Method for testing multicore cable, method for manufacturing multicore cable assembly, and multicore cable test device

A method for testing a multicore cable that includes a single common shield covering plural insulated wires. The testing method includes inputting a test signal, by capacitive coupling, to an end portion of the insulated wire under test among end portions of the insulated wires exposed at one end of the multicore cable, and measuring voltages of output signals output by capacitive coupling respectively from end portions of the insulated wires exposed at the other end of the multicore cable, and identifying the other end portion of the insulated wire under test based on the measured voltages. The voltages of output signals are measured in a state that an output variation reduction capacitive element is connected in series with a coupling capacitance generated by the capacitive coupling.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is based on Japanese patent application No. 2018-024769 filed on Feb. 15, 2018, the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a method for testing a multicore cable, a method for manufacturing a multicore cable assembly, and a multicore cable test device.

2. Description of the Related Art

A multicore cable is known in which multiple insulated wires each having an insulation around a conductor are covered with a single jacket. Also, a multicore cable used for, e.g., medical probe cables is known which has several tens to several hundreds of insulated wires (coaxial wires etc.).

For the multicore cable having the numerous insulated wires, it is difficult to use a color code so that every insulated wire has a different color insulation. In addition, in case that the insulated wires are twisted together inside the multicore cable, each insulated wire is not located at the same position. Therefore, when connecting a multicore cable having numerous insulated wires to connectors or circuit boards, a test method is required to somehow identify a correspondence relation between one end portion and the other end portion of each of the insulated wires exposed from both ends of the multicore cable.

As a test method to identify the correspondence relation between one end portion and the other end portion of insulated wires contained in the multicore cable, for example, there is a method in which a test signal is input to one end portion of a given insulated wire and voltage output from the other end portion is measured.

To test the multicore cable having the numerous insulated wires, when a conductor of each insulated wire is exposed at an end portion and an electrode for supplying a test signal is directly brought into contact with the conductor, it is necessary to bring the electrode into contact with the conductor of every insulated wire to identify the correspondence relation and it thus takes very long time for the test. Therefore, the test to identify the correspondence relation between one end portion and the other end portion of insulated wires contained in a multicore cable having numerous insulated wires is desired to be conducted by a method in which an electrode is placed on an insulation and an AC test signal is input to a conductor by capacitive coupling without contact (see, e.g., JP 2004/251771 A).

SUMMARY OF THE INVENTION

A variation in coupling capacitance at a capacitive coupling portion may occur if the electrode is misaligned with respect to the insulated wire, if the outer covering of the insulated wire has a thickness abnormality in which the thickness of the outer cover is partially different, or if minute foreign matter such as dust is sandwiched between the electrode and the insulated wire. When the coupling capacitance varies, output voltage during test varies, which may cause misdetection.

It is an object of the invention to provide a method for testing a multicore cable that reduces a variation in output voltage caused by variation in coupling capacitance so as to improve a detection accuracy, as well as a method for manufacturing a multicore cable assembly and a multicore cable test device.

According to an embodiment of the invention, a method for testing a multicore cable that comprises a single common shield covering a plurality of insulated wires comprises:

inputting a test signal, by capacitive coupling, to an end portion of the insulated wire under test among end portions of the insulated wires exposed at one end of the multicore cable; and

measuring voltages of output signals output by capacitive coupling respectively from end portions of the insulated wires exposed at the other end of the multicore cable, and identifying the other end portion of the insulated wire under test based on the measured voltages,

wherein the voltages of output signals are measured in a state that an output variation reduction capacitive element is connected in series with a coupling capacitance generated by the capacitive coupling.

According to another embodiment of the invention, a method for manufacturing a multicore cable assembly that comprises a multicore cable comprising a single common shield covering a plurality of insulated wires and connectors or circuit boards provided at both ends of the multicore cable, the manufacturing method comprising:

stripping the insulated wires to expose conductors at end portions; and

connecting the exposed conductors to terminals of the connectors or electrode patterns of the circuit board,

wherein the arranging wire comprises identifying a corresponding end portion by identifying a correspondence relation between one end portion and the other end portion of the insulated wires exposed from both ends of the multicore cable and arranging end portions of the insulated wires exposed from the both ends of the multicore cable in desired order, the identifying a corresponding end portion comprises inputting a test signal, by capacitive coupling, to an end portion of the insulated wire under test among end portions of the insulated wires exposed at one end of the multicore cable, measuring voltages of output signals output by capacitive coupling respectively from end portions of the insulated wires exposed at the other end of the multicore cable, and identifying the other end portion of the insulated wire under test based on the measured voltages, and the voltages of output signals are measured in a state that an output variation reduction capacitive element is connected in series with a coupling capacitance generated by the capacitive coupling.

