Principle Of Oxygen Sensor

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The oxygen sensor is a standard configuration on the automobile. It is a measuring element that measures the oxygen potential in the automobile exhaust pipe with ceramic sensitive elements, calculates the corresponding oxygen concentration based on the principle of chemical equilibrium, and achieves the monitoring and control of the air-fuel ratio of combustion to ensure the product quality and tail gas emission standards. Oxygen sensor is widely used in all kinds of coal combustion, oil combustion, gas combustion and other furnace atmosphere control, it is the best combustion atmosphere measurement method, has the advantages of simple structure, rapid response, easy maintenance, easy to use, accurate measurement and so on. Using the sensor to measure and control the combustion atmosphere can not only stabilize and improve the product quality, but also shorten the production cycle and save energy.

 

 

The oxygen sensor on the car works like a dry battery, with zirconia acting as an electrolyte. Its basic working principle is: under certain conditions, the potential difference is generated by the difference of oxygen concentration on the inside and outside sides of zirconia, and the greater the concentration difference is, the greater the potential difference is. The oxygen content in the atmosphere is 21%. The exhaust gas after the combustion of the thick mixture contains virtually no oxygen. The exhaust gas generated by the combustion of the thin mixture or the exhaust gas generated by the lack of fire contains more oxygen, but it is still much less than the oxygen in the atmosphere. Under high temperature and platinum catalysis, the negatively charged oxygen ions adsorbed on the inner and outer surfaces of the zirconia casing. Because there is more oxygen in the atmosphere than in the exhaust gas, more negative ions are absorbed on the side of the casing that is connected with the atmosphere than on the side of the exhaust gas, and the difference in the concentration of ions on both sides generates an electromotive force.

When the oxygen concentration on the exhaust side of the automobile casing is low, a high voltage (0.6 ~ 1V) is generated between the oxygen sensor electrodes. This voltage signal is sent to the automobile ECU for amplification. The ECU considers the high voltage signal as a concentrated mixture, while the low voltage signal as a dilute mixture. Based on the voltage signal of the oxygen sensor, the computer diluted or enriched the mixture according to the theoretical optimum air-fuel ratio as close as possible to 14.7:1. Therefore, oxygen sensor is the key sensor for electronic control of fuel metering. Only when the oxygen sensor is at high temperature (the end reaches more than 300°C) can its characteristics be fully reflected and the voltage can be output. It is most responsive to changes in the mixture at about 800°C, and this property can vary greatly at low temperatures.

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