How Does an Oxygen Sensor Work?

[SebastianDella]

For more information on how an oxygen sensor works, the details are as follows: 1. The working principle of an oxygen sensor is similar to that of a dry cell battery, with the zirconia element in the sensor acting like an electrolyte. Its basic working principle is: under certain conditions (high temperature and platinum catalysis), the difference in oxygen concentration on the inside and outside of the zirconia generates a potential difference, and the greater the concentration difference, the greater the potential difference. The oxygen content in the atmosphere is 21%. The exhaust gas from burning a rich air-fuel mixture contains virtually no oxygen, while the exhaust gas from burning a lean air-fuel mixture or due to misfire contains more oxygen, but still much less than that in the atmosphere. 2. Under high temperature and platinum catalysis, negatively charged oxygen ions adsorb on the inner and outer surfaces of the zirconia sleeve. Since there is more oxygen in the atmosphere than in the exhaust gas, the side of the sleeve exposed to the atmosphere adsorbs more negative ions than the exhaust side, creating an electromotive force due to the difference in ion concentration between the two sides. When the oxygen concentration on the exhaust side of the sleeve is low, a high voltage (0.6 to 1V) is generated between the electrodes. This voltage signal is sent to the ECU for amplification and processing. The ECU interprets a high voltage signal as a rich air-fuel mixture and a low voltage signal as a lean air-fuel mixture. Based on the oxygen sensor's voltage signal, the computer adjusts the air-fuel mixture to be as close as possible to the theoretically optimal ratio of 14.7:1 by diluting or enriching the mixture. Therefore, the oxygen sensor is a key sensor for electronic fuel metering. The oxygen sensor can only fully exhibit its characteristics and output voltage when it is at a high temperature (the tip reaches above 300°C). At around 800°C, it reacts most quickly to changes in the air-fuel mixture, while at low temperatures, this characteristic changes significantly.