According to another embodiment of the invention, a multicore cable test device for testing a multicore cable comprising a single common shield covering a plurality of insulated wires to identify a correspondence relation between one end portion and the other end portion of the insulated wires exposed from both ends of the multicore cable comprises:

a test signal input means that inputs a test signal, by capacitive coupling, to an end portion of the insulated wire under test among end portions of the insulated wires exposed at one end of the multicore cable;

a corresponding-end identifying unit that measures voltages of output signals output by capacitive coupling respectively from end portions of the insulated wires exposed at the other end of the multicore cable, and identifies the other end portion of the insulated wire under test based on the measured voltages; and

an output variation reduction capacitive element that is connected in series with a coupling capacitance generated by the capacitive coupling.

Effects of the Invention

According to an embodiment of the invention, a method for testing a multicore cable can be provided that reduces a variation in output voltage caused by variation in coupling capacitance so as to improve a detection accuracy, as well as a method for manufacturing a multicore cable assembly and a multicore cable test device.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiment

An embodiment of the invention will be described below in conjunction with the appended drawings.

General Configuration of Multicore Cable Test Device1

FIG. 1is a schematic diagram illustrating a multicore cable test device which is used in a method for testing a multicore cable in the present embodiment.FIG. 2Ais a schematic cross-sectional view showing a multicore cable taken perpendicular to a longitudinal direction andFIG. 2Bis a cross sectional view showing an insulated wire taken perpendicular to the longitudinal direction.

A multicore cable test device1is used to identify a correspondence relation between one end portion and the other end portion of each insulated wire3exposed at both ends of a multicore cable2. After identifying the correspondence relation between one end portion and the other end portion of the insulated wires3of the multicore cable2, the insulated wires3at both ends of the multicore cable2are respectively connected to connectors or circuit boards (internal boards in sensor portions, etc.) (not shown in the drawings) according to the identified correspondence relation, and a multicore cable assembly is thereby obtained.

As shown inFIGS. 2A and 2B, the insulated wire3used in the multicore cable2is a coaxial wire30in which an insulation32, an outer conductor33and an outer covering34are sequentially provided around a center conductor31. However, the insulated wire3is not limited thereto and may not have the insulation32and the outer conductor33. The outer diameter of the coaxial wire30is, e.g., 0.2 mm to 0.5 mm. The multicore cable2is formed by sequentially providing a braided common shield21and a jacket22around multiple bundled coaxial wires30. The number of insulated wires3in the multicore cable2is not specifically limited, and the invention is applicable to the multicore cable2having not less than three insulated wires3. In the present embodiment, the number of insulated wires3contained in one multicore cable2is, e.g., about ten to three hundred.

Back toFIG. 1, the multicore cable test device1is provided with a test signal input means4and an output-side processing circuit6. The test signal input means4inputs at least an AC test signal, by capacitive coupling, to an end portion of the insulated wire3under test among end portions of the insulated wires3exposed at one end of the multicore cable2, and has a voltage source41for generating the test signal and electrodes442each brought into contact with an outer circumferential surface of the insulated wire3so that the test signal is input to the insulated wire3by capacitive coupling. The reference numeral41ainFIG. 1denotes an internal resistor of the voltage source41.

In the present embodiment, since capacitive coupling is used to input the test signal to the insulated wires3, an AC signal is used as the test signal. The frequency of the test signal needs to be smaller than the resonant frequency of the multicore cable2, and can be appropriately determined depending on the structure, etc., of the multicore cable2. In more detail, the frequency of the test signal is, e.g., not more than 10 MHz. In the present embodiment, the test signal V+ at 2.5 MHz is used.

