RFID tags, continuity determination devices

Abstract

To detect a continuity state between two metal bodies without contacting them.SOLUTION: An RFID tag 20 comprises: a base substrate 21 that is in a block shape elongated in one direction; an antenna substrate 22 that is arranged in a state of being superimposed on a first surface 21A of the base substrate 21; an IC chip module 23 that is located between the base substrate 21 and the antenna substrate 22 and including a first electrode 33A and a second electrode 33B on a surface facing the base substrate 21; a first detection terminal 25A that is electrically connected to the first electrode 33A of the IC chip module 23; and a second detection terminal 25B that is electrically connected to the second electrode 33B of the IC chip module 23. The first detection terminal 25A and the second detection terminal 25B are electrically connected to a first metal body M1 and a second metal body M2, respectively. The antenna substrate 22 transmits a detection result of presence or absence of continuity between the two metal bodies via radio waves.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an RFID tag that detects the presence or absence of continuity between two points, and a continuity determining device that determines the presence or absence of continuity. [Background technology]

[0002] The corrosion protection sheet for steel materials described in Patent Document 1 electrically connects the steel material and a thin base metal plate (sacrificial anticorrosion material) with a conductive adhesive, thereby suppressing corrosion of the steel material through a sacrificial anticorrosion effect. However, if the electrical connection between the steel material and the thin base metal plate is interrupted, the anticorrosion effect is lost. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 4643288 Summary of the Invention [Problem to be solved by the invention]

[0004] The presence or absence of electrical continuity between metal objects can be determined using a tester, for example, but this requires polishing the surface beforehand to expose the metal. Furthermore, if the object being inspected, such as a sacrificial protective material, is located at a high altitude, scaffolding must be installed. If the presence or absence of electrical continuity could be determined without contact, surface polishing and scaffolding would be unnecessary, improving work efficiency.

[0005] The present invention was completed based on the above circumstances, and aims to realize an RFID tag that detects the conductivity between metal objects, and a conductivity determination device that determines the conductivity between metal objects in a non-contact manner. [Means for solving the problem]

[0006] The RFID tag of the present invention comprises a block-shaped base substrate that is long in one direction, an antenna substrate that is placed on top of a first surface of the base substrate, an IC chip module that is located between the base substrate and the antenna substrate and has a first electrode and a second electrode on the surface facing the base substrate, a first detection terminal that is electrically connected to the first electrode of the IC chip module, and a second detection terminal that is electrically connected to the second electrode of the IC chip module, wherein the first detection terminal and the second detection terminal are electrically connected to a first metal body and a second metal body, respectively, and the antenna substrate transmits the detection result of whether or not there is conductivity between the two metal bodies via radio waves.

[0007] In this way, the detection result of whether or not there is continuity can be transmitted contactlessly via radio waves.

[0008] The following configuration is a preferred embodiment of the present invention: the base substrate is made of an insulating material and has a second surface opposite the first surface, the second surface being spaced apart from the first surface by at least a predetermined distance, and the RFID tag is attached to the metal body with the second surface serving as the attachment surface.

[0009] If the distance between the metal body and the IC chip module is less than a specified distance, the IC chip module may be affected by external disturbances, which may reduce the accuracy of detection.However, if the distance between the first and second surfaces is greater than a specified distance, the metal body and the IC chip module are separated by more than the specified distance, reducing the effects of external disturbances and enabling more accurate detection of continuity.

[0010] The RFID tag has a clip that holds the antenna substrate against the base substrate, and the first detection terminal and the second detection terminal maintain contact with the first electrode and the second electrode due to the elastic force of the clip, thereby maintaining electrical connection with the electrodes.

[0011] Each terminal and electrode is held in contact by a clip, maintaining electrical connection. Because the terminal is not fixed to the electrode, even if the electrode and terminal are misaligned due to temperature changes and differences in linear expansion coefficients, the connection will not be damaged and a good connection can be maintained. This makes the RFID tag resistant to temperature changes.

