The working principle of the oxygen sensor is similar to that of dry batteries, and the oxide element in the sensor acts similarly to an electrolyte. The basic working principle is this: under certain conditions (high temperature and platinum catalysis), a potential difference is generated based on the oxygen concentration difference between the inside and outside of the oxide. The larger the concentration difference, the greater the potential difference.
The oxygen content in the atmosphere is 21%. After the combustion of fuel gas, the exhaust gas does not contain oxygen, resulting in a much lower oxygen concentration. Under the catalytic action of high temperature and platinum, negative oxygen ions are adsorbed on the inside and outside surfaces of the oxide sleeve. Since the oxygen concentration in the atmosphere is higher than that in the exhaust gas, there are more negative ions on the side of the sleeve facing the atmosphere, leading to greater adsorption compared to the side facing the exhaust gas.
When the oxygen concentration on the exhaust gas side of the sleeve is low, a high voltage (0.6 to 1V) is generated between the electrodes. This voltage signal indicates a lean mixture. Based on the voltage signal from the oxygen sensor, the computer adjusts the fuel-air mixture to approach the theoretical best air-fuel ratio of 14.7:1, either by enriching or diluting it.
Therefore, the oxygen sensor is a crucial sensor for electronic fuel measurement. Its characteristics are fully manifested only at high temperatures (typically around 300°C), where it can output voltage. At approximately 800°C, it exhibits the fastest reaction to mixed gas. However, this characteristic undergoes significant changes at low temperatures.