JPH06174471A - Electronic azimuth meter - Google Patents

Abstract

PURPOSE:To provide an electronic azimuth meter capable of avoiding the error of the measured azimuth caused by the hysteresis phenomenon of magnetoresistive elements. CONSTITUTION:Individual circuit sections are controlled by a controller 2, a large current is certainly fed to a bias magnetic field coil L1 or L2 from a capacitor 7 to magnetically saturate magnetoresistive elements MR1-MR4 prior to measurement, then this large current is cut off, and the azimuth is measured while the magnetic hysteresis of the magnetoresistive elements MR1-MR4 is kept constant.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic compass,
In particular, it is suitable for an electronic azimuth meter in which the element for detecting the earth's magnetism is made of a ferromagnetic material and the error of the detected azimuth data based on the hysteresis phenomenon cannot be ignored.

[0002]

2. Description of the Related Art Conventionally, a small-sized and portable electronic azimuth meter utilizing a magnetoresistive element formed of a ferromagnetic material such as permalloy has been put to practical use.

FIG. 3 shows a typical circuit configuration of the electronic azimuth meter as described above. The magnetic sensor unit 1 is composed of four magnetoresistive elements MR1 to MR4 formed on a substrate such as glass (not shown) and connecting portions K1 to K4 connecting these to form a bridge circuit. ~ MR4 is formed by vacuum-depositing a ferromagnetic material such as permalloy, and the connecting portions K1 to K
4 is formed by vacuum-depositing an ordinary wiring material. Then, the magnetoresistive elements MR1 to MR4.
Are arranged so that their magnetic detection directions are orthogonal to each other between the adjacent magnetoresistive elements. A direct-current voltage is applied between the connecting portions K1 and K3 by the power source E, and the potential difference between the connecting portions K2 and K4 is applied to the amplifier circuit 3. Further, the magnetic sensor unit 1 is wound with bias magnetic field coils L1 and L2 that are orthogonal to each other and generate a bias magnetic field in a direction forming 45 ° with the magnetic detection directions of the magnetoresistive elements MR1 to MR4. Power sources Px and Py for supplying a constant current under the control of the control unit 2 are tangentially connected to each other. Note that, as shown in the upper right of FIG. 2, the direction of the bias magnetic field generated by the bias magnetic field coil L1 is the X-axis direction, and the positive direction is the right direction in the figure, and the bias magnetic field generated by the bias magnetic field coil L2 is the same. Is the Y-axis direction and the positive direction is the upper direction in the figure (that is, the X-axis and the Y-axis are fixed to the magnetic sensor unit 1).

The control unit 2 includes power supplies Px, Py and an amplifier circuit 3.
It is a circuit that sends a control signal to each circuit such as and controls them. That is, the control unit 2 alternately activates the power supplies Px and Py, alternately applies the bias magnetic field in the positive direction of the X axis or the positive direction of the Y axis to the magnetic sensor unit 1, and the connecting portion K2 in both states. , K4 is a circuit that sends a control signal to the amplifier circuit 3, the A / D conversion circuit 4 and the like in order to process the potential difference.
The amplifier circuit 3 is a circuit that inputs the potential difference between the connection portions K2 and K4 of the magnetic sensor unit 1 under the control of the control unit 2, amplifies the potential difference, and outputs the amplified potential difference to the A / D conversion circuit 4. A / D
The conversion circuit 4 is a circuit for converting the output of the amplification circuit 3 into a digital signal and sending it to the storage unit 5 under the control of the control unit 2. Under the control of the control unit 2, the calculation unit 6 also stores the data stored in the storage unit 5, that is, the bias magnetic field coil L.
Connection part K when a bias magnetic field of 1 is applied
2, the potential difference between K4 is amplified by the amplifier circuit 3 and is digitized by the A / D converter circuit 4 (corresponding to the X-axis direction component of the geomagnetism), and the bias magnetic field by the bias magnetic field coil L2. The potential difference between the connection portions K2 and K4 when the voltage is applied is amplified by the amplifier circuit 3 and digitized by the A / D converter circuit 4 (corresponding to the Y-axis direction component of the earth's magnetism). Then, the azimuth (the angle between the direction of the earth's magnetism and the positive direction of the Y axis) is calculated by taking in.