[0012] The continuity determination device includes an RFID tag and a reader that reads the detection result from the RFID tag in a non-contact manner, so that the detection result from the RFID tag can be received using the reader in a non-contact manner.

[0013] The first detection terminal and the second detection terminal may be connected to a combination of metals that have a sacrificial protection effect, and whether or not the sacrificial protection effect is being maintained can be determined based on whether or not there is electrical continuity.

[0014] The reader includes a reader-side antenna that transmits and receives radio waves to and from the RFID tag, and a control unit. The RFID tag is a passive type that receives power from the received radio waves, detects the conduction state, and transmits the detection results. The control unit may automatically adjust the level of the radio waves output to the RFID tag so that the reader-side antenna can receive the detection results transmitted by the RFID tag.

[0015] In this way, the reader can receive the detection result of the RFID tag more reliably.

[0016] The control unit may increase the level of the radio waves it outputs when the reader antenna cannot receive the detection result transmitted by the RFID tag. When the radio wave level increases, the power supplied from the reader to the RFID tag increases, and the level of the radio waves transmitted from the RFID tag to the reader also increases. This allows the reader to more reliably receive the radio waves from the RFID tag.

[0017] The detection result is a close signal that is detected when there is continuity between the first detection terminal and the second detection terminal, or an open signal that is detected when there is no continuity, and the control unit may determine whether there is continuity or not based on the order and number of the open signals and close signals received.

[0018] The detection results may contain errors that indicate results different from the actual continuity status. By determining whether or not there is continuity based on the order and number of open and close signals received by the reader, the influence of errors can be eliminated and the presence or absence of continuity can be determined more accurately.

[0019] The control unit may determine that there is no conduction between the first detection terminal and the second detection terminal if the open signal is received one or more times before receiving the close signal multiple times, and may determine that there is conduction between the first detection terminal and the second detection terminal if the close signal is received multiple times before receiving the open signal one or more times.

[0020] In this way, at least the first detected close signal is not used to determine whether or not there is continuity, so even if the first close signal is an error, it will not have any effect on the determination result. Accurate determination can be made based on the second and subsequent close signals. [Effects of the Invention]

[0021] The RFID tag of the present disclosure can transmit the detection result of the presence or absence of continuity without contact, and the continuity determination device of the present disclosure can determine the presence or absence of continuity without contact. [Brief explanation of the drawings]

[0022] [Figure 1] Continuity determination device [Figure 2] Perspective view of an RFID tag [Figure 3] Exploded view of an RFID tag [Figure 4a]Bottom view of IC chip module [Figure 4b] B-B cross section of IC chip module [Figure 5] AA cross section of RFID tag [Figure 6] Reader Block Diagram [Figure 7a] Illustration of error occurrence [Figure 7b] Illustration of error occurrence [Figure 7c] Illustration of error occurrence [Figure 7d] Illustration of error occurrence [Figure 8] Flowchart of continuity determination process DETAILED DESCRIPTION OF THE INVENTION

[0023] <Embodiment> An embodiment of the present invention will be described with reference to FIGS.

[0024] 1. Overall structure 1 is a diagram showing a continuity determination device 10 that detects the presence or absence of continuity between a metal body M1 constituting a steel structure and a metal body M2 that is a sacrificial protective material. The steel structure is, for example, a bridge, a steel tower, a signpost, or the like that is installed outdoors.

[0025] The continuity determination device 10 includes an RFID tag 20 electrically connected to metal bodies M1 and M2 via lead wires 27A and 27B, respectively, to detect the presence or absence of continuity between the metal bodies M1 and M2, and a reader 40 that contactlessly receives the detection results of the RFID tag 20. The metal bodies M1 and M2 are examples of a "first metal body" and a "second metal body," respectively. The RFID tag 20 is attached to the surface of the metal body M1 or M2.

