WO1989002592A1 - Tip construction of a reference electrode - Google Patents

Tip construction of a reference electrode Download PDF

Info

Publication number
WO1989002592A1
WO1989002592A1 PCT/FI1988/000143 FI8800143W WO8902592A1 WO 1989002592 A1 WO1989002592 A1 WO 1989002592A1 FI 8800143 W FI8800143 W FI 8800143W WO 8902592 A1 WO8902592 A1 WO 8902592A1
Authority
WO
WIPO (PCT)
Prior art keywords
body tube
plug
pressure
construction
solution
Prior art date
Application number
PCT/FI1988/000143
Other languages
French (fr)
Inventor
Pertti Aaltonen
Lauri Selin
Original Assignee
Valtion Teknillinen Tutkimuskeskus
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Valtion Teknillinen Tutkimuskeskus filed Critical Valtion Teknillinen Tutkimuskeskus
Publication of WO1989002592A1 publication Critical patent/WO1989002592A1/en

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
    • G01N27/28—Electrolytic cell components
    • G01N27/30—Electrodes, e.g. test electrodes; Half-cells
    • G01N27/301—Reference electrodes

Definitions

  • the present invention concerns a tip construction for a reference electrode as defined in the preamble to Claim 1.
  • Reference electrodes used in electro-chemical measurements, and tip constructions of these, are known in the art e.g. through the Finnish patent application No. 841141 and through U.S. Patent No. 4,282,081.
  • the tip of the electrode comprises a porous plug, e.g. a plug of zirconium oxide. The plug is comparatively tightly fitted on the end of the electrode,, preventing the solutions inside and outside the electrode from becoming mixed, yet enabling electric contact between said solutions.
  • the object of the invention is to eliminate the drawbacks mentioned. It is a particular aim of the invention to provide a novel reference electrode tip construction which is insensitive to pressure fluctuations, therefore maintaining equally good tightness all the time.
  • the reference electrode tip construction of the invention comprises a pressure-resistant body tube which is pressure-tightly closed at its measuring end.
  • the end of the tube may for instance be welded closed, or it may comprise a threaded plug which completely inhibits transfer into the tube of the pressure which is ambient to the tube.
  • the tip construction comprises a porous plug connecting electrically the exterior system, which is being measured, and the solution within said body tube, this plug being located transversally to the body tube, at a distance from the end of the body tube so that the pressure acting outside the tube acts on said plug from opposite sides on different sides of the tube, so that the resultant force due to the pressure which acts on the plug is zero.
  • the plug is a rod extending from surface to surface of the body tube, across its axis therethrough, its central part communicating with the solution in the body tube and its ends in the vicinity of the surface of the body tube so that the external pressure acts on the rods only on their ends having equal area.
  • the rod is then subjected to two pressure-induced forces, which however, being opposed in direction and exactly equal in magnitude, cancel each other's effects, whereby the rod remains stationary independent of the height of pressure.
  • a sealing plug of suitable insulating material there is provided within the body tube, a sealing plug of suitable insulating material, the rod being disposed to pass therethrough.
  • a cavity within said sealing plug freely communicating with the solution in the body tube, and the body tube has apertures at the ends of the rods. Therefore the rods themselves are not in direct contact with the body tube: they are supported by and sealed against the sealing plug of insulating material by which the solution in the body tube has been sealed to be separated from the space external to the tube.
  • the tip construction comprises at least two separate porous plugs disposed as described in the foregoing.
  • the shape of the plug is not confined in the invention to be exclusively rod-like: its shape may be chosen with comparatively great freedom.
  • An essential feature thereof are those surfaces of the plug which are in contact with the external pressure, both said surfaces being so disposed that the simultaneous forces acting on the surfaces cancel each other, whereby on the plugs act no forces which would tend to move them.
  • the forces acting on the plug are advantageously perpendicular against the axis of the body tube, whereby no stressing forces act on any other sealing parts of the tip construction either.
  • FIG. 1 presents a sectional view of a tip construction according to the invention
  • Fig. 2 presents another sectional view of the construction of Fig. 1,
  • FIG. 3 presents a third view of the same tip construction.
  • a reference electrode according to the invention depicted in the drawing, comprises a pressure-resistant body tube 1 e.g. of steel, its end 4 being pressure-tightly stoppered with a threaded plug 5.
  • the inner surface of the body tube includes an insulation 12 which insulates the solution 2 in the tube and the tube itself.
  • the insulation ends at a distance from the end 4 of the tube, and at this point there has been placed in the tube a sealing plug 8 partly supported by the insulation 12 and partly on the outside thereof by the body tube, within said plug being provided a solution cavity 9 which communicates freely with the interior space of the body tube.
  • This plug 8 is tightened and sealed in place against the insulation 12 and the body tube 1 by the aid of a compression spring 11, located between the sealing plug and the stopper 5.
  • the spring 11 presses the plug 8 into position.
  • the tip construction furthermore comprises, placed in the sealing plug 8, two porous rods 6 extending therethrough from surface to surface, these rods passing through the centre of the sealing plug with round cross section and being perpendicular against the axis of the sealing plug, and at the same time against that of the body tube 1.
  • the rods are joined with tight sealing to the sealing plug 8 of insulating material, said plug consisting e.g. of Teflon or of another suitable material.
  • the body tube 1 has apertures 10 at the ends of the rods 6, whereby the ends of the rods are in free contact with the space and pressure on the outside of the body tube.
  • the rods 6 being constituted by a brittle membrane, such as zirconium oxide for instance, the rods will electrically connect the space outside the body tube and the solution 2 inside the body tube, as they pass through the solution cavity 9 and open through the aperture 10 in the body tube 1, to the exterior space. At the same time, however, the rods preclude direct communication between the solution 2 and the exterior space of the tube and material flows between said spaces.
  • the tightness and good operation of the tip construction here disclosed is based on the circumstance that the pressure external to the body tube cannot damage the seals and brittle membranes of the construction because the brittle rods have been disposed so that the pressure acts on them only in a direction at right angles to the body tube, and only on the ends of the rods, which have equal surface areas.
  • the pressure external to the body tube cannot damage the seals and brittle membranes of the construction because the brittle rods have been disposed so that the pressure acts on them only in a direction at right angles to the body tube, and only on the ends of the rods, which have equal surface areas.
  • two forces with equal absolute magnitude but completely opposed in direction and which cancel each other whereby no forces whatsoever tending to move the rod act on the rod.
  • no forces whatsoever occur there which are longitudinal with reference to the tube and which might impair the tight sealing of the tip construction. Therefore the construction retains its tightness in any conceivable pressure conditions.

