JP2003344514A - Method of detecting geomagnetic azimuth and geomagnetic azimuth sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the overall size and the cost of a sensor while simplifying the circuitry by making it possible to detect the azimuth with sufficient accuracy although the output accuracy of a second sensor is lowered when geomagnetic azimuth is detected based on the outputs from first and second magnetic sensors secured while being spaced apart by a specified angle in their fixed directions. <P>SOLUTION: With regard to geomagnetism He making an angle θ or (180°-θ) with the plus direction of X-axis, the first magnetic sensor S1 generating an output proportional to sinθ is secured to direct the Y-axis direction, and the second magnetic sensor S2 for judging to which range of (-90° to 90°) or (90° to 270°) the θ belongs is secured to direct a direction separated by a specified angle α (α≠180°) from the direction of the first magnetic sensor S1. The field detection accuracy of the second magnetic sensor S2 is set lower than that of the first magnetic sensor S1. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting a geomagnetic direction and a geomagnetic direction sensor.

[0002]

2. Description of the Related Art A geomagnetic direction sensor that outputs the geomagnetic direction as an electric quantity is used for CRT geomagnetic correction, detection of the current position of a navigation system, etc., and has conventionally been of the fluxgate type. FIG. 7 shows a fluxgate type geomagnetic direction sensor, in which an X-axis detection winding Cx and a Y-axis detection winding Cy are wound at an angle of 90 ° on a toroidal core C around which an excitation winding C0 is wound. The pulse current is passed through the exciting winding C0, and the magnetic resistance to the external magnetic flux φ passing through the detecting winding is alternately changed to ∞ and a low finite value in a pulse cycle. An output is induced in each detection winding by a magnetic flux change based on the convergence and release of the passing external magnetic flux φ due to the change. In this case, the induced voltage in the detection winding based on the magnetic flux φ ′ generated by the pulse current of the excitation winding is canceled, so that the output of the detection winding is not affected.

In the above description, the Y-axis detection system and the Y-axis detection system have substantially the same characteristics except that their orientation directions are shifted by 90 °. Therefore, if the angle between the geomagnetism and the X-axis plus direction is θ and the magnetic field strength is He, then Y
The output Vy of the axis detection winding is given by Vy = KHe · cos θ, the output Vx of the X-axis detection winding is given by Vx = KHe · sin θ, and when K is negative and Vy and Vx are illustrated, as shown in FIG. Yes,
When the direction of the Y-axis coincides with the direction of the earth's magnetism and becomes θ = 90 °, that is, when the direction of the sensor is oriented north-south with respect to the Y-axis detection system axis, Vx = −┃K
┃, Vy = 0. Furthermore, the relationship between the sensor direction and the positive / negative of the outputs Vx and Vy with reference to the Y-axis detection system axis is as shown in Table 1.

[Table 1] The angles for northeast, southeast, southwest, and northwest are both outputs V described above.
It can be calculated by sending x and Vy to a predetermined arithmetic circuit.

[0004]

The above fluxgate type geomagnetic direction sensor is a soul because it uses a toroidal core, and is not suitable for miniaturization. Further, the excitation winding must be wound around the entire toroidal core, and the impedance of the excitation winding is high, the excitation speed is slow, and the detection sensitivity is poor.

Therefore, it has been proposed to use a magneto-impedance effect element, a magneto-resistive effect element or the like. In this case, the principle of the flux gate type geomagnetic direction sensor is used. That is, a sensor with high identical detection accuracy is used for both the Y-axis sensor and the X-axis sensor, and as shown in FIG. 9, a Y-axis sensor system that generates a Y-axis output Vy = KHe · cos θ and an X-axis output Vx = KHe. The orientation of the X-axis sensor system that generates sin θ is fixed at 90 °, and the geomagnetic direction θ is calculated from both outputs Vx and Vy. In order to give the above-mentioned magneto-impedance effect sensor or magneto-resistive effect sensor a predetermined high detection accuracy, it is necessary to apply a bias or a negative feedback and to increase the exciting current. Therefore, both the Y-axis sensor and the X-axis sensor are required. As long as high detection accuracy is given,
The size of the entire sensor is inevitably increased. This will be described below with reference to the magnetic impedance effect sensor.