[0026] 1 does not show the anticorrosion coating for protecting the metal bodies M1 and M2 and the RFID tag 20. The anticorrosion coating is in the form of a sheet, and is attached to the metal body M1 so as to cover the metal body M2 and the RFID tag 20.

[0027] The metal body M1 is a component constituting, for example, a steel structure installed outdoors, and is made of steel. The metal body M2 is a plate-shaped component made of a magnesium alloy, zinc alloy, aluminum alloy, or the like, which has a higher ionization tendency than steel. In this embodiment, as an example, the material of the metal body M2 is a magnesium alloy. The size of the metal body M2 is smaller than that of the metal body M1. The metal body M2 is attached to the surface of the metal body M1 via a conductive adhesive P.

[0028] The conductive adhesive P bonds the metal body M1 and the metal body M2 while maintaining electrical continuity between them. An example of the conductive adhesive P is an adhesive that uses an epoxy adhesive as a binder and has metal particles such as silver added thereto.

[0029] Due to the difference in the ionization tendency between metal bodies M1 and M2, metal body M2, which is electrically conductive with metal body M1, has a sacrificial corrosion protection effect. Specifically, when electrolytes such as water adhere to a steel structure, magnesium, zinc, aluminum, etc. in metal body M2 ionize (corrode), and the electrons generated by this move to metal body M1 via conductive adhesive P. As a result, corrosion of metal body M2 progresses, while corrosion of metal body M1 is suppressed.

[0030] If the electrical continuity between the metal bodies M1 and M2 is interrupted, the above-mentioned electron movement will no longer be possible, resulting in the loss of the anticorrosion effect and the progression of corrosion of the metal body M1. Therefore, by detecting the presence or absence of electrical continuity between the metal bodies M1 and M2, it is possible to determine whether the anticorrosion effect is being maintained.

[0031] Possible causes of loss of conductivity between the metal bodies M1 and M2 include separation of the metal body M2 from the conductive adhesive P and wear of the metal body M2 due to the progression of corrosion.

[0032] 2.About RFID Tag 20 2 to 6, the RFID tag 20 will be described. The RFID tag 20 has a function of detecting the electrical continuity between the metal bodies M1 and M2 in response to a request from the reader 40, and transmitting the detection result to the reader 40 by radio waves.

[0033] 2 and 3, RFID tag 20 includes base substrate 21, antenna substrate 22, IC chip module 23, clip 24, connection terminals 25 (25A, 25B), crimped terminal 26, and lead wires 27 (27A, 27B). In the following description, the longitudinal direction of base substrate 21 shown in FIG. 2 is defined as the X direction, the direction in which lead wires 27 extend from base substrate 21 is defined as the Y direction, and the direction perpendicular to both the X and Y directions is defined as the Z direction (vertical direction). Connection terminals 25A and 25B are examples of a "first detection terminal" and a "second detection terminal," respectively.

[0034] The base substrate 21 is made of insulating synthetic resin or the like, and has a substantially rectangular parallelepiped (block-like) shape that is long in the X direction. In the following description, the length of the base substrate 21 in the Z direction will also be referred to as the thickness of the base substrate 21.

[0035] A storage section 28 is recessed in the upper surface 21A of the base substrate 21 to store a connection terminal 25 and an IC chip module 23, which will be described later. The upper surface 21A is an example of a "first surface." The storage section 28 is made up of a first storage section 28A recessed in the upper surface 21A of the base substrate 21 and a second storage section 28B recessed in the bottom surface of the first storage section 28A.

[0036] The second storage section 28B stores some of the connection terminals 25, and the first storage section 28A stores the IC chip module 23.

[0037] The antenna substrate 22 has the function of improving the sensitivity of the inner layer antenna 32 by electromagnetically coupling with an inner layer antenna 32 formed on the inner layer of the IC chip module 23 described later.

