Human resistivity sensing device

Abstract

An electrical circuit which is capable of producing a varying signal output, either in frequency or amplitude which is responsive to the changing resistivity sensed on the skin of a subject. Electrodes are placed on the subject's body and as the surface resistance changes, an audible signal is produced which can aid the subject in relaxing.

Description

This invention relates to a bio-feedback type device used to gauge the level of tension of a subject.

It is proposed to provide a unique and improved electrical circuit having extremely good reliability and good utilization to sense the anxiety levels of a subject by producing an audible sound which is reflective of the subject's state. Biasing means are provided to set a norm about which the audible tone will vary.

The attached FIGURE illustrates an embodiment of this invention.

The electrical circuit is comprised of electrodes 10 and 12 attached to a gripping member 14 which is capable of being either in a flat position so as to be attached to a flat surface of the body, or circular so as to be attached to an extremity. Electrode 10 is connected to the base of a transistor 16 through a resistor 18 and through a fixed resistor 20 and a biasing resistor 22 to the emitter of transistor 16. The collector of the transistor is connected through a resistor 24 to an emitter terminal of a unijunction transistor 26 as well as to one end of a capacitor 28, the other end of which is connected to ground. One base terminal of the unijunction transistor is connected through a resistor 30 to one end of a speaker 32 coil 34 and to the emitter of transistor 16. The other end of speaker coil 34 is connected to the collector of a transistor 36, the emitter of which is connected to ground while the base thereof is connected to the second base terminal of unijunction transistor 26.

The circuit functions in the following manner: electrodes 10 and 12 connect to various places on the skin of the body. The person using the instrument adjusts the range or biasing control by varying resistance 22 to a desired tone, such as many-frequency. As his body resistance decreases, the frequency of the tone increases thus signalling greater anxiety for lesser body resistance. Capacitor 28 is charged through transistor 16 at a rate controlled by resistor 22 which controls the amount of current produced by current source means formed by transistor 16. Unijunction transistor 26 is a triggering device which is caused to trigger when its threshold rate is reached. The rate at which the level is reached is set by biasing resistor 22 but will be varied as the body resistance sensed at electrodes 10 and 12 varies. This is due to the voltage divider formed by the body resistance and resistors 20 and 22.

The output of unijunction transistor 26 is coupled through amplifier means formed by transistor 36 to energize speaker 32 so as to produce an audible sound.

Claims

I claim:

1. Electrical circuit means capable of being connected to the human body and producing a changing signal in response to changes in the surface resistivity of the human skin comprising electrode means adapted to be placed on the skin, variable frequency means comprising a unijunction transistor having an emitter and a pair of base terminals, biasing means connected between said electrode means and said variable frequency means for setting a biasing level for said variable frequency means, said emitter being connected to said biasing means,

said biasing means comprising a transistor and a variable resistance controlling the amount of current produced by said transistor,

said transistor having a base resistor connected thereto, said electrode means being connected through said base resistor to the input of said transistor to control the amount of current produced thereby,

a collector resistor connected to the collector of said transistor, a capacitor connected through said collector resistor to receive said current of said transistor to be charged thereby, said capacitor connected to said emitter of said unijunction transistor to cause said unijunction transistor to be triggered into conduction,

said variable resistance and the resistance at the electrode means forming a voltage divider,

the connection between said voltage divider connected to said transistor through said base resistor and,

speaker means connected to receive the output of said variable frequency means to produce an audible signal representation of the frequency of the signal produced by said variable frequency means.

2. Electrical circuit means as set forth in claim 1, comprising amplifier means connected between the output of said unijunction transistor and said speaker means.