JP2003185694A - Method and apparatus for inspection of coaxial cable - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inspection apparatus for a coaxial cable by which the existence of the damage of a metal shield in the coaxial cable can be inspected by a low-cost and simple method and by which the existence of the damage can be judged quantitatively. <P>SOLUTION: The inspection method for the coaxial cable in which the existence of the damage of the metal shield in the coaxial cable is inspected nondestructively is constituted so as to be provided with a process in which an electrostatic noise is applied to a casing of the coaxial cable, and a process in which a signal at a prescribed level or more generated in a core wire in the coaxial cable due to its application is detected. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technical field for nondestructively inspecting a metal shield (for example, an aluminum shield) of a coaxial cable for damage such as scratches or breakage.

[0002]

2. Description of the Related Art With the recent miniaturization of computer systems, smaller and lighter coaxial cables are required, and so-called aluminum shield (alpet) structures are widely used in order to realize thin coaxial cables. is doing. FIG. 5 shows an example of the cross-sectional structure of a general coaxial cable having a thin core (for example, a diameter of about 1 mm). In the coaxial cable 10 shown in FIG. 5, the core wire 11 as a signal conductor is covered with an insulator 13, and the insulator 13 is covered with an aluminum shield 1.
It has an aluminum shield structure covered with 4. In such an aluminum shield structure, the aluminum shield 14 is grounded, which has an advantage of shielding various noises from the outside.

However, such an aluminum shield structure is weak in strength as compared with a known so-called winding structure, and is susceptible to damage such as scratches and breaks. FIG. 6 shows a case where the aluminum shield 14 of the coaxial cable 10 is damaged (however, the outer cover 15 of the coaxial cable 10 is not shown). As shown in FIG. 6, when the aluminum shield 14 of the coaxial cable 10 is damaged, various characteristics of the coaxial cable 10 are affected, and, for example, the characteristic impedance is deteriorated or uneven, the propagation delay time is lengthened, and Problems such as deterioration of the transmission waveform may occur. As a result, the performance or operation of the computer system may be seriously hindered.

In order to inspect the aluminum shield 14 of the coaxial cable 10 for damages such as scratches and breaks, conventionally, an inspection method using an X-ray device or the outer skin 15 of the coaxial cable 10 is peeled off. Alternatively, an inspection method involving destruction such as melting is known.

[0005]

However, in the inspection method using the conventional X-ray apparatus, it is difficult to detect fine damage depending on the resolution, and it is difficult to make a reliable quantitative judgment. Further, there is a problem that an expensive and large-scale device is required to realize a high detection rate.

Further, in the inspection method involving destruction such as peeling or melting of the cable outer skin, there is a problem that only a typical coaxial cable 10 can be inspected and all the coaxial cables 10 cannot be inspected.

Therefore, the present invention has been made in view of the above problems, and it is possible to inspect the presence or absence of damage to a metal shield in a coaxial cable by a nondestructive and inexpensive and simple method. An object of the present invention is to provide a coaxial cable inspection method and a coaxial cable inspection device capable of quantitatively determining the presence or absence of breakage.

[0008]

In order to solve the above-mentioned problems, the invention according to claim 1 is a method of inspecting a coaxial cable for non-destructively inspecting a metal shield in a coaxial cable for damage. It is configured to include a step of applying electrostatic noise to the outer cover of the coaxial cable, and a step of detecting a signal of a predetermined level or higher generated in the core wire of the coaxial cable by the application. Damage to a metal shield in a coaxial cable includes scratches, breaks, cuts, cracks, breaks, and the like.

According to the first aspect of the invention, electrostatic noise is applied to the outer cover of the coaxial cable. Then, by the application, a signal of a predetermined level or more generated in the core wire which is the signal conductor in the coaxial cable is detected. Therefore, if such a signal is detected, it can be known that the metal shield in the coaxial cable is damaged, and therefore the presence or absence of damage to the metal shield in the coaxial cable can be inspected by a non-destructive and inexpensive method. Furthermore, it is possible to quantitatively determine the presence or absence of the damage.

