RU2174688C1 - Method for measuring separate parameters of n- element two-terminal networks by means of multiple-port transformer bridge - Google Patents

Abstract

FIELD: electric measurement technology. SUBSTANCE: method involves separate measurement of parameters by reading out turn number in frequency- independent state of transformer bridge equilibrium. Supply voltage across comparison port is measured at preset frequency like quotient of complex admittance of measurement port and complex admittance of comparison port. To this end turn number of adjustable ratio ports is calculated using turn-number readings taken from two additional adjustable ratio ports. A number of repeated balances of bridge are made at preset measurement frequencies and also with respect to its active and reactive components relative to supply voltage across measurement port obtained during preceding set of repeated balances. Parameters being measured are separately read out in terms of turn number of main adjustable ratio ports. EFFECT: enhanced measurement accuracy. 1 dwg

Description

 The invention relates to electrical engineering, and in particular, to bridge methods for measuring alternating current parameters of n-element bipolar circuits, the equivalent circuit of which consists of parallel connected branches.

There is a method of separate measurement of the parameters of n-element two-terminal networks with an alternating current bridge (see AS N 158627 (USSR), MKI ² G 01 R 27/02, B.I. N 22, 1963), on which the bridge is fed from the oscillating frequency generator. According to the angle and width of the ellipse that appears when the frequency sways on the screen of the oscilloscope, included in the measuring diagonal of the bridge according to the phase-sensitive circuit, a series of repeated balancing of the bridge at a given frequency is carried out by adjusting two parameters. Upon reaching a frequency-independent state of equilibrium, a separate reading of the measured parameters is made according to the values of the adjustable parameters of the n-element comparison arm, made according to the scheme of the measured two-terminal device. The disadvantage of this method, selected as an analogue, is the low accuracy of the measurement due to the very large threshold of sensitivity of the broadband null indicator, which is the marked oscilloscope for observing the ellipse when the frequency swings. Another disadvantage of the analogue is the significant limitation of its functionality. This is due to a complex and lengthy process of balancing with respect to n adjustable parameters, since already for n = 3 there is no unequivocal correspondence between the angle of inclination of the ellipse on the screen and the sign of the deviation of the parameter of the three-element comparison arm adjustable for this ellipse. For n> 3, frequency-independent equilibrium of the bridge is extremely difficult.

Known for the selected prototype method for separate measurement of the parameters of n-element two-terminal networks by an alternating current bridge along a. from. N 1599803 (USSR), MKI ⁵ G 01 R 27/02, B.I. N 38, 1990, consisting of two stages. At the first stage of the method, a series of balancing of the bridge is carried out at n / 2 given frequencies, if the number n of measured parameters is even, and at (n + 1) / 2 frequencies, if n is an odd number, the active and reactive values are measured by adjusting two additional parameters of the comparison arm components of the impedance of the measurement arm, calculate the parameters of an exemplary bipolar. At the second stage of the method, a series of repeated balancing of the bridge with the said exemplary two-terminal device is carried out in the comparison arm by adjusting the marked two additional parameters of this arm at given frequencies. Before each next series of repeated balancing of the bridge, the parameters of the model two-terminal are set, which are calculated from the readings of the above two additional adjustable parameters, as well as the values of the active and reactive components of the impedance of the model two-terminal at the previous balancing. A series of repeated equilibrations is carried out until a zero-amplitude selective zero indicator is obtained at the specified measurement frequencies at zero values of the additional parameters of the comparison arm.

 The disadvantage of the prototype is that on it a separate reading of the measured n parameters is carried out according to the values of the main parameters of n adjustable resistors and capacitors, from which an exemplary two-terminal device is assembled according to the equivalent circuit of the measurement object. The residual parameters of these adjustable resistors and capacitors, the parasitic capacitance of the switching elements with which to establish the calculated values of the parameters of the model bipolar, as well as the leakage capacitance between the internal nodes of the circuit of the model bipolar and its earthed screen are sources of measurement error, protection against which the bridge realizes the measurement by prototype, as well as accounting for which when conducting calculations is very complicated. The specified disadvantage of the prototype can significantly limit the accuracy of the measurement of the parameters of n-element two-terminal networks by the bridge method.

 The essence of the invention is to improve the accuracy of measuring the parameters of an n-element bipolar by separately counting them by the number of turns in a frequency-independent equilibrium state of a multi-arm transformer bridge.

