Modern environmental standards are very strict, and the standards for the composition of exhaust gases are clearly defined. That is why in modern automotive industry special devices are used. These are catalytic converters, under the influence of which the level of toxic substances in the exhaust is significantly reduced. Unfortunately, such devices work well only under certain conditions. It is for this that an oxygen sensor is needed. This small part performs very important functions.
What is an oxygen sensor?
The optimal composition of the fuel-air mixture is when about 14.7 parts of air falls on 1 part of the fuel. In this case, the excess air coefficient (L) is 1. Effective operation of the catalytic converter is possible only when L is 1 with an error of 0.01. The main function of the sensor is to monitor the composition of the fuel-air mixture.
The oxygen sensor is a small device made of a porous material. Its main component is zirconia. On top of the part is covered with platinum spraying. A similar device responds to the difference between the oxygen content in the atmosphere and exhaust gases. In addition, at the output, it produces the corresponding potential difference.
The principle of operation of this probe is quite simple. With a decrease in the level of oxygen in the exhaust, reactions of reduction of zirconium dioxide are triggered. By the way, the catalyst for this transformation is platinum. And since recovery reactions alternate with oxidative processes on the surface of the sensor, the integrity and operability of the probe are automatically maintained.
Today, there are several basic models of such devices. The most popular is the Bosch oxygen sensor. This device is characterized by high sensitivity and performance.
Two point oxygen sensor
This is one of the main models of such a device. The probe is mounted both in front of the converter and behind it, which makes it possible to more clearly fix the coefficient of excess air. The electrode on one side of the device is in contact with atmospheric air, and on the other, with exhaust gases, responding to the difference by generating potential. The higher the oxygen content in the exhaust, the lower the generated voltage.
In cases where the oxygen level in the fuel-air mixture drops and the voltage becomes high, an electrical signal is generated, which is transmitted to the engine control system.
Broadband Oxygen Sensor
This device is slightly different from the previous one both in structure and in operation. It consists of two ceramic parts: this is an ordinary two-point probe and the injection part. A voltage of 450 mV is constantly generated between the two electrodes in the two-point part of the probe. At the same time, oxygen from the exhaust gas passes through the pumping portion of the sensor. The lower the oxygen level, the higher the voltage between the two electrodes. In such cases, the signal is transmitted to the electronic control unit. By the way, it is precisely under this scheme that the VAZ oxygen sensor works.