SU1756832A1 - Method of measuring complex parameters of bipolar members - Google Patents

Abstract

The invention relates to electrical measurements and can be used to determine the complex parameters of a two-port network without measuring phase angles. The purpose of the invention is to improve the measurement accuracy. To do this, applying a harmonic voltage to the input of the auxiliary T-link, formed from two identical known resistors in the longitudinal branches x and the measured two-pole in the transverse branch, measures the voltage and current at its input terminals and the voltage at the output in idle modes course and short circuit and calculate the parameters of the two-terminal. The method also makes it possible to simplify mathematical processing and reduce hardware costs in its implementation. 3 il. next s y-lt

Description

The invention relates to electrical measurements and can be used to determine the complex parameters of a bipolar network without measuring phase angles.

Bipolar can be any electrical device for energy or informational purposes, which have only two points of connection to the electrical circuit (two poles). Below are considered linear and passive two-terminal networks with an arbitrary, arbitrarily complex internal structure. Such two-poles are assumed to be connected to external sources of harmonic voltage or current. The print is characterized by the total (complex) input resistance Z or the full (complex) input conductivity Y, where

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CO N3

g-rHJx-Ze j fD 2 «mod (2) (2)« ZcoS4 j

if.qr.arctg-j (z) -Z6imp Y "|" G-jb-ye i4

W (jj

pkkDCH lLv1, G, .Re (Yhyco3q;

la im

q-a M orelij-ijr-, B "Im (,

where p is the phase angle between voltage and current in a two-port network,

Thus, the total input resistances or conductivities of a two-port network are characterized by complex quantities, which are given by either real (r, G) and imaginary (x, C) components, or modules (Z, y) and arguments

(± 0 Methods are known for determining the complex input resistances or conductors of a two-terminal network using a group of the following devices: a wattmeter or a phase meter, a voltmeter, and an ammeter.

The disadvantages of this method are as follows: when using a wattmeter, the sign of the phase angle p% .0 is unknown, i.e., the nature of the two-pole device itself — inductive or capacitive — is not determined; overcoming this drawback requires additional experiments and measurements.

When using a phase meter, the sign of the phase angle becomes known, but its accuracy is low, which leads to significant errors in determining the components of impedances or conductances; if it is necessary to measure Z or Y at frequencies exceeding 50 Hz, significant difficulties arise because wattmeters and phase meters for frequencies of the sound and radio range are extremely scarce, very expensive, and their accuracy is also low; The errors in instrumental determination of phase angles are not only very significant, but also significantly depend on the frequency of the voltage at which measurements are made.

The closest to the claimed method is the measurement of the parameters of a complex two-pole network, which means that the measured two-pole network is connected to the output of a calibrated four-pole network, the complex parameters of which are set over the entire frequency range used. Then, the effective values of the voltages and currents at the output of the loaded calibrated two-port network are measured and the module Z and the argument of the two-terminal model being investigated are calculated by the algorithm.

The known method has the following disadvantages.

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The calibrated quadrupole must be given two complex parameters:

characteristic impedance

Zc (5)

where Zc mod (Zc); pc arg (Zc);

fixed transmission

r a + Jb, (6)

where a and b are constant damping and phase, respectively.

All these parameters are frequency dependent. Consequently, for measuring different frequencies, four frequency characteristics of a calibrated quadrupole should be specified.

Zc Z (to), rg. Рсо (), а а (ш), b b (w). In their practical use, additional errors are possible that affect the final results.

The formulas for determining p - arg (Z) are rather complicated and cumbersome, which complicates their use in the measuring process.

The purpose of the invention is to improve the accuracy of determining the measured parameters.

This goal is achieved by the fact that according to the method of measuring the complex parameters of a two-terminal network, including supplying a harmonic voltage to the input of a quadrupole, measuring the effective values of voltage and current at its terminals, calculating the complex parameters of the two-terminal network, form an auxiliary four-terminal network in the form of a symmetric T-link of two known resistors in the longitudinal branches x and the measured two-port in its transverse branch. Apply a harmonic voltage to the input of the T-link, in idle mode (XX), the voltage and current at its input terminals and the voltage at the output are measured; in the short circuit (short circuit) mode, the voltage and current at the input terminals are measured.

The determination of the complex parameters of the measured two-terminal device is carried out using 5 formulas (3) and (4), and

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M-

N.

