JP2004170284A - Permeability measuring device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain accurate relative permeability by accurately obtaining magnetic field information over from a low-frequency band to a high-frequency band. <P>SOLUTION: A magnetic field generating coil 14 generates a nearly uniform alternating current magnetic field with the alternating current from a high-frequency power source 18. A printed board 20 having an annular conductive pattern 22 is arranged in the magnetic field generating coil 14. A through hole 26 is provided in a part of the printed board 20 inside the conductive pattern 22, and a gap 24 is provided on the way to the conductive pattern 22. An electro-optical element 28 formed into a rectangular parallelopiped is inserted into the gap 24 of the conductive pattern 22. After the laser beam from a laser beam source passes the electro-optical element 28, a photo-receiver detects the laser beam. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a magnetic permeability measuring device that acquires magnetic field information with high accuracy from a low frequency band to a high frequency band and accurately measures the magnetic permeability of a magnetic material.
[0002]
[Prior art]
Conventionally, in order to measure the magnetic permeability of a magnetic material, an inductance method, a yoke method, and the like are used. In addition, magnetic permeability measuring devices disclosed in Patent Documents 1 and 2 below are also known for measuring high-frequency magnetic permeability. I have. Among them, for example, Patent Literature 1 discloses a magnetic permeability measuring apparatus having a structure in which a measurement coil 116 having a through hole into which a magnetic sample M is inserted as shown in FIG. Is disclosed.
[0003]
In this magnetic permeability measuring device, an AC magnetic field is generated in the magnetic field generating coil 112 by a voltage from the high frequency power supply 114, the AC magnetic field is detected by the measuring coil 116, and the obtained magnetic field information is transmitted as a metal signal as an electric signal. It functions as a magnetic field sensor that transmits the signal to a measuring device (not shown) via a signal extraction portion 118 and a ground conductor 120 which are paths.
[0004]
Then, an electric signal which is an output of the measurement coil 116 when the magnetic sample M is not inserted into the through hole of the measurement coil 116, and an output when the magnetic sample M is inserted into the through hole of the measurement coil 116. This electrical signal was measured by a measuring machine transmitted through the signal extraction unit 118 and the ground conductor 120, and the relative magnetic permeability of the magnetic sample M was determined from the output in each case.
[0005]
[Patent Document 1]
Japanese Patent Application Laid-Open No. 7-104044 [Patent Document 2]
JP-A-61-58771
[Problems to be solved by the invention]
However, when the high-frequency magnetic permeability is measured by the magnetic permeability measuring device disclosed in Patent Document 1, the impedance matching at the connection between the measurement coil 116 and the metal transmission line such as the signal extraction unit 118 is insufficient. For this reason, there is a possibility that measurement accuracy may be reduced due to reflection or superimposition of a signal due to an electric field received by a metal transmission line such as the measurement coil 116 and the signal extraction unit 118. That is, as a result, the relative magnetic permeability could be measured only up to about 100 MHz, and the relative magnetic permeability could not be measured with high accuracy in the GHz band.
[0007]
As described above, it has been difficult to measure the relative magnetic permeability with high accuracy in a high frequency band such as the GHz band by the conventional magnetic permeability measuring device.
The present invention has been made in view of the above-described circumstances, and has as its object to provide a magnetic permeability measuring device that obtains magnetic field information with high accuracy from a low frequency band to a high frequency band and obtains an accurate relative magnetic permeability.
[0008]
[Means for Solving the Problems]
A magnetic permeability measuring apparatus according to claim 1 includes a light source that generates light,
A magnetic field generating coil capable of generating an alternating magnetic field,
A magnetic field detecting coil disposed in the magnetic field generating coil and formed in an annular shape from a conductive material while having a gap,
An electro-optic crystal that is inserted into the gap of the magnetic field detection coil and through which light from the light source can pass;
A light detection member for detecting a state of light passing through the electro-optic crystal,
It is characterized by having.
[0009]
According to the magnetic permeability measuring apparatus of the first aspect, the magnetic field detecting coil formed annularly of a conductive material while having a gap is disposed in the magnetic field generating coil capable of generating an AC magnetic field. It has a configuration in which an electro-optic crystal is inserted into the gap of the detection coil. Further, light from a light source that generates light passes through the electro-optic crystal, and the state of the passed light is detected by the light detection member.
