Magnetic field detector

Abstract

To lighten the fatigue of setting a range in which magnetic fields can be measured.SOLUTION: A magnetic field measurer 1 measures the magnetic field to be measured. The magnetic field measurer 1 comprises: a magnetic impedance element 10 the impedance change rate of which varies in accordance with the magnetic field being measured; a drive signal addition unit 12 for adding a drive signal to the magnetic impedance element 10; and a measurement range setting unit 16 for setting a measurement range in which the magnetic field to be measured can be measured. A relationship between the magnetic field to be measured and the impedance change rate varies in accordance with the frequency of the drive signal. The measurement range setting unit 16 sets the measurement range by setting a frequency. Furthermore, in the magnetic impedance element 10, a measurable upper limit of the magnetic field to be measured increases on one hand and a maximum value of the impedance change rate decreases on the other hand according to an increase in frequency.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to the measurement of magnetic fields.

Background Art

[0002] Conventionally, magnetic sensors using magnetic impedance elements and the like have been known (see, for example, Patent Documents 1 to 4). It is also known to incorporate magnetic sensors into various circuits (see, for example, Patent Documents 5 to 7).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Patent Document 6

Patent Document 7

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in a magnetic sensor using a magnetic impedance element, the range of the magnetic field that can be measured is limited. Therefore, when measuring a magnetic field, it is necessary to appropriately set the range in which the magnetic field can be measured.

[0005] Therefore, an object of the present invention is to reduce the labor of setting the range in which a magnetic field can be measured.

Means for Solving the Problems

[0006] The magnetic field measuring device according to the present invention measures a magnetic field to be measured, and includes a magneto-impedance element whose impedance change rate changes according to the magnetic field to be measured, a drive signal applying unit that applies a drive signal to the magneto-impedance element, and a measurement range setting unit that sets a measurement range in which the magnetic field to be measured can be measured. According to the frequency of the drive signal, the relationship between the magnetic field to be measured and the impedance change rate changes, and the measurement range setting unit is configured to set the measurement range by setting the frequency.

[0007] The magnetic field measuring device configured as described above measures a magnetic field to be measured. The magneto-impedance element has an impedance change rate that changes according to the magnetic field to be measured. The drive signal applying unit applies a drive signal to the magneto-impedance element. The measurement range setting unit sets a measurement range in which the magnetic field to be measured can be measured. According to the frequency of the drive signal, the relationship between the magnetic field to be measured and the impedance change rate changes. The measurement range setting unit sets the measurement range by setting the frequency.

[0008] In the magneto-impedance element of the magnetic field measuring device according to the present invention, the upper limit of the measurable magnetic field to be measured may be increased as the frequency increases.

[0009] In the magneto-impedance element of the magnetic field measuring device according to the present invention, the maximum value of the impedance change rate may be decreased as the frequency increases.

[0010] In the magneto-impedance element of the magnetic field measuring device according to the present invention, when the magnetic field to be measured is below the measurable upper limit, the impedance change rate may increase as the magnetic field to be measured increases.

[0011] In addition, in the magnetic impedance element of the magnetic field measuring device according to the present invention, when the magnetic field to be measured exceeds the upper limit at which measurement is possible, the impedance change rate may decrease as the magnetic field to be measured increases.

[0012] In addition, the magnetic field measuring device according to the present invention may subtract a negative feedback magnetic field corresponding to the output of the magnetic impedance element from the magnetic field to be measured and apply it to the magnetic impedance element.

[0013] In addition, the magnetic field measuring device according to the present invention includes a bridge circuit in which the magnetic impedance element has a first magnetic thin film, a second magnetic thin film, a third magnetic thin film, and a fourth magnetic thin film, the first magnetic thin film and the second magnetic thin film are connected in parallel, the third magnetic thin film and the fourth magnetic thin film are connected in parallel, the first magnetic thin film and the third magnetic thin film are connected in series, the second magnetic thin film and the fourth magnetic thin film are connected in series, the easy magnetization direction of the first magnetic thin film and the easy magnetization direction of the fourth magnetic thin film are in the same direction, the easy magnetization direction of the second magnetic thin film and the easy magnetization direction of the third magnetic thin film are in the same direction, the easy magnetization direction of the first magnetic thin film and the easy magnetization direction of the second magnetic thin film are orthogonal, and a bias magnetic field in a direction different from both the easy magnetization direction of the first magnetic thin film and the easy magnetization direction of the second magnetic thin film is applied, and a voltage between a point connecting the first magnetic thin film and the third magnetic thin film and a point connecting the second magnetic thin film and the fourth magnetic thin film may be output.

