JPH06281712A - Magnetic field sensor - Google Patents

Abstract

PURPOSE:To detect the external magnetic field approaching in the longitudinal direction of an amorphous magnetic material wire while an alternating rotating magnetic field is allowed to be generated by applying high-frequency current directly without winding a detection coil on the amorphous magnetic material wire. CONSTITUTION:The sensor is provided with a magnetic core 1 for detection, which is made of an amorphous magnetic material wire, and a conversion circuit 2, and which generates an alternating rotating magnetic field in the core 1 by which the change in rotating magnetic field based on the external magnetic field in the longitudinal direction of the core 1 is converted into an electric signal by applying high-frequency current in the longitudinal direction of the core 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention uses a magnetic field sensor, in particular, an amorphous magnetic wire as a detection element, and a high-frequency wave is directly applied to the amorphous magnetic wire without winding a winding for detection around the amorphous magnetic wire. The present invention relates to a magnetic field sensor configured to detect an external magnetic field applied to the amorphous magnetic wire by applying a current.

[0002]

2. Description of the Related Art As a conventional magnetic field (magnetic) sensor of this type, a fluxgate type has been put into practical use and is widely commercially available.

29 to 32 show the detecting portion thereof. In FIG. 29, an external current is detected by applying an alternating current to a detecting coil 101 wound around a magnetic core 100 ( JP-A-2-162276), FIG.
At 0, while supplying alternating current to both ends of the magnetic core 100,
A bias current is supplied to the detection coil 101 wound around the magnetic core 100 to detect an external magnetic field (Japanese Patent Laid-Open No. Hei 1-163686). A magnet 102 as a magnetic source is arranged to improve the sensitivity (Japanese Patent Laid-Open No. 52-
32, the feedback coil 103 is further wound on that of FIG. 30 to improve the linearity, and the feedback current is applied to the feedback coil 103 to improve the sensitivity.

FIG. 28 shows a detection circuit used at this time.
An astable multivibrator such as that shown in Figure 1 was used. In the figure, La and Lb are the detection units described in FIGS. 29 to 32, and represent the detection coils 101 of these detection units. La and L in FIG. 28
The difference in the magnitude of the external magnetic field applied to b is given by OUTa and O
It is detected by the voltage difference from UTb.

[0005]

However, in the conventional magnetic field sensor using the detecting section and the detecting circuit described above,
In the detection unit, the detection coil 101 is provided around the magnetic core 100.
It has the drawback that it cannot be miniaturized because it is wound, and its detection circuit uses transistors Qa and Qb that require time to recover the reverse bias voltage applied to the base, so the response speed is limited and it is practically used. It has a drawback that only an alternating magnetic field of 1 kHz or less can be detected.

Some magnetic field measuring devices use a Hall element in the detecting portion, but these devices also have a frequency of 50 kHz.
However, there was a drawback that the stability was not good for the maximum price. The present invention aims to solve the above drawbacks,
A high-speed response that can measure the external magnetic field at a high speed with a structure that does not have a detection coil wound around the magnetic core used in the detection unit and that can detect an external magnetic field, and is capable of measuring sufficiently in response to the speeding up of the phenomenon under test. An object of the present invention is to provide a magnetic field sensor having properties.

[0007]

FIG. 1 is an explanatory view of the principle configuration of the present invention. In the figure, 1 is a magnetic core for detection,
A linear amorphous magnetic alloy material having conductivity is used as the detection magnetic core. Reference numeral 2 is a conversion circuit, for example, a self-excited oscillation circuit is used, and the high frequency current is directly supplied from the conversion circuit 2 to the detection magnetic core 1.

As shown in FIG. 4, when a high-frequency alternating current Iac is passed through an amorphous magnetic wire having a radius a and a length l, a circumferential magnetic flux H.theta. φθ changes. Therefore, an induced voltage e _L = ∂φθ / ∂t appears across the amorphous magnetic wire. However, since the ohmic voltage e _R = Rw Iac (Rw is the electrical resistance of the amorphous magnetic alloy wire) also appears at the both ends of the amorphous magnetic wire, the total voltage e _tot
Is

[0009]

[Equation 1]

[0010] Here, since the ohmic voltage e _R can be canceled by a bridge circuit or the like, and noting the aforementioned induced voltage e _L, it becomes the induced voltage e _L as follows expressed in a high frequency alternating current Iac.