By the way, the reason why the bias magnetic field is applied to the magnetoresistive elements MR1 to MR4 by the bias magnetic field coils L1 and L2 as described above is as follows. That is, the resistance value of the magnetoresistive element decreases as the applied magnetic field becomes stronger irrespective of the direction of the applied magnetic field, as shown in FIG. The resistance value is standardized by the resistance value, that is, the standardized resistance value). Therefore, if the bias magnetic field is not applied, even if the direction of the geomagnetism can be discriminated, the direction (north facing or south facing) cannot be distinguished. Further, when the applied magnetic field is weak (at the geomagnetic level), the change in resistance is small and the measurement error is large as shown in FIG. Therefore,
As shown in the figure, a bias magnetic field is applied up to the point where the change in resistance to the applied magnetic field is the largest, and the geomagnetism is superimposed on this so that the resistance value changes depending on the direction of the geomagnetism, and even a slight change in the geomagnetic component It is designed so that a large resistance change can be obtained.

[0006]

However, the ferromagnetic magnetoresistive element used in the electronic azimuth meter as described above has the following problems.
There is a hysteresis phenomenon, and depending on the history of the applied magnetic field,
Even under the same applied magnetic field, different resistance values are shown (see FIG. 5). The error in the measurement direction resulting from this is relatively large and cannot be ignored. The present invention has been made in view of the above circumstances, and an object thereof is to provide an electronic azimuth meter capable of avoiding an error in a measurement azimuth caused by a hysteresis phenomenon of a magnetoresistive element.

[0007]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention first determines the magnetic resistance of a magnetoresistive element in order to make the magnetic history of the magnetoresistive element constant when detecting geomagnetism. A large magnetic field in a given direction was applied to magnetically saturate the magnetic field, and then the magnetic field was stopped to detect the geomagnetism.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to an embodiment shown in the drawings. FIG. 1 shows the circuit configuration of this embodiment. That is, the circuit configuration shown in FIG. 1 is substantially the same as that of the conventional example shown in FIG. 3 (note that in FIG. 1, a circuit unit having the same operation and function as the circuit unit in FIG. 3). 3 are attached with the same reference numerals as those of the circuit section in FIG. 3), a new capacitor 7, a charging power source Ec, and an on-state under the control of the control section 2.
Switches S1 and S2 which are in an off state and which intermittently charge the capacitor 7 from the charging power source Ec, and an on / off state which is under the control of the control unit 2 have both poles of the capacitor 7 at both ends of the bias magnetic field coil L1 or L2. Switches S3, S4 and S5 to be connected are added.

In the present embodiment having such a configuration,
The following operations are performed when measuring the azimuth. That is, when the switch (not shown) is operated with the positive direction of the Y-axis directed toward the direction for measuring the azimuth, first, the control signal is sent from the control unit 2 to the switches S1 and S2, 2, the switch is turned on, and the charging of the capacitor 7 by the charging power source Ec is started. Subsequently, a control signal is sent from the control unit 2 to the power supply Px, and as shown in FIG. 2, a current is made to flow from the power supply Px to the bias magnetic field coil L1 so that the magnetic sensor unit 1 is fixed in the positive direction of the X axis. (In this case, the actual bias magnetic field applied to each magnetoresistive element of the magnetic sensor unit 1 is such that the magnetic detection direction of the magnetoresistive element is from the X-axis direction). Since it is inclined by 45 °, the bias magnetic field generated by the bias magnetic field coil L1 is divided by √2).

