Shielded, heated electrochemical gas sensor

Abstract

To extend temperature range of solid electrolyte ion conductive-type gas sensors, particularly for the exhaust gases from internal combustion engines, and to prevent leakage currents between a heater element and the solid electrolyte body at temperatures just above the response temperature of the sensor, but below its normal operating temperatures, that is, even in the range of between 250.degree. C. to 400.degree. C., a layer-like shielding electrode (18,29) is provided, positioned between the solid electrolyte body (11,25) and the insulating layer (17,31). The shielding electrode is galvanically connected to the return line (21,33) of the heating element. In accordance with one embodiment, the shielding electrode and one of the operating electrodes, for example, the sensing electrode (29), can be the same metallic film or element applied to the sensor, with an additional electrical insulation layer (32) interposed in the region between the film electrode (29) and the solid electrolyte body (25), the heater element (16,30) being positioned with the interposition of the electrical insulating layer over the film electrode in that region. Preferably, the width of the respective insulating layers decreases in a direction away from solid electrolyte body. The system is applicable both to potentiometric, as well as polarographic-type sensors, of, selectively, closed tubular or plate-like construction, with electrodes exposed either to a reference gas or having, respectively, different catalytic activity.

Dependencies are inferred from the claim text.