Method and system for unobtrusively measuring physical properties in electrochemical processes

• US 5,537,042 A
• Filed: 11/18/1994
• Issued: 07/16/1996
• Est. Priority Date: 11/18/1994
• Status: Expired due to Fees

• Current Assignee: Eldec Corporation (Crane Company)
• Original Assignee: Eldec Corporation (Crane Company)
• Inventors: Van Schalkwijk, Walter A., Green, Jeffrey J., Flagg, Delbert F. Jr., Burreson, Bernard J., Beutler, Jon F., Kromholtz, Gregory A.
• Primary Examiner(s): Wieder, Kenneth A.
• Assistant Examiner(s): BROWN, GLENN WARNER
• Application Number:
  US08/342,385
• Time in Patent Office: 606 Days
• Field of Search: 324/426, 324/427, 324/432, 324/436, 324/437, 324/654, 324/226, 324/234, 324/236, 340/636, 429/10, 429/91, 429/93
• US Class Current: 324/432
• CPC Class Codes: G01R 27/02 Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant by measuring phase angle only G01R25/00
• CPC Class Codes: G01R 27/2658 Cavities, resonators, free space arrangements, reflexion or interference arrangements G01R27/2647 takes precedence; optical methods G01R27/2682
• CPC Class Codes: G01R 31/396 Acquisition or processing of data for testing or for monitoring individual cells or groups of cells within a battery

Abstract

Disclosed is a method and system for unobtrusively measuring physical properties in electrochemical processes occurring in a predefined volume, such as the state of charge in an electrochemical battery. The invention provides for a coil (22) or (42) positioned relative to the predefined volume to minimize the reluctance path between the coil and the electrochemical process, with the winding axis of the coil generally transverse to a surface bounding the predefined volume. In this position, an alternating current is applied to the coil to generate an oscillatory magnetic field. Preferably, the coil includes a core (24) or a backing plate (46) for concentrating the magnetic field in a direction towards the process in the predefined volume. The physical properties are determined based upon a measurement of the electrical complex impedance of the coil, and data correlating the physical properties of the process with the electrical complex impedance of the coil.

Claims

1. A method for measuring the state of charge in an electrochemical battery, the battery having an anode including a first sheet of material, and a cathode including a second sheet of material, comprising the steps of:

(a) providing a coil;

(b) positioning the coil relative to the battery to minimize the reluctance path between the coil and a selected sheet;

(c) orienting the coil so that the winding axis of the coil is generally transverse to the surface of the selected sheet;

(d) applying an alternating current of a first frequency to the coil to generate a first oscillatory magnetic field;

(e) providing a means for concentrating the oscillating magnetic field in a direction towards the selected sheet;

(f) measuring the electrical complex impedance of the coil at the first frequency;

(g) determining the state of charge of the battery based upon the measured electrical complex impedance of the coil by comparing the measured electrical complex impedance of the coil with data correlating the state of charge of the battery with electrical complex impedance of the coil.

2. The method of claim 1, wherein the step of providing a means for concentrating the magnetic field comprises the substep of providing a core for the coil.

3. The method of claim 2, wherein the step of providing a means for concentrating the magnetic field comprises the sub step of providing a backing plate for the coil, wherein the backing plate includes a magnetically permeable material which is poorly conductive.

4. The method of claim 1, further comprising the step of selecting a coil that has a maximum diameter no greater than the width of any of the sheets, and no greater than the length of any of the sheets.

5. A method for measuring the state of charge in an electrochemical battery, the battery having an anode including a first sheet of material, and a cathode including a second sheet of material, comprising the steps of:

(a) providing a coil;

(b) positioning the coil relative to the battery to minimize the reluctance path between the coil and a selected sheet;

(c) orienting the coil so that the winding axis of the coil is generally transverse to the surface of the selected sheet;

(d) applying an alternating current of a first frequency to the coil to generate a first oscillatory magnetic field;

(e) providing a means for concentrating the oscillating magnetic field in a direction towards the selected sheet;

(f) measuring the electrical complex impedance of the coil at the first frequency;

(g) determining the state of charge of the battery based upon the measured electrical complex impedance of the coil;

(h) applying an alternating current at a plurality of frequencies to the coil to generate a plurality of oscillatory magnetic fields; and

(i) measuring the electrical complex impedance of the coil at the plurality of frequencies.

