JP2009168724A - Magnetic field measuring device and method of correcting magnetic field measurement value - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a device for precisely measuring a magnetic field in three-axis directions. <P>SOLUTION: A three-axis sensor 14 having, mounted thereon, a detection sensor 12 capable of independently measuring a magnetic field in the three-axis directions orthogonal with each other, is moved straight along a reference line 24 connecting a pair of reference points 22. A first fixing point 30 and a second fixing point 32 are set on a cross straight line 25 with the reference line 24 therebetween, the cross straight line 25 being orthogonal to the reference line 24. The magnetic field generated by magnet pieces 28 supported on the fixing points 30, 32 is measured. Zero cross points 44 of magnetic field measurement values in the direction of the reference line 24 are compared with each other. When they are not coincident with each other, a correction coefficient 46 for correcting the magnetic field measurement values of the three-axis sensor 14 in the direction of the reference line 24 and the direction of the cross straight line 25 is selected. The correction coefficient 46 in which the zero cross points 44 are coincident with each other is set as the correction coefficient 46 for obtaining the magnetic field measurement values in the direction of the reference line 24 and the direction of the cross straight line 25. This device includes a correction coefficient computing means that performs the above processes for setting the correction coefficient 46. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a magnetic field measuring apparatus and a method for correcting a magnetic field measurement value used for measuring a magnetic field in three axial directions with high accuracy.

For example, a magnetic sensor is used to check whether a permanent magnet is magnetized to a stencil as designed. An apparatus for accurately measuring a magnetic field in the vicinity of a measurement object by attaching this magnetic sensor to the probe tip has been developed (see Patent Document 1).
JP 2005-189200 A

The known prior art has the following problems to be solved.
For example, a three-axis magnetic sensor is an element having a side of about 50 microns and is mounted near the tip of a rod-shaped substrate having a width of several millimeters. A magnetic measurement probe is formed by attaching an electrode for taking out magnetic detection output to this rod-shaped substrate and coating a protective resin. The tip of the probe is moved in the magnetic field measuring mechanism to measure the near magnetic field of the measurement object three-dimensionally.

However, if the three axes set in the magnetic field measurement mechanism do not match the three axes of the measurement system assumed by the detection element of the magnetic sensor, an error occurs in the measurement value. There is a limit to increasing the positioning accuracy of the magnetic sensor to the probe support mechanism and the probe tip.
In order to solve the above-described problems, an object of the present invention is to provide a magnetic measurement apparatus and a magnetic measurement method that can accurately measure a magnetic field in three axial directions.

The following configurations are means for solving the above-described problems.
<Configuration 1>
A triaxial sensor equipped with a detection element capable of individually measuring magnetic fields in three axial directions orthogonal to each other and an arm supporting the three axial sensors can be freely set in three orthogonal directions set in the magnetic field measuring mechanism. A reference line that connects the pair of reference points by setting a pair of reference points on any one of the three axes set in the magnetic field measuring mechanism and the actuator to be moved The first fixed point and the second fixed point are set on a crossing straight line perpendicular to the reference line and the sensor driving means for linearly moving the three-axis sensor along the reference line. The first fixed point and the second fixed point are configured to support the same magnet piece so as to be in a mirror image relationship with each other, and the first fixed point and the first fixed point. With the magnet piece supported, on the reference line When the three-axis sensor is moved from one side to the other side, the result of measuring the magnetic field in the direction of the reference line and the direction of the crossing straight line is stored in the storage device as a first measurement result, and the second fixed The result of measuring the magnetic field in the direction of the reference line and the direction of the intersecting straight line when the three-axis sensor is moved from one to the other on the reference line while the magnet piece is supported at a point. The measurement result storage means for storing in the storage device as the measurement result of No. 2, and the zero cross point of the magnetic field measurement value in the direction of the reference line is compared between the first measurement result and the second measurement result. If not, select a correction coefficient that corrects the magnetic field measurement value in the direction of the reference line and the direction of the intersecting straight line of the three-axis sensor, and set the correction coefficient that matches both to the direction of the reference line and the intersection. Magnetic field measurement in the direction of a straight line Magnetic field measuring apparatus is characterized in that a correction coefficient calculating means for setting a correction coefficient for determining the value.