[0014] In addition, the magnetic field measuring device according to the present invention may be configured such that the magnetic impedance element has a pickup coil.

[0015] In addition, the magnetic field measuring device according to the present invention may be configured such that the magnetic impedance element has a first amorphous magnetic layer, a second amorphous magnetic layer, and a conductor disposed between the first amorphous magnetic layer and the second amorphous magnetic layer.

[0016] In addition, the magnetic field measuring device according to the present invention may have a first insulator disposed between the first amorphous magnetic layer and the conductor, and a second insulator disposed between the second amorphous magnetic layer and the conductor.

[0017] In addition, the magnetic field measuring device according to the present invention may be configured such that the magneto-impedance element has an amorphous thin film, an amorphous wire, or an amorphous ribbon.

[0018] In addition, the magnetic field measuring device according to the present invention may be configured such that the magneto-impedance element measures a magnetic field of at least one axial component.

[0019] In addition, the magnetic field measuring device according to the present invention may be configured such that the measurement range setting unit decreases the upper limit of the measurable magnetic field to be measured.

[0020] In addition, the magnetic field measuring device according to the present invention may be configured to reduce magnetic noise.

[0021] In addition, the magnetic field measuring device according to the present invention may be configured such that the drive signal is a sine wave, a rectangular wave, or a pulse wave.

[0022] In addition, the magnetic field measuring device according to the present invention may be configured such that the drive signal is a chirp signal.

[0023] In addition, the magnetic field measuring device according to the present invention may be configured such that the drive signal is a band signal having a frequency within a predetermined band.

Brief Description of the Drawings

[0024]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Embodiments for Carrying Out the Invention

[0025] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0026] First Embodiment Fig. 1 is a functional block diagram showing the configuration of the magnetic field measuring device according to the first embodiment of the present invention. The magnetic field measuring device 1 according to the first embodiment of the present invention includes a magnetic impedance element 10, a drive signal application unit 12, an amplifier 14, a detection unit 15, and a measurement range setting unit 16.

[0027] The magnetic field measuring device 1 measures the magnetic field to be measured. The magnetic field to be measured can be a weak magnetic field (for example, magnetocardiogram) or a strong magnetic field (for example, a magnetic field measured during non-destructive inspection of infrastructure).

[0028] The magnetic impedance element 10 is one in which the impedance change rate changes according to the magnetic field to be measured. The magnetic impedance element 10 has a pickup coil. The magnetic impedance element 10 measures the magnetic field of at least one axial component (1 axis, 2 axes, 3 axes,...).

[0029] The amplifier 14 amplifies the output (e.g., voltage) of the magnetic impedance element 10. The detection unit 15 detects the output of the amplifier 14. The drive signal application unit 12 applies a drive signal to the magnetic impedance element 10. The measurement range setting unit 16 sets a measurement range within which the magnetic field to be measured can be measured.

[0030] Note that the relationship between the magnetic field to be measured and the impedance change rate changes according to the frequency of the drive signal. Also, the measurement range setting unit 16 sets the measurement range by setting the frequency of the drive signal (hereinafter sometimes referred to as the "drive frequency").

[0031] The drive signal is, for example, a sine wave, a rectangular wave, a pulse wave, or a chirp signal.

[0032] FIG. 2 is a graph showing the characteristics of the magnetic impedance element 10. In FIG. 2, the characteristics for the case of the drive frequency f1, the characteristics for the case of the drive frequency f2, and the characteristics for the case of the drive frequency f3 are illustrated. However, f1 < f2 < f3.

