Solid state pH sensor

• US 5,110,441 A
• Filed: 12/14/1989
• Issued: 05/05/1992
• Est. Priority Date: 12/14/1989
• Status: Expired due to Term

• Current Assignee: Monsanto Company (Bayer AG)
• Original Assignee: Monsanto Company (Bayer AG)
• Inventors: Williams, Hilliard L., Kinlen, Patrick J.
• Primary Examiner(s): Niebling, John
• Assistant Examiner(s): Leader, William T.
• Application Number:
  US07/450,783
• Time in Patent Office: 873 Days
• Field of Search: 204/433, 204/435, 204/418, 204/153.21
• US Class Current: 204/418
• CPC Class Codes: G01N 27/4035 Combination of a single ion-sensing electrode and a single reference electrode G01N27/406 and G01N27/413 take precedence

Abstract

A solid state pH sensor having an indicator electrode of metal/metal oxide and a reference electrode of metal/metal salt applied to electrically conductive conductors, such as electrically conductive cermet conductors and electrically conductive metal pins, imbedded in an electrically non-conductive substrate, such as electrically non-conductive ceramic substrates including S-glass substrates. The sensing portion of the sensor preferably has a coating of an annealed perfluorocarbon copolymer. Alternatively, the indicator or reference electrodes may be formed on separate electrically non-conductive substrates with each having an electrically conductive conductor imbedded therein. These indicator or reference electrodes may be utilized with each other or with prior art indicator or reference electrodes.

Claims

1. A solid state pH sensor for pH sensing equipment, said pH sensor comprising:

(a) an indicator electrode, said indicator electrode comprising

(1) a first electrically conductive conductor imbedded in a first electrically non-conductive substrate, said first electrically conductive conductor having a first electrically conductive conductor exposed portion,

(2) a metal/metal oxide coating on said first electrically conductive conductor exposed portion, such that said metal/metal oxide coating entirely covers said first electrically conductive conductor exposed portion,

(3) a first annealed perfluorocarbon copolymer coating on said metal/metal oxide coating, such that said first annealed perfluorocarbon copolymer coating entirely covers said metal/metal oxide coating, and

(4) an indicator contact zone electrically connected to said first electrically conductive conductor, wherein said indicator contact zone is utilized in making electrical contact between said first electrically conductive conductor and said pH sensing equipment; and

(b) a reference electrode, said reference electrode comprising

(1) a second electrically conductive conductor imbedded in a second electrically non-conductive substrate, said second electrically conductive conductor having a second electrically conductive conductor exposed portion,

(2) a metal/metal salt coating on said second electrically conductive conductor exposed portion, such that said metal/metal salt coating entirely covers said second electrically conductive conductor exposed portion,

(3) an immobilized electrolyte coating on said metal/metal salt coating, such that said immobilized electrolyte coating entirely covers said metal/metal salt coating,

(4) a second annealed perfluorocarbon copolymer coating on said immobilized electrolyte coating, such that said second annealed perfluorocarbon copolymer coating entirely covers said immobilized electrolyte coating, and

(5) a reference contact zone electrically connected to said second electrically conductive conductor, wherein said reference contact zone is utilized in making electrical contact between said second electrically conductive conductor and said pH sensing equipment;

(c) wherein said indicator and reference electrodes are electrically insulated from each other.

2. The solid state pH sensor of claim 1 having a first barrier layer of a noble metal between said first electrically conductive conductor exposed portion and said metal/metal oxide coating, such that said first barrier layer entirely covers said first electrically conductive conductor exposed portion and said metal/metal oxide coating entirely covers said first barrier layer, and a second barrier layer of noble metal between said second electrically conductive conductor exposed portion and said metal/metal salt coating, such that said second barrier layer entirely covers said second electrically conductive conductor exposed portion and said metal/metal salt coating entirely covers said second barrier layer.