This technical result in the implementation of the invention is achieved in the known a. from. N 1599803 a method for separately measuring the parameters of an n-element two-terminal network using a multi-arm transformer bridge, containing balancing operations in common-mode power supply of the comparison arms and measuring, by adjusting the number of turns of two additional arms, the ratio of this bridge with a convergence angle of 90 ^o to them at n / 2, if the number n of the measured parameters is even, and at (n + 1) / 2 frequencies, if n is odd, followed by a series of repeated balancing adjustments of the number of turns of the marked two additional arms of the ratio d about getting their zero values.

 The peculiarity lies in the fact that before each series of repeated balancing, the supply voltage of the comparison arm is formed, varying with frequency, similar to the quotient of dividing the complex conductivity of the measurement arm by the complex conductivity of the comparison arm, by setting the number of turns n of the adjustable main arms of the ratio, which is calculated by the active and its reactive components relative to the supply voltage of the measuring arm and according to the counts of the number of turns of the two adjustable additional arms n of the previous series of repeated balancing, and a separate reading of the measured parameters is carried out by the number of turns of the specified n adjustable main arms of the ratio of the bridge.

 The analysis of the prior art by the applicants, including a search by patent and scientific and technical sources of information containing information about analogues of the claimed invention, allowed us to establish that the applicants did not find a source characterized by features identical to all the essential features of the claimed invention. The definition from the list of identified analogues of the prototype, as the closest in the totality of the features of the analogue, allowed us to establish a set of essential distinguishing features in relation to the technical result perceived by the applicants in the claimed method set forth in the claims.

 Therefore, the claimed invention meets the condition of "novelty."

To verify the compliance of the claimed invention with the condition "inventive step", the applicants conducted an additional search for known solutions in order to identify features that match the distinctive features of the claimed method from the prototype. The search results showed that the claimed invention does not follow explicitly from the prior art for the specialist, since the influence of the transformations provided for by the essential features of the claimed invention has not been revealed from the prior art determined by the essential features of the claimed invention, in particular the claimed invention does not provide for the following transformations:
the addition of the known method by any known part, attached to it according to known rules, to achieve a technical result, in respect of which the effect of such an addition is established;
the creation of a method consisting of known parts, the choice of which and the relationship between them are based on known rules, recommendations, and the technical result achieved in this case is due only to the known properties of the parts of this method and the relationships between them.

 The described invention is not based on a change in a quantitative sign (s), the presentation of such signs in relationship or a change in its type, we mean the case when a known fact of the influence of each of these signs on the technical result, new values of these signs or their relationship could be obtained on the basis of from known dependencies, patterns.

 Therefore, the claimed method meets the condition of "inventive step".

The drawing shows a diagram of a multi-arm transformer bridge that implements the claimed method in the case of measuring the parameters of a two-terminal network consisting of parallel connected branches and therefore described by the complex conductivity Y _x .

перестраиваемой частоты, подключенный к зажиму 13 первичной обмотки w_г основного трансформатора 1; 14 и 15 - зажимы плеча измерения 2, которыми оно подключено к выходу вторичной обмотки w₂ основного трансформатора 1 и ко входу первичной обмотки l₂ компаратора 4; 16, 17 - входной, выходной зажимы плеча сравнения 3; 18 - выходной зажим сумматора 10; 19 - входной зажим сумматора 10, к которому подключена обмотка w₁ основного трансформатора 1; 20, 21 - входные зажимы сумматора 10, подсоединенные к выходам операционных усилителей ОУ1, ОУ2, нагруженных на первичные обмотки m трансформаторов 6, 8; 22 - избирательный амплитудный нуль-индикатор, настраиваемый на заданные частоты измерения. На чертеже также обозначены: w₁, p₁, q₁, p₂, q₂ - регулируемые основные плечи отношения моста, являющиеся обмотками трансформаторов напряжения 1, 6, 7, 8, 9 в схеме формирователя напряжения 5; l₃, l₄ - регулируемые дополнительные плечи отношения моста, являющиеся обмотками компаратора токов 4 и имеющие заземленную среднюю точку; w₂, w₅, m, l₁, l₂ - нерегулируемые основные плечи отношения моста, являющиеся обмотками трансформаторов 1, 6, 7, 8, 9 и компаратора 4; w_п - нерегулируемое вспомогательное плечо отношения моста, являющееся вторичной обмоткой трансформатора 1, используемой для питания ветви с обмоткой l₁ компаратора 4 в положении "П" переключателя 11; w₃, w₄ - нерегулируемые дополнительные плечи отношения моста, являющиеся вторичными обмотками трансформатора 1;