As shown inFIGS. 3A and 3B, the insulated wires3(the coaxial wires30in this example) exposed and aligned at one end of the multicore cable2are fixed to a test bench45. The test bench45integrally has a base451and a pair of locking walls452arranged on the base451so as to face each other. Plural locking grooves452afor locking the insulated wires3are formed at equal intervals on the both locking walls452. The insulated wires3are respectively fitted and fixed to the locking grooves452aand are thereby arranged in a row on the base451at predetermined intervals. However, the structure to fix the insulated wires3to the test bench45is not limited thereto. For example, the insulated wires3may be placed on an adhesive tape such as double-sided tape stuck to the base451so that the insulated wires3are adhered and fixed to the test bench45. In addition, although the insulated wires3are arranged in a row at equal intervals in one direction (a direction perpendicular to a longitudinal direction of the insulated wire3), arrangement of the insulated wires3may be appropriately changed.

The electrodes442are provided on an electrode substrate44. The electrode substrate44has a dielectric substrate441and the electrodes442constructed from a wiring pattern formed on the dielectric substrate441. The same number of electrodes442as the insulated wires3(or more than the insulated wires3) are formed in alignment on the dielectric substrate441at the same intervals as the insulated wires3fixed to the locking grooves452a. In addition, each electrode442is electrically connected to the voltage source41and receives input of the test signal.

In the present embodiment, the electrode substrate44is pressed, with a surface having the electrodes442facing downward, against the insulated wires3between the two locking walls452. Thus, the electrodes442and the insulated wires3are sandwiched between the dielectric substrate441and the base451. When the test signal is input to a given electrode442in this state, the test signal is input to the insulated wire3corresponding to the given electrode442by capacitive coupling. In the present embodiment in which the coaxial wire30is used as the insulated wire3, the test signal is input to the outer conductor33of the insulated wire3.

Back toFIG. 1, the output-side processing circuit6has a test bench (not shown) having the same structure as the test bench45and provided at an end of the multicore cable2, and is configured that output signals from the insulated wires3(signals transmitted through the outer conductors33) are output by capacitive coupling by pressing electrodes611of an electrode substrate (not shown) respectively against the insulated wires3. Since the test bench and the electrode substrate of the output-side processing circuit6have the same configurations as the test bench45and the electrode substrate44, the explanation thereof is omitted.

The output-side processing circuit6has a load resistor66. Based on voltage applied to the load resistor66(a potential difference between both ends of the load resistor66), the other end portion of the insulated wire3under test is identified by a corresponding-end identifying unit81(described later, seeFIG. 7). The specific configuration, etc., of the multicore cable test device1including the test signal input means4and the output-side processing circuit6will be described later.

Output Variation Reduction Capacitive Element9

The multicore cable test device1in the present embodiment is provided with output variation reduction capacitive elements9each of which is connected in series with coupling capacitance generated by capacitive coupling. The reason why the output variation reduction capacitive elements9are provided will be described below.

Firstly, the case of not providing the output variation reduction capacitive element9will be examined. The equivalent circuit of the multicore cable test device not provided with the output variation reduction capacitive elements9in Comparative Example is expressed as shown inFIG. 4A, where C is coupling capacitance as a sum of capacitances on the input and output sides. InFIG. 4A, resistance of the internal resistor41aof the voltage source41and resistance of the load resistor66are denoted by R. An input impedance Zinwhen viewing from the voltage source41side is expressed by the formula Zin=2R+1/(jωC). When R<<1/ωC, the input impedance Zinis expressed by the formula Zin≈1/(ωC)×e−jπ.

When voltage of the voltage source41is v=vo×ejωt, output voltage v1, which is voltage applied to the load resistor66, is expressed by the formula:

v1=R/Zi⁢⁢n×v≈vo⁢⁢ω⁢RC⁢⁢ej⁡(ω⁢⁢t+π)
Here, let ΔC denotes variation in coupling capacitance and the coupling capacitance C is expresses as Co+ΔC. In this case, a ratio of output voltage with variation in coupling capacitance, v1(ΔC), to output voltage without variation in coupling capacitance (when ΔC=0), v1(0), i.e., variation in normalized output voltage P(ΔC) is expressed by the following formula (1):

The equivalent circuit of Comparative Example shown inFIG. 4Awas actually made for evaluation, and change in gain (|S21|) with respect to a frequency of detection signal was measured when the coupling capacitance C was 1 pF and 2 pF (Co=1 pF, ΔC=1 pF). The measurement result is shown inFIG. 4B. In Comparative Example, change in the gain upon change in the value of the coupling capacitance C is large and variation in output voltage is large, as shown inFIG. 4B.

