JPH05264705A - Measuring apparatus for permeability - Google Patents

Abstract

PURPOSE:To provide an apparatus wherein a specimen is always arranged in a definite measur ing position and the permeability of the specimen can be measured surely and quickly so as not to cause a measuring error. CONSTITUTION:The title apparatus is provided with the following: a coil 28, for excitation use, which is installed in a substrate and which generates a nearly uniform alternating magnetic field; a coil 48, for magnetic-field detection use, which is arranged and installed in the coil 28 for excitation use; a differential coil 44 for measurement use; and a sliding and moving member which can be advanced freely into the differential coil 44 for measurement use. A permeability is measured from the following: the output voltage of the differential coil 44 for measurement use when a permeability-measuring specimen is inserted into a coil part one side of the differential coil 44 for measurement use; and the output voltage of the coil 48 for magnetic-field detection use. At this time, the following are used: a correction and operation means 80e which corrects the output voltage of the differential coil 44 for measurement use in an air core state that the permeability-measuring specimen has been inserted by vector-subtracting the output voltage from the output voltage of the differential coil 44 for measurement use in a state that the permeability-measuring specimen has been inserted. The permeability is measured from the ratio of the output voltage of the differential coil 44 for measurement use after its correction to the output voltage of the coil 48 for magnetic-field detection use.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic permeability measuring device capable of obtaining the effective magnetic permeability of a thin film magnetic material at high frequencies and its real part and imaginary part with as few errors as possible.

[0002]

2. Description of the Related Art Heretofore, an inductance method, a yoke method and the like have been used as a method of measuring the magnetic permeability of a magnetic material. With these methods, measurement at high frequencies was difficult because of self-resonance caused by the distributed capacitance of the coil. A magnetic permeability measuring method using a differential coil is known as an alternative method.

The structure of the detecting portion of the magnetic permeability measuring device using a differential coil is disclosed in Japanese Patent Laid-Open No. 61-57871. That is, as shown in FIG. 6, in this magnetic permeability measuring apparatus, a voltage from a high-frequency power source 4 for excitation is applied to a magnetic field generating coil 2 having a rectangular cross section to generate an alternating magnetic field, and the magnetic field generating coil is generated. The magnetic field generating coil 2 so that its surface is orthogonal to the alternating magnetic field generated by
A measurement differential coil 6 and a magnetic field detection coil 8 that are wound in an 8-character shape are provided inside, and a magnetic permeability measurement sample (hereinafter, also 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, and S _B is the cross-sectional area of the sample 9.

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

[0005]

However, in the above-mentioned structure, the dimensional accuracy does not improve so much, and therefore,
As products vary, it is difficult to measure the magnetic permeability accurately.

Moreover, since the magnetic permeability varies depending on the insertion degree of the sample, there is a problem that the measurement result cannot be reliable.

The present invention has been made in order to overcome the above-mentioned inconveniences, and has a simple structure, that is,
It is an object of the present invention to provide a magnetic permeability measuring device which has a small measurement error and can measure the magnetic permeability quickly and which is excellent in dimensional accuracy of a measuring portion.

[0008]

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 device disposed in the magnetic field generating coil. In the magnetic permeability measuring apparatus, which comprises a measuring coil and a measuring differential coil, and measures the magnetic permeability from the output voltage of the measuring differential coil and the output voltage of the magnetic field detecting coil, the magnetic field detecting coil and the measuring differential The coil is characterized in that it is wound around a single substrate.

[0009]

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

[0010]

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

In FIG. 1, reference numeral 10 indicates a magnetic permeability measuring apparatus according to the present invention. This magnetic permeability measuring device 10
Is basically the base 12 and the bolts 14 on the base 12.
Member 16 fixed by the guide member 16 and the guide member 16
And a magnetic detection circuit 18 facing the above.

As is easily understood from FIG. 1, the guide member 16 is provided with a dovetail groove 20 along the longitudinal central portion thereof, and a sliding member 22 is slidable in the dovetail groove 20. It is fitted. The tip portion of the sliding member 22 is used as a fixed portion of the sample W. In this case, a handle 24 is provided to displace the sliding member 22. The reference numeral 26 indicates a stopper for preventing further displacement of the sliding member 22 provided at one end of the dovetail groove 20.

The guide member 16 faces the magnetic detection circuit 18. The magnetic detection circuit 18 includes an exciting coil 28 formed by bending on a 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 the output of an 8-shaped coil (described later) provided on the printed circuit board 30 to the outside.
Composed of and.

