JP2007304703A - Equipment monitoring apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an equipment monitoring apparatus which grasps status of equipment regularly in order to detect abnormalities of the equipment, has no complicatedness of signal line or power supply cabling and can be installed easily for existing equipment. <P>SOLUTION: Loop antennas 19a-19c are set up corresponding to physical quantity detectors 15a-15c respectively and perform power transfer from loop antennas 26a-26c of a repeater 10 according to change operation of a switch 25. Thereby, a measurement result from a sensor section 18 can be transmitted to a control section 40 through the repeater 10 without connecting with a signal line or a wire, etc. for supplying power to the physical quantity detector. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a monitoring device for physical quantities of equipment and, for example, to equipment monitoring equipment for monitoring the temperature of a terminal portion of a circuit breaker in a panel such as a switchboard or a control panel.

  Generally, in a terminal portion of a circuit breaker, the electric wire and the circuit breaker are fixed with screws and bolts. However, internal corrosion may occur due to poor enforcement, external environment, or the like, and the electrical resistance may increase at the connection portion with the electric wire in the terminal portion of the circuit breaker.

  In this respect, an increase in the electric resistance value at the connection portion with the electric wire causes abnormal heat generation due to the energizing current. Also, the circuit breaker is used beyond its switching performance, and abnormal heat generation may occur due to contact wear.

  As a result of abnormal heat generation at the connection part with the circuit breaker, the electric wire, etc., those burnouts may occur, and the equipment supplied with power by the circuit breaker may be damaged.

  Conventionally, in order to solve the problem of burning due to abnormal heat generation at the circuit breaker and the connection part with the electric wire etc., the inspector patrols and monitors the thermo-label attached to the terminal part of the circuit breaker and the electric wire. It was.

  In addition, when an abnormal temperature near the contact of the circuit breaker is detected and a warning is issued at a predetermined temperature or higher (for example, Patent Document 1), or when the temperature inside the circuit breaker is higher than a predetermined allowable level A method has been proposed in which an abnormal state is detected by an electronic circuit breaker (for example, Patent Document 2) that performs control so as to perform an opening operation regardless of the value of a load current that is energized and that issues an alarm.

  However, in order to constantly monitor the state of the circuit breaker, it is necessary for the inspector to go around the switchboard and check the thermo label attached to the circuit breaker and check the alarm of the circuit breaker. In addition, it was necessary to always have an inspector for this purpose.

Therefore, there is a strong demand for remote monitoring of abnormal states such as circuit breakers, and several equipment monitoring devices have been proposed (for example, Patent Document 3, Patent Document 4, and Patent Document 5).
Japanese Patent Laid-Open No. 5-56552 (2nd paragraph, 0007 line, FIG. 2) Japanese Patent Laying-Open No. 2003-223839 (line 5 0007, FIG. 1) JP 2004-153920 A (line 8 0036, FIG. 1) Japanese Patent Laying-Open No. 2002-83389 (6th paragraph, 0028 line, FIG. 7) JP-A-8-103022 (5th paragraph 0021-0029, FIG. 1)

  However, such an equipment monitoring device has a problem that it is difficult to adapt to existing equipment such as securing an installation space.

  In addition, a physical quantity detector that has a sensor at the measurement location and that has communication means such as infrared or wireless, and that monitors equipment with that communication means has a built-in battery to drive the physical quantity detector It is necessary to make it. Or it is necessary to supply the electric power for driving a physical quantity detector from an electric wire. However, since the terminal part of the circuit breaker becomes hot due to the energized current, if a physical quantity detector is attached to the terminal part of the circuit breaker, the battery performance deteriorates and the driving time of the physical quantity detector is shortened. was there.

  In addition, since it is necessary to attach a current transformer for power supply from the electric wire, when applied to a circuit breaker, the physical quantity detector connected to the electric wire that was interrupted at the time of circuit interruption cannot supply power. There was also. Moreover, in the power supply using an electric wire, there also existed a problem that wiring became complicated.

  On the other hand, in power transmission from the outside of a physical quantity detector represented by RFID (Radio Frequency IDentification), there is a problem that electromagnetic waves emitted from a reader are mixed into an electric wire in order to obtain information on tags attached over a wide range. . In addition, the short-range communication RFID has a problem that a plurality of measurement points cannot be measured.

  The present invention has been made to solve the above-described problems. In order to detect an abnormality in equipment, the state of the equipment is steadily grasped, and there is no complication of signal lines and power supply wiring. It aims at providing the equipment monitoring device which can be installed easily with respect to the existing equipment.

  The facility equipment monitoring apparatus according to the present invention is a facility equipment monitoring apparatus that monitors the physical quantity of a location to be measured of the equipment and is provided corresponding to each of the plurality of measurement locations of the equipment and supplied from the outside wirelessly. A plurality of detectors that operate according to the above, a repeater provided in the equipment, and a communication device that performs wireless communication with the repeater, and the detector outputs an output signal corresponding to a physical quantity to be detected. A sensor unit for generating, a transmission unit for transmitting an output signal, and a first loop antenna, receiving a signal transmitted from the repeater via the first loop antenna; The generated electromotive force is supplied to each circuit of the detector, and the signal output from the transmission unit is transmitted via the first loop antenna. The repeater corresponds to the first loop antenna of each detector. Established Selecting one of a plurality of second loop antennas for wireless communication with the corresponding first loop antenna and a plurality of second loop antennas in response to an instruction signal from the communication device And a transmission / reception unit that receives a signal from the detector via the selected second loop antenna and transmits the signal to the communication device, and determines the physical quantity of the measured location by the instruction signal. Select and monitor.

  According to the present invention, the signal is transmitted to the loop antenna of the physical quantity detector, and the physical quantity detector is operated by the electromotive force generated by the received signal. It can be easily installed on equipment.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and description thereof will not be repeated.

(Embodiment 1)
The equipment monitoring apparatus according to the first embodiment of the present invention detects a physical quantity of an arbitrary object to be measured from a plurality of objects to be measured in a plurality of equipment, and is a control computer that is a control unit. In addition to collecting the detected physical quantity and displaying the physical quantity, it has a function of outputting a warning or an alarm when the physical quantity exceeds a certain threshold. This will be specifically described below.

