Abstract: An oxygen sensor (1) for detecting the oxygen content of an internal combustion engine exhaust gas system includes a generally cylindrical hollow insulator (3) having a first resistive element (17), preferably of titania, and a second resistive element (19) preferably of zirconia or chromia, adjacent the closed end (9) thereof, grooves (23) adjacent the open end (7) thereof, and an intermediate portion (11) having a shoulder (13), with electrically conductive film leads (29) passing over the surface of the insulator (3) between the resistive elements (17 and 19) and the grooves (23), with a dielectric coating (33) over the conductive film leads (29) in the area of a metal shell (31) to insulate the film leads (29) from the shell (31).

Abstract: A zirconia type oxygen partial pressure sensor for use with an exhaust system wherein an electrical voltage signal is generated in response to an oxygen partial pressure differential across a solid electrolyte. A reference oxygen partial pressure is introduced into the interior of a solid electrolyte sensor through an aperture formed in a housing for the sensor, a protective clip, wire mesh or spring being provided to at least partially cover the aperture to preclude contaminants from being introduced to the interior of the sensor through the aperture. A ground terminal assembly is also provided to supply a ground for the device in addition to that provided by the threaded engagement between the shell of the O.sub.2 sensor and the exhaust system to which it is attached.