According to a second aspect of the present invention, in the coaxial cable inspecting method according to the first aspect, signal detecting means for detecting a signal of the predetermined level or higher is connected to one end of a core wire of the coaxial cable. To configure.

According to the second aspect of the present invention, by connecting the signal detecting means to one end of the core wire of the coaxial cable, the presence or absence of damage to the metal shield of the coaxial cable is non-destructive, and an inexpensive and simple method. Can be inspected, and the presence or absence of the damage can be quantitatively determined.

According to a third aspect of the present invention, in the coaxial cable inspection method according to the second aspect, the signal detecting means has at least a data signal input terminal, a clock signal input terminal, and a signal output terminal. In the circuit, a high-level signal is always input from the data signal input terminal, and the clock signal input terminal is connected to one end of a core wire of the coaxial cable.

According to the third aspect of the present invention, when a signal of a predetermined level or higher is generated in the core wire of the coaxial cable due to the application of electrostatic noise to the outer sheath of the coaxial cable, the clock signal input terminal of the flip-flop circuit is The signal is input, and the flip-flop circuit recognizes the signal. As a result, a high-level signal is output from the signal output terminal of the flip-flop circuit, so that the presence or absence of damage to the metal shield of the coaxial cable can be inspected in a non-destructive, inexpensive and simple manner. The presence or absence of the damage can be quantitatively determined.

According to a fourth aspect of the present invention, in the coaxial cable inspection method according to the second or third aspect, the other end of the core wire of the coaxial cable is grounded via a resistor.

According to the fourth aspect of the present invention, the other end of the core wire of the coaxial cable is grounded via the resistor, so that the state of the core wire, which is the signal conductor of the coaxial cable, can be stabilized.

According to a fifth aspect of the present invention, in the coaxial cable inspection method according to the fourth aspect, the resistance value of the resistor is made equal to the characteristic impedance value of the coaxial cable.

According to the invention described in claim 5, by making the characteristic impedance value of the coaxial cable equal,
The state of the core wire that is the signal conductor in the coaxial cable,
It can be made more stable.

According to a sixth aspect of the present invention, in the coaxial cable inspection method according to the second or third aspect, a signal of a level smaller than the predetermined level is always input from the other end of the core wire of the coaxial cable. To configure.

According to the invention of claim 6, by constantly inputting a signal of a level smaller than the predetermined level from the other end of the core wire of the coaxial cable, the predetermined level or more generated in the core wire of the coaxial cable is exceeded. Since the getter can be applied to the signal of No. 3, even if the damage of the metal shield in the coaxial cable is small, the damage can be accurately detected.

According to a seventh aspect of the present invention, in the coaxial cable inspection method according to the second or third aspect, two resistors are connected in parallel to the other end of the core wire of the coaxial cable, and one of the resistors is connected. A high level signal is always input from one end, and one end of the other resistor is grounded.

According to the seventh aspect of the present invention, the desired signal detection sensitivity can be easily set by appropriately selecting the resistance values of the two resistors.

The present invention according to claim 8 is a coaxial cable inspection device for non-destructively inspecting a coaxial cable for the presence or absence of breakage of a metal shield, the noise applying means applying electrostatic noise to the outer sheath of the coaxial cable. And signal detection means for detecting a signal of a predetermined level or higher generated in the core wire of the coaxial cable by the application.

According to the invention described in claim 8, the coaxial cable inspection method according to claim 1 can be realized by the coaxial cable inspection device.
The presence or absence of damage to the metal shield in the coaxial cable can be non-destructively inspected by an inexpensive and simple method, and the presence or absence of the damage can be quantitatively determined.

According to a ninth aspect of the present invention, in the coaxial cable inspection apparatus according to the eighth aspect, the signal detecting means is connected to one end of a core wire of the coaxial cable.

