JP2017181250A - Resistance value measuring system and resistance value measuring method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an accurate resistance value associated with the resistance value of core wires even if an apparatus is connected between the core wires.SOLUTION: A resistance value measuring unit 200 includes a first core wire, a second core wire, and a shield wire, and measures the value of the resistance between the other end of the first wire and the other end of the shield wire in a configuration in which one end of the first core wire, one end of the second core wire, and one end of the shield wire are connected to one another in one end of a measurement object 500 formed of serially connected cables and the other end of the first core wire and the other end of the second core wire are connected to each other in the other end of the measurement object 500. A display device 300 displays information based on the resistance value measured by the resistance value measuring unit 200.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a resistance value measuring system and a resistance value measuring method.

  Various techniques for detecting an abnormality in a cable that connects devices to each other are known. Cable abnormalities include disconnection and oxidation of the core wire contained in the cable. The disconnection or oxidation of the core wire can be detected by determining the resistance value of the core wire. The resistance value of the core wire can be calculated from the resistance value of the circuit including the core wire. Here, as a technique for detecting an abnormality of a cable having two core wires, a technique of measuring the resistance value between the other ends of the two core wires after short-circuiting the two core wires at one end, that is, two A technique for measuring a resistance value of a loop constituted by the core wire is known.

  For example, Patent Document 1 discloses a method of measuring resistance values of a plurality of loops having different combinations of electric wires constituting a loop and identifying variations in resistance values between the plurality of electric wires based on the measured resistance values. Has been. In this method, first, the resistance value (R1 + R3) of the loop composed of the electric wires 1 and 3 and the resistance value (R2 + R3) of the loop composed of the electric wires 2 and 3 are measured. To do. And when (R1-R2) which is the difference of (R1 + R3) and (R2 + R3) is more than a threshold value, it determines with the resistance value of the electric wire 1 and the resistance value of the electric wire 2 being imbalanced.

JP 2014-225875 A

  However, when a cable laid in the facility is an abnormality detection target, a device having an input resistance value that is not sufficiently large with respect to the resistance value of the core wire may be connected between the core wires. In this case, in the method disclosed in Patent Document 1, a current flows from one core wire to the other core wire through the device, and the resistance value of the loop cannot be accurately measured. The resistance value cannot be determined accurately. On the other hand, in order to accurately measure the resistance value of the loop, it is very troublesome to remove the device connected between the core wires. For this reason, even if a device is connected between the core wires, a technique for accurately obtaining a resistance value related to the resistance value of the core wire is desired.

  The present invention has been made in view of the above problems, and provides a resistance value measuring system and a resistance value measuring method for accurately obtaining a resistance value related to a resistance value of a core wire even when devices are connected between the core wires. The purpose is to provide.

In order to achieve the above object, a resistance measurement system according to the present invention includes:
One end of a measurement object including a first core wire, a second core wire, and a shield wire, and a plurality of cables connected in series, one end of the first core wire, one end of the second core wire, and the shield wire The other end of the first core wire in a state where the other end of the first core wire and the other end of the second core wire are connected to each other at the other end of the measurement object. And a resistance value measuring instrument for measuring a resistance value between the shield wire and the other end of the shield wire,
A display device that displays information based on the resistance value measured by the resistance value measuring instrument.

  In the present invention, even if a device is connected between the core wires, no current flows through the device when measuring the resistance value. Therefore, according to the present invention, even if a device is connected between the core wires, the resistance value associated with the resistance value of the core wire can be accurately obtained.

It is a block diagram of the resistance value measurement system which concerns on embodiment of this invention. It is a block diagram of the arithmetic unit which concerns on embodiment of this invention. It is a figure which shows the to-be-measured circuit which concerns on embodiment of this invention. It is a figure which shows the equivalent circuit of the to-be-measured circuit which concerns on embodiment of this invention. It is a figure which shows the to-be-measured circuit which concerns on a comparative example. It is a flowchart which shows the resistance value measurement process which concerns on embodiment of this invention.