The circumferential magnetic field Hθ is expressed by the distance γ in the radial direction of the amorphous magnetic wire,

[0012]

[Equation 2]

It is represented by Let Iac be Iac = Im sin ωt

[0014]

[Equation 3]

[0015] Here, the relationship between the circumferential magnetic flux density Bθ and Hθ is calculated by taking into account the nonlinearity and the loss by the following equation (4).
It is represented by.

[0016]

[Equation 4]

Here, β is a damping coefficient by eddy current damping and spin relaxation of domain wall movement in the circumferential direction, and Hc is a coercive force in the circumferential direction. In order to analytically solve the equation of Equation 4, B = B
Using m sin (ωt − ψ) and the placement description function method, the following Equation 5 is obtained.

[0018]

[Equation 5]

From the equation (5), the incremental magnetic permeability in the circumferential direction μθ
Is expressed by the following equation (6).

[0020]

[Equation 6]

Therefore, the circumferential magnetic flux φθ is

[0022]

[Equation 7]

Assuming that μθ does not depend on γ,

[0024]

[Equation 8]

Here, Ic = 4πa Hc. Therefore, the induced voltage e _L is

[0026]

[Equation 9]

Represented by [0027], the amplitude of e _L | e _L | it is expressed by the number 10 in the following equation.

[0028]

[Equation 10]

Therefore, the linearized inductance L of the amorphous magnetic wire is

[0030]

[Equation 11]

When a high frequency current is applied to the detecting magnetic core 1,
An alternating rotating magnetic field is generated around the detection magnetic core 1 inside and outside the detection magnetic core 1. When an external magnetic field extending in the longitudinal direction of the detecting magnetic core 1 is applied to the alternating rotating magnetic field, the magnetic flux intersecting the detecting magnetic core 1 based on the high frequency current is changed, and the induced voltage generated at both ends of the detecting magnetic core 1 is changed. e _L changes. Further, the linear inductance L represented by the number 11 of the magnetic core 1 for detection changes.

The conversion circuit 2 rectifies and takes out the change in the induced voltage e _L , or changes the change in the inductance L into a change in the frequency, the duty ratio of the period or the signal level and takes out the change as an electric signal. ing.

FIG. 2 is an explanatory view of another principle configuration of the present invention. In the figure, the conversion circuit 2 includes an excitation unit 2-1 and a detection circuit unit 2-2, and a high frequency current is supplied from the excitation unit 2-1 to the detection magnetic core 1. Then, when an external magnetic field is applied in the longitudinal direction of the detection magnetic core 1, the detection circuit section 2-2 detects a voltage change or a waveform change of the induced voltage e _L generated in the detection magnetic core 1, and the electric signal thereof is detected. It is designed to output.

FIG. 3 is an explanatory view of another principle configuration of the present invention. In the figure, a plurality of, for example, two detection magnetic cores 1 are used, one of them is used as a reference, and the remaining one of the changes in the linear inductance L is converted by the conversion circuit 2 into the frequency of the electric signal, the duty ratio of the cycle, or It is designed to be extracted as a change in signal level.

In this case, an external magnetic field is applied to the reference detecting magnetic core 1 so as to be perpendicular to its longitudinal direction, and an external magnetic field is applied to the other detecting magnetic cores 1 in its longitudinal direction. Is arranged as.

As described above, the amorphous magnetic wire is used as the detecting magnetic core 1 shown in FIGS. 1 to 3,
The amorphous magnetic wire is more suitable for high frequencies than others.

Then, for example, one amorphous magnetic wire having a diameter of 0.1 mm and a length of 10 mm has an inductance value of several μH and a change amount of several tens%. When this is incorporated into self-oscillation and oscillated, the capacitance component is extremely small,
Moreover, since the value of the inductance is as small as several μH / 10 mm, a high frequency can be easily obtained by oscillating.

A feature of the present invention is that a high-frequency current is directly applied to the amorphous magnetic wire. Next, the structure of the detection magnetic core used in the present invention will be described.

