JP3144871B2 - Permeability measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for measuring the effective magnetic permeability of a thin-film magnetic material at high frequencies and its real and imaginary parts with as small an error as possible.

[0002]

2. Description of the Related Art Conventionally, an inductance method, a yoke method, and the like have been used as a method for measuring the magnetic permeability of a magnetic material. In these methods, measurement at high frequency was difficult due to self-resonance caused by the distributed capacitance of the coil. As an alternative to these methods, a magnetic permeability measurement method using a differential coil is known.

[0003] The structure of a detection unit of a magnetic permeability measuring apparatus using a differential coil is disclosed in Japanese Patent Application Laid-Open No. 61-58771. That is, as shown in FIG. 6, this magnetic permeability measuring device generates an alternating magnetic field by applying a voltage from a high frequency power supply 4 for excitation to a magnetic field generating coil 2 having a rectangular cross section. 2 so that the plane is orthogonal to the alternating magnetic field generated by the magnetic field generating coil 2.
A measurement differential coil 6 and a magnetic field detection coil 8 wound in an eight-shape are provided in one of the coils, and a magnetic permeability measurement sample (hereinafter, simply referred to as a sample) 9 is provided in one coil portion of the measurement differential coil 6.
Insert the ratio between the output voltage E _H of the output voltage E _B and the magnetic field detecting coil 8 of the measuring differential coil 6, μ = (E _B /
The magnetic permeability is measured from E _H ) · (S _H / S _B ). Here, S _H is the effective area of the magnetic field detection coil 8, the S _B is the cross-sectional area of the sample 9.

In the above prior art, the measuring differential coil 6 and the magnetic field detecting coil 8 disposed in the magnetic field generating coil 2 are formed, for example, on a frame made of a glass material having a low magnetic permeability. It is obtained by winding a thin conductive wire.

[0005]

However, in the above configuration, the dimensional accuracy is not significantly improved, and
Variations appear as products, and it is difficult to accurately measure magnetic permeability.

In addition, different magnetic permeability is measured depending on the degree of insertion of the sample, and there is a problem that the reliability of the measurement result cannot be obtained.

SUMMARY OF THE INVENTION The present invention has been made to overcome the above-mentioned disadvantages, and has a simple structure.
An object of the present invention is to provide a magnetic permeability measuring apparatus which can quickly measure a magnetic permeability with a small measurement error and which has excellent dimensional accuracy of a measuring section.

[0008]

SUMMARY OF THE INVENTION To achieve the above object, the present invention provides a magnetic field generating coil for generating a substantially uniform alternating magnetic field, and a magnetic field detecting coil disposed in the magnetic field generating coil. And a differential coil for measurement, wherein the magnetic permeability is measured from the output voltage of the differential coil for measurement and the output voltage of the magnetic field detection coil. The coil is characterized by being wound on a single substrate.

[0009]

The sample is brought close to the measuring differential coil formed on the substrate to obtain the output voltage. On the other hand, the output voltage when the measurement differential coil is in the air-core state is obtained, the difference between the two output voltages is obtained, the output voltage value of the measurement differential coil is corrected by an error, and the magnetic field detection coil The magnetic permeability is measured from the ratio to the output voltage. At this time, since the measurement differential coil and the magnetic field detection coil are provided on the substrate, the dimensional accuracy is improved, and the measurement of the magnetic permeability can be achieved accurately and quickly.

[0010]

The present invention will be described below with reference to examples.

In FIG. 1, reference numeral 10 denotes a magnetic permeability measuring device according to the present invention. This magnetic permeability measuring device 10
Basically, the base 12 and the bolts 14
A guide member 16 fixed by
And a magnetic detection circuit 18 facing the same.

As can be easily understood from FIG. 1, the guide member 16 is provided with a dovetail groove 20 along the center in the longitudinal direction, and a slide member 22 is slidably provided in the dovetail groove 20. Mated. The tip of the sliding member 22 is used as a fixing portion of the sample W. In this case, a handle 24 is provided to displace the sliding member 22. Reference numeral 26 denotes a stopper for preventing further displacement of the slide member 22 provided at one end of the dovetail groove 20.

