DRY CONTACT ELECTRODE WITH AMPLIFIER FOR PHYSIOLOGICAL SIGNALS

• US 3,744,482 A
• Filed: 06/29/1971
• Issued: 07/10/1973
• Est. Priority Date: 06/29/1971
• Status: Expired due to Term

• Current Assignee: Donald P. Powell, William M. Kaufman
• Original Assignee: Donald P. Powell, William M. Kaufman
• Inventors: Kaufman, William M., Powell, Donald P.
• Primary Examiner(s): Kamm, William E.
• Application Number:
  US05/158,040
• Time in Patent Office: 742 Days
• Field of Search: 128/2.6B,2.6E,2.6R,2.1E,DIG.4 330/109
• US Class Current: 600/372
• CPC Class Codes: A61B 5/30 Input circuits therefor
• CPC Class Codes: A61B 5/302 for capacitive or ionised electrodes, e.g. metal-oxide-semiconductor field-effect transistors [MOSFET]

Abstract

An electrode and amplification circuitry connected thereto mounted within a housing for capacitively coupling physiologically produced potential along the skin surface of the body to the amplification circuitry without undesirable direct current shifts in potential and with rapid recovery from saturation due to a transient by means of a Zener diode or leakresistor circuit arrangement in the amplification circuitry.

Claims

1. A dry contact electrode for receiving physiological signals from the surface of the skin, comprising a casing, conducting means secured to said casing and adapted to form one plate of an input capacitor, amplifying means housed within said conducting means, coupling means for insulating said conducting means from the surface of the skin and adapted to physically connect the surface of the skin to an input of said amplifying means through said conducting means so that the skin forms the other plate of said input capacitor, said coupling means comprising inert material which eliminates skin irritation and other medical complications arising from contact with the skin surface, wherein said amplifying means has feedback means comprising a feedback capacitor and a pair of diodes connected back-to-back in parallel with said feedback capacitor for providing high capacitive reactance and limiting leakage, and an output of said amplifier means from which amplified physiological signals can be extracted.

2. The electrode of claim 1, wherein said coupling means includes an insulating film covering the outside surface of said conducting means.

3. The electrode of claim 2, including retaining means adjacent said casing and physically engaging said insulating film for removably mounting said insulating film over the outside surface of said conducting means.

4. The electrode of claim 1, including resistive means connected across the input of said amplifying means for leaking off charge at the input of said amplifying means when going into saturation.

5. The electrode of claim 1, wherein said pair of diodes breakdown to a low resistance level at a predetermined voltage level hastening the decay of a transient voltage allowing rapid recovery from saturation.

6. The electrode of claim 1, wherein said diodes are Zener diodes.

7. A dry contact electrode for receiving physiological signals from the surface of the skin of a patient, the electrode comprising:

a main casing;

conducting means supported by said main casing for defining one plate of an input capacitor;

insulating means associating with said conductiNg means for insulating said conducting means from the skin of a patient in such a manner that when said dry contact electrode is in contact with the skin of the patient, the skin defines the other plate of said input capacitor;

amplifying means housed by said main casing;

circuit means for connecting said input capacitor to said amplifying means;

output means for transmitting the output signal developed by said amplifying means to a load;

feedback capacitance connected between an input and an output of said amplifying means; and

a pair of feedback diodes connected back-to-back in parallel across said feedback capacitance.

8. The electrode of claim 7, and further comprising resistor means connected across the input of said amplifying means.

9. The electrode of claim 7, wherein said diodes are Zener diodes.

10. The electrode of claim 7, wherein said insulating means takes the form of a film covering the outside surface of said conducting means.

11. The electrode of claim 10, and further comprising retaining means for removably mounting said insulating film over the outside surface of said conducting means.

12. A dry contact electrode for receiving physiological signals from the surface of the skin of a patient, the electrode comprising:

a main casing;

conducting means supported by said main casing for contacting the surface of the skin of the patient;

amplifying means housed by said main casing;

capacitor means connected between said conducting means and an input of said amplifying means for transmitting physiological signals to said amplifying means;

output means for transmitting the output signals developed by said amplifying means to a load;

feedback capacitance connected between the input and the output of said amplifying means; and

a pair of feedback diodes connected back-to-back in parallel across said feedback capacitance.