JPH07198407A - Magnetic measuring instrument - Google Patents

Abstract

PURPOSE:To provide a compact magnetism measuring instrument, which can detect the moving direction of a magnetic material with excellent sensitivity. CONSTITUTION:Three-axis components Hx, Hy and Hz of the magnetic field from a moving magnetic material are detected with a three-axis magnetism sensor 5 comprising a three-axis magnetism sensor element 1 and a sensor controller 2 The components are converted into the a computer 4. For example, Hz/Hx is computed in the computer 4. Then, signal is cauturned in theta+tan<-1>Hz/Hx and the change thereof are computed. The moving direction of the magnetic material is determined based on the values.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetometer capable of calculating the moving direction of a magnetic substance.

[0002]

2. Description of the Related Art Conventionally, the position and magnetic moment of a magnetic substance are
As a method of obtaining, as shown in FIG. 5, two 3-axis magnets are used.
Using a sensor and one 2-axis sensor, a magnetic field gradient of 5 components
And magnetic field triaxial components are measured, and the position and magnetic
There are some that calculate Is this method a magnetic material?
The three components of the strength of the magnetic field at the observation point P γ ′ apart from_x, H
_y, H_zAnd the magnetic moment is M_x, M_y, M_z, Distance
If the three components of the separation γ ′ are x, y, and z,

[0003]

[Equation 1]

In a static magnetic field,

[0005]

[Equation 2]

Therefore, among the magnetic field gradients in equation (d), the independent ones are

[0007]

[Equation 3]

[0008] Therefore, if the three components of the magnetic fields of H _x , H _y , and H _z and the five components of the magnetic field gradient of the formula (f) are measured, the magnetic moment M ′ and the position γ ′ are obtained from the formulas (a) and (b). be able to. In FIG. 5, the magnetic field gradient 5 component is

[0009]

[Equation 4]

Approximately, the three components of the magnetic field are
H _XB , H _YB and H _ZB are used.

[0011]

Although the position of the magnetic substance can be measured and the direction of movement can be measured by the above-mentioned conventional magnetic measuring device, practical magnetic field sensitivity cannot be obtained because the magnetic field gradient is used. In addition, since the sensor unit is composed of two three-axis magnetic sensors and one two-axis sensor, there is a problem that the sensor unit becomes large.

The present invention has been made in view of the above problems, and provides a miniaturized magnetic measuring device which can detect the direction of movement of a magnetic substance while ensuring sensitivity. It is an object.

[0013]

The magnetic measuring instrument of the present invention comprises a triaxial magnetic sensor, means for converting the magnetic field value detected by the triaxial magnetic sensor into a digital value, and generation of the detected magnetic substance. Three components of the magnetic field _Hx , _Hy , and _Hz
Per H _y / H _x , H _z / H _x , H _x / H _y , H _z /
Using the magnetic field component ratio calculation means for calculating H _y , H _x / H _z and H _y / H _z, and at least one of the calculated magnetic field component ratios, the moving direction calculation for calculating the moving direction of the magnetic substance. And means.

In this magnetometer, as shown in FIG.
For example, the measurement point is x = 0, y = 0, z = 0.
, The magnetic field detected by the magnetic substance is H_x, H_y, H_zAnd y
= 0, z = a (constant), magnetic substance in the x-axis direction
Is moving, θ = tan ^-1(H_z/ H_x) Magnetic material
Changes with the movement of the
Constant depending on the direction of movement, regardless of the direction of the air moment
Is. Therefore, this magnetometer is
(Eg H_z/ H_x), And based on this
The direction of movement can be calculated.

[0015]

The present invention will be described in more detail with reference to the following examples. FIG. 2 is a block diagram showing the configuration of a magnetometer according to an embodiment of the present invention. The magnetometer of this embodiment comprises a triaxial magnetic sensor element 1, a sensor controller 2, a signal converter 3 and a computer 4.

The three-axis magnetic sensor element 1 is installed at a measuring point and has three components of the magnetic field of a moving magnetic substance, H _x , H _y and H _z.
What can detect is used. The sensor controller 2 is 3
The axial magnetic sensor element 1 is driven and the detection signal from the triaxial magnetic sensor element 1 is processed. This 3-axis magnetic sensor element 1
And the sensor controller 2 constitute a triaxial magnetic sensor 5.

The signal converter 3 outputs from the sensor controller 2.
Detected signal V₁To the computer 4
No., that is, digital signal V₂Convert to. Computer
The data 4 is a detection signal converted to digital, that is, a detection signal.
Three components of outgoing magnetic field H_x, H_y, H _zIncorporate and generate 3 magnetic fields
To calculate each ratio of minutes and the direction of movement of magnetic material
Is calculated. The result is output from the computer 4 to the outside.
Power can be delivered.

In this magnetometer, the installation position of the triaxial magnetic sensor element 1, that is, the measurement point is x = 0, y = 0, z.
= 0, and the detection magnetic field at this measurement point is H _x , H _y , H _z
And Then, when the magnetic substance moves under the condition of y = 0 and z = a (constant), that is, when the position in the z direction is substantially constant and moves substantially parallel to the x axis, the computer 4 uses θ = tan ⁻¹ H
By calculating the _z / H _x, and calculates the change, by way of the change, and determines the movement direction, the result is output to the outside. The specific calculation method is applied to equation (10), ...

