Oxygen sensor

Abstract

An oxygen ion conductive solid-electrolyte plate (1) has first and second opposite surfaces. A plurality of negative electrodes (21b, 22b) and positive electrodes (21a, 22a) are formed on the first and second surfaces of the solid-electrolyte plate (1), respectively, and each of the plurality of negative electrodes (21b, 22b) is opposed to each of the plurality of positive electrodes (21a, 22a). A spacer (5 or 7) is hermetically secured to the first surface of the electrolyte plate (1) and at the same time surrounds each of the plurality of negative electrodes (21b, 22b). A sealing plate (3) is also hermetically secured to the spacer (5 or 7). A plurality of closed spaces (61, 62) are thus defined as spaces surrounded by the solid-electrolyte plate (1), spacer (5 or 7) and sealing plate (3). A plurality of windows (41, 42) are provided in the sealing plate. Each of the plurality of closed spaces (61, 62) embraces one negative electrode of the plurality of negative electrodes (21b, 22b) and one window of the plurality of windows (41, 42). Each of the plurality of closed spaces (61, 62) communicates with the external space through one of the plurality of windows (41, 42). Each of the plurality of windows (41, 42) allows oxygen molecules to diffusely flow from the environment into each of the plurality of closed spaces (61, 62) through each of the plurality of windows (41, 42).