Next, Example of the invention provided with the output variation reduction capacitive element9will be examined. The equivalent circuit in Example is expressed as shown inFIG. 5A. When R<<1/ωC+1/ωCα, output voltage v2in Example is expressed by:

v2=R/Zi⁢⁢n×v≈vo⁢⁢ω⁢R⁢{(C·C⁢⁢α)/(C+C⁢⁢α))⁢ej⁡(ω⁢⁢t+π)
in the same manner as Comparative Example. Thus, a ratio of output voltage with variation in coupling capacitance, v2(ΔC), to output voltage without variation in coupling capacitance (when ΔC=0), v2(0), i.e., variation of normalized output voltage Q(ΔC) is expressed by the following formula (2):

Based on the formulas (1) and (2), a difference D in the amount of change with respect to ΔC between the variation in output voltage P(ΔC) in Comparative Example and the variation in output voltage Q(ΔC) in Example is expressed by the formula (3) below. D>0 based on the formula (3), which shows that variation in output voltage caused by variation in coupling capacitance can be reduced by inserting the output variation reduction capacitive element9.

The equivalent circuit of Example shown inFIG. 5Awas actually made for evaluation, and change in gain (|S21|) with respect to a frequency of detection signal was measured when the coupling capacitance C was 1 pF and 2 pF (i.e., Co=1 pF, ΔC=1 pF). The gain (|S21|) and the output voltage bear a proportional relationship. Thus, variation in the gain (|S21|) and variation in the output voltage also bear a proportional relationship. In addition, the normalized variation in the gain (|S21|) is equal to the normalized variation in the output voltage. The measurement result is shown inFIG. 5B. In Example, change in the gain upon change in the value of the coupling capacitance C is smaller than in Comparative Example and variation in output voltage is small, as understood by comparison ofFIGS. 5B and 4B.

FIG. 6shows a calculation result of variation in gain (normalized variation in gain) obtained by dividing a difference between the gain with the coupling capacitance C of 1 pF and the gain with the coupling capacitance C of 2 pF by an average of the both gains. As shown inFIG. 6, while variation in the gain in Comparative Example is about 0.70, variation in the gain in Example is about 0.28 and is very small (reduced to about 40% of variation in the gain in Comparative Example).

As such, it is possible to reduce variation in gain (in output voltage) by providing the output variation reduction capacitive element9. Output voltage may decrease since a capacitive element with a relatively small capacitance is connected as the output variation reduction capacitive element9. Therefore, it is desirable to provide an amplifier circuit63for amplifying a decreased output signal (seeFIG. 1).

Specific Configuration of the Multicore Cable Test Device1

FIG. 7is a schematic configuration diagram illustrating an example of a specific configuration of the multicore cable test device1. As shown inFIG. 7, the multicore cable test device1is provided with the test signal input means4, a phase-inverted test signal input means5, the output-side processing circuit6, a reference signal generating circuit7, and the arithmetic device8having the corresponding-end identifying unit81.

The test signal input means4has the voltage source41(described previously) for generating the test signal V+, the electrodes442each brought into contact with an outer circumferential surface of the insulated wire3so that the test signal is input to the insulated wire3by capacitive coupling, a first amplifier42for amplifying the test signal V+, a first switching device43for switching the insulated wire3to which the test signal V+ amplified by the first amplifier42is input, and the electrode substrate44(described previously) mounting the plural electrodes442which are respectively electrically connected to outputs of the first switching device43. The electrodes442are respectively electrically connected to the outputs of the first switching device43and the test signal V+ is applied to the electrode442selected by the first switching device43.

The phase-inverted test signal input means5has a first phase shifter51for shifting the phase of the test signal V+ branched from the voltage source41by 180 degrees to generate a phase-inverted test signal V−, a second amplifier52for amplifying the phase-inverted test signal V− from the first phase shifter51, and a second switching device53for switching the insulated wire3to which the phase-inverted test signal V− amplified by the second amplifier52is input. Outputs of the second switching device53are respectively electrically connected to the electrodes442of the electrode substrate44.

