SU907473A1 - Device for determination of distance to cable damage - Google Patents

Description

The invention relates to a radio metering technique and can be used to quickly and accurately determine places of damage to cable, long-distance communication lines.

Closest to the invention in technical essence is a device for determining distances to cable damage locations, comprising a button, a start pulse generator, a short probing video pulse generator, a unipolar pulse generator, a pulse counter, an RS trigger, a time interval meter, a time delay unit, a shaper 1 restart pulse, additional time delay unit through which the test cable is connected [1]. . . .

The main disadvantage of the known device is the ability to study cables of only a small length. This is due to the low energy of the short probe pulses, their fast attenuation in the line, and the low noise immunity of the pulse counter.

The purpose of the invention is to improve the accuracy of measurement.

This goal is achieved by the fact that in the device for determining the distances to the places of cable damage, containing a power button connected via a start pulse generator block to the first input of the probe pulse shaper block, a unipolar pulse shaper block, a pulse counter, the corresponding outputs of which are connected to the block inputs a restart pulse shaper, the output of which is connected to the second input of the probe pulse shaper block, the first time delay block, the input of which connected to the output of the start-pulse generator block and to the R-input of the pulse counter, the output of the first time delay block is connected to the S-input of the RS-trigger block and to the R-input of the time interval meter block, the corresponding output of the pulse counter is connected to the R-input RS trigger block, the output of which is connected to the 3-input of the time interval meter block, the second time delay block, the output of which is connected to the terminals for connecting the monitoring object, the blocks of the phase modulator, matched filter and comparator are introduced, m the input of the phase modulator block is connected to the output of the probe pulse shaper block, the outputs of the phase modulator block are connected to the corresponding inputs of the matched filter block, the output of which is connected to the input of the unipolar pulse shaper block, the output of which is connected to the comparator block, the output of which is connected to the S-input of the counter pulses.

The drawing shows a structural electrical diagram of the device.

The circuit contains a power button 1, a start pulse generator block 2, a probe pulse shaper block 3, a reference pulse shaper block 4, a 5 pulse counter, an RS trigger block 6, a time interval meter unit 7, a first time delay block 8, ί block 9 of the shaper of the restart impulses, the second time delay unit 10, terminals 11 for connecting the monitoring object, phase modulator unit 12, matched filter unit 13 for connecting, comparator unit 14.

The device operates as follows.

When button 1 is pressed, block 2 generates a single start pulse, under which the counter 5 pulses is set to zero, block 6 of the RS-trigger is in a single state, block 7 of the time interval meter is initialized (zero), and block 3 of the shaper generates a probe a radio pulse with a duration of Г ^ ег п д 'д д, where m is the half-number. Riodes (discrete) the duration of the half-periods of the probing signal.

A sounding harmonic radio pulse with a duration from the output of block 3 of the shaper is fed to the input of block 12 of the phase modulator, in which the sounding 5th signal is phase-modulated in accordance with the Barker code and an exponential video pulse is generated with a duration of Ά 7, *, where _gn1C1 is The maximum possible delay probing 'th pulse ^and in the test cable.

An exponential video pulse from the first output of the phase modulator block 12 is supplied to the first input of the matched filter block 13. Under the action of this pulse, the transmission coefficient of the matched filter unit 13 changes inversely with the attenuation law of the probe signal in the cable communication line .. 60

A sounding phase-modulated radio pulse from the second output of the phase modulator block 12 is fed through the replenishment block 10 of the time delay to the input of the studied 65 cable communication line and directly to the second input of the matched filter block 13. In block 13 of the matched filter, the verification (compression) of the phase-manipulated probe signal is carried out and a short pulse is generated, duration! which is equal to TD, as well as short 0 pulses of duration 'SD with an amplitude of w times less than the main one, the so-called'residues' ¹ that do not contain useful information. The compressed signal from the output of block 13 of the matched filter is fed to the input of block 4 of the unipolar pulse shaper, the output of which produces video pulses, which are the envelope of the compressed signal. Video pulses from the output of block 4 are fed to the input of the comparator block 14, which generates a short counting pulse only when the main pulse of the signal is exposed from the compressed signal. To this end, the response threshold of block 14 is set above the possible level of residuals and interference signals. The counting pulse 25 from the output of block 14 is input

