The working principle of the oxygen sensor on the car is similar to that of a dry battery, and the zirconia element in the sensor acts like an electrolyte. The basic working principle is: under certain conditions, the difference in oxygen concentration on both sides of zirconia is used to generate a potential difference, and the greater the difference in concentration, the greater the potential difference. The content of oxygen in the atmosphere is 21%. The exhaust gas after burning the rich gas mixture is practically free of oxygen. The exhaust gas generated after combustion of the lean gas mixture or the exhaust gas generated due to the lack of fire contains more oxygen, but it is still higher than that of the atmosphere. The oxygen is much less. Under high temperature and platinum catalysis, negatively charged oxygen ions are adsorbed on the inner and outer surfaces of the zirconia sleeve. Since the oxygen in the atmosphere is more than the oxygen in the exhaust gas, more negative ions are adsorbed on the side of the casing that communicates with the atmosphere than on the side of the exhaust gas. The concentration of ions on both sides generates an electromotive force.