6. The method of claim 5, wherein the step of determining the state of charge of the battery based upon the complex impedance of the coil, comprises the substeps of:

(a) mathematically modeling the coil and at least one chosen sheet based on electrical equivalents; and

(b) using the mathematical model of the coil and the chosen sheet, and the measured electrical complex impedance of the coil at the plurality of frequencies, to determine the permeability and conductivity of the chosen sheet; and

(c) determining the state of charge of the battery based upon the permeability and conductivity of the chosen sheet.

7. A method for measuring the state of charge in an electrochemical battery, the battery having an anode including a first sheet of material, and a cathode including a second sheet of material, comprising the steps of:

(a) providing a coil;

(b) positioning the coil relative to the battery to minimize the reluctance path between the coil and a selected sheet;

(c) orienting the coil so that the winding axis of the coil is generally transverse to the surface of the selected sheet;

(d) applying an alternating current of a first frequency to the coil to generate a first oscillatory magnetic field, and selecting the first frequency to maximize the effect the selected sheet has on the electrical complex impedance of the coil;

(e) providing a means for concentrating the oscillating magnetic field in a direction towards the selected sheet;

(f) measuring the electrical complex impedance of the coil at the first frequency; and

(g) determining the state of charge of the battery based upon the measured electrical complex impedance of the coil.

8. A method, for measuring the state of charge in an electrochemical battery, the battery having an anode including a first sheet of material, and a cathode including a second sheet of material, comprising the steps of:

(a) providing a coil;

(b) positioning the coil relative to the battery to minimize the reluctance path between the coil and a selected sheet;

(c) orienting the coil so that the winding axis of the coil is generally transverse to the surface of the selected sheet;

(d) applying an alternating current of a first frequency to the coil to generate a first oscillatory magnetic field;

(e) providing means for concentrating the oscillating magnetic field in a direction towards the selected sheet;

(f) measuring the electrical complex impedance of the coil at the first frequency; and

(g) determining the state of charge of the battery based upon the measured electrical complex impedance of the coil by;

(i) reducing the measured electrical complex impedance of the coil into first and second component terms;

(ii) making a first initial determination of the state of charge of the battery based upon the first component term;

(iii) making a second initial determination of the state of charge of the battery based upon the second component term; and

(iv) making a final determination of the state of charge of the battery based upon the first and second initial determinations.

9. The method of claim 8, wherein the first component term is the real part of the electrical complex impedance of the coil, and the second component term is the imaginary part of the electrical complex impedance of the coil.

10. A method for measuring a physical parameter of a chemical solution residing in a container, comprising the steps of:

(a) providing a coil;

(b) positioning the coil relative to the container to minimize the reluctance path between the coil and the solution in the container;

(c) orienting the coil so that the winding axis of the coil is generally transverse to the surface of the container;

(d) applying an alternating current to the coil to generate an oscillatory magnetic field;

(e) providing a means for concentrating the first oscillating magnetic field in a direction towards the solution in the container;

(f) measuring the electrical complex impedance of the coil; and

(g) determining the physical parameter of the solution based upon the measured electrical complex impedance of the coil by comparing the measured electrical complex impedance of the coil with data correlating the physical parameter of the chemical solution with electrical complex impedance of the coil.