S of the counter 5 pulses and sets its trigger low order in a single state, i.e. at the inverse output of this trigger, a low voltage level is set. Block 9 generates a restart pulse only when at the same time at its both inputs single (high) voltage levels 35 act. The first restart pulse is generated after setting the pulse counter 5 to zero. However, under the action of the first restart pulse, block 3 does not generate a second probe pulse, since the start pulse still continues to operate at its first input. This property is possessed by many well-known relaxation formers.

The phase-shifted signal reflected from the cable damage point appears at the second input of the matched filter block 13 after the probing signal is output after a time determined by the delay of the probing and reflected signals in the test cable and in the time delay block 10.

Under the action of the reflected signal, the block 13, the matched filter, the block 4 of the shaper of unipolar pulses and block 14 generate a second counting pulse, which is fed to the counter 5 pulses and changes its state. At the inverse output of the least significant bit of counter 5, a unit voltage level occurs, i.e. fulfill ^ the condition for the operation of block 9 of the pulse shaper restart. Block 3 generates a second harmonic sounding radio pulse, which is fed to block 12 of the phase modulator. Under the influence of this pulse, a second exponential pulse is generated at the first output of block 12, and a probing phase-coded signal is generated at the second output, which, through the time delay block 10, enters the cable under investigation and directly to the second input of the matched filter block 13.

As a result of processing the second probe signal using block 13 of the matched filter, block and block 14, a third counting pulse appears at the input of the counter 5, which measures the state of the counter

5. In this case, the low-order trigger of counter 5 is set to a single state (low voltage level at the inverse output). The re-start pulse shaper unit is reset.

Upon receipt of the second and subsequent reflected signals, the processes are repeated until a single voltage level is established at the output of the 5 pulse counter (at the direct output of the senior discharge), and a low voltage level is established at the inverse output of the senior discharge, at which the operating conditions of unit 9 are violated re-start pulse shaper.

I

When establishing a unit voltage level at the output of the 5-pulse counter (at the direct output of the highest level), the PS trigger block b is set to zero. Block 7 measuring the time intervals fixes the number N-, where T _p is the measured time interval (the duration of the positive process at the output of block 6 of the RS-trigger), which is determined by the conversion factor of the counter 5 pulses, i.e. the number of t. of soundings of the test cable for one measurement and the delays of the probing and reflected signals in blocks 8 and 10 of the time delay;

T ₃ - the period following the counting pulses in block 7 of the meter time intervals.

Providing, for example, the corresponding conversion factor of the pulse counter or the period of the counted pulses T _e in block 7 and presenting the number N of counted pulses in decimal form, the measurement results can be recorded in decimal form (km).

The obtained measurement result Ν, in the general case, is n times larger than the real one. This must be taken into account when implementing a reading device. *

The introduction of a phase modulator, a matched filter and a comparator into the device ensures its operability with a harmonic sounding radio pulse with high power. An increase in the power of the probe signal is achieved by increasing its duration. In order to maintain high accuracy and resolution, the probe signal is phase-modulated, for example, according to the Barker code or, more generally, according to the M-code law, followed by compression (optimal processing) in a matched filter up to 7 _{as well} as probing and reflected signals . The introduction of the comparator device provides increased noise immunity, i.e. the device is prevented from interfering with reflected signals and from residual pulses after compression. The analysis shows that in the proposed device the power of the probe signal is approximately an order of magnitude higher compared to the known one (m times).

Calculations suggest that the proposed device allows to increase the range of stable sensing of the studied cables by>

where is the length of the studied cables when probing with short video pulses;

- the length of the investigated: cables when sensing phase-coded signal;

β is the attenuation coefficient of the signal in the cable;

^m is the number of discrete phase-coded signals.

