SU1580288A1 - Method of determining impedance of two-terminal network - Google Patents

Abstract

The invention relates to a measurement technique and can be used to determine the frequency dependence of the impedance modulus of a broadband two-port network (DP). The purpose of the invention is to improve the accuracy of measuring impedances in a wide frequency and dynamic ranges. The voltages of the constant voltage source 1 and the generator 2 of the test voltage are switched by switches 5, 6 with the frequency of the generator 16 in the two-pole 17 under study, connected to terminals 7, 8. The resistors 3, 4 of the resistances and conductances serve to measure the resistance of the two-pole permanently current and impedance. For this, the indicator 15 compares the signals from the shunt 9 multiplied by the multiplier 10 when a constant and alternating voltage is applied to a two-port 17. 1 Il.

Description

5 K, (iiy,) s, Iff- ;; ;) 91p (03 l +

the result is a constant output voltage

(P)

UA + 57ТхТТ KtKzKsSfS2 (1tAl,) | f2S „Ц

8 2 (i ± z.) S, g o, DJ (y} Ma e.n (Q | t + (,,

.diirz) Ґ-D w} (.2)

where K2 is the gain factor taking into account the values of u and and "of

switching frequency; 30 razheny (7) and (8) we obtain the constant Къ - rectifying coefficient voltage:

synchronous detector.

The dc current i

penitent through the studied bipolar-and KK8 (1-1- / G) ------

Nick, until the voltage disappears-35 g. 3 g at 2 f

commutation tots. With increasing - ir v v ъ with:.,

- k., - 3а, and г «„ with ij-f / l n-t-5 i

MODULE OF COMPLETE COMPILATION WITH ROS-K l-rtH,} {li-Zi)

volume of frequency (2.0) indicated measurements x (14G) () 1) (13) some currents carry out an additional increase in resistance two-by-40 for parallel switching of a melon chandelier, for example, by means of a resistance box switched on by -v -vv / cho. 3 6 lupeoiod switching sequentially And g $ g -№

looping switching successively 8

with two-pole, in the case of reduced

No modulus of resistance with 45 K, -ТЦ Х frequency (2Г, 0) - conduct- shop,) ()

bridges connected to the half period (

switching parallel to the studied - fli -ig 1U;

bipolar network. Sequential or

parallel connection of stores 50 The disappearance of the voltage of the dc frequency is carried out in that switching, and hence in the half-switching period, when through a given output voltage (U, the two-terminal circuit flows 0) For its impedance, its relative frequency variation is determined by the relation

In these cases, the voltage U.

from expression (3) takes the form: - l / g ". / ic%

- 1 P I TI 4L J ü V. I-5J

to sequentially turn on K

5 K, (iiy,) s, Iff- ;; ;) 91p (03 l +

and in the case of a decrease

. - 2, about. About)

Taking into account (13) and (14), the impedance modules of the two-pole device at the CO frequency are

z | - R (l + Z,) R (l +,) -

 R + r;; (17)

 - RO —H.) - Rd -) - R (1 — RG,). (8)

Increase the frequency of the alternating voltage to a value, and repeat the indicated operations. The relative frequency changes can be determined by analogy with (13) and (14) from the relations

 “4 G, 2 0; (nineteen)

 I - R1 "

(20)

where r i and G., resistance and conductivity of stores when uranovanshenivanii schemes at a frequency of 0) g - Impedance of the investigated

dvuhpolemnika on frequency (02:

 R (l + Z,) R + ri (21)

zЈ R (l -2,) - R (l - RGt). (22)

According to the results of measurements 2Г ,, 2Г,. 2ELn, it is possible to construct the frequency response of the bipolar circuit under investigation for any change in the magnitude of the impedance versus frequency.

Thus, the values of the modulus of the impedance in a given frequency pfcana-zone COMMIN G3,, 03g are determined from the values of the resistivity or direct current conductivities. In addition, as follows from formulas (17) (18) or (21), (22), the measurement results do not include frequency variations of the gain factor (C1,) of the broadband amplifier, frequency variations of the slope ( sensitivity1)

five

0

five

0

five

0

five

0 5

detector ($ 4) a also frequency variations of the slope (sensitivity) of the multiplying transform (Sy).

The device implementing the method contains a source of constant voltage 1, a tunable frequency test generator 2, a resistance store 3, a conduction store 4, switches 5 and 6, input terminals 7 and 8, shunt 9, a multiplication unit 10, a wideband amplifier 11 , amplitude detector 12, amplifier 13 switching frequency, synchronous detector 14, indicator 15 and generator 16 switching frequency.

