JP6701995B2 - Magnetic field measuring device - Google Patents

Description

  The present invention relates to a magnetic field measuring apparatus including a magnetic field generation unit that generates a magnetic field that acts on an object to be measured, and a magneto-impedance sensor that measures a magnetic field generated from the object to be measured. In particular, the present invention relates to a magnetic field measuring apparatus capable of measuring a magnetic field of a measurement object with high accuracy even when a strong magnetic field from a magnetic field generating unit acts on the magneto-impedance sensor.

  BACKGROUND ART Conventionally, a magnetic field measurement device such as a magnetic inspection device including a magnetic field generation unit that generates a measurement magnetic field that is a magnetic field that acts on an object to be measured and a magnetic impedance sensor (hereinafter, also referred to as MI sensor) is known. (See Patent Document 1 below). In this magnetic field measuring apparatus, the measurement magnetic field is applied to the measurement target to magnetize the measurement target or to cause an eddy current to flow in the measurement target. The MI sensor measures the magnetic field generated around the object to be measured, thereby detecting the presence or absence of the object to be measured. The magnetic field measuring device is used, for example, as a foreign substance detecting device for detecting a foreign substance made of metal or magnetic material contained in food or the like, or as a rotating speed calculating device for calculating the rotating speed of a metal gear (see FIG. 8). .

  The MI sensor includes a magnetic sensitive body made of an amorphous wire and a detection coil wound around the magnetic sensitive body. The detection coil outputs an output voltage corresponding to the magnetic field acting on the magnetic sensitive body. The MI sensor is configured to measure the strength of the magnetic field generated from the measurement object by measuring the output voltage.

JP, 2005-10902, A

  However, in the above-mentioned magnetic field measuring device, since the comparatively strong measuring magnetic field is generated from the magnetic field generating section, this measuring magnetic field also acts on the magnetic sensitive body. Unlike other magnetic sensors, the MI sensor does not saturate the output voltage even when a strong magnetic field acts in a direction orthogonal to the magnetic sensitive direction (axial direction) of the magnetic sensitive body because of the characteristics of the sensor. Therefore, it is possible to use the MI sensor without any problem even in a state where a strong measuring magnetic field acts in the direction orthogonal to the magnetic sensitive body. However, even if the MI sensor is consciously arranged so that the magnetic field for measurement acts in the direction orthogonal to the magnetic sensitive direction and does not act in the magnetic sensitive direction, the magnetic field for measurement is measured in the magnetic sensitive direction due to some misalignment. The magnetic field may act. When the measurement magnetic field acts on the MI sensor in the magnetic sensitive direction, the output voltage may be saturated because the measurement magnetic field applied is strong even if the amount of deviation in the adjustment is relatively small. Therefore, it may not be possible to accurately measure the magnetic field generated from the measurement target.

  The present invention has been made in view of such a background, and even if the magnetic field generated from the magnetic field generation unit acts in the magnetic sensitive direction of the magnetic sensitive body of the MI sensor, the MI sensor is not adjusted and the MI sensor is not adjusted. It is an object of the present invention to provide a magnetic field measuring device that can be adjusted so that the output of the device does not saturate.

One aspect of the present invention, a magnetic field generation unit that generates a measurement magnetic field that is a magnetic field that acts on an object to be measured,
A magneto-impedance sensor for measuring a magnetic field to be measured, which is a magnetic field generated from the measurement object by the action of the measuring magnetic field,
The magneto-impedance sensor includes a magnetic sensitive body, a detection coil wound around the magnetic sensitive body, and a measurement circuit that measures an output voltage of the detection coil,
The magneto-impedance sensor is arranged at a position where the measuring magnetic field acts on the magnetic sensitive body,
The the magnetic sensitive member, the detection bucking coils are wound with a coil, the magnetic field generated by energization of the ball striking extinguishing coil, the measuring magnetic field acting on the magnetic sensitive member, the magneto-sensitive direction of the magnetic sensitive member being configured to cancel the component in,
One of the detection coil and the canceling coil is arranged so as to fit inside both ends of the other coil of the detecting coil and the canceling coil in the magnetic sensitive direction of the magnetic sensitive body. The magnetic field measuring device is characterized by being provided (Claim 1).