FIG. 5 shows an external magnetic field detected by supplying an alternating current to the amorphous magnetic wire 3, and shows a state in which the amorphous magnetic wire 3 is mainly incorporated in a self-excited oscillation circuit or the like for use. The change in the inductance L is used.

In FIG. 6, an alternating current is supplied to the amorphous magnetic material line 3 to detect an external magnetic field, and the change in the voltage or the voltage waveform generated at both ends of the amorphous magnetic material line 3 is mainly used.

In FIG. 7, an alternating current is supplied to the amorphous magnetic wire 3 to detect an external magnetic field, but a magnet 4 as a magnetic source is provided outside the amorphous magnetic wire 3 to improve the sensitivity. Is. The change in voltage or voltage waveform generated at both ends of the amorphous magnetic wire 3 is mainly used.

In FIG. 8, an alternating current is supplied to the amorphous magnetic material wire 3 to detect an external magnetic field, but a feedback coil 5 is provided around the amorphous magnetic material wire 3 to improve linearity. At this time, the feedback current is applied to the feedback coil 5, so that the sensitivity is also improved. The change in voltage or voltage waveform generated at both ends of the amorphous magnetic wire 3 is mainly used.

As a method for detecting the external magnetic field with high sensitivity,
The structure may be such that the amorphous magnetic wire 3 of FIGS. 5 to 8 and ferrite beads for collecting magnetic flux are combined.

FIGS. 9 to 12 correspond to FIGS. 5 to 8, respectively, in which each amorphous magnetic wire 3 is covered with a ferrite bead 6 for collecting magnetic flux. The apparent inductance of is increased and the sensitivity is improved.

[0045]

When an external magnetic field is applied in the longitudinal direction of the detection magnetic core 1 to which the high frequency current is supplied, the alternating magnetic field based on the high frequency current changes, and the magnetic flux intersecting the detection magnetic core 1 also changes. It is assumed that the detection magnetic core 1 is in a magnetically saturated state. Therefore, the terminal voltage generated across the detection magnetic core 1 changes, and the inductance of the detection magnetic core 1 also changes.

The external magnetic field can be detected by converting the voltage change and the inductance change into an electric signal that is easy to measure.

[0047]

FIG. 13 shows a basic configuration of an embodiment of a magnetic field sensor using an inductance type astable multivibrator according to the present invention.

In the figure, the detection magnetic core 1 shown in FIG. 5 or 9 is used for WLa and WLb, and field effect transistors (FET transistors) Qa and Qb are used as switching elements.

The FET transistor is used as the switching element when the FET transistors Qa and Qb are reverse-biased, and the depletion type that requires a short recovery time to operate even if reverse-biased is used. This makes it possible to operate at high speed up to 200 MHz.

A bias voltage circuit 7 is a circuit for supplying a voltage for operating the FET transistors Qa and Qb. The output is taken as a change in voltage or a change in frequency between the terminals A and B or between the -V line and the terminal A or B.

Oscillation is caused by the inductance WLa of the detection magnetic core.
, WLb, the capacitors Cga, Cgb are charged and discharged based on the magnetic energy stored in the FET transistors Q,
It is performed by repeatedly controlling a and Qb to be alternately turned on and off. That is, the detection magnetic core is in a state in which an alternating current is supplied.

When the magnetic flux from the external magnetic field is applied to the inductance of the detection magnetic core, the value of the inductance of the detection magnetic core changes and the accumulated magnetic energy changes as described above. This changes the on / off time of the FET transistors Qa and Qb.

FIG. 14 is a diagram for explaining the principle waveform when only one inductance changes. In the output waveform of the FET transistor Qa, the on-time is Δt1 as shown by the dotted line in the figure from the state of the solid line in the figure. Becomes longer. The off time corresponds to the on time of the FET transistor Qb, and the on time of the FET transistor Qb is always constant, but the ratio of the on time to the off time changes,
The cycle also changes.

When both inductances change, for example, the ON time of the FET transistor Qa is Δt1.
It becomes longer, and the ON time of the FET transistor Qb is Δt2.
When it becomes longer, the off time of the FET transistor Qa becomes Δt.
2 becomes longer, and the entire cycle becomes longer than before the inductance changes by Δt1 + Δt2 hours.

