Principle Of Oxygen Sensor

Oxygen sensor is a standard configuration on automobiles. It uses ceramic sensitive components to measure the oxygen potential in the exhaust pipes of automobiles, calculates the corresponding oxygen concentration based on the principle of chemical equilibrium, and monitors and controls the combustion air-fuel ratio to ensure product quality and exhaust emissions meet standards. Oxygen sensors are widely used in various types of coal combustion, oil combustion, gas combustion and other furnace atmosphere control. It is currently the best combustion atmosphere measurement method, with advantages such as simple structure, fast response, easy maintenance, convenient use, and accurate measurement. The use of this sensor for combustion atmosphere measurement and control can not only stabilize and improve product quality, but also shorten production cycles and save energy.
The working principle of oxygen sensors in cars is similar to that of dry batteries, and the zirconia element in the sensor acts like an electrolyte. The basic working principle is to utilize the oxygen concentration difference between the inner and outer sides of zirconia under certain conditions to generate a potential difference, and the larger the concentration difference, the greater the potential difference. The oxygen content in the atmosphere is 21%, and the exhaust gas after combustion of a rich mixture actually does not contain oxygen. The exhaust gas generated after combustion of a lean mixture or due to misfire contains more oxygen, but still much less than the oxygen in the atmosphere. Under the catalysis of high temperature and platinum, negatively charged oxygen ions adsorb on the inner and outer surfaces of zirconia sleeves. Due to the fact that there is more oxygen in the atmosphere than in the exhaust gas, more negative ions are adsorbed on the side of the casing that is connected to the atmosphere than on the exhaust gas side, and the concentration difference between the ions on both sides generates an electromotive force.
When the oxygen concentration on the exhaust side of the car casing is low, a high voltage (0.6-1V) is generated between the oxygen sensor electrodes. This voltage signal is sent to the car ECU for amplification and processing. The ECU considers the high voltage signal as a rich mixture and the low voltage signal as a lean mixture. Based on the voltage signal of the oxygen sensor, the computer dilutes or enriches the mixture according to the theoretical optimal air-fuel ratio as close as possible to 14.7:1. Therefore, oxygen sensors are the key sensors for electronic control of fuel metering. Oxygen sensors can only fully reflect their characteristics and output voltage at high temperatures (with end temperatures above 300 ° C). It has the fastest response to changes in the mixture at around 800 ° C, and this characteristic undergoes significant changes at low temperatures.