A car is a complex system with many components, each of which performs a different function. One of these is an oxygen sensor, also known as a lambda probe.
Oxygen sensor design
An oxygen sensor or lambda probe (from the Greek letter λ, which denotes a mixture of gasoline and air) is a special component of a car engine for assessing the amount of free oxygen remaining in the exhaust gases. According to the principle of operation, the device is a galvanic cell with a solid ceramic electrolyte made of zirconium dioxide. Conductive platinum electrodes are deposited on top of the ceramics doped with yttrium oxide. Exhaust gases enter one of the electrodes, and air from the atmosphere enters the other. During operation, the lambda probe heats up to 300-400 degrees, which makes it possible to measure the residual oxygen. At this temperature, the zirconium electrolyte becomes conductive, and the difference in the amount of oxygen in the exhaust gas and atmospheric oxygen results in an output voltage at the electrodes.
If the oxygen concentration is the same on both sides, the electrolyte sensor is in equilibrium and its potential difference is zero. When the oxygen concentration changes on one of the electrodes, a potential difference arises, which is proportional to the logarithm of the oxygen concentration on the working side of the sensor. As soon as the combustible mixture reaches stoichiometric composition, the oxygen content in the exhaust gases decreases hundreds of thousands of times, leading to an abrupt change in the sensor, which is detected by a high-resistance measuring device (on-board computer of a car).
Oxygen sensor function
The oxygen sensor is not an independent device. It operates with the participation of an exhaust gas catalytic converter designed to oxidize toxic substances (hydrocarbons, nitrogen oxide and carbon monoxide) to carbon dioxide, water and nitrogen in a catalytic reaction. The catalyst becomes effective (with neutralization of up to 80% of the components) in a rather narrow range: at λ from 0.85 to 0.9, the maximum power of the system is provided, and at λ from 1.1 to 1.3 (the throttle valve of the gasoline engine is fully open) the highest fuel economy is achieved. A special power supply system with discrete (electronic) fuel injection, as well as the oxygen sensor itself, are involved in achieving the exact indicators necessary for the efficient operation of the internal combustion engine. Control over fuel consumption and oxygen content in it allows you to avoid various malfunctions in the operation of all engine systems.