According to the ninth aspect of the invention, the coaxial cable inspecting method according to the second aspect can be realized by the coaxial cable inspecting apparatus.

According to a tenth aspect of the present invention, in the coaxial cable inspection apparatus according to the ninth aspect, the signal detecting means has at least a data signal input terminal, a clock signal input terminal, and a signal output terminal. In the circuit, a high-level signal is always input to the data signal input terminal, and one end of a core wire of the coaxial cable is connected to the clock signal input terminal.

According to the tenth aspect of the invention, the coaxial cable inspection method according to the third aspect can be realized by the coaxial cable inspection apparatus.

The eleventh aspect of the present invention is the coaxial cable inspection apparatus according to the ninth or tenth aspect, further comprising a resistor connected to the other end of the core wire of the coaxial cable, and one end of the resistor is grounded. Configure as is.

According to the eleventh aspect of the present invention, the coaxial cable inspection method according to the fourth aspect can be realized by the coaxial cable inspection device.

According to a twelfth aspect of the present invention, in the coaxial cable inspection apparatus according to the eleventh aspect, the resistance value of the resistor is equal to the characteristic impedance value of the coaxial cable.

According to the twelfth aspect of the invention, the coaxial cable inspection method according to the fifth aspect can be realized by the coaxial cable inspection apparatus.

According to a thirteenth aspect of the present invention, in the coaxial cable inspection apparatus according to the ninth or tenth aspect, a signal of a level smaller than the predetermined level is always input from the other end of the core wire of the coaxial cable. The signal input means is further provided.

According to the thirteenth aspect of the invention, the coaxial cable inspection method according to the sixth aspect can be realized by the coaxial cable inspection apparatus.

According to a fourteenth aspect of the present invention, in the coaxial cable inspection apparatus according to the ninth or tenth aspect, further comprising two resistors connected in parallel to the other end of the core wire of the coaxial cable, one of the resistors is provided. A high-level signal is always input from one end of the resistor, and one end of the other resistor is grounded.

According to the fourteenth aspect of the present invention, the coaxial cable inspection method according to the seventh aspect can be realized by the coaxial cable inspection apparatus.

[0036]

Preferred embodiments of the present invention will be described below with reference to the accompanying drawings. (First Embodiment) First, a coaxial cable inspection method according to the first embodiment of the present invention will be described with reference to FIGS. 1 and 2. FIG. 1 is a diagram showing a schematic configuration of a coaxial cable inspection device for carrying out the coaxial cable inspection method according to the first embodiment. In FIG. 1, the coaxial cable to be inspected is the same as the thin coaxial cable 10 in FIG.

As shown in FIG. 1, the coaxial cable inspection apparatus 1 includes an electrostatic noise generator 2 as noise applying means.
0, and a flip-flop circuit 30 as signal detection means
And a terminating resistor RT as a resistor.

The electrostatic noise generator 20 has, for example, about 2
It generates an impulsive electrostatic noise of 00V. The electrostatic noise generator 20 is used to apply the electrostatic noise to the outer cover 15 of the coaxial cable 10. The voltage applied to the outer cover of the coaxial cable 10 is not limited to 200V, and is not limited to 200V.
Even if electrostatic noise of 0V to several kV is applied,
The effect of the present invention can be obtained.

The flip-flop circuit 30 is for detecting a signal of a predetermined level or more generated in the core wire 11 which is a signal conductor in the coaxial cable 10 due to the application of such electrostatic noise, and as shown in the drawing, a data signal. It has an input terminal D, a clock signal input terminal C, a reset signal input terminal R, and a signal output terminal Q. As the flip-flop circuit 30, for example, a so-called RST flip-flop, JK flip-flop or the like can be applied.

The terminating resistor RT is used to stabilize the state of the signal conductor in the coaxial cable 10, and preferably has the same resistance value as the characteristic impedance value of the coaxial cable 10. This is to prevent reflected noise from returning from the terminating resistor RT when a signal is generated in the core wire 11 of the coaxial cable 10.

