An O.sub.2 sensor has a sensor element, which includes a solid electrolyte layer and a pair of electrodes, while the solid electrolyte layer is interposed between the electrodes. The O.sub.2 sensor outputs an electromotive force signal in response to an air-to-fuel ratio of exhaust gas of an engine, which serves as a sensing subject. A constant current circuit, which induces a flow of a predetermined constant electric current between the pair of electrodes of a sensor element, and a current sensing arrangement, which senses a current value of an actual electric current that is conducted through the sensor element, are provided. A microcomputer determines whether an abnormality of the constant current circuit is present based on the current value of the electric current, which is sensed with the current sensing arrangement, in a case where the constant current is induced by the constant current circuit.

A gas sensor includes a sensor element and a controller. The sensor element includes an element body provided with a measurement-object gas flow section therein, a measurement electrode disposed in the measurement-object gas flow section, an outer pump electrode provided in the element body so that the outer pump electrode comes into contact with a measurement-object gas, a reference electrode, a reference-gas introduction section that causes a reference gas to flow to the reference electrode, and a reference-gas adjustment pump cell constituted by including the outer pump electrode and the reference electrode. The controller performs a moisture-absorption-state diagnosis process of diagnosing a moisture absorption state around the reference electrode based on a pump current flowing through the reference-gas adjustment pump cell when the reference-gas adjustment pump cell is controlled to pump out oxygen from a periphery of the reference electrode to a periphery of the outer pump electrode.

A gas sensor includes a sensor element and a control unit for controlling the sensor element. The sensor element includes: an adjustment pump cell for adjusting an oxygen concentration in a measurement-object gas to a desired concentration; a current measurement pump cell for detecting a target gas to be measured in the measurement-object gas as a current value, the current measurement pump cell including: an inner measurement electrode and an outer measurement electrode; a reference electrode; and an electromotive force detection sensor cell for detecting an electromotive force value between the inner measurement electrode and the reference electrode. The control unit includes a switching unit for switching whether a current flows through the current measurement pump cell or not.

A gas sensor includes a sensor element including an element body, a first electrode, a second electrode, and a heater; a voltage acquisition section that acquires a voltage between the first electrode and the second electrode; a heater power supply; an external common lead that serves as both at least part of an electric circuit used to acquire the voltage by providing electrical continuity between the first electrode and the voltage acquisition section and at least part of an electric circuit used to supply an electric power from the heater power supply to the heater and that is disposed outside the sensor element; and a correction section that derives a value of a voltage drop in the external common lead in accordance with a heater current and that corrects the voltage acquired by the voltage acquisition section in accordance with the derived value of the voltage drop.

A control device of a nitrogen oxide sensor comprises a voltage control part configured to control voltage applied to the pump cell, and a temperature estimation part configured to estimate a temperature of the pump cell. The voltage control part is configured to make the voltage applied to the pump cell a voltage of a starting voltage of decomposition of water or more when the estimated temperature of the pump cell estimated by the temperature estimation part is within a predetermined temperature region of less than an activation temperature of the pump cell as control suppressing evaporation.

An electrochemical gas sensing element has a footprint of less than 5 mm×5 mm so the volume of electrolyte, the sizes of the electrodes, and the electrical interconnects are very small. This results in a fast stabilization after detecting gasses and enables rapid changes in bias voltage to target different gasses. The sensor body is ceramic, and the other components are stable at temperatures including solder reflow temperatures, thus allowing the use of conventional solder reflow techniques to mount the sensing element to a PCB. A sensor circuit is mounted on the sensing element body to detect the currents through the sensor electrode and digitally process the information, resulting in a more accurate analysis. The small size, low power consumption, and modularity allow the sensor element to be mounted in small handheld devices.

A sulfur oxide detection system includes an element part which includes a sensor cell and a diffusion regulating layer. The sensor cell includes a solid electrolyte layer, a first electrode arranged, and a second electrode. The sulfur oxide detection system also includes a voltage application circuit configured to apply a voltage to the sensor cell so that a potential of the second electrode becomes higher than a potential of the first electrode, and a current detection circuit configured to detect a current flowing between the first electrode and the second electrode. The sulfur oxide detection system further includes a controller coupled with the voltage application circuit and the current detection circuit, and configured to estimate a sulfur oxide concentration in a gas to which the first electrode is exposed by way of the diffusion layer.

This control device for an internal combustion engine is equipped with: an air/fuel ratio sensor provided to the exhaust passage of an internal combustion engine; and an engine control device that controls the internal combustion engine according to the output of the air/fuel ratio sensor. The air/fuel ratio sensor is equipped with: a gas chamber to be measured, into which exhaust gas flows; a pump cell that pumps oxygen into or out of the gas chamber to be measured according to the pump current; and a reference cell of which the reference cell output current detected varies according to the air/fuel ratio inside the gas chamber to be measured. The reference cell is equipped with: a first electrode that is exposed to the exhaust gas in the gas chamber to be measured; a second electrode exposed to a reference atmosphere; and a solid electrolyte layer arranged between the electrodes. The air/fuel ratio sensor is equipped with: a reference cell voltage applying device that applies a sensor applied voltage between the electrodes; and a reference cell output current detection device that detects, as the reference cell output current, the current flowing between the electrodes.

The object of the invention is to detect a concentration of a SOx included in an exhaust gas of an internal combustion engine easily and accurately by a limiting current type sensor. The invention relates to a SOx concentration detection device of the engine having a limiting current type sensor. The device of the invention comprises a detecting part for detecting the concentration of the SOx included in the exhaust gas by using an output current of the sensor while lowering a voltage applied to the sensor from a predetermined voltage.

A gas concentration detection device includes a pump cell, a sensor cell, a monitor cell, a sensor current detection unit detecting a current outputted by the sensor cell, a monitor current detection unit detecting a current outputted by the monitor cell, a voltage adjustment unit adjusting a pump cell voltage applied to the pump cell, and a sensitivity determination unit determining a gas sensitivity of at least one of the sensor cell or the monitor cell. The voltage adjustment unit changes the pump cell voltage from a target voltage into a detection voltage where the concentration of the residual oxygen supplied to the sensor cell and the monitor cell is increased. The sensitivity determination unit determines the gas sensitivity based on a detection current detected by at least one of the sensor current detection unit or the monitor current detection unit in accordance with the concentration of the residual oxygen.