- токи плеч соответственно сравнения, измерения и дополнительных плеч отношения l₃, l₄;

- ток, проходящий через индикатор 22; R₃, C₄ - образцовые резистор и конденсатор в цепях дополнительных плеч отношения l₃, l₄.The drawing indicates: 1 - the main transformer, equipped with a primary winding w _g and six secondary windings w _P , w ₁ - w ₅ ; 2 - a measuring arm with a measured five-element bipolar, the circuit of which contains a parallel connected single-element branch with a capacitor C _0x and two two-element branches with resistors R _1x , R _2x with a series of capacitors C _1x , C _2x ; 3 - a shoulder of comparison with an exemplary constant measure of capacity C _N ; 4 - current comparator with four primary windings l ₁ -l ₄ and indicator winding l _And ; 5 - voltage shaper, composed of secondary windings w ₅ , w _{1 of the} main transformer 1, the first of which is connected to the operational resistors R1, OU2 through reference resistors R ₅ , the feedback circuits of which contain voltage transformers 6, 7, 8, 9 and exemplary resistor R, capacitor C, and a precision voltage combiner 10, based on the operational amplifier OUZ and four exemplary resistors r, is connected to the second of which is connected to the outputs of the mentioned operational amplifiers; 11 - switch to two positions: "P" and "B"; 12 - grounded source of sinusoidal voltage

tunable frequency connected to terminal 13 of the primary winding w _{g of the} main transformer 1; 14 and 15 - clamps of the shoulder of measurement 2, by which it is connected to the output of the secondary winding w _{2 of the} main transformer 1 and to the input of the primary winding l _{2 of the} comparator 4; 16, 17 - input, output clips of the shoulder comparison 3; 18 - output clamp of the adder 10; 19 - input terminal of the adder 10, to which the winding w _{1 of the} main transformer 1 is connected; 20, 21 - input terminals of the adder 10 connected to the outputs of the operational amplifiers ОУ1, ОУ2, loaded on the primary windings of m transformers 6, 8; 22 - selective amplitude null indicator, tunable to specified measurement frequencies. The drawing also shows: w ₁ , p ₁ , q ₁ , p ₂ , q ₂ - adjustable main shoulders of the bridge relationship, which are the windings of voltage transformers 1, 6, 7, 8, 9 in the voltage shaper circuit 5; l ₃ , l ₄ - adjustable additional shoulders of the bridge relationship, which are the windings of the current comparator 4 and having a grounded midpoint; w ₂ , w ₅ , m, l ₁ , l ₂ - unregulated main shoulders of the bridge relationship, which are windings of transformers 1, 6, 7, 8, 9 and comparator 4; w _p - unregulated auxiliary arm of the ratio of the bridge, which is the secondary winding of the transformer 1, used to power the branches with winding l _{1 of the} comparator 4 in position "P" of the switch 11; w ₃ , w ₄ - unregulated additional shoulders of the relationship of the bridge, which are the secondary windings of the transformer 1;

- currents of the shoulders, respectively, comparisons, measurements and additional shoulders relations l ₃ , l ₄ ;

- the current passing through the indicator 22; R ₃ , C ₄ - exemplary resistor and capacitor in the circuits of additional arms of the ratio l ₃ , l ₄ .

The voltage transformers 1, 6, 7, 8, 9, the current comparator 4 are made with close inductive coupling between their grounded windings and are considered ideal, that is, as having negligible active resistances and windings scattering inductances. To fulfill this condition, the voltage from the secondary windings of the transformers 1, 6, 7, 8, 9 can be removed through accurate voltage followers with a negligible output resistance, and the amplitude zero indicator 22 connected to the indicator winding l _And is taken with a sufficiently small input resistance . It is considered as an ideal voltage combiner 10, that is, as having a sufficiently large input impedance at its inputs 19, 20, 21 and a negligible output impedance from the side of the clamp 18. To fulfill this condition, exact voltage followers in its input circuits can also be used and output circuit. In the application, resistance and capacitance measures are considered ideal, since their residual parameters in a multi-arm transformer bridge are easily compensated. They are considered as ideal operational amplifiers OU1, OU2, that is, as having sufficiently large input impedance, gain and a sufficiently small output impedance.

