KR20000039261A - Method of measuring breaking and short points of an electric wire and appparatus thereof - Google Patents

Abstract

PURPOSE: A method and an apparatus are provided which can measure breaking and short points of an electric wire based on waves reflected from the breaking and short points when applying a pulse wave to the electric wire. CONSTITUTION: An apparatus for measuring breaking and short points of an electric wire includes: a time delay generator(11) for applying a pulse wave to the electric wire to generate an output pulse of which a width is in proportion to a delay time period when the pulse wave is reflected from the breaking and short points and for generating a breaking /short signal representing whether the electric wire is broken or short; a time difference meter(12) for measuring a width of the output pulse generatded from the time delay generator(11); a connector length meter(13) for compensating a length of a connector which is connected with the electric wire; and a display for displaying a breaking point or a short point of the electric wire based on the breaking/short signal from the time delay generator(11) and the result from the connector length meter(13). Therefore, the apparatus determines whether the electric wire is broken and short and dectects the breaking and short points.

Description

Method for measuring disconnection and short-circuit point of electric wire and its device

The present invention is to determine the disconnection and short-circuit point of the wire, in particular, the disconnection or short-circuit point is determined from the delay time between the reflected pulse and the applied pulse wave reflected back from the disconnection or short-circuit point by applying the pulse wave. Provided are a method for determining disconnection and short circuit points of an electric wire.

When there is a wire that is suspected to be disconnected or shorted, it is very convenient to not only determine whether a disconnected or shorted, but also to accurately determine the disconnected or shorted point.

According to the prior art, there is a method of determining whether a disconnection or a short circuit is performed by using a multitester. A radar that analyzes the distance to a reflection point and the properties of a reflector by applying a signal to a measurement target and observing the reflected signal There is an application of TDR (Time Domain Reflectometry) which is a basic technology. However, the technique using TDR has the disadvantage that the cost is very expensive.

SUMMARY OF THE INVENTION The present invention has been made to solve the problems of the prior art as described above, and an object of the present invention is to provide a method and apparatus for accurately determining disconnection and short circuit points of an inexpensive wire.

It is still another object of the present invention to provide a method and apparatus for measuring disconnection and short-circuit points of an electric wire that can distinguish the types of disconnected or shorted electric wires by measuring the characteristic impedance of the electric wire to be measured.

1 is a block diagram of an apparatus for determining disconnection and short circuit points of an electric wire according to an embodiment of the present invention;

2 is a detailed configuration diagram of a time delay generator in the apparatus according to the present invention;

Figure 3 shows the waveform inside the time delay generator when the wire is disconnected,

Figure 4 shows the waveform inside the time delay generator when the wire is shorted,

5 is an example of a logic circuit of a time delay generator in the apparatus of the present invention;

Figure 6 is an example of how the disconnection and short circuit measuring device is connected to the measurement target wire,

7 is a detailed configuration diagram of a time delay generator including a delay unit.

8 is a view for explaining a method for measuring characteristic impedance in the case of a disconnected wire;

9 is a view for explaining a method for measuring characteristic impedance in the case of a shorted wire;

10 is a detailed configuration diagram of a time delay generator in the apparatus according to the present invention to which a function of protecting a pulse generator circuit is added.

FIG. 11 is a diagram for explaining the change in pulse waveform according to temperature, taking the case where the wire is disconnected;

12 is a diagram for explaining a method for resetting a reference voltage in response to a change in temperature.

Explanation of symbols on the main parts of the drawings

11: time delay generator 12: time difference measuring instrument

13 connector length compensation portion 14 display unit

21, 71: pulse generator 22, 72: first reference voltage generator

23, 73: first comparator 24, 74: second reference voltage generator

25, 75: second comparator 26, 76: logic circuit

77: delay unit

In order to achieve the above object, an apparatus for determining a point by recognizing defects of disconnection and short circuit of the wire according to the present invention, applying a pulse wave to the measurement target wire, reflected at the defect point, the width of the delay time A time delay generator for generating an output pulse having a signal and generating a disconnection / short signal indicating a type of disconnection or short circuit according to the phase of the reflection pulse; A time difference measuring device for precisely measuring the width of the pulse from an output pulse having a width equal to the delay time generated by the time delay generator; A connector length correction unit for performing correction in consideration of the length of the connector for connecting to the measurement target wire from the result of the time difference measuring instrument; And a display unit for displaying the type of disconnection or short circuit and the disconnection or short circuit point from the disconnection / short signal from the time delay generator and the result from the connector length compensation unit.