Thus, the device exceeds the well-known cable sensing range by about an order of magnitude. At the same time, accuracy and resolution are kept high.

Claims (1)

filter and comparator, the input of the phase modulator unit is connected to the output of the sounding probe module, the outputs of the phase modulator block are connected to the corresponding inputs of the unit, the matching filter, the output of which is connected: the input of the unipolar pulse generator unit, the output of which is connected with a comparator unit, the output of which is connected to the S-input of the pulse counter. The drawing shows a structural electrical circuit of the device. The scheme contains a button 1, - switching on, block 2 of the start-pulse generator, block 3 of the probe pulse generator, block 4 of the reference pulse generator, pulse counter 5, block 6 of the K3-flip-flop,: block 7 of the time interval meter, first block 8 of the time delay , i block 9 of the re-start pulse generator, second time delay block 10, terminals 11 for connecting the control object, phase modulator block 12, matched filter block 13 for connecting, comparator block 14. The device works as follows. When button 1 is pressed, unit 2 generates a single start-pulse, under the action of which the pulse counter 5 is set to the zero state, unit 6 of the RS flip-flop into one, unit 7 of the time interval meter into the initial (zero) state, and block 3 of the driver produces a probe radio pulse with a duration of mtd, where ha is the number of half-waves (discrete), the duration of the half-periods of the probe signal. A probing harmonic radio pulse with a duration from the output of block 3 of the imager is fed to the input of block 12 of the phase modulator, in which the probe signal is modulated in phase in accordance with the Barker code and an exponential video pulse with a duration T ,,, t J "d where tj is the maximum possible delay of the probe pulse in the cable under study. An exponential video pulse from the first output of the phase modulator unit 12 is fed to the first input of the matched filter unit 13. Under the action of this pulse, the transmission coefficient of the matching filter unit 13 is inversely proportional to the damping law of the probing signal on the cable line. The probing radio pulse modulated in phase from the second output of the phase modulator unit 12 is fed through the additional time delay unit 10 the cable line under investigation and directly to the second input of the block 13 of the matched filter. In block 13 of the matched filter, the phase-manipulated probing signal is verified (compressed) and a short pulse is generated, the koToporo duration is equal to TD, and also short pulses of duration t with amplitude are t times smaller than the main, so-called residues that do not contain useful information. The compressed signal from the output of block 13 of the matched filter is fed to the input of block 4 of the generator of unipolar pulses, at the output of which video pulses are produced, which are the envelope of the compressed signal. Video pulses from the output of block 4 are fed to the input of block 14 of the comparator, which produces a short counting pulse only when exposed to the main pulse of a signal from a compressed signal. For this, the threshold of block 14 is set above the possible level of residual and interfering signals. The counting pulse from the output of block 14 enters the input S of the counter 5 pulses and sets its low-order trigger to one state, i.e. the inverse output of this trigger sets a low voltage level. Block 9 generates a restart pulse only when simultaneously (high) voltage levels act on its both inputs. The first restart pulse is generated after setting the pulse counter 5 to the zero state. However, under the action of the first re-start pulse, unit 3 does not produce a second probe pulse, since the start-pulse still continues to act at its first input. Many well-known relaxation formers have this property. The phase-coded manipulated signal reflected from the cable fault location appears at the second input of the matched filter unit 13 after the sounding signal is issued through the time determined by the probe sounding and reflecting signal delays in the cable under test and in the time delay unit 10. Under the action of the reflected signal, the block 13, the matched filter, the block 4 of the unipolar pulse generator and the block 14 produce a second counting pulse, which is fed to the counter 5 of pulses and changes its state. At the inverse low-voltage output of counter 5, a single voltage level occurs, i.e. fulfill the trigger condition of the restart pulse generator unit 9. Unit 3 generates a second harmonic probe radio pulse, which is fed to a block of 12 phase modulators. Under the action of this pulse, a second exponential impulse is generated at the first output of block 12, and a second | zone-donating phase-coded manipulated signal is outputted through