FIG. 1 is a network diagram of facility equipment monitoring apparatus 1 according to the first embodiment of the present invention.
Referring to FIG. 1, here, equipment devices 5a, 5b, and 5c are shown as examples of a plurality of equipment devices, and a plurality of objects to be measured corresponding to measurement locations are provided in each equipment device. It is assumed that In the following, a case will be mainly described in which the facility device 5a is selected from the plurality of facility devices 5a to 5c and the state of the device in the facility device 5a is monitored as an example.

  The equipment monitoring device 1 according to the first embodiment of the present invention includes a control unit 40 that controls the entire equipment with respect to a plurality of equipment 5a, 5b, and 5c, and wireless communication in response to an instruction from the control unit 40. A transmission / reception unit 35 for transmitting / receiving data signals is provided.

  The equipment 5a is provided with a plurality of objects 20 to be measured corresponding to the measurement locations, and a physical quantity detector for detecting the physical quantities of the objects 20 to be measured corresponding to the objects 20 to be measured. 15 is provided.

  In addition, the facility device 5 a is provided with a repeater 10 for performing wireless communication with each of the transmission / reception unit 35 and the physical quantity detector 15.

  The repeater 10 includes a transmission / reception unit 30 for performing transmission / reception of data signals by wireless communication between the transmission / reception unit 35 and the physical quantity detector 15, and a plurality of physical quantity detectors in response to an instruction from the transmission / reception unit 30. And a switch 25 for selecting at least one of them and obtaining a detection result of the selected physical quantity detector.

  The physical quantity detector 15 detects the physical quantity of the corresponding measurement target object according to the selection operation of the switch 25 and transmits the detection result to the repeater 10.

  On the network, the transmission / reception unit 35 connected to the control unit 40 and the repeater installed in each equipment 5a, 5b, 5c are connected wirelessly. And the repeater 10 provided in each equipment 5a-5c and the physical quantity detector 15 provided corresponding to each to-be-measured object 20 in corresponding equipment 5a, 5b, 5c connect by radio | wireless. Has been. In addition, in this example, although the control part 40 has shown the structure which controls the single transmission / reception part 35, it is not restricted to the structure which controls a single transmission / reception part especially, A transmission / reception part corresponding to equipment It is also possible to use a router, a switch, or the like to control a plurality of transmission / reception units provided corresponding to a plurality of facility devices.

  FIG. 2 is a schematic block diagram illustrating a configuration of facility equipment monitoring apparatus 1 according to the first embodiment of the present invention.

  Referring to FIG. 2, control unit 40 is installed in a management room or the like that remotely monitors equipment. The control unit 40 includes a display device 41 for displaying information on the physical quantity of the measurement target object 20 and the equipment 5a in which the measurement target object 20 exists, and an input device 42 that can be operated by an administrator. Although not shown, it is constituted by an external device 43 including an alarm device for outputting an alarm and a storage device for recording information. Note that these devices in the control unit 40 are in a cooperative relationship with each other, but an arrow indicating a signal flow is omitted because it is a general technical idea for those skilled in the art.

  The transmission / reception unit 35 receives a radio wave from the signal processing unit 37 and the repeater 10, a modulation / demodulation circuit 36 for performing wireless communication with the repeater 10, and transmits a radio wave to the repeater 10. Antenna 38. Here, the modulation / demodulation circuit 36 includes a digital circuit that performs digital modulation / demodulation and a high-frequency / analog circuit for transmission / reception. The other modulation circuit, demodulation circuit, and modulation / demodulation circuit are similarly composed of a digital circuit and a high-frequency / analog circuit.

  The repeater 10 includes the transmission / reception unit 30 and the switch 25 as described above. The transmission / reception unit 10 receives the radio wave from the transmission / reception unit 35 via the antenna 34 for performing wireless communication between the antenna 34 for receiving or transmitting the radio wave to the transmission / reception unit 35 and the transmission / reception unit 35. The radio wave signal is demodulated, modulated in order to transmit the data signal to the transmission / reception unit 35 and transmitted through the antenna 34, and the input data signal is subjected to signal processing and received. A signal processing unit 32 that detects data and outputs transmission data to the modulation / demodulation circuit 31 in order to transmit radio waves to the transmission / reception unit 35. Further, the signal processing unit 32 generates and outputs an instruction signal for executing the switching operation to the switch 25 based on the received data from the modulation / demodulation circuit 31 and performs wireless communication with the physical quantity detector 15. The data signal is output to the modem circuit 33. The modulation / demodulation circuit 33 modulates the data signal from the signal processing unit 32 and transmits the modulated data signal via a loop antenna, which will be described later, and receives and demodulates the radio wave transmitted from the physical quantity detector 15 by the loop antenna. Is output to the signal processing unit 32. The repeater 10 is driven by a battery such as a battery.

  The repeater 10 further includes loop antennas 26a to 26c provided corresponding to the plurality of physical quantity detectors 15a to 15c, respectively, and the plurality of loop antennas 26a to 26c according to the switching operation of the switch 25 in response to the instruction signal. Is selected.

  The equipment 5a includes physical quantity detectors 15a to 15c provided corresponding to the plurality of objects to be measured 20a to 20c, respectively. Each of the physical quantity detectors 15a to 15c has the same configuration. Here, the configuration of the physical quantity detector 15a will be described as a representative. The physical quantity detector 15a includes a loop antenna 19a provided corresponding to the loop antenna 26a, a power supply circuit 70, and a main circuit unit 75.

  The main circuit unit 75 includes a modulation / demodulation circuit 16, a signal processing circuit 17, and a sensor unit 18. Specific operations of the physical quantity detector 15a will be described later.

  FIG. 3 is a diagram illustrating an outline of a circuit breaker that is a facility device according to the first embodiment of the present invention. Here, the circuit breaker 50 is cited as an example of equipment and the configuration in which physical quantity detectors are provided at a plurality of measurement locations of the circuit breaker will be described.

  Referring to FIG. 3, three electric wires 45 are fixed to the circuit breaker 50 by screws 46 at the terminal portions. In the lower terminal portion of the circuit breaker 50, the electric wire 45 is screwed by the screw 46 as in the upper terminal portion. However, in the configuration according to the first embodiment of the present invention, the lower terminal portion is used. The case where the repeater 10 is provided so as to cover the top is shown. Here, as an example, a configuration in which the repeater 10 is installed in the region of the lower terminal portion of the circuit breaker 50 is shown as an example, but a configuration in which the repeater 10 is provided in the upper terminal portion of the circuit breaker 50 is adopted. Is of course possible.