В уравнении (1) ток плеча измерения 2 равен

где измеряемая комплексная проводимость записывается как

В уравнении (1) ток плеча сравнения 3 равен

где подводимое в положении "В" переключателя 11 к плечу сравнения 3 выходное напряжение формирователя 5

представляет собой произведение э.д.с. одного витка

/w_г трансформатора 1 на передаточную функцию формирователя 5

В дробно-рациональной функции (6) коэффициенты перед степенями переменной jω следующие:
A₀ = w₁ + T(p₁ + p₂); (7)
A₁ = w₁(τ₁+τ₂)+p₁Tτ₂+p₂Tτ₁; (8)
A₂ = w₁τ₁τ₂; (9)
B₂ = τ₁τ₂ ; (10)
B₁ = τ₁+τ₂ ; (11)
причем
T = Rw₅/R₅m; (12)
τ₁ = p₁q₁CR/m²; (13)
τ₂ = p₂q₂CR/m². (14)
По достижении для моста (чертеж) частотно-независимого равенства (1) при значениях l₃=0 и l₄=0 производят отсчет измеряемых параметров двухполюсника 2 по формулам
C_0x = (l₁C_N/l₂w₂)w_1,0; (15)

Как следует из выражений (1), (2), (4), в измерительном состоянии моста (чертеж) передаточная функция формирователя 5 равна

и, следовательно, пропорциональна отношению комплексной проводимости плеча измерения 2 к комплексной проводимости плеча сравнения 3.The measuring state of the bridge (drawing) according to the claimed method is frequency-independent and is described at zero values of the number of turns l ₃ = 0 and l ₄ = 0 of the adjustable additional arms of the ratio l ₃ , l _{4 by the} following equation of magneto-moving forces (ppm .) comparator 4:

In equation (1), the arm current of measurement 2 is

where the measured complex conductivity is written as

In equation (1), the current of the comparison arm 3 is

where the output voltage of the shaper 5 brought in in position "B" of the switch 11 to the comparison arm 3

is a work of emf one turn

/ w _{g of} transformer 1 to the transfer function of the shaper 5

In the fractional rational function (6), the coefficients before the powers of the variable jω are as follows:
A ₀ = w ₁ + T (p ₁ + p ₂ ); (7)
A ₁ = w ₁ (τ ₁ + τ ₂ ) + p ₁ Tτ ₂ + p ₂ Tτ ₁ ; (8)
A ₂ = w ₁ τ ₁ τ ₂ ; (9)
B ₂ = τ ₁ τ ₂ ; (10)
B ₁ = τ ₁ + τ ₂ ; (eleven)
moreover
T = Rw ₅ / R ₅ m; (12)
τ ₁ = p ₁ q ₁ CR / m ² ; (thirteen)
τ ₂ = p ₂ q ₂ CR / m ² . (14)
Upon reaching the frequency-independent equality (1) for the bridge (drawing) with values l ₃ = 0 and l ₄ = 0, the measured parameters of the two-terminal 2 are counted according to the formulas
C _0x = (l ₁ C _N / l ₂ w ₂ ) w _1.0 ; (fifteen)

As follows from the expressions (1), (2), (4), in the measuring state of the bridge (drawing), the transfer function of the shaper 5 is

and therefore proportional to the ratio of the complex conductivity of the shoulder of measurement 2 to the complex conductivity of the shoulder of comparison 3.

(где τ_1x = R_1xC_1x; τ_2x = R_2xC_2x) изменяется с частотой таким же образом, как и напряжение формирователя 5, описываемое формулой (5), поскольку оно может быть представлено как

где коэффициенты
a₀ = (C_0x + C_1x + C_2x)/C_N; (23)
a₁ = [C_0x(τ_1x+τ_2x)+C_1xτ_2x+C_2xτ_1x]/C_N; (24)
a₂ = (C_0x/C_N)τ_1xτ_2x; (25)
b₂ = τ_1xτ_2x ; (26)
b₁ = τ_1x+τ_2x , (27)
т.е. той же функцией, что и передаточная функция (6) формирователя 5.The ratio of the indicated conductivities

(where τ _1x = R _1x C _1x ; τ _2x = R _2x C _2x ) changes with frequency in the same way as the voltage of the shaper 5 described by formula (5), since it can be represented as

where are the coefficients
a ₀ = (C _0x + C _1x + C _2x ) / C _N ; (23)
a ₁ = [C _0x (τ _1x + τ _2x ) + C _1x τ _2x + C _2x τ _1x ] / C _N ; (24)
a ₂ = (C _0x / C _N ) τ _1x τ _2x ; (25)
b ₂ = τ _1x τ _2x ; (26)
b ₁ = τ _1x + τ _2x , (27)
those. the same function as the transfer function (6) of the shaper 5.

