ELECTROCHEMICAL SENSOR INSTRUMENTATION

• US 3,718,568 A
• Filed: 05/21/1971
• Issued: 02/27/1973
• Est. Priority Date: 05/21/1971
• Status: Expired due to Term

• Current Assignee: Fisher Scientific Co. (Thermo Fisher Scientific Incorporated)
• Original Assignee: Robert T. Neuwelt
• Inventors: Neuwelt, Robert T.
• Primary Examiner(s): Kaplan, G. L.
• Application Number:
  US05/145,839
• Time in Patent Office: 648 Days
• Field of Search: 204/195P,195M,195L,1T 324/51,29
• US Class Current: 204/401
• 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 27/4162 investigating the composition of gases, by the influence exerted on ionic conductivity in a liquid conductometry in general G01N27/06; amperometric gas sensors G01N27/404
• CPC Class Codes: G01N 27/4163 checking the operation of, or calibrating, the measuring apparatus G01N27/3274, G01N27/4175 and G01N33/0006 take precedence

Abstract

Apparatus for monitoring the integrity of a selectively permeable membrane in an electrochemical sensor system that includes two half cells, a monitoring electrode having a surface disposed in the sample chamber, and a monitoring circuit connected to a half cell on the opposite side of the selectively permeable membrane from the monitoring electrode for sensing current flow resulting from the difference in electric potential at the monitoring electrode and the galvanic potential genereated by the connected half cell for providing an output signal to indicate the integrity of the selectively permeable membrane.

Claims

2. The system as claimed in claim 1 wherein said sample chamber is bounded by two selectively permeable membranes, each said membrane separating a corresponding sensing half cell from material in said sample chamber to be analyzed, and further including a second monitoring circuit connected to a half cell on the opposite side of the second selectively permeable membrane from said monitoring half cell, said second monitoring circuit sensing current flow resulting from the difference between the half cell potentials of said monitoring half cell and the half cell on the opposite side of said second selectively permeable membrane from said monitoring half cell.

3. The system as claimed in claim 1 wherein the difference between the half cell potentials of said monitoring half cell and said one half cell is less than 0.5 volt.

4. An electrochemical sensor system comprising a sensing half cell including a first electrode, a cooperating hAlf cell including a second electrode, a sample chamber for holding the material to be analyzed, at least one wall of the sample chamber being bounded by a selectively permeable member that separates said sensing half cell from the material in said sample chamber to be analyzed, a monitoring half cell including a third electrode that has a surface exposed in said sample chamber, and a monitoring circuit connected to one of said half cells on the opposite side of said selectively permeable member from said monitoring half cell for sensing current flow resulting from the difference between the half cell potentials of said monitoring and said one half cells, said monitoring circuit comprising means for providing an output signal as a function of a predetermined value of that current flow and including an operational amplifier having a first input terminal connected to said monitoring half cell and a second input terminal connected to said one half cell.

5. An electrochemical sensor system comprising a sensing half cell including a first electrode, a cooperating half cell including a reference electrode, a sample chamber for holding the material to be analyzed, at least one wall of the sample chamber being bounded by a selectively permeable member that separates said sensing half cell from the material in said sample chamber to be analyzed, a monitoring half cell including a third electrode that is electrically connected to ground and has a surface exposed in said sample chamber, and a monitoring circuit connected to one of said half cells on the opposite side of said selectively permeable member from said monitoring half cell for sensing current flow resulting from the difference between the half cell potentials of said monitoring and said one half cells, said monitoring circuit including means for providing an output signal as a function of a predetermined value of that current flow.

6. An electrochemical sensor system comprising a sensing half cell including a first electrode, a cooperating half cell including an anode electrode, a sample chamber for holding the material to be analyzed, at least one wall of the sample chamber being bounded by a selectively permeable member that separates said sensing half cell from the material in said sample chamber to be analyzed, a monitoring half cell including a third electrode that is electrically connected to ground and has a surface exposed in said sample chamber, and a monitoring circuit connected to one of said half cells on the opposite side of said selectively permeable member from said monitoring half cell for sensing current flow resulting from the difference between the half cell potentials of said monitoring and said one half cells, said monitoring circuit including means for providing an output signal as a function of a predetermined value of that current flow.

7. The system as claimed in claim 1 wherein said monitoring circuit includes a threshold circuit responsive to the monitored current flow for providing an output signal fault indication only when said monitored current flow exceeds a predetermined value.

