A gas sensor includes a detection circuit unit that detects a specific gas component in measured gas based on output from a sensor element. The detection circuit unit includes an AC voltage application unit that applies an AC voltage signal to a pair of electrode units in an electrochemical cell, a gas concentration detection unit that detects concentration information on the specific gas component from a DC signal component included in an output signal provided by the electrochemical cell, and a cell temperature detection unit that detects temperature information on the electrochemical cell from an AC signal component included in the output signal. The cell temperature detection unit includes a signal extraction unit that removes the DC signal component to separate the AC signal component from the output signal, and a synchronous detection unit that performs synchronous detection on the separated AC signal component using the AC voltage signal.

The heater 72 of the heater portion includes the linear portions 78 and the bend portions 77. A resistance value per unit length of the bend portions 77 at least at a temperature within a temperature range of no less than 700° C. and no more than 900° C. is lower than a resistance value per unit length of the linear portions 78.

A sensor element includes: an element base including: a ceramic body made of an oxygen-ion conductive solid electrolyte, and having an inlet at one end portion thereof; at least one internal chamber located inside the ceramic body, and communicating with the gas inlet; and an electrochemical pump cell including an outer electrode, an inner electrode facing the chamber, and a solid electrolyte therebetween, and a porous leading-end protective layer covering a leading end surface and four side surfaces in a predetermined range of the element base on the one end portion, wherein the 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, and a gap communicating with the gas inlet is located in the protective layer, with demarcated by a portion of the protective layer continuous with the extension.

A gas sensor element for detecting a specific gas component in a measured gas, comprising: an element body in the form of a long plate having a gas detection part at an end thereof on a distal end face side in a longitudinal direction; and a porous protective layer covering an outer periphery of the end on said end face side of the element body, wherein in a cross section including two adjacent ones of the end face and side faces connected to the end face, an outer surface of the protective layer facing an element corner where the two faces meet has a shape with a corner part, and a ratio of an assumed diameter of a water droplet contained in the measured gas in a use environment to an effective length of the corner part in the cross section is equal to or larger than 1.5.

Provided is a gas sensor element capable of realizing both highly accurate concentration measurement in environments where the concentration of a specific gas in a measurement target gas is high and highly accurate concentration measurement in environments where the concentration is low. A gas sensor according to one aspect of the present invention adjusts a sensor element drive temperature such that the value of cell resistance of a main pump cell is a predetermined value. Further, in the gas sensor according to one aspect of the present invention, the slope of the cell resistance of the main pump cell is larger than the slope of cell resistance of a measurement pump cell.

Provided is a gas sensor element capable of realizing highly accurate concentration measurement in both environments where the concentration of a specific gas in a measurement target gas is high and where the concentration is low. A gas sensor according to one aspect of the present invention determines whether the concentration of a predetermined gas component in a measurement target gas is higher or lower than a predetermined concentration. If it is determined that the concentration is lower, a specific temperature that a sensor element is to reach as a result of being heated by a heater unit is set to be lower than the specific temperature set if it is determined that the concentration is higher.

A gas sensor for sensing a predetermined gas component contained in a measurement gas includes: a sensor element including a sensing part on one end portion thereof; a casing in which the sensor element is contained and secured; and a connector disposed in the casing, wherein the casing includes: an outer tube including a main portion in which a reference gas is included and a sealing portion as an end portion with a diameter smaller than the main portion so that another end portion of the sensor element protrudes to the main portion, a rubber seal member fitted into the sealing portion to seal the outer tube, and a spacer intervening between the seal member and the connector, and the spacer includes: a resin first spacer contacting with the seal member and having higher heat resistance than the seal member and a ceramic second spacer contacting with the connector.

A ceramic planar sensor element having four contact surfaces and three vias, for example for a lambda sensor. Measures are provided for increasing the loadability of the sensor element in relation to mechanical stresses. The measures relate in particular to the arrangement of the vias and to the design of insulating layers in the interior of the sensor element.

Apparatus and associated methods relate to a one-piece structure for a solid electrolyte chemical sensor (SECS) having a first surface defining a cavity (210, 305, 415) designed to receive a substrate (215, 350, 410) that retains a solid electrolyte (365, 440), an internal water impermeable coating (425) on at least a portion of the first surface, a second surface that is substantially coplanar with an adjacent peripheral edge of a top surface of the substrate (215, 350, 410) when the substrate (215, 350, 410) is received in the cavity (210, 305, 415), and a plurality of electrical contacts (335, 340, 345, 450a-450b) disposed on the second surface adapted to electrically couple with the electrodes (435a-435c) on the substrate (215, 350, 410) when the substrate (215, 350, 410) is received in the cavity (210, 305, 415) and electrical paths are provided between respective electrical contacts (335, 340, 345, 450a-450b) and electrodes (435a-435c).

A connector includes two insulators which hold contacts connected to lead wires and are arranged on two surfaces of a ceramic element, a spring component which includes two cantilever-shaped spring pieces and has a flexed portion at a middle portion of each spring piece, and a cylindrical sleeve. The two spring pieces are located over two outer surfaces of the two insulators, and are elastically deformed toward the two insulators by the sleeve hanging over the two spring pieces. The two insulators pushed by the flexed portions of the two elastically deformed spring pieces hold the ceramic element from two sides to push the contacts against the terminal electrodes.