# US 5,351,029 A · Sensor for determining carbon monoxide

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- Number: US 5,351,029 A
- Document ID: US5351029A
- Status: Granted
- Kind: A
- Application number: 08/078,291
- Filed: 1993-06-22
- Granted: 1994-09-27
- Earliest claimed: 1991-01-15
- Assignees: Robert Bosch GmbH
- Inventors: Gerhard Huth; Detlef Baresel
- Web page: https://patentgrep.com/patent/US5351029A

## CPC

- G01N 27/12: of a solid body in dependence upon absorption of a fluid; of a solid body in dependence upon reaction with a fluid {, for detecting components in the fluid}
- G01N 33/004: {CO or CO2}
- G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q)

## Abstract

The invention relates to a sensor for the determination of carbon monoxide, especially in gas mixtures containing oxygen, on the basis of doped metal oxides whose electric conductivity is a function of the composition of the gas mixtures. Suitable metal oxides are those having n-type conductivity, the dopants used being other oxides of a metal having a maximum valency <4; oxides of a metal catalyzing the reaction of carbon monoxide with oxygen to give carbon dioxide, each in amounts from 0.01 to 0.2 mol %; and from 0.001 to 0.1 mol % of an oxide of a metal of the 5th subgroup of the Periodic Table of Elements. The sensors are notable for a small resistance-temperature coefficient while having high sensitivity and low hysteresis.

## Claims

### Claim 1

A sensor for the determination of carbon monoxide in a gas mixture comprising a doped n-type metal oxide whose electric conductivity is a function of the composition of the gas mixture, dopants for said metal oxide comprising (a) from 0.01 to 0.2 mol % of an oxide of another metal having a maximum valency <4 together with (b) from 0.01 to 0.2 mol % of an oxide of a metal, which catalyses the reaction of carbon monoxide to carbon dioxide and (c) from 0.001 to 0.1 mol % of an oxide of a metal of the 5th subgroup of the Periodic Table of the Elements.

### Claim 2 (depends on 1)

The sensor according to claim 1, wherein the n-type metal oxide is tin(IV) oxide which is doped with magnesium oxide, palladium oxide and the oxide of a metal of the 5th subgroup of the Periodic Table of the Elements.

### Claim 3 (depends on 1)

The sensor according to claim 1, wherein the oxide of a metal of the 5th subgroup of the Periodic Table of the Elements is tantalum (V).

### Claim 4 (depends on 2)

The sensor according to claim 2, wherein the oxide of a metal of the 5th subgroup of the Periodic Table of the Elements is tantalum (V).

### Claim 5 (depends on 1)

A sensor as defined in claim 1 for determining carbon monoxide in a gas mixture containing oxygen.