The magneto-impedance effect element includes
A zero magnetostrictive or negative magnetostrictive amorphous alloy wire, a ribbon, a sputtered film, or the like having an outer shell portion in which magnetic domains whose spontaneous magnetization directions are opposite to each other with respect to the wire circumferential direction are alternately separated by domain walls is used. There is. The inductance voltage component in the output voltage across both ends of the magneto-impedance effect element generated when a high-frequency current is passed through the element is not easily magnetized in the circumferential direction due to the circumferential magnetic flux generated in the cross section of the wire. It occurs because the shell is magnetized in the circumferential direction. Therefore, the circumferential magnetic permeability μ _θ
Depends on the circumferential magnetization of the outer shell. Thus, when an external magnetic field is applied to the energized amorphous element, the outer magnetic flux portion is easily magnetized in the circumferential direction due to the composition of the circumferential magnetic flux due to the energization and the element axial direction external magnetic field component. The direction of the magnetic flux acting on is deviated from the circumferential direction, so that the circumferential magnetization is less likely to occur, and the circumferential magnetic permeability μ _θ changes. That is, if the deviation of the magnetic flux from the circumferential direction when the axial external magnetic field component acts is Ψ, the circumferential magnetic flux is reduced by cos Ψ times, and the rotational magnetization reduces μ _θ . Therefore, this μ
By the decrease of _θ, the inductance voltage is reduced. Further, the energizing current frequency is MHz O - When Da, appearing high frequency skin effect is large, the skin depth δ = (2ρ / wμ _θ) as the ^{1/2 (mu} _theta mentioned above, circumferential permeability, ρ is electrical resistivity, w is the angular frequency) is changed by mu _theta, as the mu _theta is the so changed by the parallel external magnetic field component, parallel external magnetic field component the resistance voltage of in the element ends between the output voltage Will fluctuate with.

Therefore, both the above-mentioned inductance voltage component and resistance voltage component due to the external magnetic field, that is, the output voltage across the element (the variation of the output voltage due to this external magnetic field is called the magnetic impedance effect) is caused by the external magnetic field component. Although varied, even if the deviation Ψ of the magnetic flux from the circumferential direction when the external magnetic field component acts becomes ± depending on whether the magnetic field is positive or negative, the sign of cos Ψ does not change. As indicated by h in (a) of FIG. 6, the characteristic becomes symmetric, and the polarity of the external magnetic field cannot be determined.

Therefore, in the magneto-impedance effect sensor, a bias magnetic field of Hb is applied to output positive and negative in correspondence with the positive and negative of the time to be detected, and further negative feedback is applied for linearity. As shown in (b), the magnetic field Hex has a linear characteristic which is asymmetrical and whose detection accuracy is high and whose polarity can be determined. This asymmetric linear characteristic

[Equation 1] V = KHex (1) Can be expressed as

Conventionally, in FIG. 9, it is known to use the same magnetic impedance effect sensor with high detection accuracy for both the X-axis magnetic sensor and the Y-axis magnetic sensor. In FIG. 9, if the direction of the geomagnetism (intensity He) is θ with respect to the X-axis plus direction, the parallel geomagnetic component hy to the Y-axis magneto-impedance effect sensor is hy = He · sin θ, and therefore the Y-axis magnetic field From the equation (1), the output Vy of the impedance effect sensor is Vy = KHe · sin θ, and the parallel geomagnetic component Hx to the X-axis magneto-impedance effect sensor is Hx = He · cos θ. The output Vx of the effect sensor is expressed by the equation (1)
Therefore, Vx = KHe · cos θ. Then, as shown in FIG. 10, the geomagnetic azimuth θ is detected from Vy and Vx, and if an error occurs in any output, for example, Vx ±
When an error of ΔV occurs, an azimuth error of ± Δθ occurs. Therefore, the detection accuracy of both magneto-impedance effect sensors is set to the same high accuracy.

