An amperometric electrochemical gas sensor holds a working electrode (WE), reference electrode (RE) and counter electrode (CE) in electrolyte behind a gas-permeable membrane. Target gas diffuses through the membrane and is oxidized at the catalytic WE surface:
CO + H₂O → CO₂ + 2H⁺ + 2e⁻
- Amperometric signal — the current produced by this reaction is linearly proportional to the gas concentration at the electrode surface: I = S·C + I₀.
- Response time — the electrode-surface concentration doesn't jump instantly when the ambient concentration changes; it lags the target through membrane diffusion, modeled here as a first-order exponential approach with time constant τ.
- Readout noise — the displayed reading adds small electronic noise on top of the true current, same as a real potentiostat circuit.
- Reset — starts a fresh calibration test: a new sensor unit with slightly different sensitivity/offset, concentration back to 0, history cleared.