In the present embodiment, the phase-inverted test signal V− is generated by adjusting the phase of the voltage source41of the test signal input means4. However, it is not limited thereto and a voltage source for generating the phase-inverted test signal V− may be separately provided. In this case, voltage (amplitude) of the phase-inverted test signal V− is substantially the same as that of the test signal V+. In addition, although the electrode substrate44of the test signal input means4is also used to input the phase-inverted test signal V− to the insulated wires3in the present embodiment, it is not limited thereto. An electrode substrate for inputting the phase-inverted test signal V− may be separately provided.

The output-side processing circuit6has the test bench (not shown) having the same structure as the test bench45and provided at an end of the multicore cable2, and is configured that output signals from the insulated wires3(signals transmitted through the outer conductors33) are output by capacitive coupling by pressing electrodes611of an electrode substrate61respectively against the insulated wires3.

The output-side processing circuit6also has a third switching device62electrically connected to each electrode611of the electrode substrate61to switch the insulated wire3from which an output signal is output, the third amplifier63for amplifying the output signal from the third switching device62, a multiplier64which produces a detection signal by multiplying the output signal amplified in the third amplifier63by a reference signal having the same phase as the test signal V+, and a low-pass filter65which removes high-frequency components in the detection signal sent from the multiplier64.

When signals having the same phase and the same frequency are multiplied with each other by the multiplier64, a DC component and a component with a frequency double the original frequency are generated. The low-pass filter65removes the component with a doubled frequency and outputs only the DC component as the detection signal to the arithmetic device8.

The reference signal generating circuit7has a second phase shifter71which produces a reference signal by adjusting the phase of the test signal V+ branched from the voltage source41, and a fourth amplifier72which amplifies the reference signal from the second phase shifter71and outputs it to the multiplier64. The phase shift amount by the second phase shifter71is appropriately adjusted by taking into consideration capacitive coupling and phase shifting during transmission through the multicore cable2, so that the test signal V+ and the reference signal have the same phase in the multiplier64.

The arithmetic device8has the corresponding-end identifying unit81which measures voltages of the output signals respectively output from end portions of the insulated wires3exposed at the other end of the multicore cable2and identifies the other end portion of the insulated wire3under test based on the measured voltages of the output signals. In the present embodiment, the corresponding-end identifying unit81is configured to identify the other end portion of the insulated wire3under test based on voltage of the detection signal output from the low-pass filter65. The corresponding-end identifying unit81is realized by appropriately combining a CPU, a memory such as RAM or ROM, a storage device such as hard disc, a software, and an interface, etc.

The corresponding-end identifying unit81has a switch controlling portion811which controls switching operations of the first to third switching devices43,53and62, and a determination portion812which determines the correspondence relation between one end portion and the other end portion of the insulated wire3. In the present embodiment, the determination portion812controls the first switching device43through the switch controlling portion811to input the test signal V+ to an end portion of the insulated wire3under test at one end of the multicore cable2, and also controls the second switching device53to input the phase-inverted test signal V− to an end portion of a given insulated wire3. After that, the determination portion812controls the third switching device62and sequentially measures voltages of the detection signals from all insulated wires3at the other end of the multicore cable2.

The determination portion812identifies that the end portion with the detection signal having the largest voltage, among end portions of the insulated wires3exposed at the other end of the multicore cable2, is the other end portion of the insulated wire3under test, and stores the correspondence relation in a storage unit82. To express the correspondence relation between one end portion and the other end portion of the insulated wire3, e.g., the numbers sequentially assigned to end portions of the insulated wires3arrange in a row at one end of the multicore cable2are associated with the numbers sequentially assigned to end portions of the insulated wires3arrange in a row at the other end of the multicore cable2. The determination portion812sequentially changes the insulated wire3to be tested, identifies the correspondence relation between one end portion and the other end portion of all insulated wires3, and stores the identified relation in the storage unit82.

In the present embodiment, the corresponding-end identifying unit81also has a verifying portion813which determines whether or not an end portion of any of the insulated wires3exposed at one end of the multicore cable2corresponds to duplicate other end portions. The verifying portion813checks if any of the numbers assigned to the other end portions of the insulated wires3is duplicated in the correspondence relation which is determined by the determination portion812and is stored in the storage unit82, thereby determining whether or not there is a duplication. This is performed because depending on the positional relation between the insulated wires3receiving an input of the test signal V+ and the phase-inverted test signal V−, the common shield21and the insulated wire3from which the detection signal is acquired, crosstalk of the test signal V+ and crosstalk of the phase-inverted test signal V− may become imbalanced, resulting in misdetection. When it is determined that there is a duplication, the verifying portion813changes the insulated wire3to which the phase-inverted test signal V− is input, and re-identifies the correspondence relation between one end portion and the other end portion of at least the insulated wire3under test having duplicate end portions at the other end.