3. A solid state pH sensor for pH sensing equipment, said pH sensor comprising:

(a) an indicator electrode, said indicator electrode comprising

(1) a first electrically conductive conductor imbedded in a first portion of an electrically non-conductive substrate, said first electrically conductive conductor having a first electrically conductive conductor exposed portion,

(2) a metal/metal oxide coating on said first electrically conductive conductor exposed portion, such that said metal/metal oxide coating entirely covers said first electrically conductive conductor exposed portion,

(3) an annealed perfluorocarbon copolymer coating on said metal/metal oxide coating, such that said annealed perfluorocarbon copolymer coating entirely covers said metal/metal oxide coating, and

(4) an indicator contact zone electrically connected to said first electrically conductive conductor, wherein said indicator contact zone is utilized in making electrical contact between said first electrically conductive conductor and said pH sensing equipment; and

(b) a reference electrode, said reference electrode comprising

(1) a second electrically conductive conductor imbedded in a second portion of said electrically non-conductive substrate, said second electrically conductive conductor having a second electrically conductive conductor exposed portion,

(2) a metal/metal salt coating on said second electrically conductive conductor exposed portion, such that said metal/metal salt coating entirely covers said second electrically conductive conductor exposed portion,

(3) an immobilized electrolyte coating on said metal/metal salt coating, such that said immobilized electrolyte coating entirely covers said metal/metal salt coating,

(4) an annealed perfluorocarbon copolymer coating on said immobilized electrolyte coating, such that said annealed perfluorocarbon copolymer coating entirely covers said immobilized electrolyte coating, and

(5) a reference contact zone electrically connected to said second electrically conductive conductor, wherein said reference contact zone is utilized in making electrical contact between said second electrically conductive conductor and said pH sensing equipment;

(c) wherein said indicator and reference electrodes are electrically insulated from each other.

4. The solid state pH sensor of claim 3 having a single perfluorocarbon copolymer coating entirely covering both of said metal/metal oxide coating and said immobilized electrolyte coating.

5. The solid state pH sensor of claim 3 having a first barrier layer of a noble metal between said first electrically conductive conductor exposed portion and said metal/metal oxide coating, such that said first barrier layer entirely covers said first electrically conductive conductor exposed portion and said metal/metal oxide coating entirely covers said first barrier layer, and a second barrier layer of noble metal between said second electrically conductive conductor exposed portion and said metal/metal salt coating, such that said second barrier layer entirely covers said second electrically conductive conductor exposed portion and said metal/metal salt coating entirely covers said second barrier layer.

6. A solid state pH sensor for pH sensing equipment, said pH sensor comprising:

(a) an indicator electrode, said indicator electrode comprising

(1) a first cermet conductor imbedded in a first portion of a ceramic substrate, said first cermet conductor having a first cermet conductor exposed portion,

(2) a metal/metal oxide coating or a metal oxide coating on said first cermet conductor exposed portion, such that said metal/metal oxide or metal oxide coating entirely covers said first cermet conductor exposed portion,

(3) an annealed perfluorocarbon copolymer coating on said metal/metal oxide or metal oxide coating, such that said perfluorocarbon entirely covers said metal/metal oxide or metal oxide coating, and

(4) an indicator contact zone electrically connected to said first cermet conductor, wherein said indicator contact zone is utilized in making electrical contact between said first cermet conductor and said pH sensing equipment, and

(b) a reference electrode, said reference electrode comprising

(1) a second cermet conductor imbedded in a second portion of said ceramic substrate, said second cermet conductor having a second cermet conductor exposed portion,

(2) a metal/metal salt coating on said second cermet conductor exposed portion, such that said metal/metal salt coating entirely covers said second cermet conductor exposed portion,

(3) an immobilized electrolyte coating on said metal/metal salt coating, such that said immobilized electrolyte coating entirely covers said metal/metal salt coating,

(4) an annealed perfluorocarbon copolymer coating on said immobilized electrolyte coating, such that said annealed perfluorocarbon copolymer coating entirely covers said immobilized electrolyte coating, and

(5) a reference contact zone electrically connected to said second cermet conductor, wherein said reference contact zone is utilized in making electrical contact between said second cermet conductor and said pH sensing equipment;

(c) wherein said indicator and reference electrodes are electrically insulated from each other.

7. The solid state pH sensor of claim 6 having a single perfluorocarbon copolymer coating entirely covering both of said metal/metal oxide or metal oxide coating and said immobilized electrolyte coating.

8. The solid state pH sensor of claim 6, having a first barrier layer of a noble metal between said first cerment conductor exposed portion and said metal/metal oxide coating or said metal oxide coating, such that said first barrier layer entirely covers said first cerment conductor exposed portion and said metal/metal oxide coating or metal oxide coating entirely covers said first barrier layer, and a second barrier layer of noble metal between said second cermet conductor exposed portion and said metal/metal salt coating, such that said second barrier layer entirely covers said cerment conductor exposed portion and said metal/metal salt coating entirely covers said second barrier layer.