Solid electrolyte oxygen sensor - having metal oxide mix in electrolyte cup with heat resistant stopper and seal

摘要

Oxygen sensor element consists of a solid electrolyte vessel with a metallic pole on its inner reference surface. It has a second metallic pole on its outer test surface. The vessel or cup is filled to a specified level with a metal/metal oxide mixture which serves as a reference source of O2. The cup is sealed by a stopper which contacts the mixture. A heat resistant sealing medium is used to seal the stopper in. The vessel is cup shaped with a closed end. The stopper can be threaded or smooth and should be made of the same material as the solid electrolyte. If not, it should have the same coefficient of expansion as the solid electrolyte. The seal can be a glassy material. This can be applied as a soln. to the stopper. Used esp. for monitoring exhaust gas streams from i.e. engines before passing them to catalyst beds for cleaning up. It is necessary to seal such a cell because if exhaust gas gets inside, it affects the O2 potential of the reference mixture and upsets the calibration. The use of all glass seals is known but these give poor thermal shock resistance. The seal with the stopper is operationally safer and more reliable.