JPH0355844B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a magnetic field stabilizing device, particularly a predetermined space necessary for adjustment and testing of a test object such as a flux valve (geomagnetic detector). The present invention relates to a magnetic field stabilizing device suitable for use in maintaining a magnetic field in a work space at a predetermined value during the working time.

[Conventional technology]

An example of a conventional magnetic field stabilizing device of this type will be described with reference to FIGS. 4 and 5.

In FIG. 4, 10 indicates a field coil assembly. This field coil assembly 10 includes a pair of field coils 11 and 12 that generate mutually opposing magnetic fields Hf, and both field coils 11 and 12 are connected to each other with the same dimensions and distance D according to a desired work space WA. It consists of a lead wire 13. In this example, both field coils 11 and 12
are roughly the same square shape, so the work space
WA has a rectangular parallelepiped shape.

In this conventional example, a pair of field coils 11,
The magnetic field in the work space WA defined by 12
In order to maintain H _s ′ at a constant value, the magnetic field sensor 30
, whose input shaft is connected to both field coils 11 and 12
so that it is approximately parallel to the common central axis X-X' of
Between the two field coils 11 and 12, that is, the work space
An _output signal _E
and a reference signal E _s corresponding to the required magnetic field H _s ′ in the working space WA, or a deviation signal e, is applied to a suitable electronic circuit 40 such as an amplifier, and its output signal is converted into the above-mentioned deviation signal. A magnetic field, with a polarity such that e decreases, which maintains the magnetic field H _s ' in the workspace WA at a desired value regardless of the disturbance field Hd by being fielded back to the field coil, in this example the field coil assembly 10. It constitutes a stabilizing device.

[Problem that the invention seeks to solve]

The conventional magnetic field stabilizing device described above includes a magnetic field sensor 3
Since the output signal _Ex of 0 is compared with the standard signal E _s and the output signal E of the magnetic field sensor 30 is operated to make the deviation signal e substantially zero, the output of the magnetic field sensor 30 generally does not become zero. Therefore, the magnetic field sensor 30 used in this magnetic field stabilizing device has many requirements such as high resolution, small zero point fluctuation, wide dynamic range, small scale factor fluctuation, and good linearity. They need to be satisfied at the same time. It was extremely difficult to satisfy so many demands at the same time.

[Means for solving problems]

The present invention provides a magnetic field stabilizing device that solves the above problems. For example, as shown in FIG.
A magnetic field sensor 30 for detecting the strength of the magnetic field in the work space WA is installed near the center of the magnetic field coils 11 and 12, and the input shaft of the magnetic field sensor 30 and the field coil 11,
The output of the magnetic field sensor 30 arranged in this way is sent to the field coils 11 and 12 via the electronic circuit 40.
This magnetic field stabilizing device has reference coils 21 and 22, and when placing the reference coils 21 and 22 near the magnetic field sensor 30, the reference coils 21 and 22 are connected to the work space WA. When a reference current I _s corresponding to the required magnetic field strength is supplied, the magnetic field generated by the reference coils 21 and 22 is applied to the magnetic field sensor 30.
It is arranged so that it is approximately constant with respect to.

[Effect]

In the magnetic field stabilizing device according to the present invention, if the automatic control system loop gain is selected to be large enough, the output signal of the magnetic field sensor becomes approximately zero, so the dynamic range of the magnetic field sensor may be narrow. Gain fluctuations have almost no effect on the magnetic field in the work space, and the linearity of the magnetic field sensor has an extremely small effect on the magnetic field in the work space, and the reference signal of the reference coil and the strength of the magnetic field in the work space are approximately the same. A linear relationship can be established, and the magnetic field in the workspace can be maintained at a desired value, in other words, the value required in the workspace, regardless of the disturbance field.

〔Example〕

Hereinafter, one embodiment of the present invention will be described with reference to FIGS. 1 and 2. In addition, in the same figure, the fourth and fifth
The same reference numerals as those in the drawings indicate the same elements, and a detailed explanation thereof will be omitted.

In the embodiment of the invention shown in FIGS. 1 and 2, a reference coil assembly 20 is provided as part of the magnetic field stabilizer. This reference coil assembly 20 includes a reference coil 21 and a reference coil 22 having the same shape and dimensions.
It consists of These reference coils 21, 21 are
The shape is smaller than that of the field coils 11 and 12. Further, the reference coils 21, 21 and the field coils 11, 12 are arranged to face each other so that their respective central axes are common. Further, the reference coil 21 and the reference coil 22 are connected to have the same polarity. Depending on the reference current I _s supplied to these coils 21 and ₂₂ , the dimensions of the coils 21 and 22 and the Select a shape. Further, the central axis of the reference coil assembly 20 is set such that the input axis of the magnetic field sensor 30 is parallel to the reference coil assembly 20 and the magnetic field H _s generated by the reference coil assembly 20 is approximately equal to the entire magnetic field sensor 30. That is, the reference coil assembly 2 is adjusted so that the magnetic field received by the magnetic field sensor 30 is constant.
0 is placed with respect to the magnetic field sensor 30. and,
An output signal ε corresponding to the input magnetic field Hi of the magnetic field sensor 30 is applied to the electronic circuit 40, and its corresponding output current If is applied to the field coil assembly 10.
The connection is such that the output current causes the magnetic field Hf generated by the field coil assembly 10 to bring the magnetic field in the direction of the input axis of the magnetic field sensor 30, that is, the input magnetic field Hi of the magnetic field sensor 30, close to zero. There is.

