Oxygen activity in gases and metal and salt melts - is measured by a ceramic solid electrolyte immersed in the fluid

The solid electrolyte is soldered by its one end to a metal probe tube containing a gaseous or powdery medium with a certain oxygen partial pressure and a reference electrode on a side of the solid electrolyte in the form of a crucible soldered by its edge to the tube. The solid electrolyte crucible is inserted into the probe tube up to a collar in it. A clearance for the solder is left between the two. The outer part inner edge is chamfered. The reference electrode is fastened to a metal plate sintered to the solid electrolyte, or pressed to it by an insulating, spring loaded rod or tube.