In the above magnetic field measuring device, the above-mentioned canceling coil capable of canceling a predetermined amount of the magnetic sensitive component of the measuring magnetic field is wound around the magnetic sensitive body.
Therefore, the component of the measuring magnetic field acting on the magnetic sensitive body in the magnetic sensitive direction can be canceled by the magnetic field generated by energizing the canceling coil. Therefore, even if the magnetic field acts on the magnetic sensitive body in the magnetic sensitive direction, the effect is canceled by the canceling coil so that the output of the MI sensor is not saturated even if the position of the MI sensor is not adjusted. can do. Therefore, it is possible to accurately measure the magnetic field generated from the measurement object by the MI sensor. The term “cancellation” in the present invention does not necessarily mean that the value is completely set to zero. Of course, there is no problem if it is completely set to 0, but if the output of the MI sensor is canceled to the extent that the output does not saturate, measurement can be performed without problems.

  As described above, according to this aspect, even when the magnetic field generated from the magnetic field generation unit acts in the magnetic sensitive direction of the magnetic sensitive body of the MI sensor, the magnetic field measurement that can be adjusted so that the output of the MI sensor is not saturated. A device can be provided.

1 is a conceptual diagram of a magnetic field measuring apparatus according to the first embodiment. 3 is a plan view of the magneto-impedance element according to the first embodiment. FIG. 3 is a graph showing a change over time in the output voltage of the detection coil when foreign matter is mixed in the first embodiment. 3 is a graph showing the time change of the current flowing in the electromagnetic coil, the current flowing in the canceling coil, the current flowing in the magnetic sensitive body, and the output voltage of the detection coil in the first embodiment. 3 is a graph showing a relationship between a magnetic field component of a magnetic field acting on a magnetic body and an output voltage in the first embodiment. 1 is a schematic circuit diagram of a magnetic field measurement apparatus according to the first embodiment. 3 is a conceptual diagram of a magnetic field measuring apparatus according to a second embodiment. FIG. 6 is a conceptual diagram of a magnetic field measuring apparatus according to a third embodiment. FIG. FIG. 7 is a plan view of the magneto-impedance element according to the fourth embodiment. FIG. 13 is a plan view of the magneto-impedance element according to the fifth embodiment. XI-XI sectional drawing of FIG. 6 is a conceptual diagram of a magnetic field measuring apparatus according to a sixth embodiment. FIG. 9 is a conceptual diagram of a magnetic field measuring apparatus according to a seventh embodiment. FIG.

In the magnetic field measuring device, the orientation of the magnetic sensitive body is determined so that the component in the magnetic sensitive direction of the measuring magnetic field acting on the magnetic sensitive body is smaller than the component in the direction orthogonal to the magnetic sensitive direction. It is preferable that it is provided (Claim 4 ).
As described above, in the magnetic field measuring apparatus, the MI sensor is basically arranged basically so that the measuring magnetic field does not act in the magnetic sensitive direction. However, since the canceling coil is provided in the present invention, even if the MI sensor is arranged so that a large measuring magnetic field acts in the magnetic sensitive direction by adjusting the strength of the current flowing through the canceling coil. , It is possible to adjust so that the output voltage of the MI sensor is not saturated. However, there is a problem that the power consumption increases when the current flowing through the cancellation coil is large. On the other hand, when the measurement magnetic field acting on the magnetosensitive body is adjusted as in the second aspect of the present invention, the magnetosensitive direction component of the measurement magnetic field acting on the magnetosensitive body is small, so that a large current flows in the cancellation coil. It is possible to cancel this magnetic-sensitive direction component without flowing. Therefore, the power consumption of the magnetic field measuring device can be saved.
As described above, even if a strong magnetic field acts on the magnetic sensitive body in the direction orthogonal to the magnetic sensitive direction, the output voltage is not saturated due to the characteristics of the MI sensor, so that no particular problem occurs.

Further, it is preferable that the magnetic field generator is an electromagnetic coil, and is configured to flow an alternating current through the electromagnetic coil, and to flow a current synchronized with the alternating current through the cancellation coil (claim 5 ). .
In this case, an alternating magnetic field can be generated from the electromagnetic coil. Therefore, for example, when the measurement target is a non-magnetic material and is a conductive material, an eddy current can be passed through the measurement target, and the magnetic field generated thereby can be measured by the MI sensor. become. Therefore, even if the measurement target is not a magnetic substance, the magnetic field generated from the measurement target can be measured.
In this case, an AC magnetic field (measurement magnetic field) generated from the electromagnetic coil acts on the magnetic sensitive body. That is, the magnetic field for measurement which changes with time acts on the magnetic sensitive body. However, in the above-mentioned magnetic field measuring device, since a current synchronized with the alternating current flowing through the electromagnetic coil is passed through the canceling coil, even if the magnetosensitive direction component of the measuring magnetic field acting on the magnetosensitive body changes with time, this Can be exactly canceled.

