JPH0317569A - Apparatus for detecting disconnection trouble point of electric cable - Google Patents

Abstract

PURPOSE:To simplify measuring work by allowing a pulse time width to correspond to the distance up to a disconnection trouble point and measuring said time width. CONSTITUTION:An oscillator 11 oscillates a square wave pulse and the pulse width thereof is set so as to be sufficiently larger than the required reciprocating time of the pulse up to a disconnection trouble point. Said pulse is transmitted to the conductor P of an electric wire cable C through an amplifier 12, a damping resistor 14 and an output terminal 15a and also transmitted to a differential amplifier 16 through an amplifier 13 on the other hand. Herein, when a disconnection trouble point X is present, the pulse transmitted to the conductor P from the amplifier 12 turns back at the trouble point X to be inputted to the differential amplifier 16 which in turn compares and subtracts the input to output the pulse waveform due to propagation delay to a reflected wave measuring part 3. This output waveform corresponds to the time required in the reciprocation of the distance up to the trouble point X and the measuring part 3 shapes said waveform to modulate the same to a unit pulse train and counts the number of unit pulses to make it possible to display the distance up to the trouble point X.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a device for detecting a disconnection fault point in an electric wire cable such as a heater cable. There are methods such as capacitance method and pulse method. (Problem to be solved by the invention) However, with these conventional detection methods, the measurement work is complicated. In other words, the conventional capacitance method detects the disconnection failure point. Detection involves measuring the capacitance of the wire and cable under test and comparing it with the capacitance per unit length in a healthy state, which is a complicated measurement process. In the case of measurement using the capacitance method, the measured value is affected by stray capacitance, which tends to deteriorate measurement accuracy, and various considerations must be taken during measurement work to reduce this effect. In addition, measurement using the pulse method involves inputting electrical pulses into a wire cable at regular intervals, and taking advantage of the property that these pulses reflect back at the breakage point, the pulse method measures the distance between the pulse and the breakage point. The position of the disconnection fault point is detected by measuring the round trip time. In the conventional pulse method, an oscilloscope is used to measure time, and the measurement operator measures the waveform dimensions on the cathode ray tube. Therefore, the measurement work is complicated, and it is also a cause of lubrication errors.Furthermore, since the electric pulse used in conventional pulses is a sine square wave pulse, the point of disconnection is close to the point of failure. In some cases, the reflected pulse may overlap with a larger pulse, making it impossible to detect the reflected pulse, making it difficult to detect the fault location. Furthermore, the waveform of the reflected pulse may be similar to the noise waveform. Therefore, there was a risk of erroneously detecting noise.The present invention was made based on this background, and it not only simplifies the measurement work for detecting disconnection fault points of electric wire cables, but also improves the accuracy of the measurement process. The purpose of this method is to detect the location of a disconnection fault point with high accuracy by eliminating error factors.

(Means for Solving the Problems) For this purpose, the present invention inputs a pulse signal from one end of a conductor of an electric wire cable to be measured, and provides a reflection pulse of the +'+77 pulse signal from a breakage point of the cable. and detects the position of the breakage fault point from the waveform of the reflected pulse. A pulse oscillator that emits pulses is provided, and a differential amplifier is provided that inputs the reflected pulse from the disconnection failure point of the pulse signal from the pulse oscillator and the rectangular pulse generated by the pulse oscillator to detect the pulse waveform due to propagation delay. The modulation means for modulating this pulse waveform into a unit pulse train is composed of a rectifier, a comparator, and a pulse generator, and further includes a counter that counts the number of pulses of this unit pulse train, and a display that displays the counted value of this counter. It has been established. (Function) According to the present invention, the time width of the pulse corresponding to the time required for the pulse signal to travel back and forth the distance to the disconnection fault point of the electric wire cable is set as the number of pulses of the unit pulse train corresponding to this time width. You can count with a counter and display the counted value. Therefore, there is no need to measure dimensions on an oscilloscope as in the past, which simplifies the measurement work associated with detection, and fundamentally solves the measurement errors associated with dimension measurements, resulting in high precision. Measurement becomes possible. (Example) The present invention will be explained below with reference to an example shown in the drawings. In the figure, M indicates a measuring device, and the measuring device M has a pulse signal generating section 1, a reflected pulse detecting section 2, and a reflected pulse wave time measuring section 3.

