Device for the simultaneous detection of dissimilar gas components

• US 5,298,146 A
• Filed: 10/26/1992
• Issued: 03/29/1994
• Est. Priority Date: 11/08/1991
• Status: Expired due to Fees

• Current Assignee: Compur Monitors Sensor Technology GmbH
• Original Assignee: Bayer AG
• Inventors: Braden, Christoph, Deprez, Jacques
• Primary Examiner(s): Niebling, John
• Assistant Examiner(s): Bell, Bruce F.
• Application Number:
  US07/966,229
• Time in Patent Office: 519 Days
• Field of Search: 204/406, 204/407, 204/412, 204/415, 204/431, 204/432, 422/82.03, 422/82.04
• US Class Current: 204/406
• CPC Class Codes: G01N 27/404 Cells with anode, cathode and cell electrolyte on the same side of a permeable membrane which separates them from the sample fluid , e.g. Clark-type oxygen sensors
• CPC Class Codes: G01N 33/0031 comprising two or more sensors, e.g. a sensor array

Abstract

The device for the simultaneous detection of dissimilar gas components contains a number of electrochemical, three-electrode measuring cells with a common electrolyte, that are formed from a number of working electrodes with a common counter-electrode and a common reference electrode. Measured values are generated with the aid of a potentiostatic evaluation circuit that also adjusts and sets the potentials at the working electrodes. The current signals correlated with the gas concentrations to be measured are displayed with the aid of current-measuring instruments 11₁ . . . 11_n in the lines to the working electrodes 5₁ . . . 5_n. At the same time it is important that all three-electrode measuring cells have a common counter-electrode 3 and a common reference electrode 4, and that the potentiostatic evaluation circuit 6 contains control loops 7₁ . . . 7_n which maintain the potentials of the working electrodes 5₁ . . . 5_n constant with respect to the reference electrode 4, both individually and independently of each other.

Claims

1. A device for the simultaneous detection of dissimilar gas components, comprising:

a. at least two three-electrode measuring cells, wherein each measuring cell comprises one working electrode, one counter-electrode and one referenced electrode and wherein the at least two measuring cells having a common counter-electrode, a common reference electrode and the working electrodes all in a common electrolyte;

b. A potentiostatic evaluation circuit comprising a separate control loop for each cell for maintaining a constant potential across each working electrode with respect to the reference electrode, the constant potential of one working electrode being individual and independent of the constant potential across other working electrodes; and

c. wherein the evaluation circuit further comprises means for separately detecting electric current flowing in each working electrode, each current corresponding to a gas concentration of a different gas component.

2. The device according to claim 1, wherein each control loop comprises a first operational amplifier effecting a high resistance measurement of the potential difference between an associated working electrode and the reference electrode, a second operational amplifier connected in series with the first operational amplifier for comparing the potential difference to a preset set-point voltage and means for adjusting a current output from the second operational amplifier to minimize any difference from the comparison.

3. The device according to claim 1, wherein the electrolyte comprises an electrolyte solution and wherein the working electrodes delimit the electrolyte on a gas side thereof and comprises physically separate measuring fields on a common membrane and wherein the counter-electrode and reference electrode are disposed on an opposite side of the electrolyte.

4. The device according to claim 3, further comprising gas specific filters connected in series with the measuring fields.

5. The device according to claim 3, wherein the working electrodes comprise catalysts.

6. The device according to claim 3, further comprising orifices or diffusion membranes in series with the working electrodes for adjusting the sensitivity thereof.

7. The device according to claim 1, for the measurement of HCl and Cl, wherein the electrolyte consists of aqueous sulphuric acid and the working electrodes consist of gold.