Method and apparatus for bio-electrical signal measurement

• US 3,915,154 A
• Filed: 05/08/1974
• Issued: 10/28/1975
• Est. Priority Date: 04/28/1972
• Status: Expired due to Term

• Current Assignee: Kontron (S&T AG)
• Original Assignee: Louis Ciro Cosentino
• Inventors: Cosentino, Louis Ciro
• Primary Examiner(s): Kamm, William E.
• Application Number:
  US05/468,056
• Time in Patent Office: 538 Days
• Field of Search: 128/2.6B,2.6G,2.6R,2.1A,2.1P,2.1R 321/2 330/68
• US Class Current: 128/898
• CPC Class Codes: A61B 5/301 providing electrical separation, e.g. by using isolating transformers or optocouplers
• CPC Class Codes: A61B 5/305 Common mode rejection
• CPC Class Codes: Y10S 128/908 Patient protection from electric shock

Abstract

Electrical instrumentation for deriving bio-electrical signals is supplied with an isolated front-end amplifying system enclosed by a floating shield connected to one of the patient leads to provide a high common mode rejection ratio and good isolation, and transformer or other suitable isolation coupling furnishes output signals from the isolated front end to the instrumentation processing circuitry.

Claims

1. In electrical instrumentation for deriving bio-electrical signals and the like from a patient with at least a three patient lead system, first means including amplifier means adapted for connection with a first one and second one of said leads for producing bio-electrical output signals, second means for processing said signals, and coupling means for coupling said output signals from said first means to said second means via an electrically nonconducting path, the improvement comprising, electrical floating shield means arranged to be an electrical extension of a third one of said patient leads, said shield means enclosing said first means and shielding the electrical input signal leads thereto and further enclosing the portion of said coupling means electrically coupled to said first means, for virtually eliminating common mode interference by inhibiting patient common mode current from flowing through said first means.

2. In electrical instrumentation according to claim 1 including, electrical power supply means forming a part of said second means, and second coupling means for transmitting power from said power supply means to said first means via an electrically nonconductive path.

3. In electrical instrumentation according to claim 1 wherein, said coupling means comprises shielded high frequency transformer means where at least a single shield of said transformer means is electrically connected with said electrical floating shield means.

4. In electrical instrumentation according to claim 3 wherein, the second one of said leads serves as a connection for floating ground reference of said first means, and said second means is adapted for connection to an earth ground reference, and said high frequency transformer means includes a first winding outside of said floating shield means for connection to earth ground reference and a second winding within said floating shield means for connection to the floating ground reference.

5. In electrical instrumentation according to claim 1 wherein said coupling means comprises, a light emitting unit inside said floating shield and connected from said amplifier means, light pick-up means outside of said floating shield, and a light conductor optically connected from said light emitting unit to said light pick-up means.

6. In electrical instrumentation according to claim 4 including, electrical power supply means forming a part of said second meAns, and second shielded high frequency transformer means for transmitting power from said power supply means to said first means and where at least one shield thereof is electrically connected with said electrical floating shield means.

7. A method for isolating a patient from earth grounded type electrical instrumentation and for accurately measuring patient bio-electrical signals comprising, providing an amplifier system for connection to at least first and second patient leads, for deriving such signals whereby one of said leads is referenced as a floating ground, coupling the derived signals to said instrumentation via first means providing an electrically nonconductive coupling path, and enclosing the amplifying system and the portion of said first means coupled thereto within an electrical floating shield, wherein said shield is an electrical extension of a third patient lead.

8. A method according to claim 7 including, utilizing either of the first or second leads as a floating ground potential at a negative input of the amplifier system.