The guide member 16 faces a magnetic detection circuit 18. The magnetism detecting circuit 18 includes an exciting coil 28 bent on the C channel and a printed circuit board 30 disposed at the center of the exciting coil 28 in the vertical direction in the drawing.
A terminal portion 32 for taking out an output of a figure eight coil (described later) provided on the printed circuit board 30 to the outside.
It is composed of

The exciting coil 28 and the printed circuit board 30 are fixed, and a bolt 34 is inserted through a hole formed in the printed circuit board 30 and screwed into a screw groove of the guide member 16. It is integrated with the magnetic detection circuit 18.

FIGS. 3 and 4 show the wiring structure of the printed circuit board 30. FIG. As can be easily understood from FIG. 3, a measurement differential coil 44 is formed on one surface of the printed circuit board 30 by bending or bending a single conductor 42 substantially in a figure-eight shape. As shown in FIG.
A conductor 46 is formed as a magnetic field detection coil 48 by bending or bending the conductor 46 on the other surface of the magnetic field detecting coil 48. Measurement differential coil 44
Is connected to a first terminal 50 via a conductor (not shown).
, And the output side of the magnetic field detecting coil 48 is similarly connected to the second terminal 52. The output side of the exciting coil 28 is connected to the third terminal 54.
In the drawings, reference numerals 56a and 56b indicate through holes, reference numeral 57 indicates a first rectangular space defined on the printed circuit board 30, and reference numeral 58 indicates the first space. Shown below is a second space defined below 57 for sample insertion.

Next, a circuit configuration of the magnetic permeability measuring apparatus 10 configured as described above will be described with reference to FIG.

The permeability measuring apparatus 10 includes an oscillator 60 as a high-frequency power source for generating a magnetic field. The oscillation output from the oscillator 60 is supplied to a filter attenuator 62 to shape the waveform, and the level of the oscillator 60 is adjusted. The power is attenuated in proportion to the oscillation frequency, supplied to the high-frequency power amplifier 64 to amplify the power, and the output voltage of the high-frequency power amplifier 64 is applied to the exciting coil 28 to generate a substantially uniform alternating magnetic field.

The output voltage of the measuring differential coil 44 and the output voltage of the magnetic field detecting coil 48 generated by interlinking with the alternating magnetic field generated by the exciting coil 28 are passed through the second terminal 52 and the first terminal 50, respectively. And supplied to a two-channel high-frequency amplifier 66 to be separately amplified. The output voltage of the measurement differential coil 44 and the output voltage of the magnetic field detection coil 48 amplified by the two-channel high-frequency amplifier 66 are supplied to a two-channel mixer 68, and are respectively frequency-mixed with the oscillation frequency from the oscillator 70. The frequency is converted to an intermediate frequency signal.

The output voltage of the measuring differential coil 44 and the output voltage of the magnetic field detecting coil 48, which have been converted into the intermediate frequency signal, are supplied to a two-channel intermediate frequency amplifier 72 to selectively amplify only the intermediate frequency component. I do. The output voltage of the measuring differential coil 44 and the output voltage of the magnetic field detecting coil 48 amplified by the two-channel intermediate frequency amplifier 72 are output from the two-channel A / D converter and the memory 74.
, And convert the data into digital data separately.
Is temporarily stored in the two-channel A / D converter and the memory of the memory 74 as amplitude data when excited at the oscillation frequency f1 of the _first and second channels, respectively.

The output voltage of the measuring differential coil 44 and the output voltage of the magnetic field detecting coil 48 amplified by the two-channel intermediate frequency amplifier 72 are output from a phase detector and an A / D converter.
And a two-channel intermediate frequency amplifier 72
The output phase of the measurement differential coil 44 amplified by the two-channel intermediate frequency amplifier 72 with reference to the output phase of the magnetic field detection coil 48 amplified by The phase difference from the output phase is detected, extracted as a DC voltage, converted into digital data, and output. In this case, in the A / D conversion, the phase detection output is sampled using a low frequency as a sample pulse and converted into digital data.
The phase detector and A / D converter 76 also functions as a temporary memory.

