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Publication numberUS3620208 A
Publication typeGrant
Publication date16 Nov 1971
Filing date3 Nov 1969
Priority date3 Nov 1969
Publication numberUS 3620208 A, US 3620208A, US-A-3620208, US3620208 A, US3620208A
InventorsHigley Wayne R, Silcocks Harry L, Waggoner James A
Original AssigneeAtomic Energy Commission
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Ekg amplifying electrode pickup
US 3620208 A
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Description  (OCR text may contain errors)

United States Patent [72] Inventors Wayne R. I-llgley;

Harry L. Silcoclts; James A. Waggoner, all of Livermore, Calif. [21] Appl. No. 873.223 [22] Filed Nov. 3, 1969 [45] Patented Nov. 16, 1971 [73] Assignee The United States 0! America as represented by the United States Atomic Energy Commission [54] EKG AMPLIFYING ELECTRODE PICKUP 10 Claims, 4 Drawing Figs.

[52] U.S. Cl 128/2.06 E, 128/D1G. 4 [51] Int. A611) 5/04 [50] Field olSearch .1 128/206 E. 206 R. 2.1 E. DIG. 4; 330/68 [56] References Cited UNITED STATES PATENTS $212,496 10/1965 Preston 128/206 R 3,500,823 3/1970 Richardson et a1. 128/206 E 3.542.013 11/1970 Stephenson 1. 128/206 E FOREIGN PATENTS 1,164,770 5/1958 France 128/206 E Primary Examiner-William E. Kamm Attorney-Roland A. Anderson ABSTRACT: An amplifying electrode pickup for an electrocardiograph (EKGJ device consisting broadly of an impedance converter integrated amplifier circuit potted in a metal shell. The integrated circuit is biased by a nanoamp electrical current. The EKG, signal is sensed by a small sensor plate or disc positioned in a boot or cover and is electrically insulated from the shell. The circuit has a very high input impedance to minimize the effect of skin contact resistance changes, and a very low output impedance to minimize noise pickup by the signal line between the electrode and the EKG electronics. Electronic circuitry in the potted metal shell also includes a diode voltage clamp and decoupling RC circuits. A multiconductor cable provides shielding. conducts power to the electrode, and transmits the signal from the electrode through an integral coaxial cable Because of the low (nanoamp) biasing current. signal traces of numerous separate electrodes can be simultaneously recorded without exceeding the maximum permissible current through the human body as established by the American Heart Association.

SHIELD SIGNAL 23 PATENTEDuuv 16 I97! 3. 620 2 O8 sum 1 or 2 SHIELD 24 SIGNAL 23 INVENTORS Wayne R. Higley Harry L. Silcacks James A. Waggoner ATTORNEY.

PAIENTEDNUV 1619?! 3, 620,208

SHEET 2 [IF 2 A As 'n n w PLATE 3s 29 35" A TO CURRENT TAPE d6 RECORDER B 17 38 cm l 35 40 I 29M Mull I m 1$ CURRENT LIMITER Q7 PLU c PLATE A SlGNAUA-B) 44 1 l CED INVENTORS. Wayne R. Higley Harry L. Silcocks W James A. Waggoner BACKGROUND OF THE INVENTION The invention described herein was made in the course of, or under, Contract No. \V-7405-ENG-48, with the US. Atomic Energy Commission.

The maximum permissible current which may be conducted through a live human body for diagnostic purposes is one microamp, this limit being set by the American Heart Association. A typical electrocardiograph (EKG) device has at least five to ten leads connected to the human body. Each lead typically requires relatively large biasing currents (on the order of 0.1 to l microamp). Hence, often only one or two signal traces can be recorded simultaneously.

Moreover, a typical EKG lead consists simply of a conductive plate at the end of a shielded single conductor cable. Consequently, these leads pick up considerable extraneous electronic noise (signals) from their environment. Also, changes in skin contact resistance will degrade the quality of the resultant signal traces. In order to minimize noise pickup, the input impedance into the EKG electronics must be kept as low as possible. However, in order to minimize the eflects of changes in skin contact resistance, the input impedance into the EKG electronics must be relatively high. Hence, minimizing one effect increases the other.

While various prior art efforts have been directed to the solution of the above impedance problems in EKG electrodes, none are known which incorporate the amplifier electronics into the electrode and which have a very high input impedance to minimize the effect of skin resistance changes, and I a very low output impedance to minimize noise pickup. Thus, there has long been a need, for diagnostic purposes, for electrodes which would enable the simultaneous recording of signal traces from every lead; ten leads usually being required for a complete set of EKG traces.

