Insulated core electrode for pH sensor

• US 5,221,456 A
• Filed: 10/22/1991
• Issued: 06/22/1993
• Est. Priority Date: 10/22/1991
• Status: Expired due to Fees

• Current Assignee: Rosemount Incorporated (Emerson Electric Company)
• Original Assignee: Rosemount Incorporated (Emerson Electric Company)
• Inventors: Rutt, Donald R., Toy, Adrian C., Sittler, Fred C., Benton, Barry W., Majerus, Lawrence R.
• Primary Examiner(s): Tung, T.
• Assistant Examiner(s): Bell, Bruce F.
• Application Number:
  US07/781,106
• Time in Patent Office: 609 Days
• Field of Search: 204/416, 204/433, 204/435, 204/243 R, 204/418, 204/419
• US Class Current: 204/416
• CPC Class Codes: G01N 27/333 Ion-selective electrodes or membranes glass electrodes G01N27/36

Abstract

A pH sensor has a core of an electrochemically inert insulating or semi-conductive material, and is coated with an electrically conductive, electrochemically sensitive coating. The preferred core is insulating and made of alumina, with a thin coating of iridium oxide deposited over at least a portion of the outer surface of the core. The coating is carried to a surface remote from the sensing surface and is used for making electrically conductive connections that lead to remote circuitry. The core is made in a form that can be supported and held in an insulating, electrochemically inert, deformable material that is sealed around the outer surface of the coating on the core to prevent leakage of chemicals being sensed. The body also permits sealing quite easily onto access ports on which the sensor housing is mounted. Various connections to the electrode coating can be made quite easily to provide for a unique sensor assembly.

Claims

1. An indicator electrode assembly for sensing an electrochemical condition of a sample, the assembly comprising:

a core of material that is chemically inert to the sample, a sensing portion comprising a coating of an electrochemically sensitive material placed on the core, a conductor electrically connected to the coating, and a body of an electrical insulating, electrochemically inert deformable material partially enveloping the core and the coating and having an opening of size to permit at least a portion of the sensing portion to be exposed by the body.

2. The indicator electrode assembly of claim 1, wherein the core is spherically shaped and is mounted in a part spherical opening in the body.

3. The indicator electrode assembly of claim 2 wherein the core is an insulating ceramic material, and the coating is iridium oxide.

4. The indicator electrode assembly of claim 3 wherein the core is ball shaped.

5. The indicator electrode assembly of claim 4 wherein the core is alumina.

6. The indicator electrode assembly of claim 4 wherein the core is a semi-conductor.

7. The indicator electrode assembly of claim 5 wherein the iridium oxide is sputter deposited onto the core.

8. The indicator electrode assembly of claim 1, wherein the coating extends to a side of the core remote from the opening in the body, and the conductor comprises a conductive polymer in contact with the coating.

9. The indicator electrode assembly of claim 1, and a temperature sensor mounted in a conductive sleeve, and means to hold the conductive sleeve in contact with the coating to form the conductor.

10. The indicator electrode assembly of claim 1 wherein the body of insulating, electromechanically inert deformable material comprises a ferrule having a central bore, and an end portion deformable toward the core and coating of an electrode, the electrode having at least a parts spherical surface that is engaged by he deformable end, the housing over said ferrule having a surface that engages the ferrule to urge the ferrule to deform against the core and coating and means to urge said ferrule against the portion of said housing.

11. The indicator electrode assembly of claim 10 and means supported relative to said housing to urge the electrode in the same direction as the direction of force acting to retain the ferrule.

12. The indicator electrode assembly of claim 11 wherein said means for urging the electrode includes a metal electrical conductor directly engaging the surface of the electrode and being urged against the electrode surface to form an electrical contact.

13. The indicator electrode assembly of claim 1 and an outer layer of an ion sensitive coating over the sensing portion and through which sample material passes to contact the coating.

14. An electrode assembly for indicating a condition of a sample comprising:

a core member having at least a portion thereof forming a part spherical surface;

a sensing portion on said part spherical surface having an exterior part spherical surface, the sensing portion comprising a coating of a selected material for sensing a condition of the sample;

a conductor electrically connected to the coating;

a sealing body engaging a portion of the exterior part spherical surface along a sealing line to define an exposed portion that is exterior of the sealing body; and

said sealing body comprising a chemically inert, nonelectrically conductive deformable material which prevents the sample to be sensed by the exposed portion from leaking past the sensing portion to the conductor.

