Abstract: A gas sensor includes a pair of electrodes printed on an electrically insulating substrate, a sensitive layer deposited on tip portions of the electrodes and a part of the substrate adjacent to the tip portions and bridging the space between the electrodes at the tip portion, and a protective film deposited on the electrodes and a part of the substrate adjacent to the tip portion so that a part of each electrode covered with the sensitive layer is free of the protective film. The sensitive layer is formed by depositing titanium oxide by plasma spraying on the substrate, and then heat-treating the deposited titanium oxide, so as to provide a diffusion reactive layer between the sensitive layer and the substrate and to form fine grooves on the surface of the sensitive layer.

Abstract: Gas sensor which is constructed of an electrically insulating base, electrodes formed on said base, and a gas sensitive film formed on the surface of said base at a portion where it detects a gas to be sensed, e.g., an oxygen gas. The gas sensor of the present invention is characterized in that the gas sensitive film is a thermal-sprayed film which is made of an oxide having a perovskite structure. The thermal-sprayed film has its surface formed with fine cracks to have its effective surface area increased so that the response is speeded up. Moreover, the thermal spraying process is so effected during the formation of the oxide film that an impurity to adversely affect the reliability may be avoided from being mixed.The gas sensor may have said gas sensitive film coated with a ceramic material so that is performance may be further improved while protecting the gas sensitive film. Furthermore, it is also effective to add another sensor with the electrically insulating base being commonly used.

Abstract: A gas sensor is described which includes a layer of a sensitive material formed on an electric insulating substrate and spaced electrodes electrically connected to the layer. The layer is formed of a porous film of a uniform mixture which contains a p-type compound oxide semiconductor with a perovskite type of crystal structure as the major ingredient and one or more of vanadium, niobium, tantalum and/or compounds thereof as minor ingredients. The minor ingredients are contained in the layer in an amount of 0.01 to 5% by weight, based on the weight of the p-type compound oxide semiconductor, and are incorporated into the layer by diffusing them into the layer. The gas sensor exhibits a small change with time and a reduced tailing effect attendant on variations in the gas combustion. With this, it is possible to effect measurements, detection and control with a high reliability.

Abstract: A sensor having an n-type oxide semiconductor layer and a p-type oxide semiconductor layer spaced from and electrically connected in series with each other and two fixed resistors connected in series with each other, wherein the two semiconductor layers and two resistors are connected to construct a four-arm bridge.