It is an object of the present invention to first separate a predetermined angle.
When the orientations of the magnetic sensor and the second magnetic sensor are fixed, and the orientation of the geomagnetism is detected from the outputs of both sensors, the orientation can be detected with sufficient accuracy, although the output accuracy of the second magnetic sensor is lowered. In this way, it is possible to reduce the size of the entire sensor, simplify the circuit configuration, and reduce the cost.

[0011]

According to a first aspect of the present invention, there is provided a method for detecting a geomagnetic direction, in which a first magnetic sensor is arranged in a Y-axis direction or an X-axis direction, and a predetermined angle α (α ≠) from the direction of the first magnetic sensor.
180 degrees) and the orientation of the second magnetic sensor is fixed, and an angle signal proportional to sin θ or cos θ is output with respect to the geomagnetism whose angle to the X-axis plus direction is θ, and the output of the second magnetic sensor. And the θ is (−90 ° to 90 °),
The range of (90 ° to 270 °), the range of (0 ° to 180 °), and the range of (180 ° to 360 °) are determined to determine the azimuth of the geomagnetism from the angle signal. It is characterized by detecting.

In the geomagnetic direction sensor according to a second aspect of the present invention, the first magnetic sensor that produces an output proportional to sin θ with respect to the geomagnetism whose angle to the X-axis plus direction is θ or (180 ° −θ) is the Y-axis direction. Orientation is fixed at, and the above θ is (-90 ° to 9
0 °) and (90 ° to 270 °) in which the second magnetic sensor is separated from the direction of the first magnetic sensor by a predetermined angle α (α ≠ 180 °). The orientation is fixed in the direction, and the magnetic field detection accuracy of the second magnetic sensor is lower than the magnetic field detection accuracy of the first magnetic sensor.

In the geomagnetic direction sensor according to a third aspect of the present invention, the first magnetic sensor that produces an output proportional to cos θ with respect to the geomagnetism whose angle to the X-axis plus direction is θ or (360 ° −θ) is the X-axis direction. Orientation is fixed at, and the above θ is (0 ° to 180
Angle), (180 ° to 360 °), the direction in which the second magnetic sensor is separated from the direction of the first magnetic sensor by a predetermined angle α (α ≠ 180 °). It is characterized in that the orientation is fixed at, and the magnetic field detection accuracy of the second magnetic sensor is lower than the magnetic field detection accuracy of the first magnetic sensor.

According to a fourth aspect of the present invention, the first magnetic sensor and the second magnetic sensor are constituted by a magnetic impedance effect sensor having an asymmetric output characteristic with respect to an external magnetic field.

According to a fifth aspect of the present invention, the first magnetic sensor is a magneto-impedance effect sensor having asymmetric linearity by applying bias and negative feedback, and the second magnetic sensor is an asymmetric magneto-resistive effect sensor and Hall effect. A sensor etc. can be used.

According to a sixth aspect of the present invention, the first magnetic sensor comprises a magneto-impedance effect sensor having an asymmetric linearity by applying bias and negative feedback, and the second magnetic sensor has a biasing asymmetric magnetic impedance. According to the present invention, the first magnetic sensor is asymmetrical linearity by applying bias and negative feedback, and the second magnetic sensor is a twisted magneto-impedance effect element. And an asymmetrical magnetic impedance effect sensor, wherein the exciting current of the magneto-impedance effect element of the second magnetic sensor is lower than the exciting current of the magneto-impedance effect element of the first magnetic sensor. In the item 9, the angle α is 90 °.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a view showing an embodiment of a geomagnetic direction sensor according to the present invention. In FIG. 1, S1 is a first magnetic sensor, which is oriented and fixed in the Y-axis direction on a base P such as a substrate. S2 is a second magnetic sensor, which is oriented and fixed in the X-axis direction on the base P such as the substrate. That is, the orientation of the first magnetic sensor S1 is fixed at 90 ° in the clockwise direction. B is an arithmetic circuit.