 The measurement according to the claimed method of the parameters of a two-terminal 2 using a bridge (drawing) is carried out in two stages.

снимаемым со вторичной обмотки w_П трансформатора 1, как и напряжение питания плеча измерения 2, подключенного ко вторичной обмотке w₂ трансформатора 1.The first stage of the measurement procedure is carried out, as in the prototype, with the common-mode power supply of the measurement arm 2 and the comparison arm 3. For this, the switch is set to position “P” and the comparison arm 3 is energized

removed from the secondary winding w _{P of the} transformer 1, as well as the supply voltage of the measuring arm 2 connected to the secondary winding w _{2 of the} transformer 1.

где токи плеча сравнения и измерения равны соответственно:

Токи

в равенствах (29) определяются по формулам

Ток индикатора

имеет место в равенствах (29) из-за влияния высших гармоник на показания нуль-индикатора 22.By adjusting the number of turns l ₃ , l ₄ carry out balancing of the bridge (drawing) at l measurement frequencies. At each of the given frequencies, equilibrium of the bridge is achieved with the sensitivity threshold of the null indicator 22 as low as possible, i.e., frequency-dependent equalities are established:

where the currents of the shoulder of comparison and measurement are equal, respectively:

Toki

in equalities (29) are determined by the formulas

Indicator current

takes place in equalities (29) due to the influence of higher harmonics on the readings of the zero indicator 22.

и определяют коэффициенты перед степенями полиномов дробно-рациональной функции F(jω ).According to the obtained counts of the numbers of turns l _3i , l _4i make up a system of 2l equations based on equalities
F _P (jω _i ) = α _i + jω _i β _i , (34)
Where

and determine the coefficients in front of the powers of the polynomials of the fractional rational function F (jω).

где значения (см. (35), (36)) α₁, β₁, α₂, β₂, α₃, β₃ соответствуют частотам ω₁, ω₂, ω₃ и отсчетам l_3i, l_4i на этих частотах, а коэффициенты B₂, B₁, A₂, A₁, A₀ соответствуют выражению (6).In the case of measuring the parameters of a five-element bipolar (drawing), this system has the form

where the values (see (35), (36)) α ₁ , β ₁ , α ₂ , β ₂ , α ₃ , β ₃ correspond to frequencies ω ₁ , ω ₂ , ω ₃ and samples l _3i , l _4i at these frequencies , and the coefficients B ₂ , B ₁ , A ₂ , A ₁ , A ₀ correspond to expression (6).

По найденным коэффициентам В₂, B₁, A₁, A₂, A₀ далее вычисляют числа витков регулируемых основных плеч отношения моста (чертеж) по формулам:
w_1,0 = A₂/B₂; (43)
p_1,0 = (A₁ - A₀τ₁ - w_1,0τ₂)/T(τ₂ - τ₁); (44)
p_2,0 = [(A₀ - w_1,0)/T]-p_1,0; (45)
q_1,0 = τ₁m²/CRp_2,0; (46)
q_2,0 = τ₂m²/CRp_2,0; (47)
где

τ₂ = B₁ - τ₁; (49)
T = w₅R/R₅m. (50)
Вычисленные в конце первого этапа числа витков регулируемых основных плеч отношения соответствуют значениям параметров измеряемого двухполюсника недостаточно точно, поскольку найдены они на основе равенств м.д.с. (29), содержащих в правой части ток индикаторной обмотки

Для обеспечения высокой точности измерения по заявленному способу, как и по прототипу, проводят второй этап измерения.The solutions of system (37) are as follows:

