Oxygen sensors are devices that are used to measure the amount of oxygen in the gas or liquid being tested. They are primarily used in cars. These sensors are fitted in the exhaust of the car and measure the oxygen content in the exhaust gas emitted from the car. They have also found use in diving equipment. This version is used by divers to measure the pressure of oxygen in their breathing gas mixture. Similarly, they have found their uses in several medical equipment such as oxygen analyzers, anesthesia monitors, and respirators.
The oxygen sensors that are being used in cars all over the world today owe their origins to Robert Bosch GmbH in the late 1960s. The first ones were developed under the supervision of Dr. Gunter Bauman, in Robert Bosch GmbH.
Originally, the equipment element consisted of thimble shaped zirconia ceramic, which was coated on the exhaust pipe, with a thin layer of platinum. This element would take quite some time to heat and relay its information to the car's engine management computer, which would base the amount of fuel and air mixture in the car.
These sensors are also known as Lambda Sensors. These sensors created an era where it became possible to measure the emissions from cars and monitor them. The first Lambda sensors were used in 1976 by Volvo and Saab. These sensors then began to be used in the USA from 1980 and in Europe from 1993.
Robert Bosch GmbH then modified the equipment and came out with a planar style sensor which hit the market in 1998. This new sensor reduced the mass of ceramic being used and also incorporated a heater within the structure. This created a sensor which responded faster and began its operations sooner.
Role of Oxygen Sensors
Most cars are equipped with an engine management computer (ECU), which uses look-up tables to determine the air-fuel ratio required to burn the fuel in a engine, for a complete combustion process. The ideal ratio is 14.7:1 for air and fuel. The ECU tries to find a way to maintain this optimum ratio and the oxygen sensor helps ECU do this.
The oxygen sensor can sense if the exhaust gas is rich with unburnt fuel vapor or if it is lean with excess oxygen. A rich mixture leads to an increase in the power of the car, but it decreases the car's fuel economy and increases the emission of hydrocarbons in the air. It can also overheat the catalytic converter. A lean mixture may often increase the fuel efficiency of the car, but it increases the emission of nitrogen oxide and eventually leads to engine damage.
The unburnt fuel is actually a mixture of hydrocarbons which are a result of more fuel in the air-fuel mixture. The nitrogen oxide is a result of increase in the air in the air-fuel mixture. Both of these add to the environmental pollution levels, causing smog and acid rain.
The ECU uses a closed loop feedback mechanism, which varies the fuel injector output according to real-time data received from the sensor. This helps in increasing the efficiency of engine operation, while reducing the amounts of unburnt fuel and nitrogen oxide that enter the atmosphere.
These oxygen sensors have a limited life. They last for anywhere between 30,000 to 50,000 miles in an unheated condition, and for about 100,000 miles in a heated condition. It can fail due to the accumulation of soot on the ceramic element of the sensor. These sensors also fail due to the use of leaded fuels or due to contamination of the fuel with silicones and silicates. This can damage the catalytic converter.
An oxygen sensor, thus, performs a very important function in the operation and the overall performance of the car. It also performs a very important function of maintaining emission levels from the exhaust gases that are emitted from the car, thus helping in reducing environmental pollution caused due to cars.