Method for determining oxidizable constituents in a gaseous mixture

• US 6,312,585 B1
• Filed: 07/06/1999
• Issued: 11/06/2001
• Est. Priority Date: 08/12/1997
• Status: Expired due to Term

• Current Assignee: Robert Bosch GmbH
• Original Assignee: Robert Bosch GmbH
• Inventors: Brinz, Thomas, Schumann, Bernd, Wahl, Thomas
• Primary Examiner(s): Warden, Jill
• Assistant Examiner(s): Olsen, Kaj K.
• Application Number:
  US09/269,948
• Time in Patent Office: 854 Days
• Field of Search: 204/424-429, 205/781, 205/784, 205/785, 205/787, 205/783.5, 205/786.5, 205/780.5
• US Class Current: 205/783.5
• CPC Class Codes: G01N 27/4075 Composition or fabrication of the electrodes and coatings thereon, e.g. catalysts

Abstract

A method and arrangement is described for determining oxidizable constituents in a gas mixture by using a solid electrolyte cell with at least one reference electrode and at least one working electrode made of electrically conducting mixed oxides which is sensitive to the oxidizable constituents, with the current between the reference electrode and the working electrode induced by electrochemical oxidation of a gas constituent to be determined being measured.

Claims

1. A method for determining at least one oxidizable constituent in a gas mixture using a solid electrolyte cell, including a solid electrolyte body, at least one reference electrode and at least one working electrode, the at least one working electrode being composed of electrically conducting mixed oxides and being sensitive to the at least one oxidizable constituent, wherein the mixed oxides are mixed metal oxides which include at least one of pseudobrookites, eschynites and fergusonites, the method comprising the steps of:

inducing a current, between the at least one reference electrode and the at least one working electrode, by an electrochemical oxidation of the at least one oxidizable constituent; and

measuring the current.

2. The method according to claim 1, further comprising the step of:

determining a temperature of the solid electrolyte cell using a temperature-dependent electrical conductivity of a solid electrode body of the solid electrolyte cell.

3. The method according to claim 2, further comprising the step of:

applying an a.c. voltage through the solid electrolyte body to the at least one reference electrode, wherein the at least one reference electrode includes a first reference electrode and a second reference electrode.

4. The method according to claim 3, wherein the a.c. voltage is between 0.1 Hz and 10⁶ Hz.

5. The method according to claim 3, wherein the a.c. voltage is between 1 kHz to 200 kHz.

6. The method according to claim 3, wherein an amplitude of the a.c. voltage is 50 mV.

7. The method according to claim 1, wherein the solid electrolyte body includes at least one of an yttrium stabilized zirconium oxide and an oxygen ion conducting material.

8. The method according to claim 1, wherein the mixed oxide is TiCr₂O₅.

9. An arrangement for determining at least one oxidizable constituent of a gas mixture, the arrangement comprising:

a solid electrolyte body;

at least one reference electrode; and

at least one working electrode, wherein the at least one working electrode includes at least one metal oxide selected from the group of pseudobrookites, eschynites and fergusonites, and the at least one metal oxide is sensitive to the at least one oxidizable constituent,

wherein a current is induceable between the at least one reference electrode and the at least one working electrode by an electrochemical oxidation of the at least one oxidizable constituent of the gas mixture.

10. The arrangement according to claim 9, wherein the solid electrolyte body includes at least one of an yttrium stabilized zirconium oxide and an oxygen ion conducting material.

11. The arrangement according to claim 9, wherein the at least one oxidizable constituent includes NH₃.

12. The arrangement according to claim 9, further comprising:

an amplifier arrangement, wherein the working electrode is coupled to an input of the amplifier arrangement; and

a feedback arrangement, wherein the feedback arrangement is coupled across the input and an output of the amplifier arrangement.

13. The arrangement according to claim 12, wherein:

the amplifier arrangement includes an operational amplifier, and the input of the amplifier arrangement is an inverting input of the operational amplifier; and

the feedback arrangement includes an impedance arrangement.

14. The arrangement according to claim 12, wherein:

a first current is coupled from the working electrode to the input;

a second current is coupled from the feedback arrangement to the input; and

the amplifier arrangement regulates the first current and the second current so that a common coupling point among the working electrode, the feedback arrangement and the input of the amplifier arrangement is a virtual ground.

15. An arrangement for determining at least one oxidizable constituent of a gas mixture, the arrangement comprising:

a solid electrolyte, wherein the solid electrolyte body includes at least one of an yttrium stabilized zirconium oxide and an oxygen ion conducting material;

at least one reference electrode;

at least one working electrode, wherein the at least one working electrode includes at least one metal oxide selected from at least one of pseudobrookites, eschynites and fergusonites, and the at least one metal oxide is sensitive to the at least one oxidizable constituent,

wherein a current is induceable between the at least one reference electrode and the at least one working electrode by an electrochemical oxidation of the at least one oxidizable constituent of the gas mixture;

an amplifier arrangement, wherein the working electrode is coupled to an input of the amplifier arrangement; and

a feedback arrangement, wherein the feedback arrangement is coupled across the input and an output of the amplifier arrangement.

16. The arrangement according to claim 15, wherein:

the amplifier arrangement includes an operational amplifier, and the input of the amplifier arrangement is an inverting input of the operational amplifier; and

the feedback arrangement includes an impedance arrangement.

17. The arrangement according to claim 15, wherein:

a first current is coupled from the working electrode to the input;

a second current is coupled from the feedback arrangement to the input; and

the amplifier arrangement regulates the first current and the second current so that a common coupling point among the working electrode, the feedback arrangement and the input of the amplifier arrangement is a virtual ground.

18. The method according to claim 15, wherein the mixed oxide is TiCr₂O₅.