Two-channel A / D converter and memory 7
4, the output voltage amplitude data of the measurement differential coil 44 and the output voltage amplitude data of the magnetic field detection coil 48,
The phase difference data converted by the phase detector and A / D converter 76 is supplied to the microcomputer 80 via the input / output device 78, and is read into the microcomputer 80.

The microcomputer 80 includes a ROM storing a program, a RAM having a work area, and the like, and is connected to an external memory 82. The microcomputer 80 functions in cooperation with the program stored in the ROM and the external memory 82 to function. The oscillation frequency of the oscillator 60 is set to, for example, 1 MHz every predetermined period.
Oscillation frequency control means 80a that sequentially changes z at a time, for example, when the intermediate frequency is 100 kHz, the oscillator 6
Oscillation frequency of 0 + oscillation frequency of 100 kHz
An oscillation frequency control means 80b for controlling an oscillation frequency of 0;
Attenuator attenuation rate control means 80c in the filter attenuator 62 for attenuating the input level in proportion to the oscillation frequency of the oscillator 60, the two-channel A / D converter and the measuring differential coil 4 stored in the memory 74
4, the output voltage amplitude data of the magnetic field detecting coil 48, the phase detector and the A / D converter 7
6 reads the phase difference data converted in
2 is provided.

Further, the microcomputer 80 functionally stores the output voltage amplitude data of the measurement differential coil 44 in the air-core state stored in the external memory 82 and the measurement differential coil when the sample W is inserted. 44 based on the output voltage amplitude data, the phase difference data of the output voltage of the measurement differential coil 44 in the air-core state, and the phase difference data of the output voltage of the measurement differential coil 44 when the sample W is inserted. Differential coil 44 for inserting sample W
Measurement differential coil 44 in the air-core state from the output voltage of
A vector calculating means for obtaining a corrected output voltage of the differential coil for measurement 44 e by subtracting the output voltage of the differential differential coil 44 from the output voltage of the differential coil for measurement 44. A magnetic permeability calculating means 80f for calculating a ratio to calculate a magnetic permeability is provided.

Further, the microcomputer 80 also has a display control means 80g for controlling the printer / display device 84 as an output means for outputting a result calculated as required, and presenting magnetic permeability and the like. .

The magnetic permeability measuring apparatus 10 according to the present invention is basically configured as described above. Next, its operation and effects will be described.

First, as shown in FIG. 1, a sample W made of a thin plate-like magnetic material is placed on the tip of the sliding member 22 by, for example,
Adhere with cellophane tape. Then, the sliding member 22 is moved toward the printed circuit board 30 along the dovetail groove 20 via the handle 24, and the stopper 26 at the tip end of the sliding member 22 is moved.
When the sample W comes into contact, the sample W enters a state in which the central portion in the longitudinal direction has entered the second space 58 of the printed circuit board 30. Here, the measurement of the magnetic permeability is started.

First, the oscillation frequency of the oscillator 60 is 1 MHz from 1 to 100 MHz by the oscillation frequency control means 80a.
Description will be made on the assumption that the frequency is controlled every z.
Before inserting the sample W, the oscillation frequency control means
The oscillation frequency of the oscillator 60 is 1 MHz, 2 MHz, 3 MHz in synchronization with a predetermined time interval under the control of a and 80 b.
Hz, the oscillation frequency of the oscillator 70 is 1.1 MHz,
Are controlled at 2.1 MHz, 3.1 MHz,.
The attenuation rate of the filter attenuator 62 is controlled so as to be proportional to the reciprocal of the frequency under the control of the attenuation rate control means 80c in synchronization with the change of the oscillation frequency.

