JPH0352832B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic field measuring device that can perform highly accurate measurements with simple operation.

Conventionally used magnetic field measuring devices include magnetic sensing instruments, proton magnetometers, fluxgate magnetometers, and the like. However, magnetic sensing instruments require repeated measurements to eliminate various errors, and proton magnetometers require a considerable amount of power for excitation, are not completely continuous, and have a uniform magnetic field. If not, all the protons stop moving in the same phase and no signal is output.Furthermore, in a fluxgate magnetometer, when measuring horizontal and vertical component forces, direct current is passed through a compensation coil to calculate the average horizontal and vertical components. It is necessary to cancel out the component force, but it is difficult to maintain such a canceling magnetic field with an accuracy within 1 (γ) over a long period of time, and the disadvantages are that it is complicated to handle and difficult to perform highly accurate measurements. .

The present invention aims to eliminate the above-mentioned conventional drawbacks and realize a device that is easy to operate and can perform high-precision measurements. a magnetic element whose electromechanical coupling coefficient increases gradually and reaches a maximum value when a predetermined external magnetic field is applied; first and second coils disposed at one end and the other end of the magnetic element, respectively; and the magnetic element. means for applying an alternating current signal to cause the magnetic element to resonate in the first coil; means for applying a direct current to generate the predetermined external magnetic field; means for applying a signal current to the fourth coil while sequentially changing the magnitude and polarity;
means for detecting the voltage value of the detection signal generated in the coil; and the magnetic field strength and direction of the magnetic field in the direction of the magnetic element based on the magnitude and polarity of the signal current when the voltage value of the detection signal becomes minimum. A magnetic field measuring device comprising: a means for measuring a magnetic field; The drawings will be described in detail below.

First, the sensor section of the magnetic field measuring device of the present invention and its measurement principle will be explained with reference to FIGS. 1 and 2.

In the figure, 1 is a magnetic element, in particular, an element whose electromechanical coupling coefficient gradually increases with the application of an external magnetic field, and whose electromechanical coupling coefficient reaches its maximum value when a predetermined external magnetic field is applied, such as a ribbon of amorphous alloy. It is. Here, the electromechanical coupling coefficient is the proportion of energy that is converted into elastic energy and stored in the material, out of the energy given magnetically by magnetic fields and minute changes in magnetization, or by minute changes in stress and strain. It shows the proportion of energy that is converted into magnetic energy and stored within the material, out of the energy given elastically. Further, the value of the electromechanical coupling coefficient differs depending on the material and changes depending on the magnitude of the external magnetic field applied to the material. For example, in the ribbon 1 described above, the value is almost 0 or small in the absence of an external magnetic field, but when an external magnetic field is applied, it initially increases as the external magnetic field increases, and reaches its maximum value when a predetermined external magnetic field is applied. and then decreases as the external magnetic field increases further. For details on the electromechanical coupling coefficient, see, for example, "R&D Report No. 34 Amorphous Metal Materials with Progress in Applied Development"
(CMC Co., Ltd., published on November 16, 1982,
P96-99) etc.

Further, 2 is a first coil (hereinafter referred to as an excitation coil) for applying an alternating current that makes the ribbon 1 resonate, and 3 is a second coil for extracting a detection signal (hereinafter referred to as a detection coil). , 4 is a third coil (hereinafter referred to as an excitation bias coil) for applying the above-mentioned predetermined external (bias) magnetic field to the location of the excitation coil 2 of the ribbon 1; 5 is the ribbon 1;
This is a fourth coil (hereinafter referred to as a detection bias coil) for applying an external (bias) magnetic field to the disposed portion of the detection coil 3 while sequentially changing its strength and direction as described later.

The ribbon 1 is bent at a substantially right angle near its center, and one side 1a thereof is arranged substantially vertically, and the other side 1b is oriented in the direction A of the magnetic field to be detected. Further, an excitation coil 2 and an excitation bias coil 4 are arranged around one side 1a, and a detection coil 3 and a detection bias coil 5 are arranged around the other side 1b.
is installed.

A constant DC current is passed through the excitation bias coil 4, and a predetermined bias magnetic field is applied to the region of the ribbon 1 where the excitation coil 2 is disposed. is set to the maximum. In addition, here ribbon 1
The reason why the bias magnetic field is applied so that the electromechanical coupling coefficient of is approximately maximized is to enable the ribbon 1 to be excited most efficiently by the excitation coil 2, which will be described later.

When an alternating current input current is applied to the excitation coil 2, an alternating magnetic field is generated in the excitation coil 2, and the magnetic energy due to this alternating magnetic field is converted into vibration (elastic) energy in the ribbon 1. 1
becomes an oscillating state. On the other hand, the vibrational energy in the vibrating ribbon 1 is converted into magnetic energy in the ribbon 1, and an alternating current magnetic field is generated around the ribbon 1, so that an alternating current output voltage is generated in the detection coil 3.