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

3 and 4 show the wiring structure of the printed circuit board 30. As shown in FIG. As is easily understood from FIG. 3, one conductor 42 is curved or bent in a substantially 8-shape on one surface of the printed circuit board 30 to form a measurement differential coil 44. As shown in FIG.
The conductor 46 is curved or bent on the other surface of the above to form a magnetic field detection coil 48. Differential coil 44 for measurement
The output side of the first terminal 50
The output side of the magnetic field detection 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 figure, reference numerals 56a and 56b indicate through holes, reference numeral 57 indicates a rectangular first space defined on the printed circuit board 30, and reference numeral 58 indicates the first space. 57 shows a second space defined below 57 for sample insertion.

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

The magnetic permeability measuring apparatus 10 is provided with an oscillator 60 as a high frequency power source for generating a magnetic field, and an oscillation output from the oscillator 60 is supplied to a filter attenuator 62 for waveform shaping and a level of the oscillator 60. It is attenuated in proportion to the oscillation frequency, supplied to the high frequency power amplifier 64 for power amplification, 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, which are 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. Are supplied to a 2-channel high frequency amplifier 66, and are individually amplified. The output voltage of the measurement differential coil 44 and the output voltage of the magnetic field detection coil 48 amplified by the 2-channel high frequency amplifier 66 are supplied to the 2-channel mixer 68 and mixed with the oscillation frequency from the oscillator 70. The frequency is converted into 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. To do. The output voltage of the measurement differential coil 44 and the output voltage of the magnetic field detection coil 48 amplified by the 2-channel intermediate frequency amplifier 72 are the 2-channel A / D converter and the memory 74.
To the oscillator 60 and convert it into digital data separately.
Are temporarily stored in the memory of the 2-channel A / D converter and the memory 74 as amplitude data when excited at the oscillation frequency f ₁ .

The output voltage of the measuring differential coil 44 and the output voltage of the magnetic field detecting coil 48 amplified by the 2-channel intermediate frequency amplifier 72 are the phase detector and the A / D.
The two-channel intermediate frequency amplifier 72 is supplied to the converter 76.
The output phase of the measurement differential coil 44 amplified by the 2-channel intermediate frequency amplifier 72 and the magnetic field detection coil 48 amplified by the 2-channel intermediate frequency amplifier 72 with reference to the output phase of the magnetic field detecting coil 48 amplified by The phase difference from the output phase of is detected, extracted as a DC voltage, converted to digital data, and output. In this case, the A / D conversion uses the low frequency as the sample pulse to sample the phase detection output and convert it into digital data.
The phase detector and A / D converter 76 also function as a temporary memory.

2-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, which are stored in FIG.
The phase difference data converted by the phase detector and the A / D converter 76 is supplied to the microcomputer 80 via the input / output device 78 and is read by the microcomputer 80.

The microcomputer 80 includes a ROM storing a program, a RAM having a work area, etc., and is connected to an external memory 82. In cooperation with the program stored in the ROM and the external memory 82, the microcomputer 80 functionally functions. The oscillation frequency of the oscillator 60 is set to, for example, 1 MH every predetermined period.
When the oscillation frequency control unit 80a that sequentially changes by z and the intermediate frequency is, for example, 100 kHz, the oscillator 6
Oscillator 7 to the oscillation frequency of 0 + the oscillation frequency of 100 kHz
Oscillation frequency control means 80b for controlling the 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 measurement differential coil 4 stored in the memory of the 2-channel A / D converter and the memory 74.
4 output voltage amplitude data and magnetic field detection coil 48 output voltage amplitude data, phase detector and A / D converter 7
The phase difference data converted in 6 is read and the external memory 8
2 is provided with a memory control means 80d.

Further, the microcomputer 80 functionally stores the output voltage amplitude data of the measurement differential coil 44 stored in the external memory 82 in the air-core state and the measurement differential coil when the sample W is inserted. 44 based on the output voltage amplitude data, the output voltage phase difference data of the measurement differential coil 44 in the air-core state, and the measurement differential coil 44 output voltage phase difference data when the sample W is inserted. , Differential coil 44 for measurement when inserting the sample W
Differential coil 44 from the output voltage of
Of the corrected output voltage of the measuring differential coil 44 and the corrected output voltage of the magnetic field detecting coil 48. A magnetic permeability calculating unit 80f for calculating the ratio to calculate the magnetic permeability is provided.

