Abstract: Disclosed is a device useful for detection of air/fuel ratio of an air-fuel mixture subjected to combustion in a combustor by sensing oxygen in the exhaust gas, using a solid electrolyte concentration cell type oxygen-sensitive element which requires supply of a DC current to flow through its solid electrolyte layer between reference and measurement electrode layers to establish a reference oxygen partial pressure at the interface between the reference electrode and the solid electrolyte. The device comprises a control circuit to vary the intensity of the current for the oxygen-sensitive element in dependence on the magnitude of output voltage of the oxygen-sensitive element at least when a predetermined one of said output voltage and a reference voltage is higher than the other in order to compensate variations of the magnitude of the reference oxygen partial pressure caused mainly by variations of the temperature.

Abstract: A device comprising an oxygen-sensitive element to be disposed in a combustion gas exhausted from a combustor to detect deviation of actual air/fuel ratio from a stoichiometric ratio. The element is a combination of two oxygen concentration cells each having a solid electrolyte layer, a measurement electrode layer formed on one side of the electrolyte layer, a reference electrode layer formed on the opposite side and covered with a shield layer. Either measurement electrode layers or reference electrode layers of the two cells are connected to each other, and a constant DC voltage is applied to the element to force a current to flow through solid electrolyte layers of both cells to cause migration of oxygen ions therethrough, from the measurement electrode to the reference electrode in one cell and reversely in the other.

Abstract: A device comprising an oxygen-sensitive element to be disposed in combustion gas exhausted from a combustor to detect deviation of actual air/fuel mixing ratio of a mixture supplied to the combustor from a stoichiometric ratio. The element is a combination of two oxygen concentration cells each having a solid electrolyte layer, a measurement electrode layer formed on one side of the electrolyte layer and a reference electrode layer formed on the opposite side and covered with a shield layer.

Abstract: A device having an oxygen sensing probe to be disposed in a combustion gas to detect actual air/fuel ratio values of an air-fuel mixture subjected to combustion. The probe is a combination of two oxygen concentration cells each having a porous solid electrolyte layer such as of zirconia, a porous measurement electrode layer on one side of the solid electrolyte layer and a reference electrode layer on the other side, with a shield layer thereon. Either the shield layers of the two cells or the solid electrolyte layers of the two cells are provided by a single layer which serves also as a substrate of the entire probe. The device includes DC power supply means for forcing a current to flow through the solid electrolyte of each cell thereby to cause oxygen ions to migrate through each solid electrolyte layer, from the reference electrode layer to the measurement electrode layer in one cell and reversely in the other cell.

Abstract: A method of detecting numerical values for air/fuel ratio of either a lean air-fuel mixture or a rich mixture supplied to, for example, a combustion engine by means of an oxygen sensor disposed in the exhaust gas. The sensor comprises a porous measurement electrode layer on one side of a porous solid electrolyte layer, e.g., of zirconia and a porous reference electrode layer on the other side with a shield layer thereon, so that the reference electrode layer communicates with the exhaust gas through pores in the sensor. Measurement is accomplished by keeping a DC current flowing between the two electrode layers to establish a reference oxygen partial pressure on the reference electrode side. The intensity of the current is made below a critical value above which an EMF generated by the sensor becomes substantially constant unless the air/fuel ratio changes across the stoichiometric ratio, and the direction of the current flow is chosen depending on whether the air-fuel mixture is a lean one or a rich one.

Abstract: An apparatus comprising a probe having an oxygen ion conductive solid electrolyte layer, a potentiometer and a DC power source connected to the probe. The probe comprises a porous and electronically conductive reference electrode layer on one side of the solid electrolyte layer, a similar measurement electrode layer on the other side of the electrolyte layer and a separation layer of an inactive material on the outer side of the reference electrode layer. The separation layer or the solid electrolyte layer, or both, has a porous structure and is formed such that the reference electrode communicates with an exterior atmosphere only through this porous structure, while either the separation layer or the electrolyte layer serves as a substrate of the probe. During measurement, the DC power source keeps a current flowing through the electrolyte layer between the two electrode layers to maintain a reference oxygen partial pressure at the interface between the electrolyte layer and the reference electrode layer.