At this time, when an input current 6 with a specific frequency shown in FIG. A voltage with a certain frequency is also generated, but we will not consider it here.) is generated.

By the way, the output voltage 7 is the other side 1b of the ribbon 1.
It varies depending on the polarity and strength of the magnetic field existing in direction A.

Considering the earth's magnetism as the magnetic field that exists here, when the other side 1b of the ribbon 1 faces north, the strength of the magnetic field is greatest, so the output voltage 7
indicates the maximum value. Next, when the other side 1b is rotated around one side 1a to face east, the strength of the magnetic field weakens and the voltage value becomes smaller (output voltage 7').
The minimum value is just east. If you then rotate it further and point it even slightly south, the polarity of the magnetic field will be reversed, so the phase will change by 180 degrees (output voltage 7''), and the closer you get to the south, the stronger the magnetic field will be, and the voltage value will change. (output voltage 7).

On the other hand, when a current is passed through the detection bias coil 5, a bias magnetic field is generated in the direction of the other side 1b.
A case may occur in which the output voltage value of the excitation coil 3 takes a minimum value as the magnetic field cancels out with the magnetic field. Therefore, it is possible to determine the strength and polarity of the magnetic field in direction A from the value and polarity of the current flowing through the detection bias coil 5 at this time.

Figures 3 to 6 show an embodiment of the magnetic field detection device of the present invention, in which three sensor sections are combined orthogonally to each other to measure the true direction and strength of the magnetic field. I am doing what I can. That is, in the figure, 10, 20, 30 are sensor parts, and the sensor parts 10, 20, 30 are amorphous alloy ribbons 11, 2 bent at a substantially right angle near the center thereof.
1, 31, excitation coils 12, 22, 32 and excitation bias coils 14, 24, 34 attached to one side 11a, 21a, 31a, and the other side 11
Detection coil 1 attached to b, 21b, 31b
3, 23, 33 and detection bias coils 15, 2
5, 35, and the other sides 11b, 21
b, 31b are mutually orthogonal x, y, z, respectively
They are arranged along the axial direction.

Further, 40 and 41 are multiplexers, 42 is a video amplifier, 43 is a synchronous detector, 44 is a low pass filter (LPF), 45 is a comparator, 46 is a signal generator, 47 is an excitation magnetic bias current source, 4
8 is a DA converter, and 49 is a microprocessor.

The excitation coils 12, 22, 32 are supplied with an alternating current of a specific frequency from a signal generator 46, and the excitation bias coils 14, 24, 34 are supplied with a predetermined direct current from an excitation magnetic bias current source 47. The ribbons 11, 21, and 31 are maintained in a resonant state. Detection coil 13, 23, 3
3 and detection bias coils 15, 25, 35 are connected to multiplexers 40 and 41, respectively,
It is designed to be switched and selected by a microprocessor 49.

Next, the operation will be explained using an example in which the total magnetic force and inclination angle of the earth's magnetism are measured. Here, the z-axis is assumed to be arranged in the vertical direction. First, the microprocessor 49 selects the coils in the x-axis direction, that is, the detection coil 13 and the detection bias coil 15, by the multiplexers 40 and 41, and the D-A converter 48 sends the detection bias coil 15 an electric current with a changed absolute value and polarity. Input signals sequentially. Based on the electric signal from the detection coil 13, the video amplifier 42 and the synchronous detector 4
3, a signal having the same frequency as the specific frequency of the signal generator 46, that is, a detection signal, is extracted, smoothed by a low-pass filter 44, and then passed to a comparator 45.
However, due to the bias magnetic field generated by the detection bias coil 15, the phase of the electric signal from the detection coil 13 changes by 180 degrees, and when the detection signal crosses the 0 level, the comparator 45
A pulse signal is then output to the microprocessor 49, and the value and polarity of the current passed to the detection bias coil 15 at this time are stored. Thereafter, in the same manner for the y-axis and z-axis, the value and polarity of the current flowing through the detection bias coils 25 and 35 when the detection signal crosses the 0 level are stored in the microprocessor 49. The above operation is repeated a predetermined number of times, the average value thereof is determined, and the strength and polarity of the magnetic field in the x-, y-, and z-axis directions are determined based on predetermined conversion coefficients.

Next, the microprocessor 49 processes the above x, y, z
From the strength and polarity of the magnetic field in the axial direction, the direction of the true magnetic field of the earth's magnetism and the strength of the magnetic field are determined by the calculations shown below.

That is, in FIG. 6, the horizontal component H becomes H=√ ² + ² (1), where X and Y are the magnetic field strengths in the x-axis direction and the y-axis direction, respectively. Also, the true magnetic field strength, that is, the total magnetic force F, is z
If the magnetic field strength in the axial direction is Z, then F=√ ₂ + ² ...(2). Also, the inclination angle I with respect to the horizontal component H of the total magnetic force F is I=tan ^-1 F/H (3). Furthermore, by correcting the declination D, the direction of true north can also be determined.