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

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

First, as shown in FIG. 1, a sample W made of a thin plate-shaped magnetic material is attached to the tip of the sliding member 22, for example, as shown in FIG.
Stick it with cellophane tape. Then, the sliding member 22 is moved along the dovetail groove 20 toward the printed circuit board 30 via the grip 24, and the stopper 26 at the tip of the sliding member 22 is moved.
When the sample W comes into contact, the center portion of the sample W in the longitudinal direction enters the second space 58 of the printed circuit board 30. Here, the measurement of 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.
It is assumed that the frequency is controlled every z.
Before inserting the sample W, the oscillation frequency control means 80 in an air-core state
Under the control of a and 80b, the oscillation frequency of the oscillator 60 is 1MHz, 2MHz, 3M in synchronization with each predetermined time interval.
, The oscillation frequency of the oscillator 70 is 1.1 MHz,
Oscillator 60 controlled to 2.1 MHz, 3.1 MHz ...
In synchronism with the change of the oscillation frequency, the attenuation factor of the filter attenuator 62 is controlled so as to be proportional to the reciprocal of the frequency under the control of the attenuation factor control means 80c.

The voltage V detected by each coil is V∝dH / d, where H = Aexp jωt (A is an amplitude constant, ω is the angular frequency of the oscillation output of the oscillator 60).
Since t = jωH, 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, when the frequency is 100 MHz, the voltage is 100 times higher than that in the case of 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. Instead of controlling the attenuation rate, the gain of the high frequency power amplifier 64 may be controlled.

The oscillated output from the attenuated oscillator 60 is power-amplified by the high-frequency power amplifier 64 and applied to the exciting coil 28 to generate an alternating magnetic field by the exciting coil 28. The measurement differential coil 44 and the magnetic field detection coil 48 are linked to this alternating magnetic field, and a voltage is generated from the measurement differential coil 44 and the magnetic field detection coil 48. The two voltages are respectively amplified by a 2-channel high frequency amplifier 66, frequency-mixed with an oscillation frequency signal of an oscillator 70 by a 2-channel mixer 68, and converted into an intermediate frequency signal. Here, the intermediate frequency is 100
kHz.

The two signals converted to the intermediate frequency are each selectively amplified by a 2-channel intermediate frequency amplifier 72 at a signal of 100 kHz, and the amplified intermediate frequency signals are converted into two signals.
Channel A / D converter and memory 74 digitize them separately, and both amplitude data are converted into 2 channels A / D.
It is temporarily stored in the memory of the D converter and the memory 74 in correspondence with the oscillation frequency of the oscillator 60.

Further, the phase detector and A / D converter 76
, The phase difference between the phase of the output voltage of the measurement differential coil 44 and the phase of the output voltage of the magnetic field detection coil 48 is phase-detected and digitized with reference to the phase of the output voltage of the magnetic field detection coil 48. Is output.

Here, the input level of the 2-channel high-frequency amplifier 66 is 1 mV _PP or less at the most, and this is set at the input ends of the 2-channel A / D converter and memory 74, the phase detector and A / D converter 76. To obtain an amplitude level of 1 V _PP , a voltage gain of 70 to 80 dB is required, but a 2-channel high frequency amplifier 66 that realizes good amplitude characteristics and phase characteristics in the range of 1 MHz to 100 MHz is realized. Have difficulty. Therefore, in this embodiment, the voltage gain of the 2-channel high frequency amplifier 66 is set to about 40 dB, and other gains are obtained in the 2-channel intermediate frequency amplifier 72.

The above operation is performed every time the oscillation frequency of the oscillator 60 is changed, and 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 1 MHz at 1 MHz intervals
It will take place over 100 MHz. Therefore, in analogy, the output voltage E _B2 sin (ωt + θ ₂ ) of the measurement differential coil 44 in the air-core state is stored in the external memory 82 in correspondence with the oscillation frequency of the oscillator 60.

Next, the sample W is inserted into one coil portion of the measurement differential coil 44, and in the state where the sample W is inserted, the output voltage of the measurement differential coil 44 is measured in the same manner as above. The amplitude data and the phase difference data and the amplitude data of the output voltage of the magnetic field detection coil 48 are stored in the external memory 82 in correspondence with the oscillation frequency of the oscillator 60 under the control of the memory control means 80d. This will be done at 1 MHz intervals from 1 MHz to 100 MHz. In this case, amplitude data of the output voltage of the magnetic field detection coil 48 is also stored. Therefore, in terms of analog, 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 oscillators. Corresponding to the oscillation frequency of 60, the state is stored in the external memory 82.

When it is executed until the oscillation frequency of the oscillator 60 reaches 100 MHz, the amplitude data of the output voltage of the measurement differential coil 44 with the sample W inserted under the control of the correction calculation means 80e. The correction calculation 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 and the phase difference data. This vector subtraction is performed for each frequency.

If this correction calculation is explained in an analog manner,
It is as follows.