He indicates a geomagnetic vector, which is in the direction of θ with respect to the positive direction of the X axis, and the first magnetic sensor generates an output V1 proportional to the Y axis direction component of the geomagnetism. That is, an output of V1 = KHe · sin θ is generated. In the second magnetic sensor, the direction θ of the geomagnetism is (-90 ° ~
(90 °) or (90 ° to 270 °), a signal for determining which range it belongs to, for example, +1 if the geomagnetic X-axis direction component He · cos θ for the second magnetic sensor S2 is positive,
If it is negative, -1 is output. The output V1 of the first magnetic sensor S1 and the discrimination signal V2 of the second magnetic sensor S2 are shown in the figure.

In the method of detecting the geomagnetic direction according to the present invention, if these output signals V1 and V2 are sent to the arithmetic circuit B and the output of the first magnetic sensor S1 is A, V2 will be +1.
When V2 is −1, θ = β, and θ = 180
Display ° -β.

FIG. 3 is a view showing another embodiment of the geomagnetic direction sensor according to the present invention. In FIG. 3, S1 is a first magnetic sensor, which is oriented and fixed in the X-axis direction on a base P such as a substrate. S2 is a second magnetic sensor, which is oriented and fixed in the Y-axis direction on a base P such as a substrate. B is an arithmetic circuit.

He indicates a geomagnetic vector, which is in the direction of θ with respect to the plus direction of the X axis, and is the first magnetic sensor S1.
Produces an output V1 proportional to the X-axis component of the earth's magnetism. That is, an output of V1 = KHe · cos θ is generated. In the second magnetic sensor S2, the direction of the geomagnetism θ is (0
(° to 180 °) or (180 ° to 360 °), a signal for determining to which range it belongs, for example, the second magnetic sensor S
+ If the geomagnetic X-axis direction component He · sin θ for 2 is positive
1 is output, and -1 is output when the output is negative, and the output V1 and the discrimination signal V2 are shown in FIG.

According to the geomagnetic direction detection method of the present invention, these output signals V1 and V2 are sent to the arithmetic circuit B,
When the output of the first magnetic sensor S1 is A, θ = β when V2 is +1 and θ = 360 ° when V2 is −1.
-Display β. A magnetic impedance effect sensor can be used as the first magnetic sensor S1 and the second magnetic sensor S2.

In this case, as described above, the first magnetic sensor is required to have a capability of detecting KHe.sin.theta. Or KHe.cos.theta. With high accuracy with respect to the geomagnetism of the azimuth .theta. And the intensity He. Asymmetric linearity with high detection accuracy is given. In addition, the second magnetic sensor is required to be able to discriminate the polarity with respect to the external magnetic field in order to generate the discrimination signal, and is provided with asymmetry. The second magnetic sensor is not required to have linearity, and if the polarity of the external magnetic field can be discriminated, further detection accuracy is not required.

FIG. 5 shows a magneto-impedance effect sensor with asymmetric linearity. In FIG. 5, MI
Is a magneto-impedance effect element, and a zero magnetostrictive or negative magnetostrictive Armophus wire, Armophus ribbon, sputtered Armophus film or the like can be used. Reference numeral 1 is a transmission circuit for supplying an exciting current such as a high frequency current or a pulse current to the magneto-impedance effect element MI. Two
Is a detection circuit, the magneto-impedance effect element
An external magnetic field component signal is output by demodulating a modulated wave based on a change in impedance between both ends of the element due to an element axial direction component (hereinafter referred to as an external magnetic field component) Hex of an external magnetic field applied to MI. 3f is a negative feedback magnetic field generating coil,
Reference numeral 3b denotes a bias magnetic field generating coil, and both coils 3f and 3b are arranged so that the generated magnetic field acts in the axial direction of the element MI.