[0010]
Therefore, the magnetic permeability measuring device according to the present invention is configured such that a gap is formed in the magnetic field detecting coil disposed in the magnetic field generating coil, and the electro-optic crystal is inserted into the gap. Then, by passing light such as laser light from a light source through the electro-optical crystal, the magnetic field information detected and obtained by the magnetic field detecting coil is converted into an optical signal using the electro-optical effect of the electro-optical crystal. Can be converted.
[0011]
Specifically, the output when the magnetic sample is not inserted into the magnetic field detection coil and the output when the magnetic sample is inserted into the magnetic field detection coil indicate the state of light passing through the electro-optic crystal. The relative permeability of the magnetic sample was obtained based on the output in each case obtained by detection by the light detection member.
[0012]
Accordingly, the sensor portion of the magnetic permeability measuring apparatus according to the present invention has a simple configuration in which a magnetic field is converted into an optical signal by a magnetic field detecting coil and an electro-optic crystal and the optical signal is transmitted. Since the light detection member detects the state of the light from the light source that has passed through the crystal, unlike a conventional magnetic field sensor that transmits an electric signal through a metal transmission line, a metal transmission line must not be used. become.
[0013]
For this reason, the magnetic field can be measured in a state where the influence of the electric field is small, and reflection due to insufficient impedance matching at the connection between the magnetic field detection coil and the metal transmission line can be eliminated. That is, since light is used, high-frequency magnetic permeability can be measured with high accuracy not only in a low frequency band but also in a high frequency band such as a GHz band.
[0014]
As a result, according to the magnetic permeability measuring apparatus according to the present invention, it is possible to measure a magnetic field with high accuracy from a low frequency band to a high frequency band, and to transmit magnetic field information with high accuracy. Accordingly, magnetic field information can be acquired with high accuracy, and an accurate relative magnetic permeability can be obtained.
[0015]
According to the magnetic permeability measuring apparatus of the second aspect, in addition to the same configuration as the magnetic permeability measuring apparatus of the first aspect, a magnetic field detecting coil is formed by a conductor pattern disposed on the substrate, and the magnetic field of the substrate is It has a configuration in which a through hole is provided in a portion inside the detection coil.
[0016]
In other words, according to the present invention, not only the function and effect of claim 1 but also the magnetic field detecting coil is formed by the conductor pattern arranged on the substrate, so that the shape of the magnetic field detecting coil is stabilized. This also has the effect of stabilizing the measurement data. In addition, since the magnetic field detecting coil is disposed on the substrate, it is easy to mount the electro-optic crystal in the gap of the magnetic field detecting coil.
[0017]
According to the magnetic permeability measuring apparatus of the third aspect, in addition to the same configuration as the magnetic permeability measuring apparatus of the first and second aspects, the electro-optic crystal is formed of lithium niobate or lithium tantalate. It has a configuration. That is, by adopting lithium niobate or lithium tantalate as the electro-optic crystal, the operation and effect of claim 1 can be more reliably achieved.
[0018]
According to the magnetic permeability measuring apparatus of the fourth aspect, in addition to the same configuration as the magnetic permeability measuring apparatus of the first to third aspects, a supporting portion is provided around a gap of the magnetic field detecting coil, and the supporting portion is provided. By sandwiching the electro-optic crystal between them, the electro-optic crystal is inserted into the gap.
[0019]
In other words, if the magnetic field detecting coil is a conductor pattern arranged on the substrate as in claim 2, simply inserting the electro-optic crystal in the gap cannot apply an electric field uniformly over a wide range of the electro-optic crystal. However, for example, when a metal support is provided around the gap, the electro-optic crystal is sandwiched between the supports, so that the support serves as an electrode and an electric field is applied over a wide range of the electro-optic crystal. Can be applied uniformly. As a result, the effect of the first aspect can be more reliably achieved with the more reliable use of the electro-optic effect of the electro-optic crystal.