SUMMARY OF THE INVENTION The invention is an amplifying electrode for an electrocardiograph device which solves the above-cited problems of the prior devices. It consists of an integrated impedance converter amplifier circuit having a high input impedance and a low output impedance, potted in a metal shell for electrostatic and electromagnetic shielding. The amplifier circuit is driven by a nanoamp current signal sensed by a small conductive plate which caps, but is insulated from, the conetic metal shell. The high input impedance of the integrated circuit minimizes the effect of skin contact resistance, while the low output impedance minimizes noise pickup in the signal line to the remainder of the EKG electronics. Most importantly, the integrated impedance converter amplifier circuit requires only about a IO-nanoamp biasing current for operation. Hence, signal traces of up to 100 separate electrodes can be simultaneously recorded without exceeding the maximum permissible current through the human body.

Therefore, it is an object of this invention to provide an EKG amplifying electrode pickup.

A further object of the invention is to provide an amplifying electrode having a high input impedance and a low output impedance.

Another object of the invention is to provide an amplifying electrode pickup for an EKG device which utilizes an integrated impedance converter amplifier circuit potted in a metal shell and driven by a nanoamp current signal sensed by a small conductive plate which caps, but is insulated from, the metal shell.

Other objects of the invention will become readily apparent from the following description and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a greatly enlarged view, partially in cross section, of an embodiment of the inventive amplifying electrode;

FIG. 2 is a simplified schematic of the inventive electrode circuitry;

FIG. 3 is a schematic view showing a plurality of the inventive electrodes operatively connected individually to an electrocardiagraph device, tape recorder, etc.; and

FIG. 4 is a schematic view of a pair of the inventive electrodes operatively connected to provide a difference output signal.

DESCRIPTION OF THE INVENTION Referring now to the drawings, an embodiment of an electrode made in accordance with the invention is illustrated in FIGS. 1 and 2. Generally, the electrode assembly comprises a shell or container 10 constructed of metal or other suitable material, for electrostatic and electromagnetic shielding, with various electronic components, described in detail hereinafter, secured therein by a suitable potting material ll, such as polyurethane, as known in the an. A cover or boot I2 is positioned over the open end of shell 10 and may be made of vinyl or other suitable insulating material, boot I2 having a centrally located aperture 13 within which is positioned a flat conductor or sensor plate I4 constructed, for example, of stainless steel. A multiconductor cable, described in detail hereinbelow, is secured at one end thereof to shell 10 via an internally positioned ferrule 15 and an external metal clamptype collar 16, and is operatively connected at the opposite end to a plug assembly generally indicated at 17.

The electronic components and circuitry comprising the inventive electrode are illustrated schematically in FIG. 2 with a portion of same being physically illustrated in FIG. I. The multiconductor cable has an outer insulating cover 18 of Suflex (insulated tubing) or the like, an outer grounded shield 19 of copper braid, for example, a positive voltage DC powerline 20, a negative voltage DC powerline 21, a ground lead 22, a central output signal line or conductor 23, and an inner grounded shield 24 coaxially positioned about output line 23. The outer cover 18 of the cable is secured between ferrule I5 and clamplike collar 16, ferrule 15 being connected to ground as indicated at 25 via inner shield 24; while outer cover 18 and each of the cable components 19-24 are each secured to the plug assembly 17.