  Embodiments of the present invention will be described below with reference to the drawings. First, a resistance value measurement system 1000 according to an embodiment of the present invention will be described with reference to FIG. The resistance value measurement system 1000 is a system that measures the resistance value of the circuit under measurement 510 constituted by the measurement object 500. In the present embodiment, the measurement object 500 is configured by connecting a plurality of cables in series. The resistance value measurement system 1000 has a function of displaying the measured resistance value, a function of calculating the resistance value of the core wire included in the cable from the measured resistance value, a function of displaying the calculated resistance value, and the like.

  The user can detect an abnormality of the cable with reference to the displayed resistance value. When the displayed resistance value is the measured resistance value, the user calculates the resistance value of the core wire from the measured resistance value using a calculation formula described later. On the other hand, when the displayed resistance value is the calculated resistance value, the user does not need to calculate the resistance value of the core wire. The user can determine whether or not the calculated resistance value of the core wire is a normal resistance value, and can determine whether or not there is an abnormality in the cable. The abnormality of the cable is, for example, disconnection of the core wire, poor contact of the core wire, oxidation of the core wire, or the like. As shown in FIG. 1, the resistance value measurement system 1000 includes an arithmetic device 100, a resistance value measuring device 200, and a display device 300.

  The arithmetic device 100 is a device that forms the core of the resistance value measurement system 1000 and executes resistance value measurement processing. The arithmetic device 100 causes the display device 300 to display the measured resistance value of the circuit under measurement 510. In addition, the arithmetic device 100 calculates the resistance value of the core wire from the measured resistance value and causes the display device 300 to display it. The arithmetic device 100 acquires information indicating the measured resistance value from the resistance value measuring device 200.

  The arithmetic device 100 is a personal computer, a tablet terminal, a smartphone, or the like. Hereinafter, the configuration of the arithmetic device 100 will be described with reference to FIG. As shown in FIG. 2, the arithmetic device 100 includes a CPU (Central Processing Unit) 101, a ROM (Read Only Memory) 102, a RAM (Random Access Memory) 103, a hard disk 104, an RTC (Real Time Clock) 105, and an operation receiving unit. 106, a display control unit 107, and a communication unit 108. Each component included in the arithmetic device 100 is connected to each other via a bus.

  The CPU 101 controls the overall operation of the arithmetic device 100. Note that the CPU 101 operates according to a program stored in the ROM 102 and uses the RAM 103 as a work area. The ROM 102 stores a program and data for controlling the overall operation of the arithmetic device 100. The RAM 103 functions as a work area for the CPU 101. That is, the CPU 101 temporarily writes programs and data in the RAM 103 and refers to these programs and data as appropriate.

  The hard disk 104 is a non-volatile storage device that stores various types of information. For example, the hard disk 104 stores information indicating a calculation formula for calculating the resistance value of the core wire from the measured resistance value and information used in the calculation formula. The information used in the calculation formula is, for example, cable information indicating a correspondence relationship between the cable model number and the resistance value ratio. The resistance value ratio is a ratio of the resistance value per unit length of the core wire to the resistance value per unit length of the shield wire. That is, the resistance value ratio is determined in advance for each cable type (cable model number).

  The RTC 105 is a time measuring device. The RTC 105 incorporates a battery, for example, and continues timing while the power of the arithmetic device 100 is off. The RTC 105 includes an oscillation circuit including a crystal oscillator, for example. The operation reception unit 106 detects an operation by the user and supplies a signal indicating the detection result to the CPU 101. The operation reception unit 106 is, for example, a touch screen, a mouse, a keyboard, or the like. The display control unit 107 displays various types of information on the display device 300 according to control by the CPU 101. The display control unit 107 includes, for example, a graphic card.

  The communication unit 108 communicates with the resistance value measuring device 200 according to control by the CPU 101. That is, the communication unit 108 is an interface for connecting the arithmetic device 100 to the resistance value measuring device 200. For example, the communication unit 108 transmits a signal instructing the start of measurement to the resistance value measuring device 200 or receives information indicating the measured value of the resistance value from the resistance value measuring device 200. The communication unit 108 includes interfaces such as a LAN (Local Area Network), a USB (Universal Serial Bus), and an IEEE (Institute of Electrical and Electronic Engineers) 1394, for example.

