SU1242117A1 - Method of measuring resistance of skin of a biological object - Google Patents

Description

one

The invention relates to medical technology and is intended for use in labor protection institutes for measuring the skin resistance of a biological object under the influence of an electric field of industrial frequency.

The purpose of the invention is to eliminate the influence of the external electric field of industrial frequency on the results of measuring the resistance of the skin.

Fig, 1 shows a diagram for the implementation of the proposed method; in fig. 2 - the body of a biological object with superimposed electrodes; ka fig.Z - electrical equivalent circuits of the skin.

The method is carried out as follows.

Electrodes 1 and 2 are applied to the human skin area. The human body is connected to a common tire, applying, for example, on. ankle electrode 3. This stabilizes the passage of current from a source of electrical field through the human body, since the effect of distributed body capacitances relative to the earth is eliminated if the posture is randomly changed during the study of skin resistance. This increases the measurement accuracy.

To measure the current flowing from the source of the electric field through the active electrode 1, above it with a small gap of 0.1-0.2 mm), filled with a dielectric pad, an additional current-receiving electrode 4 is placed (Fig. 1). The electrodes and the human body, which is affected by the external electric field of industrial frequency, work in this case as an antenna, which receives the pickup signal. On the electrode 4, charges that flow through the input resistance of the current meter 8 and the connecting cable 7 to the active electrode 1 and then through the human body to the common bus are induced. At the output of cable 7 between the electrodes 1 and 2, they include a high-resistance (MOhm) voltage meter 9. The equation for dp potentials induced on the active and inactive electrodes by the external electric field of industrial frequency is expressed by the voltage drop across the outer layer of skin (epidermis) and the inner tissue of the body.

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FIG. 2, the human body is shown with the active I, inactive 2 and ground 3 electrodes placed on it, where, is the source of the external, electric field; C {and C capacity of the source of the external field relative to the electrodes 1 and 2.

For this arrangement, electrode overlap is attached to the Lig. 3 shows the electrical equivalent circuits of the human body: L - -; for the body section between the electrodes 1-3; b-dl body part between the electrodes 2 and 3, where and: Z HJ. . outer layer resistance

skin under electrodes 1 and 2; and R, 6i is the resistance of the internal fabric of the body under the electrodes 1 and 2 relative to the ground electrode; Z, - the resistance of the outer layer

the skin under a copy with a cuticle electrode. According to the second Kirchhoff's law for electrical equivalent circuits of a person (Fig. 3), we have

five

0

five

0

five

- UH Ub. + UH, (X)

fi- Ut, + UH, (L) where f, and v-fi. - potentials of electrodes 1 and 2 relative to the earth;

Uu and Ujj - voltage drop on the outer skin layer under electrodes 1 and 2, respectively;

Uj, and U, j. - voltage drop on the resistances of the internal tissues of the body bj, respectively - - - -1

HG; and - voltage drop

the outer layer of the skin Z, below the basement

an electrode.

Induced by the source of the external electric field T currents -f, and f. on electrodes I and 2. flow through the corresponding resistance of the epidermis 2ts n Z and cause them to fall:

 V lyv (3

The potential difference l and between electrodes 1 and 2, taking into account the equations (O - (3), is equal to

55 ....

f. , z -I, z, (4)

somewhere A, UR, -UR.

3 ;

When measuring skin resistance, the inactive electrode 2 is first shielded from the external floor by placing an electrostatic shield 6 above it, connected to the braided shielding of the connecting cable 7 and the transducer housing 10. At this, the current becomes zero. The difference between the potentials and the current Id flowing through the active electrode is measured. Sog is the equation (1) at I2.0, these quantities are related by

And At. t: f, z,

In addition to the electrode 2, the active electrode is shielded from the external field. To do this, an electrostatic shield 5 is installed over the current-collecting electrode 4 and connected to the braiding screen of the connecting cable 7. The screens 5 and 6 can be filled, for example, in the form of plates arranged with a gap above the corresponding shielded (electrodes 1 and 2. Moreover, the screen 5 with the possibility of bending it aside so as not to overlap the current-receiving electrode 4 and connected to 1shm electr

42117 .. 4

t genus 1 when measuring the current Y /. and potential difference l Over. After shielding of both electrodes, the currents I / 2. measure the potential difference f fi between electrodes 1 and 2, which, according to equation (5), is equal to

 l.

d d

(6)

Skin resistance Z is determined from equation (5) using measured values of potential differences d

Afc

with. and current 1. In view of the equation

(6) we have

(five)

15

A 2

(7)

Since, in the proposed method for measuring the skin resistance of a biological object, a pickup signal from an external electromagnetic field of industrial frequency is used as a source of voltage and a 50 Hz autonomous generator is not required, there is no electrical oscillation in the measuring system that implements the method. This increases the accuracy of measurement of the skin response when exposed to a person — the external electromagmitic field P1 $ of the industrial frequency.

and,

f l

 - Epidermis

 Vnu / t7 /) sheh / Kz

/ // //

J.

// ///

FIG. g

Fig.Z

Editor A. Kozoriz

Compiled by Y. Kochetkov Tehred O. Sopke

. Order 3635/6. Circulation 660 Subscription

VVIIPI USSR State Committee

Inventions and discoveries 113035, Moscow, Zh-35, Raushsk nab., 4/5

Production and printing company, Uzhgorod, st. Project, 4

Proofreader L. Patay

Claims (1)

METHOD OF MEASUREMENT, RESISTANCE. SKINS OF A BIOLOGICAL OBJECT by measuring the potential difference and current between active and inactive electrodes installed on a biological object, characterized in that, in order to eliminate the influence of an external electric field of industrial frequency, an inactive electrode is shielded, a current-receiving electrode is inserted over the active electrode and an electrode connecting biological object with zero bus, measure the potential difference and current between the active and current-receiving electrodes, then shield the current-receiving electrode and by changing aznosti potentials between the active and inactive electrodes and the current between the active and inactive electrodes determine the skin resistance. Yu