  Detection elements capable of individually measuring magnetic fields in three axial directions orthogonal to each other are arranged in the magnetic field measuring mechanism, and the magnetic fields in the three axial directions set in the magnetic field measuring mechanism are measured. At this time, if the three axes set in the magnetic field measurement mechanism do not match the three axes of the measurement system assumed by the detection element of the three-axis sensor, an error occurs in the measurement value. The correction coefficient can be obtained by comparing magnetic field measurement values measured when the same magnet is supported on both sides of the reference line so as to have a mirror image relationship with each other. Thereby, highly accurate three-dimensional magnetic field measurement becomes possible.

<Configuration 2>
In the magnetic field measurement apparatus according to Configuration 1, the first fixing means and the second fixing means include a single support base that supports the magnet piece, and the support base from the first fixing point to the second fixing base. A magnetic field measuring apparatus comprising a mechanism for moving to a fixed point.

  If the moving mechanism whose position accuracy has been adjusted is used, the first fixed point and the second fixed point can be positioned quickly and accurately.

<Configuration 3>
In the magnetic field measurement apparatus according to Configuration 2, the first fixing unit and the second fixing unit include a single support base that supports the magnet piece, and the support base is formed between the reference line and the intersecting straight line. A magnetic field measuring apparatus arranged on a turntable having a rotation axis perpendicular to a plane including the reference line and the intersecting straight line on an intersection.

  After obtaining the first measurement result, the second measurement result can be obtained accurately by rotating the rotary table 180 degrees.

<Configuration 4>
4. The magnetic field measurement apparatus according to Configuration 2 or 3, further comprising a switching mechanism that switches a support state of the magnet pieces so as to have a mirror image relationship on the support base.

  The magnet pieces can be positioned so as to have a mirror image relationship by simply switching the direction of the magnet pieces.

<Configuration 5>
In the magnetic field measurement apparatus according to any one of Configurations 1 to 3, the magnet piece is fixed to a support plate having a side surface parallel to the reference line and perpendicular to a plane including the reference line and the intersecting straight line. Magnetic field measuring apparatus characterized by the above.

  When the orientation of the side surface of the support plate is adjusted with respect to the reference line or the intersecting straight line, the magnet piece can be accurately supported in the intended state.

<Configuration 6>
A triaxial sensor equipped with a detection element capable of individually measuring magnetic fields in three axial directions orthogonal to each other and an arm supporting the three axial sensors can be freely set in three orthogonal directions set in the magnetic field measuring mechanism. A reference line that connects the pair of reference points by setting a pair of reference points on any one of the three axes set in the magnetic field measuring mechanism and the actuator to be moved Sensor driving means for linearly moving the three-axis sensor along the line, and on the intersecting straight line orthogonal to the reference line, the first fixed point and the second fixed point with the reference line interposed therebetween When the three-axis sensor is moved from one side to the other on the reference line with the magnet piece supported at the first fixed point, the direction of the reference line and the direction of the intersecting straight line The result of measuring the magnetic field is the first The measurement result is stored in the storage device, and the same magnet piece is supported at the second fixed point so that it is in a mirror image relationship with the second fixed point. The result of measuring the magnetic field in the direction of the reference line and the direction of the intersecting straight line when the three-axis sensor is moved from one to the other on the reference line while the magnet piece is supported at a point. The measurement result storage means for storing in the storage device as the measurement result of No. 2, and the zero cross point of the magnetic field measurement value in the direction of the reference line is compared between the first measurement result and the second measurement result. If not, select a correction coefficient that corrects the magnetic field measurement value in the direction of the reference line and the direction of the intersecting straight line of the three-axis sensor, and set the correction coefficient that matches both to the direction of the reference line and the intersection. Find the magnetic field measurement in the direction of the straight line Correction method for a magnetic field measuring device and sets the correction coefficient for.

