SU845823A1 - Device for examining electric characteristics of biological tissues - Google Patents

Description

This invention relates to a medical technique, in particular to devices for functional diagnostics. A device for studying the electrical characteristics of biological tissues, which contains a cell with potential, current and indifferent electrodes, is known, while the potential electrode is sequentially connected to a potential follower, a differential amplifier, and a current electrode, which registers a device connected to an indifferent electric current house, a generator of reference signals connected to the second input of the differential amplifier RD. The disadvantage of this device is the low accuracy of voltage stabilization at the object, which ultimately leads to low measurement accuracy, as well as to low resistance of the device. The stability of the device and the accuracy of voltage stabilization on an object are determined by both the electrical parameters of the device and the characteristics of the replaceable electrodes. During measurements, the electrode resistance varies, the condition of critical attenuation is violated, and the device can go into a self-oscillating press, which usually leads to damage to the biological object. When operating in a mode far from the critical attenuation, the accuracy of tracking the command signal decreases. In addition, in order to ensure high accuracy of the voltage stabilization on the object, the magnitude of the gain factor of the QTp MEATS device. I increase, and since the output operational amplifiers on the device are built, the gain decreases with increasing amplitude-frequency characteristic this leads to a decrease in the stability of the device, speed of the device

consequently, the reduction and accuracy of measurement of the electrical parameters of the object.

The purpose of the invention is to increase the stability and accuracy of measurements. The goal is achieved by introducing a voltage-current converter into the device, the input of which is connected to the output of the differential amplifier and the output to the TOKoi electrode.

The drawing shows a block diagram of a device for studying the electrical characteristics of biological tissues.

The device contains a cell 1 with potentiating electrodes 2, a current electrode 3, an indifferent electrode 4, a potential repeater 5 whose inputs are connected to potential electrodes, a differential amplifier 6, a voltage-current converter 7 whose output is connected to a current electrode, a generator 8 of the reference voltage the voltage registering device 9 and the current registering device 10. The output of the repeater 5 potential is connected to the recording device 9 and the first input of the differential amplifier 6 ,. The second input of the differential amplifier. 6 is connected to the generator 8, and the output from the registered current device 10 and the input of the converter 7 and terminals. The indifferent electrode 4 is grounded.

The device works as follows.

A cell filled with a conductive saline solution is placed in a biological object (a nervous cell or some other cell, and through the semipermeable membrane bounding cell, potential and current 1 {electrodes 2 and 3 are introduced into it). current, forming a potential difference across the cell membrane, which is measured by the potential repeater 5. The measurement result is fed to a recording device 9 and one of the inputs of the differential amplifier 6, the second input of which is the signal from the generator 8 fails. The error voltage (the difference between the membrane voltage and the reference voltage), amplified by the differential amplifier 6, is fed to the recording device IO

current and voltage-to-current converter 7, which, with a conversion factor, converts the voltage supplied to its current into a current passing through the current electrode 3, the membrane of the biological object and the indifferent electrode 4, and this current proportional to the error signal is not depends on the electrical parameters of the current electrode and the biological object.

The differential equation, to which the measurement process performed by the device obeys, makes it possible to evaluate the features of the device in terms of stability, speed and accuracy of measurement of object parameters. Calculations performed by a known method lead to the following expression

(: t: t /% Vu c) c-4.c

where W is the transmission coefficient of the device. constant voltage time C; ., s are constant time biological

whom object;

 - membrane resistance; 6iv) - membrane capacity; US room signal; VM voltage on the membrane.

f m

where O / is the voltage-current conversion ratio.

Therefore, the critical damping condition for the described device

t Л y 4 К AKoC.

f l l V A tX Jt JI

C2.)

In the device, the accuracy of tracing the command signal by the membrane depends on the product of K. oC and the accuracy can be increased by increasing the conversion coefficient (L-voltage-to-current, the value of which does not depend on f.) As follows from equation (.2) improving the accuracy of the device, but also expanding the frequency range of the signals, for which the criterion of critical closure is fulfilled, i.e. performance.

Claims (1)

Claim ROD and VaUystroit for the study of the electrical characteristics of biological tissues, containing a series-connected cell, potential electrodes, a potential repeater and a differential amplifier, a voltage reference generator, a current electron; and current recording devices; voltages, characterized in that, in order to increase the stability! the accuracy and accuracy of measurement, a voltage converter is introduced into it, the input of which is connected to the output of the differential amplifier, and the output to the current electrode. B—