[0038] The antenna substrate 22 is made of a metal plate such as an aluminum alloy, and includes an antenna body 22A that is long in the X direction, and four claws 22B that extend downward from the Y-direction edge of the antenna body 22A. The antenna body 22A covers the upper surface 21A of the base substrate 21, and is provided with a notch 22C in part to avoid interference with a clip 24, which will be described later.

[0039] Two pairs of claw portions 22B are arranged side by side with a gap in the Y direction, and are provided on the antenna substrate 22. The pair of claw portions 22B sandwich the base substrate 21 from both sides and fix the antenna substrate 22 to the base substrate 21.

[0040] The length of the claw portion 22B in the vertical direction is smaller than the thickness of the base substrate 21, and the claw portion 22B does not protrude below the lower surface 21B of the base substrate 21.

[0041] As shown in Figures 4(a) and 4(b), the IC chip module 23 has a package 29 and an IC chip 30. Figure 4(b) is a cross-sectional view taken along line BB of Figure 4(a). The package 29 is a rectangular laminated substrate made of ceramic as an insulating material, and the IC chip 30 is mounted on the package 29.

[0042] The IC chip module 23 is a module in which the IC chip 30 receives power from the radio waves emitted by the reader 40, detects the presence or absence of conduction between the two electrodes 33 (33A, 33B), and transmits the detection result to the reader 40. The IC chip module 23 is a so-called passive type, and does not require a power supply on the module side because it obtains power from the radio waves it receives.

[0043] The package 29 includes a cavity 31, an inner layer antenna 32, and two electrodes 33 (33A, 33B). The electrodes 33A and 33B are examples of a "first electrode" and a "second electrode," respectively.

[0044] The cavity 31 is a recessed portion that opens to the surface of the package 29, and the IC chip 30 is mounted at the bottom of the cavity 31. The bottom surface of the cavity 31 is provided with a plurality of electrodes (not shown) that are connected to the inner layer antenna 32 and the electrodes 33A and 33B, respectively. These electrodes are connected to the electrodes on the IC chip 30 by wire bonding. Wire bonding is a connection method that allows for a displacement tolerance in the wire and has high connection reliability against temperature changes.

[0045] The cavity 31 is completely filled with a molding material 35 made of epoxy resin or the like, which protects the IC chip 30 and the connection between the IC chip 30 and the package 29 .

[0046] The inner layer antenna 32 is an antenna formed by a conductor pattern provided on the inner layer of the package 29. The inner layer antenna 32 is electrically connected to the IC chip 30, and supplies power to the IC chip 30 and transmits and receives radio waves. Because the inner layer antenna 32 is electromagnetically coupled to the antenna body 22A, the inner layer antenna 32 and the antenna substrate 22 can be treated together as a single antenna with high sensitivity.

[0047] Since the RFID tag 20 is attached to the surface of the metal body M1 or metal body M2 (see FIG. 1), the antenna body 22A and the inner layer antenna 32 are susceptible to disturbances caused by radio waves reflected on the surfaces of the metal bodies M1 and M2. The influence of disturbances increases the closer the distance, so the antenna body 22A and the inner layer antenna 32 must be separated from the metal bodies M1 and M2 by a distance (a predetermined distance) or more that does not affect transmission and reception.

[0048] In the RFID tag 20, the thickness of the base substrate 21 is set to a predetermined distance or more. The bottom surface 21B, which faces the top surface 21A, is the attachment surface for the metal body M1. Since the base substrate 21 is located between the antenna main body 22A and the inner layer antenna 32 and the metal bodies M1 and M2, they are separated by a predetermined distance or more, making them less susceptible to external disturbances. The bottom surface 21B is an example of a "second surface." The thickness of the base substrate 21 can be changed as desired as long as it is equal to or greater than the predetermined distance.

[0049] The electrodes 33A and 33B are arranged side by side on the surface of the package 29. When the IC chip module 23 is stored in the first storage section 28A, the electrode 33 is located on the surface facing the base substrate 21. The electrodes 33A and 33B and the IC chip 30 are electrically connected in the inner layer of the package 29.

