JP2013228209A - Electromagnetic field sensor and system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electromagnetic field sensor and system including a compact electromagnetic field sensor capable of measuring electric field intensities of mutually orthogonal XYZ components.SOLUTION: There is provided an electromagnetic field sensor and system including an electromagnetic field sensor 100 including a plurality of coils which are arranged having their axes in mutually orthogonal XYZ directions and an amplifier which amplifies a voltage based upon an electromagnetic field induced by the respective coils, a cable 200 which connects an output end of the electromagnetic field sensor 100 to an input end of a switch (SW) 300, the (SW) 300 which selects one of a plurality of signals output from the electromagnetic field sensor 100, and a spectrum analyzer (SA) 400 connected to the amplifier of the electromagnetic field sensor 100.

Description

  The present invention relates to an electromagnetic field sensor and system, and more particularly to an electromagnetic field sensor and system capable of measuring electromagnetic field strengths of XYZ components orthogonal to each other.

  On June 18, 2007, the World Health Organization task group issued an environmental health criterion on health risks from exposure to low and very low frequency (up to 400 kHz) electric and magnetic fields.

  Even in our daily lives, electromagnetic cookers (IH cookers), vacuum cleaners, home TVs, personal computers, home appliances in general, digital home appliances in general, information equipment, lighting equipment, and electric vehicles that are expected to become popular in the future are also low. It has a source of frequency magnetic field.

  In order to avoid health risks due to exposure to human bodies with low-frequency magnetic fields, it is necessary to take measures to shield electromagnetic fields. For that purpose, the strength of low-frequency magnetic fields from any position of an electromagnetic cooker, etc. It is necessary to identify whether or not

http://www.who.int/peh-emf/publications/facts/fs322_ELF_fields_jp_final.pdf

  To take measures to shield electromagnetic fields, simply identify how much electromagnetic field is generated from which part of home appliances, etc., and take appropriate measures such as shielding measures against the source. It is considered necessary.

  Accordingly, an object of the present invention is to provide an electromagnetic field sensor capable of measuring the electromagnetic field strengths of XYZ components orthogonal to each other in order to solve the above problems.

In order to solve the above problems, the electromagnetic field sensor of the present invention is:
A plurality of coils arranged in XYZ directions in which the respective axes are orthogonal to each other;
And an amplifier that amplifies a voltage based on an electromagnetic field induced by each coil.

  The electromagnetic field sensor system of the present invention includes the electromagnetic field sensor and a spectrum analyzer connected to the amplifier.

  In addition, as each said coil, it is good to use a ferrite coil for size reduction of an electromagnetic field sensor. Thereby, spatial resolution can be improved. Furthermore, when a spectrum analyzer is used, it is possible to grasp the electromagnetic field intensity in the frequency band to be measured, that is, to perform frequency decomposition of the electromagnetic field.

  According to the present invention, the voltage in the XYZ directions of the electromagnetic field induced by each coil can be measured. In addition, in order to complement that the voltage based on the electromagnetic field is weak, it is handled by amplifying it with an amplifier.

It is a typical block diagram of the electromagnetic field sensor system of embodiment of this invention. It is a figure which shows the typical example of arrangement | positioning of several coil vicinity in the electromagnetic field sensor 100 shown in FIG. It is explanatory drawing of the electrical connection of the electromagnetic field sensor 100 shown in FIG. It is an explanatory view of a coil X ₁ shown in FIG. It is a figure which shows the example of arrangement | positioning of the coil group shown in FIG. It is a schematic diagram which shows the usage example of the electromagnetic field sensor system of the Example of this invention.

100 Sensor 200 Cable 300 Switch (SW)
400 Spectrum Analyzer (SA)
500 Personal computer (PC)

BEST MODE FOR CARRYING OUT THE INVENTION

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Description of configuration)
FIG. 1 is a schematic configuration diagram of an electromagnetic field sensor system according to an embodiment of the present invention. FIG. 1 shows an electromagnetic field sensor 100, a cable 200, a switch (hereinafter referred to as “SW”) 300, a spectrum analyzer (hereinafter referred to as “SA”) 400, and a personal computer, which will be described below. (Hereinafter referred to as “PC”) 500. FIG. 1 shows one configuration of the electromagnetic field sensor system, and a plurality of electromagnetic field sensors 100 may be prepared, and a plurality of SWs 300 may be prepared in association therewith.

