SU263734A1 - DEVICE FOR DETERMINATION OF DISTANCE TO THE PLACE OF DAMAGE OF WIRES AND CABLES BY LOCATION METHOD 1'2 - Google Patents

Description

The known devices for determining the distance to the point of damage to wires and cables by the location method, containing a power supply unit, clock, probe and measuring pulse generators and linearly varying voltage, comparator, pulse modulator and amplifiers, are not resistant to interference on the line, not they provide high accuracy in determining the distance to the damage site and are complex in terms of design, since usually a cathode ray tube is used as an indicator.

The proposed device for improving noise immunity, accuracy and simplification is equipped with a DC voltage meter, integrators with two capacitors, two switches, a switch and a block of control pulses. The specified voltage meter is connected between the terminals of two capacitors of the integrators connected respectively to the outputs of one switch and the inputs of the other, the input of the first switch connected to the output of the amplifier, and the output of the second to the input of a pulse modulator. The control inputs of the switches are connected to the first output of the control pulse block, which is connected by its input to a clock generator and forms square pulse-meanders at the specified first output and unipolar pulses at the second output connected to the generator input of linearly varying voltage. The switch, closing and opening the circuit between the first output of the generator of linearly varying voltage and the input of the generator of probe pulses, has a control input connected to the first output of the control pulse unit.

To eliminate the influence on the operation of the spurious pulse device of the power supply and increase the stability of the power supply voltage, the power supply unit is equipped with a converter made on the basis of a push-pull semiconductor generator of rectangular control pulses, the input of the control pulse unit is connected to the collector of one of the transistors.

To isolate the measuring pulse generator from the low input impedance of the monitored cable and expand the dynamic range of the measurement, the pulse modulator can be made according to the serial circuit of the diode with the emitter-collector junction of the transistor connected to the common base and the capacitor, the offset from the second the switch and measuring pulses are applied to one of the diode electrodes, and the voltage from the monitored cable to the base of the transistor. To ensure that the delaying of the probe pulse can be controlled relative to the clock without reducing the measurement accuracy, the generator of linearly varying voltage can be made according to the scheme of charging the capacitor through a resistor from a high-potential source, to the capacitor of which is connected through a bottom and a resistor connected to an additional source connected in a key scheme with an opening threshold, adjustable emitter potential, and a signal to the switch is taken from the collector. FIG. 1 shows the basic block scheme of the device proposed; in fig. 2 and 3 are diagrams of diagrams for the input and output of blocks of FIG. one; in fig. 4 - principle electric circuit of the generator of linearly varying voltage; in fig. 5 is an electrical circuit diagram of a pulse modulator. The power converter 1 simultaneously performs the functions of a clock generator and generates square-wave meanders (see Fig. 2a), which are fed to the input of the control pulse unit 2. This unit forms at its output 1 square wavelengths half the frequency (Fig. 2.6) and unipolar rectangular pulses at its output // (Fig. 2, b). The latter start the generator 3 linearly varying voltage, producing output / short pulses (Fig. 2, d), going through the switch 4 to start the generator 5 of the probe pulses (Fig. 2, e) and at the output // linearly varying The voltage (Fig. 2, g) entering the input / comparator 6. The formation of short pulses, the front of which exactly coincides with the beginning (zero level) of a linearly varying line: a measurement that provides measurement accuracy, is achieved by the circuit shown in FIG. 4. The mentioned rectangular pulses entering the input of unit 2 lock the control key, the shunt capacitor C, allowing this capacitor to be charged simultaneously from source i through resistor Ri and from source EZ through resistor RZ. When the emitter of the TI (zero level) transistor is opened, the last opens, and a short pulse is released on its collector (Fig. 2, d) to the switch 4. At the same time, the diode Db is closed, ensuring the participation in the charge of the capacitor Ci in the charge high potential source EI (Fig. 2, g), i.e., the absence of distortion of the linearly varying voltage. The comparator 6 (Fig. 1) has an input at which the operator making the measurement sets this or that voltage level with a potentiometer. Since at the output of the comparator a pulse is released when a linearly varying voltage is reached, the time interval between the sending of the probe pulse (the front of a short pulse from generator 3) and the pulse from the output of the comparator 6 is proportional to the voltage level at its input. This time interval is directly proportional to the distance to the point of the line viewed by the operator. Therefore, the potentiometer at the input of the // comparator is calibrated in meters. The pulses from the output of the comparator 6 synchronously start the generator of measuring pulses 7 (Fig. 3, a), the pulses from the output of which fall on the input P of the pulse modulator 8. The input of this modulator receives the voltage from the monitored cable, consisting odd a clock (from control pulses from block 2) from probing and flipping: pulses together with interference (switch 4 is closed) and an even clock from interference only (switch 4 is open). From the output of the modulator 8, the pulses (Fig. 3, k) enter the amplifier-deflector 9, which increases their duration, preserving the amplitude. The extended pulses through the switch 10 alternately receive (in accordance with the control pulses from the output / block 2) an odd clock to one of the capacitors 11 and every even clock to the other. The voltage from the capacitors using the second similar switch 12 is alternately fed to the input // of the modulator 8, providing negative feedback for its stable and accurate operation in a large dynamic range. This effect is achieved using the pulse modulator circuit shown in FIG. 5. Before the arrival of the next measuring pulse from block 7, the diode Yes and the TS transistor are closed. Depending on the bias on the anode of the diode feedback from the non-switch 12 and the instantaneous value of the voltage from the measured cable at the base of the transistor to the capacitor Cz and then to the amplifier 9 comes some part of the measuring pulse (Fig. 3, k), is proportional to : on the cable at the moment of arrival of the pulse from the generator of measuring pulses 7. The corresponding parts of the measuring pulses, the amplifier-expander 9 and the switch 10 pass, recharge the capacitors 11 through the cycle, respectively, changing the shift from the feedback and the diode D2. After several cycles in a closed circuit of blocks -.9-10-11-11-12-8, the stationary mode is worked out, and a capacitance proportional to the pulse voltage on the cable at the viewing point, i.e., at a given time movement relative to probe pulse FIG. 3, l, m, n). The voltage difference from the capacitors 11 is measured by the device 13. The interference with the operator’s movement of the potentiometer knob associated with the graduated scale in meters at the input // of the unit b the instrument 13 is changed according to the pulse voltage on the cable for these distances from its beginning.