Further, it is preferable that the magnetic field generating section is a permanent magnet (claim 6 ).
In this case, the magnetic field can be generated without supplying power to the magnetic field generation unit. Therefore, the power consumption of the magnetic field measuring device can be saved.

Further, it is preferable that the detection coil and the canceling coil are concentrically wound around the magnetic sensitive body (claim 7 ).
In this case, the axial length of the magnetic sensitive body can be shortened as compared with the case where the detection coil and the canceling coil are formed at positions adjacent to each other in the axial direction. Therefore, the manufacturing cost of the MI sensor can be reduced.

(Embodiment 1)
An embodiment of the magnetic field measuring device will be described with reference to FIGS. As shown in FIG. 1, the magnetic field measuring apparatus 1 of the present embodiment includes a magnetic field generator 2 and a magnetoimpedance sensor 3 (MI sensor). The magnetic field generator 2 generates a measuring magnetic field H ₁ that is a magnetic field that acts on the measurement target 4. The MI sensor 3 measures a magnetic field to be measured H ₂ that is a magnetic field generated from the measuring object 4 by the action of the measuring magnetic field H ₁ .

As shown in FIGS. 2 and 6, the MI sensor 3 includes a magnetic sensitive body 31, a detection coil 32, and a measurement circuit 33. The detection coil 32 is wound around the magnetic sensitive body 31. Measuring circuit 33 measures the output voltage V _o of the detecting coil 32.

As shown in FIG. 1, the MI sensor 3 is arranged at a position where the magnetic field for measurement H ₁ acts on the magnetic sensitive body 31. The MI sensor 3 is arranged immediately below the magnetic field generation unit 3.
As shown in FIG. 2, a canceling coil 34 is wound around the magnetic sensitive body 31. Due to the magnetic field H ₃ generated by energizing the canceling coil 34, the component of the measuring magnetic field H ₁ acting on the magnetic sensitive body 31 in the magnetic sensitive direction (axial direction: X direction) of the magnetic sensitive body 31 (hereinafter, the magnetic sensitive direction). Component H _1X ).

As shown in FIG. 1, in this embodiment, the electromagnetic coil 2 _E is used as the magnetic field generator 2. By flowing an alternating current i through the electromagnetic coil 2, a magnetic field for measurement H ₁ (alternating magnetic field) is generated from the electromagnetic coil 2 _E. The measurement magnetic field H _{1 is applied} to the inspection target 11 such as food. When a foreign substance (measurement target 4) is mixed in the inspection target 11, a measured magnetic field H ₂ is generated around the measurement target 4. That is, for example, when the measuring object 4 is a magnetic body, the measuring magnetic field H ₁ magnetizes the measuring object 4 and a measured magnetic field H ₂ is generated around the measuring object 4. When the measurement object 4 is a metal, an eddy current flows in the measurement object 4, and as a result, a magnetic field (measured magnetic field H ₂ ) caused by the eddy current is generated in the surroundings. By measuring the magnetic field H ₂ to be measured by the MI sensor 3, it is configured to determine whether or not a foreign substance (measurement target 4) is mixed in the inspection target 11.

In this embodiment, the magnetic sensitive body 31 is arranged on the central axis A of the electromagnetic coil 2 _E. The coil magnetic field H ₁ generated from the electromagnetic coil 2 _E, it is desirable to be perfectly symmetrical with respect to the central axis A of the electromagnetic coils 2 _E, complete alignment is difficult. Therefore, even if the magnetic sensitive body 31 is arranged on the central axis A, the magnetic sensitive direction component H _1X is always generated due to a slight deviation. Further, when the magnetic field measuring device 1 is manufactured, the magnetic sensitive body 31 may be arranged at a position deviated from the central axis A. This also causes the above-mentioned magnetic-sensitive direction component H _1X . In the present embodiment, this magnetic sensitive component H _1X can be canceled by the magnetic field H ₃ of the canceling coil 34.