The pulse signal generator 1 includes an oscillator l1 that generates a square wave pulse for measurement, and two amplifiers 12 and 13 connected in parallel to the output terminal of the oscillator 11. The output terminal of the amplifier 12 (hereinafter referred to as the first amplifier) is
It is connected to an output terminal 15a as a measurement iM via a damping resistor 14. The other amplifier 13 (hereinafter referred to as a second amplifier) appropriately amplifies the pulse signal from the oscillator 11, and the differential amplifier 1 of the reflected pulse detection section 2
6. The reflected pulse detection unit 2 is composed of a differential amplification coffin 16, and the differential amplifier 16 receives a pulse signal from the second amplifier 13 and a pulse signal captured between the damping resistor 14 and the output terminal 15a. The reflected pulse is input, compared and subtracted. The reflected pulse wave time measuring section 3 includes a wire current device 18, a comparator 19, and a pulse generator 21, which constitute a modulation means 17, and a high-speed counter 22.
and a display 23. The rectifier N18 rectifies the output of the differential amplifier l6 to obtain a pulse waveform with a time width corresponding to the time required to travel the distance to the disconnection fault point. The comparator 19 shapes the waveform, and the pulse generator 21 modulates the input signal waveform into a unit pulse train. The high-speed force counter 22 is
It counts the number of pulses in this unit pulse train, and the display 23 displays the counted value. The output terminal 15a of the measurement i19M configured in this way,
As shown in FIG. 2(a), the conductors P and Q of the electric wire cable C to be measured are connected to the conductor P.15b for measurement. The conductors Q are electrically connected to each other at their other ends, and the output terminal 15b to which the conductor Q is connected is grounded. As shown in Figure 2 (a) below! In the pulse signal generating section l, the oscillator 11 generates a predetermined measurement square wave pulse (see Fig. 3), and this pulse is 1st and 2nd
is transmitted to amplifiers 12 and 13. The pulse width of the square wave pulse generated by this signal 41i111 is larger than the round-trip time required for the pulse to reach the disconnection fault point, and is set to be sufficiently larger than the expected round-trip time to ensure reliable measurement. ．． The pulse transmitted to the first amplifier 12 is amplified and then passed through the damping resistor 14 to the output terminal 15 of the measuring instrument M.
It is transmitted to conductor P of @ line cable C connected to a. The pulse transmitted to the second amplifier 13 is appropriately amplified as a reference signal, and the pulse is transmitted to the differential amplifier 1 of the reflected pulse detection section 2.
6 (Figure 5). If there is a disconnection fault point X in the conductor P of the electric wire cable C, the first amplifier 1
The reflected pulse wave at the disconnection failure point
(The reflected pulse waveform at point A is shown in Figure 4). This difference vJ amplification @l6 compares and subtracts these inputs and outputs a pulse waveform (Figure 6) due to propagation delay. In the reflected pulse wave time measurement section 3, the output of the differential amplifier 16 is input to a rectifier l8 and rectified (seventh
(Fig.), a pulse waveform corresponding to the time required to travel the distance from the output terminal 15 to the disconnection fault point is obtained. This pulse waveform is input to the comparator 19 to perform waveform shaping (Fig. 8). The output from the comparator 19, which has undergone waveform shaping, is input to the pulse generator 21 to facilitate measurement of the pulse width. The unit pulse train is input and modulated by unit pulses (Fig. 9), but the correspondence with time is preserved even in this modulation.The unit pulse train obtained in this way is
Next, the high speed counter 22 counts, and the counted value is displayed on the display 23. The numerical value displayed on this display 323 corresponds to the time width of the pulse waveform having the above-mentioned time width, and by displaying the numerical value multiplied by a predetermined coefficient, the distance to the disconnection fault point X can be directly displayed. You can also. According to the measuring instrument H of this embodiment, as explained above, the pulse waveform corresponding to the time width is modulated into a unit pulse train, the number of pulses of this unit pulse train is counted by a high-speed force counter, and the counted value is displayed. be able to. This eliminates the need for workers to measure dimensions on an oscilloscope as in the past, which simplifies measurement work associated with detection, and fundamentally eliminates measurement errors caused by worker measurement work. By solving this problem, highly accurate measurement becomes possible. In addition, the time required for measurement is very short.
Since the pulse voltage applied to the @ wire cable is also low, it has the advantage of having less influence on the external surroundings of the wire cable. Furthermore, since the measurement work by the operator is eliminated and digital measurement is used, it is also possible to perform so-called automatic measurement, and the workability of detecting disconnection fault points can be greatly improved. Furthermore, by using square wave pulses as measurement pulses, the range of cable lengths that can be measured can be expanded from short distances to long distances. The above explanation of the operation of the measuring instrument M is related to the case of detecting a disconnection fault point in the electric wire cable C having two core wires as shown in FIG. 2(a), but this measuring instrument M is Not limited to this, even in electric wire cables having three or more core wires, the disconnection fault point
can be detected. Furthermore, as shown in Section 2r2(b), the disconnection fault point X can be similarly detected by connecting the measuring device M between the core wire and the shield as conductors P and Q, respectively. Therefore, for example, in the case of an electric wire cable having a single core wire but also having a shield, the disconnection fault point X can be detected in the same way. Furthermore, the main purpose of the measuring instrument M of this embodiment is to detect the position of the disconnection fault point X, as described above.
It is also possible to measure the length of the cable to be measured by connecting it to the measuring device M with the other end of the cable to be measured not in a conductive state but in an open state. (Effects of the Invention) Since the present invention is configured as described above, according to the present invention, the time width of the pulse corresponding to the time required for the pulse signal to travel back and forth the distance to the disconnection fault point of the electric wire cable can be adjusted. , the number of pulses in a unit pulse train corresponding to this time width can be counted by a high-speed counter and the counted value can be displayed.Therefore, there is no need to measure dimensions on an oscilloscope as in the past, and the number of pulses in the unit pulse train corresponding to this time width can be displayed. This not only simplifies measurement work, but also enables highly accurate measurements by fundamentally solving the measurement errors that occur when measuring dimensions.