[0033] Referring to the characteristics for the case of the drive frequency f1, when the magnetic field to be measured is H1, the impedance change rate takes the maximum value R1. When the magnetic field to be measured is less than or equal to H1, the impedance change rate increases as the magnetic field to be measured increases. When the magnetic field to be measured exceeds H1, the impedance change rate decreases as the magnetic field to be measured increases. Therefore, if the magnetic field to be measured is 0 or more and H1 or less, the magnetic field to be measured can be uniquely determined from the impedance change rate. That is, the upper limit of the measurable magnetic field to be measured is H1.

[0034] Similarly, for the case of the drive frequency f2, the upper limit of the measurable magnetic field to be measured is H2. However, when the magnetic field to be measured is H2, the impedance change rate takes the maximum value R2. When the magnetic field to be measured is less than or equal to H2, the impedance change rate increases as the magnetic field to be measured increases. When the magnetic field to be measured exceeds H2, the impedance change rate decreases as the magnetic field to be measured increases.

[0035] Also in the case of the drive frequency f3, similarly, the upper limit of the measurable magnetic field to be measured is H3. However, when the magnetic field to be measured is H3, the impedance change rate takes the maximum value R3. When the magnetic field to be measured is equal to or less than H3, the impedance change rate increases as the magnetic field to be measured increases. When the magnetic field to be measured exceeds H3, the impedance change rate decreases as the magnetic field to be measured increases.

[0036] Note that H1 < H2 < H3. Also, R1 > R2 > R3.

[0037] Here, in the magnetic impedance element 10, as the drive frequencies increase to f1, f2, and f3, the upper limit of the measurable magnetic field to be measured increases to H1, H2, and H3, while the maximum value of the impedance change rate decreases to R1, R2, and R3.

[0038] Therefore, by setting the drive frequency, the upper limit (and thus the measurement range) of the measurable magnetic field to be measured can be set.

[0039] For example, when measuring a weak magnetic field, in order to avoid saturation, it is conceivable to decrease the drive frequencies to f3, f2, and f1, thereby decreasing the upper limits of the measurable magnetic fields to be measured to H3, H2, and H1. In this case, since the maximum values of the impedance change rate increase to R3, R2, and R1, the sensitivities increase to R3 / H3, R2 / H2, and R1 / H1.

[0040] Next, the operation of the first embodiment will be described.

[0041] First, a magnetic field to be measured (for example, a magnetocardiogram) is applied to the magnetic field measuring device 1. According to the magnetic field to be measured, the impedance change rate of the magnetic impedance element 10 changes, and an output (for example, a voltage) corresponding to the impedance change rate is output from the magnetic impedance element 10. The output of the magnetic impedance element 10 is amplified by the amplifier 14 and detected by the detector 15. However, the amplifier 14 may be located after the detector 15, or may be located both before and after the detector 15.

[0042] Note that a drive signal is applied to the magnetic impedance element 10 from the drive signal application unit 12. Then, since it can be said that the output of the magnetic impedance element 10 is modulated by the drive signal, the measurement data of the magnetic field to be measured can be obtained by detecting (demodulating) it with the detection unit 15.

[0043] The output of the detection unit 15 is given to the measurement range setting unit 16. The measurement range setting unit 16 sets a measurement range in which the magnetic field to be measured can be measured based on the output of the detection unit 15. For example, when the output of the detection unit 15 is much smaller than the upper limit of the measurable magnetic field to be measured, the drive frequency is gradually decreased (for example, decreased to f3, f2, f1 (see FIG. 2)), and the upper limit of the measurable magnetic field to be measured is decreased (for example, decreased to H3, H2, H1 (see FIG. 2)). Note that, as described above, the measurement range setting unit 16 may operate automatically based on the output of the detection unit 15, but it is also conceivable that the user manually operates the measurement range setting unit 16.

[0044] According to the first embodiment, by changing the drive frequency, the setting of the measurement range in which the magnetic field can be measured can be performed, so the labor of setting the measurement range can be reduced.

