In a method of performing active control between a lean operation state and a rich operation state on a vehicle engine including a three way catalyst in an exhaust path, on a downstream side with respect to the three way catalyst in the exhaust path, a limited current type NOx sensor having NH.sub.3 interference and also capable of detecting a change in an oxygen concentration on the downstream side is disposed, and an operation state of the vehicle engine is switched between a lean operation state and a rich operation state at a timing when a detection of a change in an oxygen concentration in an exhaust air flowing out from the three way catalyst or a detection of NOx or NH.sub.3 is performed first by the NOx sensor.

Embodiments relate generally to systems, devices, and methods for depositing an electrode and an electrolyte on a microelectromechanical system (MEMS) electrochemical sensor. A method may comprise providing a blade on a surface of a substrate; providing a ridge along the perimeter of the substrate; pressing the electrode and the electrolyte onto the blade and the ridge; cutting the electrode into multiple electrodes; positioning the electrolyte to contact the surface, the blade, and the ridge; and positioning the multiple electrodes to contact the surface, the blade, and the ridge.

A gas sensor, which includes a solid electrolyte layer including positive charge carriers to which detection-target gas coordinates, an electrode arranged on part of a plane of the solid electrolyte layer, and a unit configured to accelerate movements of the positive charge carriers.

A sensor element (100) including: a detection element portion (300) provided with at least one cell (130, 140) having a solid electrolyte (105, 109) and a pair of electrodes (104, 106, 108, 110) disposed on the solid electrolyte; a measurement chamber (107c) faced by one of the electrodes; and a diffusion resistance portion (115) through which a gas to be measured is introduced from outside into the measurement chamber. The sensor element further includes a porous protection layer (21) that is in direct contact with the diffusion resistance portion and which at least covers the diffusion resistance portion. The porous protection layer contains ceramic particles which serve as a backbone, and has pores formed in gaps between the ceramic particles. Further, a diameter ratio R represented by (an average diameter D1 (nm) of the pores / a particle diameter D2 (nm) at which an accumulated number of the ceramic particles accounts for 50%) is not greater than 100.

A solid electrolyte includes partially stabilized zirconia in which a stabilizer forms a solid solution in zirconia. The partially stabilized zirconia includes, as crystal particles that configure the partially stabilized zirconia, stabilizer low-concentration phase particles of which concentration of the stabilizer at a particle center is less than 4.7 mol % and stabilizer high-concentration phase particles of which the concentration of the stabilizer at the particle center is equal to or greater than 4.7 mol %. The partially stabilized zirconia includes an adjacent particle portion in which two or more particles of the stabilizer low-concentration phase particles of which an average particle size is greater than 0.1 μm are adjacent. An abundance ratio of the stabilizer high-concentration phase particles on a cross-section of the solid electrolyte is equal to or greater than 70% in terms of area ratio relative to all crystal particles.

A gas sensor includes: a sensor element; a plurality of element pads formed on a rear end portion of the sensor element; and a plurality of contact members holding the rear end portion of the sensor element and electrically connected respectively to the plurality of element pads. The plurality of contact members include contact members that each have an outer end surface protruding out from a corresponding one of end surfaces of the sensor element.

A CO.sub.2 mass estimation system includes: an acquisition element acquiring detected values in accordance with concentrations of oxygen, H.sub.2O, and CO.sub.2 contained in an engine exhaust gas output from a gas sensor; a setting element setting an air-fuel ratio of a mixture; and a calculation element calculating the mass of CO.sub.2 contained in the exhaust gas, wherein the calculation element calculates the concentrations of oxygen, H.sub.2O, and CO.sub.2 contained in the exhaust gas based on the sensor detected values, acquires concentrations of oxygen and H.sub.2O in air and the air-fuel ratio, calculates a composition ratio of at least C atoms contained in fuel based on the concentrations in the exhaust gas, the concentrations in the air, and the air-fuel ratio, and estimates the mass of CO.sub.2 contained in the exhaust gas based on the composition ratio and the amount of injection of the fuel into the engine.

An automotive exhaust gas sensor includes a gas chamber, an ultraviolet light source configured to emit ultraviolet light into the gas chamber and to photolyze an exhaust gas sample in the gas chamber, and an electrochemical detector disposed in the gas chamber and configured to detect a specified chemical in the photolyzed exhaust gas sample.

A gas sensor including a detection element section (71) including a solid electrolyte body and a pair of electrodes disposed on the solid electrolyte body, and a heater (73) for heating the detection element section (71). Inherent characteristic information is recorded in a record section (170) provided on the gas sensor or a record section provided separately from the gas sensor. The inherent characteristic information is information specific to the detection element section (71) and which allows setting of a relation between a change in the temperature of the detection element section (71) and a change in the internal resistance between the pair of electrodes.

A sensor element includes: an element base including: a ceramic body made of an oxygen-ion conductive solid electrolyte, and having a gas inlet at one end portion thereof; at least one internal chamber located inside the ceramic body, and communicating with the gas inlet under predetermined diffusion resistance; an electrochemical pump cell including an electrode located on an outer surface of the ceramic body, an electrode facing the chamber, and a solid electrolyte located therebetween; and a heater buried in the ceramic body, and an leading-end protective layer being porous, and covering a leading end surface and four side surfaces in a predetermined range of the element base on the one end portion. The leading-end protective layer has an extension extending into the gas inlet, and fixed to an inner wall surface of the ceramic body demarcating the gas inlet.