Which sensors use galvanic cells or Clarke electrodes to measure oxygen partial pressure?

• A. Electrochemical sensors
• B. Capacitance sensors
• C. Thermocouple sensors
• D. Optical sensors

Answer: (A)

Oxygen partial pressure is measured with electrochemical sensors, which include galvanic cells and Clarke electrodes. In these sensors, oxygen undergoes a redox reaction at electrodes, producing an electrical signal that is proportional to the amount of O2 present. A galvanic cell sensor contains a suitable redox couple and a diffusion pathway; oxygen diffuses in and is reduced at the cathode, generating a current without needing an external power source. The Clarke electrode works similarly: oxygen diffuses through a membrane to the cathode where it is reduced, and the resulting current reflects the pO2. This approach is distinct from capacitance sensors (which detect dielectric changes), thermocouples (which measure temperature via the Seebeck effect), and optical sensors (which rely on light-based signals like luminescence or absorption).