In such a configuration, a fixed high level (“1” level) signal (a signal higher than the signal detection level of the flip-flop circuit 30) is constantly output from the data signal input terminal D of the flip-flop circuit 30. input.
Such a signal is output from, for example, a DC / DC converter.

The clock signal input terminal C of the flip-flop circuit 30 is connected to one end 10a of the core wire 11 of the coaxial cable 10. Further, for example, an LED (light emitting diode) or a buzzer is connected to the signal output terminal Q of the flip-flop circuit 30.

Further, the core wire 11 of the coaxial cable 10
The other end 10b of the above is grounded via a terminating resistor RT. As a result, the core wire 11 of the coaxial cable 10 becomes 0V.

Furthermore, both ends (one end 10a) of the aluminum shield 14 as a metal shield in the coaxial cable 10 are connected.
And the other end 10b) to ground.

In such a state, the electrostatic noise generator 20 is moved along the coaxial cable 10 from one end 10a to the other end 10b, and electrostatic noise is applied to the outer cover 15 of the coaxial cable 10.

FIG. 2 shows an input signal input from the clock signal input terminal C and an output signal output from the signal output terminal Q of the flip-flop circuit 30 when electrostatic noise is applied to the outer cover 15 of the coaxial cable 10. It is the conceptual diagram which showed.

As shown in FIG. 2A, the coaxial cable 1
When the aluminum shield 14 at 0 is normal, it is hardly affected by electrostatic noise, and the level of the signal generated on the core wire 11 of the coaxial cable 10 by the application of electrostatic noise is the signal detection level of the flip-flop circuit 30 (flip block). The flip-flop circuit 30 receives an input from the clock signal input terminal C because the input signal from the clock signal input terminal C does not reach the threshold level (recognizing that the input signal is high level (“1” level)). Recognizing that the signal is low level (“0” level), the level of the output signal from the signal output terminal Q remains low level (“0” level).

On the other hand, as shown in FIG. 2B, when the aluminum shield 14 of the coaxial cable 10 is damaged such as scratches or breaks, the effect of electrostatic noise is reduced because the shielding effect is not sufficient. The level of the signal generated on the core wire 11 of the coaxial cable 10 by the application of the electrostatic noise is equal to or higher than the signal detection level of the flip-flop circuit 30, so that the input signal from the clock signal input terminal C of the flip-flop circuit 30 is high. It is recognized as the level (“1” level), and as a result, the level of the output signal from the signal output terminal Q changes to the high level (“1” level).

As a result, the LED connected to the signal output terminal Q of the flip-flop circuit 30 lights up and the buzzer sounds. That is, the electrostatic noise generator 2
0 from one end 10a to the other end 1 along the coaxial cable 10.
When moving to 0b, electrostatic noise generator 2
When 0 reaches the location where the aluminum shield 14 of the coaxial cable 10 has a damage such as a scratch or a break, the LED
Lights up and the buzzer sounds. Therefore, it becomes clear which part of the aluminum shield 14 in the coaxial cable 10 is damaged.

Further, once the output signal from the signal output terminal Q changes to the high level ("1" level), unless the reset signal is input from the reset signal input terminal R,
Since the output signal maintains a high level (“1” level) state, it is possible to retain information on damage such as scratches and breaks in the aluminum shield 14 of the coaxial cable 10.

Further, after the output signal from the signal output terminal Q once changes to the high level (“1” level), the reset signal is input from the reset signal input terminal R of the flip-flop circuit 30, and the signal output terminal Q Output signal from
After returning to the low level (“0” level), the electrostatic noise generator 20 is moved along the coaxial cable 10 again, and electrostatic noise is applied to the outer skin 15 of the coaxial cable 10. Other damage to the aluminum shield 14 in the coaxial cable 10 can be detected.