  As shown in FIG. 6, the MI sensor 3 includes a magneto-impedance element 30 (hereinafter also referred to as an MI element 30), an IC 35, and a wiring board 39 on which these are mounted. As shown in FIG. 2, the MI element 30 includes a magnetic sensitive body 31, a detection coil 32, a canceling coil 34, and a sensor substrate 301 on which these are mounted. The magnetic sensitive body 31 is made of a zero magnetostrictive amorphous wire.

FIG. 4 is a graph showing changes over time of the current i flowing in the electromagnetic coil 2 _E , the current I flowing in the canceling coil 34, the current I _P flowing in the magnetic sensitive body 31, and the output voltage V _O of the detection coil 32. Indicates. As shown in the figure, the current i flowing through the electromagnetic coil 2 _E and the current I flowing through the canceling coil 34 are synchronized. A magnetic field H ₃ (see FIG. 2) is generated by passing a current I through the canceling coil 34 to cancel the magnetic sensitive component H _1X of the measuring magnetic field H ₁ acting on the magnetic sensitive body 31.

Further, as shown in FIG. 4, in this embodiment, a pulsed current I _P is passed through the magnetic sensitive body 31. When the current I _P rises (time t _u ) and falls (time t _d ), an output voltage V _O corresponding to the strength of the magnetic field H ₂ to be measured acting on the magnetic sensitive body 31 is generated in the detection coil 32. To do. By measuring this output voltage V _O , the presence or absence of the measurement object 4 (foreign matter) is inspected.

As shown in FIG. 1, when the measurement object 4 (foreign matter) is mixed in the inspection object 11 conveyed by the belt conveyor 19, as the inspection object 11 approaches the MI sensor 3, the object that acts on the MI sensor 3 is detected. The strength of the measuring magnetic field H ₂ is increased. Therefore, as shown in FIG. 3, the output voltage V _O has a peak value at a predetermined time t ₀ and then decreases. The MI sensor 3 determines that the measurement target 4 (foreign matter) is mixed in the inspection target 11 when the output voltage V _O exceeds a predetermined threshold V _th .

As described above, in the present embodiment, the magnetic sensitive direction component H _1X of the measuring magnetic field H ₁ acting on the magnetic sensitive body 31 is canceled by the magnetic field H ₃ generated by energizing the canceling coil 34. Therefore, the output voltage V _O due to the magnetic field H ₂ to be measured can be accurately measured. That is, as shown in FIG. 5, the output voltage V _O of the MI sensor 3 is not saturated when the magnetic sensitive direction component H _{X of the} magnetic field applied to the magnetic sensitive body 31 is small. That is, it is possible to obtain the output voltage V _O proportional to the magnetic-sensitive direction component H _X. On the other hand, if the magnetic sensitive direction component H _X becomes high, the MI sensor 3 enters the saturation region, and the output voltage V _O proportional to the magnetic sensitive direction component H _X cannot be obtained. In the present embodiment, as described above, the magnetosensitive direction component H _1X of the measuring magnetic field H ₁ acting on the magnetosensitive body 31 is canceled by the canceling coil 34, so that the MI sensor 3 can be used in the non-saturated region. . Therefore, the magnetosensitive direction component of the magnetic field to be measured H ₂ generated from the measurement object 4 and acting on the magnetosensitive body 31 can be accurately measured.

Next, the structure of the MI sensor 3 will be described in more detail with reference to FIG. As described above, the MI sensor 3 of this embodiment includes the MI element 30, the IC 35, and the wiring board 39. The IC 35 includes a pulse generation circuit 351, a measurement circuit 33, a synchronization circuit 36, a CPU 353, a ROM 354, and a RAM 355. The pulse generation circuit 351 is connected to the magnetic sensitive body 31. A pulse wave (current I _P ) is passed from the pulse generation circuit 351 to the magnetic sensitive body 31. The measurement circuit 33 also measures the output voltage V _O of the detection coil 32. The measurement circuit 33 includes a sample hold circuit (not shown) that holds the output voltage V _O for a certain period, and an A/D converter (not shown) that converts the held output voltage V _O into a digital value.

Further, as shown in FIG. 6, the electromagnetic coil 2 _E is connected to the drive circuit 12. A current i (AC current) is passed from the drive circuit 12 to the electromagnetic coil 2 _E. The synchronizing circuit 36 formed in the IC 35 causes the current I synchronized with the current i flowing through the electromagnetic coil 2 _E to flow through the canceling coil 34. As a result, the magnetosensitive direction component H _1X of the measuring magnetic field H ₁ acting on the magnetic sensitive body 31 is canceled.