  The resistance value measuring instrument 200 measures the resistance value of the circuit under measurement 510 that is a circuit to be measured. The resistance value measuring instrument 200 measures the voltage value between the measurement terminals when a constant current is passed between the measurement terminals, or the current value flowing between the measurement terminals when a constant voltage is applied between the measurement terminals. By measuring, the resistance value between the measurement terminals is measured. The resistance value measuring device 200 includes a changeover switch 210, a display unit 220, a measurement terminal 231, and a measurement terminal 232. The changeover switch 210 is a switch for changing the measurement mode, the range, and the like. The measurement mode is a mode for designating a physical quantity (for example, a resistance value, a voltage value, or a current value) to be measured, for example. The display unit 220 displays the measured resistance value. The measurement terminal 231 and the measurement terminal 232 are terminals connected to the circuit under measurement 510. That is, the resistance value between the measurement terminal 231 and the measurement terminal 232 is measured. The resistance value measuring device 200 has a function of communicating with the communication unit 108 included in the arithmetic device 100. That is, the resistance value measuring device 200 has the same configuration as that of the communication unit 108. The resistance value measuring device 200 is, for example, a digital multimeter or a tester.

  The display device 300 displays information based on the measured resistance value of the circuit under measurement 510 according to the control by the arithmetic device 100. For example, the display device 300 displays the measured resistance value of the circuit under measurement 510 and the calculated resistance value of the core wire. The display device 300 receives information indicating the resistance value to be displayed from the arithmetic device 100. The display device 300 is, for example, a liquid crystal display.

  The device 410 is, for example, a management device that manages facility devices and facility devices arranged in the facility. For example, the device 410 is connected between core wires at a connection portion of a cable in order to receive data from another device. The device 410 includes an input interface 411, a terminal 415, and a terminal 416. The input interface 411 is an interface for receiving data from other devices. The input interface 411 includes a processing unit 412, a coil 413, and a coil 414. The processing unit 412 receives data from other devices via a transformer composed of the coil 413 and the coil 414. The coil 413 and the coil 414 constitute a transformer. The terminal 415 and the terminal 416 are respectively connected to different core wires at the cable connection portion.

  The device 420 basically has the same configuration and function as the device 410. That is, the device 420 is connected between the core wires at the connection portion of the cable in order to receive data from other devices. The device 420 includes an input interface 421, a terminal 425, and a terminal 426. The input interface 421 includes a processing unit 422, a coil 423, and a coil 424.

  Next, the circuit under measurement 510 will be described. The circuit under measurement 510 is basically a circuit composed of the measurement object 500. In this embodiment, the measurement object 500 includes a terminal block 40, a terminal block 50, a terminal block 60, and a terminal block 70, and the cable 110, the cable 120, and the cable 130 are connected in series and fixed in the facility. It shall be. In the present embodiment, the resistance value measurement process is executed in a state where the measurement object 500 is arranged in the facility.

  Here, when the device 410 or the device 420 is connected to the measurement object 500, the circuit under measurement 510 includes the input resistance of the device 410 or the input resistance of the device 420. The input resistance of the device 410 is configured by a coil 413, for example. The input resistance of the device 420 is constituted by a coil 423, for example. The resistance value of the input resistance of the device 410 and the input resistance of the device 420 is, for example, about 0.5Ω. Therefore, it cannot be said that the resistance values of these input resistors are sufficiently large relative to the resistance values of the core wires included in the cable. That is, depending on the resistance value measurement method, when the device 410 or the device 420 is connected between the core wires, a current may flow between the core wires through the input resistance.

  The cable 110 is a cable that is laid in facilities such as buildings and factories and used for supplying power and transmitting electrical signals. The cable 110 is a shielded two-core cable, and includes a core wire 11, a core wire 21, a shield wire 31, an insulating member 111, an insulating member 112, and an insulating member 113. The core wire 11 and the core wire 21 are electric wires for transmitting electric power and electric signals, and are made of, for example, copper or aluminum. The shield wire 31 covers and shields the core wire 11 and the core wire 21. That is, the shield wire 31 prevents noise radiated from the external space from entering the core wire 11 and the core wire 21. Further, the shield wire 31 prevents noise from being radiated from the core wire 11 or the core wire 21 to the external space. The shield wire 31 is connected to the chassis of the device and grounded. Therefore, no element is intentionally connected to the shield wire 31. The shield wire 31 is made of, for example, copper or aluminum. The insulating member 111 is an insulator that covers the core wire 11. The insulating member 112 is an insulator that covers the core wire 21. The insulating member 113 is an insulator that covers the shield wire 31. The insulating member 111, the insulating member 112, and the insulating member 113 are made of, for example, vinyl chloride resin.