If the voltage V detected by each coil is H = A 磁 界 exp jωt (A is an amplitude constant and ω is the angular frequency of the oscillation output of the oscillator 60), V∝dH / d
t = jωH, and the voltage V is proportional to the angular frequency ω. Therefore, the output voltage level of each coil increases in proportion to the angular frequency. Therefore, for example, the voltage at 100 MHz is 100 times higher than that at 1 MHz. Therefore, when the gain of the high-frequency power amplifier 64 is increased, the high-frequency power amplifier 64 is saturated. In order to prevent this, the attenuation rate is controlled. The gain of the high-frequency power amplifier 64 may be controlled instead of controlling the attenuation rate.

The attenuated oscillation output from the oscillator 60 is power-amplified by the high-frequency power amplifier 64 and applied to the exciting coil 28, so that the exciting coil 28 generates an alternating magnetic field. The measurement differential coil 44 and the magnetic field detection coil 48 are linked to the alternating magnetic field, and a voltage is generated from the measurement differential coil 44 and the magnetic field detection coil 48. These two voltages are respectively amplified by a two-channel high-frequency amplifier 66, mixed in frequency with an oscillation frequency signal of an oscillator 70 by a two-channel mixer 68, and converted into an intermediate frequency signal. Here, the intermediate frequency is 100
kHz.

The 100 kHz signal is selectively amplified by the two-channel intermediate frequency amplifier 72 for the two signals converted to the intermediate frequency.
Both amplitude data are digitized separately in the channel A / D converter and the memory 74 so that the two-channel A / D
The data is temporarily stored in the memory of the D converter and the memory 74 corresponding to the oscillation frequency of the oscillator 60.

Further, a phase detector and an A / D converter 76
In the above, the phase difference between the phase of the output voltage of the measuring differential coil 44 and the phase of the output voltage of the magnetic field detecting coil 48 is detected based on the phase of the output voltage of the magnetic field detecting coil 48, and digitized. Output.

Here, the input level of the two-channel high-frequency amplifier 66 is at most 1 mV _PP or less, which is supplied to the input terminals of the two-channel A / D converter and memory 74, the phase detector and the A / D converter 76. A voltage gain of 70 to 80 dB is required to achieve an amplitude level of 1 V _PP , but a two-channel high-frequency amplifier 66 that realizes both an amplitude characteristic and a phase characteristic in a good state in a range of 1 MHz to 100 MHz is realized. Have difficulty. Therefore, in this embodiment, the voltage gain of the two-channel high-frequency amplifier 66 is set to about 40 dB, and the other gains are obtained in the two-channel intermediate frequency amplifier 72.

The above operation is performed every time the oscillation frequency of the oscillator 60 is changed. The amplitude data and the phase difference data of the output voltage of the measuring differential coil 44 are stored in the external memory 82 under the control of the memory control means 80d. It is stored corresponding to the oscillation frequency of the oscillator 60. This is 1MHz at 1MHz intervals
It will be performed over 100 MHz. Therefore, in analog terms, the output voltage E _B2 sin (ωt + θ ₂ ) of the measuring differential coil 44 in the air-core state is stored in the external memory 82 in accordance with the oscillation frequency of the oscillator 60.

Next, the sample W is inserted into one of the coil portions of the measurement differential coil 44, and in a state where the sample W is inserted, the output voltage of the measurement differential coil 44 is The amplitude data and the phase difference data, and the amplitude data of the output voltage of the magnetic field detecting coil 48 are stored in the external memory 82 under the control of the memory control means 80d in accordance with the oscillation frequency of the oscillator 60. This will be done at 1 MHz intervals from 1 MHz to 100 MHz. In this case, the amplitude data of the output voltage of the magnetic field detecting coil 48 is also stored. Therefore, in analog terms, the output voltage E _B1 sin (ωt + θ ₁ ) of the measurement differential coil 44 and the output voltage E _H sin ωt of the magnetic field detection coil 48 with the sample W inserted are generated by the oscillator. The state is stored in the external memory 82 corresponding to the oscillation frequency of 60.