If this principle is used, for example, the magnetic field generated by the current flowing in one conductor is arranged so as to change both of the above inductances, and the period (Δ
It is also possible to detect t1 + Δt2) and measure the magnitude of the current flowing through the conductor.

In this way, the inductance WL of the magnetic core for detection is
When an external magnetic field is applied to a and WLb in the longitudinal direction,
The oscillation cycle and the on / off time ratio of the circuit shown in FIG. 13 change. Therefore, the average current flowing through the FET transistors Qa and Qb changes, and a potential difference appears between the terminals A and B. That is, the inductances WLa, W of the magnetic core for detection
The difference in the magnitude of the magnetic field applied to Lb can be taken out as an electrical signal (averaged DC voltage or pulse) between terminals A and B.

The output signal can also be taken out between the -V line and the terminal A or B. FIG. 16 shows the configuration of a specific embodiment of the magnetic field sensor according to the present invention. Figure 1
6, the bias voltage circuit 7 of FIG. 13 is composed of a resistor RO and a capacitor CO, and the other parts are the same as those of FIG.

Detecting magnetic core inductances WLa, WL
b is orthogonal to the cross, and the wire of the inductance WLb of the detection magnetic core orthogonal to the cross is made to coincide with the central axis of the Helmholtz coil 8 shown in FIG.

When a current is supplied from the DC power supply 9 to the Helmholtz coil 8, a uniform magnetic field is generated at the center of the Helmholtz coil 8, and this magnetic field becomes an external magnetic field in the longitudinal direction of the wire of the inductance WLb. At this time, the external magnetic field is vertically applied to the wire of the other inductance WLa.

Now, as the wires of the inductances WLa and WLb, unitika amorphous magnetic substance wire DC-2T having a diameter of 100φ and a length of 4 cm is used to perform an experiment in the circuit of FIG. 16, and the results are shown in FIGS. The output result was obtained.

The output voltage on the vertical axis is obtained from between terminals A and B in FIG. Output is 0 mV according to the experimental results in FIG.
At this time, a current of about 60 mA is flowing in the Helmholtz coil 8, which is presumed to be due to the influence of the earth's magnetism.

From FIG. 18 and FIG. 19, the Helmholtz coil 8
When the current flowing through the coil exceeds 60 mA, the output voltage is the current flowing through the Helmholtz coil 8, that is, the inductance WLb.
It can be seen that it is almost proportional to the external magnetic field applied to the wire in the longitudinal direction.

20 to 22 show drain waveforms of the FET transistor Qa, and FIG. 20 shows that no current flows through the Helmholtz coil 8 and that 0.3 gauss of the earth's magnetism is applied in the longitudinal direction of the wire of the inductance WLb. 21 is when the current is applied to the Helmholtz coil 8 to cancel out the geomagnetism of 0.3 Gauss, and FIG. 22 is when the current is applied to the Helmholtz coil 8,
This is when an external magnetic field of 2 Gauss is applied in the longitudinal direction of the wire of the inductance WLb.

It can be seen from FIGS. 20 to 22 that the value of the inductance WLb is changed by the external magnetic field and thus the oscillation frequency is changed. In the figure, the waveform is not rectangular but sinusoidal because the waveform is distorted due to high speed.

FIG. 23 shows a gate waveform of the FET transistor Qa, which is obtained when an external magnetic field of 2 Gauss is applied in the longitudinal direction of the wire of the inductance WLb similar to that in FIG.

FIG. 24 shows the gate waveform and the source waveform of the FET transistor Qa, and the measurement conditions are the same as in the case of FIG. 25 to 27 show drain waveforms of the FET transistors Qa and Qb, and the measurement condition is that an external magnetic field is applied also in the longitudinal direction of the wire of the inductance WLa.
This is when the values of WLb are made equal.
At this time, it is understood that the on times of the FET transistors Qa and Qb are equal. FIG. 26 shows the case where the value of the inductance WLa is made larger than the value of the inductance WLb. It can be seen that the on-time of the FET transistor Qa at this time is smaller than the on-time of the FET transistor Qb. FIG. 27 shows the case where the value of the inductance WLa is smaller than the value of the inductance WLb. It can be seen that the on-time of the FET transistor Qa at this time is longer than the on-time of the FET transistor Qb.