  The cable 120 and the cable 130 are shielded two-core cables, and basically have the same configuration and function as the cable 110 except for the length. That is, the cable 110, the cable 120, and the cable 130 are cables of the same model number. The cable 120 includes a core wire 12, a core wire 22, a shield wire 32, an insulating member 121, an insulating member 122, and an insulating member 123. The cable 130 includes a core wire 13, a core wire 23, a shield wire 33, an insulating member 131, an insulating member 132, and an insulating member 133.

  One end of the cable 110 is connected to the resistance value measuring device 200 via a terminal block 40 including a terminal 41, a terminal 42, and a terminal 43. Specifically, one end of the core wire 11 is connected to the terminal 41, one end of the core wire 21 is connected to the terminal 42, and one end of the shield wire 31 is connected to the terminal 43. Further, the measurement terminal 231 is connected to the terminal 41, and the measurement terminal 232 is connected to the terminal 43. The measurement terminal 231 and the terminal 41 are connected by, for example, a lead wire with a clip. Similarly, the measurement terminal 232 and the terminal 43 are connected by, for example, another lead wire with a clip. Further, when measuring the resistance value, the user connects the terminal 41 and the terminal 42 by the lead wire 81. Thereby, one end of the core wire 11 and one end of the core wire 21 are connected.

  The other end of the cable 110 is connected to one end of the cable 120 via a terminal block 50 including a terminal 51, a terminal 52, and a terminal 53. Specifically, the other end of the core wire 11 is connected to the terminal 51, the other end of the core wire 21 is connected to the terminal 52, and the other end of the shield wire 31 is connected to the terminal 53. One end of the core wire 12 is connected to the terminal 51, one end of the core wire 22 is connected to the terminal 52, and one end of the shield wire 32 is connected to the terminal 53. The other end of the cable 120 is connected to one end of the cable 130 via a terminal block 60 including a terminal 61, a terminal 62, and a terminal 63. Specifically, the other end of the core wire 12 is connected to the terminal 61, the other end of the core wire 22 is connected to the terminal 62, and the other end of the shield wire 32 is connected to the terminal 63. One end of the core wire 13 is connected to the terminal 61, one end of the core wire 23 is connected to the terminal 62, and one end of the shield wire 33 is connected to the terminal 63.

  The other end of the cable 130 is connected to a terminal block 70 including a terminal 71, a terminal 72, and a terminal 73. Specifically, the other end of the core wire 13 is connected to the terminal 71, the other end of the core wire 23 is connected to the terminal 72, and the other end of the shield wire 33 is connected to the terminal 73. Further, when measuring the resistance value, the user connects the terminal 71 and the terminal 72 by the lead wire 82 and connects the terminal 72 and the terminal 73 by the lead wire 83. Thereby, the other end of the core wire 13, the other end of the core wire 23, and the other end of the shield wire 33 are connected.

  As described above, by connecting each part, the core wire 11, the core wire 12, and the core wire 13 are connected in series to form one core wire (hereinafter, referred to as “first core wire” as appropriate). Further, the core wire 21, the core wire 22, and the core wire 23 are connected in series to constitute one core wire (hereinafter, referred to as “second core wire” as appropriate). Further, the shield wire 31, the shield wire 32, and the shield wire 33 are connected in series to constitute one shield wire. That is, the measurement object 500 includes a first core wire, a second core wire, and a shield wire, and the cable 110, the cable 120, and the cable 130 are connected in series.