  The three-axis sensor is a sensor in which three magnetic sensors are fixed to the tip of the probe in the three-axis direction of the measurement system. The three magnetic sensors are precisely aligned (angled) with each other in the element manufacturing stage. On the other hand, a magnetic field measurement mechanism that measures a magnetic field using this magnetic sensor supports, moves, or rotates a measurement object. The three axes set in the magnetic field measuring mechanism are also precisely aligned (angle aligned) with each other. However, it does not always coincide with the three axes of the measurement system assumed by the detection element of the magnetic sensor. If they do not match, the measurement value of the magnetic field in the X-axis direction of the measurement system assumed by the detection element is actually acquired even though the magnetic field in the X-axis direction of the magnetic field measurement mechanism of the measurement object should be measured. Therefore, prior to the measurement of the magnetic field of the measurement object, the correction coefficient is calculated using a magnet piece. Hereinafter, embodiments of the present invention will be described in detail for each example.

FIG. 1 is a plan view showing the magnetic field measuring apparatus according to the first embodiment. FIG. 2 is an explanatory diagram showing the nature of the measured values.
The operation principle of the apparatus of the present invention will be described with reference to these drawings. The triaxial sensor 14 is supported by the arm 16 so as to freely move in the triaxial direction in the magnetic field measuring mechanism 18. The actuator 20 of the magnetic field measurement mechanism 18 includes a mechanism group that moves the arm 16 in three axial directions set in the magnetic field measurement mechanism 18 and orthogonal to each other. This mechanism group has been conventionally used in various machine tools and measuring devices, and detailed description thereof will be omitted.

The triaxial sensor 14 is equipped with a detection element 12 that can individually measure magnetic fields in three axial directions orthogonal to each other. Here, an example in which the arm 16 is moved in the X-axis direction of the magnetic field measurement mechanism 18 will be described. In this apparatus, a magnet piece 28 is provided for correcting the magnetic field measurement value. The magnet piece 28 is a magnet that generates magnetic lines of force from the side of the triaxial sensor 14 in the Y-axis direction. A dashed-dotted line shows a magnetic force line.

FIG. 2 is an explanatory diagram for explaining the relationship among the lines of magnetic force generated by the magnet, the magnetic field measurement value, and the inclination of the three-axis sensor 14.
As shown in the figure, the arm 16 is moved in the X-axis direction, and the magnetic field in front of the magnet piece 28 is measured by the triaxial sensor 14. The magnetic field in the Y-axis direction has a maximum value when the triaxial sensor 14 is located in front of the magnet piece 28. On the other hand, as shown in the figure, the magnetic field in the X-axis direction becomes zero in front of the magnet piece 28, and the absolute value gradually increases after reversing the direction before and after that.

  Here, when the X-axis direction of the measurement system of the triaxial sensor 14 is inclined with respect to the X-axis direction in which the arm 16 moves, the position at which the zero-cross point of the magnetic field in the X-axis direction is measured is slightly Shift from the front position. The position where the maximum value of the magnetic field in the Y-axis direction is also slightly shifted from the position in front of the magnet piece 28. At this time, the measured value of the magnetic field in the X-axis direction measured by the triaxial sensor 14 is not a value obtained by measuring the magnetic field in the X-axis direction of the magnetic field measuring mechanism 18. That is, a measurement error slightly occurs.

FIG. 3 is a principle diagram of an apparatus capable of correcting the above measurement error.
As shown in the figure, the apparatus includes an arm 16 that supports the triaxial sensor 14 and a rotary table 56 that supports the magnet piece 28. The above-mentioned measurement is performed by moving the triaxial sensor 14 in the X-axis direction in the figure. At this time, a pair of reference points 22 is set on the X axis. A line connecting the pair of reference points 22 is defined as a reference line 24. A line orthogonal to the reference line 24 is defined as a crossing straight line 25.
A first fixed point 30 and a second fixed point 32 are set on the intersecting straight line 25 with the reference line 24 interposed therebetween.