In addition, in order to achieve the above object, the disconnection and short-circuit point determination method of the wire according to the present invention, the step of applying a pulse wave to the measurement target wire; Recognizing a reflected pulse that the pulse wave applied in the step travels in the wire and is reflected at the disconnection or short circuit point and returned; Measuring a delay time between the applied pulse wave and the reflected pulse; And determining the disconnected or shorted point in consideration of the propagation speed of the pulse in the wire from the delay time.

Hereinafter, a method and apparatus for determining disconnection and short circuit points of a wire according to an exemplary embodiment of the present invention will be described in detail with reference to the accompanying drawings.

When a pulse wave is applied to the wire, the pulse wave travels along the wire and is reflected back at the disconnection or short circuit point. The pulse wave propagates in the wire and is reflected back from the disconnection or short-circuit point because the characteristic impedance of the wire suddenly changes at the disconnection point with infinite impedance and the short-circuit point with zero impedance. That is, the pulse wave generates the reflected wave at the point where the impedance changes during the progression.

Using this property, by measuring the propagation velocity of the pulse wave in the wire and the delay time from applying the pulse wave to returning it, it is possible to calculate the distance of the disconnected or shorted point from the point where the pulse is applied. have.

In general, since the propagation speed of the pulse wave proceeds very fast at a speed close to the speed of light in the wire, the delay time until the pulse wave is applied and returns is very short. Therefore, in order to determine the disconnection or short-circuit point, a time difference measuring instrument capable of measuring such a very short delay time should be used. For example, using a time difference measuring instrument that can measure the time difference in units of 10 ps (100 billionth of a second), it can be measured in units of 1 mm, assuming that the pulse wave proceeds at the speed of light.

In addition, when the pulse wave proceeds in the wire and meets the disconnection point, the phase does not change but is reflected back. have.

1 is a block diagram of an apparatus for determining disconnection and short circuit points of an electric wire according to an exemplary embodiment of the present invention.

As shown in Fig. 1, the disconnection and short-circuit point discriminator of the wire according to the present invention is composed of a time delay generator 11, a time difference measuring instrument 12, a connector length compensating portion 13, and a display portion 14. .

The time delay generator 11 is connected to the wire to be measured. The time delay generator 11 generates a pulse wave and applies it to the measurement target wire, and then recognizes the returned pulse and generates an output pulse having a width equal to the delay time, and whether the line is short or short depending on the phase of the reflected pulse. Generates a disconnection / short signal indicating the type of signal.

The time difference measuring instrument 12 accurately measures the width of the pulse from an output pulse having a width corresponding to the delay time generated by the time delay generator 11.

The connector length compensator 13 performs a correction such as subtracting the length of the connector for connecting to the measurement target wire from the result of the time difference measuring instrument 12.

The display unit 14 displays the type of disconnection or short circuit and the disconnection or short circuit point from the disconnection / short signal from the time delay generator 11 and the result from the connector compensator 13.

In the apparatus for determining disconnection or short-circuit point of the wire according to the present invention, the time delay generator 11 for discriminating the type of disconnection or short-circuit and generating a pulse having a width equal to the delay time of the reflection pulse is a key component. to be. The time delay generator will be described with reference to FIGS. 2, 3, 4, and 5.

2 is a detailed configuration diagram of a time delay generator in the apparatus according to the present invention.

As shown in Fig. 2, the time delay generator, which is a key component in the apparatus according to the present invention, includes a pulse generator 21, a first reference voltage generator 22, a first comparator 23, and a second reference voltage generator. (24), the second comparator 25, and the logic circuit 26.

The pulse generator 21 generates a pulse to be applied to the measurement target wire. The first reference voltage generator 22, the first comparator 23, the second reference voltage generator 24, and the second comparator 25 are for recognizing the reflected pulse, and the logic circuit 26 is a disconnection / short circuit signal. Produces an output pulse with a pulse width equal to the delay time.