  The electromagnetic field sensor 100 measures the direction and intensity of the electromagnetic field. The electromagnetic field sensor 100 is connected to the SW 300. As will be described later, in the present embodiment, in order to be able to specify the direction of the electromagnetic field, a plurality of coils whose axes are arranged in XYZ directions orthogonal to each other and induced by each coil And an amplifier that amplifies a voltage based on the electromagnetic field.

  In addition, although the example which made the shape of the electromagnetic field sensor 100 the dome shape is shown in FIG. 1, a shape is not limited to this, For example, it is good also as a column shape, a cube, a rectangular parallelepiped. As an example of the external dimensions of the electromagnetic field sensor 100, the size can be set to fit within φ40 mm × 30 mm, 30 mm × 30 mm × 30 mm, or 20 mm × 30 mm × 40 mm based on the coil size described later. Of course, depending on the electromagnetic field measurement target, it may not be necessary to reduce the size to this size. Therefore, the coil size is determined according to the size of the measurement target, and the size of the electromagnetic field sensor 100 itself is selected accordingly. do it. Therefore, the size of the electromagnetic field sensor 100 itself may be, for example, about 1.5 to 3 times the above size.

  In the present embodiment, the amplifier provided in the electromagnetic field sensor 100 preferably has an internal amplifier gain of about 20 dB. Further, the electromagnetic field sensor 100 is preferably configured to cover a frequency band of 10 Hz to 1 GHz. The conditions for this will be described later.

  The cable 200 connects the output end of the electromagnetic field sensor 100 and the input end of the SW 300. The cable 200 is not limited, but a coaxial cable may be adopted so that a noise component is hardly superimposed on the output signal from the electromagnetic field sensor 100 from the outside.

  The SW 300 is used to select one of a plurality of signals output from the electromagnetic field sensor 100. The output terminal of SW300 is connected to the input terminal of SA400. For these connections, for example, a coaxial cable may be employed.

  SA400 inputs an output signal from the electromagnetic field sensor 100 and measures a voltage level in a frequency bandwidth of a preset measurement range. Here, SA for low frequency is used. The output terminal of SA400 is connected to the input terminal of PC500.

  The PC 500 processes the measurement data output from the SA 400 and records it on a recording medium (not shown), or performs predetermined image processing based on each data to create image data, and is connected to the PC 500. Or output to a display.

  The configuration shown in FIG. 1 is an example. For example, if the SA 400 is prepared according to the number of coils, the SW 300 can be omitted.

  FIG. 2 is a diagram showing a schematic arrangement example near a plurality of coils (hereinafter also referred to as “coil group”) in the electromagnetic field sensor 100 shown in FIG. 1. FIG. 2A shows a plan view of the coil group, and FIG. 2B shows a side view of the coil group.

  As shown in FIG. 2, the electromagnetic field sensor 100 includes a spacer 110 provided on a substrate (not shown). The substrate and the spacer 110 should be made of a material that can accurately measure the strength of the electromagnetic field, such as a foam, a resin material, and wood. For example, a polystyrene foam can be used.

  FIG. 2A shows a spacer 110 having a rectangular parallelepiped outer shape with a central portion opened in a rectangular shape. However, the shape of the spacer 110 is not limited to this, for example, a cylindrical shape. It is good also as the external shape.

  A coil group is provided with the coil arrange | positioned in the aspect in which an axial center follows any one of a X direction, a Y direction, and a Z direction. It should be noted that the X direction, the Y direction, and the Z direction are relative to each other, and there is no absolute thing such as the X axis.

The spacer 110 has a condition in which the axial centers of the coils X ₁ , X _2, etc. are orthogonal to the center in the length direction of the coils Z ₁ , Z ₂ . Thus, for example, it is shorter than the case where the coil X ₁ or the like is shown in relatively Figure 2 does not necessarily have to be provided a spacer 110.

  Further, the layout of the coil group can be changed so that the spacer 110 is not provided. Specifically, for example, it is also a method to prepare a substrate assembled in a cube and arrange the coils so that the axis of the coil is along the vertical direction of each substrate.

On the spacer 110, the coils X ₁ and X ₂ are placed in a manner in which the axial center is in the X direction, and the coils Y ₁ and Y ₂ are placed in a manner in which the axial center is in the Y direction. In addition, coils Z ₁ and Z ₂ are placed in the opening portion of the spacer 110 in such a manner that the axis is in the Z direction.