When the process is executed until the oscillation frequency of the oscillator 60 reaches 100 MHz, the amplitude data of the output voltage of the measuring differential coil 44 with the sample W inserted under the control of the correction calculating means 80e. The correction operation is performed by vector subtracting the amplitude data and the phase difference data of the output voltage of the measurement differential coil 44 in the air-core state from the phase difference data. This vector subtraction is performed for each frequency.

If this correction operation is described in analog terms,
It is as follows.

The output voltage of the measuring differential coil 44 with the sample W inserted is E _B1 sin (ωt + θ ₁ ), and the output voltage of the measuring differential coil 44 with the air core is E _B2 sin
(Ωt + θ ₂ ), the output voltage of the magnetic field detecting coil 48 is E
_H sin ωt, and the corrected output voltage of the measurement differential coil 44 with the sample W inserted is expressed as E _B sin (ω
t + θ).

Here, θ ₁ , θ _2, and θ are phases with reference to the output voltage E _H sin ωt of the magnetic field detecting coil 48.

From the above, the correction operation is: E _B sin (ωt + θ) = E _B1 sin (ωt + θ ₁ ) −E _B2 sin (ωt + θ ₂ ).

The left side E _B sin (ωt + θ) is equal to E _B (cos θ
sinωt + sin θ cosωt).

On the other hand, the right side is E _B1 sin (ωt + θ ₁ ) −E _B2 sin (ωt + θ ₂ ) = (E _B1 cos θ ₁ −EB ₂ cos θ ₂ ) sin ωt + (E _B1 sin θ ₁ −E _B2 sin θ ₂ ) cos ωt. Therefore E _B is _{| E B | = √ {E} B1 2 + E B2 2 -2E B1 E B2 cos (θ 1 -θ 2)} , and the phase angle ^{θ θ = tan -1 {(E} B1 sin θ 1 - E _B2 sin θ ₂ ) / (E _B1 cos θ ₁ −E _B2 cos θ ₂ )｝ and is corrected.

Following this correction, the calculation of (E _B / E _H ) is performed under the control of the magnetic permeability calculating means 80f, and the magnetic permeability μ is obtained. This calculation is performed for each frequency. In addition,
If the permeability measuring device 10 is determined and the cross-sectional area of the sample W is always kept constant, (S _H / S _B ) is constant, and this calculation is omitted. By presenting the result of the permeability calculation to the printer / display device 84, the measured permeability can be presented as a table for each frequency or as a graph for the frequency. Further, the phase angle δ between E _B and E _H
= Θ is also calculated, and the real part of the magnetic permeability is calculated from the magnetic permeability | μ | cos δ, and the imaginary part of the magnetic permeability is calculated from | μ | sin δ. Further, the loss (tan δ) is also calculated as (sin δ / cos
δ). These presentations are of course also possible.

Since the measurement in the air-core state and the measurement in the state in which the sample W is inserted are performed every 1 MHz as described above, the stray capacitances of the measuring differential coil 44 and the magnetic field detecting coil 48 and the stray capacitance of the magnetic field detecting coil 48 depend on the frequency. The effect of stray capacitance at the input end of the two-channel high-frequency amplifier 66 can be reduced.

In the above-described embodiment, the measurement is performed from 1 MHz to 100 MHz in the air-core state,
Next, with the sample W inserted, 1 MHz to 100 MHz
Although the case where the measurement up to the above is performed is illustrated, the measurement from 1 MHz to 100 MHz may be performed by alternately measuring the air-core state and the state where the sample W is inserted at the same frequency.

Also, the case where the measurement in the air-core state is performed every 1 MHz has been described as an example, but the measurement in the air-core state is several times the frequency interval of the measurement with the sample W inserted. In some cases, it may be sufficient. In this case, as the amplitude data and the phase difference data of the output voltage of the measurement differential coil 44 in the state of the air-core state, interpolation is performed with the measurement value immediately before the measurement at the next frequency.