The incident pulse generated by the pulse generator 21 is applied to the wire to be measured and travels along the wire to be measured and is reflected at the disconnection or short-circuit point. Reflected pulses proceed to the comparators, and pulses in which the incident pulse and the reflected pulse are added are applied to the first comparator 23 and the second comparator 25.

Since the phases of the reflection pulses are different in the case of a single line and a short circuit, the waveforms of the output pulses output from the incident pulse, the reflected pulse, and the logic circuit will be described below.

3 is a waveform when the wire is disconnected.

After the delay time elapses after the incident pulse is applied, the reflected pulse is generated, and the reflected pulse has the same phase as the incident pulse. The first comparator 23 and the second comparator 25 are input with pulses in which an incident pulse and a reflection pulse are added. The first reference voltage is set to have a size equal to or smaller than the size of the incident pulse so as to sense the incident pulse and the reflected pulse together so that the first comparator 23 is generated when the incident pulse is detected. The second reference voltage is set to have a magnitude between the magnitude of the incident pulse and the sum of the incident pulse and the reflected pulse so that the reflected pulse is detected so that the second comparator 25 is generated when the reflected pulse is detected.

4 is a waveform when the wire is short-circuited.

After the delay time elapses after the incident pulse is applied, the reflected pulse is generated, and the reflected pulse has a phase changed 180 degrees with the incident pulse. The first comparator 23 and the second comparator 25 are input with pulses in which an incident pulse and a reflection pulse are added. The first reference voltage is set to have a magnitude less than or equal to the magnitude of the incident pulse so as to sense the incident pulse and the reflected pulse together so that the first comparator 23 generates a signal when the incident pulse and the reflected pulse are detected. Since the second reference voltage is set to have a magnitude between the magnitude of the incident pulse and the magnitude (absolute value) of the incident pulse and the reflected pulse, there is no output of the second comparator 25 when the wire is shorted. The output of the first comparator 23 represents the delay time.

The logic circuit 26 outputs a pulse signal having a pulse width as long as a disconnection / short signal and a delay time from the output waveforms of the first comparator 23 and the second comparator 25 as described above. 5 shows an example of a logic circuit of a time delay generator in the apparatus of the present invention.

3 and 4, since the output of the first comparator is different in the case of a disconnection and a short circuit, the output of the first comparator may be used as a disconnection / short circuit. Of course, since the output of the second comparator is also different in the case of a disconnection and a short circuit, the output of the second comparator may be used as a disconnection / short circuit.

In order to express the delay time, when the output of the first comparator and the second comparator is logically operated in both the disconnection and the short circuit, the delay of the logic circuit as shown in Figs. Time output pulse can be obtained. FIG. 5 illustrates a case where an output obtained by performing an XOR operation on the output of the first comparator and the output of the second comparator is used as a delay time output pulse of a logic circuit.

In the device according to the invention, the time difference measurer 12 measures the time corresponding to the width of the output pulse of the time delay generator 11. For more accurate measurements, the accuracy of the time difference meter must be high. For example, if the time difference can be measured in units of 10 ps (100 billionth of a second), it can be measured in units of 1 mm even if the propagation velocity of the pulse in the wire is luminous flux.

In the device according to the present invention, the connector length compensator 13 performs correction such as subtracting the length of the connector for connecting the measuring device to the measurement target wire from the measurement result of the time difference measuring instrument 12.

6 shows the disconnection and short circuit measuring devices connected to the measurement target wire. Since the delay time measured by the time difference measurer 12 includes a time for advancing the length of the connector, the length of the connector known in advance is corrected.

As an example of a method for correcting the length of a connector, a negative reset and a subtraction method may be performed by resetting the value corresponding to the delay time as much as advancing the length of the connector to the internal counter of the time difference measuring instrument 12. The delay time during the connector is subtracted from the delay time measured at.

Another method of correcting the length of the connector is to subtract the value corresponding to the delay time as the length of the connector from the delay time output from the time difference measuring instrument 12.

On the other hand, in order to minimize the reflection of the pulse in the connector, the impedance of the connector is preferably equal to the impedance of the wire to be measured. Since the types of wires to be measured vary, the present inventors recommend preparing a connector set having various impedances as an example.