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h-r-,

m4 to And 1 41MM ICHM)

Where

and wow. u) ttх

k ° t. t; t

"Ahi x

(7}

(I

(9)

(W

In expressions (7) - (10) - lhx, UIK, Their, Hk are the effective values of the voltage and current at the input of the T-link in the XX and short-circuit modes, respectively; U2x is the voltage at the output of the T-link in the XX mode; R is the resistance of each of the two resistors forming the longitudinal branches of the T-link. The value of R. in ohms, is known. The relative error of resistance of each of these resistors should not exceed the guaranteed. errors of measuring devices.

Fig. 1 shows a diagram of a T-link of the type R-Y-R, forming a generalized quadrupole SJ in Fig. 2 — a quadrupole E at idle and the quantities measured therewith; in FIG. 3, a quadrupole 2 is in short-circuit mode and the values measured therewith.

The proposed method of measuring the complex parameters of a two-terminal network is reduced to performing the following sequence of operations with the help of material objects (voltmeter, ammeter, key) on another material object (the two-terminal device under study).

Form a generalized two-port network 2J. consisting of a symmetric T-link of the form R-Y-R, where R is two identical resistors whose resistance is known, Y is the measured complex bipolar (Fig. 1).

A source of harmonic is connected to the input of the generalized four-port of the motif X

voltage, and the output - the key K, with which you can translate the T-link in idle mode (XX) or short circuit (CZ).

Measured in mode XX effective values of the voltage and current at the input of the generalized quadrupole Zj Uix, hx and the voltage at its output U2x (Fig.2), measured in the short-circuit mode, the effective values of voltage and current at the input of the generalized four-terminal UIK, IR (fig.Z).

Calculated according to formulas (10) of two auxiliary parameters

v - Uix T2 - UIK hx U2x Uix IIK

In their physical sense, these are the parameters-modules of complex functions of a complex argument, i.e.

K - modfchr}; T mod (thr), (11)

where Г а + jb is the transfer constant of the generalized quadrupole 2 according to - expression (b);

a, b - constant damping and phase, respectively.

Calculate according to the formulas (8} - (9) of the two calculated parameters M and N, which in their physical sense are as follows:

M cha N sha sinb, (12)

The real and imaginary components of the complex (total) conductivity of the measured two-port G and -B are calculated according to formulas (7).

In this case, the calculated values of G and B are invariant to the parameter R, i.e. as R changes in (7), not only the denominators change, but the numerators (M-1) or (-N). Physically, this is determined by the fact that, with variations of R, the voltages and currents measured in the XX and the short-circuit modes change accordingly. All intermediate and design parameters change accordingly, but G and B remain constant, determined only by the internal structure of the two-port network Y, which does not depend on R.

The total conductivity of the two-terminal Y is calculated according to formulas (3) - (4) and, if required, its total resistance Z,

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(1b)

x / s

gTsGHh sg-Gt)

x "B

T

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The technical and economic efficiency of the proposed method as compared with the known one is that the measurement accuracy is improved, a cheaper element base is used (two identical resistors instead of a calibrated two-port network); the computation of the complex parameters of the measured two-port network is greatly simplified and accelerated, which is important when automating the measurement process and processing the results on a computer; when measuring at a frequency different from the industrial one, there is no need for a frequency meter, without which it is impossible to refer to the frequency characteristics of a calibrated two-port network.

Claims (1)

Claims The method of measuring complex parameters of a two-port device includes harmonic supply to a quadrupole input, measuring effective values of voltage and current at its terminals, calculating complex parameters of a two-terminal device, characterized in that, in order to increase accuracy, an auxiliary four-terminal network is formed in the form of a symmetrical T-link — of two known identical resistors in the longitudinal branches x — and a measured two-port in its transverse branch, the actual values of voltage and current at the input terminals of the T-link and the voltage at its output terminals are measured in idle mode, in the short-circuit mode, the effective values of voltage and current at the output terminals of the T-link are measured, and the definition of the complex parameters of a two-pole device is made by the formulas  one . Y g - Z m M ICHZ H (| -t) -G) K.iii to IV -1 Uix 1 (for TG T IX I (TO where Uix, UIK are the effective voltage values at the input terminals of the T-link in idle mode and short circuit, respectively: U2x - the same at the end of the T-link in idle mode; Their, Hk are the effective values of the currents at the input of the T-e ve and in the idling and short-circuit modes, respectively; K, T, M, N - intermediate calculated values; R is the resistance of each of the resistors forming two longitudinal arms of the T-links; Y is the total conductivity of the measured two-pole; G, B - active and reactive components Y; Z is the total resistance of the measured two-pole device; y, # -module and argument 2. sh Csg.1 It   - - -J 123 TO