The electrode electronics generally indicated at 26 in FIG. 2 is electrically connected to sensor plate 14, positive and negative voltage DC powerlines 20 and 21, and central output signal line 23, as well as the necessary ground connections required for operation. The sensor plate I4 is connected to an integrated impedance converter amplifier circuit 27 via lead 28 and is isolated from the amplifier power supply voltage by a large resistor or other current limiting means 29, which may be a l M-ohm resistor Resistor 29 is not essential to the operation of the electrode but is inserted for safety purposes to isolate the patient from the power supply. The converter amplifier circuit 27 may, for example, be a commercially available LM-302 integrated circuit manufactured by the National Semiconductor Corporation and having a high input impedance of up to 10,000 meg. ohms, for example, and a low output impedance of 1 ohm, for example. Noise in the positive and negative power supply lines 20 and 21, respectively, is decoupled by two simple RC circuits, operatively connected to lines 20 and 21, generally indicated at 28 and 29, and comprising resistors R, and R, and capacitors C, and C the capacitors being connected to ground. For example, R, and R, may be 300 ohms with C, and C, being a 2.2 microfarad tantalum capacitor. Two diodes D, and D are connected between the central output signal line 23 and the power supply lines 20 and 21 via leads 30 and 31, respectively, and clamp the amplified signal voltage between the voltage of the positive line of +15 volts, for example, and the voltage on the negative line of IS volts, for example. The amplifier circuit 27 provides a gain of at least 0.999 and requires only a 10- nanoamp biasing current. The voltage clamp provided by diodes D, and D, isolates the sensitive electronics of an associated EKG device, for example. This feature allows highvoltage shocks to be applied to the patient to stimulate heart action. for example. without disconnecting the EKG apparatus Structurally. as partly seen in FIG. I. sensor plate I4 is positively insulated by an insulator 32. while an insulator 33 is positioned between shell I and amplifier circuit 27 For example. the insulators 32 and 33 may be made of Dacron fiber tape. The various resistors and capacitors as well as the amplifier circuit and the sensor plate illustrated in FIG. I are electrically interconnected via a printed circuit board assembly 34 by leads as partially shown. and a readily known in the art. With the novel arrangement described hereinabove. the amplifying electronics of the remainder of the EKG device. or other apparatus. need not be as sophisticated for purposes of noise-rejection amplification. etc as presently utilized.

The high input impedance of the integrated converter amplifier circuit 27 minimizes the eflect of skin contact resistance. while the low output impedance thereof minimizes noise pickup in the signal line 23 to the remainder of the associated EKG electronics Most importantly. the amplifier circuit requires only a IO-nanoamp biasing current for operation. Hence. signal traces of up to I00 separate electrodes can be simultaneously recorded without exceeding the maximum permissible current through the human body FIG. 3 illustrates the application of a plurality of the inventive electrodes connected to an EKG device or other mechanism whereby the individual signal traces are recorded. While the components of FIG I are utilized in each of the electrodes generally indicated at A. B. N in FIG. 3. the electrodes in FIG. 3 are illustrated very schematically for purposes of simplicity with each respectively comprising a sensor plate l4 I4, and 14.. a resistor 29,. 29,, and 29 an amplifier 27.. 27, and 27.. and output signal line 23.. 23 and 23, connected to plug assemblies 17.. I7, and I7. Each of plug as semblies l7.. l7 and I7. comprises a male and female section 35 and 36 with the plug sections 36 connected to separate amplifiers 38 38,, and 38.. respectively. the outputs thereof. indicated at 39.. 39,, and 39.. being directed to a tape recorder or other mechanism as indicated by legend. Generally the plug assembly sections 36 and amplifiers 38. 38 and 38. are located within a housing 40 or the like. depending on the mechanism associated therewith The details of the amplifiers 38 do not constitute part of this invention but may. for example. be a commercially produced differential amplifier with a gain of L000 such as several cascaded stages made up of UA709C integrated circuits manufactured by Fairchild Camera.

FIG. 4 very schematically illustrates the connection of a pair of the inventive electrode assemblies to provide a difference reading therebetween. again each of the electrode assemblies being constructed in accordance with the FIG. I embodiment. though simplified in this illustration The two electrodes are generally indicated at A and B and consist of sensor plates I4 and I4". large resistors 29' and 29". integrated impedance converter amplifier circuits 27 and 27". central output signal transmission lines or conductors 23 and 23" connected to plug assemblies I7 and 17" each consisting of plug sections 3S'36' and 35"36". The output signals from plug assemblies I7 and I7". as indicated at 4| and 42. respectively are directed to an amplifier circuit 43 which. for example. may be a commercially produced differential amplifier with a gain of 1.000. such as the UA709C An output signal indicated at 44 from amplifier 43 is a difference signal of electrode A and B and thus legended Signal (AB). signal 44 being transmitted to a strip chart recorder or other mechanism or point of use.

It has thus been shown that the present invention provides an amplifying electrode which is particularly adapted as a pickup electrode for an electrocardiograph (EKG) device. this being accomplished by an integrated amplifier circuit potted in the electrode shell which is biased by a nanoamp electrical signal. and has a very high input impedance to minimize the effect of skin resistance changes. and a very low output impedance to minimize noise pickup by the output signal line between the electrode and the EKG electronics If desired. the electrode can be modified by attaching a stud to the metal shell to aid in attaching the electrode to a patient Also. a suction hose or bulb along with a channel or pipe through the electrode can be provided to aid in attaching the electrode to the torso of the patient.