  The magnet piece 28 is fixed to a support plate 60 having a side surface 62 parallel to the reference line 24 and perpendicular to the plane including the reference line 24 and the intersecting straight line 25. When the orientation of the side surface 62 of the support plate 60 is adjusted with respect to the reference line 24 or the intersecting straight line, the magnet piece 28 can be accurately supported in the intended state.

  A first fixing means 34 and a second fixing means 36 configured to support the magnet piece 28 are provided at the first fixing point 30 and the second fixing point 32. Each fixing means may be composed of a plate, a pin, or a clamp that holds the magnet piece 28 in a fixed posture in a fixed direction. It is difficult to prepare a pair of magnet pieces 28 having exactly the same characteristics. Accordingly, one magnet piece 28 is supported on the first fixing point 30 by using the first fixing means 34 to obtain the first measurement result. Next, the magnet piece 28 is moved to the second fixing point 32 side and supported by the second fixing means 36 to obtain a second measurement result.

  At this time, the lines of magnetic force generated by the magnet pieces 28 are preferably symmetrical with respect to the reference line 24. Accordingly, it is preferable to select the position and orientation of the magnet piece 28 so that the magnet piece 28 is in a mirror image relationship when the magnet piece 28 is fixed by the first fixing means 34 and when the magnet piece 28 is fixed by the second fixing means 36. . The first fixed point 30 and the second fixed point 32 do not necessarily have to be equidistant from the reference line 24. What is necessary is just to be able to support so that the magnet piece 28 may become a mirror image relationship mutually.

  The sensor driving means 26 drives the actuator 20 (FIG.) To move the triaxial sensor 14 linearly along the reference line 24. The first time, the three-axis sensor 14 is moved from one side to the other on the reference line 24 with the magnet piece 28 supported by the first fixed point 30. This is returned to the original state and the same operation is repeated with the magnet piece 28 supported by the second fixed point 32. By this operation, the triaxial sensor 14 stores the measurement result of the magnetic field in the direction of the reference line 24 and the direction of the intersecting straight line 25 in the measurement result storage unit 42 as the first measurement result 38 and the second measurement result 40. Can be made.

FIG. 4 is a comparative explanatory diagram of the first measurement result and the second measurement result.
The format of the graph in the figure is the same as in FIG. As shown in the figure, the first measurement result 38 and the second measurement result 40 are reversed in polarity, but magnetic field measurement values at substantially the same level are obtained. If the distance between the reference line 24 and the first fixed point 30 and the distance between the reference line 24 and the second fixed point 32 are not equal, the absolute values of the magnetic field measurement values are slightly different, but the Y-axis direction magnetic field is slightly different. And the position of the zero cross point 44 of the magnetic field in the X-axis direction should match. However, if the three-axis direction set in the magnetic field measurement mechanism 18 and the three axes of the measurement system assumed by the detection element of the three-axis sensor 14 do not match, the position of the zero cross point 44 is shifted as shown in the figure. .

  Here, for example, the support angle of the three-axis sensor 14 is adjusted so that the three-axis direction set in the magnetic field measurement mechanism 18 matches the three axes of the measurement system assumed by the detection element of the three-axis sensor 14. Can do. The support angle may be adjusted so that the positions of the zero cross points 44 in the figure coincide with each other in the X-axis direction.

  However, this adjustment requires skill and requires a highly accurate adjustment mechanism. In addition to the method of adjusting the angle mechanically, if the angle deviation is allowed and measured as it is, and the magnetic field measurement value is numerically corrected thereafter, high-precision measurement is possible.