[0046]

As described above, according to the present invention, a work can be inserted into a coil for measuring magnetic permeability via a sliding member. In this case, since the substrate for magnetic permeability measurement is composed of a single substrate including the measurement differential coil and the magnetic field detection coil, no dimensional error or the like occurs. Therefore, stable measurement of magnetic permeability can be performed.
In addition, since the sliding member is positioned with respect to the guide member via the stopper, the measurement position is always in a fixed state. Therefore, even when measuring a large number of samples,
A stable measurement-free result is obtained. In addition, since the thin-film magnetic material as a sample is fixed to the sliding member and a fixing portion that can be inserted into the hole is provided, positioning of the sample is easy.

Further, according to the present invention, the output voltage of the measurement differential coil in the air-core state where the magnetic permeability measurement sample is not inserted is changed by the measurement differential coil in the state where the magnetic permeability measurement sample is inserted. The vector is subtracted from the output voltage of the coil and corrected, and the permeability is measured from the ratio of the output voltage of the corrected measurement differential coil and the output voltage of the magnetic field detection coil. Even in the case where the effective areas of the two coil portions forming the measurement differential coil cannot be made equal due to manufacturing restrictions and the like,
This is corrected to be substantially equivalent to the case where the effective areas of the two coil portions forming the measurement differential coil are substantially equalized, and there is an effect that the magnetic permeability can be accurately measured.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view of an apparatus according to an embodiment of the present invention.

FIG. 2 is a perspective view of the device shown in FIG.

FIG. 3 is a front view of a substrate incorporated in the apparatus shown in FIGS. 1 and 2;

FIG. 4 is a rear view of the substrate shown in FIG. 3;

FIG. 5 is a block diagram showing a configuration of one embodiment of the present invention.

FIG. 6 is a perspective view showing a configuration of a detecting unit of the magnetic permeability measuring apparatus to which the present invention is applied.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Permeability measuring apparatus 12 ... Base 16 ... Guide member 18 ... Magnetic detection circuit 22 ... Sliding member 24 ... Handle 28 ... Excitation coil 44 ... Measurement differential coil 48 ... Magnetic field detection coil 50, 52, 54 ... Terminal 60 ... Oscillator 62 ... Filter Attenuator 64 ... High Frequency Power Amplifier 66 ... Two Channel High Frequency Amplifier 68 ... Two Channel Mixer 70 ... Oscillator 72 ... Two Channel Intermediate Frequency Amplifier 74 ... Two Channel A / D Converter and Memory 76 ... Phase Detector and A / D converter 80 Microcomputer 80a, 80b Oscillation frequency control means 80c ... Attenuation rate control means 80d ... Memory control means 80e ... Correction calculation means 80f ... Magnetic permeability calculation means 80g ... Display control means 82 ... External Memory 84: Printer / display device W: Sample

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-7-104044 (JP, A) JP-A-5-264705 (JP, A) JP-A-5-232203 (JP, A) JP-A-4- 19584 (JP, A) JP-A-61-57871 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01R 33/00-33/18

Claims (5)

(57) [Claims] 1. A measuring differential coil comprising: a magnetic field generating coil for generating a substantially uniform alternating magnetic field; a magnetic field detecting coil and a measuring differential coil disposed in the magnetic field generating coil. In a magnetic permeability measuring device for measuring magnetic permeability from an output voltage and an output voltage of a magnetic field detection coil, the magnetic field detection coil and the measurement differential coil are wound around a single substrate. Characteristic permeability measuring device. 2. The magnetic permeability measuring apparatus according to claim 1, wherein
A magnetic permeability measuring device, wherein a hole for sample insertion is formed through a central portion of the measurement differential coil of the substrate. 3. The magnetic permeability measuring apparatus according to claim 2, wherein
A guide member is disposed in close proximity to a sample insertion hole, a slide member is engaged with the guide member, and a sample fixed to the slide member is inserted into the hole. Magnetic susceptibility measurement device. 4. The magnetic permeability measuring apparatus according to claim 3, wherein
A magnetic permeability measuring device, wherein a guide member is provided with a stopper for stopping the sliding member at a predetermined position. 5. A magnetic permeability measuring apparatus according to claim 3, wherein a fixed portion of a thin film magnetic material as a sample is formed on said sliding member.