  FIG. 4 is a diagram illustrating the structure of the repeater 10 provided so as to be covered on the lower terminal portion with respect to the circuit breaker 50 shown in FIG. 3.

  Referring to FIG. 4, three electric wires 45 are fixed to the circuit breaker 50 by screws 46 at the terminal portions as described in FIG. The physical quantity detectors 15 a to 15 c are provided on the tops of the three screws 46, respectively. A spacer 47 that is a holding member is provided between the physical quantity detectors 15 a to 15 c and the repeater 10. The spacer 47 holds the physical quantity detectors 15 a to 15 c and the repeater 10 and also has a fixing function for the circuit breaker 50. Furthermore, the spacer 47 is also used as a terminal cover for the circuit breaker.

FIG. 5 is a diagram for explaining the relationship between the physical quantity detectors 15 a to 15 c and the repeater 10.
Referring to FIG. 5, the repeater 10 includes a printed circuit board 60 on which circuit wiring connections and the like are formed. Three loop antennas 26 a to 26 c are formed on one surface of the printed circuit board 60, and the other The electronic parts constituting the transmission / reception unit 30 and the switch 25 are mounted on the surface.

  The physical quantity detector 15a includes a printed circuit board 61 on which circuit wiring connections and the like are formed. A loop antenna 19a is formed on one surface of the printed circuit board 61 facing the printed circuit board 60, and the other surface is formed. Electronic components constituting the power supply circuit 70 and the main circuit unit 75 are mounted. The same applies to the other physical quantity detection circuits 15b and 15c. The physical quantity detection circuit 15b is provided with a loop antenna 19b facing the loop antenna 26b. Regarding the physical quantity detection circuit 15c, a loop antenna 19c is provided so as to face the loop antenna 26c. Here, the case where the electronic components of the repeater 10 and the physical detector 15a are mounted on the surface different from the loop antennas 26a and 19a has been described. However, the present invention is not limited to this, and can be mounted on the same surface. It is.

  The loop antennas 19a to 19c of the physical quantity detectors 15a to 15c are disposed so as to face the loop antennas 26a to 26c of the repeater 10 via a spacer 47 (not shown).

  FIG. 6 is a diagram illustrating the antenna shapes of the repeater 10 and the physical quantity detection circuits 15a to 15c.

  Referring to FIG. 6A, here, loop antennas 26 a to 26 c provided respectively corresponding to physical quantity detectors in printed circuit board 60 of repeater 10 are shown. 6B, here, loop antennas 19a to 19c provided on the printed circuit board 61 of each of the physical quantity detection circuits 15a to 15c are shown.

  Here, the loop antennas 26a to 26c and the loop antennas 19a to 19c have a line-symmetric shape with each other, and are set to have the same size and shape and the same number of turns. When the loop antennas 26a to 26c provided on the printed circuit board 60 of the repeater 10 and the loop antennas 19a to 19c provided on the printed circuit board 61 of the physical quantity detectors 15a to 15c are opposed to each other, a rectangular antenna is used. The sides are set to face each other and the winding direction is set to be opposite to each other. In FIG. 6, a square loop antenna 26a having a radius r0 centered on the center O1 and a square loop antenna 19a having a radius r1 (= r0) centered on the center O2 are shown as an example.

  With this configuration, when the loop antennas are opposed to each other, the sides of the rectangular antennas face each other, so that the coupling coefficient between the loop antennas can be increased. Here, the shape of the loop antenna is a quadrangular shape, but it may be a spiral circular shape.

  The distance between the loop antennas 19a and 26a between the repeater 10 and the physical quantity detector 6 provided by the spacer 47 is set to a value not less than 1/3 and not more than the diameter of the loop antennas 19a and 26a. For example, it can be set to be larger than the radius of the loop antennas 19a and 26a. Note that the distance l between adjacent loop antennas is set to be equal to or greater than the radius of the loop antenna.

  The sensor unit 18 of the physical quantity detector 15a is provided on the side close to the terminal part of the circuit breaker 50, and is provided on the side close to the screw 46 of the terminal part of the circuit breaker 50.

  Further, the loop antennas 26a to 26c and the loop antennas 19a to 19c are provided in parallel to each other, and are arranged so that the normal line of the loop antenna surface is orthogonal to the electric wire connected to the circuit breaker.

Hereinafter, the operation of the equipment monitoring apparatus 1 according to the first embodiment of the present invention will be described.
Referring again to FIG. 2, when a command related to detection of a physical quantity of an arbitrary measurement target object 20 in any facility equipment 5 a to 5 c is issued from the control unit 40, a data signal including the command is transmitted to the transmission / reception unit 35. It is done. Here, as an example, a case will be described in which the physical quantity of the measurement target 20a corresponding to the equipment 5a is detected.

  In the transmission / reception unit 35, the signal output from the control unit 40 is subjected to signal processing by the signal processing unit 37 and output to the modulation / demodulation circuit 36. The modem circuit 36 modulates the data signal and wirelessly transmits it using the antenna 38. The radio used in the transmission / reception unit 35 can be a widely used wireless communication means such as a 5 GHz band or a 2.4 GHz band wireless LAN or Bluetooth. When a general communication standard such as a wireless LAN is used, there is usually a communication distance of about 10 m, and a signal can be transmitted to a repeater existing within the communication distance.

  As described above, the modulation / demodulation circuit 36 is composed of a digital circuit and a high frequency / analog circuit. For example, in the case of a 5 GHz band wireless LAN, the modulation / demodulation circuit 36 performs digital modulation / demodulation such as OFDM, and the carrier frequency in the 5 GHz band by the high frequency / analog circuit. Thus, it has a function of transmitting and receiving signals.

  The data signal transmitted by radio transmission from the transmission / reception unit 35 is transmitted to the repeaters provided in the plurality of facility devices 5a to 5c via the antenna.

  The repeater 10 receives the modulated data signal transmitted from the transmission / reception unit 35 via the antenna 34, and demodulates the signal by the modem circuit 31. The demodulated data signal is output to the signal processing unit 32 to execute signal processing. In this signal processing, when it is determined that the measurement target object 20 designated as a detection target does not exist in its own equipment, that is, when it is determined that the equipment is not a command target, No further signal processing is performed, and a standby state is entered. For example, if the data signal transmitted from the transmitter / receiver 35 includes the data indicating the ID number of the repeater indicating the instruction target, the data is transmitted with the ID number held in advance in each repeater. It is possible to determine whether or not they match by executing a match determination operation with the ID number in the data signal.