As described above, according to the first embodiment, a signal of a predetermined level (threshold level of the flip-flop circuit 30) or more generated in the core wire 11 by applying electrostatic noise to the outer cover 15 of the coaxial cable 10. Since it is configured to detect the damage, the presence or absence of damage such as scratches or breaks of the aluminum shield 14 in the coaxial cable 10 can be inspected in a non-destructive, inexpensive and simple method. It can be judged quantitatively. Further, by applying the flip-flop circuit 30 as the signal detecting means in the present invention, simplification of the circuit configuration and cost reduction can be realized. (Second Embodiment) Next, a coaxial cable inspection method according to a second embodiment of the present invention will be described with reference to FIGS. 3 and 4. FIG. 3 is a diagram showing a schematic configuration of a coaxial cable inspection device for carrying out the coaxial cable inspection method according to the second embodiment. Note that, in FIG. 3, the same components as those in the first embodiment will be described with the same reference numerals. Further, in the second embodiment, the description overlapping with the description in the first embodiment will be omitted.

As shown in FIG. 3, the coaxial cable inspection device 2 includes an electrostatic noise generator 20 as in the first embodiment.
And a flip-flop circuit 30, and further D
C / DC converter 40 and terminating resistors RT1 and RT
2 is provided. This DC / DC converter 40,
The termination resistors RT1 and RT2 function as signal input means. The parallel resistance value of the terminating resistors RT1 and RT2 is preferably the same resistance value as the characteristic impedance value of the coaxial cable 10 (where Z is the characteristic impedance of the coaxial cable, Z = (RT1 * RT2) / (RT
1 + RT2)). This is similar to the first embodiment.
This is to prevent reflected noise from returning from the terminating resistor.

In such a configuration, the coaxial cable 1
The connection state at the other end 10b of 0 is different from that in the first embodiment. As shown in FIG. 3, the terminating resistors RT1 and RT2 are connected in parallel to the other end 10b of the core wire 11 of the coaxial cable 10. The DC / DC converter 40 is connected to one end of one terminating resistor RT1 to constantly input a fixed high level (“1” level) signal, and the other end of the other terminating resistor RT2. Ground.

Here, the core wire 1 in the coaxial cable 10
The voltage VT between the terminating resistors RT1 and RT2 is applied to the other end 10b of 1. This voltage VT is a value determined by the ratio of the resistance values of the terminating resistors RT1 and RT2, and more specifically, the voltage of the signal input from the DC / DC converter 40 to one end of the terminating resistor RT1 is V
Assuming DD, the voltage VT = VDD * RT2 / (RT1 +
RT2).

That is, the voltage VT is at a level lower than the high level (“1” level) voltage VDD, and the core wire 11 of the coaxial cable 10 is maintained at the level of the voltage VT. Therefore, the input signal from the clock signal input terminal C to the flip-flop circuit 30 becomes the level of the voltage VT. That is, before applying the static electricity noise to the outer cover 15 of the coaxial cable 10, in the first embodiment, the core wire 11 of the coaxial cable 10 is applied.
Is 0V, whereas in the second embodiment, the core wire 11 of the coaxial cable 10 is larger than 0V, and
The level is lower than the high level (“1” level).

Therefore, in this state, the flip-flop circuit 30 recognizes that the input signal from the clock signal input terminal C is low level (“0” level), and the level of the output signal from the signal output terminal Q is , Low level (“0”
Level) remains.

In such a state, when the electrostatic noise generator 20 is moved along the coaxial cable 10 from one end 10a to the other end 10b and electrostatic noise is applied to the outer sheath 15 of the coaxial cable 10, As in the first embodiment, when the electrostatic noise generator 20 reaches a location where the aluminum shield 14 of the coaxial cable 10 is damaged, such as scratched or broken, the LED lights up and the buzzer sounds. Therefore, it becomes clear which part of the aluminum shield 14 in the coaxial cable 10 is damaged.