  In addition, at one end of the measurement object 500, one end of the first core wire, one end of the second core wire, and one end of the shield wire are connected to each other. One end of the measurement object 500 is the other end of the cable 130 and is a connection portion of the cable 130 to the terminal block 70. One end of the measurement object 500 can be said to be the far end of the measurement object 500 when viewed from the resistance value measuring device 200. One end of the first core wire is the other end of the core wire 13 and is a connection portion to the terminal 71 of the core wire 13. One end of the second core wire is the other end of the core wire 23 and is a connection portion of the core wire 23 to the terminal 72. One end of the shield wire is the other end of the shield wire 33 and is a connection portion of the shield wire 33 to the terminal 73. Further, at the other end of the measuring object 500, the other end of the first core wire and the other end of the second core wire are connected to each other. The other end of the measurement object 500 is one end of the cable 110 and is a connection portion of the cable 110 to the terminal block 40. The other end of the measurement object 500 can be said to be the near end of the measurement object 500 when viewed from the resistance value measuring device 200. The other end of the first core wire is one end of the core wire 11 and is a connection portion to the terminal 41 of the core wire 11. The other end of the second core wire is one end of the core wire 21 and is a connection portion to the terminal 42 of the core wire 21.

  In such a state, the resistance value measuring device 200 measures the resistance value between the other end of the first core wire and the other end of the shield wire. The other end of the shield wire is one end of the shield wire 31 and is a connection portion to the terminal 43 of the shield wire 31. That is, the resistance value measuring instrument 200 measures the resistance value between the terminal 41 and the terminal 43. Then, the resistance value measuring instrument 200 displays the measured resistance value on the display unit 220. In addition, the display device 300 displays information based on the resistance value measured by the resistance value measuring device 200.

  Next, the circuit under test 510 will be described with reference to FIG. In the measured circuit 510, one end of the first core wire, one end of the second core wire, and one end of the shield wire are connected to each other, and the other end of the first core wire, the other end of the second core wire, and the measurement terminal 231 are mutually connected. The circuit is connected and the other end of the shielded wire is connected to the measurement terminal 232. That is, the measured circuit 510 is a circuit in which the first core wire and the second core wire are connected in parallel with the shield wire in series.

  The resistor R11 indicates the resistance component of the core wire 11, the resistor R12 indicates the resistance component of the core wire 12, and the resistor R13 indicates the resistance component of the core wire 13. The resistor R21 indicates the resistance component of the core wire 21, the resistor R22 indicates the resistance component of the core wire 22, and the resistor R23 indicates the resistance component of the core wire 23. The resistor R31 indicates the resistance component of the shield wire 31, the resistor R32 indicates the resistance component of the shield wire 32, and the resistor R33 indicates the resistance component of the shield wire 33. Here, the resistance value of the resistor R11 is r11, the resistance value of the resistor R12 is r12, the resistance value of the resistor R13 is r13, the resistance value of the resistor R21 is r21, the resistance value of the resistor R22 is r22, and the resistance value of the resistor R23 is r23. The resistance value of the resistor R31 is r31, the resistance value of the resistor R32 is r32, and the resistance value of the resistor R33 is r33.

  A resistor R410 indicates an input resistance of the input interface 411 included in the device 410, and indicates a resistance component of the coil 413. The resistor R410 is generated when the terminal 415 included in the device 410 is connected to the terminal 51 and the terminal 416 included in the device 410 is connected to the terminal 52. A resistor R420 indicates an input resistance of the input interface 421 included in the device 420, and indicates a resistance component of the coil 423. The resistor R420 is generated when the terminal 425 included in the device 420 is connected to the terminal 61 and the terminal 426 included in the device 420 is connected to the terminal 62.

  Here, the core wire 11 and the core wire 21 have the same length. Therefore, if the core wire 11 and the core wire 21 are made of the same material and have the same cross-sectional area, r11 = r21. Moreover, the core wire 12 and the core wire 22 are the same length. Therefore, if the core wire 12 and the core wire 22 are made of the same material and have the same cross-sectional area, r12 = r22. Moreover, the core wire 13 and the core wire 23 are the same length. Therefore, if the core wire 13 and the core wire 23 are made of the same material and have the same cross-sectional area, r13 = r23. In the present application, “same” does not indicate complete coincidence, but means substantially the same. The meaning of the equal sign “=” also means substantially the same.

  As described above, when the relationship r11 = r21, r12 = r22, r13 = r23 is established, when the resistance value is measured by the resistance value measuring device 200, no potential difference occurs between both ends of the resistor R410, and the resistor R420. There is no potential difference between the two ends. As a result, no current flows through the resistor R410, and no current flows through the resistor R420. That is, the measured circuit 510 shown in FIG. 3 is equivalent to the equivalent circuit 520 shown in FIG. 4 when measuring the resistance value. As shown in FIG. 4, the equivalent circuit 520 is a circuit in which the resistor R410 and the resistor R420 are excluded from the circuit under measurement 510.