FIG. 6 shows the output characteristic of the magneto-impedance effect sensor. In (a) of FIG. 6, h represents the relationship between the output voltage V and the external magnetic field component Hex when negative feedback and bias are not applied, which is symmetric nonlinearity, and the polarity (±) of the external magnetic field component Hex is determined. Can not. So the first
For the magneto-impedance effect sensor, the detection width of the external magnetic field component is set to ± ΔHex and bias is applied with the bias magnetic field strength Hb, and further negative feedback is applied, as shown in (b) of FIG. It has been given sex. In this case, if the external magnetic field segment strength is Hex, the length of the negative feedback generation coil is 1, the number of turns is N, and the ground resistance is R, the detection output V is

## EQU2 ## V = HexlR / N = KHex (2) On the other hand, in the second magneto-impedance effect sensor, as described above, linearity is not required as long as it is possible to determine the polarity of the external magnetic field component,
Negative feedback is not applied and only the bias Hb is applied, which is asymmetrical as shown in FIG. As described above, the second magneto-impedance effect sensor has asymmetry, and as long as the polarity of the external magnetic field component can be discriminated by this asymmetry, further sensitivity is not required. The exciting current can be made lower than that of the second magnetic impedance effect sensor to reduce the power consumption of the power supply.

As shown in FIG. 1, the output V1 of the first magnetic impedance effect sensor S1 when the orientation of the first magnetic impedance effect sensor S1 is fixed in the Y-axis direction is obtained.
If the direction of e is + θ with respect to the positive direction of the X axis,
The element axial direction component Hex of the first magneto-impedance effect sensor S1 of geomagnetism becomes He · sin θ, which is given by Equation 2
To

[Formula 3] V1 = KHe · sin θ (3) holds. On the other hand, since He.cos θ acts as an external magnetic field component in the element axial direction of the second magneto-impedance effect sensor S2 whose orientation is fixed in the X-axis direction,
From the asymmetrical characteristics shown in FIG. 6C, θ is 0 ° to 90 °.
When the angle θ is in the range of 270 ° to 360 °, the positive output V2 is generated, and when the angle θ is in the range of 270 ° to 360 °, the negative output V2 is generated, and those outputs V1 and V2 are generated.
Is the same as that shown in FIG.

Therefore, by the method for detecting the geomagnetic direction according to the present invention, these output signals are sent to the arithmetic circuit, and the first
Assuming that the output of the magnetic sensor is A, when V2 is +1
When θ = β and V2 is −1, θ = 180 ° −β can be displayed and the geomagnetic direction can be recognized.

Further, as shown in FIG. 3, when the output V1 of the first magnetic sensor S1 when the orientation of the first magnetic impedance effect sensor S1 is fixed in the X-axis direction, the direction of the geomagnetism He is determined to be the X-axis. If the direction is + θ with respect to the plus direction, the first magneto-impedance effect sensor S1
The element axial component Hex of is He · cos θ, which is substituted into Equation 2,

## EQU00004 ## V1 = KHe.cos.theta. (4) holds. On the other hand, since the second magnetic impedance effect sensor S2 fixed in the X-axis direction has He.sin.theta. Acting as an external magnetic field component in the element axis direction,
From the asymmetrical characteristics shown in FIG. 6C, θ is 0 ° to 18 °
A positive output V2 is generated when it belongs to the range of 0 °, and a negative output V2 when θ belongs to the range of 180 ° to 360 °.
And their outputs V1 and V2 are the same as those shown in FIG. Therefore, if these output signals are sent to the arithmetic circuit and the output of the first magnetic sensor is A by the method for detecting the geomagnetic direction according to the present invention, when V2 is +1 then θ = β and V2 is Is −1, θ = 360 ° −β
Can be displayed to recognize the geomagnetic direction.