[0045] Note that an element for reducing magnetic noise may be added to the magnetic field measuring device 1 according to the first embodiment. Elements for reducing magnetic noise are well known and the description thereof is omitted (see Patent Document 5 (Japanese Unexamined Patent Application Publication No. 2017-133993), Patent Document 6 (Japanese Unexamined Patent Application Publication No. 2018-7821), and Patent Document 7 (Japanese Unexamined Patent Application Publication No. 2019-124661)).

[0046] Second Embodiment The second embodiment is different from the first embodiment in that it includes a loop filter 18 and a negative feedback coil 19.

[0047] FIG. 3 is a functional block diagram showing the configuration of the magnetic field measuring device 1 according to the second embodiment of the present invention. The magnetic field measuring device 1 according to the first embodiment of the present invention includes a magneto-impedance element 10, a drive signal applying unit 12, an amplifier 14, a detection unit 15, a measurement range setting unit 16, a loop filter 18, and a negative feedback coil 19. Hereinafter, parts that are the same as those in the first embodiment will be denoted by the same reference numerals and the description thereof will be omitted.

[0048] The magneto-impedance element 10, the drive signal applying unit 12, the amplifier 14, the detection unit 15, and the measurement range setting unit 16 are the same as those in the first embodiment, and the description thereof will be omitted.

[0049] The loop filter 18 receives the output of the detection unit 15 and supplies it to the negative feedback coil 19. The negative feedback coil 19 receives the output of the magneto-impedance element 10 via the loop filter 18. The negative feedback coil 19 further generates a negative feedback magnetic field corresponding to the output of the magneto-impedance element 10. A magnetic field obtained by subtracting the negative feedback magnetic field from the measured magnetic field is applied to the magneto-impedance element 10.

[0050] Next, the operation of the second embodiment will be described. However, parts that are the same as the operation of the first embodiment will be omitted from the description.

[0051] The output of the detection unit 15 is supplied not only to the measurement range setting unit 16 but also to the negative feedback coil 19 via the loop filter 18. The negative feedback coil 19 generates a negative feedback magnetic field corresponding to the output of the magneto-impedance element 10. The negative feedback magnetic field is subtracted from the measured magnetic field and applied to the magneto-impedance element 10.

[0052] According to the second embodiment, the same effects as those of the first embodiment are obtained.

[0053] Moreover, according to the second embodiment, by increasing the gain of the amplifier 14, the ratio between the measured magnetic field and the output of the detection unit 15 can be kept substantially constant.

[0054] Third Embodiment The third embodiment is different from the first embodiment in that the magnetic impedance element 10 includes a bridge circuit, where the magnetic impedance element 10 in the first embodiment has a pickup coil.

[0055] FIG. 4 is a diagram showing the configuration of the magnetic impedance element 10 in the magnetic field measuring device 1 according to the third embodiment of the present invention. The drive signal applying unit 12, the amplifier 14, the detection unit 15, and the measurement range setting unit 16 are the same as those in the first embodiment, and the description thereof is omitted (see FIG. 1).

[0056] The magnetic impedance element 10 in the magnetic field measuring device 1 according to the third embodiment includes a bridge circuit having a high-frequency power supply 20, a first magnetic thin film 21, a second magnetic thin film 22, a third magnetic thin film 23, a fourth magnetic thin film 24, and a voltage output unit 25.

[0057] The high-frequency power supply 20 is a power supply that applies a high-frequency voltage to the bridge circuit. The first magnetic thin film 21 and the second magnetic thin film 22 are connected in parallel. The third magnetic thin film 23 and the fourth magnetic thin film 24 are connected in parallel. The first magnetic thin film 21 and the third magnetic thin film 23 are connected in series. The second magnetic thin film 22 and the fourth magnetic thin film 24 are connected in series.

[0058] The easy magnetization direction d1 of the first magnetic thin film 21 and the easy magnetization direction d4 of the fourth magnetic thin film 24 are in the same direction. However, the anisotropy constant of the first magnetic thin film 21 and the fourth magnetic thin film 24 is Ku.