Next, the measuring principle used in the above-mentioned apparatus will be described in detail. Magnetic moment M '[W shown in FIG.
The magnetic field H '[A / m] generated at the observation point P by the magnetic substance of b · m] at the position vector γ' [m] is (the mark 'on the right shoulder of M'is used as a beltle symbol for convenience. Yes, the same applies to other characters),

[0020]

[Equation 5]

[0021] Here, the unit vectors in the X-, Y-, and Z-axis directions are i ′, j ′, and k ′, and M ′ [Wb · m],
γ '[m] and H' [AT / m] are defined as follows using respective axial components. M '= M _x i' + M _y j '+ M _z k' [Wb · m] (3) γ '= xi' + _y j '+ _z k' [m] (4) H '= H _x i' + H _y j '+ H _z k' [A / m] (5) At this time, from equation (1),

[0022]

[Equation 6]

[0023]

[Equation 7]

It becomes For example, M '[Wb · m] is M _x
= M _y = M _z > 0 [Wb · m], y = 0 [m], z
= 50 [m], H _x for x [m],
The changes in H _y and H _z [A / m] have the waveforms in FIG. These waveforms change variously depending on the direction of M '[A / m], and when M' [Wb · m] is unknown, the waveform was moved in the positive direction or negative direction in the X-axis direction and observed. An effective method has not been discovered so far, even if the direction of movement of the observation point is to be obtained in reverse from the magnetic field waveform. On the other hand, the inventor has found in the course of various studies that the ratio of the two components of the magnetic field has a strange property such as Hz / Hx.

Here, the observation point P is Y = 0 [m], and X is
When moving parallel to the axis direction, focus on from the observation field without the Y-axis component _{H 'xy = H x j'} + H z k ' [A / m] ... (9). On the XY plane, the angle θ _xz [ra
d]

[0026]

[Equation 8]

It is The change in θ _xz [rad] in the X-axis direction is calculated from the equation (8).

[0028]

[Equation 9]

It becomes If the observation points are moved at a constant velocity, equation (11) is equivalent to ∂θ _xy / ∂t [rad / s], that is, the angular velocity is means. Here, when y = 0 [m] and equations (6) to (8) are substituted into equation (11),

[0030]

[Equation 10]

It becomes The denominator of this expression is 2 for x
Is the following formula,

[0032]

[Equation 11]

It is From this equation, define the positive and negative denominator of Equation (12) depends only on the polarity of the z (m), M _x
≠ 0 [Wb · m] or M _z ≠ 0 [Wb · m] (1
Under the condition of 4), regardless of the characteristics of M '[Wb · m], when z> 0 ∂θ _xx / ∂x <0 (15) When z <0 ∂θ _xx / ∂x > 0 (16) Therefore, z ≠ 0 without changing the characteristics of z [m].
[M], the observation point is moved in the X-axis direction, and θ _xz [r
ad _x ] increase / decrease, the magnetic substance has M _x ≠ 0, or M
_{If z} ≠ 0, the direction of movement of the observation point can be determined.

Although the above description has been made assuming that the observation point is moved for convenience of explanation in the equation (1), it is of course applicable to the case where the observation point is fixed and the magnetic substance moves.
According to the numerical calculation, the condition of y = 0 [m] when moving is not a strict requirement for satisfying the equations (15) and (16), but an increase in the deviation from y = 0 [m]. According to the direction of M ′ [Wb · m], the formula (15)
It has been found to have the property of increasing the number of cases where (16) is not satisfied.

For example, for a motion on a straight line that does not satisfy y ≠ 0 [m], a movement that passes a point of x = y = 0 [m] but has an inclination from the X-axis direction x = y = 0 [ There is a movement that does not pass the point m] and is only in the X-axis direction. A movement that does not pass the point x = y = 0 [m] and that has an inclination from the X-axis direction. In the worst case, it can be understood that the movement coincides with the Y-axis direction. For this,

[0036]

[Equation 12]

By paying attention to, it is possible to determine that the movement is in the Y-axis direction. As for the above, the number of observation points is arranged laterally with respect to the traveling direction to deal with the problem. For the expression (1
We will deal with this by using the attention to 7) together with multiple observation points.

[0038]

According to the present invention, only one triaxial magnetic sensor is used to measure the direction of movement of a magnetic substance, and three magnetic sensors are used.
Since the axial magnetic field component is detected, the magnetic field component ratio is calculated, and the change is determined to determine the direction, the magnetic field gradient itself is used instead of the magnetic field gradient.
The orientation can be determined with sufficient sensitivity. Moreover, since the number of magnetic sensors used is small, it is possible to reduce the size of the magnetic measuring device.

[Brief description of drawings]

FIG. 1 is a diagram illustrating an example of measuring the direction of movement of a magnetic substance in a magnetometer of the present invention.

FIG. 2 is a block diagram showing a configuration of a magnetometer according to an embodiment of the present invention.

FIG. 3 is a diagram showing an observation system for explaining a principle of adoption of the magnetometer of the embodiment.

FIG. 4 is a diagram showing changes in each magnetic field component when the measurement point is changed in the X-axis direction in the same observation system.

FIG. 5 is a diagram illustrating an observation magnetic field of a conventional magnetometer.

[Explanation of symbols]

 1 3-axis magnetic sensor element 2 Sensor controller 3 Signal converter 4 Computer 5 3-axis magnetic sensor

Claims (1)

[Claims] 1. A three-axis magnetic sensor, a means for converting a magnetic field value detected by the three-axis magnetic sensor into a digital value, and three components H _x , H _y , and H of a magnetic field generated by the detected magnetic substance.
_{For z} , H _y / H _x , H _z / H _x , H _x / H _y , H _z
/ H _y , H _x / H _z and H _y / H _z A magnetic field component ratio calculating means and at least one of the calculated magnetic field component ratios are used to calculate the moving direction of the magnetic substance. A magnetometer comprising: a calculating unit.