Next, the control unit 2 switches the switches S1 and S2.
A control signal is sent to the switch, these switches are turned off (see FIG. 2), the above charging is stopped, and the control unit 2
2 sends a control signal to the switches S4 and S5 to turn them on, as shown in FIG. 2, whereby a large current is momentarily applied from the already fully charged capacitor 7 to the bias magnetic field coil L1. Flowing. In this case, the large current flowing in the bias magnetic field coil L1 has the same direction as the current flowing from the power supply Px to the bias magnetic field coil L1, and the magnetic sensor unit 1 receives a large magnetic field in the positive direction of the X axis. When applied, each magnetoresistive element is magnetically saturated (in this case also, the magnetic field applied to each magnetoresistive element is the above magnetic field divided by √2, but this is also an extremely strong magnetic field. And a magnetic field sufficient to magnetically saturate the magnetoresistive element).

After that, a control signal is sent from the control unit 2 to the switches S4 and S5, and these switches are turned off, as shown in FIG. Only the current from the power source Px flows through the magnetic field coil L1, and this causes the magnetoresistive element MR1.
A normal bias magnetic field and a magnetic field due to geomagnetism are applied to MR4. Then, at this time point, the control signal t (see FIG. 2) is sent from the control unit 2 to the amplification circuit 3, the A / D conversion circuit 4 and the like, and the potential difference between the connection portions K2 and K3 changes.
Is input to and amplified by the A / D conversion circuit 4 and stored in the storage unit 5 as data corresponding to the X-axis direction component of the geomagnetism.

As described above, after the data corresponding to the X-axis direction component of the geomagnetism is stored in the storage unit 5, the control unit 2
The control signal from the power supply Px stops the outflow of current from the power supply Px to the bias magnetic field coil L1 (see FIG. 2), and also stops the application of the bias magnetic field in the positive direction of the X axis.

After that, the control unit 2 sends switches S1 and S
A control signal is sent to 2 to turn on these switches (see FIG. 2), and the charging of the capacitor 7 by the charging power source Ec is started again. Subsequently, a control signal is sent from the control unit 2 to the power supply Py, and as shown in FIG. 2, a current is made to flow from the power supply Py to the bias magnetic field coil L2 to cause the magnetic sensor unit 1 to move in the positive direction of the Y axis. A bias magnetic field having a constant strength is applied (in this case, the actual bias magnetic field applied to each magnetoresistive element of the magnetic sensor unit 1 is the same as described above by the bias magnetic field coil L2. Divided by √2).

Next, the control unit 2 switches the switches S1 and S2.
A control signal is sent to the switch, these switches are turned off (see FIG. 2), the above charging is stopped, and the control unit 2
Sends a control signal to the switches S3 and S5, and these switches are turned on as shown in FIG. 2, so that the capacitor 7 which is already sufficiently charged momentarily becomes large in the bias magnetic field coil L2. An electric current flows.
In this case, the large current flowing through the bias magnetic field coil L2 is in the same direction as the current flowing from the power source Py into the bias magnetic field coil L2, and the magnetic sensor unit 1 has Y.
A large magnetic field in the positive direction of the axis is applied, and each magnetoresistive element is magnetically saturated (in this case, the magnetic field actually applied to each magnetoresistive element is the above magnetic field at √2). However, the magnetic field is still extremely strong,
Magnetoresistive elements are sufficiently magnetically saturated).

After that, a control signal is sent from the control unit 2 to the switches S3 and S5, these switches are turned off as shown in FIG. 2, and a large voltage is sent from the capacitor 7 to the bias magnetic field coil L2. The outflow of the current is stopped, and only the current from the power source Py flows in the bias magnetic field coil L2, whereby the normal bias magnetic field and the magnetic field due to the geomagnetism are applied to the magnetoresistive elements MR1 to MR4. Then, at this time, the control signal t (see FIG. 2) is sent again from the control unit 2 to the amplification circuit 3, the A / D conversion circuit 4, etc., and the potential difference between the connection portions K2, K3 is amplified by the amplification circuit 3. Further, it is converted into digital data by the A / D conversion circuit 4, and this is stored in the storage unit 5 as data corresponding to the Y-axis direction component of the geomagnetism.