  On the other hand, in the repeater 10 installed in the equipment in which the specified object 20 to be measured exists, the signal processing unit 32 outputs a data signal to be transmitted to the physical quantity detector to the modulation / demodulation circuit 33 and performs switching. An instruction signal for executing the switching operation is output to the device 25.

  The switch 25 selects any one of the plurality of loop antennas 26 a to 26 c in response to the instruction signal from the signal processing unit 32. In this example, it is provided corresponding to the physical quantity detector 15a corresponding to the desired measurement object 20a among the physical quantity detectors 15a to 15c provided corresponding to the plurality of measurement objects 20a to 20c, respectively. It is assumed that the loop antenna 26a is selected.

  Then, a signal superimposed on the carrier frequency for power transmission is transmitted only from the loop antenna 26a to the physical quantity detector 15a. The transmission signal includes a trigger signal that signals the start of detection to the physical quantity detector 15a, is modulated by the digital circuit of the modulation / demodulation circuit unit of the modulation / demodulation circuit 33, and is carrier frequency by the mixer of the high-frequency circuit of the modulation circuit unit. Is superimposed on. Thereafter, a high frequency current is generated by the driving amplifier of the high frequency circuit of the modulation circuit unit, and a current including a signal flows through the loop antenna 26a of the repeater 10.

  Power transmission from the repeater 10 to the physical quantity detector 15a is performed using the loop antenna 26a of the repeater 10 and the loop antenna 19a of the physical quantity detector 15a. When a current corresponding to the signal flows through the loop antenna 26a of the repeater 10, a magnetic field is formed by the current.

  On the other hand, in the loop antenna 19a of the physical quantity detector 15a, a current flows in a direction to suppress the generated magnetic field. An electromotive force is generated by the induced current flowing through the loop antenna 19a, and is converted into a constant voltage by rectifying and smoothing it in the power supply circuit 70, and the physical quantity detector 15a can be operated using the converted voltage. .

  FIG. 7 is an equivalent circuit diagram of the power supply circuit 70 connected to the loop antenna 19a of the physical quantity detector 15a.

  Referring to FIG. 7, here, the inductances of the loop antennas 26a and 19a of the repeater 10 and the physical quantity detector 15a are L1 and L2, respectively. It is assumed that the two inductances L1 and L2 are coupled with a coupling coefficient k or a mutual inductance. Further, the resistance component due to the loop antenna 19a and the lead wiring of the physical quantity detector 15a is R2. The power supply circuit 70 has a resonance circuit including a load resistor RL and a resonance capacitor C2. By connecting the loop antenna 19a and the power supply circuit 70 having a resonance circuit, a high induced electromotive force u2 can be obtained even at a low frequency. Then, it is converted into a constant voltage by a rectifier circuit and a smoothing circuit (not shown) and supplied to the main circuit unit 75.

  FIG. 8 is a diagram for explaining the relationship between the frequency and the induced electromotive force in the equivalent circuit diagram shown in FIG.

  8 indicates the electromotive force induced on the loop antenna 19a of the physical quantity detector 15a facing the loop antenna 26a of the repeater 10. Moreover, the symbol Δ in the figure indicates the electromotive force induced in the loop antenna 19b of the adjacent physical quantity detector 15b. This loop antenna is formed of copper wiring on a glass epoxy printed circuit board (FR-4) and designed to have an outer diameter of 14 mm, a line width of 0.3 mm, a number of turns of 3, and a distance between lines of 0.5 mm. . The distance between the loop antennas is designed to be 10 mm, and the distance between the loop antennas of the physical detector 19b adjacent to the physical detector 19a is designed to be 12 mm.

  Here, the frequency dependence characteristic of the maximum amplitude of the induced electromotive force obtained by adjusting the resonance capacitor C2 so as to resonate at each frequency is shown, and the maximum amplitude of the induced electromotive force is 5 V at a frequency of 30 MHz. Is obtained.

  As shown in FIG. 8, the voltage induced by the loop antenna 19a of the physical quantity detector 15a increases with frequency, but at 50 MHz or more, the resistance component of the loop antenna 19a increases due to the skin effect, and the induced electromotive force decreases. The voltage induced in the loop antenna 19b of the adjacent physical quantity detector 15b has the same frequency dependency, but is lower than the voltage induced in the loop antenna 19a of the corresponding physical detector 15a. For example, if the electronic components constituting the physical quantity detector 15a operate at 5V, a signal having a frequency of 30 MHz or higher is applied to the loop antenna 26 of the repeater 10, thereby causing the loop of the physical quantity detector 15a corresponding to this loop antenna. An induced voltage of 5 V or more can be generated in the antenna 19a. The physical quantity detector 15a can be operated by rectifying and smoothing in the power supply circuit 70. On the other hand, since the loop antenna 20 of the adjacent physical quantity detector 15b can induce only a voltage of 2 V or less, the adjacent physical quantity detector 15b cannot be operated.

  When a booster circuit is incorporated in the physical quantity detector 15a, the voltage excited by the loop antenna 19a of the physical quantity detector 15a is set to a voltage that slightly exceeds the threshold value of the transistor, for example, about 1V. It is also possible to adjust. In this case, since the voltage excited by the loop antenna of the adjacent physical quantity detector 15b is about 0.3 V or less, it is difficult to switch the transistor in the adjacent physical quantity detector 15b even when boosted.

  In addition, as described above, the induced voltage obtained by the loop antenna increases as the frequency increases, but decreases due to the skin effect above a certain frequency.

  For example, although the self-resonant frequency of the loop antenna used in FIG. 8 is 300 MHz or more, the resistance component of the antenna increases due to the skin effect and the excitation voltage decreases at a frequency of 1/3 of the self-resonant frequency, that is, 100 MHz. . In the frequency band of 1/3 or more of the self-resonance frequency, the reduction of the excitation voltage is further increased. Therefore, it is desirable that the frequency used for power transmission and communication between the repeater 10 and the physical quantity detector 15a be in the range of 1/3 or less of the self-resonant frequency of the loop antenna. It is further desirable to use a frequency band of 1/6 or less.