The asymmetrical characteristics of the magneto-impedance effect element can be imparted by adding a twist to the element (wire) and using an asymmetrical current such as an alternating current or a pulsed current in which a direct current bias is superimposed on the exciting current. That is, as a result of the twist, the easiness of magnetization is induced on the surface of the element wire in the direction inclined from the wire circumferential direction to the wire axis direction, and the coercive force of the domain wall movement is increased. The magnetization vector is rotated in the easy magnetization direction by the asymmetrical excitation magnetic field due to the current, and μ _θ is increased. On the other hand, in the negative external magnetic field, the angle formed by the magnetization vector and the asymmetrical excitation magnetic field is 90 ° or more. , The magnetization vector cannot be reversed due to the increased coercive force and becomes non-rotation μ _θ
Is kept low and the output voltage becomes constant. Thus, the voltage output is asymmetrical depending on whether the external magnetic field is positive or negative. Therefore, the asymmetry of the second magneto-impedance effect sensor can be achieved by twisting the element instead of the bias magnetic field method.

Discrimination signal V of the second magnetic sensor in FIG.
As can be understood from 2 and the discrimination signal V2 of the second magnetic sensor in FIG. 4, when the geomagnetic direction sensor vibrates near the change point of the discrimination signal, the discrimination signal follows the vibration and vibrates between positive and negative. As a result, the azimuth display becomes unstable and the azimuth recognition becomes difficult. Therefore, it is preferable not to display the azimuth or to display a specific value in a desired range (for example, a range of about ± 5 °) near the change point of the discrimination signal. For example, the exciting current of the twist element is
A pulse current with a sharp change is applied, strong eddy current braking is applied to the domain wall movement, the magnetization vector is not rotated with respect to a low external magnetic field, and the magnetization vector is inverted with a large external magnetic field exceeding the braking. By providing a hysteresis characteristic that outputs binary in a desired external magnetic field range, a specific binary can be digitally displayed in the vicinity of the change point of the discrimination signal.

In the above embodiment, the first magnetic sensor S1
The angle α between the second magnetic sensor S2 and the second magnetic sensor S2 is 90 °, but if α ≠ 180 °, an appropriate angle, for example, 45 °
It can also be °.

The geomagnetic direction sensor according to the present invention is installed in a driver's seat of a car or mounted on a mobile phone, and is used for a navigation system for recognizing a current direction on a map image to determine a course and for a geomagnetic correction of a CRT. Can be used.

[0033]

According to the present invention, the first magnetic sensor and the second magnetic sensor
When detecting the geomagnetic direction using a magnetic sensor, the second
Even if the magnetic detection accuracy of the magnetic sensor is lowered, the geomagnetic direction can be detected with sufficiently high accuracy, and the size and simplification of the second magnetic sensor can reduce the size and simplification of the entire geomagnetic direction sensor. Particularly, in the case of the magneto-impedance effect sensor, the exciting current of the second magneto-impedance effect sensor can be lowered to reduce the battery power consumption, negative feedback can be omitted, and the geomagnetic direction sensor can be downsized and simplified. .

[Brief description of drawings]

FIG. 1 is a view showing an embodiment of a geomagnetic direction sensor according to the present invention.

FIG. 2 is a diagram showing a first magnetic sensor output and a second magnetic sensor discrimination signal of the embodiment shown in FIG.

FIG. 3 is a view showing another embodiment of the geomagnetic direction sensor according to the present invention.

FIG. 4 is a diagram showing a first magnetic sensor output and a second magnetic sensor discrimination signal of the embodiment shown in FIG.

FIG. 5 is a view showing a first magneto-impedance effect sensor used in the present invention.

FIG. 6 is a diagram showing output characteristics of a first magneto-impedance effect sensor and a second magneto-impedance effect sensor used in the present invention.