FIG. 5 is an explanatory diagram showing how to obtain the correction coefficient of the magnetic field measurement value.
In the figure, the X axis and Y axis of the measurement system of the triaxial sensor 14 are represented as P and Q with respect to the X axis and Y axis set in the magnetic field measurement mechanism 18. The measurement system of the triaxial sensor 14 is inclined by β on the XY plane in the magnetic field measurement mechanism 18.

  At this time, when the magnetic field vector A is measured by the three-axis sensor 14, the magnetic field in the X-axis direction is Gx, and the magnetic field in the Y-axis direction is Gy. The vector A is inclined by α with respect to the X axis in the magnetic field measurement mechanism 18. At this time, the relationship between Gx, Gy, the absolute value of the vector A, and the angles α, β is expressed by the equation (b). The true measured values are Hx and Hy.

  From the relational expression (b), the X-axis correction coefficient is as shown in (c). The Y-axis correction coefficient is as shown in (d). Thereby, the correction coefficient 46 for obtaining the magnetic field measurement values in the direction of the reference line 24 and the direction of the crossing straight line 25 is obtained. This is logically the same, but when the computer processes, the arithmetic processing becomes relatively complicated. Therefore, a large number of correction coefficients assuming such an angle shift are calculated and held in advance.

  If the maximum possible value of β is 5 degrees, for example, even if correction values corresponding to 0.1 degrees are prepared, it is about 50. By applying all the correction values, when the zero cross points 44 of the measurement values of the first measurement result 38 and the second measurement result 40 coincide in the X-axis direction, the correction value may be adopted. The correction coefficient calculation means 48 shown in FIG. 3 may be configured by a computer that executes such calculation processing.

  Note that the rotary table 56 shown in FIG. 3 can have a rotation axis perpendicular to the plane including the reference line 24 and the crossing straight line on the intersection 54 of the reference line 24 and the crossing straight line. The rotary table 56 is used for rotating a magnetic field measurement object. A first fixing means is provided at the periphery. The first fixing means 34 is a support base 50 such as a plate or a clamp. When the rotary table 56 is rotated 180 degrees and the support base 50 moves along with the rotation of the rotary table 56, it can be moved from the first fixed point 30 to the second fixed point 32. Thereby, if the moving mechanism in which position accuracy is adjusted is used, the positioning of the magnet piece 28 at the first fixed point 30 and the second fixed point 32 can be performed quickly and accurately.

FIG. 6 is a flowchart of a specific magnetic field measuring method.
Specifically, the magnetic field measurement proceeds as shown in this figure. First, in step S11, the magnet is set to an initial state. That is, the magnet piece 28 is supported on the first fixed point 30. Next, the triaxial sensor 14 is set at the reference point 22 in step S12. Subsequently, in step S13, the triaxial sensor 14 is moved along the X axis. That is, it moves on the reference line 24. In step S14, magnetic field measurement in the X-axis and Y-axis directions is performed.

  When the magnetic field measurement is completed, a first measurement result 38 is acquired. In step S15, the center zero cross point 44 (first) is detected. In step S16, the magnet piece 28 is revolved 180 degrees. Thus, the magnet piece 28 is supported at the position of the second fixed point 32. In step S17, the direction of the surface of the magnet piece 28 facing the three-axis sensor 14 is not changed, and the magnet piece 28 is rotated 180 degrees about the intersecting straight line 25 as an axis. Thus, the magnet piece 28 can be set in a mirror image relationship. In step S 18, the magnet piece 28 is set at the reference point 22. In step S19, the triaxial sensor 14 is moved along the X axis. In step S20, magnetic field measurement in the X-axis and Y-axis directions is performed. Thus, the second measurement result 40 can be acquired. In step S21, the center zero cross point 44 (second) is detected.

