SU1544369A1 - Device for measuring equivalent parameters of electrode impedance - Google Patents

Abstract

The invention relates to medical technology and can be used to measure active and reactive resistances of electrodes, as well as to measure diagnostic parameters of a bioobject. The purpose of the invention is to simplify the design and improve the measurement accuracy by directly measuring the desired quantity. The signal from the low-frequency generator 1 is fed to the input of the voltage follower 6, the output signal from which is simultaneously fed to the electrodes 2 and 3 under study and to the adjustable potentiometer 10. The signal passed through the electrodes 2 and 3 is inverted in the inverter 7, the second adjustable potentiometer passes 11 and the phase shifter 8. The output signal of the phase shifter through the resistor 15 is summed with the signal having passed the adjustable potentiometer 10 at the inversion input of the adder 9. During the measurement process, at the selected frequency, the signal is obtained by Adjustable potentiometers 10 and 11 ensure that the output voltage of the adder becomes zero. The equivalent parameters of the electrodes are determined by the values of potentiometers 10 and 11, the resistance of the resistor 16, the capacitance of the capacitor 17, and the frequency of the suppressed signal. 1 Cp, 1 Il.

Description

The invention relates to medical equipment, namely to devices for studying the electrical parameters of electrodes used in sensors of medical equipment, in addition, can be used in devices for measuring diagnostic parameters of a biological object.

The purpose of the invention is to improve the accuracy of measurement.

The drawing shows an electrical diagram of a device for measuring equivalent parameters of the impedance of the electrodes.

The device contains an alternating current generator 1, electrodes 2 and 3, a biological object 4 impedance, a voltage meter 5 built on operational amplifiers, a voltage follower 6, an inverter 7, a phase shifter 8, and an adder 9, as well as two potentiometers 10 and 11, five resistors 12— 16 and capacitor 17.

The alternator 1 is connected 20 to the non-inverting input of the voltage follower 6, the output of which through the potentiometer 10 is connected to the inverting input of the adder 9. The output of the voltage follower 6 is connected through the electrode 2, impedance 4, electrode 3 with the inverter 7 inverting ^ 5 input. Inverter 7 output through a potentiometer 11 is connected to a non-inverting, and through a resistor 13 - to the inverting inputs of the phase shifter 8. The output of the phase shifter 8 is connected through a resistor 15 to the inverting input of the adder 9. Resistors 12, 14 and 16 are included respectively in the The negative feedback loop of inverter 7, phase shifter 8 and adder 9. Non-inverting inputs of inverter 7 and adder 9 are grounded, and non-inverting 35 input of phase shifter 8 is grounded through capacitor 17.

The device operates as follows.

The signal from the generator AC 1 (low frequency) is applied to neinver- ⁴⁰ 6 tiruyuschy input voltage repeater. The output signal from the voltage follower 6 is simultaneously supplied to the electrode 2 and to the potentiometer 10. The signal transmitted through the electrodes 2 and 3, as well as through the bio- ₄₅ object, is inverted in the inverter circuit 7. Then this signal passes through the potentiometer 11, phase shifter 8. The output the signal of the phase shifter 8 through the resistor 15 is summed with the output signal of the voltage follower 6 passed through the potentiometer 50 10 at the inverting input of the adder 9.

In case of equal resistance of the resistors 12 and 15, as well as the resistors 13 and 14, the voltage value of the output signal of the adder LU is connected with the voltage value of the input signal from the generator Shop ^{55 by the} equation

C o —itCT JRo_ Rot r g + pcs 'Z K /' ^and in, where L is the desired complex value of the resistance of the electrodes;

Ro is the resistance of the resistor 16;

Ri, R.2 — resistance of potentiometers 11 and 10;

C is the capacitance of the capacitor 17;

ω is the angular frequency of the signal.

In the process of measuring the parameters of the complex quantity L at a selected signal frequency, by adjusting the potentiometers 11 and 10, the output voltage is equal to zero.

Then the desired resistance

L = R ₂

1 — ίωτ

-j-ίωτ ’(2)

Solving equation (2), we obtain the corresponding values of the modulus of resistance | L |, the active and reactive component a and b of the resistance L and the angle of the phase shift between the active and reactive components | L | = R ₂ ;

- (ωτ) ² + (ωτ) ² '

2ωτ p2.

-j- (ojt) ' ^z '

R ₂

Thus, changing the frequency of the signal, we determine the equivalent parameters of the electrodes as a function of frequency.

In the process of each measurement, we obtain the total impedance of the two electrodes and the subcutaneous layer of the biological object. To obtain the equivalent value of each individual electrode, three pairs of electrodes are examined, which are connected in pairs to the indicated measurement circuit. The complex values of the impedances are determined for each pair of electrodes L, ₂ , Li3, L ₂ 3, which can be represented by a system of equations

Li 2 = L 1 -ph Ln -ph L ₂ ;

L13 = L1 + Lt 1-j-Lt ₂ + L3;

L ₂ s — L ₂ - | -Lt ₂ - | -L ₃ , where L |, L ₂ , L3 is the equivalent impedance of each electrode;

Ln, Lt ₂ - equivalent impedances of a biological object.

Considering that the impedance of the subcutaneous layer is two to three orders of magnitude lower than the impedance of the electrodes, we obtain the equivalent impedance parameters of each electrode under study by the formulas t L | ₂ - | -L | 3t-L23. .

^{L |} T '

L ₂ ^ = ^L 12-L | ₃ + ^L 23;

t - Li 2 - | - L1 s ~ | - L23 ³ 9>

(1)

Claims (2)

Claim 1. A device for measuring equivalent parameters of the impedance of the electrodes, containing an alternating current generator, two electrodes, a phase shifter made 5 on an operational amplifier, the non-inverting input of which is grounded through a capacitor, two potentiometers, a voltage meter and five resistors, characterized in that, in order to increase accuracy of measurement, a voltage follower, an inverter and an adder are introduced, while the alternator is connected through a non-inverting input of the voltage follower and the first potentiometer with nvertiruyuschim adder input, a noninverting input ¹⁵ Ko torogo grounded, and an output connected to a voltage meter furthermore dressings toritelya output voltage is connected through electrodes to the inverting input of the inverter, a non-inverting input of which is grounded and the output is connected via a first resistor to the inverting and by a second potentiometer with non-inverting inputs of the phase shifter, the output of which is connected through a second resistor to the inverting input of the adder, the third, fourth, and fifth resistors included in the circuit, respectively tritsatelnyh feedback inverter, phase shifter and an adder, and the inverting input of the voltage follower connected to its output. 2. The device according to π. 1, characterized in that the resistance values of the first and fourth, as well as the second and third resistors are equal to each other. Editor I. Shulla Zakash 449 Compiled by A. Dmitriev Tehred I. Veres Corrector A. Obrschar Circulation 546 Subscription VNIIIPI of the State Committee for Inventions and Discoveries at the State Committee for Science and Technology 113035, Moscow, Zh-35, Raushskaya nab., D. 4/5 Production and Publishing Plant "Patent", Uzhhorod, st. Gagarin. 101