[0059] The easy magnetization direction d2 of the second magnetic thin film 22 and the easy magnetization direction d3 of the third magnetic thin film 23 are in the same direction. However, the anisotropy constant of the second magnetic thin film 22 and the third magnetic thin film 23 is also Ku.

[0060] The easy magnetization direction d1 of the first magnetic thin film 21 and the easy magnetization direction d2 of the second magnetic thin film 22 are orthogonal to each other.

[0061] A bias magnetic field having a direction different from both the easy magnetization direction d1 of the first magnetic thin film 21 and the easy magnetization direction d2 of the second magnetic thin film 22 is applied. For example, the direction of the bias magnetic field forms an angle of 45° with both the easy magnetization direction d1 and the easy magnetization direction d2.

[0062] Note that the directions of the magnetization vectors m1 of the first magnetic thin film 21, m2 of the second magnetic thin film 22, m3 of the third magnetic thin film 23, and m4 of the fourth magnetic thin film 24 are the same as the direction of the bias magnetic field.

[0063] A voltage is output between the point connecting the first magnetic thin film 21 and the third magnetic thin film 23 and the point connecting the second magnetic thin film 22 and the fourth magnetic thin film 24. The voltage output unit 25 outputs this voltage.

[0064] Next, the operation of the third embodiment will be described. However, the operations related to the drive signal applying unit 12, the amplifier 14, the detection unit 15, the measurement range setting unit 16, and the loop filter 18 are the same as those of the first embodiment, and the description thereof will be omitted.

[0065] First, a magnetic field to be measured is applied to the magneto-impedance element 10. The direction of the magnetic field to be measured is the same as the easy magnetization direction d2 of the second magnetic thin film 22.

[0066] Then, since the magnetization vector m1 of the first magnetic thin film 21 rotates in a direction away from the easy magnetization direction d1, the impedance of the first magnetic thin film 21 increases. Similarly, since the magnetization vector m4 of the fourth magnetic thin film 24 also rotates in a direction away from the easy magnetization direction d4, the impedance of the fourth magnetic thin film 24 also increases.

[0067] On the other hand, since the magnetization vector m2 of the second magnetic thin film 22 rotates in a direction approaching the easy magnetization direction d2, the impedance of the second magnetic thin film 22 decreases. Similarly, since the magnetization vector m3 of the third magnetic thin film 23 also rotates in a direction approaching the easy magnetization direction d3, the impedance of the third magnetic thin film 23 also decreases.

[0068] Then, the potential at the point connecting the first magnetic thin film 21 and the third magnetic thin film 23 decreases. On the other hand, the potential at the point connecting the second magnetic thin film 22 and the fourth magnetic thin film 24 increases. Therefore, the voltage between the point connecting the first magnetic thin film 21 and the third magnetic thin film 23 and the point connecting the second magnetic thin film 22 and the fourth magnetic thin film 24 changes according to the magnetic field to be measured. This voltage is output from the voltage output unit 25.

[0069] According to the third embodiment, the same effects as those of the first embodiment are achieved.

[0070] Fourth Embodiment The fourth embodiment is different from the first embodiment in that the magnetic impedance element 10 includes an amorphous magnetic layer, while the magnetic impedance element 10 in the first embodiment has a pickup coil.

[0071] FIG. 5 is a diagram showing the configuration of the magnetic impedance element 10 in the magnetic field measuring device 1 according to the fourth embodiment (FIG. 5(a)) and a modified example thereof (FIG. 5(b)) of the present invention. The drive signal applying unit 12, the amplifier 14, the detection unit 15, and the measurement range setting unit 16 are the same as those in the first embodiment, and the description thereof is omitted (see FIG. 1).

[0072] Referring to FIG. 5(a), the magnetic impedance element 10 has a first amorphous magnetic layer, a second amorphous magnetic layer, and a conductor. However, the conductor (for example, copper) is disposed between the first amorphous magnetic layer and the second amorphous magnetic layer.

[0073] According to the fourth embodiment, the same effects as those of the first embodiment are achieved.