a time delay unit 10 to the cable under study and directly to the second input of the matched filter block 13. As a result of processing the second probing signal with the help of block 13 of the matched filter, block 4 and block 14, a third counting pulse appears at the input of counter 5, which measures the state of counter 5. In this case, the low-bit trigger of counter 5 is set to one inverse output low voltage level). The restart pulse generator unit 9 is reset. Upon receipt of the second and subsequent reflected signals, the processes are repeated until a single voltage level is established at the output of the counter of 5 pulses (at the forward output of the higher discharge), and at the inverse output of the higher discharge - a low voltage, under which the trigger conditions of the restart pulse shaper unit 9 are violated. I When establishing the unit voltage level at the output of the pulse counter 5 (at the forward output of the higher bit), the RS-6 flip-flop unit 6 is set to the zero state. Block 7 of the time interval meter fixes with NUMBER ---, where Tp is the measured time interval (the duration of the positive process at the output of the B block of the RS flip-flop), which is determined by the recalculation coefficient of the pulse counter 5, i.e. the number of tons of probings of the cable under study over one measurement and the delays of the probe and reflected signals in blocks 8 and 10 of the time delay; the period of the following counting pulses in block 7 measure the bodies of time intervals. Providing, for example, the corresponding conversion factor of the pulse counter 5 or the period of the counting pulses Te in block 7 and presented the number N of counted pulses in decimal form, the measurement results can be recorded in decimal form (km). The result of measuring N, in general, is n times larger than the real one. This must be considered when implementing a reading device. Introduction to the device of an MRD stator of the phase, a matched filter and a comparator ensures its operation with a harmonic sounding radio pulse with high power. An increase in the power of the probing signal is achieved by increasing its duration. In order to maintain high accuracy and resolution, the modulation of the probe signal by phase, for example, the Barker code or, more generally, according to the M-code law, followed by compression (optimum processing) in the matched filter, is as much as probing, and reflected signals. Introduction to the composition of the comparator device provides increased noise immunity, i.e. the device is prevented from interfering with reflected signals and from residual pulses after compression. The analysis shows that in the proposed device the power of the probing signal is about an order of magnitude higher than the known (by a factor of m). Calculations show that the proposed device allows increasing the range of stable probing of the studied cables by the length of the studied cables when probing with short video pulses; the length of the study; cables when probing with a phase-coded signal; cable attenuation ratio; discrete number of the phase-coded signal. Thus, the device exceeds the cable sensing range known by about an order of magnitude. This maintains high accuracy and resolution. Apparatus of the Invention A device for determining distances to cable damage sites, comprising a power button connected via a starter generator unit to a first input of a probe driver unit, a unipolar pulse driver unit, a pulse counter, the corresponding outputs of which are connected to the inputs of a restart pulse driver unit, the output of which is connected to the second input of the unit Shaper pulse generator first time delay unit, the input of which is connected to the output of the start-pulse generator unit and the R-output of the pulse counter, the output of the first time delay unit is connected to the S-input of the RS-flip-flop unit and to the R-input of the time meter unit, the corresponding output of the impulse counter is connected to the R-input of the RS-flip-flop block, the output of which is connected to the J-input of the time interval meter block, the second time delay block, the output of which is connected to, terminals for connecting the object Control, characterized in that, in order to improve the measurement accuracy, phase modulator, matched filter and comparator- blocks are introduced into it, and the input of the phase modulator block is connected to the output of the shaping block of the probe pulses, the outputs of the phase modulator block are connected to the corresponding inputs of the matched filter unit, the output of which is connected to the input of the unipolar pulse generator unit, the output of which is connected to the comparator unit, the output of which is connected to the S-input of the pulse counter. Sources of information taken into account in the examination 15 1, USSR Author's Certificate No. 573780, cl. G 01 R 31/08, 1976.