In a sensor element for a limiting-current type gas sensor measuring concentration of NOx in a measurement gas, an inner pump electrode located to face a first internal space communicating, under predetermined diffusion resistance, with a gas inlet through which a measurement gas is introduced from an external space is made of a cermet of a Pt—Au alloy and zirconia, and includes a first portion located on a surface farther from a heater part and a second portion located on a surface closer to the heater part from among surfaces opposing each other in the first internal space, an Au content with respect to the Pt—Au alloy as a whole of the second portion is 0.3 wt % or more smaller than that of the first portion, and a total area of the first portion and the second portion is 10 mm.sup.2 to 25 mm.sup.2.

A bio-field effect transistor (bioFET) system includes a bioFET configured to receive a first voltage signal and output a current signal. A logarithmic current-to-time converter is connected to the bioFET and is configured to receive the current signal and convert the current signal to a time domain signal. The time domain signal varies logarithmically with respect to the current signal, such that the time domain signal varies linearly with respect to the first voltage signal.

A gas sensor includes a sensor element, and the sensor element includes a bottomed tubular solid electrolyte, a detection electrode provided on an outer surface of the solid electrolyte, a reference electrode provided on an inner surface of the solid electrolyte. The detection electrode of the sensor element includes a detection electrode section provided at a position on a tip side of an axial direction, an attachment electrode section provided at a position on a base end side of the axial direction, and a lead electrode section provided at a position where the detection electrode section is connected to the attachment electrode section. An insulating layer is provided between a tube of the solid electrolyte and each of the attachment electrode section and the lead electrode section.

A gas sensor includes a sensor element, and the sensor element includes a bottomed tubular solid electrolyte, a detection electrode provided on an outer surface of the solid electrolyte, a reference electrode provided on an inner surface of the solid electrolyte. The detection electrode of the sensor element includes a detection electrode section provided at a position on a tip side of an axial direction, an attachment electrode section provided at a position on a base end side of the axial direction, and a lead electrode section provided at a position where the detection electrode section is connected to the attachment electrode section. An insulating layer is provided between a tube of the solid electrolyte and each of the attachment electrode section and the lead electrode section.

A sensor element includes an element body that contains a measurement-object gas flow section and a heat generation portion. The measurement-object gas flow section includes a main pump chamber, an auxiliary pump chamber, and a measurement chamber. A distance X1 in a left-right direction between a part of a first inner linear portion and a part of a second inner linear portion of the heat generation portion that overlap a main pump chamber projection region is equal to or more than ⅓ of a width Wp of the main pump chamber projection region in the left-right direction. A distance X2 in the left-right direction between a part of the first inner linear portion and a part of the second inner linear portion that overlap an auxiliary pump chamber projection region is equal to or more than 0.4 times the width Wp.

A sensor element includes an element body that contains a measurement-object gas flow section and a heat generation portion. The measurement-object gas flow section includes a main pump chamber, an auxiliary pump chamber, and a measurement chamber. A distance X1 in a left-right direction between a part of a first inner linear portion and a part of a second inner linear portion of the heat generation portion that overlap a main pump chamber projection region is equal to or more than ⅓ of a width Wp of the main pump chamber projection region in the left-right direction. A distance X2 in the left-right direction between a part of the first inner linear portion and a part of the second inner linear portion that overlap an auxiliary pump chamber projection region is equal to or more than 0.4 times the width Wp.

A gas sensor element includes a solid electrolyte having oxygen-ion conductivity, a first electrode film located on one side of the solid electrolyte, a second electrode film located on the other side of the solid electrolyte. At least one of the first electrode film and the second electrode film includes noble metal particles, solid electrolyte particles having oxygen-ion conductivity, and pores, and a capacitance in the electrode film is 80 μF or less. A gas sensor includes the gas sensor element.

A gas sensor element includes a solid electrolyte having oxygen-ion conductivity, a first electrode film located on one side of the solid electrolyte, a second electrode film located on the other side of the solid electrolyte. At least one of the first electrode film and the second electrode film includes noble metal particles, solid electrolyte particles having oxygen-ion conductivity, and pores, and a capacitance in the electrode film is 80 μF or less. A gas sensor includes the gas sensor element.

In order to suppress a deterioration in the measurement precision while also reducing the manufacturing cost of a gas sensor element, an aspect of the present invention is directed to a gas sensor element including: a stack formed by stacking a plurality of oxygen ion-conductive solid electrolyte layers, and including an internal space configured to receive a measurement target gas from the outside, a first face adjacent to the internal space, and a second face adjacent to an external space; a first pump electrode provided on the first face; a second pump electrode provided on the second face; a first lead formed on the first face so as to extend from the first pump electrode; and a second lead formed on the second face so as to extend from the second pump electrode and configured to be electrically connected to the first lead. At least one of the first and second leads has a shape with a maximum current density of 3.5 A/mm.sup.2 or less.

In order to suppress a deterioration in the measurement precision while also reducing the manufacturing cost of a gas sensor element, an aspect of the present invention is directed to a gas sensor element including: a stack formed by stacking a plurality of oxygen ion-conductive solid electrolyte layers, and including an internal space configured to receive a measurement target gas from the outside, a first face adjacent to the internal space, and a second face adjacent to an external space; a first pump electrode provided on the first face; a second pump electrode provided on the second face; a first lead formed on the first face so as to extend from the first pump electrode; and a second lead formed on the second face so as to extend from the second pump electrode and configured to be electrically connected to the first lead. At least one of the first and second leads has a shape with a maximum current density of 3.5 A/mm.sup.2 or less.