Electrode isolation amplifier

• US 5,099,856 A
• Filed: 11/08/1989
• Issued: 03/31/1992
• Est. Priority Date: 11/08/1989
• Status: Expired due to Fees

• Current Assignee: Etymotic Research Incorporated
• Original Assignee: Etymotic Research Incorporated
• Inventors: Wilson, Donald L., Killion, Mead C., Stewart, Jonathan K.
• Primary Examiner(s): Pellegrino, Stephen C.
• Assistant Examiner(s): SHUMAKER, STEVEN
• Application Number:
  US07/433,633
• Time in Patent Office: 874 Days
• Field of Search: 128/731, 128/732, 128/746, 128/632, 128/635, 128/419 R, 128/696, 128/653, 128/901, 128/908, 250/215, 250/515.1
• US Class Current: 600/544
• CPC Class Codes: A61B 5/30 Input circuits therefor
• CPC Class Codes: A61B 5/369 Electroencephalography [EEG] devices for psychotechnics A61B5/16

Abstract

A system for detecting and transmitting body electrical signals in the presence of ambient electrical interference that uses a transmiter circuit including an amplifier coupled to and in close proximity to two or more body electrodes, a light pulse generator that receives its input from that amplifier and provides a pulse-duration-modulated series of light pulses, and a remote receiver including a transducer which demodulates the transmitted light pulses into electrical pulses of corresponding duration and frequency and a demodulator which accepts those electrical pulses and produces an amplified replica of the original signal developed between the body electrodes, thereby effectively providing complete electrical isolation of the electrode amplifier from the remaining bioelectrical signal analysis equipment. A valuable additional feature of the invention is a complete electrostatic shield around the amplifier-transmitter as well as the electode leads, so that the small amount of residual capacitive coupling to the amplifier circuit itself is effectively shunted to the same average (body) potential as that of the electrodes.

Claims

1. A system for detecting and transmitting body electrical signals in the presence of ambient electrical interference, comprising:

at least two electrodes adapted for attachment to the body at spaced body locations between which electrical signals are generated by the body in response to a predetermined stimulus;

an independently-grounded transmitter circuit arranged to be mounted in close proximity to and attachable to the body and coupled to said electrodes in close proximity thereto, said circuit comprising;

a) a source of electrical power;

b) amplifier means coupled to said source for energization therefrom and having an input arranged to be coupled to said electrodes to detect body signals and operative for developing an output signal whose magnitude varies with the detected body signals;

c) light pulse generator means coupled to said amplifier to respond to said output signal and to develop output light pulses having durations which vary in accordance with said amplifier output signal; and

d) grounding means for providing independent ground path of short length between the body and said source and said amplifier means to minimize electrical interference;

a receiver optically coupled to and remote from said transmitter and comprising;

a) a transducer converting said transmitted light pulses into electrical pulses of corresponding duration and frequency, and

b) demodulation means responsive to said transducer electrical pulses and producing an amplified version of the original signal between said first and second electrodes, said electrical power source being a minature single-cell battery, said light pulse generator including a light emitting diode and a voltage doubler circuit connected to said single-cell battery and driven from said amplifier output signal, said voltage doubler circuit being arranged for supplying voltage pulses to said diode at an amplitude level substantially greater than the voltage available from said single-cell battery.