  A determination program 356 is stored in the ROM 354. The CPU 353 reads out and executes the judgment program 356. Thereby, it is configured to determine whether or not the foreign substance (measurement target 4) is mixed in the inspection target 11 (see FIG. 1).

Next, the function and effect of this embodiment will be described. As shown in FIG. 2, in this embodiment, the canceling coil 34 is wound around the magnetic sensitive body 31.
Therefore, the magnetic sensitive component H _1X of the measuring magnetic field H ₁ acting on the magnetic sensitive body 31 can be canceled by the magnetic field H ₃ generated by energizing the canceling coil 34. Therefore, even if a strong magnetic field acts on the magnetic sensitive body 31 in the magnetic sensitive direction, by canceling the magnetic sensitive direction component, the output of the MI sensor 3 can be adjusted so as not to be saturated. Therefore, the measured magnetic field H ₂ generated from the measuring object 4 can be accurately measured by the MI sensor 3.

Further, in the present embodiment, as shown in FIG. 1, the position and orientation of the MI sensor 3 are adjusted so that the component H _1X of the measuring magnetic field H ₁ acting on the magnetic sensitive body 31 in the magnetic sensitive direction approaches 0 as much as possible. ing. As a result, the magnetic sensitive component H _1X is made smaller than the component in the direction (Z direction) orthogonal to the magnetic sensitive direction (orthogonal component H _1Z ).
Thus, since the magneto-sensitive direction component H _1X of the coil magnetic field H ₁ acts on the magnetic sensitive member 31 is small, even without flow a large current to the bucking coil 31, can counteract this magnetic sensitive direction component H _1X it can. Therefore, power consumption of the magnetic field measuring device 1 can be saved.
As described above, even if a strong magnetic field acts on the magnetic sensitive body 31 in a direction orthogonal to the magnetic sensitive direction, the output voltage V _O of the MI sensor 3 is not saturated, so that no particular problem occurs.

Further, as shown in FIG. 1, the magnetic field generation unit 2 of the present embodiment is an electromagnetic coil 2 _E , and is configured to flow an alternating current i through the electromagnetic coil 2 _E. Then, the current I synchronized with the alternating current i is made to flow through the cancellation coil 34.
Therefore, an alternating magnetic field can be generated from the electromagnetic coil 2 _E. Therefore, for example, when the measuring object 4 is a non-magnetic material and is a conductive material, an eddy current can be passed through the measuring object 4, and the magnetic field generated with this can be measured by the MI sensor 3. It becomes possible to do. Therefore, even if the measurement object 4 is not a magnetic substance, the magnetic field generated from the measurement object 4 can be measured.
In this case, the magnetic field 31 (measurement magnetic field H ₁ ) acts on the magnetic sensitive body 31. That is, the magnetic field for measurement H ₁ that changes with time acts on the magnetic sensitive body 31. However, in this embodiment, since the current I synchronized with the alternating current i flowing through the electromagnetic coil 2 is passed through the canceling coil 34, the magnetosensitive direction component H _{1X of} the measuring magnetic field H ₁ acting on the magnetic sensitive body 31 is temporal. Even if it changes to, it can be canceled exactly.

Further, as shown in FIG. 2, the MI element 30 of this embodiment includes two detection coils 32, which are a first detection coil 32a and a second detection coil 32b. A cancellation coil 34 is formed between these two detection coils 32a and 32b.
Therefore, the two detection coils 32a and 32b can be arranged at positions sandwiching the cancellation coil 34 from both sides, and the symmetry of the MI element 30 can be enhanced. Therefore, the measurement accuracy of the measured magnetic field H ₂ can be improved.

  As described above, according to the present embodiment, it is possible to provide the magnetic field measurement device in which the output of the magneto-impedance sensor is less likely to be saturated even when the magnetic field generated by the magnetic field generation unit acts.

  In the following embodiments, the same reference numerals as those used in the first embodiment among the reference numerals used in the drawings represent the same components and the like as those in the first embodiment unless otherwise specified.