FIG. 7 is a flowchart of the correction coefficient calculation processing operation.
In step S31, the acquired zero cross points (first and second) on the X axis are compared. In step S32, it is determined whether or not the positions on the X axis match. If the result of this determination is yes, there is no need for correction, and the process is terminated. If no, the process proceeds to step S33. In step S33, the correction value table storing a number of correction coefficients already described is referred to. In step S34, the measurement values of the first measurement result 38 and the second measurement result 40 are corrected with the acquired correction coefficient. In step S35, the zero cross points (first and second) are compared. In step S36, it is determined whether or not the positions on the X axis match. When the result of this determination is yes, the process proceeds to step S37, and the correction value used is set as a correction coefficient used during actual measurement. If no, the process returns to step S33, and the correction coefficient search is repeated in steps S33 to S36.

  6 and 7, the three-axis sensor is moved in the X-axis direction, and the angle deviation correction coefficient when viewed from the Z-axis direction of the three-axis sensor on the XY plane is acquired. . In exactly the same manner, the 3-axis sensor is moved in the Y-axis direction, and an angle deviation correction coefficient when viewed from the X-axis direction of the 3-axis sensor on the YZ plane is acquired (step S38 in FIG. 7). Further, the three-axis sensor is moved in the Z-axis direction to obtain an angle deviation correction coefficient when viewed from the Y-axis direction of the three-axis sensor on the ZX plane (step S39 in FIG. 7). Note that the angle shift when viewed from the Z-axis direction moves the sensor in the X-axis direction by disposing a magnet piece on the Y-axis. The angle deviation when viewed from the X-axis direction is such that a magnet piece is arranged on the Y-axis and the sensor is moved in the Z-axis direction. As for the angular deviation when viewed from the Y-axis direction, it is preferable to dispose a magnet piece on the X-axis and move the sensor in the Z-axis direction. According to this method, the correction coefficient can be acquired by arranging the magnet only on the XY plane. Therefore, a special mechanism for disposing the magnet on the Z axis is unnecessary, and a device having a known configuration as described in Patent Document 1 can be used as it is. As described above, the angle deviation correction coefficient when viewed from the Z-axis direction, the X-axis direction, and the Y-axis direction is acquired and set in the apparatus.

  When the correction coefficient obtained by the above arithmetic processing is used, the magnetic field obtained while moving the three-axis sensor 14 using the actuator 20 while fixing the actual measurement object on the rotary table 56 or the like. A precise three-dimensional magnetic field can be measured by correcting the measured value.

1 is a plan view showing a magnetic field measuring apparatus according to Embodiment 1. FIG. FIG. 2 is an explanatory diagram showing the nature of the measured values. It is explanatory drawing explaining the relationship between the magnetic force line which a magnet generate | occur | produces, a magnetic field measured value, and the inclination of the triaxial sensor. It is a principle figure of the apparatus which can correct | amend said measurement error. It is comparison explanatory drawing of a 1st measurement result and a 2nd measurement result. It is explanatory drawing which shows how to obtain | require the correction coefficient of a magnetic field measurement value. It is a flowchart of a specific magnetic field measurement method. It is a correction coefficient calculation processing operation flowchart.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Magnetic field measuring device 12 Detection element 14 3-axis sensor 16 Arm 18 Magnetic field measurement mechanism 20 Actuator 22 Reference point 24 Reference line 25 Crossing straight line 26 Sensor drive means 28 Magnet piece 30 1st fixing point 32 2nd fixing point 34 1st fixing means 36 Second fixing means 38 First measurement result 40 Second measurement result 42 Measurement result storage means 44 Zero cross point 46 Correction coefficient 48 Correction coefficient calculation means 50 Support base 52 Sensor moving mechanism 54 Intersection 56 Rotary table 58 Switching mechanism 60 Support Plate 62 side

Claims (6)

