Oxygen sensor

An oxygen sensor is an electronic device that measures the proportion of oxygen in the gas being analyzed. The sensing element is usually made with a zirconium ceramic bulb coated on both sides with a thin layer of platinum and comes in both heated and unheated forms.

In most modern automobiles, these sensors are attached to the engines exhaust manifold to measure the oxygen in the exhaust to determine whether the mixture of air and gasoline going into the engine is rich (too much fuel) or lean (too little fuel). This information is sent to the ECU (Engine Control Unit) computer, which adjusts the mixture to give the engine the best possible fuel economy and lowest possible exhaust emissions. It was originally called a 'Lambda sensor' in early cars.

Failure of these sensors, either through normal aging or the use of leaded fuels, can lead to damage of an automobile's catalytic converter and expensive repairs.

A different type of oxygen sensor, which is sometimes called an oxygen analyser or ppO₂ meter, is used in SCUBA diving. They are used to measure the oxygen content of breathing gas mixes such as nitrox and trimix. They are also used within the oxygen control mechanisms of closed-circuit rebreathers to keep the partial pressure of oxygen within safe limits. This type of oxygen sensor measures the electricity generated by a small electro-galvanic fuel cell.

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