By the way, in the first embodiment, since the aluminum shield 14 in the coaxial cable 10 is not damaged (damaged or broken) is small (the influence of electrostatic noise is small), the core wire of the coaxial cable 10 is applied by the application of electrostatic noise. It is conceivable that the level of the signal generated at 11 does not reach the signal detection level of the flip-flop circuit 30 or higher and the damage cannot be detected. Even in this case,
In the second embodiment, such damage can be accurately detected.

FIG. 4 shows a case where electrostatic noise is applied to the outer cover 15 of the coaxial cable 10 when the aluminum shield 14 of the coaxial cable 10 is not damaged such as scratches or breaks. 4 is a conceptual diagram showing an input signal input from a clock signal input terminal C of the flip-flop circuit 30 and an output signal output from a signal output terminal Q of the flip-flop circuit 30. Note that FIG. 4A shows the case in the first embodiment,
FIG. 4B shows a case in the second embodiment.

In the case of the first embodiment, since the aluminum shield 14 in the coaxial cable 10 is less damaged such as scratches or breaks, as shown in FIG. Since the level of the signal generated at the signal level does not exceed the signal detection level of the flip-flop circuit 30,
Recognizes that the input signal from the clock signal input terminal C is low level (“0” level), and the level of the output signal from the signal output terminal Q is low level (“0” level).
Will remain.

On the other hand, in the case of the second embodiment, the core wire 11 of the coaxial cable 10 is at a level (VT) higher than 0 V and lower than the high level (“1” level), so that Aluminum shield 14
Even if the level of the signal generated in the core wire 11 of the coaxial cable 10 is small, the damage of FIG.
As shown in (B), the flip-flop circuit 30 recognizes that the input signal from the clock signal input terminal C is at a high level (“1” level), and as a result, outputs the output signal from the signal output terminal Q. The level is high level (“1”
It is possible to accurately detect damage such as scratches or breaks of the aluminum shield 14 in the coaxial cable 10 by changing the level.

As described above, according to the second embodiment, in addition to the effects of the first embodiment, the coaxial cable 1
Even when damage such as scratches or breakage of the aluminum shield 14 at 0 is small, such damage can be accurately detected.

Further, by appropriately selecting the resistance values of the termination resistors RT1 and RT2, it is possible to easily set a desired signal detection sensitivity.

In the first and second embodiments, the aluminum shield has been described as an example of the metal shield of the coaxial cable, but the present invention is not limited to this, and other conductors such as a copper shield may be used. The present invention is also applicable to the applied coaxial cable.

In the first and second embodiments, the so-called thin core coaxial cable inspection method has been described as an example, but it is needless to say that the present invention can be applied to coaxial cables other than so-called thin core cables.

[0067]

As described above, according to the present invention,
Since it is configured to detect a signal above a certain level generated in the core wire by applying electrostatic noise to the outer sheath of the coaxial cable, it is a non-destructive, inexpensive and simple method for detecting the presence or absence of damage to the metal shield of the coaxial cable. Can be inspected, and the presence or absence of the damage can be quantitatively determined.

[Brief description of drawings]

FIG. 1 is a diagram showing a schematic configuration of a coaxial cable inspection device for carrying out a coaxial cable inspection method according to a first embodiment.

FIG. 2 shows an input signal input from a clock signal input terminal C and an output signal output from a signal output terminal Q of a flip-flop circuit 30 when electrostatic noise is applied to the outer jacket 15 of the coaxial cable 10. It is a conceptual diagram.

FIG. 3 is a diagram showing a schematic configuration of a coaxial cable inspection apparatus for carrying out a coaxial cable inspection method according to a second embodiment.

FIG. 4 is an aluminum shield 14 of the coaxial cable 10.
When the damage such as scratches or breakage is small, the coaxial cable 1
When electrostatic noise is applied to the outer skin 15 of 0,
It is a comparison between the first embodiment and the second embodiment, showing an input signal input from the clock signal input terminal C of the flip-flop circuit 30 and an output signal output from the signal output terminal Q. It is a conceptual diagram.