That is, it can be seen that the ratio of the on-time to the off-time of the FET transistors Qa and Qb is changed by the change of the inductances WLa and WLb, and the oscillation cycle is changed. FIG. 17 shows the configuration of another specific embodiment of the magnetic field sensor according to the present invention.

In FIG. 17, the bias voltage circuit 7 of FIG. 13 is composed of a Zener diode ZdO and a capacitor CO, and the other parts are the same as those of FIG. In the inductance type astable multivibrator shown in FIGS. 13, 16 and 17, since the FET transistors Qa and Qb are used as switching elements, the FET transistors Qa and Qb shown in FIG. 13 are operated to operate. The bias voltage circuit 7 is incorporated, and the output signal is rectified and taken out by the bias voltage circuit 7. The magnetic field sensor of the present invention has an excellent feature that a new rectifier circuit, which is difficult to accurately rectify and take out a high-frequency signal, is not newly required, and therefore requires a small number of circuit components.

By connecting a diode or a capacitor between the drain and source of each of the FET transistors Qa and Qb, the gain is increased, and further high speed operation becomes possible.

By using the magnetic field sensor of the present invention,
It can be used for high-speed response current sensor and high-speed displacement sensor.

[0071]

As described above, according to the present invention, since there is no detection coil, 1) the magnetic core can be made smaller, the detection unit can be made smaller, and 2) the capacitance component contained in the coil is almost eliminated. Since it does not exist, high-speed response is improved, and it becomes a magnetic field sensor with an excellent response speed. 3) It is possible to shorten the work process and cost of the magnetic field sensor.

[Brief description of drawings]

FIG. 1 is a diagram illustrating the principle configuration of the present invention.

FIG. 2 is a diagram illustrating another principle configuration of the present invention.

FIG. 3 is a diagram illustrating another principle configuration of the present invention.

FIG. 4 is an explanatory diagram for calculating the inductance of an amorphous magnetic wire.

FIG. 5 is a structural diagram of an embodiment of a detection magnetic core used in the present invention.

FIG. 6 is a structural diagram of another embodiment of the magnetic core for detection used in the present invention.

FIG. 7 is a structural diagram of another embodiment of the magnetic core for detection used in the present invention.

FIG. 8 is a structural diagram of another embodiment of the magnetic core for detection used in the present invention.

FIG. 9 is a structural diagram of another embodiment of the magnetic core for detection used in the present invention.

FIG. 10 is a structural diagram of another embodiment of the magnetic core for detection used in the present invention.

FIG. 11 is a structural diagram of another embodiment of the magnetic core for detection used in the present invention.

FIG. 12 is a structural view of another embodiment of the magnetic core for detection used in the present invention.

FIG. 13 is a basic configuration of an embodiment of a magnetic field sensor using the inductance type astable multivibrator according to the present invention.

FIG. 14 is a principle waveform explanatory diagram when only one inductance changes.

FIG. 15 is an explanatory diagram of external magnetic field generation.

FIG. 16 is a specific example configuration of a magnetic field sensor according to the present invention.

FIG. 17 is a configuration of another specific example of the magnetic field sensor according to the present invention.

FIG. 18 is an output characteristic test result diagram of the example of the present invention.

FIG. 19 is a graph showing the output characteristic test results of another embodiment of the present invention.

FIG. 20 is a drain waveform diagram of the FET transistor Qa.

FIG. 21 is a drain waveform chart of the FET transistor Qa.

FIG. 22 is a drain waveform diagram of the FET transistor Qa.

FIG. 23 is a gate waveform diagram of the FET transistor Qa.

FIG. 24 is a gate and source waveform diagram of the FET transistor Qa.

FIG. 25 is a drain waveform diagram when the inductance values are the same.

FIG. 26 is a drain waveform diagram when the inductance values are different.

FIG. 27 is a drain waveform diagram when the inductance value is opposite to that in FIG. 26.

FIG. 28 is a circuit diagram of a conventional inductance type multivibrator.