[0050] The connection terminal 25 is made of metal and includes a connection portion 251 and an extension portion 252 extending in the Y direction from the connection portion 251. The connection portion 251 is substantially square in shape, and has a cylindrical projection 253 formed on the upper surface thereof. The extension portion 252 is narrower than the connection portion 251 and has a rectangular shape that is longer in the Y direction. The connection terminal 25 and the lead wire 27 are joined and electrically connected via a crimped terminal 26.

[0051] As shown in FIG. 1, the two lead wires 27 are connected to the metal bodies M1 and M2, respectively.

[0052] Clip 24 is made by bending an elastic wire into a predetermined shape. As shown in Fig. 3, clip 24 is composed of upper contact portion 24A that contacts the upper surface of IC chip module 23, lower contact portion 24B that contacts the lower surface 21B of base substrate 21, and intermediate portion 24C that connects upper contact portion 24A and lower contact portion 24B.

[0053] 5, clip 24 uses its elastic force to clamp the upper surface of IC chip module 23 and lower surface 21B of base substrate 21, holding IC chip module 23 so that it does not separate from base substrate 21. At the same time, the elastic force of clip 24 presses electrodes 33 located on the bottom surface of IC chip module 23 against connection terminals 25. This maintains contact between electrodes 33 and connection terminals 25, maintaining electrical connection.

[0054] 3. About Leader 40 The reader 40 has the function of transmitting UHF band radio waves to the RFID tag 20 to supply power to it without contact and detect the presence or absence of continuity, and the function of receiving the radio waves transmitted by the RFID tag 20 and receiving the detection results. The reader 40 and the RFID tag 20 can supply power and communicate with each other even when they are several meters or more apart.

[0055] 6 is a block diagram showing the electrical configuration of the reader 40. The reader 40 includes a control unit 41, a transmission circuit 42, a reception circuit 43, a reader-side antenna 44, and a display unit 45.

[0056] The control unit 41 is a control device for the reader 40. The control unit 41 includes a CPU 46 and a memory 47.

[0057] The control unit 41 is a controller that controls the reader 40. The memory 47 stores a program for a continuity determination process that determines the level of radio waves to be transmitted to the RFID tag 20 and determines the presence or absence of continuity based on a signal received from the RFID tag 20. The memory 47 is also a storage medium that cumulatively stores received detection results.

[0058] The display unit 45 is a display device such as a liquid crystal panel or a touch panel, and displays information about the operating status of the reader 40, the level of the transmitted radio waves, the received detection results, and the like.

[0059] The transmitting circuit 42 outputs radio waves in the UHF band in response to instructions from the control unit 41. The radio waves are radiated from the reader-side antenna 44, and power is supplied to the RFID tag 20 that receives the radio waves. The radio wave level radiated from the reader-side antenna 44 is, for example, a maximum of 30 dBm. The reader-side antenna 44 also receives the detection result transmitted by the RFID tag 20. The received detection result is amplified by the receiving circuit 43 and then transmitted to the control unit 41.

[0060] 4. Detection principle and detection errors As described above, the RFID tag 20 detects the presence or absence of conduction between the metal bodies M1 and M2 using power supplied by the radio waves transmitted by the reader 40, and transmits the detection result to the reader 40. The detection principle of the RFID tag 20 and the occurrence of errors will be explained below.

[0061] 7(a) and (b) show a state in which two connection terminals 25 of an RFID tag 20 are shorted and an open state. As shown in Fig. 7(a), when the RFID tag 20 observes that an electric charge is discharged from one connection terminal 25A and that the electric charge has reached the other connection terminal 25B, it determines that there is continuity between the connection terminals 25 and transmits a "close signal CS" from the inner layer antenna 32. In contrast, as shown in Fig. 7(b), when it cannot observe an electric charge returning to connection terminal 25B or when it cannot discharge an electric charge from connection terminal 25A, it determines that there is no continuity between the connection terminals 25 and transmits an "open signal OS."