(Embodiment 2)
The present embodiment is an example in which the configuration of the magnetic field generator 2 is changed. As shown in FIG. 7, in this embodiment, a permanent magnet 2 _P is used as the magnetic field generation unit 2. The measurement magnetic field H ₁ generated from the permanent magnet 2 _{P is applied} to the detection target 11. Then, as in the first embodiment, the magnetic field to be measured H ₂ generated from the foreign substance (measurement target 4) present in the detection target 11 is measured by the MI sensor 3. Thereby, it is configured to confirm whether or not the foreign matter is mixed in the detection target 11.

With the above configuration, since the permanent magnet 2 _P is used as the magnetic field generation unit 2, it is possible to generate the measurement magnetic field H ₁ without supplying electric power to the magnetic field generation unit 2. Therefore, power consumption of the magnetic field measuring device 1 can be saved.
Besides, it has the same configuration and operation effects as those of the first embodiment.

(Embodiment 3)
The present embodiment is an example in which the method of using the magnetic field measuring apparatus 1 is changed. As shown in FIG. 8, in the present embodiment, the magnetic field measurement device 1 is used as a rotation speed measurement device that measures the rotation speed of the gear 49 (measurement target 4). The gear 49 is made of a magnetic material. In this embodiment, the measurement magnetic field H ₁ generated from the magnetic field generation unit 2 is applied to the gear 49. As a result, the gear 49 is magnetized, and the measured magnetic field H ₂ is generated from the gear 49. When the gear 49 rotates, the measured magnetic field H ₂ generated from the teeth 48 of the gear 49 is periodically measured by the MI sensor 3. That is, in accordance with the tooth shape of the gear 49, the output voltage V _o of the MI sensor 3 may become weakened or become periodically strongly. The rotation speed of the gear 49 is detected by measuring the cycle of the output voltage V _o .
Besides, it has the same configuration and operation effects as those of the first embodiment.

(Embodiment 4)
The present embodiment is an example in which the configuration of the MI element 30 is changed. As shown in FIG. 9, the MI element 30 of this embodiment includes two cancellation coils 34, which are a first cancellation coil 34a and a second cancellation coil 34b. The detection coil 32 is formed between these two cancellation coils 34a and 34b.

With this configuration, the two canceling coils 34a and 34b are arranged at positions sandwiching the detection coil 32 from both sides, so that the symmetry of the MI element 30 can be increased. Therefore, the detection accuracy of the magnetic field H _{2 to} be measured by the MI element 30 can be improved.

(Embodiment 5)
The present embodiment is an example in which the configuration of the MI element 30 is changed. As shown in FIGS. 10 and 11, in the present embodiment, the detection coil 32 and the canceling coil 34 are concentrically wound around the magnetic sensitive body 31. The cancellation coil 34 is wound around the detection coil 32. An insulating layer (not shown) is interposed between the magnetic sensitive body 31 and the detection coil 32, and between the detection coil 32 and the cancellation coil 34.

With the above configuration, the length of the magnetic sensitive body 31 in the X direction can be shortened as compared with the case where the two coils 32 and 34 are formed at positions adjacent to each other in the X direction (see FIG. 2 ). Therefore, the manufacturing cost of the MI element 30 can be reduced.
Further, with the above configuration, the number of turns of the canceling coil 34 can be increased without increasing the length of the magnetic sensitive body 31 in the X direction as compared with the first embodiment (see FIG. 2 ). Therefore, the magnetic field H ₃ generated from the canceling coil 34 can be strengthened without increasing the length of the magnetic sensitive body 31 in the X direction. Therefore, even if the magnetic sensitive direction component H _{1X of the} magnetic field for measurement H ₁ strongly acts on the magnetic sensitive body 31, it can be sufficiently canceled and the saturation of the MI sensor 3 can be suppressed.
Besides, it has the same configuration and operation effects as those of the first embodiment.

(Embodiment 6)
The present embodiment is an example in which the arrangement position of the MI sensor 3 is changed. As shown in FIG. 12, in this embodiment, the MI sensor 3 is arranged closer to the belt conveyor 19 than the magnetic field generator 2. When the inspection target 11 is closest to the MI sensor 3, the distance from the MI sensor 3 to the detection target 11 is shorter than the distance from the MI sensor 3 to the magnetic field generation unit 2.

Further, in the present embodiment, the MI sensor 3 is arranged on the extension line of the central axis A of the electromagnetic coil 2 _E. Similar to the first embodiment, the magnetosensitive direction component H _1X of the measuring magnetic field H ₁ that acts on the magnetosensitive body 31 in the MI sensor 3 is smaller than the vertical direction component H _1Z .