While the impedance converter has been set forth as having a gain nearly equal to 1. other values can be used provided all electrodes being used at one time have equal values of gain to within three significant figures. for example. or some form of dynamic calibration. This would be accomplished by a selection process to obtain the desired gainv Although the power source as described herein is external to the electrode assembly. batteries can be incorporated into the individual electrodes. Also. the multiconductor cable can be attached to the electrode shell by means of a plug-type connector. or the like. such ihat the cable can be easily repaired or replaced without disturbing the electrode assembly Although a particular embodiment of the invention has been illustrated and described. modifications will become ap' parent to those skilled in the art. and it is intended to cover in the appended claims all such modifications as come within the spirit and scope of the invention.

What we claim is:

I An amplifying electrode pickup. particularly adapted for an electrocardiograph device comprising: container means having an open end portion; a cover means for said open end portion of said container means, said cover means being provided with an aperture therethrough; an electrically conductive sensor plate means supported in said aperture of said cover means; electronic means secured in said container means and electrically insulated from said container means and from said cover means. a multiconductor cable means secured in an aperture ofsaid container means and electrically connected to said electronic means; said electronic means in cluding an integrated impedance converter amplifier circuit means electrically connected to said conductive plate means. at least one voltage line constituting certain of the conductors of said multiconductor cable means being connected to said amplifier circuit means. a pair of resistor-capacitor circuit means connected to positive and negative voltage lines of said multiconductor cable means. an output signal line connected to said amplifier circuit means and constituting another conductor of said multiconductor cable means. a diode means connected between said positive voltage line and said output signal line. a second diode means connected between said negative voltage line and said output signal line. said multiconductor cable means additionally including electrical shielding means about said output signal line and about said positive and negative voltage lines.

2. The amplifying electrode pickup defined in claim I. wherein said container means is constructed of metal and said cover means is constructed ofa noncoriductive material.

3 The amplifying electrode pickup defined in claim I. additionally including means for securing said multiconductor cable means in said container means aperture. said securing means comprising a ferrulelike means located internally of said container means and a clamplike collar means located externally ofsaid container means 4. The amplifying electrode pickup defined in claim l.additionally including a pluglike assembly means having one end ofsaid multiconductor cable means secured thereto.

5. The amplifying electrode pickup defined in claim I. wherein said multiconductor cable means comprises an outer insulating cover. an outer grounded shield constituting said electrical shielding means about said positive and negative voltage lines. said positive voltage line. said negative voltage line. a grounded lead. said output signal line. and an inner grounded shield constituting said electrical shielding means about said output signal line. said outer and inner grounded shields being connected for ground purposes to said grounded lead.

6 The amplifying electrode pickup defined in claim I. wherein said electronic means is secured in said container means by appropriate potting material of about 10,000 meg. ohms and an output impedance of about 1 ohm and is constructed to be biased by about a 10 nanoamp current.

10. The amplifying electrode pickup defined in claim I, wherein said container means is constructed of metal. said sensor plate means is constructed of stainless steel. and said cover means is constructed of a insulating material.

