SU382979A1 - DEVICE FOR DETERMINATION OF DISTANCES TO THE DAMAGE OF CABLE - Google Patents

Description

one

The invention relates to telecommunications.

Devices for determining the distance to a cable damage site are known, comprising a clock pulse generator, a probe pulse generator, the output of which is used to connect the cable to be tested, a linearly varying voltage generator, and two integrating capacitors connected to a DC voltage meter.

However, the known devices require the presence of a high-precision delay system for measuring pulses, are not sufficiently high performance and are not reliable enough.

The aim of the invention is to improve the accuracy and reduce the measurement time.

For this, the proposed device is equipped with an additional linear voltage generator, having a time-pulse converter at the input. One input of this converter is connected to the output of the generator of probe pulses, and the other to the output of the clock generator and the input of the first generator of linearly varying voltage. The outputs of both generators of linearly varying voltage are connected to integrating capacitors.

To reveal the nature of damage to the cable, the time-pulse converter input is connected to the output of the probe pulse generator through the shaper of the same-pole pulses.

To determine the distance between two adjacent cable inhomogeneities, the output of the clock generator is connected to the input of the generator of a linearly varying voltage and one of the inputs of a time-pulse converter through a delay unit.

FIG. 1 shows a block diagram of the proposed device; in fig. 2 - diagrams of Hia stresses of the outputs of individual blocks; in fig. 3 is a schematic diagram of an unipolar pulse former. The device contains (see Fig. 1) generator

1 clock pulse, 2 probe pulse generator, 3 unipolar pulse shaper, time-pulse converter 4, linear-varying voltage generator 5 p 6, integrating capacitors 7, meter 8 DC voltage and delay block 9.

The pulses from the output of the clock generator / (see Fig. 2a) simultaneously start the generator 2 probe pulses and enter

on block 9 delay.

Generator 2 probe pulses generates pulses and sends them to the controlled cable.

The pulses reflected from the cable inhomogeneities (polarity depends on the nature of the heterogeneity), as well as from the place where the cable is connected to the device, and the probe pulses enter the input of the imaging unit 3 (see Fig. 28).

Shaper 3 generates at its output unipolar pulses synchronously with incoming at its input and independent of the amplitude and polarity of the latter. A variant of the driver circuit is shown in FIG. 3. The driver itself is a one-shot on tunnel-diode 10, which is controlled via a switch // by positive pulses taken (depending on the nature of the monitored heterogeneity) either from an emitter follower on transistor 12 or on an inverter on transistor 13. Thus, the output of the one-shot will always be positive pulses, synchronous with the incoming and its input (see Fig. 2c). These pulses are amplified by an amplifier on a transistor 14 (see Fig. 3).

In the case when the switch // is connected to the transistor 12, the heterogeneity of the cable with a resistance greater than the wave one is controlled. When the switch is connected to the transistor 13, inhomogeneities with less than wave resistance are monitored.

The time-pulse converter 4 is a trigger with two separated inputs, designed to convert the latency of the reflected pulses relative to the probing to the pulses modulated in duration :.

The pulses from the output of the imaging device do not deduce the time-pulse converter 4 (trigger) from the steady state until the delayed pulse from the delay block 9 arrives at the first input of the converter 4. The delay time of block 9 is set so as to eliminate the influence of pulses reflected from the point where the monitored cable is connected to the device or from any other non-uniformity; in the latter case, the delay is set by the operator (see Fig. 2a).

The start time of converter 4 is first at the beginning of the measurement.

Simultaneously with the start-up of converter 4, the generator 6 of linearly varying voltage is started.

After a time equal to the time of passage of the probe pulse to cable heterogeneity and vice versa, the converter 4 is transferred to the initial state by a pulse arriving at the second input from the output of the driver 3. Thus, at the output of the converter 4, pulses are generated, the leading edge of which corresponds to the point where the switchable cable (measurement start),

and the back front-spot of non-uniformity (the end of the measurement), i.e., the pulse duration at the output of the transducer 4 is proportional to the distance to the fault (see Fig. 2f). These pulses drive the generator 5.

The plots shown in FIG. 2, the time points corresponding to the beginning and end of the measurement are indicated by dotted lines.

At the moment the delayed clock pulse arrives from block 9, the generators 5 and b simultaneously form linearly varying voltages. Moreover, the voltage amplitude from the output of the generator 6 is constant for

of all cycles (see Fig. 2 /), and the voltage amplitude from the output of the generator 5 is constant for a series of cycles corresponding to a single inhomogeneity (see Fig. 2g). Thus, the integrating capacitors 7 are charged on one side with a linearly varying voltage, the amplitude of which contains information about the distance, and with the other, with a linearly varying voltage of constant amplitude. In a few

The voltage cycles across the capacitors take on steady-state values, and the difference between these voltages is measured by a DC voltage meter 8. The meter reading 8 is proportional

distance to cable damage.

If it is necessary to measure the distance by two adjacent inhomogeneities, the operator, by moving the handle of the measurement start delay unit, reduces the meter to zero, and the beginning of the measurement corresponds to the first inhomogeneity. The operation of the device in this measurement is similar to that described above, only the beginning of the measurement corresponds to the first inhomogeneity, and the end of the measurement -

subsequent heterogeneity.

The error in measuring the distance depends only on how different the law of voltage variation is from the linear voltage at the outputs of the generators 5, and b, and from the accuracy class of the test instrument.

Subject invention

Claims (3)

1. A device for determining the distance to a cable damage site, comprising a clock pulse generator, a probe pulse generator, the output of which is used to connect a test conductor a cable, a generator of a linearly varying voltage, and two integrating capacitors connected to a DC voltage meter, characterized in that, in order to improve accuracy and reduce measurement time, it is equipped with an additional generator of alternating voltage with an input time-pulse a converter, one input of which is connected to the output of the probe pulse generator, and the other with the output of the clock generator the pulses and the input of the geyrator of the linearly varying voltage, the output of which, as well as the output of the additional generator of the linearly varying voltage, is connected to one of the said integrating capacitors. 2. The device according to claim 1, characterized in that, in order to detect the nature of the cable damage, the input time-pulse converter is connected to the output of the probe pulse generator through the shaper of single-pole pulses. 3. The device according to claim 1, characterized in that, in order to measure the distance between two adjacent cable irregularities, the output of the clock and mplus generator is connected to the generator input of a linearly varying voltage and one of the time-pulse converter inputs . five- FIG 3