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  • Chemical & Material Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Health & Medical Sciences (AREA)
  • Physics & Mathematics (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Molecular Biology (AREA)
  • Analytical Chemistry (AREA)
  • Biochemistry (AREA)
  • General Health & Medical Sciences (AREA)
  • General Physics & Mathematics (AREA)
  • Immunology (AREA)
  • Pathology (AREA)
  • Measuring Fluid Pressure (AREA)
  • Building Environments (AREA)

Abstract

The invention concerns a tip construction for a reference electrode comprising a pressure-resistant body tube (1), and a porous plug (3) electrically connecting the system that is being measured and the solution (2) in said body tube. As taught by the invention, the body tube (1) is pressure-tightly closed at its end (4) and the plug (3) is located transversally to the body tube so that the pressure in the system acts on the plug from opposite sides so that the resultant force due to pressure acting on the plug is zero.

Description

TIP CONSTRUCTION OF A REFERENCE ELECTRODE
The present invention concerns a tip construction for a reference electrode as defined in the preamble to Claim 1. Reference electrodes used in electro-chemical measurements, and tip constructions of these, are known in the art e.g. through the Finnish patent application No. 841141 and through U.S. Patent No. 4,282,081. In these references the tip of the electrode comprises a porous plug, e.g. a plug of zirconium oxide. The plug is comparatively tightly fitted on the end of the electrode,, preventing the solutions inside and outside the electrode from becoming mixed, yet enabling electric contact between said solutions.
However, drawbacks are encountered when using reference electrodes of this kind in systems under pressure, particularly in very high pressures. When the porous plug is subjected to high pressure, it tends to move along with the pressure and to push into the electrode. When the pressures abates again, the plug is pushed outward, and if the plug is not damaged at once by effect of the high pressure, it will certainly before long lose its tight fit, as a result of which the electrode no longer operates in desired manner.
The object of the invention is to eliminate the drawbacks mentioned. It is a particular aim of the invention to provide a novel reference electrode tip construction which is insensitive to pressure fluctuations, therefore maintaining equally good tightness all the time.
Regarding the features which are characteristic of the invention, reference is made to the claims section. The reference electrode tip construction of the invention comprises a pressure-resistant body tube which is pressure-tightly closed at its measuring end. The end of the tube may for instance be welded closed, or it may comprise a threaded plug which completely inhibits transfer into the tube of the pressure which is ambient to the tube. Furthermore, the tip construction comprises a porous plug connecting electrically the exterior system, which is being measured, and the solution within said body tube, this plug being located transversally to the body tube, at a distance from the end of the body tube so that the pressure acting outside the tube acts on said plug from opposite sides on different sides of the tube, so that the resultant force due to the pressure which acts on the plug is zero.
Advantageously, the plug is a rod extending from surface to surface of the body tube, across its axis therethrough, its central part communicating with the solution in the body tube and its ends in the vicinity of the surface of the body tube so that the external pressure acts on the rods only on their ends having equal area. The rod is then subjected to two pressure-induced forces, which however, being opposed in direction and exactly equal in magnitude, cancel each other's effects, whereby the rod remains stationary independent of the height of pressure.
Advantageously, there is provided within the body tube, a sealing plug of suitable insulating material, the rod being disposed to pass therethrough. There is a cavity within said sealing plug, freely communicating with the solution in the body tube, and the body tube has apertures at the ends of the rods. Therefore the rods themselves are not in direct contact with the body tube: they are supported by and sealed against the sealing plug of insulating material by which the solution in the body tube has been sealed to be separated from the space external to the tube.