  Referring to FIG. 2 again, the main circuit unit 75 of the physical quantity detector 15a receives power supply from the power supply circuit 70 connected to the loop antenna 19a and operates with the power.

In the main circuit unit 75, the sensor unit 18 detects the physical quantity of the measurement target 20a.
Specifically, as described with reference to FIG. 4, the physical quantity detectors 15 a to 15 c are installed on the upper part of the screw 46 for fixing the electric wire 45 at the terminal portion attached to the circuit breaker 50, and the sensor unit. 18 measures the temperature around the terminal portion. In addition, the sensor part 18 shall be comprised by the diode which can be formed on a silicon substrate as an example. Then, the current flowing through the diode of the sensor unit 18 is converted into a binarized signal (digital signal) by the signal processing circuit 17. As an example, the signal processing circuit 17 includes a so-called sigma-delta modulator including a switch, a differentiator, and an integrator, and a flip-flop circuit, and generates a bit stream of a digital signal. The signal processing circuit 17 may be provided with an ADC (analog-digital conversion) circuit to obtain a digital output.

  Then, the signal processed by the signal processing circuit 17 is output to the modulation / demodulation circuit 16, and the signal modulated by the modulation / demodulation circuit 16 is transmitted to the loop antenna 19a and transmitted to the repeater 10. Specifically, a signal including the physical quantity is superimposed on the carrier frequency and transmitted from the loop antenna 19a to the loop antenna 26a.

  The signal processing circuit 17 may be configured to temporarily store the result detected by the sensor unit 18 using a register or the like.

  On the repeater 10 side, the received signal transmitted from the loop antenna 19a is input to the modem circuit 33 by the switch 25 connected to the loop antenna 26a. The modem circuit 33 demodulates the input received signal and outputs it to the signal processing unit 32. The signal processing unit 32 performs signal processing on the signal demodulated by the modulation / demodulation circuit 33, and this time, a data signal including a physical quantity obtained as a result of signal processing is transmitted to the transmission / reception unit 35. 31 is output. The modem circuit 31 modulates the data signal including the physical quantity output from the signal processing circuit 32 and transmits the data signal to the transmission / reception unit 35 via the antenna 34.

  Here, the case where the physical quantity detected by the physical quantity detector 15a provided corresponding to the object 20a to be measured is transmitted to the transmission / reception unit 35 has been described. For example, an external storage device (not shown) is connected to the repeater 10. The physical quantity of the measurement target 20a detected by the physical quantity detector 15a and the information specifying the measurement target 20a are temporarily stored, and then another information is set according to the switching operation by the switch 25. It is also possible to select the physical quantity detector 15b or 15c and operate it in the same manner as the physical quantity detector 15a to store the physical quantities of the corresponding measured objects 20b and 20c in the external storage device. And the physical quantity detected from each of all the measurement objects included in the equipment 5a, for example, the measurement objects 20a to 20c, and the information for specifying the measurement objects 20a to 20c, for example, the position information and the number are again displayed. It is also possible to transmit data collectively from the antenna 34 of the repeater 10 to the transmitting / receiving unit 35 using the signal processing unit 32 and the modulation / demodulation circuit 31 by reading from an external storage device or the like.

  In addition, although the sensor part 18 demonstrated the case where the temperature around a terminal part was measured here, it is not restricted to this, For example, it may detect the housing | casing temperature of the circuit breaker in which the repeater is installed. Is possible. Also, install some of the physical quantity detectors to measure the temperature around the terminal of the circuit breaker, and install the remaining physical quantity detectors in place to detect the circuit housing temperature. Thus, it is also possible to transmit the information on the case temperature of the circuit breaker to the control unit 40 via the transmission / reception unit 35.

  The transmission / reception unit 35 demodulates the signal transmitted from the repeater 10 received by the modem 38 by the modulation / demodulation circuit 36, and outputs the demodulated signal to the control unit 40 after the signal processing by the signal processing unit 37.

  Based on the signal processing result by the signal processing unit 37, the control unit 40 displays information such as a physical quantity on the display device 41 and stores data in the external device 43. Further, when the physical quantity of the object 20 to be measured exceeds a certain threshold value, for example, it is possible to notify an abnormality of the equipment by operating a connected alarm device or the like.

  Here, the physical quantity detectors 15 a to 15 c installed at the terminal portions of the circuit breaker 50 described with reference to FIG. Generally, since the performance of a battery deteriorates at 80 ° C. or higher, it is difficult to incorporate the battery in the physical quantity detectors 15a to 15c. In addition, the small circuit breaker 50 may not be able to secure a space in which the battery is built. Furthermore, if the wiring is drawn into the physical quantity detectors 15a to 15c for supplying power from the electric wire 45, the wiring becomes complicated, and a defect is likely to occur during enforcement or maintenance.

  Therefore, the equipment monitoring apparatus according to the first embodiment of the present invention executes the above-described power transmission from the repeater 10 by providing the loop antennas 19a to 19c corresponding to the physical quantity detectors 15a to 15c, respectively, as described above. By doing so, the physical quantity of the desired location of the existing equipment 5a can be measured while eliminating the complexity of routing signal lines and wires. And when the physical quantity of the measurement object 20 exceeds a certain threshold value, it becomes possible to notify the abnormality of the equipment by interlocking with an alarm device or the like. Since the casing of the circuit breaker 50 has a lower temperature than the terminal portion, the repeater 10 can be driven by a battery such as a battery.

  In addition, the repeater 10 includes the switch 25 so that only the physical quantity detector 15 provided corresponding to the arbitrary measurement target object 20 can be operated, and the physical quantity of the measurement target object 20 can be changed. It becomes possible to detect. As a result, the state of the measurement object 20 can be constantly monitored, and an abnormality of the equipment can be detected. If the switch 25 is not provided and the repeater 10 tries to transmit / receive a signal with one loop antenna, the physical quantity detector 15 is operated by transmitting a signal to all the physical quantity detectors 15. There is a need. When a signal including a signal for selecting an arbitrary physical quantity detector 15 is transmitted in the signal, the other physical quantity detectors wait while returning a data signal detected from the actually selected physical quantity detector 15. There is a need. Therefore, the power consumption of the repeater 10 becomes larger than that in the present embodiment. In particular, when the sensor unit 18 uses a resistance type sensor, the current consumption during standby is further increased.