In the present embodiment, determination of the correspondence relation between one end portion and the other end portion is also performed on the insulated wire3receiving an input of the phase-inverted test signal V− in the same manner as the other insulated wires3due to the circuit configuration, and misdetection is highly likely to occur in at least the insulated wire3receiving an input of the phase-inverted test signal V−. Therefore, in the present embodiment, the verifying portion813determines, at least once, that there is a duplication, and identifies the correspondence relation between one end portion and the other end portion of the insulated wire3having a duplication.

In the multicore cable test device1, the test signal V+ and the phase-inverted test signal V− are both input so that the two test signals V+ and V− cause crosstalk and cancel each other out in the other insulated wires3to which the test signals V+ and V− are not input. As a result, it is possible to reduce the effect of crosstalk and to accurately identify the correspondence relation between one end portion and the other end portion of the insulated wires3. The invention is particularly suitably applicable to the multicore cable2in which multiple insulated wires3are densely arranged and a coupling capacitance between the insulated wires3is large. In addition, use of the invention is highly effective in case that the multicore cable2has the common shield21since the coupling capacitance is larger than when not having the common shield21.

Where to Position the Output Variation Reduction Capacitive Element9

The output variation reduction capacitive elements9can be provided either on the test signal input side or the output side. However, in view of electrical characteristics, the output variation reduction capacitive elements9are more desirably provided on the test signal output side, i.e., on the output-side processing circuit6. Alternatively, the output variation reduction capacitive elements9may be provided on both the test signal input side and the output side.

In the configuration of the present embodiment, the same number of output variation reduction capacitive elements9as the electrodes611are provided on the electrode substrate61and the electrodes611are respectively electrically connected to inputs of the third switching device62via the variation reduction capacitive elements9. In other words, in the present embodiment, the variation reduction capacitive elements9are mounted on the electrode substrate61and connected in series to the electrodes611. This allows good electrical characteristics to be maintained even when, e.g., work of pressing the electrode substrate61against the insulated wires3arranged on the test bench is automated and the electrode substrate61is connected to the output-side processing circuit6in the subsequent stage by an insulated wire such as coaxial wire or a cable.

However, it is not limited thereto. For example, a single output variation reduction capacitive element9may be provided between the third switching device62and the third amplifier63. In this case, since there is only one output variation reduction capacitive element9, the cost is lower and the circuit configuration is simpler. However, when the electrode substrate61is connected to the output-side processing circuit6in the subsequent stage by an insulated wire such as coaxial wire or a cable as mentioned above, a capacitive element with a relatively small capacitance is provided immediately after the insulated wire or cable and it is difficult to obtain impedance matching with the insulated wire or cable. This may result in that output decreases due to impedance mismatching and electrical characteristics thereby degrade. Therefore, in such a case, it is desirable to provide the output variation reduction capacitive element9on the electrode substrate61.

When the output variation reduction capacitive elements9are provided on the test signal input side, the configuration may be such that the same number of output variation reduction capacitive elements9as the electrodes442are provided on the electrode substrate44and the electrodes442are respectively electrically connected to inputs of the switching devices43and53via the output variation reduction capacitive elements9. Alternatively, when the output variation reduction capacitive elements9are provided on the test signal input side, the output variation reduction capacitive elements9may be provided respectively between the first amplifier42and the first switching device43and between the second amplifier52and the second switching device53.

Method for Manufacturing the Multicore Cable Assembly

FIG. 8Ais a flowchart showing a method for manufacturing a multicore cable assembly. As shown inFIG. 8A, the method for manufacturing a multicore cable assembly in the present embodiment includes a wire arranging step as Step S1, a stripping step as Step S2and a connecting step as Step S3which are performed sequentially.