FIG. 2 shows an example in which the coils Z ₁ and Z ₂ are installed diagonally in the rectangular opening, but the mounting conditions are not limited to this, and the coils Z ₁ , Z ₂ may be placed under the condition of providing symmetry.

  In addition, as described above, the voltage output from the coil group is amplified by the amplifier connected to each coil. For example, an amplifier board is prepared below the board (not shown). It should be provided on this.

FIG. 3 is an explanatory diagram of the electrical connection of the electromagnetic field sensor 100 shown in FIG. Here, the electrical connection relationship between the coils X ₁ and X ₂ is shown, but the electrical connection relationship between the coils Y ₁ and Y ₂ and the coils Z ₁ and Z ₂ is also the same.

As shown in FIG. 3, for example, the winding start side of the coil _{X 1} is connected through a wire 130 to a first input terminal of the aforementioned amplifier (AMP) 120. Further, the winding end side of the coil X ₁ is serially connected to the winding start side of the coil X _2. Further, the winding end side of the coil X ₂ are connected through a wire 140 to the second input terminal of the aforementioned amplifier 120. Since the coils X ₁ , X _2, etc. are connected in series, the voltage based on the X component of the electromagnetic field induced by them is synthesized.

The output terminal of the amplifier 120 and the output terminals of the amplifiers of the coils Y ₁ , Y ₂ , Z ₁ , and Z ₂ are connected to the input terminal of the SW 300 through the cable 200.

  Here, any type of amplifier 120 may be used, but it is preferable to obtain a high gain in a wide frequency band. Therefore, it is preferable to employ a negative feedback multi-stage amplifier to lower the gain per stage and expand the frequency band accordingly.

Figure 4 is an explanatory view of a coil X ₁ shown in FIG. FIG. 4A shows a ferrite core constituting the coil, and FIG. 4B shows a state in which an electric wire is wound around the ferrite core shown in FIG. The coil _{X 1} other coil _Y 1 other than, _{Z 1} and the like are also the same structure as the coil _{X 1} shown in FIG.

Coil _{X 1,} for example, a diameter of about 14 mm, is a size that approximately 12mm in height. However, this size is an example, and it may be about 1.5 to 3 times larger than this, or smaller. However, coil X _1, when too small an attempt to increase the spatial resolution, because the reception sensitivity of the electromagnetic field is reduced, even if the smaller, it is possible to keep up to at most about half the size.

Coil X ₁ is, although the ferrite core as described above, particularly, for example, can be adopted a ferrite core including manganese and zinc. Specifically, when attention is paid to the magnetic permeability, ferrite materials called “2G4” and “2H6” can be suitably used in an ultra-low frequency region up to 100 kHz.

  In other words, when it is desired to measure the electromagnetic field strength in the high frequency region, a ferrite core containing nickel and zinc, such as a ferrite material called “7B2”, may be employed. However, in such a case, the amplifier 120 and the SA 400 may be changed to those for high frequency.

Coil X _1, it means that functions as an electromagnetic field antenna, its size, the determination of the shape is important. In general, the larger the antenna opening, the higher the reception level, but there is also a limitation on the size of the electromagnetic field sensor 100.

  In the present embodiment, the number of coils wound around the ferrite material is secured to some extent to increase the inductance. For this reason, as shown in FIG. 4, the coil winding area is secured larger than that of a general ferrite coil.

Wires forming the coil X _1, for example, can be suitably used for electromagnetic field sensor of a low frequency, it may be two or polyurethane coated copper wire. When such a conducting wire is used, a wire having a wire diameter of about 0.05φ to 0.16φ may be selected in order to secure a certain number of turns of the coil wound around the ferrite material.

  When the electric wire is mechanically wound, a wire having a diameter of about 0.05φ to 0.09φ may be employed. On the other hand, when it is manually wound, it is preferable to use a wire having a diameter of about 0.10 to 0.16. Which winding method is used has its advantages and disadvantages, and may be determined according to the electromagnetic field measurement target or measurement sensitivity.

In the case of manual winding can prevent an increase in the DC resistance of the coil X _1, include merit enhances the reception sensitivity of the electromagnetic field. On the other hand, in the case of mechanical winding, there is a merit that a detailed winding method can be performed and winding unevenness is hardly generated.