As described above, the storage unit 5 stores the geomagnetic X
After the data corresponding to the axial component and the data corresponding to the Y-axis component of the earth's magnetism are stored, the arithmetic unit 6 takes in both of the above-mentioned data, executes the arithmetic operation based on these data, and The azimuth of the direction pointed by the Y axis is obtained, which is digitally displayed on a display unit (not shown) controlled by the control unit 2.

As described above, in the present embodiment, when data relating to the X-axis direction component of the earth's magnetism is obtained, immediately before that, an extremely strong magnetic field is applied once in the positive direction of the X-axis, and the magnetoresistive element. When MR1 to MR4 are magnetically saturated and then the application of this strong magnetic field is stopped to obtain the above-mentioned data, while the data relating to the Y-axis direction component of the geomagnetism is obtained, immediately before that, Since an extremely strong magnetic field is applied in the positive direction of the Y-axis to magnetically saturate the magnetoresistive elements MR1 to MR4, and then the application of the strong magnetic field is stopped, the above data is obtained. X axis or Y
When obtaining data relating to the axial component, the magnetoresistive element M
Since the magnetic histories of R1 to MR4 are constant, it is possible to avoid the error of the measurement direction data due to the difference of the histories.

[0018]

As described above in detail, according to the present invention, in detecting the geomagnetism, in order to make the magnetic history of the magnetoresistive element constant, first, the magnetoresistive element is temporarily moved in a predetermined direction. Apply a magnetic field to saturate it with geomagnetism,
After that, since it relates to the electronic azimuth meter which stops the application of the magnetic field and detects the geomagnetism, the electronic azimuth that can avoid the error in the measurement azimuth associated with the hysteresis phenomenon of the magnetoresistive element. It is possible to provide the total.

[Brief description of drawings]

FIG. 1 is a diagram showing a circuit configuration of an embodiment of the present invention.

FIG. 2 is a time chart showing ON / OFF of the switches shown in FIG.

FIG. 3 is a diagram showing a circuit configuration of a conventional example.

FIG. 4 is a diagram showing characteristics of a magnetoresistive element.

FIG. 5 is a diagram for explaining a hysteresis phenomenon in a magnetoresistive element.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Magnetic sensor part 2 Control part 7 Capacitor MR1-MR4 Magnetoresistive element L1, L2 Bias magnetic field coil Px, Py, E power supply Ec Charging power supply

Claims (2)

[Claims] 1. A magnetic detection means, a bias magnetic field generation means for applying a plurality of bias magnetic fields in different directions, and a magnetic field detection means for applying a bias magnetic field in a plurality of directions by the bias magnetic field generation means. An electronic azimuth meter comprising: an azimuth calculation means for calculating an azimuth from an output; and a magnetic saturation means for magnetically saturating the magnetic detection means. 2. Four magnetoresistive elements that are coupled in a bridge shape so that the magnetic detection directions of adjacent magnetoresistive elements are orthogonal to each other, and are wound around the magnetoresistive elements in a mutually orthogonal state. At least two bias magnetic field coils, voltage applying means for applying a constant voltage between two opposing coupling parts of the four magnetoresistive element coupling parts, and the two bias magnetic field coils alternately. First bias magnetic field coil driving means for generating a bias magnetic field in the magnetic field, and the four magnetic resistances when a bias magnetic field is generated in the bias magnetic field coil by the first bias magnetic field coil driving means. Detecting means for detecting a potential difference between two opposing coupling portions other than the two coupling portions to which the constant voltage is applied among the coupling portions of the element, and two potential differences detected by the detecting means. An electronic azimuth, comprising: an arithmetic means for calculating the azimuth from the second bias magnetic field coil; and a second bias magnetic field coil driving means for causing the bias magnetic field coil to generate a magnetic field in which the magnetoresistive element causes magnetic saturation. Total.