Oxygen sensor for detecting the oxygen content of an internal combustion engine exhaust gas system

An oxygen sensor for detecting the oxygen content of the gaseous atmosphere in an internal combustion engine exhaust gas system, having a first resistive element having an electrical resistance characteristic that varies as a function of both temperature and the presence of oxygen in said gaseous atmosphere to which the element is exposed, and a second resistive element having an electrical resistance characteristic that varies as a function of the temperature of said gaseous atmosphere to which the element is exposed in a manner similar to that of the first resistive element, and either varies negatively or does not vary as a function of the oxygen in said gaseous atmosphere, comprising:

• a generally cylindrical hollow electrical insulator having an open end, a closed end, and an intermediate portion;
• said first and second resistive elements being situated on the outer surface of the insulator adjacent the closed end;
• a plurality of grooves in the outer surface of the insulator adjacent to and communicating with the open end;
• a shoulder formed about the insulator at the intermediate portion thereof;
• electrically conductive film means extending from said first and second resistive elements and over the surface of the intermediate portion to said grooves;
• a threaded metal shell enclosing the intermediate portion of the insulator;
• and
• a dielectric coating over said film means in the area of the metal shell to insulate the film means from the shell.