402G Separate type Zirconia Oxygen/Humidity Analyzer — IM 11M12A01-02E, 18th edition, 27 December 2022; chapters 7, 9, 11–12.