[0020]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of a magnetic permeability measuring apparatus according to the present invention will be described with reference to the drawings. As shown in FIGS. 1 to 4, the magnetic permeability measuring apparatus 10 according to the present embodiment transmits a sensor body 12 which is an optical magnetic field sensor disposed in an electromagnetic field to be measured and a laser beam L. It is composed of an optical system capable of receiving light and the like.
[0021]
As shown in FIGS. 1 and 2, a magnetic field generating coil 14 which is an outer frame of the sensor main body 12 is formed in a rectangular tubular shape obtained by bending a metal plate and one end is opened. Wirings 16 are connected to both ends of the open magnetic field generating coil 14, respectively, and a high frequency power supply 18 for generating a high frequency alternating current is connected to the end of the magnetic field generating coil 14 through the wiring 16. Connected to each other. Thus, the alternating current from the high frequency power supply 18 causes the magnetic field generating coil 14 to generate a substantially uniform alternating magnetic field.
[0022]
A printed circuit board 20 made of glass epoxy as shown in FIGS. 1 to 3 is disposed in the magnetic field generating coil 14 so that its surface is orthogonal to the direction in which the magnetic field generating coil 14 penetrates. On the printed circuit board 20, a conductor pattern 22, which is a magnetic field detecting coil formed in, for example, a rectangular shape in a ring shape, is provided in a planar manner with a conductive material such as a metal. A through hole 26 having an inner peripheral surface along the inner peripheral side of the conductive pattern 22 is provided in a portion of the printed circuit board 20 in the conductive pattern 22. A gap 24, which is a gap, is provided in the portion while notching the printed circuit board 20.
[0023]
On the other hand, a pair of parallel plate electrodes 25A and 25B, which are support portions, are provided at the ends of the conductor pattern 22 forming the gap 24, as shown in FIG. Are arranged in parallel with each other. That is, a pair of parallel plate electrodes 25A and 25B formed of copper or the like in an L-shape are connected to the peripheral portion of the gap 24 of the conductor pattern 22 by soldering.
[0024]
In the gap 24 of the conductor pattern 22, an electro-optical element 28 formed in a rectangular parallelepiped shape is brought into contact with each of the pair of parallel plate electrodes 25A and 25B facing each other, and for example, a conductive (not shown). It is inserted and arranged so that it is adhered with a conductive adhesive. The electro-optical element 28 is formed of an electro-optical crystal. As the electro-optical crystal, for example, a crystal of lithium niobate (LiNbO ₃ ) whose refractive index changes with a change in applied voltage is used. .
[0025]
Therefore, the sensor main body 12 according to the present embodiment can be manufactured by the magnetic field generating coil 14, the high frequency power supply 18, the printed circuit board 20, the conductor pattern 22, the parallel plate electrodes 25A and 25B, the electro-optical element 28, and the like. Further, in the present embodiment, the electro-optical element 28 is arranged such that the optical axis direction is directed to a predetermined direction so that magnetic field information can be reliably extracted.
[0026]
Next, the entire optical system of the magnetic permeability measuring apparatus 10 according to the present embodiment will be described with reference to FIG.
As shown in FIG. 4, the present embodiment has a laser light source 30 that generates a laser beam L, and a lens serving as a light emitting unit provided at an end of an optical fiber 32 connected to the laser light source 30. 32A emits the laser light L sent from the laser light source 30.
[0027]
On the other hand, an optical fiber 40 is connected to a photo receiver 42 which is a light detecting member for converting a change in light intensity into a change in current amount, and a lens 40A provided at an end of the optical fiber 40 and serving as a light receiving unit. Receive the laser beam L. Therefore, the laser light L received by the lens 40A passes through the optical fiber 40, and the photo receiver 42 can detect the state of the laser light L. The photo receiver 42 is connected to a network analyzer 44 capable of displaying a change in the amount of current converted by the photo receiver 42, and the network analyzer 44 is also connected to the magnetic field generating coil 14. .
[0028]
Further, the lens 40A is arranged at a position where the laser light L emitted from the lens 32A can be received, and between the lens 32A and the lens 40A, the laser light L is sequentially arranged from the lens 32A side. A polarizer 34, an electro-optical element 28, a wave plate 36, and an analyzer 38 for converting a change in the polarization state into a change in the intensity of light are arranged in a straight line. That is, the present embodiment is of a straight traveling system in which the laser light L travels straight.