The output voltage of the measurement differential coil 44 with the sample W inserted is E _B1 sin (ωt + θ ₁ ), and the output voltage of the measurement differential coil 44 with the air-core state is E _B2 sin.
(Ωt + θ ₂ ), the output voltage of the magnetic field detection coil 48 is E
_H sin a .omega.t, the corrected output voltage of the measuring differential coil 44 in a state where the sample W is inserted 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 calculation 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 E _B (cos θ
It can be written as sin ωt + sin θ cos ωt).

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 −E _B2 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 is θ = tan ⁻¹ {(E _B1 sin θ ₁ − E _B2 sin θ ₂ ) / (E _B1 cos θ ₁ −E _B2 cos θ ₂ )}, which is corrected.

Subsequent to this correction, under the control of the magnetic permeability calculating means 80f, (E _B / E _H ) is calculated to obtain the magnetic permeability μ. This calculation is performed for each frequency. In addition,
Sadamari permeability measuring device 10, if the cross-sectional area of the sample W always constant (S _H / S _B) is constant, this operation is omitted. By presenting the result of this magnetic permeability calculation to the printer / display device 84, the measured magnetic permeability can be presented as a table for each frequency or as a graph with respect to frequency. Furthermore, 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. Furthermore, the loss (tan δ) is also (sin δ / cos
Calculated from δ). Of course, these presentations are also possible.

As described above, in order to perform the measurement in the air-core state and the measurement in the inserted state of the sample W every 1 MHz, the stray capacitance of the measurement differential coil 44 and the magnetic field detection coil 48 depends on the frequency and It is possible to reduce the influence of the stray capacitance at the input end of the 2-channel high frequency amplifier 66.

In the above-mentioned embodiment, the measurement from 1 MHz to 100 MHz is performed in the air-core state,
Next, with the sample W inserted, 1 MHz to 100 MHz
However, the measurement from 1 MHz to 100 MHz may be performed by alternately measuring the time in the air-core state and the state in which the sample W is inserted at the same frequency.

Although the case where the measurement in the air-core state is performed every 1 MHz is illustrated, the measurement in the air-core state is performed at a frequency interval several times that of the measurement in the state where the sample W is inserted. In some cases, it may be enough. In this case, the amplitude data and the phase difference data of the output voltage of the measuring differential coil 44 in the air-core state are interpolated by the immediately preceding measured value until the measurement at the next frequency.

[0046]

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

Further, according to the present invention, the output voltage of the measuring differential coil in the air-core state in which the magnetic permeability measuring sample is not inserted is determined by measuring the output voltage of the measuring differential coil in the state in which the magnetic permeability measuring sample is inserted. The vector is subtracted from the output voltage of the coil for correction, and the magnetic permeability is measured from the ratio of the corrected output voltage of the measurement differential coil and the output voltage of the magnetic field detection coil. Even when the effective areas of the two coil portions forming the measurement differential coil cannot be formed equal due to manufacturing restrictions or the like,
This is equivalent to being corrected so that the effective areas of the two coil portions forming the differential coil for measurement are substantially equalized, and the magnetic permeability can be accurately measured.

[Brief description of drawings]

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

2 is a perspective view of the device shown in FIG. 1. FIG.

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

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

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

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

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Permeability measuring device 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 coils 50, 52, 54 ... Terminal 60 ... Oscillator 62 ... Filter / Attenuator 64 ... High-frequency power amplifier 66 ... 2-channel high-frequency amplifier 68 ... 2-channel mixer 70 ... Oscillator 72 ... 2-channel intermediate frequency amplifier 74 ... 2-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 ... Permeability calculation means 80g ... Display control means 82 ... External Memory 84 ... Printer / display device W ... Sample

Claims (5)

[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 arranged in the magnetic field generating coil. In a magnetic permeability measuring device that measures 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 may be wound on a single substrate. Characteristic permeability measuring device. 2. The magnetic permeability measuring device according to claim 1,
A magnetic permeability measuring device, characterized in that a hole for sample insertion is defined by penetrating a central portion of the measuring differential coil of the substrate. 3. The magnetic permeability measuring device according to claim 2, wherein
A guide member is disposed close to the sample insertion hole, and a sliding member is engaged with the guide member to insert the sample fixed to the sliding member into the hole. Magnetic susceptibility measuring device. 4. The magnetic permeability measuring device according to claim 3,
A magnetic permeability measuring device, wherein a guide member is provided with a stopper for stopping the sliding member at a predetermined position. 5. The magnetic permeability measuring apparatus according to claim 3 or 4, wherein a fixed portion of a thin film magnetic material as a sample is formed on the sliding member.