In the wire arranging step as Step S1, a corresponding-end identifying step to identify a correspondence relation between one end portion and the other end portion of the insulated wires3exposed from both ends of the multicore cable2is performed in Step S11, and an orderly arranging step to arrange the end portions of the insulated wires3exposed from both ends of the multicore cable2in desired order is then performed in Step S12. In the stripping step as Step S2, the exposed length of each insulated wire3is adjusted (by cutting and removing an excess length), and also the conductor (the center conductor31and the outer conductor33of the coaxial wire30in this example) is exposed at ends of each insulated wire3. In the connecting step as Step S3, the exposed conductors are connected to terminals of connectors or electrode patterns of circuit boards (not shown), etc., by soldering, etc. Through these steps, a multicore cable assembly having connectors or circuit boards at both ends of the multicore cable2is obtained.

Method for Testing the Multicore Cable

FIG. 8Bis a flowchart showing a process of the corresponding-end identifying step as Step S11. As shown inFIG. 8B, in the corresponding-end identifying step as Step S11, i.e., in the method for testing a multicore cable in the present embodiment, firstly, the insulated wires3are exposed at both ends of the multicore cable2by removing a predetermined length of the jacket22and the common shield21in Step S111. After that, in Step S112, the exposed insulated wires3are respectively fitted to the locking grooves452aof the test bench45at both ends of the multicore cable2, and the electrode substrates44and61are pressed against the insulated wires3which are fixed to the test bench45. Then, a test is conducted to identify a correspondence relation between one end portion and the other end portion of each insulated wire3in Step S113. The method for testing a multicore cable in the present embodiment is performed by using the multicore cable test device1shown inFIG. 7. That is, voltages of output signals are measured in a state that the output variation reduction capacitive elements9are connected in series with coupling capacitances Cc generated by capacitive coupling.

In Step S113, firstly, the test signal V+ is input, by capacitive coupling and through the electrode substrate44(the electrode442), to an end portion of the insulated wire3under test among end portions of the insulated wires3exposed at one end of the multicore cable, and also the phase-inverted test signal V− is input, by capacitive coupling and through the electrode substrate44(the electrode442), to an end portion of the insulated wire3other than the end portion of the insulated wire3under test. After that, the determination portion812controls the third switching device62through the switch controlling portion811, measures voltage of an output signal (in this example, a detection signal produced by multiplying the output signal by a reference signal) output from an end portion of each insulated wire3exposed at the other end of the multicore cable2, and determines that the other end portion of the insulated wire3with the largest output voltage is the other end portion of the insulated wire3under test. By performing such determination while changing the insulated wire3receiving an input of the test signal V+ by the first switching device43, the correspondence relation between one end portion and the other end portion of all insulated wires is identified. Then, the verifying portion813determines whether or not an end portion of any of the insulated wires3exposed at one end of the multicore cable2corresponds to duplicate other end portions, and when duplication is determined, the insulated wire3determined as having a duplication is retested.

Functions and Effects of the Embodiment

As described above, in the method for testing a multicore cable in the present embodiment, voltages of output signals are measured in a state that the output variation reduction capacitive elements9are connected in series with coupling capacitances generated by capacitive coupling. As a result, even when variation in coupling capacitance occurs due to capacitive coupling, it is possible to reduce variation in output voltage and thereby suppress a decrease in detection accuracy. In other words, according to the present embodiment, it is possible to provide a multicore cable testing method of which detection accuracy is improved by reducing variation in output voltage caused by variation in coupling capacitance.

In addition, since variation in output voltage can be reduced, it is possible to increase allowable variation in coupling capacitance. Therefore, it is possible to accurately identify the correspondence relation between one end portion and the other end portion of the insulated wires3even when, e.g., the electrode442or611is slightly misaligned with respect to the insulated wire3, the outer covering has a thickness abnormality, or minute foreign matter such as dust is sandwiched between the electrode442or611and the insulated wire3.

When, e.g., the insulated wire3is very thin (e.g., a diameter of not more than 1 mm), displacement in the event of misalignment is very small and it is necessary to use an expensive alignment device, etc., for accurate positioning. However, in the present embodiment, such expensive alignment device, etc., is not required, hence, low cost. Meanwhile, when minute foreign matter such as dust is sandwiched between the electrode442or611and the insulated wire3, it is necessary to remove the foreign matter in the conventional technique and it thus takes time for detection. However, in the present embodiment, it is not necessary to remove the foreign matter as log as it is very small and it is thus possible to reduce time for identifying the correspondence relation.