In general, since the impedance of the connector is different from the impedance of the wire to be measured, the reflected wave occurs in the connector. Compared to the impedance imbalance at the disconnection or short circuit point, the impedance imbalance at the connector is not so severe that the reflected pulse reflected at the connector is very small in size.

Even if the size of the reflected pulse reflected from the connector is very small, an error may occur, so the present invention proposes a method for taking this into consideration. In other words, the length of the connector is known in advance, so if you do not recognize the reflected pulse during this time, you can predict the delay time of the reflected wave from the connector. You may not receive it.

For this purpose, the second comparator 25 does not recognize the reflected pulse during the delay time in which the reflected wave generated in the connector returns after the delay is added to the time delay generator 11 to generate the pulse from the pulse generator 21. The second comparator 25 is disabled so that the second comparator 25 is enabled after a delay time for returning the reflected wave generated from the connector has elapsed. 7 is a detailed configuration diagram of the time delay generator including the delay unit 77.

In the method for measuring disconnection and short circuit according to the present invention described above and the apparatus, it may be necessary to determine the type of the disconnection or short circuit wire. Since the characteristic impedance is different depending on the type of wire, the reference voltage of the comparator should be set differently in the present invention. For this purpose, there must be prior information on the characteristic impedance of the wire to be measured. Information on the characteristic impedance of the wire to be measured would also be very convenient if it could be obtained using a single-wire or short-circuit measuring device. To this end, the present invention also proposes a method of measuring the characteristic impedance of the wire to be measured by scanning the reference voltage of the comparator.

8 is a view for explaining a method for measuring characteristic impedance in the case of a disconnected wire.

FIG. 8A is a general output waveform of the first comparator, the second comparator, and the logic circuit in the case of a disconnected wire, and FIG. 8B is a diagram illustrating scanning the second reference voltage downward while the first reference voltage is fixed. 8C is a view for explaining the first reference voltage and the second reference voltage when the width of the output pulse of the logic circuit suddenly decreases.

The height of the first pulse, indicated by the arrow in Fig. 8A, varies depending on the characteristic impedance of the wire. In detail, when the wire having the high characteristic impedance is measured, the height of the first pulse is higher. Therefore, by measuring the height of the first pulse, the characteristic impedance of the wire can be known, and hence the type of wire.

In order to measure the height of the first pulse, while the waveform as shown in FIG. 8A is output, the second pulse voltage is gradually moved downward until the width of the output pulse of the logic circuit is suddenly reduced. The magnitude of the second reference voltage when the width of the output pulse of the logic circuit suddenly decreases becomes the height of the first pulse. This will be described in more detail with reference to Figs. 8B and 8C. 8B illustrates a case where the second reference voltage is slightly higher than the first pulse, and FIG. 8C illustrates a case where the second reference voltage has just passed the first pulse. As shown in Fig. 8C, in this case, the width of the output pulse of the logic circuit is abruptly reduced, and the height of the second reference voltage at this time is the height of the first pulse.

9 is a view for explaining a method for measuring characteristic impedance in the case of a shorted wire.

9A is a general output waveform of a first comparator, a second comparator, and a logic circuit in the case of a shorted wire, and FIG. 9B is a diagram illustrating scanning of a second reference voltage while the first reference voltage is fixed. 9C is a diagram for explaining a first reference voltage and a second reference voltage when the output of the logic circuit becomes an impulse waveform.

The height of the first pulse, indicated by the arrow in Fig. 9A, varies depending on the characteristic impedance of the wire. In order to measure the height of the first pulse, it is checked when the output of the logic circuit becomes an impulse waveform while moving the second reference voltage downward while the waveform shown in FIG. 9A is output. When the output of the logic circuit becomes an impulse waveform, the magnitude of the second reference voltage becomes the height of the first pulse. This will be described in more detail with reference to Figs. 9B and 9C. 9B illustrates a case in which the second reference voltage is slightly higher than the first pulse, and FIG. 9C illustrates a case in which the second reference voltage has just passed the first pulse. As shown in Fig. 9C, the output of the logic circuit in this case is an impulse waveform, and the height of the second reference voltage at this time is the height of the first pulse.

