SU1580570A1 - Device for measuring cable length - Google Patents

Abstract

The invention relates to electrical engineering. The purpose of the invention is to increase the reliability of the measurement. The device contains an induction sensor 1, selective amplifiers 2.3, frequency multipliers 4.5, analog-digital converter 6, indicator 7, sine wave generator 8, phase detector 9, amplifier 10. A test signal is supplied to the beginning of the cable line from the output of amplifier 10 The sum of two sinusoidal signals. At some distance from the beginning of the cable, the signal is shifted in phase. The magnetic field is sensed by the induction sensor 1 and the phase of the signals is compared in the phase detector. 2 Il.

Description

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The invention relates to telecommunications technology and can be used in measuring cable lengths on high frequency transmitting amplification systems.

The purpose of the invention is to increase the reliability of the measurement.

Figure 1 shows the structural electrical circuit of the proposed fg device; 2 shows the frequency dependence of the phase coefficient B of cables.

A device for measuring the length of the cable (Fig. 1) contains 15 inductive sensor 1, first 2 and second 3 selective amplifiers, first 4 and second 5 frequency multipliers, analog to digital converter 6, indicator 7, generator 8 of a sinusoidal 20 signal, phase detector 9 , amplifier 10,

The device works as follows.

At the beginning of the cable line, from the output 25 of the amplifier 10, a test signal is supplied, consisting of the sum of two blue-coupled signals with frequencies f from the generator output 8 and from the output of the first multiplier 4. The frequencies 30 f 4 and f2 must be selected in a certain way.

If we consider the graph of the frequency dependence (Fig.2) of the phase 5 coefficient of communication cables of any type, then -, g it can be noted that in the frequency range from 0 to some f, the dependence of B on frequency is nonlinear, in the frequency range above f the plot of ft (f) is a nearly straight line. For example, for cables MKS 1 k4x1,2, ZhS, 2, ZhS 7x4x1,2, IKSA, 2, TG of the CCI and others above f S 10 kHz graphs K (f) are almost straight line, below this frequency there is a rather pronounced non-linear dependence, especially in the frequency range up to 300 Hz.

Therefore, the frequency f4 is chosen in the range of 0 - 300 Hz, the frequency - in the range of frequencies close to f ,, n 1 - is an integer. The frequency f corresponds to the phase factor & frequency f 2. flitr

At some distance 1 from the beginning of the cable, the signal with frequency f is shifted in phase from the beginning of cable by value B (1, the signal with frequency f by size / 321. To isolate this shift, it is necessary to multiply in frequency by the second multiplier 5 a signal with a frequency f ,, while receiving a signal with a phase shift relative to the beginning of the cable J3, In, it is now possible to compare the phase of this signal and the phase of the signal with a frequency f

DSRV, 1n-pr1 (p (n-r7) 1,

those. Der is directly proportional to the electrical cable length. The value (ft, n- | 3d) is not zero, since the frequencies f and f are chosen taking into account the non-linearity of the frequency of the characteristic A F (f).

The magnetic field surrounding the cable, to which the signal from generator 8 is fed, is sensed by induction sensor 1, signals with frequencies f $ and f are allocated by the first 2 and second 3 selective amplifiers, respectively, in the second multiplier 5 the frequency is multiplied by frequency signal with frequency f, in phase detector 9 - comparison of signal phases. The signal proportional to the length of the measured cable from the output of the phase detector 9 is fed to the input of the analog-digital converter 6. After processing the signal by the analog-digital converter 6 on the indicator 7, information is received on the electrical length of the segment of the measured cable from in which there is an operator with induction sensor 1.

When measuring cable length, the operator must move along the cable path. Due to the fact that the phase constants of the circuits of different types of cables differ from one another, it is necessary to carry out the initial calibration of the instrument before measurements.

Claims (1)

Invention Formula A device for measuring the length of a cable, comprising a sinusoidal signal generator, a first selective amplifier and an indicator, characterized in that, in order to increase the reliability of the measurement, the first connected frequency multiplier, the input of which is connected to the first gene output, is introduced 1 a sine-wave signal generator, and an amplifier, the second code of which is connected to the second generator output, a dual signal, and the amplifier output is the input of the cable to be measured, the induction sensor connected in series and the second selective amplifier, the second multiplier connected in series are often / l 5805706 you whose input is connected to the exit - first selective amplifier, phase detector, the second input of which -connected to the output of the second selective amplifier, and analog-to-digital converter, the output of which is connected to the indicator input, the output of the inductive sensor is connected to input JQ House of the first selective amplifier. 2 1, Hz