Here, assuming that the resistance value when the equivalent circuit 520 is viewed from the resistance value measuring device 200 is rtot, rtot can be expressed as in Expression (1).
rtot = (r11 + r12 + r13) × (r21 + r22 + r23) / ((r11 + r12 + r13) + (r21 + r22 + r23)) + (r31 + r32 + r33) Formula (1)

Further, considering the relationship r11 = r21, r12 = r22, r13 = r23, the equation (2) can be derived from the equation (1).
rtot = (r11 + r12 + r13) / 2 + (r31 + r32 + r33) Formula (2)

Here, the resistance ratio is A. The resistance value ratio is a ratio of the resistance value per unit length of the first core wire to the resistance value per unit length of the shield wire. Since the length of the shield wire and the length of the first core wire are the same, the resistance value ratio is also the ratio of the resistance value of the first core wire to the resistance value of the shield wire. Further, since the first core wire and the second core wire are basically the same, the resistance value ratio is also the ratio of the resistance value of the second core wire to the resistance value of the shield wire. A is predetermined according to the types of the cable 110, the cable 120, and the cable 130, and can be specified from the cable information and the model number. When the first core wire and the shield wire are the same material, the ratio of the cross-sectional area of the shield wire to the cross-sectional area of the first core wire is A. Moreover, since the cable 110, the cable 120, and the cable 130 are cables of the same model number, the expression (3) is established.
(R11 + r12 + r13) = A (r31 + r32 + r33) Formula (3)

Moreover, Formula (4) is derived from Formula (2) and Formula (3).
rtot = (1/2 + 1 / A) × (r11 + r12 + r13) Formula (4)

Furthermore, when the resistance value of the first core wire and the resistance value of the second core wire are r1, Equation (5) is derived from Equation (4). The arithmetic device 100 can calculate the resistance value of the first core wire and the resistance value of the second core wire from the measured resistance value using the equation (4) or the equation (5).
rtot = (1/2 + 1 / A) × r1 Formula (5)

  Here, a circuit 530 according to a comparative example will be described with reference to FIG. The circuit 530 is a circuit in which a loop is formed by a first core wire and a second core wire without using a shield wire. That is, the circuit 530 is a circuit in which one end of the first core wire and one end of the second core wire are connected to each other, and the other end of the first core wire and the other end of the second core wire are opened. The resistor R410 and the resistor R420 are assumed to be about 0.5Ω, for example. Accordingly, the resistors R410 and R420 are not sufficiently large relative to the resistors R11, R12, R13, R21, R22, R23, and the like. In particular, the resistor R410 is not sufficiently large relative to the resistor R12. Therefore, as shown in FIG. 5, when the resistance value is measured by the resistance value measuring instrument 200, most of the current that should flow through the resistor R12 flows through the resistor R410.

  Next, the resistance value measurement process executed by the resistance value measurement system 1000 will be described with reference to the flowchart shown in FIG. The resistance value measurement process is basically executed according to control by the CPU 101 provided in the arithmetic device 100. The CPU 101 starts the resistance value measurement process after receiving an instruction to start the resistance value measurement process from the user. For example, the CPU 101 receives a start instruction from the user via the operation receiving unit 106. Hereinafter, accepting information from the user via the operation accepting unit 106 by the CPU 101 is simply referred to as simply accepting information from the user by the CPU 101.

  First, the CPU 101 instructs preparation for measurement (step S101). For example, the CPU 101 controls the display control unit 107 to display on the display device 300 a screen that prompts the user to prepare for measurement. Specifically, the preparation for the measurement is specifically the connection between the terminal 41 and the terminal 42 by the lead wire 81, the connection between the terminal 71 and the terminal 72 by the lead wire 82, and the connection between the terminal 72 and the terminal 73 by the lead wire 83. Connection between the measurement terminal 231 and the terminal 41, connection between the measurement terminal 232 and the terminal 42, and the like. Note that the preparation for measurement does not include the removal work of the device 410 or the removal work of the device 420.