[0062] However, in actual measurements where metal bodies M1 and M2 are connected between connection terminals 25, RFID tag 20 may emit a "close signal CS (continuity present)" even if there is no conductivity between connection terminals 25.

[0063] 7(c) shows a state in which metal bodies M1 and M2 are separated and not conducting. However, when metal bodies M1 and M2 receive the radio waves emitted by reader 40, an electric charge is generated in them. The generated electric charge is supplied from metal body M2 to connection terminal 25B, and RFID tag 20 determines that the electric charge emitted from connection terminal 25A has returned to connection terminal 25B. In this case, an error occurs in which a "close signal CS" is transmitted, even though there is actually no conduction.

[0064] 7(d) shows a state in which the metal bodies M1 and M2 are electrically connected by the conductive adhesive P. In this state, electric charges generated in the metal body M1 upon receiving radio waves emitted by the reader 40 may be directed toward the connection terminal 25A.

[0065] In this case, even though there is actually electrical continuity between the connection terminals 25, the charge flowing from connection terminal 25A to metal body M1 is blocked by the charge generated in metal body M1 and cannot reach connection terminal 25B. Despite the actual continuity, an error occurs in which an "open signal OS" is transmitted.

[0066] In order to suppress the occurrence of errors, it is effective to reduce the amount of electric charge generated in the metal bodies M1 and M2 by lowering the level of the radio waves transmitted from the reader 40. However, if the level of the radio waves is low, the power supplied to the RFID tag 20 decreases, and the level of the radio waves transmitted by the RFID tag 20 also decreases, making it difficult for the reader 40 to receive the signals.

[0067] Therefore, the reader 40 performs a continuity determination process, which will be described later, to accurately determine whether or not there is continuity even if an error occurs.

[0068] 5. Continuity determination process 8 is a flowchart of the continuity determination process performed by the control unit 41 of the reader 40. The memory 47 stores a program for executing the following flowchart.

[0069] When the continuity determination process is started in response to an instruction from the control unit 41, the control unit 41 adjusts the initial value of the radio wave level emitted by the reader 40 (S10). The initial value of the radio wave level is automatically set by the control unit 41 based on, for example, the distance between the reader 40 and the RFID tag 20. The initial value of the radio wave level may be input by the user of the reader 40 as an arbitrary value, or may be set to the smallest possible value.

[0070] As a general rule, the greater the distance between the reader 40 and the RFID tag 20, the larger the initial value of the radio wave level is set to. For example, the initial value is 9 dBm when the distance is 50 cm, 15 dBm when the distance is 50 cm to 2 m, and 20 dBm when the distance is 2 m or more.

[0071] Next, the control unit 41 transmits radio waves at the adjusted radio wave level for a predetermined time (for example, 2 seconds) (S20). Radio waves are transmitted at a frequency of, for example, 50 times per second. When the RFID tag 20 receives radio waves from the reader 40, it transmits a detection result (an "open signal OS" or a "close signal CS") to the reader 40. The detection results are cumulatively stored in the memory 47. While transmitting radio waves toward the RFID tag 20, the reader 40 simultaneously performs the following processing on the received detection results. Note that the detection results are not stored if the RFID tag 20 is not supplied with sufficient power and is therefore unable to transmit radio waves, or if the radio waves transmitted by the RFID tag 20 are too weak for the reader 40 to receive.

[0072] The control unit 41 counts the detection results stored in the memory 47 in the order in which they were received, and if one or more "open signals OS" are included (S30: YES), it determines that there is no continuity between the metal bodies M1 and M2. At the time of this determination, even if a predetermined time has not yet elapsed since the start of radio wave transmission, the continuity determination process is terminated. At this time, the control unit 41 notifies the user of the reader 40 of the determination result (no continuity) by displaying that there is no continuity on the display unit 45 or by sounding a sound.