[0029]
As described above, when the laser light source 30 generates the laser light L, the laser light L passes through the optical fiber 32 and is emitted from the lens 32A, passes through the laser light L in the above order, and is received by the lens 40A of the optical fiber 40. Become like Then, the photo receiver 42 detects the state of the laser light L entering the optical fiber 40 from the lens 40A.
[0030]
On the other hand, when, for example, a magnetic flux passes through the through hole 26 of the conductive pattern 22 shown in FIGS. 1 to 3 which is a conductive loop, a current flows through the conductive pattern 22. Along with this, a voltage is generated around the gap 24 of the conductor pattern 22, and the voltage is applied to the electro-optical element 28 disposed in the gap 24 to generate an electric field. The rate changes. That is, the magnetic flux penetrating through the conductor pattern 22 becomes magnetic field information detected by the sensor main body 12, and this magnetic field information is converted into a change in the refractive index of the electro-optical element 28.
[0031]
Further, the magnetic permeability measuring apparatus 10 according to the present embodiment uses the structure shown in FIG. 4 to temporarily change the change in the refractive index of the electro-optical element 28 as the change in the polarization state of the laser light L injected into the electro-optical element 28. Can be caught. Then, by passing the light through the analyzer 38, the change in the polarization state is converted into a change in the intensity of the laser light L, and finally, the change in the amount of current is converted by the photo receiver 42. As a result, the network analyzer 44 connected to the photo receiver 42 can display the change in the amount of current, and calculate the relative magnetic permeability based on the display of the network analyzer 44 so that the relative magnetic permeability can be obtained. become.
[0032]
From the above, the optical system of the magnetic permeability measuring apparatus 10 according to the present embodiment includes the laser light source 30 and the photo receiver 42, and further, the optical fiber 32 disposed between the laser light source 30 and the photo receiver 42, It consists of a polarizer 34, a wave plate 36, an analyzer 38, an optical fiber 40 and the like.
[0033]
Next, a procedure for calculating the relative magnetic permeability from the output of the photo receiver 42 will be described.
Specifically, in the magnetic permeability measuring apparatus 10 described above, an AC magnetic field is generated by the magnetic field generating coil 14, and the photo-receiver 42 when the magnetic sample M is not inserted into the through hole 26 of the printed circuit board 20 shown in FIG. And the output of the photoreceiver 42 when the magnetic sample M is inserted into the through hole 26 shown in FIG. 2, respectively, and the relative magnetic permeability of the magnetic sample M is obtained by the following equation.
[0034]
First, _assuming that the output in the state shown in FIG. 1 is V _OUT0 and the output in the state shown in FIG. 2 is V _OUTM , the magnetic sample M is inserted into the through hole 26 of the printed circuit board 20 according to the following equations 1 and 2. an induced electromotive voltage V ₀ and by the magnetic field if not, to calculate the induced electromotive voltage V _M by the magnetic field in the case of inserting the magnetic sample M in the through hole 26, respectively.
[0035]
V ₀ = α · V _OUT0 Equation 1
V _M = α · V _OUTM Equation 2
That is, it equation 1, 0 induced electromotive voltage _V from equation 2, _{V M} is the output _V OUT0 of the photoreceiver _{42, V OUTM} respectively a linear relationship. Here, α is a constant determined by the sensor body 12 and the optical system.
[0036]
Further, mu _r is a relative permeability of these induced electromotive voltage V _0, V _M of a magnetic sample M is calculated by the following equation 3.
_{μ r = S / (t ·} d) · (V M / V 0 -1) + 1 ... Equation 3
Here, as shown in FIG. 1, S is the opening area of the through hole 26, t is the thickness of the magnetic sample M, and d is the width of the magnetic sample M.
[0037]
Next, the operation of the magnetic permeability measuring device 10 according to the present embodiment will be described.