In an embodiment of the invention the tip construction comprises at least two separate porous plugs disposed as described in the foregoing.However, the shape of the plug is not confined in the invention to be exclusively rod-like: its shape may be chosen with comparatively great freedom. An essential feature thereof are those surfaces of the plug which are in contact with the external pressure, both said surfaces being so disposed that the simultaneous forces acting on the surfaces cancel each other, whereby on the plugs act no forces which would tend to move them. Hereat, the forces acting on the plug are advantageously perpendicular against the axis of the body tube, whereby no stressing forces act on any other sealing parts of the tip construction either. The advantage of the invention over the state of art is insensitivity of the tip construction even under high pressure and in the presence of pressure fluctuations, whereby the sealing problems encountered in existing tip construction have all been successfully eliminated.
In the following, the invention is described in detail, referring to the attached drawing, wherein:- Fig. 1 presents a sectional view of a tip construction according to the invention,
Fig. 2 presents another sectional view of the construction of Fig. 1,
Fig. 3 presents a third view of the same tip construction. A reference electrode according to the invention, depicted in the drawing, comprises a pressure-resistant body tube 1 e.g. of steel, its end 4 being pressure-tightly stoppered with a threaded plug 5. The inner surface of the body tube includes an insulation 12 which insulates the solution 2 in the tube and the tube itself. The insulation ends at a distance from the end 4 of the tube, and at this point there has been placed in the tube a sealing plug 8 partly supported by the insulation 12 and partly on the outside thereof by the body tube, within said plug being provided a solution cavity 9 which communicates freely with the interior space of the body tube. This plug 8 is tightened and sealed in place against the insulation 12 and the body tube 1 by the aid of a compression spring 11, located between the sealing plug and the stopper 5. Thus when the stopper 5 is screwed in its place the spring 11 presses the plug 8 into position.
The tip construction furthermore comprises, placed in the sealing plug 8, two porous rods 6 extending therethrough from surface to surface, these rods passing through the centre of the sealing plug with round cross section and being perpendicular against the axis of the sealing plug, and at the same time against that of the body tube 1. The rods are joined with tight sealing to the sealing plug 8 of insulating material, said plug consisting e.g. of Teflon or of another suitable material. The body tube 1 has apertures 10 at the ends of the rods 6, whereby the ends of the rods are in free contact with the space and pressure on the outside of the body tube.
The rods 6 being constituted by a brittle membrane, such as zirconium oxide for instance, the rods will electrically connect the space outside the body tube and the solution 2 inside the body tube, as they pass through the solution cavity 9 and open through the aperture 10 in the body tube 1, to the exterior space. At the same time, however, the rods preclude direct communication between the solution 2 and the exterior space of the tube and material flows between said spaces.
The tightness and good operation of the tip construction here disclosed is based on the circumstance that the pressure external to the body tube cannot damage the seals and brittle membranes of the construction because the brittle rods have been disposed so that the pressure acts on them only in a direction at right angles to the body tube, and only on the ends of the rods, which have equal surface areas. Hereby on one rod act two forces with equal absolute magnitude but completely opposed in direction and which cancel each other, whereby no forces whatsoever tending to move the rod act on the rod. Likewise, since moreover the forces acting on any one of the sealing elements and rods within the body tube are perpendicular against the axis of the body tube, no forces whatsoever occur there which are longitudinal with reference to the tube and which might impair the tight sealing of the tip construction. Therefore the construction retains its tightness in any conceivable pressure conditions.
The embodiment here presented is meant to illustrate the invention, without in any way restricting the invention. of which its various embodiments may vary within the scope of the inventive idea delimited by the claims.