Modification

Although the effect of crosstalk is reduced by inputting two signals, the test signal and the phase-inverted test signal, in the embodiment, it is not limited thereto. It is possible to configure to input only the test signal. In this case, the phase-inverted test signal input means5is omitted and the common shield21of the multicore cable2is grounded, as is a multicore cable test device1ashown inFIG. 9. Since crosstalk is divided by grounding the common shield21(by keeping the common shield21at the same potential as a measurement system ground), output voltage from end portions of the insulated wires3not receiving input of the test signal V is reduced to smaller than the output voltage from an end portion of the insulated wire3to which the test signal V is input, and the effect of crosstalk is thereby reduced.

SUMMARY OF THE EMBODIMENTS

Technical ideas understood from the embodiment will be described below citing the reference numerals, etc., used for the embodiment. However, each reference numeral, etc., described below is not intended to limit the constituent elements in the claims to the members, etc., specifically described in the embodiment.

[1] A method for testing a multicore cable (2) that comprises a single common shield (21) covering a plurality of insulated wires (3), the testing method comprising: inputting a test signal, by capacitive coupling, to an end portion of the insulated wire (3) under test among end portions of the insulated wires (3) exposed at one end of the multicore cable (2); and measuring voltages of output signals output by capacitive coupling respectively from end portions of the insulated wires (3) exposed at the other end of the multicore cable (2), and identifying the other end portion of the insulated wire (3) under test based on the measured voltages, wherein the voltages of output signals are measured in a state that an output variation reduction capacitive element (9) is connected in series with a coupling capacitance generated by the capacitive coupling.

[2] The method for testing a multicore cable defined by [1], wherein the output variation reduction capacitive element (9) is provided on an output-side processing circuit (6) that processes the output signals.

[3] The method for testing a multicore cable defined by [2], wherein the output-side processing circuit (6) comprises an electrode substrate (61) comprising a plurality of connection electrodes (611) that are capacitively coupled to other end portions of the insulated wires (3), and the output variation reduction capacitive element (9) is connected in series to the connection electrodes (611) mounted on the electrode substrate (61).

[4] The method for testing a multicore cable defined by [2] or [3], comprising: an amplifier circuit (63) that amplifies the output signals.

[5] A method for manufacturing a multicore cable assembly that comprises a multicore cable (2) comprising a single common shield (21) covering a plurality of insulated wires (3) and connectors or circuit boards provided at both ends of the multicore cable (2), the manufacturing method comprising: arranging wires; stripping the insulated wires (3) to expose conductors at end portions; and connecting the exposed conductors to terminals of the connectors or electrode patterns of the circuit board, wherein the arranging wire comprises identifying a corresponding end portion by identifying a correspondence relation between one end portion and the other end portion of the insulated wires (3) exposed from both ends of the multicore cable (2) and arranging end portions of the insulated wires (3) exposed from the both ends of the multicore cable (2) in desired order, the identifying a corresponding end portion comprises inputting a test signal, by capacitive coupling, to an end portion of the insulated wire (3) under test among end portions of the insulated wires (3) exposed at one end of the multicore cable (2), measuring voltages of output signals output by capacitive coupling respectively from end portions of the insulated wires (3) exposed at the other end of the multicore cable (2), and identifying the other end portion of the insulated wire (3) under test based on the measured voltages, and the voltages of output signals are measured in a state that an output variation reduction capacitive element (9) is connected in series with a coupling capacitance generated by the capacitive coupling.

[6] A multicore cable test device (1) for testing a multicore cable (2) comprising a single common shield (21) covering a plurality of insulated wires (3) to identify a correspondence relation between one end portion and the other end portion of the insulated wires (3) exposed from both ends of the multicore cable (2), the device comprising: a test signal input means (4) that inputs a test signal, by capacitive coupling, to an end portion of the insulated wire (3) under test among end portions of the insulated wires (3) exposed at one end of the multicore cable (2); a corresponding-end identifying unit (81) that measures voltages of output signals output by capacitive coupling respectively from end portions of the insulated wires (3) exposed at the other end of the multicore cable (2), and identifies the other end portion of the insulated wire (3) under test based on the measured voltages; and an output variation reduction capacitive element (9) that is connected in series with a coupling capacitance generated by the capacitive coupling.

Although the embodiment of the invention has been described, the invention according to claims is not to be limited to the embodiment. Further, please note that all combinations of the features described in the embodiment are not necessary to solve the problem of the invention. In addition, the invention can be appropriately modified and implemented without departing from the gist thereof.