A triaxial sensor equipped with a detecting element capable of individually measuring magnetic fields in three axial directions orthogonal to each other;
An actuator that freely moves an arm that supports the three-axis sensor in three orthogonal directions set in the magnetic field measurement mechanism;
A pair of reference points is set on any one of the three axes set in the magnetic field measurement mechanism, the actuator is driven, and the 3 points along the reference line connecting the pair of reference points. Sensor driving means for linearly moving the axis sensor;
A first fixed point and a second fixed point are set on an intersecting straight line orthogonal to the reference line with the reference line interposed therebetween, and the same magnet piece is placed at the first fixed point and the second fixed point. A first fixing means and a second fixing means configured to support the mirror images in a mirror image relationship with each other;
Measuring the magnetic field in the direction of the reference line and the direction of the crossing line when the three-axis sensor is moved from one to the other on the reference line with the magnet piece supported at the first fixed point. When the triaxial sensor is moved from one side to the other on the reference line in a state where the result is stored in the storage device as the first measurement result, and the magnet piece is supported on the second fixed point, Measurement result storage means for storing a result of measuring the magnetic field in the direction of the reference line and the direction of the intersecting straight line in a storage device as a second measurement result;
Of the first measurement result and the second measurement result, the zero cross point of the magnetic field measurement value in the direction of the reference line is compared, and when both do not match, the direction of the reference line of the triaxial sensor and the A correction coefficient for correcting the magnetic field measurement value in the direction of the intersecting straight line is selected, and a correction coefficient matching the two is set as a correction coefficient for obtaining the magnetic field measurement value in the direction of the reference line and the direction of the intersecting straight line. A magnetic field measuring apparatus comprising a correction coefficient calculating means. The magnetic field measurement apparatus according to claim 1,
The first fixing means and the second fixing means comprise one support base that supports the magnet piece, and a mechanism for moving the support base from the first fixing point to the second fixing point is provided. Magnetic field measuring apparatus characterized by the above. The magnetic field measurement apparatus according to claim 2,
The first fixing means and the second fixing means comprise a single support base for supporting the magnet piece, and the support base is located at the intersection of the reference line and the intersecting straight line and intersects the reference line. A magnetic field measuring apparatus arranged on a rotary table having a rotation axis perpendicular to a plane including a straight line. The magnetic field measurement apparatus according to claim 2 or 3,
A magnetic field measuring apparatus comprising a switching mechanism for switching a support state of the magnet pieces so as to have a mirror image relationship on the support base. In the magnetic field measuring apparatus according to any one of claims 1 to 3,
The magnetic piece is fixed to a support plate having a side surface parallel to the reference line and perpendicular to a plane including the reference line and the intersecting straight line. A triaxial sensor equipped with a detecting element capable of individually measuring magnetic fields in three axial directions orthogonal to each other;
An actuator that freely moves the arm that supports the three-axis sensor in the three-axis directions orthogonal to each other set in the magnetic field measurement mechanism, and any one of the three axes set in the magnetic field measurement mechanism A sensor driving means for setting a pair of reference points on the upper surface, driving the actuator, and linearly moving the three-axis sensor along a reference line connecting the pair of reference points;
On the intersecting straight line orthogonal to the reference line, a first fixed point and a second fixed point are set with the reference line in between,
Measuring the magnetic field in the direction of the reference line and the direction of the crossing line when the three-axis sensor is moved from one to the other on the reference line with the magnet piece supported at the first fixed point. And store the result as a first measurement result in the storage device,
The same magnet piece is supported on the second fixed point so as to be in a mirror image relationship with that when supported on the first fixed point,
Measuring the magnetic field in the direction of the reference line and the direction of the crossing line when the three-axis sensor is moved from one to the other on the reference line with the magnet piece supported at the second fixed point. Measurement result storage means for storing the result obtained in the storage device as a second measurement result;
Of the first measurement result and the second measurement result, the zero cross point of the magnetic field measurement value in the direction of the reference line is compared, and when both do not match, the direction of the reference line of the triaxial sensor and the A correction coefficient for correcting the magnetic field measurement value in the direction of the intersecting straight line is selected, and a correction coefficient matching the two is set as a correction coefficient for obtaining the magnetic field measurement value in the direction of the reference line and the direction of the intersecting straight line. A correction method for a magnetic field measuring apparatus.

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