  When the CPU 101 completes the process of step S101, it determines whether the preparation is completed (step S102). For example, the CPU 101 determines whether or not an operation indicating that preparation has been completed has been received from the user.

  If the CPU 101 determines that preparation has not been completed (step S102: NO), it returns the process to step S102. On the other hand, if the CPU 101 determines that the preparation has been completed (step S102: YES), the CPU 101 acquires the cable model number (step S103). For example, the CPU 101 accepts designation of the model number of the cable 110 from the user.

  CPU101 will measure the resistance value between measuring terminals, if the process of step S103 is completed (step S104). Specifically, the CPU 101 instructs the resistance value measuring device 200 to start measuring the resistance value via the communication unit 108. And CPU101 acquires the information which shows the resistance value measured from the resistance value measuring device 200 via the communication part 108. FIG.

  When completing the process in step S104, the CPU 101 displays the measured resistance value (step S105). For example, the CPU 101 controls the display control unit 107 to display the measured resistance value on the display device 300.

  When completing the process in step S105, the CPU 101 calculates a resistance value of the first core wire (step S106). For example, the CPU 101 calculates the resistance value of the first core wire from the above-described equation (4) or (5), the cable information stored in the hard disk 104, and the acquired cable model number.

  When the CPU 101 completes the process of step S106, the CPU 101 displays the calculated resistance value (step S107). For example, the CPU 101 controls the display control unit 107 to cause the display device 300 to display the calculated resistance value, that is, the estimated value of the resistance value of the first core wire.

  As described above, in this embodiment, even if a device is connected between the core wires, no current flows through the device when measuring the resistance value. Therefore, according to this embodiment, even if an apparatus is connected between the core wires, it is possible to accurately obtain the resistance value related to the resistance value of the core wire. Moreover, in this embodiment, when the apparatus is connected between the core wires, the user does not need to remove the apparatus before measuring the resistance value. Therefore, according to the present embodiment, the time required for preparation for measuring the resistance value can be shortened, and the labor required for preparation can be reduced. Further, according to the present embodiment, it is not necessary to check whether or not a device is connected.

  In the present embodiment, the measured resistance value is displayed. Therefore, according to the present embodiment, it is possible to notify the user of information effective for determining whether or not there is an abnormality in the first core wire or the second core wire.

  In the present embodiment, the resistance value of the first core wire calculated from the measured resistance value is displayed. Therefore, according to the present embodiment, it is possible to notify the user of information that is more effective for determining whether or not there is an abnormality in the first core wire or the second core wire.

  In the present embodiment, the resistance value of the first core wire can be calculated by a simple calculation formula. Therefore, according to the present embodiment, it is possible to calculate the resistance value of the first core wire without increasing the processing load of the arithmetic device 100 so much.

(Modification)
As mentioned above, although embodiment of this invention was described, when implementing this invention, a deformation | transformation and application with a various form are possible.

  In the present invention, which part of the configuration, function, and operation described in the above embodiment is adopted is arbitrary. Further, in the present invention, in addition to the configuration, function, and operation described above, further configuration, function, and operation may be employed. Further, any device may have the above-described function, and the above-described function may be executed as the entire system.

  For example, since the resistance value measuring device 200 has a function of displaying the measured resistance value on the display unit 220, the arithmetic device 100 and the display device 300 are not essential components. Further, when the arithmetic device 100 has a display function, the display device 300 may not be provided. Further, the resistance value measuring device 200 may have the function of the arithmetic device 100.

  In the above embodiment, the example in which the measurement object 500 is configured by three cables has been described. In the present invention, the number of cables constituting the measurement object 500 may be two, or four or more. In addition, the present invention can also be applied to a case where the core wire and the shield wire are taken out from the covering at the intermediate portion of one cable and the device is connected. Further, the types of cables constituting the measurement object 500 may be different. This is because even in this case, current does not flow to the device connected to the connection portion of the cable.

  In the above embodiment, an example in which the present invention is applied to a shielded two-core cable has been described. The present invention can be applied to a shielded multi-core cable having three or more core wires. In this case, it is only necessary to connect and measure two cores selected from three or more core wires as the first core wire and the second core wire.