The function and effect of this embodiment will be described. With the above configuration, the magnetic field H ₂ to be measured generated from the DUT 4 can be strongly applied to the MI sensor 3. Therefore, the measurement sensitivity of the magnetic field H _{2 to} be measured by the MI sensor 3 can be increased.
Besides, it has the same configuration and operation effects as those of the first embodiment.

(Embodiment 7)
The present embodiment is an example in which the arrangement position of the MI sensor 3 is changed. As shown in FIG. 13, in this embodiment, the MI sensor 3 is arranged at a position deviated from the extension of the central axis A of the electromagnetic coil 2 _E. In the present embodiment, the magnetic-sensitive direction component H _{1X of} the measuring magnetic field H ₁ acting on the magnetic sensitive body 31 in the MI sensor 3 is larger than the vertical direction component H _1Z .

The function and effect of this embodiment will be described. With the above configuration, the degree of freedom in the arrangement position of the MI sensor 3 can be increased. Therefore, it becomes easy to design the magnetic field measuring apparatus 1. In the present embodiment, as in the first embodiment, since the canceling coil 34 is wound around the magnetic sensitive body 31, even if the magnetic sensitive direction component H _{1X of} the measuring magnetic field H ₁ acting on the magnetic sensitive body 31 is large, This magnetosensitive direction component H _1X can be sufficiently canceled. Therefore, the MI sensor 3 can be arranged at any place.
Besides, it has the same configuration and operation effects as those of the first embodiment.

1 Magnetic Field Measuring Device 2 Magnetic Field Generator 2 _E Electromagnetic Coil 2 _P Permanent Magnet 3 Magneto Impedance Sensor 31 Magnetosensitive Body 32 Detection Coil 33 Measuring Circuit 34 Canceling Coil 4 Object to be Measured

Claims (7)

A magnetic field generation unit that generates a measurement magnetic field that is a magnetic field that acts on the measurement target;
A magneto-impedance sensor for measuring a measured magnetic field, which is a magnetic field generated from the measurement object by the action of the measuring magnetic field,
The magneto-impedance sensor includes a magnetic sensitive body, a detection coil wound around the magnetic sensitive body, and a measurement circuit that measures an output voltage of the detection coil,
The magneto-impedance sensor is arranged at a position where the magnetic field for measurement acts on the magnetic sensitive body,
The the magnetic sensitive member, the detection bucking coils are wound with a coil, the magnetic field generated by energization of the ball striking extinguishing coil, the measuring magnetic field acting on the magnetic sensitive member, the magneto-sensitive direction of the magnetic sensitive member being configured to cancel the component in,
One of the detection coil and the canceling coil is arranged so as to fit inside both ends of the other coil of the detecting coil and the canceling coil in the magnetic sensitive direction of the magnetic sensitive body. A magnetic field measuring device characterized by being provided . The detection coil has a first detection coil and a second detection coil that are connected in series with each other, and the cancellation coil is a combination of the first detection coil and the second detection coil in the magnetic sensitive direction of the magnetic sensitive body. The magnetic field measuring device according to claim 1, wherein the magnetic field measuring device is arranged between the two. The canceling coil has a first canceling coil and a second canceling coil connected in series with each other, and the detecting coil includes the first canceling coil and the second canceling coil in the magnetic sensitive direction of the magnetic sensitive body. The magnetic field measuring device according to claim 1, wherein the magnetic field measuring device is arranged between the two. The orientation of the magnetic sensitive body is determined so that the component in the magnetic sensitive direction of the measuring magnetic field acting on the magnetic sensitive body is smaller than the component in the direction orthogonal to the magnetic sensitive direction. The magnetic field measuring device according to any one of claims 1 to 3 . The magnetic field generating unit is an electromagnetic coil, is configured to flow an alternating current through the electromagnetic coil, and is configured to flow a current synchronized with the alternating current through the cancellation coil . 4. The magnetic field measuring device according to any one of 4 above. The magnetic field measuring device according to claim 1, wherein the magnetic field generating unit is a permanent magnet. And the detection coil and the cancellation coils, characterized in that are wound concentrically the magnetic sensitive member, a magnetic field measuring apparatus according to any one of claims 1 to 6.

Images