[0073] If there is not one or more "open signals OS," that is, if no "open signal OS" has been received (S30: NO), the control unit 41 determines whether the accumulated and stored detection results include three or more "close signals CS" (S40).

[0074] If three or more "close signals CS" are included (S40: YES), the control unit 41 determines that there is electrical continuity between the metal bodies M1 and M2 and ends the continuity determination process even before the predetermined time has elapsed since the start of radio wave transmission. Then, the control unit 41 notifies the user of the determination result (continuity).

[0075] If the number of "close signals CS" is not three or more (S40: NO), the control unit 41 determines whether the level of the radio waves output by the reader 40 reaches 30 dBm (maximum output of the reader 40) (S50). If the level of the radio waves reaches 30 dBm (S50: YES), the continuity determination process is temporarily terminated. In this case, the continuity determination device 10 has not been able to determine whether or not there is continuity.

[0076] The control unit 41 displays, for example, "Please bring the reader closer to the RFID tag and measure again" on the display unit 45, and prompts the user to bring the reader 40 closer to the RFID tag 20 and start the continuity determination process again. By bringing the reader 40 and the RFID tag 20 closer, the power supplied to the RFID tag 20 increases, so there is a possibility that a determination result will be obtained in the continuity determination process again.

[0077] If the radio wave level has not yet reached 30 dBm (S50: NO), the control unit 41 instructs the transmission circuit 42 to increase the radio wave level by 1 dBm, and transmits radio waves at the increased radio wave level for a predetermined period of time (S20).

[0078] In this configuration, the radio wave level output by the reader 40 is automatically adjusted in accordance with the signal received by the reader 40 from the RFID tag 20, so the user does not need to adjust the radio wave level each time.

[0079] Furthermore, at the start of measurement, low-level radio waves are emitted toward the RFID tag 20, which reduces the amount of charge generated in the metal bodies M1 and M2, thereby suppressing the occurrence of errors caused by the generated charge (see Figures 7(c) and (d)).

[0080] If the level of the radio waves emitted by the reader 40 is low, less power is supplied to the RFID tag 20, and the level of the radio waves emitted from the RFID tag 20 to the reader 40 also becomes low. However, by the control unit 41 automatically adjusting the level of the radio waves repeatedly emitted from the reader 40 so that it gradually increases, the level of the radio waves emitted by the RFID tag 20 also increases, and eventually reaches a level at which the reader 40 can receive the radio waves. This makes it possible to more reliably determine the presence or absence of continuity while suppressing the occurrence of errors.

[0081] Furthermore, as described above, an error may occur in which the close signal CS is transmitted even though the RFID tag 20 is actually in the open state due to the electric charge generated in the metal bodies M1 and M2 (see FIG. 7(c)). Meanwhile, when the RFID tag 20 transmits the close signal CS or the open signal OS, electric charge is consumed.

[0082] In this embodiment, as shown in S40 of FIG. 8, the control unit 41 determines that there is continuity only when it receives the close signal CS three or more times. In other words, if the close signal CS is detected two or less times, it is not determined that there is continuity. In this way, the electric charge generated in the metal bodies M1 and M2 is consumed by the RFID tag 20 transmitting the close signal CS twice, so the close signal CS received by the reader 40 from the third time onwards is less likely to contain an error. This makes it possible to more accurately determine whether there is continuity by excluding the influence of the generated electric charge.

[0083] <Other embodiments> The present invention is not limited to the embodiments described above and illustrated in the drawings, and the following embodiments, for example, are also included within the technical scope of the present invention.

[0084] (1) In the above embodiment, electric charges are generated in the metal bodies M1 and M2 due to the radio waves emitted by the reader 40. However, electric charges are also generated in the conductor portion of the lead wire 27. To reduce the effect of the electric charges generated in the lead wire 27 on the detection results, the length of the lead wire 27 may be shortened. For example, if the length of the lead wire 27 is set to 50 cm or less, the effect on the detection results can be reduced.