  By applying an operation program that defines the operation of the arithmetic device 100 according to the present invention to an existing personal computer or information terminal device, the personal computer can also function as the arithmetic device 100 according to the present invention.

  Further, such a program distribution method is arbitrary. For example, the program is stored and distributed in a computer-readable recording medium such as a CD-ROM (Compact Disk Read-Only Memory), a DVD (Digital Versatile Disk), or a memory card. Alternatively, it may be distributed via a communication network such as the Internet.

  Various embodiments and modifications can be made to the present invention without departing from the broad spirit and scope of the present invention. Further, the above-described embodiment is for explaining the present invention, and does not limit the scope of the present invention. That is, the scope of the present invention is shown not by the embodiments but by the claims. Various modifications within the scope of the claims and within the scope of the equivalent invention are considered to be within the scope of the present invention.

  The present invention is applicable to a system that detects a cable abnormality.

11, 12, 13, 21, 22, 23 Core wire, 31, 32, 33 Shield wire, 40, 50, 60, 70 Terminal block, 41, 42, 43, 51, 52, 53, 61, 62, 63, 71 , 72, 73 terminals, 81, 82, 83 Lead wire, 100 arithmetic unit, 101 CPU, 102 ROM, 103 RAM, 104 hard disk, 105 RTC, 106 operation accepting unit, 107 display control unit, 108 communication unit, 110, 120 , 130 Cable, 111, 112, 113, 121, 122, 123, 131, 132, 133 Insulating member, 200 Resistance measuring device, 210 Changeover switch, 220 Display unit, 231, 232 Measurement terminal, 300 Display device, 410, 420 equipment, 411, 421 input interface, 412, 422 processing unit, 413 414, 423, 424 Coil, 415, 416, 425, 426 terminal, 500 measurement object, 510 measured circuit, 520 equivalent circuit, 530 circuit, 1000 resistance measurement system, R11, R12, R13, R21, R22, R23 , R31, R32, R33, R410, R420 Resistance

Claims (7)

One end of a measurement object including a first core wire, a second core wire, and a shield wire, and a plurality of cables connected in series, one end of the first core wire, one end of the second core wire, and the shield wire The other end of the first core wire in a state where the other end of the first core wire and the other end of the second core wire are connected to each other at the other end of the measurement object. And a resistance value measuring instrument for measuring a resistance value between the shield wire and the other end of the shield wire,
A display device for displaying information based on the resistance value measured by the resistance value measuring instrument,
Resistance measurement system. An arithmetic device for calculating the resistance value of the first core wire from the resistance value measured by the resistance value measuring instrument;
The display device displays information indicating a resistance value of the first core wire calculated by the arithmetic device;
The resistance value measurement system according to claim 1. The resistance value of the first core wire and the resistance value of the second core wire are the same,
The arithmetic unit calculates r1 which is a resistance value of the first core wire, rtot which is a resistance value measured by the resistance measuring device, and a ratio of the resistance value of the first core wire to the resistance value of the shield wire. Using a certain A, and calculating by rtot = (1/2 + 1 / A) × r1,
The resistance value measurement system according to claim 2. One end of a measurement object including a first core wire, a second core wire, and a shield wire, and a plurality of cables connected in series, one end of the first core wire, one end of the second core wire, and the shield wire The other end of the first core wire in a state where the other end of the first core wire and the other end of the second core wire are connected to each other at the other end of the measurement object. And measuring the resistance value between the other end of the shield wire,
Resistance value measurement method. At one end of the measurement object, one end of the first core wire, one end of the second core wire, and one end of the shield wire are connected to each other, and at the other end of the measurement object, the other end of the first core wire And the other end of the second core wire are connected to each other, and further, the first core wire and the second core wire are connected to each other via a device at a connection portion of the plurality of cables, Measuring a resistance value between the other end of the first core wire and the other end of the shield wire;
The resistance value measuring method according to claim 4. Displaying the measured resistance value;
The resistance value measuring method according to claim 5. Based on the measured resistance value and the ratio of the resistance value of the first core wire to the resistance value of the shield wire, the resistance value of the first core wire is calculated,
Displaying the calculated resistance value of the first core wire;
The resistance value measuring method according to claim 5 or 6.

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