[0074] Note that according to the fourth embodiment, although the conductor is in contact with the first amorphous magnetic layer and the second amorphous magnetic layer, it is not necessarily in contact.

[0075] That is, referring to FIG. 5(b), the magnetic impedance element 10 includes a first amorphous magnetic layer, a second amorphous magnetic layer, a conductor, a first insulator, and a second insulator. The first insulator is disposed between the first amorphous magnetic layer and the conductor. The second insulator is disposed between the second amorphous magnetic layer and the conductor.

[0076] Further, an amorphous magnetic layer and an insulator layer may be added to the modification shown in FIG. 5(b). FIG. 6 is a diagram showing the configuration of the magnetic impedance element 10 according to a further modification of the fourth embodiment of the present invention.

[0077] Referring to FIG. 6, an insulator layer and an amorphous magnetic layer are disposed above the first amorphous magnetic layer and below the second amorphous magnetic layer of the modification shown in FIG. 5(b). However, the insulator layer above the first amorphous magnetic layer is disposed between the first amorphous magnetic layer and the amorphous magnetic layer. The insulator layer below the second amorphous magnetic layer is disposed between the second amorphous magnetic layer and the amorphous magnetic layer.

[0078] In the fourth embodiment, including the modification, the magnetic impedance element 10 includes the first and second amorphous magnetic layers, but the magnetic impedance element 10 may have an amorphous wire or an amorphous ribbon. The magnetic impedance element 10 may have an amorphous thin film.

[0079] Fifth Embodiment The fifth embodiment is different from the first embodiment in that the drive signal is a band signal.

[0080] FIG. 7 is a functional block diagram showing the configuration of the drive signal applying unit 12 in the magnetic field measuring device 1 according to the fifth embodiment of the present invention. The magnetic impedance element 10, the amplifier 14, the detection unit 15, and the measurement range setting unit 16 are the same as those in the first embodiment, and the description thereof is omitted (see FIG. 1).

[0081] The drive signal application unit 12 according to the fifth embodiment outputs a band signal having a frequency within a predetermined band (a band with a center frequency flo [MHz] and a bandwidth B [Hz]) as a drive signal, and includes an S / P conversion unit 31, Nyquist filters 32a and 32b, a carrier signal source 33, a 90-degree phase shifter 34, mixers 36a and 36b, and an adder 38.

[0082] The S / P conversion unit 31 receives random pattern data (preferably something with strong autocorrelation such as a PN code or an M-sequence) at a chip rate of 2B [sps], converts it into a parallel signal, and supplies it to the Nyquist filters 32a and 32b. The Nyquist filters 32a and 32b filter the output of the S / P conversion unit 31 and supply it to the mixers 36a and 36b, respectively. The carrier signal source 33 outputs a carrier signal (frequency flo [MHz]). The 90-degree phase shifter 34 receives the carrier signal, changes the phase by 90 degrees, and outputs it. The mixer 36a multiplies the output of the Nyquist filter 32a and the output of the 90-degree phase shifter 34 and outputs the result. The mixer 36b multiplies the output of the Nyquist filter 32b and the carrier signal and outputs the result. The adder 38 adds the output of the mixer 36a and the output of the mixer 36b and outputs the result. Then, the output of the adder 38 becomes a band signal (bandwidth B [Hz], center frequency flo [MHz]).

[0083] Next, the operation of the fifth embodiment will be described. However, the operations related to the magnetic impedance element 10, the amplifier 14, the detection unit 15, the measurement range setting unit 16, and the loop filter 18 are the same as those of the first embodiment, and the description thereof will be omitted.

[0084] The random pattern data of the chip rate 2B[sps] is converted into a parallel signal by the S / P converter 31, and is respectively supplied to the mixers 36a and 36b via the Nyquist filters 32a and 32b. The output of the Nyquist filter 32a is multiplied by the mixer 36a with the phase of the carrier signal changed by 90 degrees. The output of the Nyquist filter 32b is multiplied by the mixer 36b with the carrier signal. The output of the mixer 36a and the output of the mixer 36b are added by the adder 38 to obtain a band signal (bandwidth B[Hz], center frequency flo[MHz]).

