SU1552139A1 - Apparatus for measuring coupling impedance of cylindrical screens - Google Patents

Abstract

The invention relates to communication technology. The purpose of the invention is to expand the dynamic and frequency ranges and reduce measurement errors. The device contains external 1 and internal 2 conductors, test screen 3, end plugs 4 and 5, induction converter 6, shielded conductor 7, ring cores 8, generator 9, indicator 10 and screen 11. Introduction of an inductive converter consisting of a shielded conductor and ring cores, allows to increase the measurement accuracy of the resistance of cylindrical screens and expand the dynamic and frequency ranges for screens with a large screen attenuation value. 1 il.

Description

The invention relates to a communication technique, in particular to a technique for measuring the resistance of a connection of cylindrical screens and, in particular, cable shields.

The purpose of the invention is to expand the dynamic and frequency ranges and reduce measurement errors,

The drawing shows a proposed device for measuring the resistance of the connection of cylindrical screens.

The device contains external 1 and internal 2 conductors, test screen 3, end plugs 4 and 5, induction converter 6 consisting of one turn of shielded conductor 7 and ring cores 8, generator 9, indicator 10 and screen 11.

The generator 9 is connected between the inner conductor 2 and the test screen 3. On the generator 9 side, the outer conductor 1 is connected to the tested screen 3 by means of an end cap 40 On the opposite side of the installation, the outer conductor 1, the test screen 3 and the inner conductor 2 are interconnected with using end cap 5. Inside the outer conductor 1 is placed induction transducer 6, which consists of one turn of the shielded conductor 7 and the ring cores 8 of ferromagnetic material. The ring cores 8 are worn evenly along the test screen 3 and the shielded conductor 7, the inner core of the shielding conductor 7 on the generator side 9 is connected to the outer conductor 1, at the opposite end it is displayed through the outer conductor 1 Pa 10 is connected to the external conductor 1. The screen of the shielded conductor 7 on the side of the generator 9 is isolated from the external conductor 1, and at the opposite end is connected to it.

The device works as follows.

A generator 9 is connected to the input of a coaxial circuit called internal conductor 2 and test screen 3. At the opposite end, this coaxial short-circuit circuit with an end cap 5. The generator 9 creates a current in this circuit.

In turn, this current creates on the outer surface of the test screen 3 EMF equal to

E I ZC8-1,

where E - EMF on the outer surface

test screen 3, V; I is the current in the circuit: the inner conductor is the test screen, and ZCB is the resistance of the test screen 3, Ohm / m; 1 - - the length of the test screen

3m.

This EMF in turn creates a voltage in the induction converter 6, consisting of one turn of shielded conductor 7 and ring cores 8, which is measured by the indicator 10. At a given level of the generator 9 and a certain transfer function of the induction converter 6 according to the measurement result value of the resistance of the test screen 3.

Based on the results of measurements, estimates of the modulus of communication resistance, theoretical estimates of a given value, as well as absolute and relative values of their differences with theoretical estimates are obtained. The latter are obtained by calculating the formula

 St.

R-,

P

l shft

where y- 2 Iff

R0 - screen resistance at

direct current, Ohm / m; p is the absolute magnetic permeability of the screen material, GN / m;

& - specific conductivity of screen material, CM / m; f - frequency, Hz,

The following methodology was used to assess the immunity. It is known that the conductivity of the connection of continuous screens is zero. Accordingly, when testing short samples of continuous cylindrical shields (1 "L, where 1 is the sample length, and A is the wavelength), the PXX level measured in the considered devices when the generator circuit is at idle is due to parasitic energy transitions {disturbance) Pk level (measured in the considered devices during the operation of the generator circuit in the short-circuit mode, arr51552

caught by the sum of the desired signal level and interference. Level difference

Jq

P "1 - P.

XX4

)

serves as an assessment of the noise immunity of the measuring circuit of the device, where Pkj, Pyx are the levels measured when the generator circuit operates in the short circuit and idling modes, respectively; RK - amendment, defined by the ratio

Where

to

V

-20 lg / v0l / Z6 /,

"in 1

A3 Vr

generator output level;

generator impedance;

the length of the outer conductor of the device;

noise immunity of the measuring circuit;

the values of the modulus of resistance of the test screen, obtained by experimental and calculated routes A, 201gZ3; lg zt. The noise immunity of the measuring circuit of the proposed device is significantly higher. This allows the measured frequency range to be expanded, in this example, to a frequency of 1 MHz - the limit determined by the sensitivity of the measuring device, which is equal to (-140 dB).

The advantage of the proposed device in comparison with the known one is manifested to a greater extent when testing more efficient screens and to a lesser extent when testing screens with a low attenuation of shielding.

The technical and economic efficiency of the proposed device in comparison with the known one is as follows. The elimination of the galvanic connection between the generator 9 and the indicator 10 due to the introduction of the induction converter 6 made it possible to completely shield the indicator circuit by using end plugs 4 and 5, and consequently, significantly reduce indicator spurious signal. In addition, due to the use of an induction converter 6 with annular cores distributed along the length of 8 DS, induced on the entire length of the test screen 3

396

Consequently, indicator 10 will fix the maximum value of the voltage. These circumstances lead to a significant increase in the sensitivity of the device and, consequently, to an expansion of the dynamic and frequency ranges and a decrease in the measurement error of the resistance-Q values.

Thus, compared with what is known in the proposed device, the accuracy of the measurement of the resistance of the communication of the cyclic 5 screens increases, and the dynamic and frequency ranges for the screens with a large screen attenuation value are expanded.

Claims (1)

Claim 0 A device for measuring the communication resistance of cylindrical screens, comprising an outer conductor made in the form of a metal tube, the test object with its inner conductor inside it, coaxially with the outer conductor and the test object, between the inner conductor at one end and the object under test is a 0-key generator, at the opposite end the inner conductor is connected to the object under test, so that, in order to expand the dynamic and An inductive transducer consisting of one turn of shielded conductor and ring cores of ferromagnetic material is inserted into the device in order to reduce the measurement error and the ring cores are placed evenly along the entire length of the test object and the shielded conductor, and the connection of the external conductor to the 5 test object made in the form of end caps, the outer conductor at both ends is shorted to the test object through the end caps, the inner core of the screen is 0 This conductor from the generator side is connected to the external conductor, at the opposite end it is led through the external conductor to the indicator, the second output of which is connected to the external conductor, the screen of the shielded conductor from the generator side is isolated from the external conductor, and at the opposite end it is connected to it. five five