NONLINEAR ELECTROMYOGRAPH

• US 3,641,993 A
• Filed: 04/23/1970
• Issued: 02/15/1972
• Est. Priority Date: 04/23/1970
• Status: Expired due to Term

• Current Assignee: Kenneth R. Gaarder, William B. Leaf
• Original Assignee: Kenneth R. Gaarder, William B. Leaf
• Inventors: Gaarder, Kenneth R., Leaf, William B.
• Primary Examiner(s): Kamm, William E.
• Application Number:
  US05/031,344
• Time in Patent Office: 663 Days
• Field of Search: 128/2.6A,2.6B,2.6G,2.6R,2.1R,419R 3/1.1
• US Class Current: 600/546
• CPC Class Codes: A61B 5/389 Electromyography [EMG]
• CPC Class Codes: A61B 5/486 Bio-feedback A61B5/375 takes precedence
• CPC Class Codes: A61B 5/7242 using integration
• CPC Class Codes: Y10S 128/905 Feedback to patient of biological signal other than brain electric signal

Abstract

This specification discloses an electrical apparatus which measures human muscle activity and provides both visual and audio information relative to such activity for feedback to the human. Slight skin voltages caused by muscle activity are assumed by electrodes, transmitted via shielded electrical leads and processed by the apparatus, first to provide a visual display of the instantaneous logarithm of the peak value of such signals and secondly to provide a visual display of an accumulation or integration of the instantaneous logarithm of the peak signal values over a selectable and timed integration interval. In addition to these visual indications for human feedback, an audio signal, with a frequency proportional to the instantaneous logarithm of the peak value, is provided as a string of sharp pulses thus allowing human discrimination at very low frequencies such as 1 Hz.

Claims

1. An electrical apparatus for indicating degree of muscle activity by measuring skin voltages assumed by electrodes positioned adjacent to skin surfaces and caused by said muscle activity, said device comprising:

input means for connection to said electrodes and for receiving and amplifying said skin voltages, said input means including nonlinear means for amplifying said skin voltage in a nonlinear fashion providing relatively high gain at low skin voltage levels and increasingly lower gains at higher skin voltage levels to produce a nonlinear output signal proportional to a nonlinear function of said skin voltages, and feedback means connected to said input means for receiving said nonlinear output signal and for producing a humanly sensible feedback signal therefrom.

2. A device as in claim 1 wherein said feedback means comprises:

first means connected to said input means for visually displaying said nonlinear output signal proportional to a nonlinear function of said skin voltages;

second means also connected to said input means for simultaneous computation and visual display of a further signal proportional to an integrated value of said nonlinear output signal over a timed interval of integration; and

third means also connected to said input means for simultaneously producing an audible pulse response having a frequency or pulse repetition rate dependent upon said nonlinear output signal.

3. A device as in claim 2 wherein said second means includes a timing means connected therein to automatically terminate said timed interval of integration.

4. A device as in claim 3 wherein said second means includes manual resetting means connected to initiate said timed interval of integration upon manual actuation.

5. A device as in claim 2 wherein said third means includes:

means connected to said input means for producing sharply shaped pulses of electrical energy having a relatively low pulse repetition rate proportional to the instantaneous value of said nonlinear output signal and, means connected to receive said sharply shaped pulses for converting said pulses to an audible audio response resembling a series of '"'"''"'"''"'"''"'"'clicks'"'"''"'"''"'"''"'"' thereby permitting human detection and discrimination at very low basic pulse or '"'"''"'"''"'"''"'"'click'"'"''"'"''"'"''"'"' repetition frequencies to permit precisely accurate audio signal feedback independent of any visual feedback to a human user of the device.

6. A device as in claim 2 including ohmmeter means for measuring the electrical resistance between said electrodes and said skin surfaces.

7. An electrical device for measuring muscle activity and for providing an indication of such activity, said device comprising:

electrodes for electrical contact with at least two points on a skin surface;

shielded electrical leads for conducting signals from said electrode means;

differential amplification means for combining electrical signals from said shielded leads into a single common output signal and for cancelling all common mode electrical signals;

electronic conversion means for obtaining a peak value of said common output signal and for producing a nonlinear signal proportional to a nonlinear function of said peak value;

visual display means to visually display said nonlinear signal;

first integration means for integrating said nonlinear signal and for producing an accumulated output signal during a times interval;

timing means to terminate said timed interval;

reset means to begin said timed interval;

visual display means to visually display said accumulated output signal;

pulse-generating means for producing electrical pulses at a frequency proportional to said nonlinear signal; and

audio response means to provide an audible sound wave in response to said electrical pulses.

8. A device as in claim 7 wherein said electronic conversion means comprises:

full-wave rectifying means for rectifying said common output signal;

peak detection means with an input signal and an output signal including an operational amplifier with a controlled gain;

gain-controlling means to cause said controlled gain to vary inversely with respect to said output signal such that said output signal is approximately proportional to said nonlinear function of said peak value of said input signal.

9. A device as in claim 7 wherein said pulse-generating means includes:

second integrating means with an output and an input responsive to said nonlinear signal having a first polarity; and

an automatic resetting means connected to the output of said second integrating means for delivery of resetting pulse signals at a frequency proportional to the output of said second integrating means and hence dependent upon said nonlinear signal.

10. A device as in claim 7 including ohmmeter means for measuring the electrical resistance between said electrodes and said skin surface.