And where´s the oxygen?

Biochemistry, medical, air-conditioning, plant growing in glass-houses, protection against fire or explosion,… these are only a few fields, where it´s usually necessary or at least desirable to know exact concentration of oxygen in air.

Oxygen ... one of the most important elements for life. But how to measure it? An old known method says about a burning candle and until it burns it´s OK… or in other words, the O2 concentration is above approx. 15%. Naturally this is a method usable only somewhere and only for a rough orientation. Fortunately, there also exist some more accurate components - oxygen sensors.

In our portfolio can be found the top level sensors series KE, as well as a novelty - SK25F, both from a pioneer in segment of sensors - Japan company Figaro. There are a few principles how to create an oxygen sensor and the method of a galvanic cell belongs to the most reliable ones. What is it about? The whole sensor is constructed as a miniature battery with an acid electrolyte and electrodes from gold and Lead. A solid oxygen permeable membrane enables access of a small amount of gases into a battery. That causes a chemical reaction at which Pb oxidizes to PbO while emitting electrons. This results into an essential fact, that this sensor doesn´t require any power supply - it behaves as a battery with an output voltage proportional to an oxygen concentration. An outstanding feature of this type of sensors is a high selectivity (virtually no sensitivity to other gases) and a high linearity. That´s why to calibrate a sensor, it´s usually sufficient to measure in two points (zero concentration and approx. 21% concentration at a common air). A disadvantage is, that a lifetime is limited by exhausting a Lead electrode and it is roughly several years.

KE25 is a bigger type with a long lifetime, with only one limitation - that it can´t be installed in an upside-down position. A novelty - type SK25F is very suitable for miniature devices usable in any position. Both types feature a built-in temperature compensation, so their usage is very straightforward. Details and useful tip for a successful usage can be found in the Figaro KE and Figaro SK25F technical guides.
KE25 and also SK25F are in our standard stock offer. Upon order we´re able to provide you also the KE50 type with even longer lifetime. In case of interest, please contact us at info@soselectronic.com.