Oxygen concentration detector

Claim 2

An oxygen concentration detector for detecting oxygen concentration in gases, comprising: at least one semiconductor (9) whose electric resistance varies with oxygen partial pressure of ambient atmosphere thereof, characterized by: at least one resistive body (10) having a composition including a number of portions (1,5) with a negative temperature coefficient of electric resistance and high-resistance substance layers (2,6) separating said portions (1,5) one from the other, and electrodes (3,4) contacting said composition; an AC power source (12) adapted to apply an AC current to said resistive body (10), so as to heat the resistive body (10), said AC power source (12) being operable at AC frequencies wich are not lower than a frequency which corresponds to point B of a complex impedance characteristic of the type defined, said resistive body (10) being so related to said semiconductor (9) that said semiconductor is heated by said resistive body upon application of said AC current; and means (16,17,18) for measuring the resistance of the semiconductor (9).

Claim 3

An oxygen concentration detector for detecting oxygen concentration in gases, comprising: at least one semiconductor (9) wholse electric resistance varies with oxygen partial pressure of ambient atmosphere thereof, characterized by: at least one of resistive body (10) having a composition including a number of portions (1,5) with a negative temperature coefficient of electric resistance and high-resistance substance layers (2,6) separating said portions (1,5) one from the other, and electrodes (3,4) contacting said composition, at least one said composition being an oxygen ion conductive solid electrolyte which forms an oxygen pump; an AC power source (12) adapted to apply an AC current to a selected said resistive body (10) so as to heat the resistive body, said AC power source being operable at AC frequencies which are not lower than a frequency which corresponds to point B of a complex impedance characteristic of the type defined, said resistive body (10) being so related to said semiconductor (9) that said semiconductor is heated by said resistive body upon application of said AC current; a DC source (15) connected to said oxygen pump for controlling oxygen partial pressure around the semiconductor (9) by applying DC current; and means (16,17,18) for measuring the resistance of the semiconductor (9).

Claim 4

An oxygen concentration detector for detecting oxygen concentration in gases, comprising: at least one semiconductor (9) wholse electric resistance varies with oxygen partial pressure of ambient atmosphere thereof, characterized by: at least one of resistive body (10) having a composition including a number of portions (1,5) with a negative temperature coefficient of electric resistance and high-resistance substance layers (2,6) separating said portions (1,5) one from the other, and electrodes (3,4) contacting said composition, at least one said composition being an oxygen ion conductive solid electrolyte which forms an oxygen pump; an AC power source (12) adapted to apply an AC current to a selected said resistive body (10) so as to heat the resistive body, said AC power source being operable at AC frequencies which are not lower than a frequency which corresponds to point B of a complex impedance characteristic of the type defined, said resistive body (10) being so related to said semiconductor (9) that said semiconductor is heated by said resistive body upon application of said AC current; a DC source (15) connected to said oxygen pump for controlling oxygen partial pressure around the semiconductor (9) by applying DC current; and means (16,17,18) for measuring the resistance of the semiconductor (9).

Claim 5

The detector of claim 1 or 2, wherein said portions with a negative temperature coefficient of electric resistance are fine grains (1).

Claim 6

The detector of claim 1 or 2, wherein said portions with a negative temperature coefficient of electric resistance are thin films (5).

Claim 7

The detector of any one of claims 1 to 4, wherein an AC current and an AC voltage between the electrodes (3,4) have a negative relation such that one increases, the other decreases.

Claim 8

The detector of any one of claims 1 to 5, wherein the AC current has a frequency at which an impedance of electrostatic capacitance (C 2 ) at the highly resistant region layers (2,6) interposed between the fine grains (1) or thin films (5) is smaller than a resistance (R 2 ) at the highly resistant region layers (2,6).

Claim 9

The detector of any one of claims 1 to 6, further comprising means (14,19) for detecting the impedance of selected one (1 0 ) of said resistive bodies by applying an AC ' current thereto, said AC current having a frequency which is not lower than a frequency which corresponds . to point B of a complex impedance characteristic of the type defined.

Claim 10

The detector of any one of claims 1 to 7, further comprising an auxiliary heating means related to one of said resistive bodies.

Claim 11

The detector of any one of claims 1 to 8, wherein one electrode (44) of said semiconductor (9) is connected to one electrode (45) of said resistive body (16) through a capacitor (42), said resistive body (10) being heated by said AC current.