The two-port circuit 17 under study is connected to terminals 7 and 8, one of which is connected to the output of switch 5, and the other to low-resistance shunt 9 and one of the outputs of the multiplying circuit 10. One of the inputs of the multiplication unit 10 is connected to the output of automatic switch 6, the inputs which are connected to the sources of constant 1 and alternating 2 voltages. Resistance box 3 is connected between source 1 and one of the inputs of automatic switch 5, the second input of which is connected directly to generator 2 output. Conductivity store 4 is connected between source 1 and potential shunt terminal 9. A serially connected broadband amplifier 11 is connected to the output of multiplication unit 10, a detector 12, a selective amplifier 13, a synchronous detector 14 and an indicator 15. The control inputs of the automatic switches 5 and 6 and the synchronous detector 14 are connected to anti-phase outputs generator 16,

The device works as follows.

Constant source voltage

1 and alternator voltage

2 through the automatic switch 5 alternately affect the studied two-port .17. The voltage drop across the shunt 9 from the constant and alternating currents of the two-terminal circuit 17 affects one input of the multiplication unit 10, the other input of which is acted upon by the alternating or direct voltage depending on the position of the switch 6.

With the positions of the switches 5 and 6 of the multiplication indicated in the drawing

The direct current flowing through the two-port device 17 under study from source 1 and the alternating voltage of the generator 2, and in the opposite position of the switches 5 and 6, the alternating current of the two-terminal device 17 from generator 2 and the constant voltage source 1.

During continuous operation of switches 5 and 6, which are controlled by antiphase pulses of generator 16, alternating voltage bursts from the output of multiplication unit 10 are alternately amplified by wideband amplifier 11 and detected by amplitude detector 12. Switching frequency voltage is amplified by selective amplifier 13 tuned to oscillator frequency 16, and rectified by synchronous detector 14, which is controlled by antiphase pulses of oscillator 16. Rectified voltage is detected by output indicator 15.

The resistance of store 3 or the capacity of store 4 is changed to obtain a zero indicator reading 15. The impedances of the two-port circuit under study 17 are determined by the formulas (19) - (22) taking into account the readings of stores 3 and 4 when the frequency of the generator 2 changes in a given frequency range.

Claims (1)

Invention Formula the measured two-pole when applying calibration voltages compare the values of the first and second signals and change the value of one of the calibration voltages to establish equality of signals proportional to the currents through the measured two-pole, so that the accuracy and quality of the first of the calibrated voltages, use a constant voltage, use the alternating voltage as the second, the value of the first signal is obtained as the product of the value of the constant voltage to alternating voltage, whose amplitude is proportional to the current through the measured two-terminal, magnitude. The second signal is obtained as the product of the value of the second calibrated voltage for a constant voltage, the value of which is proportional to the current through the measured two-pole when the constant calibrated voltage is applied in series with the tested two-pole device, the calibrated resistance is measured, the measured current is measured through the measured two poles, and the voltage change on the test two-pole is made by changing the value of the calibrated resistance, according to the values of the constant voltage and after the current through the test dvukhpolosniki determine its resistance at a direct current, and the magnitude of the impedance of the test dvuhpolevniki The method for determining the impedance of a two-pole device is in that, the first and second co-currents are supplied to the input of the measured two-pole by the size of the calibrated bluesman at the moment of equality, the signals are proportional to the currents through signals proportional to the current of the four-measured two-port network. about 0 five five the measured two-pole when applying calibration voltages compare the values of the first and second signals and change the value of one of the calibration voltages to establish equality of signals proportional to the currents through the measured two-pole, so that the accuracy and quality of the first of the calibrated voltages, use a constant voltage, as the second use a variable voltage, the magnitude of the first signal is obtained as the product of the magnitude of the applied constant voltage to alternating voltage, the amplitude of which is proportional to the current through the measured two-terminal, magnitude. The second signal is obtained as the product of the second calibrated voltage and direct voltage, the value of which is proportional to the current through the measured two-port, when applying a constant calibrated voltage in series with the test two-pole, include a calibrated resistance, measure the direct current through the measured two-pole and the voltage change on the test bipolar is made by changing the magnitude of the calibrated resistance, according to the values of the constant voltage and direct current through the tested dvukhpolosniki determine its resistance to direct current, and the magnitude of the impedance of the test dvuhpolemniki