SU1565481A1 - Device for measuring conduction of skin - Google Patents

Abstract

The invention relates to medical technology. To improve the accuracy of measuring the skin's conductivity, the device containing the first electrode 1 and the operational amplifier 5, the inverting input of which is connected to the output via a resistor 6 and the second electrode 2 directly, and the non-inverting input is connected to a common power supply bus, 4, a series-connected differential amplifier 7, a voltage-generating unit 8, an adjustable voltage source 9 and a switch 10. The output of the latter is connected to the electrode 1, while the electrodes 3,4 are connected to the inputs of the differential A power amplifier 7, the output of which is also connected to the second input of the adjustable voltage source 9, and the second output of the reference voltage generating unit 8 is connected to the control input of the switch. 2 Il.

Description

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The invention relates to medical technology, and more specifically to devices for measuring the electrical properties of the skin, and can be used in medicine and experimental psychology.

The purpose of the invention is to improve the accuracy of measuring the conductivity of the skin.

FIG. 1 is a block diagram of a device for measuring skin conductivity; in fig. 2 - time diagram of his work.

The device for measuring skin conductivity contains electrodes 1-4, an operational amplifier 5, a resistor 6, a differential amplifier 7, a reference voltage shaping unit 8, an adjustable voltage source 9 and a switch 10.

Pairs of electrodes 3 and 2, 4 are respectively in electrode housings 11 and 12 (Fig. 1), with electrode 2 connected to an inverting input of an operational amplifier 5, the non-inverting input of which is connected to a common power supply bus of the device. The output of the operational amplifier 5, which is simultaneously the output of the device, is connected to its inverting input via a resistor 6. The differential amplifier 7, the reference voltage shaping unit 8, the adjustable voltage source 9 and the switch 10 are connected in series. At the same time, the output of the key 10 is connected to the electrode 1. The electrodes 3 and 4 are connected to the inputs of the differential amplifier 7, the output of which is connected to the second input of the voltage source 9, and the second output of the block 8 forming the reference voltage is connected to the control input of the key 10. When Thereby, the reference voltage generation unit 8 consists of a control unit 13 and serially connected key element 14, a memory cell 15 and an adder 16. Moreover, the first output of control unit 13 is connected to the control input of the key element 14, and the second from second an input unit 8 for generating a reference voltage. The second input of the adder 16 is connected to a source of stabilized voltage, and the output is connected to the first output of the unit 8 for the formation of a reference voltage.

The control unit 13 is designed as an asymmetric generator with direct and inverse outputs. It provides two modes of operation of the device: mode 1 - measuring and storing the sum of the biopotential between the places of application of electrode housings 11 and 12 and the polarization potential of a pair of electrodes 3 and 4, mode 2 - generating a reference voltage, corrected by the magnitude of the parasitic potentials measured in one.

The unit 8 for the formation of the reference voltage provides a periodic measurement of the difference in biopotentials between the places of application of the electrode shells 11 and 12.

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5 (t).

and the polarization potential of the pair of electrodes 3, 4 and introduces the appropriate correction to the input of the adjustable voltage source 9. The adjustable voltage source 9 is made of a series-connected comparison unit 17 and an adjustable element 18, such as a transistor (Fig. 1).

It is advisable to set the stabilized voltage at the second input of the adder 16 to eliminate the effect on the measurement results of the nonlinear properties of the skin to 0.4-0.5 V.

A device for measuring the conductivity of the skin works as follows.

Before switching on the device, electrode shells 11 and 12 are installed on the skin, filled with an electrically conductive paste or liquid to stabilize the contact. When the device is turned on, the control unit 13 implements mode 1, the closure of the key element 14 and the key 10 opens. The voltage is not supplied to the electrodes 1 and 2, therefore the sum of the polarization potential of the pair of electrodes 3 and 4 is fed from the electrodes 3 and 4 to the input of the differential amplifier 7 - Ј34 and biopotential differences between the points of superposition of the electrodes of the housings. And and 12 - Ј / "" (Fig. 2). This sum of voltages is stored in memory cell 15 and is maintained for the first input of the adder 16 during the whole measurement cycle, the second input of which receives the stabilized voltage and.

After the time required for the sampling and memorization procedure (ten milliseconds) has elapsed, at time tm, the control unit 13 switches the device to mode 2 (Fig. 2). 5 For this, it opens the key element 14 and closes the key 10 As a result, a voltage is applied between electrodes 1 and 2, which creates some voltage and strain on the skin between electrode housings 11 and 12. This voltage is accurate to the sum of Ez4y), (t) is removed by electrodes 3 and 4 to the input of the differential amplifier 7, so that at its output and the first input of the adjustable voltage source 9 there is a voltage (/ «- M g) -f0

The second input of the voltage source 9 receives a voltage from the output of the adder 16, equal to (Utf + E34 (tol) (tai). The output voltage of the voltage source 9 through the switch 10 is supplied to the electrode 1 and is changed so that At the inputs of the source 9, the voltages were always equal. This is achieved subject to equality

Ј / “utr + {Ј34 (() +

+ Uwo-tf (“)

Thus, through the electrodes 1 and 2 flows the measuring current, independent

A power amplifier, the inverting input of which is connected to the second electrode directly, and through a resistor to its input, non-inverting to a zero bus, characterized in that, with the aim of post-polarization of electrodes 1 and 2, and equal to, where Y is the skin's conductivity. As a result, the output voltage of the device is

(JBln (UlOM RoC.) CC, SHPPP, W

and the measurement error of conductivity to determine the accuracy, the third one is introduced into it, the degree of compensation of the field of the vnz and fourth electrodes, the differential of electrodes 3 and 4, and the biopotential and amplifier, the reference unit

voltage, adjustable source Hanpflj and key, with the third and fourth S electrodes connected to the inputs of the differential amplifier, the output of the latter

equals

. Ј34 (fl-Ј34 (U, Ts (0-C (.)

O-, t g

f / crUCT

with the first input of the adjustable voltage source and with the input of the unit for the formation of the reference voltage, the first output of which is connected to the second input of the adjustable

The proposed device allows improving the accuracy of measuring the skin conductivity due to constant compensation of the polarization of the electrodes through which the skin

measurement current is supplied, and a periodic source of voltage, and the second output biopotential compensation, having a control input of the key, the output of the key

connected to the second electrode, with the first and fourth, second and third electrodes. - pairwise combined in two housings, an instrument for measuring the conductivity of the skin formation input 20, containing the first electrode, the operand of the adjustable voltage source

Regine 1

state on the skin between the places where the electrodes are applied.

Claims (1)

Invention Formula A power amplifier, the inverting input of which is connected to the second electrode directly, and through a resistor to its own input, non-inverting, to a zero bus, characterized in that higher accuracy, the third and fourth electrodes, the differential amplifier, the reference unit voltage, adjustable source Hanpflj and key, the third and fourth electrodes are connected to the inputs of the differential amplifier, the output of the latter with the first input of the adjustable voltage source and with the input of the unit for the formation of the reference voltage, the first output of which is connected to the second input of the adjustable voltage source, and the second output with a key control input, a key output