The point of the potentiometer scale, at the moment of passing which the device 13 begins to give a sharp deflection (reflected pulse), corresponds to the distance to the place of damage.

Since a noticeable displacement of the potentiometer does not occur faster than tenths of a second, during this time, ten cycles of operation of the device (frequency of the order of 10 kHz) pass and the voltage on the capacitors are processed //. Therefore, the reading of the device 13 stably corresponds to the impulse response of the line for each of its points.

Subject invention

Claims (4)

1. A device for determining the distance to damage of wires and cables by a locating method, comprising a power supply unit, generators of clock, probe and measuring pulses and a linearly varying voltage, a comparator, a PULSE modulator and amplifiers, characterized in that, in order to increase noise immunity, accuracy and control of the device, it is equipped with a DC voltage meter, integrators with two capacitors, two switches, a switch and a block of control pulses, The voltage meter is connected between the terminals of two capacitors of the integrator connected respectively to the outputs of one switch and the inputs of the other, while the input of the first switch is connected to the output of the amplifier, and the output of the second to the input of a pulse modulator, the control inputs of the switches are connected to the first output of the unit control pulses, connected by its input to a clock generator and forming nr-angle pulses, mandrels at the indicated first output, and unipolar pulses at the second output, according to connected to the input of the generator of linearly varying voltage; The above switch, closing and opening the circuit between the first generator output of the linearly varying voltage and the input of the probe pulse generator, has a control input connected to the first output of the control pulse unit. 2. The device according to claim 1, characterized in that, in order to eliminate the influence on the operation of the device of parasitic pulses of the power supply unit and increase the stability of the power supply voltage, the power supply unit is equipped with a converter made on the basis of a two-stroke semiconductor generator of rectangular pulses from whose transistors the input of the control impulse unit is connected. 3. The device according to claim 1, characterized in that, in order to decouple the generator of measuring impulses from the low input resistance of the monitored cable and to expand the dynamic measuring range, the pulse loudspeaker is made according to the series circuit of the diode with the emitter-collector junction connected over circuits, e with a common base, and a capacitor, and the offset from the output of the second switch and The measuring impulses are fed to one of the diode electrodes, and the voltage from the monitored cable to the base of the transistor. 4. The device according to claim I, characterized in that, in order to enable the delaying probe pulse to be controlled relative to the clock without reducing the measurement accuracy, the generator of linearly varying voltage is made according to the charge circuit of the capacitor through a resistor from the high-potential source, to which the capacitor is connected through a diode and a resistor connected to an additional source, the base of the transistor connected in a key circuit with an opening threshold, regulated by the emitter potential, and removed from the collector a signal to the switch. f. ABOUT From block 5