Oxygen concentration sensor measurement principle
Oxygen sensors are standard equipment in automobiles. They utilize ceramic sensing elements to measure the oxygen potential in the exhaust pipe and calculate the corresponding oxygen concentration based on chemical equilibrium principles. This allows for monitoring and controlling the air-fuel ratio during combustion, ensuring product quality and compliance with exhaust emission standards. Oxygen sensors are widely used in atmosphere control for various coal-fired, oil-fired, and gas-fired furnaces. They are currently the optimal method for measuring combustion atmosphere, offering advantages such as simple structure, rapid response, easy maintenance, convenient use, and accurate measurement. Using this sensor for combustion atmosphere measurement and control can stabilize and improve product quality, shorten production cycles, and save energy.
The working principle of an oxygen sensor in a car is similar to that of a dry cell battery, with the zirconium oxide element in the sensor acting like an electrolyte. Its basic working principle is: under certain conditions, the difference in oxygen concentration on the inside and outside of the zirconium oxide sleeve generates a potential difference, and the greater the concentration difference, the greater the potential difference. The oxygen content in the atmosphere is 21%. Exhaust gas from the combustion of a rich air-fuel mixture actually contains no oxygen, while exhaust gas from the combustion of a lean air-fuel mixture or due to misfire contains a relatively high amount of oxygen, but still much less than the oxygen in the atmosphere. Under high temperature and platinum catalysis, negatively charged oxygen ions are adsorbed on the inner and outer surfaces of the zirconium oxide sleeve. Because there is more oxygen in the atmosphere than in the exhaust gas, the side of the sleeve open to the atmosphere adsorbs more negative ions than the side open to the exhaust gas, and the concentration difference of the ions on both sides generates an electromotive force.
To achieve high exhaust purification efficiency and reduce the levels of carbon monoxide (CO), hydrocarbons (HC), and nitrogen oxides (NOx) in exhaust gases, fuel-injected vehicles must utilize a three-way catalytic converter. However, for the three-way catalytic converter to function effectively, the air-fuel ratio must be precisely controlled to maintain a close proximity to the stoichiometric air-fuel ratio. The catalytic converter is typically installed between the exhaust manifold and the muffler. An oxygen sensor has a characteristic where its output voltage changes abruptly near the stoichiometric air-fuel ratio. This characteristic is used to detect the oxygen concentration in the exhaust and feeds feedback to the computer to control the air-fuel ratio.
The ECU determines whether the air-fuel ratio is too low or too high based on the difference in induced electromotive force from the oxygen sensor, and accordingly controls the injection duration. However, if the oxygen sensor malfunctions and causes an abnormal induced electromotive force, the ECU cannot accurately control the air-fuel ratio. Therefore, the oxygen sensor can also compensate for errors in the air-fuel ratio caused by wear and tear on mechanical components and other parts of the electronic fuel injection system. It can be said to be the truly "intelligent" sensor in the electronic fuel injection system.
What are the applications of oxygen concentration sensors?
Oxygen sensors are widely used in industries such as petroleum, chemical, coal, metallurgy, papermaking, fire protection, municipal engineering, pharmaceuticals, automotive, and gas emission monitoring. After reading this article, you should have a more comprehensive understanding of oxygen concentration sensors! Whether in the automotive field or environmental monitoring, oxygen concentration sensors are playing an increasingly crucial role. Furthermore, with the rapid advancement of scientific research, the performance of oxygen concentration sensors is becoming increasingly sophisticated, stable, and mature.