Next, the operating principle of the example of the present invention shown in FIG. 1 will be explained with reference to the functional block diagram of FIG. First, when a reference current _Is is applied to the reference coil assembly 20, the magnetic field sensor 30 located at the center of the reference coil assembly 20 detects the voltage generated by the reference coil assembly 20 depending on the reference current _Is . a magnetic field H _s and a working space at a suitable distance from the reference coil assembly 20;
The magnetic field Hi of the sum (vector sum) of the magnetic field Hs′ in WA
I can do it. The magnetic field sensor 30 provides an output signal ε corresponding to the magnetic field Hi to the electronic circuit 40. Electronic circuit 40 supplies its output current If to field coil assembly 10 . The magnetic field Hf generated by the field coil assembly 10 depending on the current If acts to bring the input magnetic field Hi of the magnetic field sensor 30 close to zero, as described above. That is, since the magnetic field sensor 30 is located at the input end of the negative feedback group, if the loop gain A of the automatic control system is selected to be sufficiently large, the input magnetic field Hi of the magnetic field sensor 30 becomes almost zero. Therefore, near the center of the field coil assembly 10, the magnetic field H _s ' in the work space WA located at an appropriate distance from the reference coil assembly 20
is the reference coil assembly 2 depending on the reference current I _s .
0 is always almost equal to the magnetic field H _s created by H s and can be held constant almost independently of the external magnetic field H _x . However, each of the magnetic fields H _x , H _s ′, H _s , Hi, and Hf is a component of the magnetic field in the direction of the input axis of the magnetic field sensor 30 .

In the magnetic field stabilizing device according to the present invention as described above, since the input to the magnetic field sensor 30 is almost zero, the dynamic range of the magnetic field sensor 30 may be narrow, and gain fluctuations can be handled easily. It has almost no effect on the magnetic field H _s ′ in space WA. In addition, the linearity of the magnetic field sensor 30 is not related to the linearity between the reference current I _s and the magnetic field H _s '. That is, there is a great advantage that the linearity of the magnetic field sensor 30 is no longer important.

Next, another embodiment of the magnetic field stabilizing device according to the present invention will be described with reference to FIG. 3, which is a perspective view thereof.

In the example of the present invention shown in FIG. 3, three sets of the magnetic field stabilizer and field coil assembly of the present invention shown in FIG. (input axis) are arranged parallel to three orthogonal axes X-X', Y-Y', and Z-Z', respectively. In addition, in the same figure, 10,2
0, 30, 40, I _s10 is the field coil assembly of the X-X′ axis system, the reference coil assembly, the magnetic field sensor,
Electronic circuit, reference current, 100, 200, 30
0,400, I _s100 is the field coil assembly, reference coil assembly, magnetic field sensor, electronic circuit, reference current in the Y-Y' axis system, and 1000,200
0, 3,000, 4,000, and I _s1000 currents respectively indicate the field coil assembly, reference coil assembly, magnetic field sensor, electronic circuit, and reference current in the Z-Z' axis system. Further, reference numeral 4 indicates a test object in the work space WA.

In such a configuration, the reference current I _s10 of each system,
By selecting appropriate values for I _s100 and I _s1000 ,
It is possible to keep the magnetic field in the working space constant in any direction and strength.

Although the magnetic field stabilizer for one-axis control and three-axis control has been described above, the present invention is not limited to this example, and can of course be applied to a two-axis case.
If the magnetic field on one axis is zero, it is also possible to omit the reference coil assembly for that axis, and furthermore,
The field coil assembly and the reference coil assembly need not be limited to two coils each. For example, the number of field coils and reference coils may be one or several, and if there is only one field coil, it may be a solenoid-type coil that is elongated in the direction of its central axis. Further, the magnetic field sensor may also have a structure such as two-axis input or three-axis input.

Furthermore, the shape of the field coil defining the work space WA to which the present invention is applied does not need to be limited to a rectangle, and may be any desired shape such as a circle.

It will be apparent to those skilled in the art that many other changes can be made without departing from the spirit of the invention.

〔Effect of the invention〕

As described above, in the magnetic field stabilizing device according to the present invention, the input to the magnetic field sensor 30 is almost zero, so the dynamic range of the magnetic field sensor 30 may be narrow, and gain fluctuations can also be handled easily. It has almost no effect on the magnetic field H _s ′ in space WA. In addition, the linearity of the magnetic field sensor 30 is not related to the linearity between the reference current I _s and the magnetic field H _s '. That is, there is a great advantage that the linearity of the magnetic field sensor 30 is no longer important.

[Brief explanation of drawings]

FIG. 1 is a perspective view of one example of the present invention, FIG. 2 is a circuit diagram thereof, FIG. 3 is a perspective view of another example of the present invention, and FIG.
The figure is a perspective view of a conventional example, and FIG. 5 is its circuit diagram. In the figure, 10, 100, and 1000 are field equalizer assemblies, 20, 200, and 2000 are reference coil assemblies, 30, 300, and 3000 are magnetic field sensors, and 40, 400, and 4000 are electronic circuits, respectively.

Claims (1)

[Scope of Claims] 1. A magnetic field sensor for detecting the strength of the magnetic field in the working space is provided near the center of a field coil that defines a working space, and the input axis of the magnetic field sensor and the central axis of the feed coil are approximately equal to each other. A magnetic field stabilizer which is arranged in parallel and feeds back the output of the magnetic field sensors arranged in this way to the field coil via an electronic circuit, which has a reference coil, and this reference coil is connected to the magnetic field sensor. When this reference coil is supplied with a reference current corresponding to the magnetic field strength required in the working space,
A magnetic field stabilizing device characterized in that the reference coil is arranged so that the magnetic field generated by the reference coil is substantially constant with respect to the magnetic field sensor.