  In addition, when the repeater 10 performs transmission / reception with one loop antenna, the loop antenna of the physical quantity detector 15 cannot be covered unless the size of the loop antenna is increased. There is a possibility that the resonance frequency is lowered and the frequency band to be used is lowered. When the frequency is low, the excited voltage is also small, and it may be difficult to obtain a desired voltage.

  Therefore, as in the configuration of the present application, a switching device is built in, and a loop antenna having the same size and shape as the loop antenna provided in the physical quantity detector 15 is provided on the repeater side, so that an arbitrary measurement point can be obtained. Is effective from the viewpoint of power consumption and frequency.

  In addition, as described above, the loop antenna of the repeater 10 and the loop antenna of the physical quantity detector 15 have the same size, the same shape, and the reversely wound antenna shape. The coefficient can be increased. As a result, the induced current flowing through the antenna can be increased. Even if the current of the loop antenna of the repeater 10 is small or the transmission output is small, the physical quantity detector 15 can induce a large electromotive force. Therefore, when power is transmitted from the repeater 10 to the physical quantity detection circuit 15, the current flowing through the loop antenna 26 of the repeater 10 can be reduced, and the power consumption of the repeater 10 can be further reduced.

  In addition, as described above, the distance between the loop antenna of the physical quantity detector 15a and the loop antenna of the adjacent physical quantity detector 15b is more than the radius of the loop antenna, so that the electromotive force in the loop antenna of the adjacent physical quantity detector is operated as a circuit. The voltage can be lower than the voltage, and only the desired physical quantity detector can be operated.

  Furthermore, the maximum value of the voltage excited by the physical quantity detector is obtained by setting the frequency used for power transmission and communication between the repeater 10 and the physical quantity detector 15 to 1/3 or less of the self-resonance frequency of the antenna. Can do.

  Since the repeater 10 and the physical quantity detector 15a are fixed by the spacer 47, the position of the loop antenna is determined by the processing accuracy of the spacer 47 and the printed boards 60 and 61. Since the spacer 47, the repeater 10, and the physical quantity detector 15a are integrated, the position of the antenna can be prevented from shifting during attachment and attachment / detachment during maintenance, and variations in antenna position accuracy can be reduced. At the same time, it is possible to prevent mounting defects during maintenance and enforcement.

  Further, by integrating the repeater 10 and the physical quantity detector 15a by the spacer 47, the influence of the unevenness of the connecting portion such as a screw or a bolt is prevented, and the parallelism of the loop antenna of the repeater 10 and the physical quantity detector 15a is increased. Therefore, communication failure can be reduced.

  Furthermore, the loop antennas 26a to 26c and the loop antennas 19a to 19c provided via the spacer 47 are arranged in parallel to each other, and the normal line of the loop antenna surface is orthogonal to the electric wire connected to the circuit breaker. By doing so, the magnetic field generated between the repeater 10 and the loop antenna of the physical quantity detector 15a is kept almost orthogonal to the magnetic field generated by the electric current of the electric wire, so that communication is performed between the repeater 10 and the physical quantity detector 15a. Even if it is, the electromagnetic wave of the communication is not mixed into the electric wire. Therefore, it is possible to prevent the signal from being mixed as noise into other equipment connected to the circuit breaker.

  Further, since the circuit breaker 50 handles a voltage of 100 V or higher, a gap is provided between the screw 46 and the sensor unit 18 of the physical quantity detector 15 for insulation. That is, a space is provided in order to prevent a circuit from being destroyed by contact of a conductor such as a high voltage screw 46 with the exposed terminal portion of the physical quantity detector 15. In addition, since the repeater 10 is held by the spacer 47, even if the physical quantity detection circuit 15 is damaged due to the influence of the ground fault current, since the space is provided by the spacer 47, damage to the repeater 10 can be prevented.

  In the first embodiment of the present invention, the temperature measurement of the terminal portion of the circuit breaker 50 is described as an example of the equipment, but the invention is not limited to this, and the invention is applicable to other equipment. Further, it is naturally possible to perform temperature measurement not only on the terminal portion but also on other optimum locations.

(Embodiment 2)
The equipment monitoring apparatus according to the second embodiment of the present invention detects a physical quantity of an arbitrary object to be measured from a plurality of objects to be measured in a plurality of equipment as in the first embodiment. The management computer that is the control unit has a function of collecting the detected physical quantity, displaying the physical quantity, and outputting a warning or an alarm when the physical quantity exceeds a certain threshold. This will be specifically described below.

  FIG. 9 is a schematic block diagram illustrating the configuration of the equipment monitoring device according to the second embodiment of the present invention.

  Referring to FIG. 9, the equipment monitoring device according to the second embodiment of the present invention replaces repeater 10 with repeater 10 # and detects a physical quantity as compared with the equipment monitoring device described in FIG. The difference is that the device 15 is replaced with a physical quantity detector 15 #. Specifically, in this example, the repeater 10 # is different from the repeater 10 in that the transmission / reception unit 30 is replaced with the transmission / reception unit 30 #. The transmission / reception unit 30 # is different from the transmission / reception unit 30 in that the modulation / demodulation circuit 33 is replaced with a demodulation circuit 33 #. The physical quantity detector 15 # has a configuration in which the physical quantity detectors 15a to 15c are replaced with physical detectors 15a # to 15c #. Also, the physical quantity detector 15 # differs from the physical quantity detector 15 in that the modulation / demodulation circuit 16 is replaced with a modulation circuit 16 #. Since the other points are the same, detailed description thereof will not be repeated.

FIG. 10 is a diagram illustrating physical quantity detector 15 # according to the second embodiment of the present invention.
Here, the physical quantity detector 15a # will be described as an example.

  Referring to FIG. 10, physical quantity detector 15a # according to the second embodiment of the present invention includes loop antenna 19, power supply circuit 70, and main circuit unit 75 #. Main circuit unit 75 # includes a modulation circuit 16 #, a timing circuit 72, an oscillation circuit 71, a storage device 73, a signal processing circuit 17, and a sensor unit 18.

  Hereinafter, the operation of the equipment monitoring apparatus according to the second embodiment of the present invention will be described using FIG. 9 and FIG.

