Capacitively coupled electrode system with variable capacitance for sensing potentials at the surface of tissue

• US 20030036691A1
• Filed: 10/07/2002
• Published: 02/20/2003
• Est. Priority Date: 08/10/2000
• Status: Abandoned Application

• Current Assignee: Gaetan Chevalier, Thomas G. Stanaland
• Original Assignee: Gaetan Chevalier, Thomas G. Stanaland
• Inventors: Chevalier, Gaetan, Stanaland, Thomas G.
• Application Number:
  US10/266,648
• Publication Number:
  US 20030036691A1
• Time in Patent Office: Days
• US Class Current: 600/372
• CPC Class Codes: A61B 5/0531 Measuring skin impedance
• CPC Class Codes: A61B 5/25 Bioelectric electrodes therefor
• CPC Class Codes: A61B 5/277 Capacitive electrodes
• CPC Class Codes: A61B 5/291 for electroencephalography [EEG]

Abstract

An electrical activity sensor for sensing and reproducing electrical potentials at the surface of a test item such as a human being has an electrode configured to be capacitively coupled to the test item and a variable capacitance coupled to the electrode. The capacitively coupled electrode and the variable capacitance cooperate to mitigate a need for conductively coupling the electrode to the test subject.

Claims

1. An electrical activity sensor comprising:

an electrode configured to be capacitively coupled to a test item;

a variable capacitance coupled to the electrode; and

wherein the capacitively coupled electrode and the variable capacitance cooperate to mitigate a need for conductively coupling an electrode to the test item.

2. The electrical activity sensor as recited in claim 1, wherein the electrode comprises:

a conductive member; and

a dielectric member configured to inhibit contact of the conductive member with the test item.

3. The electrical activity sensor as recited in claim 1, wherein the electrode comprises:

a conductive member generally configured as a disk; and

a dielectric cover substantially surrounding the conductive member.

4. The electrode system as recited in claim 1, wherein the electrode is configured to be capacitively coupled to living tissue.

5. The electrode system as recited in claim 1, wherein the electrode is configured to be capacitively coupled to a mammal.

6. The electrode system as recited in claim 1, wherein the electrode is configured to be capacitively coupled to a human being.

7. The electrical activity sensor as recited in claim 1, wherein the electrode comprises:

a copper member generally configured as a disk;

a dielectric cover substantially surrounding the conductive member;

a cap comprised of insulator cooperating with the dielectric cover to generally enclose the copper member; and

a conductive lead coupled to the copper member and extending through the cap.

8. The electrical activity sensor as recited in claim 1, wherein the variable capacitance comprises an electro-mechanical device.

9. The electrical activity sensor as recited in claim 1, wherein the variable capacitance comprises:

at least two spaced apart conductors; and

a position controller for varying a position of the conductors with respect to one another.

10. The electrical activity sensor as recited in claim 1, wherein the variable capacitance comprises:

two spaced apart conductive plates; and

a piezoelectric element disposed intermediate the two spaced apart conductive plates such that application of a voltage to the piezoelectric crystal effects movement of the two spaced apart conductive plates.

11. The electrical activity sensor as recited in claim 1, wherein the variable capacitance comprises:

a frequency source;

two spaced apart conductive plates; and

a piezoelectric element disposed intermediate the two spaced apart conductive plates and coupled to the frequency source such that application of a voltage to the piezoelectric element from the frequency source effects movement of the two spaced apart conductive plates.

12. The electrical activity sensor as recited in claim 1, wherein the variable capacitance comprises:

a frequency source configured to provide a generally predetermined frequency output;

two spaced apart conductive plates; and

a piezoelectric element disposed intermediate the two spaced apart conductive plates and coupled to the frequency source such that application of a voltage to the piezoelectric crystal from the frequency source effects movement of the two spaced apart conductive plates.

13. The electrical activity sensor as recited in claim 1, wherein the variable capacitance comprises:

a frequency source configured to provide a generally random frequency output;

two spaced apart conductive plates; and

a piezoelectric element disposed intermediate the two spaced apart conductive plates and coupled to the frequency source such that application of a voltage to the piezoelectric crystal from the frequency source effects movement of the two spaced apart conductive plates.

14. The electrical activity sensor as recited in claim 1, wherein the variable capacitance comprises:

frequency source grounded to a metal enclosure;

two spaced apart conductive plates; and

a piezoelectric element disposed intermediate the two spaced apart conductive plates and coupled to the frequency source such that application of a voltage to the piezoelectric crystal from the frequency source effects movement of the two spaced apart conductive plates.

