An oxygen sensor (or lambda sensor) is an electronic device that measures the proportion of oxygen (O2) in the gas or liquid being analysed. It was developed by the Robert Bosch GmbH company during the late 1960s under the supervision of Dr. Günter Bauman.
The original sensing element is made with a thimble-shaped zirconia ceramic coated on both the exhaust and reference sides with a thin layer of platinum and comes in both heated and unheated forms. The planar-style sensor entered the market in 1990, and significantly reduced the mass of the ceramic sensing element as well as incorporating the heater within the ceramic structure. This resulted in a sensor that started sooner and responded faster.
The most common application is to measure the exhaust gas concentration of oxygen for internal combustion engines in automobiles and other vehicles. Divers also use a similar device to measure the partial pressure of oxygen in their breathing gas. Scientists use oxygen sensors to measure respiration or production of oxygen and use a different approach.
Oxygen sensors are used in oxygen analyzers which find a lot of use in medical applications such as anesthesia monitors, respirators and oxygen concentrators.
Oxygen sensors are also used in hypoxic air fire prevention systems to monitor the oxygen concentration inside the protected volumes continuously. There are many ways of measuring oxygen, including technologies such as zirconia, electrochemical (also known as Galvanic), infrared, ultrasonic, and laser methods. Each method has its advantages and disadvantages.