According to the found coefficients B ₂ , B ₁ , A ₁ , A ₂ , A _0, then the number of turns of the adjustable main arms of the ratio of the bridge (drawing) is calculated by the formulas:
w _1.0 = A ₂ / B ₂ ; (43)
p _1,0 = (A ₁ - A ₀ τ ₁ - w _1,0 τ ₂ ) / T (τ ₂ - τ ₁ ); (44)
p _2.0 = [(A ₀ - w _1.0 ) / T] -p _1.0 ; (45)
q _1.0 = τ ₁ m ² / CRp _2.0 ; (46)
q _2.0 = τ ₂ m ² / CRp _2.0 ; (47)
Where

τ ₂ = B ₁ - τ ₁ ; (49)
T = w ₅ R / R ₅ m. (fifty)
The ratios calculated at the end of the first stage of the number of turns of the main arms do not correspond to the values of the parameters of the measured two-terminal, since they are found on the basis of the equalities (29), containing on the right side the current of the indicator winding

To ensure high accuracy of the measurement according to the claimed method, as well as the prototype, carry out the second stage of measurement.

подводимое к плечу сравнения 3 с помещенной в него постоянной мерой емкости C_N (см. чертеж), изменяющееся в функции частоты в первом приближении так же, как частное от деления комплексной проводимости плеча измерения на комплексную проводимость плеча сравнения, то есть как Y_x = (jω)/jωC_N, в отличие от прототипа, по которому и на втором этапе напряжения питания плеч сравнения и измерения синфазны друг другу при одном и том же отношении их модулей на всех частотах измерения.The second stage proceeds as follows. The bridge switch 11 (drawing) is moved to position "B" and the number of turns of the adjustable windings of the shaper 5 found at the end of the first stage is installed. Thereby, a voltage is generated

applied to the comparison arm 3 with a constant measure of capacitance C _N placed in it (see the drawing), changing as a function of frequency as a first approximation, as well as the quotient of dividing the complex conductivity of the measurement arm by the complex conductivity of the comparison arm, that is, as Y _x = (jω) / jωC _N , in contrast to the prototype, according to which, at the second stage, the supply voltages of the comparison and measurement arms are in phase with each other with the same ratio of their modules at all measurement frequencies.

По получении l равенств (52) проводят уточнение передаточной функции формирователя 5 путем решения системы из 2l уравнений на основе равенств
F_y(jω_i) = α_iy+jω_iβ_iy, (53)
в которых в случае моста (чертеж)

где F_п(jω) - передаточная функция формирователя 5, найденная на первом этапе.Then, by adjusting the additional shoulders, the relations l ₃ = var, l ₄ = var at frequencies ω _i balance the bridge, obtaining equalities comparator 4

Upon receipt of l equalities (52), the transfer function of the shaper 5 is refined by solving a system of 2l equations based on equalities
F _y (jω _i ) = α _iy + jω _i β _iy , (53)
in which in the case of a bridge (drawing)

where F _p (jω) is the transfer function of the shaper 5, found in the first stage.

изменяется в первом приближении так же, как м.д.с. обмотки l₂, равная

и благодаря применению избирательного амплитудного нуль-индикатора 22 на каждой из l частот измерения регулировками l₃ = var, l₄ = var мост (чертеж) уравновешивается полностью. Вследствие этого система из 2l уравнений для определения передаточной функции F_y(jω) формирователя 5 является существенно более точной, чем на первом этапе.The refinement of the transfer function is achieved due to the fact that equalities (52), in contrast to equalities (29) obtained at the first stage, do not contain p.m. indicator winding, since already at the first stage of the second stage winding l ₁ equal

varies as a first approximation in the same way as ppm winding l ₂ equal

and due to the use of selective amplitude null indicator 22 at each of l measurement frequencies by adjustments l ₃ = var, l ₄ = var the bridge (drawing) is fully balanced. As a result, a system of 2l equations for determining the transfer function F _y (jω) of the shaper 5 is significantly more accurate than in the first stage.

Установив уточненное напряжение формирователя 5, проводят проверку состояния равновесия моста (чертеж) на заданных частотах ω_i при нулевых значениях чисел витков дополнительных регулируемых плеч отношения l₃ = 0 и l₄ = 0.In the case of a bridge (drawing) for measuring the parameters of a five-element bipolar 2, solving the system (37), find the adjusted coefficients В ₂ , В ₁ , A ₁ , A ₂ , A ₀ . From them find the specified number of turns w _1,0 ; p _1.0 ; q _1.0 ; p _2.0 ; q _2.0 . Set these numbers of turns and thereby specify the updated transfer function F _y (jω), and with it form the updated voltage of the shaper 5 in accordance with the expression

Having established the specified voltage of the shaper 5, the equilibrium state of the bridge (drawing) is checked at the given frequencies ω _i at zero values of the number of turns of the additional adjustable arms of the ratio l ₃ = 0 and l ₄ = 0.