8. An electrochemical sensor system comprising a sensing half cell including a first electrode, a cooperating half cell including a second electrode, a sample chamber for holding the material to be analyzed, at least one wall of the sample chamber being bounded by a selectively permeable member that separates said sensing half cell from the material in said sample chamber to be analyzed, a monitoring half cell including a third electrode that has a surface exposed in said sample chamber, and a monitoring circuit connected to one of said half cells on the opposite side of said selectively permeable member from said monitoring half cell for sensing current flow resulting from the difference between the half cell potentials of said monitoring and said one half cells, said monitoring circuit comprising means for providing an output signal as a function of a predetermined value of that current flow and including an operational ampliFier having a first input terminal connected to said monitoring half cell and a second input terminal connected to said one half cell and a threshold circuit responsive to the monitored current flow for providing an output signal fault indication only when said monitored current flow exceeds a predetermined value.

9. The system as claimed in claim 8 wherein said difference between the half cell potentials of said monitoring half cell and said one half cell is less than 0.5 volt.

10. An electrochemical sensor system comprising a first electrode assembly including a first sensing half cell including a first electrode, a first cooperating half cell including a second electrode assembly including a second sensing half cell that includes a third electrode and a second cooperating half cell that includes a fourth electrode, each said electrode assembly including a separate selectively permeable membrane and means for releasably connecting each said membrane to its corresponding electrode assembly in intimate contact with a surface thereof, a sample chamber for holding material to be analyzed, a first portion of said sample chamber being bounded by a first selectively permeable membrane that separates said first sensing half cell from the material in said sample chamber to be analyzed and a second portion of said sample chamber being bounded by a second selectively permeable membrane that separates said second sensing half cell from the material in said sample chamber to be analyzed, a first monitoring circuit including a first monitoring half cell, said first monitoring circuit being connected to one of the half cells of said first electrode assembly on the opposite side of said first selectively permeable membrane from said monitoring half cell for sensing current flow resulting from the difference between the half cell potentials of said monitoring and said one half cell of said first electrode assembly, and a second monitoring circuit including a second monitoring half cell, said second monitoring circuit being connected to a half cell of said second electrode assembly on the opposite side of the second selectively permeable membrane from said monitoring half cell for sensing current flow resulting from the difference between the half cell potentials of said monitoring half cell and said one half cell of said second electrode assembly, each said monitoring circuit including means for providing an output signal as a function of a predetermined value of that current flow.

11. Apparatus for monitoring the integrity of a selectively permeable membrane in an electrochemical sensor system, comprising a sensing half cell including a first electrode, a cooperating half cell including a second electrode, a sample chamber for holding the material to be analyzed, said sample chamber having a port in a wall thereof and said selectively permeable membrane being disposed across said port to separate said sensing half cell from the material in said sample chamber to be analyzed, a monitoring half cell including a third electrode that has a surface disposed in said sample chamber, said monitoring half cell generating an electric potential as a function of the material in which it is disposed, and a monitoring circuit connected to said cooperating half cell on the opposite side of said selectively permeable membrane from said monitoring half cell for sensing current flow resulting from the difference in the electric potential generated by said monitoring half cell and the galvanic potential generated by said cooperating half cell, said monitoring circuit including means for providing an output signal as a function of a pre-determined value of that current flow to provide an indication of the integrity of said selectively permeable membrane.

12. The apparatus as claimed in claim 11 wherein said sensing and cooperating half cells are disposed in an electrode assembly, said selectively permeable membrane is a separate member and further including means for releasably connecting sAid membrane to said electrode assembly in intimate contact with a surface thereof.

13. The apparatus as claimed in claim 12 wherein the potential difference between said electric potential and said galvanic potential is less than 0.5 volt.

14. The apparatus as claimed in claim 13 wherein said monitoring circuit includes an operational amplifier having a first input terminal connected to said monitoring half cell and a second input terminal connected to said one half cell.

15. The apparatus as claimed in claim 14 wherein said monitoring circuit includes a threshold circuit responsive to the monitored current flow for providing an output signal fault indication only when said monitored current flow exceeds a predetermined value.

16. The apparatus as claimed in claim 15 and further including a second electrode assembly including a sensing half cell including a fourth electrode, a cooperating half cell including a fifth electrode, a second selectively permeable membrane, and means for releasably attaching said second membrane to said second electrode assembly in intimate contact with a surface thereof and a second monitoring circuit connected to the cooperating half cell of said second electrode assembly on the opposite side of the second selectively permeable membrane from said monitoring half cell, said second monitoring circuit sensing current flow resulting from the potential difference between said monitoring half cell and the cooperating half cell of said second electrode assembly to which it is connected.

17. The apparatus as claimed in claim 16 wherein said first electrode is a platinum member, said second, fourth and fifth electrodes are silver/silver chloride members, and said third electrode is a stainless steel member.