  As described above, when a command related to detection of a physical quantity of an arbitrary measurement target object 20 in any equipment 5a to 5c is issued from the control unit 40, a data signal including the command is sent to the transmission / reception unit 35. Here, as an example, it is assumed that the physical quantity of the measurement target object 20a corresponding to the equipment 5a is detected.

  The transmission / reception unit 35 modulates the data signal by the signal processing unit 37 and the modulation / demodulation circuit 36 and wirelessly transmits the data signal using the antenna 38. The data signal transmitted wirelessly from the transmission / reception unit 35 reaches the repeater 10 # provided for each of the plurality of facility devices.

  The repeater 10 # receives the data signal from the transmission / reception unit 35 via the antenna 34, and demodulates the signal received by the modem circuit 31. Then, the demodulated data signal is output to the signal processing unit 32 to execute signal processing. In this signal processing, as described above, it is determined whether or not the measurement target object 20 designated as a detection target exists in its own equipment. In the repeater 10 # installed in the facility device where the specified object 20 to be measured exists, the signal processing unit 32 outputs an instruction signal to the switch 25.

  As described above, the switch 25 selects any one of the plurality of loop antennas 26 a to 26 c in response to the instruction signal from the signal processing unit 32. In this example, it is provided corresponding to the physical quantity detector 15a corresponding to the desired measurement object 20a among the physical quantity detectors 15a to 15c provided corresponding to the plurality of measurement objects 20a to 20c, respectively. It is assumed that the loop antenna 26a is selected.

  Then, the carrier frequency for power transmission is transmitted only from the loop antenna 26a to the physical quantity detector 15a.

  In the configuration of the first embodiment, the trigger signal is superimposed on the physical quantity detector 15a with the carrier frequency for power transmission via the loop antenna 26a from the signal modulated from the modulation / demodulation circuit 33 of the transmission / reception unit 30. Although transmitted / received, transmission / reception unit 30 # according to the second embodiment of the present invention does not transmit a data signal or the like to physical quantity detector 15a but only performs power transmission through loop antenna 26a.

  Power supply circuit 70 generates a constant DC voltage necessary for operating main circuit portion 75 # as described above. For example, when the voltage obtained by the resonance circuit is not less than the threshold voltage of the transistor and not more than the allowable voltage of the circuit, a boost circuit is provided to generate a voltage for boosting and operating the main circuit unit 75 #. It is also possible to do.

  Then, the voltage generated by the power supply circuit 70 is supplied to the main circuit unit 75 #, and a clock signal is generated by the oscillation circuit 71 shown in FIG. The timing circuit 72 generates a clock signal at a desired timing using the clock signal output from the oscillation circuit 71 and outputs the clock signal to other circuits. This clock signal is output to the signal processing circuit 17, the storage device 73, and the modulation circuit 16 # as an operation timing signal of the main circuit unit 75 #.

  In the same manner as described above, the sensor unit 18 measures the temperature, and the signal processing unit 17 can obtain a digital output. In this example, this output is temporarily stored in the storage device 73 constituted by a register or the like. Then, in response to a certain timing, the data signal stored in the storage device 73 is modulated by the modulation circuit 16 # and transmitted to the repeater 10 # via the loop antenna 19a.

  Specifically, the data stored in the storage device 73 is coded by the digital circuit included in the modulation circuit 16 #, and the high frequency / analog circuit included in the modulation circuit 16 # generates a signal including data at the carrier frequency. Superimpose and transmit the data signal to repeater 10 #.

  On the repeater 10 # side in FIG. 9, a transmission signal from the physical quantity detector 5a # is received via the loop antenna 26a and the switch 25. The received data signal is input to demodulation circuit 33 #. Then, in the demodulation circuit 33 #, the transmission signal from the physical quantity detector 5a # is demodulated and output to the signal processing unit 32. Then, the signal is modulated by the modulation / demodulation circuit 31 based on the same signal processing as described above, and transmitted from the antenna 34 of the repeater 10 # to the transmission / reception unit 35.

  In the transmission / reception unit 35, signal processing is performed according to the same method as described above, and a data signal is output to the control unit 40.

  The control unit 40 displays information such as physical quantities on the display device 41 and stores data in the external device 43. When the physical quantity of the object to be measured exceeds a certain threshold value, it is possible to notify the abnormality of the equipment by interlocking with an alarm or the like, and the same effect as in the first embodiment can be obtained. .

  Further, in the configuration according to the second embodiment of the present invention, in relay unit 10 # and physical quantity detector 15a #, etc., only the demodulation circuit and the modulation circuit are provided, and the modulation circuit and the demodulation circuit are not provided. It is. That is, in the configuration according to the first embodiment, a data signal is transmitted from the repeater 10 side to the physical quantity detector 15a, and a data signal is transmitted from the physical quantity detector 15a to the repeater 10 side. Although the configuration according to the second embodiment is a possible configuration, since the data signal is transmitted only from the physical quantity detector 15a to the repeater 10 side, the demodulation circuit and the modulation circuit are formed. Since electronic components can be deleted, the circuit scale can be reduced as compared with the configuration according to the first embodiment.

  Further, as described above, it is not necessary to have a function of modulating a signal to be transmitted to the physical quantity detector, and similarly, the physical quantity detector need not have a function of demodulating a signal from the repeater. Therefore, the power consumption of the repeater and the physical quantity detector can be reduced.

  Further, by reducing the number of parts of the physical quantity detector, it is possible to reduce the layout area of the internal circuit included in the main circuit unit 75 # so as to be accommodated in one chip. It is also possible to reduce the number of parts.

(Embodiment 3)
The equipment monitoring apparatus according to Embodiment 3 of the present invention detects a physical quantity of an arbitrary object to be measured from among a plurality of objects to be measured in a plurality of equipment as in Embodiment 1. The management computer that is the control unit has a function of collecting the detected physical quantity, displaying the physical quantity, and outputting a warning or an alarm when the physical quantity exceeds a certain threshold. This will be specifically described below.

  FIG. 11 is a schematic block diagram illustrating the configuration of the equipment monitoring device according to the third embodiment of the present invention.

