CAPACITOR FOR SENSING CONTAMINATED OIL

• US 3,876,916 A
• Filed: 01/08/1973
• Issued: 04/08/1975
• Est. Priority Date: 01/08/1973
• Status: Expired due to Term

• Current Assignee: Donald S. Stoakes
• Original Assignee: Donald S. Stoakes
• Inventors: Stoakes, Donald S.
• Primary Examiner(s): Goldberg, E. A.
• Application Number:
  US05/321,912
• Time in Patent Office: 820 Days
• Field of Search: 317/246,247,248,249R 324/61R,60
• US Class Current: 361/280
• CPC Class Codes: H01G 4/04 Liquid dielectrics

Abstract

Apparatus to determine the dielectric characteristics of a fluid dielectric material including a rigid mounting with a planar mounting surface, a base electrode on a stem secured to the mounting surface and having a broad disc-like portion at one end of the stem and defining a flat electrode face, a ring electrode concentric with the flat face of the base electrode and having an annular wafer-like shape and a mounting projection extending from the outer edge of the wafer-like ring electrode to the planar surface of the rigid mounting and affixed thereto, and a solid insulating media between the base and ring electrodes and forming the remainder of a container wall adjacent the electrodes, the insulating media being formed of a stable low dielectric material which is substantially insensitive to temperature changes.

Claims

1. A sensor for determining the dielectric characteristics of a fluid medium, comprising:

means defining a rigid mounting lying in a plane, a rigid metallic base electrode having a generally flat electrode face lying substantially parallel to said plane and also having an annular edge at the periphery of the face, said base electrode being secured to said rigid mounting, a rigid ring electrode of the same material as the base electrode and spaced from the base electrode, the ring electrode having an inwardly facing annular electrode face conforming to the size and shape and orientation of the annular edge of the base electrode face, said annular electrode face lying substantially perpendicular to the flat face of the base electrode and having an annular end edge adjacent the flat electrode face and uniformly spaced from the flat electrode face around the periphery thereof, said ring electrode having a width, in a direction outwardly from the annular electrode face, equal to the distance from the center of the flat electrode face to the annular edge thereof, said ring electrode also being secured to said rigid mounting, and fluid sealing insulator means disposed between the base and ring electrodes and closing the space between the annular edges of the electrodes, the insulator means being formed of a solid insulating low dielectric material with characteristics of minimum change of dielectric constant in response to changes in temperature, and said insulating material having strength characteristics considerably weaker than the material of the electrodes to allow limited relative movement between the electrodes during temperature induced expansion and contraction, and said insulating means cooperating with the electrodes in defining an open ended fluid medium-confining chamber with the base electrode forming one end of the chamber and the ring electrode forming a portion of the peripheral wall of the chamber.

2. The sensor according to claim 1 and the area of the annular electrode face being substantially equal to the area of the flat electrode face.

3. The sensor according to claim 2 and the area of the flat electrode face being at least as large as the area of the annular electrode face.

4. The sensor according to claim 2 and the flat electrode face of the base electrode being circular, and said annular electrode face also being circular.

5. The sensor according to claim 2 and the base electrode having a mounting stem extending toward and secured to the rigid mounting and having a thickness significantly less than the distance across the flat electrode face.

6. The sensor according to claim 2 and the ring electrode being substantially flat and lying substantially parallel with the flat electrode face of the base electrode.

7. The sensor according to claim 6 and said ring electrode having a mounting projection at the outer periphery of the electrode and extending to said rigid mounting.

8. The sensor according to claim 7 and said mounting projection comprising a cylindrical wall formed integrally of and in one piece with the flat portion of the ring electrode.

9. The sensor according to claim 7 and the base electrode having a mounting stem extending to said rigid mounting and having a thickness significantly less than the distance across the flat electrode face, the space between the stem of the base electrode and the mounting projection of the ring electrode being filled with insulating medium including a portion of said fluid sealing insulator means.

10. The sensor according to claim 1 wherein the sensor is oriented to position the open-ended chamber in upright position with the base electrode forming the bottom end of the chamber, and insulating means defining a peripheral wall above the ring electrode to extend the chamber upwardly and facilitate confining an increased depth of the fluid medium.

11. The sensor according to claim 1 and a housing having a flow passage therethrough and through which said fluid medium may flow, said housing embracing the sensor and providing open flow communication between said passage and said open-ended fluid medium confining chamber for renewing the fluid medium in the chamber with the fluid medium from the passage.

12. The sensor according to claim 1 and the base electrode having a beveled side wall adjacent said annular edge, said beveled side wall facing obliquely away from the ring electrode.

13. The sensor according to claim 1 and said base electrode being movable toward and away from the ring electrode to vary the spacing therebetween and to vary the capacitance of the sensor.

14. The sensor according to claim 13 and said base electrode having a disc portion defining said flat electrode face and also having a threaded stem extending to and being threaded into the rigid mounting to facilitate adjustment of the base electrode relative to the ring electrode.

15. A sensor for determining the dielectric characteristics of a fluid medium, comprising:

means defining a rigid mounting lying in a plane, a rigid metallic base electrode having a generally flat electrode face lying substantially parallel to said plane and also having an annular edge at the periphery of the face, said base electrode engaging and being secured to said rigid mounting at the plane, a rigid ring electrode of the same material as the base electrode and spaced from the base electrode, the ring electrode having an inwardly facing annular electrode face conforming to the size and shape and orientation of the annular electrode of the base electrode face, said annular electrode face lying substantially perpendicular to the flat face of the base electrode and said annular electrode face being uniformly spaced from the flat electrode around the periphery thereof;

said ring electrode having a thickness in a direction across the annular electrode face, and also having a width in a direction outwardly from the annular face of such magnitudes as to cause the area of the annular electrode face to change corresponding to the change of the base electrode face with change in temperature and proportionately to the change in spacing between the electrode faces of the base and ring electrodes as the electrodes extend from or contract toward the reference plane of the rigid mounting in response to such change in temperature, and fluid sealing insulator means disposed between the base and ring electrodes and closing thespace between the peripheries of the electrodes, the insulator means being formed of a solid insulating low dielectric material with characteristics of minimum change of dielectric constant in response to changes in temperature, and said insulating material having strength characteristics considerably weaker than the material of the electrodes to allow limited relative movement between the electrodes during temperature induced expansion and contraction, and said insulating means cooperating with the electrodes in defining an open ended fluid medium-confining chamber with the base electrode forming one end of the chamber and the ring electrode forming a portion of the peripheral wall of the chamber.

16. The sensor according to claim 15 and said annular electrode face having an area at least as small as the area of the flat electrode face of the base electrode.