[0085] (2) When a current flows through the lead wire 27, an electromotive force is generated, which may affect the detection of the IC chip module 23. By routing the lead wire 27 so that it forms a loop, the effect of the electromotive force can be offset, resulting in more accurate detection results.

[0086] (3) In the above embodiment, the metal body M1 is made of steel and the metal body M2 is made of magnesium alloy, but the present invention is also applicable to other metal materials. The metal bodies M1 and M2 may be made of a combination of metals that do not have a sacrificial corrosion protection effect.

[0087] (4) In the above embodiment, radio waves in the UHF band are used for communication between the reader 40 and the RFID tag 20, but radio waves in other frequency bands may be used for communication.

[0088] (5) The reader 40 may be provided with an interface unit for transmitting cumulatively stored test result data to another terminal (for example, a personal computer).

[0089] (6) In the above embodiment, the case where the close signal CS is received three or more times to determine that there is continuity is exemplified, but the number of times the close signal CS is received may be "multiple times" and is not limited to three. It may also be two or four or more times. [Explanation of symbols]

[0090] 10 Continuity determination device 20 RFID tags 21 Base board 21A 1st page 22 Antenna board 23 IC chip module 25A First detection terminal 25B Second detection terminal 33A 1st electrode 33B 2nd electrode

Claims

1. An RFID tag, A block-shaped base substrate that is long in one direction, an antenna substrate disposed on a first surface of the base substrate; an IC chip module located between the base substrate and the antenna substrate, the IC chip module having a first electrode and a second electrode on a surface facing the base substrate; a first detection terminal electrically connected to a first electrode of the IC chip module; a second detection terminal electrically connected to a second electrode of the IC chip module; the first detection terminal and the second detection terminal are electrically connected to a first metal body and a second metal body, respectively; The antenna substrate is an RFID tag that transmits the detection result of the presence or absence of electrical continuity between two metal bodies by radio waves.

2. 2. The RFID tag according to claim 1, the base substrate is made of an insulating material and has a second surface opposite to the first surface; the second surface is spaced apart from the first surface by a predetermined distance or more, The RFID tag is attached to the metal body with the second surface serving as an attachment surface.

3. 3. The RFID tag according to claim 1, a clip for holding the antenna substrate relative to the base substrate; An RFID tag in which the first detection terminal and the second detection terminal maintain contact with the first electrode and the second electrode due to the elastic force of the clip, thereby maintaining electrical connection with the electrodes.

4. The RFID tag according to any one of claims 1 to 3; a reader that reads the detection result from the RFID tag in a non-contact manner.

5. The continuity determination device according to claim 4, A continuity determining device, wherein a combination of metals having a sacrificial anticorrosion effect is connected to the first detection terminal and the second detection terminal, respectively.

6. The continuity determination device according to claim 4 or 5, The reader a reader-side antenna for transmitting and receiving radio waves to and from the RFID tag; a control unit; The RFID tag is a passive type that receives power from received radio waves, detects a continuity state, and transmits the detection result. The control unit automatically adjusts the level of the radio waves output to the RFID tag so that the reader antenna can receive the detection result transmitted by the RFID tag.

7. 7. The continuity determination device according to claim 6, The control unit increases the level of the radio waves to be output when the reader antenna cannot receive the detection result transmitted by the RFID tag.

8. The continuity determination device according to claim 7, the detection result is a close signal that is detected when there is electrical continuity between the first detection terminal and the second detection terminal, or an open signal that is detected when there is no electrical continuity between the first detection terminal and the second detection terminal, The control unit determines whether or not there is continuity based on the order and number of the received open signals and close signals.

9. 9. The continuity determination device according to claim 8, When the control unit receives the open signal one or more times before receiving the close signal a plurality of times, the control unit determines that the first detection terminal and the second detection terminal are not electrically connected to each other, When the close signal is received a plurality of times before the open signal is received one or more times, the continuity determination device determines that the first detection terminal and the second detection terminal are conductive.

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