  Referring to FIG. 11, the equipment monitoring device according to the third embodiment of the present invention is different from equipment equipment monitoring described in FIG. 2 in that repeater 10 is replaced with repeater 10 # a. . Specifically, in this example, the repeater 10 # a replaces the transmission / reception unit 30 with the transmission / reception unit 30 # a and is provided with a switch 25 # and modulation / demodulation circuits 33a to 33c as compared with the repeater 10. The point is different. The transmission / reception unit 30 # has a configuration in which the modulation / demodulation circuit 33 is excluded from the transmission / reception unit 30, and the other points are the same.

  The repeater 10 according to the first embodiment selects any one of the loop antennas 26a to 26c by the switching operation of the switch 25 in response to the switching instruction from the signal processing unit 32, and the selected loop antenna However, in the repeater 10 # a according to the third embodiment of the present invention, the arrangement of the switch and the modulation / demodulation circuit is switched. In other words, modulation / demodulation circuits 33a-33c are provided corresponding to the loop antennas 26a-26c, respectively, and among the plurality of modulation / demodulation circuits 33a-33c by the switching operation of the switch 25 # in response to the switching instruction from the signal processing unit 32. Is selected and connected to the signal processing unit 32. Accordingly, the selected modulation / demodulation circuit 33 receives the signal input from the signal processing unit 32, modulates it, and transmits it to the corresponding loop antenna 26. Subsequent operations are the same as those in the first embodiment. Conversely, the signal transmitted from the loop antenna 19 is received via the loop antenna 26 and output to the corresponding modulation / demodulation circuit 33. As a result, the signal is demodulated in the corresponding modem circuit 33 and output to the signal processing unit 32 via the switch 25 #. The operation is the same as that described in the configuration according to the first embodiment.

  In this configuration, the number of modulation / demodulation circuits is increased as compared with the configuration of the first embodiment, but the distance between the modulation / demodulation circuit and the loop antenna can be shortened. In this respect, if the inductance of the wiring increases, the frequency used to perform communication between the repeater and the physical quantity detector may be affected. Since it can be shortened, the influence of the inductance of the wiring can be reduced. Further, although the signal is deteriorated due to transmission loss caused by the resistance of the wiring, since the length of the wiring can be shortened, the deterioration of the signal can be reduced. Moreover, the efficiency of power transmission can be increased by reducing transmission loss.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

It is a network diagram of the equipment monitoring device 1 according to Embodiment 1 of the present invention. It is a schematic block diagram explaining the structure of the equipment monitoring device 1 according to Embodiment 1 of the present invention. It is a figure explaining the outline of the circuit breaker which is the installation apparatus according to Embodiment 1 of this invention. It is a figure explaining the structure of the repeater 10 provided so that it might cover over the lower terminal part regarding the circuit breaker 50 shown in FIG. It is a figure explaining the relationship between the physical quantity detectors 15a-15c and the repeater 10. FIG. It is a figure explaining the antenna shape of the repeater 10 and the physical quantity detection circuits 15a-15c. It is an equivalent circuit diagram with the power supply circuit 70 connected with the loop antenna 19a of the physical quantity detector 15a. It is a figure explaining the relationship between the frequency and induced electromotive force in the equivalent circuit diagram shown by FIG. It is a schematic block diagram explaining the structure of the equipment monitoring device according to Embodiment 2 of this invention. It is a figure explaining the physical quantity detector 15 # according to Embodiment 2 of this invention. It is a schematic block diagram explaining the structure of the equipment monitoring device according to Embodiment 3 of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Equipment equipment monitoring apparatus, 5a-5c Equipment equipment, 10, 10 # repeater, 15, 15a-15c, 15a # -15c # Physical quantity detector, 16, 31, 33, 36 Modulation / demodulation circuit, 17 Signal processing circuit, 18 Sensor unit, 19a to 19c, 26a to 26c Loop antenna, 20 object to be measured, 25 switch, 30 transmission / reception unit, 32, 37 signal processing unit, 34, 38 antenna, 35 transmission / reception unit, 40 control unit, 45 electric wire, 46 screw, 47 spacer, 50 circuit breaker, 60, 61 printed circuit board.

Claims (7)

In equipment monitoring equipment that monitors the physical quantities of measured points of equipment,
A plurality of detectors that are provided corresponding to a plurality of measurement locations of the equipment, respectively, and that operate by power supplied wirelessly from the outside,
A repeater provided in the equipment;
A communication device for wireless communication with the repeater,
The detector is
A sensor unit for generating an output signal corresponding to a physical quantity to be detected;
A transmission unit for transmitting the output signal;
A first loop antenna, receiving a signal transmitted from the repeater via the first loop antenna, and generating an electromotive force generated by the received signal in each circuit of the detector And supplying the signal output from the transmission unit via the first loop antenna,
The repeater is
A plurality of second loop antennas provided corresponding to the first loop antennas of each of the detectors for wireless communication with the corresponding first loop antennas;
A switch for selecting any one of the plurality of second loop antennas in response to an instruction signal from the communication device;
A transmission / reception unit that receives a signal from the detector via the selected second loop antenna and transmits the signal to the communication device, and selects a physical quantity of a measurement location by the instruction signal; Equipment equipment monitoring device to monitor.   The first and second loop antennas are symmetrical with each other, and are arranged so as to face each other, and the arrangement interval of the first and second loop antennas is larger than the radius of the loop antenna. The equipment monitoring apparatus according to claim 1, which is set as follows.   The distance between the second loop antennas adjacent to each other among the plurality of second loop antennas of the repeater is set to be greater than or equal to the radius of the second loop antenna. The equipment monitoring device described.   The frequency of electromagnetic waves for performing wireless communication between each second loop antenna of the repeater and the first loop antenna of the corresponding detector is the self-resonant frequency of the first and second loop antennas. The facility equipment monitoring apparatus according to claim 2, wherein the equipment monitoring apparatus is set to be 1/3 or less of the above.   The equipment monitoring apparatus according to claim 1, further comprising a holding member that integrally holds the repeater and the detectors. The equipment corresponds to a circuit breaker,
The plurality of second loop antennas of the repeater and the first loop antennas of the detectors are arranged to face each other and in parallel through the holding member,
The plurality of second loop antennas of the repeater and the first loop antenna of each detector are arranged so that a normal line of a loop antenna surface is orthogonal to an electric wire connected to the circuit breaker. Item 5. The equipment monitoring apparatus according to Item 5. Each said repeater is
The equipment monitoring apparatus according to claim 1, comprising a modulation / demodulation circuit provided between the switch and each of the second loop antennas.

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