According to the magnetic permeability measuring apparatus 10 according to the present embodiment, as shown in FIGS. 1 to 4, the printed circuit board 20 is disposed in the magnetic field generating coil 14 capable of generating a substantially uniform AC magnetic field. A conductor pattern 22 formed of a conductive material in an annular shape is disposed on the printed board 20, and a through hole 26 is provided in a portion of the printed board 20 in the conductor pattern 22. Further, a gap 24 is formed in the conductor pattern 22, and the electro-optical element 28 is inserted into the gap 24 with the optical axis direction adjusted.
[0038]
Further, the laser light L from the laser light source 30 is applied to an optical fiber 32, a polarizer 34, an electro-optical element 28, a wave plate 36, which is disposed between the laser light source 30 and the photo receiver 42 as shown in FIG. The photoreceiver 42 finally detects the state of the laser light L passing through the analyzer 38 and the optical fiber 40 and passing through the analyzer 38 and the optical fiber 40.
[0039]
Therefore, the magnetic permeability measuring apparatus 10 according to the present embodiment is configured such that the gap 24 is formed in the conductor pattern 22 disposed in the magnetic field generating coil 14 and the electro-optical element 28 is inserted into the gap 24. ing. Then, by passing the laser light L from the laser light source 30 through the electro-optical element 28, the magnetic field information detected and obtained by the conductor pattern 22 is utilized by utilizing the electro-optical effect of the electro-optical element 28 as described above. Was converted to an optical signal.
[0040]
Further, in the present embodiment, the polarizer 34, the wave plate 36, and the analyzer 38 disposed between the laser light source 30 and the photo receiver 42 adjust the state of the laser light L, and the optimally adjusted laser light L The state of L was detected by the photo receiver 42, and the network analyzer 44 displayed the magnetic field information detected by the photo receiver 42. Finally, the relative magnetic permeability was calculated from the displayed magnetic field information.
[0041]
Specifically, the output V _OUT0 when the magnetic sample M is not inserted into the through hole 26 in the conductor pattern 22 shown in FIG. 1 and the output V _OUT0 when the magnetic sample M is inserted into the through hole 26 shown in FIG. The output V _OUTM is obtained by detecting the state of the laser beam L that has passed through the electro-optical element 28 with the photoreceiver 42. Based on the output in each case, the relative permeability of the magnetic sample M is calculated by the above-described equation. The magnetic susceptibility _μr was obtained.
[0042]
Accordingly, the sensor portion of the magnetic permeability measuring apparatus 10 according to the present embodiment has a simple configuration in which a magnetic field is converted into an optical signal by the conductor pattern 22 and the electro-optical element 28 and the optical signal is transmitted. Since the photo receiver 42 detects the state of the laser light L from the laser light source 30 that has passed through the electro-optical element 28, unlike a conventional magnetic field sensor that transmits an electric signal through a metal transmission path, the metal transmission You are not using the road.
[0043]
Therefore, the magnetic field can be measured in a state where the influence of the electric field is small, the reflection caused by insufficient impedance matching at the connection between the conductor pattern and the metal transmission line can be eliminated. Therefore, the permeability can be measured with high accuracy not only in a low frequency band but also in a high frequency band such as a GHz band.
[0044]
As a result of the above, according to the magnetic permeability measuring apparatus 10 according to the present embodiment, it is possible to measure a magnetic field with high accuracy from a low frequency band to a high frequency band, and to transmit magnetic field information with high accuracy. As it becomes possible, it becomes possible to acquire magnetic field information with high accuracy and obtain relative magnetic permeability with high accuracy.
[0045]
On the other hand, in the present embodiment, a magnetic field detecting coil is formed by the conductor pattern 22 disposed on the printed board 20, and the through hole 26 is provided in a portion of the printed board 20 in the conductor pattern 22. The shape of the conductor pattern 22 is stabilized, and accordingly, the measurement data is also stabilized. In addition, since the conductor pattern 22 is disposed on the printed circuit board 20, the mounting of the electro-optical element 28 in the gap 24 of the conductor pattern 22 is facilitated.
[0046]
On the other hand, in the present embodiment, as shown in FIG. 3, a pair of parallel plate electrodes 25A and 25B is provided around the gap 24 of the conductor pattern 22, and the electro-optical element 28 is formed by the pair of parallel plate electrodes 25A and 25B. The sandwiching has a structure in which the electro-optical element 28 is inserted into the gap 24.
