Process for operating an electrochemical measuring cell

• US 6,344,133 B1
• Filed: 05/18/1999
• Issued: 02/05/2002
• Est. Priority Date: 11/06/1998
• Status: Active Grant

• Current Assignee: Dräger Sicherheitstechnik GmbH (FPS Vermögensverwaltung GmbH)
• Original Assignee: Dräger Sicherheitstechnik GmbH (FPS Vermögensverwaltung GmbH)
• Inventors: Formica, Philip Michael, Kaneblei, Ingo
• Primary Examiner(s): TUNG, TA HSUNG
• Application Number:
  US09/313,825
• Time in Patent Office: 994 Days
• Field of Search: 204/400, 204/402, 204/415, 204/431, 204/432, 205/775, 205/782, 205/782.5, 205/783
• US Class Current: 205/775
• 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 27/4045 for gases other than oxygen

Abstract

A process for operating an electrochemical measuring cell (1) is described, with which it is possible to carry out gas concentration measurements already shortly after switching on the measuring cell (1). The process includes the steps that potential voltage pulses are applied to the measuring cell (1) in a state of readiness of the measuring cell (1), in which the potential voltage is switched off. A system and device are also described.

Claims

1. A process for operating an electrochemical measuring cell. the process comprising the steps of:

providing an electrochemical cell with a measuring cell housing filled with an electrolyte and closed with a gas permeable membrane and having a measuring electrode and a counterelectrode;

connecting the measuring electrode and the counterelectrode to a potential voltage source with a pulse generator;

applying a substantially constant measuring potential voltage U₀ to the cell, supplied by the potential voltage source in a gas measuring operation;

generating readiness potential voltage pulses in a gas cell readiness operation using the potential voltage source and applying the readiness potential voltage pulses to the measuring electrode and the counterelectrode to provide a state of readiness of the cell during said gas cell readiness operation each of said pulses including a potential voltage pulse amplitude applied for a pulse period with successive pulse periods separated by an interpulse period during which no potential is applied to said measuring electrode and the counterelectrode.

2. The process in accordance with claim 1, wherein the readiness potential voltage pulses have the amplitude of the measuring potential voltage U₀.

3. The process in accordance with claim 2, wherein the readiness potential voltage pulses are selected such that an interpulse period t_p between 1 minute and 60 minutes is provided.

4. The process in accordance with claim 1, wherein the readiness potential voltage pulses are selected such that an interpulse period t_p between 1 minute and 60 minutes is provided.

5. The process in accordance with claim 1, wherein a pulse length t_i to duration of interpulse period t_p ratio ranging from 1:

10 to 1;

100 is set for the readiness potential voltage pulses.

6. The process in accordance with claim 5, wherein gas concentration measurements are carried out and the ratio of the pulse length t_i to the duration of the interpulse period t_p is set corresponding to the gas concentration measured.

7. A electrochemical measuring cell system, comprising:

an electrochemical cell;

a potential voltage source connected to said cell;

a pulse generator; and

a control for establishing a measuring state with a potential voltage U₀ applied to the cell and supplied by the potential voltage source in a measuring operation and establishing a readiness state with potential voltage pulses generated by the potential voltage source and applied to the cell in the state of readiness of the cell, in which the potential voltage is not applied between the pulses.

8. The system in accordance with claim 7, wherein the potential voltage pulses have the amplitude of the potential voltage U₀.

9. The system in accordance with claim 7, wherein the potential voltage pulses are selected such that an interpulse period t_p between 1 minute and 60 minutes is provided:

a pulse length t_i to duration of interpulse period t_p ratio ranging from 1;

10 to 1;

100 is set for potential voltage pulses.

10. The system in accordance with claim 7, wherein gas concentration measurements are carried out and a ratio of pulse length t_i to interpulse period t_p is set corresponding to the gas concentration measured.

11. A measuring cell system in accordance with claim 7, further comprising:

a measuring electrode conductive line connected to said measuring electrode;

a counter electrode conductive line connected to said counter electrode;

a resistor provided in series in said counter electrode conductive line;

tap lines for measuring a sensor current by providing an indication of the voltage drop across said resistor;

a potentiostat connected to said measuring electrode conductive line and said counter electrode conductive line;

a switch connecting said potential voltage source to said potentiostat, said control unit controlling said switch to establish said measuring state with said potential voltage U₀ applied to the cell and to establish said readiness state with said potential voltage pulses applied to the cell.

12. A process for operating an electrochemical measuring cell, the process comprising the steps of:

providing an electrochemical cell system with an electrochemical cell having a measuring cell housing filled with an electrolyte and closed with a gas permeable membrane and having a measuring electrode and a counterelectrode, a potential voltage source connected to the cell, a pulse generator and a control;

connecting the measuring electrode and a counterelectrode to the potential voltage source with the pulse generator;

establishing a measuring state with the cell by applying a substantially constant measuring potential voltage U₀ to the measuring electrode and a counterelectrode, the measuring potential voltage being supplied by the potential voltage source;

establishing an off state with the cell with no measuring potential voltage applied to the measuring electrode and the counterelectrode;

establishing a readiness state with the cell by generating potential voltage pulses with the potential voltage source and applying the potential voltage pulses to the measuring electrode and the counterelectrode, each of the pulses including a potential voltage pulse amplitude applied for a pulse period with each of successive pulse periods separated by an interpulse period during which no measuring potential voltage is applied to the measuring electrode and the counterelectrode.

13. A process in accordance with claim 12, wherein:

the measuring state is established after said readiness state;

the potential voltage pulses are applied substantially periodically;

establishing a measuring state includes measuring a concentration of a gaseous sample.

14. A process in accordance with claim 12, wherein:

the amplitude of the measuring potential voltage and the polarity of the measuring potential voltage are substantially equal to the amplitude of the potential voltage pulses and the polarity of the potential voltage pulses.

15. A process in accordance with claim 12, wherein:

the measuring potential voltage is applied during said measuring state for a period longer than the pulse period.

16. A process in accordance with claim 12, wherein:

measurements of the sample are carried out at predetermined intervals and a ratio of pulse length t_i to interpulse period t_p is varied corresponding to said measurements.

17. A process for measuring gas concentration of a gas sample, the process comprising the steps of:

exposing an electrochemical cell to a gas sample, the electrochemical cell having a measuring cell housing filled with an electrolyte and closed with a gas permeable membrane and having a measuring electrode and a counterelectrode;

applying a plurality of voltage pulses to the cell to form a readiness state of the cell;

applying a substantially constant voltage to the cell to form a measuring state of the cell; and

measuring the sample with said cell in said measuring state.

18. A process in accordance with claim 17, wherein:

the measuring state is established after said readiness state; and

the potential voltage pulses are applied substantially periodically;

the amplitude of the measuring potential voltage and the polarity of the measuring potential voltage are substantially equal to the amplitude of the potential voltage pulses and the polarity of the potential voltage pulses; and

the measuring potential voltage is applied during said measuring state for a period longer than the pulse period.

19. A process in accordance with claim 17, wherein:

measurements of the sample are carried out at predetermined intervals and a ratio of pulse length t_i to interpulse period t_p is varied corresponding to said measurements.