[0085] According to the fifth embodiment, the same effects as those of the first embodiment are achieved.

Explanation of symbols

[0086] 1 Magnetic field measuring device 10 Magnetic impedance element 12 Driving signal applying unit 14 Amplifier 15 Detection unit 16 Measurement range setting unit 18 Loop filter 19 Coil for negative feedback 20 High-frequency power supply 21 First magnetic thin film 22 Second magnetic thin film 23 Third magnetic thin film 24 Fourth magnetic thin film 25 Voltage output unit

Claims

1. A magnetic field measuring device for measuring a magnetic field to be measured, comprising: a magneto-impedance element whose impedance change rate changes according to the magnetic field to be measured; a drive signal applying unit for applying a drive signal to the magneto-impedance element; a measurement range setting unit for setting a measurement range in which the magnetic field to be measured can be measured; The relationship between the magnetic field to be measured and the impedance change rate changes according to the frequency of the drive signal, The measurement range setting unit sets the measurement range by setting the frequency, The measurement range setting unit decreases the upper limit of the measurable magnetic field to be measured, In the magneto-impedance element, as the frequency increases, the upper limit of the measurable magnetic field to be measured increases, In the magneto-impedance element, as the frequency increases, the maximum value of the impedance change rate decreases, Magnetic field measuring device.

2. The magnetic field measuring device according to claim 1, further comprising: subtracting a negative feedback magnetic field corresponding to the output of the magneto-impedance element from the magnetic field to be measured and applying the result to the magneto-impedance element. Magnetic field measuring device.

3. The magnetic field measuring device according to claim 1, wherein: the magneto-impedance element includes a bridge circuit having a first magnetic thin film, a second magnetic thin film, a third magnetic thin film, and a fourth magnetic thin film; the first magnetic thin film and the second magnetic thin film are connected in parallel; the third magnetic thin film and the fourth magnetic thin film are connected in parallel; the first magnetic thin film and the third magnetic thin film are connected in series; the second magnetic thin film and the fourth magnetic thin film are connected in series; an easy magnetization direction of the first magnetic thin film and an easy magnetization direction of the fourth magnetic thin film are in the same direction; an easy magnetization direction of the second magnetic thin film and an easy magnetization direction of the third magnetic thin film are in the same direction; an easy magnetization direction of the first magnetic thin film and an easy magnetization direction of the second magnetic thin film are orthogonal; a bias magnetic field having a direction different from both the easy magnetization direction of the first magnetic thin film and the easy magnetization direction of the second magnetic thin film is applied; a voltage between a point connecting the first magnetic thin film and the third magnetic thin film and a point connecting the second magnetic thin film and the fourth magnetic thin film is output. Magnetic field measuring device.

4. The magnetic field measuring device according to claim 1, wherein: the magneto-impedance element has a pickup coil. Magnetic field measuring device.

5. ​ The magnetic field measuring device according to claim 1, wherein the magnetic impedance element has a first amorphous magnetic layer, a second amorphous magnetic layer, and a conductor disposed between the first amorphous magnetic layer and the second amorphous magnetic layer.

6. The magnetic field measuring device according to claim 5, wherein a first insulator disposed between the first amorphous magnetic layer and the conductor, and a second insulator disposed between the second amorphous magnetic layer and the conductor. The magnetic field measuring device having the same.

7. The magnetic field measuring device according to claim 1, wherein the magnetic impedance element has an amorphous thin film, an amorphous wire, or an amorphous ribbon.

8. The magnetic field measuring device according to claim 1, wherein the magnetic impedance element measures a magnetic field of at least one axial component.

9. The magnetic field measuring device according to claim 1, wherein it reduces magnetic noise.

10. The magnetic field measuring device according to claim 1, wherein the drive signal is a sine wave, a rectangular wave, or a pulse wave.

11. The magnetic field measuring device according to claim 1, wherein the drive signal is a chirp signal.

12. The magnetic field measuring device according to claim 1, wherein the drive signal is a band signal having a frequency within a predetermined band.

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