[0047]
That is, although the electric field cannot be applied uniformly over a wide range of the electro-optical element 28 by simply inserting the electro-optical element 28 into the gap 24 of the conductor pattern 22, the metal parallel plate electrodes 25A and 25B are formed around the gap 24. When the electro-optical element 28 is sandwiched between the parallel plate electrodes 25A, 25B, the electric field can be uniformly applied over a wide range of the electro-optical element 28 by the parallel plate electrodes 25A, 25B. As a result, with the more reliable use of the electro-optical effect of the electro-optical element 28, the above-described effect of acquiring the magnetic field information with high accuracy and obtaining the relative magnetic permeability with high accuracy is more reliably achieved. Will be able to achieve.
[0048]
In the present embodiment, when the electro-optical element 28 is disposed between the pair of parallel plate electrodes 25A and 25B, a conductive adhesive is used. However, the electro-optical element 28 is not coated with the conductive adhesive. Alternatively, the pair of parallel plate electrodes 25A and 25B may be simply sandwiched. The thickness of at least the portion of the pair of parallel plate electrodes 25A and 25B opposed to the electro-optical element 28 may be, for example, about 150 μm.
[0049]
Further, in the above-described embodiment, the conductor pattern 22 is rectangular, but the conductor pattern 22 may be formed in another shape such as a square or a circle, and the conductor pattern 22 is thin as in this embodiment. The material is not limited to a metallic conductive material, and may be a member such as a wire. On the other hand, although lithium niobate (LiNbO ₃ ) is used as the electro-optic crystal in the above embodiment, another electro-optic crystal such as lithium tantalate (LiTaO ₃ ) may be used. Further, in the above-described embodiment, one electro-optic crystal is used, but two electro-optic crystals may be used.
[0050]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the magnetic permeability measuring apparatus which acquires magnetic field information from low frequency band to high frequency band with high precision, and can obtain exact relative magnetic permeability.
[Brief description of the drawings]
FIG. 1 is a partially cutaway perspective view of a sensor main body according to an embodiment of the present invention, showing a state where a magnetic sample is not inserted into a through hole.
FIG. 2 is a partially cutaway perspective view of a sensor main body according to one embodiment of the present invention, showing a state where a magnetic sample is inserted into a through hole.
FIGS. 3A and 3B are diagrams showing a printed circuit board applied to one embodiment of the present invention, wherein FIG. 3A is a front view, and FIG. 3B is a view taken along line 3B-3B of FIG.
FIG. 4 is an overall view showing a magnetic permeability measuring apparatus according to one embodiment of the present invention.
FIG. 5 is an overall view showing a conventional magnetic permeability measuring apparatus.
[Explanation of symbols]
Reference Signs List 10 Permeability measuring device 14 Magnetic field generating coil 20 Printed circuit board (board)
22 Conductor pattern (magnetic field detection coil)
24 gap 25A parallel plate electrode (support)
25B parallel plate electrode (support)
26 Through-hole 28 Electro-optical element (electro-optical crystal)
30 Laser light source (light source)
42 Photo Receiver (Light Detector)

Claims (4)

A light source for generating light,
A magnetic field generating coil capable of generating an alternating magnetic field,
A magnetic field detecting coil disposed in the magnetic field generating coil and formed in an annular shape from a conductive material while having a gap,
An electro-optic crystal that is inserted into the gap of the magnetic field detection coil and through which light from the light source can pass;
A light detection member for detecting a state of light passing through the electro-optic crystal,
A magnetic permeability measuring device characterized by having: 2. The magnetic permeability measuring apparatus according to claim 1, wherein a magnetic field detecting coil is formed by a conductor pattern disposed on the substrate, and a through hole is provided in a portion of the substrate within the magnetic field detecting coil. 3. The magnetic permeability measuring device according to claim 1, wherein the electro-optic crystal is formed of lithium niobate or lithium tantalate. The electro-optic crystal is inserted into the gap by providing a support portion around a gap of the magnetic field detecting coil and sandwiching the electro-optic crystal between the support portions. The magnetic permeability measuring device according to any one of the above.

Images