# t l 4 I01

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US3212496 *21 Aug 196219 Oct 1965United Aircraft CorpMolecular physiological monitoring system
US3500823 *20 Nov 196717 Mar 1970Us Air ForceElectrocardiographic and bioelectric capacitive electrode
US3542013 *25 Sep 196824 Nov 1970Walter Raymond Barrett JrEkg pickup assembly
FR1164770A * Title not available
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US3735425 *10 Feb 197129 May 1973Us Of America The Secretary OfMyoelectrically controlled prothesis
US3747590 *21 Jun 197124 Jul 1973Nat Cable Molding CorpBiopotential electrode
US3868947 *16 Oct 19734 Mar 1975Us GovernmentConcentric electrode construction for an electrocardiogram transmitter
US3882846 *4 Apr 197313 May 1975Robert M DavidInsulated electrocardiographic electrodes
US3991747 *5 Aug 197416 Nov 1976Albert L. StanlyPortable cardiac monitoring system and method
US4122843 *10 Aug 197731 Oct 1978Electro-Technics, Inc.Electrode system for a heart rate monitor
US4155354 *21 Mar 197722 May 1979Rasmussen Steen BDisposable electromedical electrode and a set of such electrodes
US4245649 *25 Jul 197820 Jan 1981Schmidt Andersen PoulDevice for monitoring biological signals from patients, while an electro-surgical appliance is being simultaneously used
US4249538 *12 Dec 197810 Feb 1981Toshimitsu MushaElectronic clinic apparatus
US4261371 *18 Jan 197814 Apr 1981Reading Iii William HMethod and apparatus for determining ovulation in female mammalia
US4396019 *8 Jun 19812 Aug 1983Perry Jr John DVaginal myograph method and apparatus
US4628939 *10 Nov 198316 Dec 1986Hughes Aircraft CompanyMethod and improved apparatus for analyzing heart activity
US4640290 *25 Apr 19853 Feb 1987Westinghouse Electric Corp.Shielded, self-preparing electrode suitable for electroencephalographic mapping
US4669479 *21 Aug 19852 Jun 1987Spring Creek Institute, Inc.Dry electrode system for detection of biopotentials
US4686998 *12 Nov 198518 Aug 1987Mediscan Research LimitedPatient temperature and heartbeat rate monitoring system
US4697598 *25 Apr 19856 Oct 1987Westinghouse Electric Corp.Evoked potential autorefractometry system
US4751471 *23 Dec 198614 Jun 1988Spring Creek Institute, Inc.Amplifying circuit particularly adapted for amplifying a biopotential input signal
US4763659 *20 Aug 198616 Aug 1988Spring Creek Institute, Inc.Dry electrode system for detection of biopotentials
US4861154 *6 Aug 198629 Aug 1989Westinghouse Electric Corp.Automated visual assessment system with steady state visual evoked potential stimulator and product detector
US4865039 *20 May 198812 Sep 1989Spring Creek InstituteDry electrode system for detection of biopotentials and dry electrode for making electrical and mechanical connection to a living body
US5299572 *30 Oct 19925 Apr 1994University Of British ColumbiaBiological electrode array
US5443559 *24 Nov 199322 Aug 1995The University Of British ColumbiaBrush-tip electrode
US6327486 *18 Jun 19994 Dec 2001Polar Electro OyScreen
US6600942 *17 Oct 200129 Jul 2003Polar Electro OyScreen
US6718191 *11 Jun 20016 Apr 2004Medikro OySkin potential measuring sensor
US6961601 *11 Jun 20031 Nov 2005Quantum Applied Science & Research, Inc.Sensor system for measuring biopotentials
US708817514 Aug 20038 Aug 2006Quantum Applied Science & Research, Inc.Low noise, electric field sensor
US7136690 *19 May 200414 Nov 2006Stephan BohmElectrode for biomedical measurements
US71419687 Oct 200428 Nov 2006Quasar Federal Systems, Inc.Integrated sensor system for measuring electric and/or magnetic field vector components
US71419877 Oct 200428 Nov 2006Quantum Applied Science And Research, Inc.Sensor system for measurement of one or more vector components of an electric field
US71734379 Jun 20056 Feb 2007Quantum Applied Science And Research, Inc.Garment incorporating embedded physiological sensors
US724595617 Aug 200417 Jul 2007Quantum Applied Science & Research, Inc.Unobtrusive measurement system for bioelectric signals
US7260428 *8 Jan 200421 Aug 2007Ge Healthcare Finland OyShield arrangement for ECG lead wires
US7373196 *29 Dec 200413 May 2008Electronics And Telecommunications Research InstitutePhysiological signal detection module, multi-channel connector module and physiological signal detection apparatus using the same
US7885700 *9 Dec 20028 Feb 2011The University Of SussexElectrodynamic sensors and applications thereof
US81656524 Apr 200824 Apr 2012Electronics And Telecommunications Research InstitutePhysiological signal detection module, multi-channel connector module and physiological signal detection apparatus using the same
EP0114922A2 *19 Jul 19838 Aug 1984Központi Valto-Es Hitelbank Rt Innovacios AlapDetecting device to prevent dysphonia during infancy
EP0232412A1 *21 Aug 198619 Aug 1987Spring Creek Institute, Inc.Dry electrode system, disposable electrode pad, and amplifier circuit for detection of biopotentials
WO2004110268A1 *10 Jun 200423 Dec 2004Andrew D HibbsSensor system for measuring biopotentials
Classifications
U.S. Classification600/395
International ClassificationA61B5/0402, A61B5/0428
Cooperative ClassificationA61B5/04284, A61B5/0428
European ClassificationA61B5/0428, A61B5/0428D