 If when checking at the maximum sensitivity of the amplitude null indicator 22 at all frequencies the bridge (drawing) is balanced, then the measured parameters are counted according to formulas (15) - (19), that is, in contrast to the prototype, according to the number of turns.

индикаторной обмотки, то второй этап повторяют.If, when checking at least one of the frequencies, the amplitude null indicator 22 will show the presence of ppm.

indicator winding, then the second stage is repeated.

The second stage is completed when the frequency-independent equilibrium state of the bridge is reached (drawing) at zero numbers of turns of the additional arms, the relations l ₃ , l _{4 by a} separate reading of the measured parameters according to formulas (15) - (19).

 Thus, in the bridge (drawing), by generating the supply voltage of the comparison arm 3, varying with frequency, similar to the quotient of dividing the complex conductivity of the measurement arm 2 by the complex conductivity of the comparison arm 3, the essence of the claimed measurement method is achieved, which consists in increasing accuracy by, unlike prototype, separate readout of measured parameters by the number of turns of the adjustable windings of the multi-arm transformer bridge in a frequency-independent state of equilibrium.

 Higher measurement accuracy compared to the prototype is also achieved through the use of a "clean" measure of capacitance included in a single-element comparison arm, that is, a constant measure of capacitance, the residual parameters of which at given measurement frequencies in a multi-arm transformer bridge are easily compensated.

 The number of series of repeated balancing of the bridge (drawing) is small, because already the first of them is carried out in a bridge state close to frequency-independent, and ends with the receipt of exact equalities current comparator (see (52)), found on the basis of which the values of the measured parameters quickly approach true values as such series repeat.

Each of the balancing in two parameters at the measurement frequencies in these series is carried out under optimal conditions of convergence (the balancing lines at l ₃ = var, l ₄ = var are orthogonal straight lines) and for small ranges of variation in the number of turns of the additional arms of the ratio l ₃ , l ₄ relative to their zero values, i.e. It is carried out for several steps of balancing and can easily be automated.

 Therefore, the claimed method, like the prototype, is characterized by a short measurement time, as well as the simplicity of automation of the balancing process in n parameters.

 The claimed method is easily implemented, because voltage transformers, current comparator, selective null indicator, measure of capacitance used to measure n-element two-terminal devices from it are typical elements and nodes of known (see Novik A.I. Systems of automatic balancing of digital extreme AC bridges. - Kiev : Naukova Dumka, 1983) multi-arm transformer bridges for automatic measurement of two-terminal parameters using a two-element circuit, and the implementation of the necessary computational operations using the computer described The measurement procedure is not difficult.

 The claimed method can be used as a basis for measuring the parameters of n-element two-terminal networks, which are exact equivalent circuits for many important objects in various fields of science and the national economy, and will allow the construction of high-precision digital bridges with new functionalities that significantly expand the range of research and control tasks on a variable current.

Claims (1)

 A method for separately measuring the parameters of n-element two-terminal circuits with a multi-arm transformer bridge, comprising balancing the common-mode power supply of the comparison arms and measuring, by adjusting the number of turns of two additional arms, the ratio of this bridge with a convergence angle of 90 ° by n / 2 if the number n of measured the parameters are even, and at (n + 1) / 2 frequencies, if n is odd, followed by a series of repeated equilibrations by adjusting the number of turns of the marked two additional shoulders of the ratio until they are zero values, characterized in that before each series of repeated equilibrations, the supply voltage of the comparison arm is formed, changing with frequency similar to the quotient of the complex conductivity of the measurement arm by the complex conductivity of the comparison arm, by setting the number of turns n of the adjustable main arms of the ratio, which is calculated by the active and its reactive components relative to the supply voltage of the measuring arm and according to the counts of the number of turns of the two adjustable additional arms relative to solutions in the previous series of repeated equilibrations, and a separate reading of the measured parameters is carried out according to the number of turns of the indicated n adjustable main arms of the bridge ratio.