The following proposes a method for protecting a pulse generator circuit in an apparatus for measuring disconnection and short circuit points of a wire according to the present invention. Fig. 10 is a detailed configuration diagram of the time delay generator in the apparatus according to the present invention to which the function of protecting the pulse generator circuit is added.

In FIG. 7, since the time delay generator serves to measure the time difference between the outputs of the first comparator 73 and the second comparator 75, the pulse generator 71 generates the output of the second comparator. There is no need to keep the pulse on and on. Therefore, the output of the second comparator is connected to the disable of the pulse generator to disable the pulse generator immediately after performing the role of the time delay generator. As a result, not only unnecessary operation of the pulse generator circuit can be prevented, but also an overload of the pulse generator can be prevented when the short circuit is measured, thereby protecting the pulse generator 71 circuit.

Next, since the voltage generated in the pulse generator may be changed according to the temperature, the output voltage of the pulse generator is compensated according to the temperature change.

The voltage generated by the pulse generator can vary with temperature. The final output of most pulse generators consists of an emitter-follower. The emitter-follower is a circuit that produces an output voltage (V _o ) by lowering the input voltage (V _i ) by the base-emitter voltage (V _be ) of the transistor. The base-emitter voltage (V _be ) of the transistor is typically about 0.7V. The base-emitter voltage (V _be ) must be constant for the pulse generator to produce a pulse of constant height. However, the base-emitter voltage (V _be ) has a characteristic of varying with temperature, and the temperature decreases by 2㎷ as the temperature increases by 1 ° C. Therefore, when the operating temperature of the pulse generator increases by 10 ° C, the base-emitter voltage (V _be ) decreases by 0.02V. As a result, the output voltage is increased to cause a change in the output voltage of the pulse generator. Therefore, it is necessary to compensate the output voltage of the pulse generator according to the change of temperature.

FIG. 11 is a diagram illustrating a change in the pulse waveform according to temperature, taking the case where the wire is disconnected, for example. When the temperature is low, the upper part of FIG. 11 shows when the temperature is high.

As shown in Fig. 11, when the temperature rises, the output pulse waveform rises upward as a whole. However, since the first reference voltage and the second reference voltage do not change, the comparison reference voltage with respect to the output pulse waveform is relatively low. If the height of the reference voltage with respect to the pulse waveform is not constant, the result of measuring the distance to the disconnection point is not only changed. Also, when distinguishing the characteristic impedance of the wire to be measured, the height of the first pulse is recognized differently, thereby causing an error.

In order to solve the problem caused by the temperature change as described above, the present invention proposes a method for resetting the reference voltage with reference to the output voltage of the pulse generator. For this purpose, the voltage before generating the pulse in the pulse generator is read using an A / D converter or the like, and the difference with the original voltage is reflected in the reference voltage setting. A method of resetting the reference voltage according to the temperature change will be described with reference to FIG. 12.

12A shows the pulse waveform and the reference voltage before the temperature rises. At this time, the voltage before pulse generation is a known value. 12B shows the pulse waveform and the reference voltage after the temperature rises. As the temperature rises, the pulse waveform rises up overall, but the reference voltage remains unchanged, so the relative relationship between the pulse waveform and the reference voltage changes with the temperature rise. In this case, if you read the voltage before the pulse generation using A / D converter, you can know the change of voltage before the pulse generation according to the temperature rise. The relative relationship with the reference voltage does not change. 12C shows that the reference voltage is reset by an amount corresponding to the change of the voltage before the pulse generation as the temperature rises.

In the present invention, it is also intended to perform continuous automatic zero adjustment to minimize the error of the disconnection and short-point measuring device. Disconnection and short-point measuring devices need to perform zero adjustment as the length and temperature of the connector change. When the wire to be measured is not connected to the connector, it is necessary to adjust the zero point so that the distance is zero as a result of measurement. However, it would be very inconvenient if the user had to adjust the zero point every time before the measurement, and the measurement result would be inaccurate if the user did not make the zero point adjustment. Therefore, in the present invention, the zero point adjustment is automatically performed periodically. The automatic measurement is performed periodically to check whether the connector is connected or the cable to be measured is connected to the connector. If only the connector is connected, the distance is zero as a result of the measurement.

