SU1422184A1 - Impedance to voltage converter - Google Patents

Abstract

The invention relates to electrical measurements, in particular, to measuring impedance measurements, and can be used to measure the deviation of the impedance modulus from a predetermined value. The purpose of the invention is to improve the accuracy of the conversion of the impedance into a voltage. The converter contains an alternating current source 1, a current transformer 2, amplifiers 3 and 4, a voltage transformer 5, reference impedances 6.7 and 8, a converted impedance 9. The converter converts into a voltage the value of the relative change of the impedance modulus, which and provides an increase in conversion accuracy with small deviations of the impedance from its nominal value. 1 il. 6 (/

Description

U li

tc

NS

The invention relates to electrical measurements, in particular to impedance meters, can (be used to measure from 1 the deviation of the impedance modulus from a given value and is an improvement of the invention according to Aut. No. 1269052.

The purpose of the invention is to increase the precision; the complex transformation of the resistance to voltage.

The drawing shows the functional diagram of the impedance-to-voltage converter. 15

The converter contains a source; 1 alternating voltage, current transformer 2, first 3 and second 4 aspirators, voltage transformer 5, first 6, second 7 and third 8 sample impedances, converted impedance 9. First output of source 1 AC voltage through the first winding of the current transformer 2 and the converted 25 impedance 9 is connected to the input of the second amplifier 4. The second (anti-phase) output of the alternating voltage source 1 is through the fourth winding of the current transformer 2 and 30 The reference impedance impedance 8 is also connected to the input of the second amplifier 4. The second and third windings of the current transformer 2 are connected counter, and their common point .35 is connected to the common bus, the output of the second winding is connected to the input of the first amplifier 3, and the output of the third winding The first exemplary impedance 6 is connected to the output 40 of the first amplifier 3. The output of the latter through the first winding of the voltage transformer 5 is connected to the output of the converter, which through the second exemplary impedance 45 s 7 is connected to the input of the second amplifier 4. The yield of the latter through a second winding of the transformer 5, the voltage coupled to the common bus.

The Converter operates as follows.

The output voltage of the transducer is defined as the difference of the two voltages created by the antiphase 55

mi currents flowing tsovoy 8 and convertible resistances:

and and - and.

,

Yu

15

20 25 30 .35 about 40 about 5 45

m

e 55

where and is the output voltage of the converter, proportional to the converted impedance 9 (2); and is the output voltage of the converter, proportional to the model complex impedance 8 (2),

and; and, + (1) U2; and z; (1) u,

where il is the error in summing the output voltages of the first and second amplifiers due to the presence of a transformer 5. Under the CONDITION that the input impedance of amplifiers 3 and 4 is infinite and the output impedance is zero, the gain factors are equal to K, the currents flowing through the converted 9, first 6 and second 7 exemplary complex resistances are described respectively by the expressions

1, (and + and / K) / Z ,; 1 (and; + and; / K)

il (and - and; / K) 7z ,,

(where Zo, Zo exemplary complex

resistances 6 and 7, respectively; Ufl - source voltage 1.

. Learning that 0, 1 + + (, O and Z Z, get the system of equations

r (K + l) K.Z, .U; KZX I (Z, + Zp) U + -K. ,,;

l i Uz - 0 The solution of this system with respect to the output voltage U is

 - 1: -k1 --to% where b Z / (Zv + Zo).

The expression for U, obtained similarly, has the form

and - and - (1 ---

where X (Z + Zo).

Converter Output Voltage

and -and --P

 Z / KV

where & Z Z -

A

uZ

ZM Z /

As follows from the expression for you hard voltage converter, it performs the conversion to

the voltage of the relative change in the modulus of the impedance dZ / Z, i, which provides an increase in the accuracy of conversion with small deviations of the impedance Z from its nominal value Z ... . -.

For rm ulyz re te

Converter impedance to voltage according to auth.St. No. 1269052, characterized in that, in order to increase the conversion accuracy, a third exemplary impedance is introduced into it, the alternating voltage source is up to, fully equipped with an anti-phase output, and the current transformer is the fourth winding, and the alternating output of the alternating voltage source through the fourth winding of the current transformer and the third exemplary impedance is connected to the input of the second amplifier.

Editor I.Gorn

Compiled by, Makrimeno

Tehred L. Oliynyk Proofreader S. Cherni

Order 4427/46

Circulation 772

VNIIPI USSR State Committee

for inventions and discoveries 113035, Moscow, Zh-35, Rauschska nab., 4/5

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Claims (1)

Form u l iz about otreteniya Converter of complex resistance to voltage according to autosw. g If 1269052, characterized in that, in order to increase the conversion accuracy, a third exemplary complex resistance is introduced into it, the alternating voltage source up to IQ is equipped with an antiphase output, and the current transformer has a fourth winding, the antiphase output of the alternating voltage source through the fourth winding of the transformer · * 15 current matrices and a third exemplary complex resistance connected to the input of the second amplifier.