FIG. 7 shows a modification of the magnetic field measuring device of the present invention, in which the number of parts is reduced by using both the excitation coil and the detection coil, or the excitation bias coil and the detection bias coil. That is, in the figure, 5
0, 51, 52 are amorphous alloy ribbons, 5
3, 54, 55, 56, 57, 58 are coils,
The ribbons 50, 51, 52 are bent at right angles near the center, and one side 50a, 51a, 52
a in the y, z, and x axis directions, and the other side 50
b, 51b, and 52b are arranged toward the x, y, and z axis directions, respectively. The coils 53 and 56 are connected to the other side 50b of the ribbon 50 and one side 52a of the ribbon 52.
The coils 54 and 57 are arranged around the ribbon 5.
The coils 55 and 58 are arranged around the other side 52b of the ribbon 52 and the one side 51a of the ribbon 51. For example, when measuring the magnetic field in the x-axis direction, the coil 53 is used as a detection coil,
The coil 56 serves as a detection bias coil, and the coil 54 serves as a detection bias coil.
is selected as the excitation coil, and coil 57 is selected as the excitation bias coil. As for the electric circuit section, only the output of the signal generator and the output of the excitation magnetic bias current source are selectively applied to each coil 53 to 58 by a multiplexer, and the rest may be left as is.

As explained above, according to the present invention, there is provided a magnetic element whose electromechanical coupling coefficient gradually increases upon application of an external magnetic field, and whose electromechanical coupling coefficient reaches its maximum value when a predetermined external magnetic field is applied; first and second coils disposed at one end and the other end, respectively; third and fourth coils disposed at the first and second coil disposed portions of the magnetic element; means for applying an alternating current signal to the coil to cause the magnetic element to resonate, means for applying a direct current to the third coil to generate the predetermined external magnetic field, and a signal current to the fourth coil with a magnitude and polarity. a means for detecting the voltage value of the detection signal generated in the second coil; and a means for detecting the magnetic current from the magnitude and polarity of the signal current when the voltage value of the detection signal becomes minimum. Since it consists of a means for measuring the magnetic field strength in the direction of the element and the direction of the magnetic field, there are no moving parts, so measurements can be started immediately after power is turned on, and there is no need for complicated operations or handling. It is possible to measure the magnetic field strength and direction of magnetic flux with high accuracy in the direction of , and the sensor part can be installed separately from other parts, allowing remote sensing, and the distance between them can be set freely. Furthermore, since it can be configured with inexpensive magnetic elements, a small number of coils, and a simple electric circuit, it can be made at low cost and with low power consumption, and the magnetic field strength and direction of magnetic flux can be extracted as electrical signals. Therefore, there are advantages such as ease of connection with other electronic devices.

[Brief explanation of drawings]

The drawings are for explaining the present invention. FIG. 1 is a perspective view of the sensor section for explaining the basic principle of the magnetic field measuring device of the present invention, and FIG. 2 shows the input current and output in the sensor section of FIG. 1. An explanatory diagram showing the relationship with voltage, FIGS. 3 to 6 show an embodiment of the magnetic field measuring device of the present invention, and FIG. 3 is a perspective view of the sensor portion,
Figure 4 is a block diagram of the electric circuit, Figure 5 is a diagram showing the operation flow of the microprocessor, Figure 6 is a diagram showing the relationship between the total magnetic force of the earth's magnetic field and each component, and Figure 7 is a diagram showing the relationship between the total magnetic force of the earth's magnetic field and each component. FIG. 7 is a perspective view showing another embodiment. 1, 11, 21, 31... Amorphous alloy ribbon, 2, 12, 22, 32... Excitation coil,
3, 13, 23, 33...detection coil, 4, 1
4, 24, 34...excitation bias coil, 5, 1
5, 25, 35... detection bias coil, 40,
41... multiplexer, 43... synchronous detector,
44...Low pass filter, 45...Comparator, 46...Signal generator, 47...Magnetic bias current source for excitation, 48...D-A converter, 49...
Microprocessor.

Claims (1)

[Scope of Claims] 1. A magnetic element whose electromechanical coupling coefficient gradually increases upon application of an external magnetic field, and whose electromechanical coupling coefficient reaches a maximum value when a predetermined external magnetic field is applied; one end of the magnetic element and another end thereof; first and second coils respectively disposed at the ends; third and fourth coils disposed respectively at the first and second coils of the magnetic element; and the first coil. means for applying an alternating current signal to cause the magnetic element to resonate; means for applying a direct current to the third coil to generate the predetermined external magnetic field; and applying a signal current to the fourth coil while sequentially changing the magnitude and polarity. means for detecting the voltage value of the detection signal generated in the second coil; and a direction of the magnetic element based on the magnitude and polarity of the signal current when the voltage value of the detection signal becomes minimum. A magnetic field measuring device comprising means for measuring the magnetic field strength and direction of the magnetic field. 2. The magnetic field measuring device according to claim 1, wherein an amorphous alloy ribbon is used as the magnetic element.