15. The electrode assembly of claim 14, wherein said body forms a sleeve having a through opening, and one end of said opening having a camming surface defining an exterior thereof, and a housing around the sleeve having a mating interior camming surface, whereby when the sleeve and the housing are urged together so that their camming surfaces engage, the body is forced against the sensing portion in the through opening of the body.

16. The electrode assembly of claim 15 wherein said body comprises a block of an elastomeric material having a part spherical surface therein that mates with the exterior part spherical surface of the coating on the core and forms a seal therewith, and an outer housing for holding said body in position against the coating on the core.

17. The electrode assembly of claim 16 wherein said sensing portion has a cylindrical surface joining the exterior part spherical surface, said cylindrical surface being formed on a tube, and a temperature sensor on the interior of said tube, said tube being made of an insulating material.

18. The electrode assembly of claim 15 wherein said body comprises a ferrule and said housing is tubular and has a central opening, the electrode further comprising a ferrule pusher threadably mounted in said central opening and bearing against said ferrule to urge the camming surfaces together, said ferrule also being tubular, and a sensing portion pusher threadably mounted on the interior of said ferrule pusher and threadable relative to the ferrule pusher to urge the sensing portion in a direction toward the surface of the ferrule.

19. The electrode assembly of claim 18 wherein said sensing portion pusher comprises at least a section of an electrically insulating material, and the conductor directly engaging the coating to form electrical contact therewith.

20. The electrode assembly of claim 14 wherein the core member is an electrical insulator material.

21. The electrode assembly of claim 14 wherein the core member is a semi-conductor.

22. The electrode assembly of claim 16 wherein the coating on the core member is gold and a semi-permeable membrane covers the exposed portion of the sensing portion, the electrode sensing properties of ions passing through the membrane.

23. An indicator electrode for sensing the electrochemical condition of a sample, the indicator electrode comprising:

a core of material that is chemically inert to the sample and having a partially spherical shaped surface, a sensing portion comprising a coating of an electrochemically sensitive material, directly deposited on the the partially spherical shaped surface to form a sensing surface for sensing electrochemical activity and, a conductor electrically connected to the coating.

24. The indicator electrode of claim 23 wherein the core is an insulating ceramic material, and the coating is iridium oxide sputtered on the core.

25. The indicator electrode of claim 24 wherein the core is alumina.

26. The indicator electrode of claim 23 wherein the coating is iridium oxide sputter deposited onto the core.

32. The indicator electrode of claim 23 wherein the coating is a metal oxide.

33. The indicator electrode of claim 23 wherein the core is a semi-conductor.

34. The indicator electrode of claim 23 wherein the core is ball shaped.

35. The indicator electrode of claim 23 wherein the core has an inner cavity.

27. An assembly used to indicate a condition of electrochemical activity of a sample, the assembly comprising;

a sealing body having an opening leading to a cavity;

an electrode having an electrochemically sensitive outer coating wherein a portion of the outer coating is spherical, and wherein the electrode is disposed within the cavity such that a part of the spherical outer coating extends through the opening and is exposed to the sample, the sealing body engaging a portion of the spherical outer coating to make a seal therebetween to prevent the sample from entering the cavity; and

a conductor located within the cavity and electrically connected to the coating.

28. The assembly of claim 27 wherein the sealing body comprises a non-electrically conductive deformable material, and the assembly further comprises means for tightening the seal between the sealing body and the electrode.

29. The assembly of claim 28 and further comprising an outer housing having an opening defining inner camming surfaces, the electrode positioned within the opening with a portion of the electrode extending thereout, and the sealing body positioned between the electrode and the inner camming surfaces, and wherein the means for tightening comprises simultaneously urging the sealing body against the electrode and the inner camming surfaces.

30. The assembly of claim 29 wherein the sealing body comprises a ferrule, the housing is tubular and the means for tightening comprises a ferrule pusher threadably mounted within the housing to urge the sealing body against the electrode and the inner camming surfaces.

31. The assembly of claim 30 and further comprising an electrode pusher threadably mounted on the interior of the ferrule pusher to urge the electrode in a direction toward the ferrule.