[Brief explanation of drawings]

The drawings relate to an embodiment of the present invention, and FIG. 1 is a diagram showing the configuration of a measuring device, FIGS. The figure shows the output waveform of the measurement pulse oscillator, Figure 4 shows the reflected pulse waveform, Figure 5 shows the output waveform of the second amplifier, Figure 6 shows the output waveform of the differential amplifier, and Figure 7 shows the rectifier. Output waveform diagram, No. 8
The figure shows the output waveform diagram of the comparator, and Figure 9 shows the output waveform diagram of the pulse generator. C: Electric wire cable, M: Disconnection fault detection device (measuring instrument), P, Q: Conductor (core wire), X: Disconnection fault point, 1l;
Pulse oscillator, 16; Differential amplifier, 17; Modulation means, 18; Rectification scale,

Claims (1)

[Claims] An electric wire cable in which a pulse signal is inputted from one end of a conductor of an electric wire cable to be measured, a reflected pulse of the pulse signal from a breakage fault point of the cable is detected, and a position of the breakage fault point is detected from the waveform of this reflected pulse. In the disconnection fault point detection device, a pulse oscillator is provided which transmits a rectangular pulse having a pulse width larger than the round-trip time required to reach the disconnection fault point as the pulse signal, and the pulse oscillator generates a pulse signal from the disconnection fault point. reflected pulse,
A modulation means for detecting a pulse waveform due to propagation delay by providing a differential amplifier inputting the rectangular pulse generated by the pulse oscillator and modulating the pulse waveform into a unit pulse train is composed of a rectifier, a comparator, and a pulse generator, An apparatus for detecting a disconnection fault point in an electric wire cable, further comprising a counter for counting the number of pulses of the unit pulse train, and a display for displaying the counted value of the counter.