FIG. 5 is a diagram illustrating an arrangement example of the coil group illustrated in FIG. 3. The arrangement example shown in FIG. 5 is similar to the aspect shown in FIG. 2, but shows a case where the spacer 110 is not necessary due to the shape of the coil X ₁ or the like. If each coil is arranged in the mode shown in FIG. 5, the entire coil group has reception directivity characteristics close to a hemisphere.

Here, the coil X ₁ and the like are used in a balanced connection, the input of the amplifier 120 or the like is unbalanced connection. To achieve this difference per alignment, where a balun: It is one method provided between the "balanced-to-unbalanced transformer" signal conversion element such as a coil X ₁ or the like and the amplifier 120 or the like.

However, since the transformer has frequency amplitude characteristics and is not suitable for transmitting a wide frequency, a signal conversion IC having the same main function may be used instead of the signal conversion element. Accordingly, the voltage induced in coil X ₁ and the like, can be converted to without loss unbalanced inputs to the amplifier 120 or the like.

(Description of operation)
Next, the operation of the electromagnetic field sensor system of the present embodiment will be described by taking as an example the case of measuring the electromagnetic field strength in an electric vehicle under development.

  First, a user of an electromagnetic field sensor system sets a plurality of electromagnetic field sensors 100 in, for example, an electric vehicle that is a measurement target of electromagnetic field strength. For example, when the purpose of taking the electromagnetic field shielding measures in the electric vehicle under development is set, the position where each electromagnetic field sensor 100 is set will normally be set near each seat in the vehicle.

  Next, a frequency bandwidth that is a measurement range is set for SA400. According to the environmental health criteria issued by the World Health Organization, it is preferable to investigate the strength of the electromagnetic field in the frequency band of 10 Hz to 400 kHz, so these frequency bands will be selected.

In this state, when each electromagnetic field sensor is turned on, the coils X ₁ , X ₂ , Y ₁ , Y ₂ , Z ₁ , and Z ₂ provided in the electromagnetic field sensor 100 include the X component and Y component of the electromagnetic field. A voltage based on the Z component is induced. As a result, the voltage based on the X component of the electromagnetic field induced by the coils X ₁ and X ₂ is synthesized and output to the amplifier 120. Similarly, the induced voltage based on the Y component and the Z component of the electromagnetic field in the coils Y ₁ and Y ₂ and the coils Z ₁ and Z ₂ is output to the amplifier connected thereto.

In the amplifier 120 or the like, the voltage output from the coils X ₁ and X ₂ or the like is amplified and input to the input terminal of the SW 300 through the cable 200. In SW300, one of the signals output from amplifier 120 or the like is selected, and the selected signal is output to SA400.

  In SA400, the voltage level is measured in a frequency bandwidth of a preset measurement range. This measurement data is output to the PC 500. In the PC 500, the measurement data output from the SA 400 is processed. As a result, the processing result in the PC 500 can be output to the display.

  As a result of the above operations, developers of electric vehicles can take electromagnetic field shielding measures against the electromagnetic field generation source based on the intensity and direction of the electromagnetic field obtained by the electromagnetic field sensor system. It becomes.

  FIG. 6 is a schematic diagram showing a usage example of the electromagnetic field sensor system according to the embodiment of the present invention. FIG. 6 shows a usage example in the case of measuring an electromagnetic field generated from the electric vehicle 1000 under development or the like. Here, for example, it is investigated how much low frequency magnetic field exposure occurs in the vicinity of the head, chest, and legs of each of the driver of the electric vehicle 1000, the passenger in the passenger seat, and the three passengers in the rear seat. A usage example for doing this will be described.

  As shown in FIG. 6, the electromagnetic field sensor system of this embodiment includes a head electromagnetic field sensor 100A for detecting an electromagnetic field near the head of a passenger in a passenger seat of an electric vehicle 1000, and an electromagnetic field near the chest. A chest electromagnetic field sensor 100B for detecting the field and a head electromagnetic field sensor 100C for detecting the electromagnetic field near the legs are provided.

  Similarly, the electromagnetic field sensor system of the present embodiment includes the electromagnetic field sensors 100C to 100O in the driver seat and the rear seat. However, electromagnetic sensors for two people may be used in the rear seat. Further, although an example using three electromagnetic field sensors for each person is shown, the number may be larger, for example, 15 for each person, and conversely, for example, one for each person. May be.