Claims

1. A tip construction for a reference electrode, for use in pressurized systems, comprising a pressure-resistant body tube (1), and a porous plug (3) electrically connecting the system that is being measured and the solution (2) in said body tube, characterized in that the body tube (1) is pressure-tightly closed at its end (4) and the plug (3) is located transversally to the body tube so that the pressure in the system acts on the plug from opposite sides so that the resultant force due to pressure acting on the plug is zero.
2. Construction according to claim 1, characterized in that the end (4) of the body tube (1) consists of a pressure-tightly closable cover , for instance a threaded stopper (5).
3. Construction according to claim 1 or 2, characterized in that the plug (3) is a rod (6) transversal to the body tube (1) in contact with the pressurized system by its ends only, and its central part (7) communicating with the solution (2) within the body tube.
4. Construction according to any one of claims 1-3, characterized in that the construction comprises within the body tube (1) a sealing plug (8) of insulating material, said plug having aaa solution cavity (9) opening into the body tube and closed at the other end, the porous plug (3) being disposed to extend through said cavity so that the ends of the plug are through apertures (10) in the body tube in contact with the pressurized system.
5. Construction according to claim 4, characterized in that between the threaded stopper (5) and the sealing plug
(8) belongs a compression spring (11) for sealing the sealing plug against the body tube (11).
6. Construction according to any one of claims 1-5, characterized in that the construction comprises at least two porous plugs (3) electrically connecting the pressurized system and the solution (2) in the body tube (1).
PCT/FI1988/000143 1987-09-08 1988-09-07 Tip construction of a reference electrode WO1989002592A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FI873885 1987-09-08
FI873885A FI81678C (en) 1987-09-08 1987-09-08 SPETSSTRUKTUR FOER EN REFERENSELEKTROD.

Publications (1)

Publication Number Publication Date
WO1989002592A1 true WO1989002592A1 (en) 1989-03-23

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PCT/FI1988/000143 WO1989002592A1 (en) 1987-09-08 1988-09-07 Tip construction of a reference electrode

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AU (1) AU2303088A (en)
FI (1) FI81678C (en)
WO (1) WO1989002592A1 (en)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE4035447A1 (en) * 1990-10-29 1992-04-30 Forsch Kurt Schwabe Meinsberg Pressure-compensating electrode holder - esp. for potentiometric measuring systems and electrochemical gas sensors
WO1995005597A1 (en) * 1993-08-18 1995-02-23 Valtion Teknillinen Tutkimuskeskus Reference electrode
FR2816057A1 (en) * 2000-10-31 2002-05-03 Schott Glas Electrochemical sensor, for measurements during chemical/biological processes, has tubular glass housing with inner chamber for electrode and concentric outer chamber with reference electrode
WO2015093563A1 (en) * 2013-12-18 2015-06-25 東亜ディーケーケー株式会社 Electrode unit and liquid junction member

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4282081A (en) * 1980-07-10 1981-08-04 Graphic Controls Corp. Double junction reference electrode
US4462872A (en) * 1981-08-21 1984-07-31 Westinghouse Electric Corp. Method of operating a gas analyzer and solid electrolyte gas sensing apparatus
EP0215178A1 (en) * 1985-09-16 1987-03-25 Valtion Teknillinen Tutkimuskeskus A reference electrode

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4282081A (en) * 1980-07-10 1981-08-04 Graphic Controls Corp. Double junction reference electrode
US4462872A (en) * 1981-08-21 1984-07-31 Westinghouse Electric Corp. Method of operating a gas analyzer and solid electrolyte gas sensing apparatus
EP0215178A1 (en) * 1985-09-16 1987-03-25 Valtion Teknillinen Tutkimuskeskus A reference electrode

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE4035447A1 (en) * 1990-10-29 1992-04-30 Forsch Kurt Schwabe Meinsberg Pressure-compensating electrode holder - esp. for potentiometric measuring systems and electrochemical gas sensors
DE4035447C2 (en) * 1990-10-29 1999-07-01 Kurt Schwabe Inst Fuer Mes Und Electrode holder for pressure compensation on electrochemical measuring systems
WO1995005597A1 (en) * 1993-08-18 1995-02-23 Valtion Teknillinen Tutkimuskeskus Reference electrode
FR2816057A1 (en) * 2000-10-31 2002-05-03 Schott Glas Electrochemical sensor, for measurements during chemical/biological processes, has tubular glass housing with inner chamber for electrode and concentric outer chamber with reference electrode
WO2015093563A1 (en) * 2013-12-18 2015-06-25 東亜ディーケーケー株式会社 Electrode unit and liquid junction member
JPWO2015093563A1 (en) * 2013-12-18 2017-03-23 東亜ディーケーケー株式会社 Electrode body and liquid junction member

Also Published As

Publication number Publication date
FI873885A (en) 1989-03-09
FI873885A0 (en) 1987-09-08
FI81678B (en) 1990-07-31
AU2303088A (en) 1989-04-17
FI81678C (en) 1990-11-12

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