FIG. 29 is a structural diagram of a detection magnetic core used in a conventional magnetic field sensor.

FIG. 30 is another structural diagram of the detection magnetic core used in the conventional magnetic field sensor.

FIG. 31 is another structural diagram of a detection magnetic core used in a conventional magnetic field sensor.

FIG. 32 is another structural diagram of a detection magnetic core used in a conventional magnetic field sensor.

[Explanation of symbols]

 1 Magnetic Core for Detection 2 Conversion Circuit 2-1 Excitation Section 2-2 Detection Circuit Section 3 Amorphous Magnetic Wire 6 Ferrite Beads

─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] April 7, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0004

[Correction method] Change

[Correction content]

An astable multivibrator as shown in FIG. 28 has been used as the detection circuit used in FIGS. 29 to 32 . In the figure, La and Lb
Are the detection units described in FIGS. 29 to 32, and each detection coil 101 of these detection units is shown. FIG. 28
The difference in the magnitudes of the external magnetic fields applied to La and Lb in the above is detected by the difference in the voltage between OUTa and OUTb.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0038

[Correction method] Change

[Correction content]

A feature of the present invention is that a high-frequency current is directly applied to the amorphous magnetic wire. Next, the detection mode of the external field using the detection magnetic core used in the present invention will be described.
It described Te.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0046

[Correction method] Change

[Correction content]

The external magnetic field can be detected by converting the change in the voltage and the voltage waveform and the change in the inductance into an electric signal that can be easily measured.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0050

[Correction method] Change

[Correction content]

Reference numeral 7 denotes a bias voltage circuit, which supplies a voltage for shifting the FET transistors Qa and Qb to the operating point.
A circuit for generating or supplying. The output is taken as a change in voltage or a change in frequency between the terminals A and B or between the -V line and the terminal A or B.

[Procedure Amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0068

[Correction method] Change

[Correction content]

In FIG. 17, the bias voltage circuit 7 of FIG. 13 is composed of a Zener diode ZdO and a capacitor CO, and the other parts are the same as those of FIG. 13, 16, an inductance type astable multivibrator shown in FIG. 17, FET transistor Qa as a switching element, that have used Qb. The bias voltage circuit 7 shown in FIG. 13 is incorporated to operate the FET transistors Qa and Qb . The output signal is taken out in rectified form. The magnetic field sensor of the present invention has an excellent feature that a new rectifier circuit, which is difficult to accurately rectify and take out a high-frequency signal, is not newly required, and therefore requires a small number of circuit components.

[Procedure correction 6]

[Document name to be corrected] Drawing

[Correction target item name] Fig. 16

[Correction method] Change

[Correction content]

FIG. 16

[Procedure Amendment 7]

[Document name to be corrected] Drawing

[Name of item to be corrected] Fig. 17

[Correction method] Change

[Correction content]

FIG. 17

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Jiro Yamazaki 1-1 Sensumachi, Tobata-ku, Kitakyushu City Kyushu Institute of Technology

Claims (5)

[Claims] 1. An amorphous magnetic wire and a high-frequency current are passed directly in the longitudinal direction of the amorphous magnetic wire to generate concentric alternating magnetic fields centered on the magnetic wire within and around the magnetic wire. A magnetic field sensor comprising: a conversion circuit for converting a change in the alternating magnetic field based on an external magnetic field in the longitudinal direction of the amorphous magnetic wire into an electric signal. 2. The conversion circuit captures a change in the alternating magnetic field as a change in a terminal voltage generated at both ends of the amorphous magnetic wire, and outputs an electric signal based on the change in the terminal voltage. The magnetic field sensor according to claim 1. 3. The magnetic field sensor according to claim 1, wherein the conversion circuit detects a change in the alternating magnetic field as a change in inductance of the amorphous magnetic wire and converts the change in inductance into an electric signal. 4. When converting the change in the inductance into an electric signal, an inductance type astable multivibrator composed of switching elements operating at high speed is used to extract the electric signal based on the change in the oscillation frequency. The magnetic field sensor according to claim 3, wherein: 5. The magnetic field sensor according to claim 4, wherein a field effect transistor is used as the switching element.