11. A method for measuring a physical parameter in an electrochemical process occurring within a predefined volume, comprising the steps of:

(a) providing a coil;

(b) positioning the coil relative to the predefined volume to minimize the reluctance path between the coil and the electrochemical process;

(c) orienting the coil so that the winding axis of the coil is generally transverse to a surface bounding the predefined volume;

(d) applying an alternating current at a first frequency to the coil to generate a first oscillatory magnetic field;

(e) providing a means for concentrating the first oscillating magnetic field in a direction towards the electrochemical process;

(f) measuring the electrical complex impedance of the coil at the first frequency; and

(g) determining the physical parameter based upon the measured electrical complex impedance of the coil by comparing the measured electrical complex impedance of the coil with data correlating the physical parameter with electrical complex impedance of the coil.

12. The method of claim 11, wherein the step of providing a means for concentrating the magnetic field comprises the substep of providing a core for the coil.

13. The method of claim 11, wherein the step of providing a means for concentrating the magnetic field comprises the substep of providing a backing plate for the coil, wherein the backing plate includes a magnetically permeable material which is poorly conductive.

14. The method of claim 11, wherein the step of determining the physical parameter based upon the electrical complex impedance of the coil, comprises the substeps of:

(a) reducing the measured complex impedance of the coil into a component term; and

(b) determining the physical parameter based upon the component term.

15. A system for measuring the state of charge in an electrochemical battery, the battery having an anode including a first sheet of material, and a cathode including a second sheet of material, the system comprising:

(a) a coil;

(b) holding means for holding the coil adjacent the battery, and in an orientation so that the winding axis of the coil is generally transverse to the surface of at least one of the sheets;

(c) alternating current means electrically connected to the coil, for applying an alternating current at a first frequency to the coil to generate a first oscillatory magnetic field;

(d) magnetic field concentration means for concentrating the first oscillating magnetic field in a direction towards the sheets;

(e) measuring means electrically connected to the coil, for measuring the electrical complex impedance of the coil at the first frequency; and

data processing means for receiving the measured electrical complex impedance of the coil; and

(f) determining the state of charge of the battery, wherein the data processing means determines the state of charge of the battery by comparing the measured electrical complex impedance of the coil with data correlating state of charge of the battery with electrical complex impedance of the coil.

16. The system of claim 15, wherein the magnetic field concentration means comprises a magnetically permeable core having at least a part of the coil encircled by the core.

17. The system of claim 16, wherein the core includes:

(a) a base;

(b) a nose portion extending from the base; and

(c) walls extending from the base a spaced distance from the nose portion, wherein the coil encircles at least a part of the nose portion, and at least a part of the coil is encircled by the walls.

18. The system of claim 15, wherein the magnetic field concentration means includes a backing plate connected to the coil opposite the battery, the backing plate having a magnetically permeable material which is poorly conductive.

19. The system of claim 15, wherein the coil has a maximum diameter no greater than the width of any of the sheets, and no greater than the length of any of the sheets.

20. A system for measuring the state of charge in an electrochemical battery, the battery having an anode including a first sheet of materials, and a cathode including a second sheet of material, the system comprising;

(a) a coil;

(b) holding means for holding the coil adjacent the battery, and in an orientation so that the winding axis of the coil is generally transverse to the surface of at least one of the sheets;

(c) alternating current means electrically connected to the coil for applying an alternating current at a first frequency to the coil to generate a first oscillatory magnetic field;

(d) magnetic field concentration means for concentrating the first oscillating magnetic field in a direction towards the sheets;

(e) measuring means electrically connected to the coil, for measuring the electrical complex impedance of the coil at the first frequency; and

(f) data processing means for receiving the measured electrical complex impedance of the coil, and determining the state of charge of the battery, wherein the data processing means determines the state of charge of the battery based upon the electrical complex impedance of the coil by;

(i) reducing the measured complex impedance of the coil into first and second component terms;

(ii) making a first initial determination of the state of charge of the battery based upon the first component term;

(iii) making a second initial determination of the state of charge of the battery based upon the second component term; and

(iv) making a final determination of the state of charge of the battery based upon the first and second initial determinations.

21. The system of claim 20, wherein the first component term is the real part of the electrical complex impedance of the coil, and the second component term is the imaginary part of the electrical complex impedance of the coil.