15. The electrical activity sensor as recited in claim 1, further comprising a detection circuit coupled to receive an output of the capacitively coupled electrode and to condition the output of the capacitively coupled electrode.

16. The electrical activity sensor as recited in claim 1, further comprising a detection circuit coupled to receive an output of the capacitively coupled electrode, the detection circuit comprising a calibrated resistance.

17. The electrical activity sensor as recited in claim 1, wherein further comprising a detection circuit coupled to receive an output of the capacitively coupled electrode, the detection circuit being configured so as to provide an output suitable for input to a differential amplifier.

18. The electrical activity sensor as recited in claim 1, further comprising:

a detection circuit coupled to condition an output of the capacitively coupled electrode; and

an amplifier coupled to amplify an output of the detection circuit.

19. The electrical activity sensor as recited in claim 1, further comprising:

a detection circuit coupled to condition an output of the capacitively coupled electrode; and

a differential amplifier coupled to amplify an output of the detection circuit.

20. The electrical activity sensor as recited in claim 1, further comprising:

a detection circuit coupled to condition an output of the capacitively coupled electrode; and

a variable gain amplifier coupled to amplify an output of the detection circuit.

21. The electrical activity sensor as recited in claim 1, further comprising:

a detection circuit coupled to condition an output of the capacitively coupled electrode; and

a variable gain amplifier coupled to amplify an output of the detection circuit in a manner which facilitates provision of an output that generally mimics an output of at least one of an electroencephalograph electrode, an electrocardiograph electrode, an electromyograph electrode and a galvanic skin response electrode.

22. The electrical activity sensor as recited in claim 1, further comprising:

a detection circuit coupled to condition an output of the capacitively coupled electrode;

an amplifier coupled to amplify an output of the detection circuit; and

an output circuit coupled to the amplifier to define an output impedance.

23. The electrical activity sensor as recited in claim 1, further comprising:

a detection circuit coupled to condition an output of the capacitively coupled electrode;

an amplifier coupled to amplify an output of the detection circuit; and

an output circuit coupled to the amplifier to define an output impedance which is suitable for providing a signal to an electroencephalograph.

24. The electrical activity sensor as recited in claim 1, further comprising:

a detection circuit coupled to condition an output of the capacitively coupled electrode;

an amplifier coupled to amplify an output of the detection circuit; and

an output circuit coupled to the amplifier to define an output impedance which is suitable for providing a signal to an electromyograph.

25. The electrical activity sensor as recited in claim 1, further comprising:

a detection circuit coupled to condition an output of the capacitively coupled electrode;

an amplifier coupled to amplify an output of the detection circuit; and

an output circuit coupled to the amplifier to define an output impedance which is suitable for providing a signal to an electrocardiograph.

26. The electrical activity sensor as recited in claim 1, further comprising:

a detection circuit coupled to condition an output of the capacitively coupled electrode;

an amplifier coupled to amplify an output of the detection circuit; and

an output circuit coupled to the amplifier to define an output impedance which is suitable for providing a signal to a galvanic skin response monitor.

27. The electrical activity sensor as recited in claim 1, further comprising a reference electrode coupled to the detection circuit.

28. The electrical activity sensor as recited in claim 1, further comprising a ground electrode coupled to a metal enclosure.

29. The electrical activity sensor as recited in claim 1, further comprising a reference electrode coupled to the detection circuit and a ground electrode coupled to a metal enclosure.

30. An electrical activity sensor comprising an electrode coupled to a variable capacitance device.

31. A method for characterizing electrical activity of an object being monitored, the method comprising using displacement current to sense electrical activity within a test item.

32. The method as recited in claim 31, wherein using displacement current to sense electrical activity comprises capacitively coupling an electrode to the object being tested.

33. The method as recited in claim 31, wherein using displacement current to sense electrical activity comprises capacitively coupling an electrode to the object being tested and varying a capacitance of a capacitor coupled to the electrode.

34. The method as recited in claim 31, wherein using displacement current to sense electrical activity comprises capacitively coupling an electrode to the object being tested and using a frequency source to vary a capacitance of a capacitor coupled to the electrode.

35. The method as recited in claim 31, wherein using displacement current to sense electrical activity comprises capacitively coupling an electrode to the object being tested and using a frequency source to vary a capacitance of a capacitor coupled to the electrode, the capacitance of the capacitor being varied in a predetermined manner.

36. The method as recited in claim 31, wherein using displacement current to sense electrical activity comprises capacitively coupling an electrode to the object being tested and using a frequency source to vary a capacitance of a capacitor coupled to the electrode, the capacitance of the capacitor being varied in a random manner.