FIG. 7 is a view showing a conventional fluxgate type geomagnetic direction sensor.

8 is a drawing showing the X-axis detection output and Y-axis detection output characteristics of the flux gate type geomagnetic direction sensor shown in FIG. 7. FIG.

FIG. 9 is a view showing a conventional geomagnetic direction sensor using a magnetic impedance effect sensor.

10 is a diagram showing a direction detection method of the geomagnetic direction sensor shown in FIG.

[Explanation of symbols]

S1 First magnetic sensor S2 Second magnetic sensor B arithmetic circuit He geomagnetism θ Geomagnetic direction MI magneto-impedance element 1 Exciting current source 2 Detection circuit 3b Bias field generating coil 3f Negative feedback magnetic field generating coil

Claims (9)

[Claims] 1. A first magnetic sensor in the Y-axis direction or the X-axis direction, a predetermined angle α (α ≠ 18) from the direction of the first magnetic sensor.
The second magnetic sensor is oriented and fixed in a direction separated by 0 °), and the first magnetic sensor outputs an angle signal proportional to sin θ or cos θ for the geomagnetism whose angle with the X-axis plus direction is θ, and 2 The output of the magnetic sensor shows that θ is (-90 °
To 90 °), (90 ° to 270 °), or (0 ° to 180 °), (180 ° to 360)
The method for detecting the geomagnetic azimuth is characterized in that the geomagnetic azimuth is detected from the angle signal by discriminating to which range the angle belongs. 2. The angle with the plus direction of the X axis is θ or (18
0 ° -θ) geomagnetism, the first magnetic sensor that generates an output proportional to sin θ is fixed in the Y-axis direction,
The second magnetic sensor for determining which range of (-90 ° to 90 °) and (90 ° to 270 °) the predetermined angle α (α ≠) with respect to the direction of the first magnetic sensor. 180
A geomagnetic direction sensor, characterized in that the orientation is fixed in a direction separated by (°) and the magnetic field detection accuracy of the second magnetic sensor is lower than the magnetic field detection accuracy of the first magnetic sensor. 3. The angle with the plus direction of the X axis is θ or (36
0 ° -θ) for the geomagnetism, the first magnetic sensor that generates an output proportional to cos θ is fixed in the X-axis direction,
The second magnetic sensor for determining which range of (0 ° to 180 °) and (180 ° to 360 °) belongs to the direction of the first magnetic sensor at a predetermined angle α (α ≠ 180).
A geomagnetic direction sensor, characterized in that the orientation is fixed in a direction separated by (°) and the magnetic field detection accuracy of the second magnetic sensor is lower than the magnetic field detection accuracy of the first magnetic sensor. 4. The geomagnetic direction sensor according to claim 2, wherein the first magnetic sensor and the second magnetic sensor are magneto-impedance effect sensors having asymmetric output characteristics with respect to an external magnetic field. 5. The geomagnetic direction sensor according to claim 2, wherein the first magnetic sensor is a magneto-impedance effect sensor which has asymmetric linearity by applying bias and negative feedback. 6. The geomagnetic direction sensor according to claim 4, wherein the first magnetic sensor is biased and negatively feedbacked to be asymmetrical, and the second magnetic sensor is biased to be asymmetrical. 7. The first magnetic sensor is a magneto-impedance effect sensor having asymmetric linearity by applying a bias and a negative feedback, and the second magnetic sensor is asymmetrical magnetism by twisting the magneto-impedance effect element. The geomagnetic direction sensor according to claim 4, which is an impedance effect sensor. 8. The geomagnetism according to claim 4, wherein the exciting current of the magneto-impedance effect element of the second magnetic sensor is lower than the exciting current of the magneto-impedance effect element of the first magnetic sensor. Direction sensor. 9. The geomagnetic direction sensor according to claim 2, wherein the angle α is 90 °.