This automatic zero adjustment is intended to compensate for changes in measurements over changes in length and temperature of the connector. The zero point adjustment according to the change of the connector length and the zero point adjustment according to the change of the temperature are somewhat different. First, the zero point adjustment according to the change in the connector length is performed by subtracting the length of the connector from the measurement result. On the contrary, the zero point adjustment according to the temperature change is performed by resetting the reference voltage.

By further expanding the concept of the disconnection and short circuit measuring method and the apparatus according to the present invention described above, it is possible to determine the point where the impedance changes due to any defect in the measurement target wire. In addition, the type of the defect can be detected in consideration of the phase of the reflected pulse. In addition, according to the present invention, it is possible to know the type of the wire to be measured by measuring the characteristic impedance, and the present invention provides a method for protecting a pulse generator, a temperature-based correction, and a method for performing automatic zero point adjustment.

Claims (13)

In the device for determining the point by recognizing the disconnection and short circuit of the wire, Applying a pulse wave to the wire to be measured, generating an output pulse reflected at the defect point and having a width equal to the delay time, and generating a disconnection / short signal indicating the type of disconnection or short circuit according to the phase of the reflection pulse. Time delay generator; A time difference measuring device for precisely measuring the width of the pulse from an output pulse having a width equal to the delay time generated by the time delay generator; A connector length correction unit for performing correction in consideration of the length of the connector for connecting to the measurement target wire from the result of the time difference measuring instrument; And And a display unit for displaying the type of disconnection or short circuit and the disconnection or short circuit point from the disconnection / short signal from the time delay generator and the result from the connector length compensator. Device. The method of claim 1, wherein the time delay generator, A pulse generator for generating a pulse to be applied to the measurement target wire; A first comparator and a second comparator configured to recognize a reflected pulse by inputting a pulse obtained by adding an incident pulse and a reflected pulse; And And a logic circuit for generating a disconnection / short signal from the outputs of the first comparator and the second comparator and an output pulse having a pulse width equal to the delay time. The method of claim 2, The reference voltage of the first comparator is set to have a magnitude less than or equal to the incident pulse to generate a signal when the incident pulse is detected, and the reference voltage of the second comparator is incident to the magnitude of the incident pulse so that the reflected pulse is detected. A device for determining disconnection and short circuit points of a wire, which is set to have a magnitude between a pulse plus a magnitude (absolute value) of the reflected pulse and generates a signal when the reflected pulse is detected. The logic circuit of claim 2, wherein the logic circuit comprises: And an output signal of the first comparator or the second comparator as a disconnection / short signal. The logic circuit of claim 2, wherein the logic circuit comprises: And an output signal of the first comparator and the output signal of the second comparator are output as a signal representing a delay time due to a reflected pulse. The method of claim 2, wherein the time delay generator, After generating the pulse from the pulse generator, the second comparator is disabled so that the second comparator does not recognize the reflected pulse after the reflected wave generated from the connector is returned, and the delayed return of the reflected wave generated from the connector is returned. And means for enabling the second comparator after a period of time has elapsed. The method of claim 2, wherein the time delay generator, Disabling the pulse generator in accordance with the output of the second comparator. The method of claim 2, wherein the time delay generator, Apparatus for determining disconnection and short-circuit points of a wire, characterized in that reflecting the difference in the output voltage of the pulse generator in accordance with the change in temperature to the reference voltage of the first and second comparators. In a method for determining disconnection and short circuit points of an electric wire, Applying a pulse wave to a measurement target wire; Recognizing a reflected pulse that the pulse wave applied in the step travels in the wire and is reflected at the disconnection or short circuit point and returned; Measuring a delay time between the applied pulse wave and the reflected pulse; And And determining a disconnected or shorted point in consideration of the propagation speed of a pulse in the wire from the delay time. The method of claim 9, wherein The method of claim 1, further comprising the step of correcting the length of the connector connected to the wire to be measured. The method of claim 10, wherein And determining whether the wire is disconnected or shorted from the phase of the reflected pulse. The method of claim 9, wherein And detecting a kind of the wire to be measured by measuring a characteristic impedance of the wire to be measured by scanning a reference voltage for measuring a delay time between the applied pulse wave and the reflected pulse. How to determine the short point. The method of claim 9, wherein And periodically performing automatic zero adjustment.