FIG. 5 is a diagram showing an example of a cross-sectional structure of a general thin core coaxial cable.

FIG. 6 is a diagram showing a state where the aluminum shield 14 of the coaxial cable 10 is damaged.

[Explanation of symbols]

1, 2 coaxial cable inspection device 10 coaxial cable 11 core wire 12 drain wire 13 Insulator 14 Aluminum shield 15 outer skin 20 Electrostatic noise generator 30 flip-flop circuit 40 DC / DC converter RT, RT1, RT2 Terminator D Data signal input terminal C clock signal input terminal R Reset signal input terminal Q signal output terminal

Claims (14)

[Claims] 1. A method of inspecting a coaxial cable for non-destructively inspecting a metal shield in a coaxial cable for damage, comprising a step of applying electrostatic noise to an outer cover of the coaxial cable, and a core wire of the coaxial cable by the application. And a step of detecting a signal of a predetermined level or higher, which is generated in 1. 2. The method for inspecting a coaxial cable according to claim 1, wherein a signal detecting means for detecting a signal of the predetermined level or higher is connected to one end of a core wire of the coaxial cable. Inspection method. 3. The method for inspecting a coaxial cable according to claim 2, wherein the signal detecting means is a flip-flop circuit having at least a data signal input terminal, a clock signal input terminal, and a signal output terminal. A method of inspecting a coaxial cable, wherein a high-level signal is constantly input from a signal input terminal, and the clock signal input terminal is connected to one end of a core wire of the coaxial cable. 4. The method of inspecting a coaxial cable according to claim 2, wherein the other end of the core wire of the coaxial cable is grounded via a resistor. 5. The method of inspecting a coaxial cable according to claim 4, wherein the resistance value of the resistor is made equal to the characteristic impedance value of the coaxial cable. 6. The coaxial cable inspection method according to claim 2, wherein a signal having a level lower than the predetermined level is always input from the other end of the core wire of the coaxial cable. Inspection method. 7. The method for inspecting a coaxial cable according to claim 2, wherein two resistors are connected in parallel to the other end of the core wire of the coaxial cable, and one end of one of the resistors is always at a high level. Signal is input and one end of the other resistor is grounded. 8. A coaxial cable inspection apparatus for nondestructively inspecting a coaxial cable for damage to a metal shield, comprising: noise applying means for applying electrostatic noise to the outer sheath of the coaxial cable; And a signal detecting means for detecting a signal of a predetermined level or more generated in the core wire in the coaxial cable inspection device. 9. The coaxial cable inspection device according to claim 8, wherein the signal detecting means is connected to one end of a core wire of the coaxial cable. 10. The coaxial cable inspection device according to claim 9, wherein the signal detection unit is a flip-flop circuit having at least a data signal input terminal, a clock signal input terminal, and a signal output terminal, A high-level signal is always input to a signal input terminal, and one end of a core wire of the coaxial cable is connected to the clock signal input terminal. 11. The coaxial cable inspection device according to claim 9, further comprising a resistor connected to the other end of the core wire of the coaxial cable, wherein one end of the resistor is grounded. Coaxial cable inspection device. 12. The coaxial cable inspection device according to claim 11, wherein the resistance value of the resistor is equal to the characteristic impedance value of the coaxial cable. 13. The coaxial cable inspection device according to claim 9, further comprising a signal input unit for constantly inputting a signal of a level smaller than the predetermined level from the other end of the core wire of the coaxial cable. A coaxial cable inspection device characterized in that 14. The coaxial cable inspection device according to claim 9, further comprising: two resistors connected in parallel to the other end of the core wire of the coaxial cable, wherein one end of one of the resistors is always connected, A high-level signal is input, and one end of the other resistor is grounded. A coaxial cable inspection device.