  In addition, it is not essential that the electromagnetic field sensors 100A to 100O used in the present embodiment are the same as those described in the above-described embodiment. Therefore, for example, an electromagnetic wave measuring device “ELT-400” manufactured by NARDA, a magnetic field measuring device “FT3470-52” manufactured by Hioki Electric Co., Ltd., and the like can be used. However, in comparison with these, what has been described in the above-described embodiment is small in size, and can measure the electromagnetic field strength in the three-axis directions of the XYZ axes. Very beneficial.

  These electromagnetic field sensors 100A and the like may actually be attached to a passenger in the passenger seat, may be attached to an appropriate position of the passenger seat itself, etc. It may be placed. Note that the electromagnetic field sensor system according to the present embodiment can measure the electromagnetic field generated during traveling by actually driving the electric vehicle 1000 if the electromagnetic field sensors 100D to 100F are attached to the driver. It becomes.

  In addition, the electromagnetic field sensor system of this embodiment can be installed in a trunk space or the like, and includes a PC 500, a DC-AC converter 700, filter boxes 800A to 800E, and oscilloscopes 900A to 900O, which will be described below. A rack 2000 is provided.

  However, it should be noted that the shield rack 2000 is not necessarily installed in the trunk space. However, when the electric vehicle 1000 is actually traveled and the electromagnetic field generated during travel is measured, the shield rack 2000 may be installed in the trunk space. On the other hand, the shield rack 2000 may be provided outside the electric vehicle 1000 if the electromagnetic field generated when the engine of the electric vehicle 1000 is started or when the accelerator is further depressed is only measured. Is possible.

  The DC-AC converter 700 is a converter 700 for converting a DC 12V power source mounted on the electric vehicle 1000 into an AC 100V power source. The power source converted by the DC-AC converter 700 is used for the PC 500 and the oscilloscopes 900A to 900O. However, the DC-AC converter 700 is not essential, and a storage battery or the like may be used as a power source for the PC 500 or the like.

  The filter boxes 800A to 800E are for removing external noise superimposed on an output signal from the electromagnetic field sensor 100A or the like. Although it is not essential to provide the filter boxes 800A to 800E, when "ELT-400" or "FT3470-52" is used as the electromagnetic field sensor 100A or the like, the display unit provided in these is a noise generation source. Therefore, it is desirable to provide for removing this kind of noise.

  The oscilloscopes 900A to 900O are illustrated as substitutes for the SA400. Therefore, of course, the SA400 may be used instead of the oscilloscopes 900A to 900O. In the case where processing of measurement data is not necessary in real time, a data logger may be used instead of the oscilloscopes 900A to 900O and the PC 500. In this case, there is an advantage that it is not necessary to install 15 units depending on the type of data logger and only one unit is required. Which one to select is considered in consideration of the capacity of the trunk space of the electric vehicle 1000 and the like.

  In addition, when performing frequency analysis on noise data acquired by the oscilloscopes 900A to 900O or a data logger, for example, one that can perform fast Fourier transform (FFT) analysis can be used.

  The PC 500 is the same as that shown in FIG. In the example shown in FIG. 6, a small PC such as a notebook type or a tablet type may be used in consideration of the capacity of the trunk space. Output from the oscilloscopes 900A to 900O is input to the PC 500, and the same processing as in the above-described embodiment is performed.

  According to the electromagnetic field sensor system of the present embodiment, it is possible to measure the exposure state of the electromagnetic field to the human body in the electric vehicle 1000, and it is possible to effectively take measures for shielding the electromagnetic field.

Claims (6)

A plurality of coils arranged in XYZ directions in which the respective axes are orthogonal to each other;
An electromagnetic field sensor comprising: an amplifier that amplifies a voltage based on an electromagnetic field induced by each coil.   The electromagnetic field sensor according to claim 1, wherein each of the coils is a ferrite coil.   The electromagnetic field sensor according to claim 1, wherein a plurality of coils are arranged in each of the XYZ directions.   The electromagnetic field sensor according to claim 1, wherein each of the coils is arranged with symmetry.   The electromagnetic field sensor according to claim 1, wherein the amplifier is a negative feedback multistage amplifier. The electromagnetic field sensor according to claim 1;
And a spectrum analyzer connected to the amplifier of the electromagnetic field sensor.