JPH0243152B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetometer constructed using a magnetometer.

There are two methods for measuring magnetic fields: a method using a magnetometer and a method using a magnetometer. A magnetometer directly gives the strength of the magnetic field at that location, but a flux meter itself has directionality and can only determine the strength of the component of the magnetic field in that direction. Then, you must move the magnetometer in various directions to find the direction of maximum output, and then measure the output at that time. Therefore, magnetometers are generally more convenient for measuring magnetic field strength.

Currently, optical magnetic resonance magnetometers are extremely sensitive as magnetometers, and are more sensitive than fluxgates, which are generally used as magnetometers. It doesn't make much sense. Recently, SQUID magnetometers that utilize the superconducting Josephson effect have been put into practical use, and they have a sensitivity that is 100 times that of optical magnetic resonance magnetometers. If it is a flux meter, constructing a magnetometer using this is extremely meaningful in the sense of obtaining an ultra-high sensitivity magnetometer.

The present invention aims to construct a magnetometer by combining magnetometers, thereby making it possible to perform measurements with high precision beyond the limitations of the machine precision of the device, thereby obtaining a magnetometer with extremely high sensitivity and precision. It is something to do.

The present invention proposes a method of configuring a magnetometer using a magnetometer from the above-mentioned perspective, and is not intended only for the case where a skid magnetometer is used, but is intended for use in the future. This generality can naturally be applied to the case where a magnetometer is constructed using a highly sensitive magnetometer.

The present invention uses three or more magnetometers, fixes each magnetometer so that its axes intersect so that only two axes are included in the same plane, and creates orthogonal coordinate axes with the origin at the intersection of the axes of these magnetometers. The direction of the axis of each magnetometer with respect to the coordinate axis is measured in advance, and the magnetic field component in the direction of each coordinate axis of the above orthogonal coordinates is calculated from the output of each magnetometer by vector calculation, and the direction and strength of the magnetic field are calculated. Provided is a magnetometer capable of determining the . In this case, if the magnetometers are placed perpendicular to each other from the beginning, the three components of the orthogonal coordinate system of the magnetic field can be measured immediately without any special calculations, but in practice, the magnetometers (generally It is extremely difficult to fix the axes of multiple objects (objects) so that they are perpendicular to each other, and it inevitably involves some errors. The angle between the axes of multiple objects that have already been placed and fixed can be measured relatively easily and with extremely high precision.
The angles that these axes make with the orthogonal coordinate axes must also be determined with high precision, and therefore, rather than fixing multiple magnetometers in advance with extremely accurate orthogonal alignment, the direction of each magnetometer with respect to the orthogonal coordinate axes is measured. death,
A more accurate result can be obtained by calculating the magnetic field using the result, and the present invention focuses on this point. The present invention will be explained below with reference to Examples.

FIG. 1 explains the function of the magnetometer, where F is the magnetometer and A is its detection axis. H represents the applied magnetic field as a vector, and the magnetometer detects the component Ha of H in the axis A direction.

FIG. 2 shows the arrangement of the magnetometer in the present invention,
This is an example using three magnetometers, Fx, Fy, Fz
are magnetometers, and x', y', and z' are detection axes of these magnetometers, which are fixed so as to intersect each other at approximately right angles at the zero point. The x', y', and z' axes do not need to be intentionally set at different angles from right angles, but they also do not need to be orthogonal with a particularly high degree of precision. Now there are three axes as shown in Figure 3.
For x', y', and z', consider orthogonal coordinate axes x, y, and z, and align the origin, x' axis, and x axis, and create the xy plane.
Align it with the x′y′ plane. In this way, x′, y′,
The deviation from the orthogonal coordinate x, y, z axis system of the z′ axis system is y
It is determined by the angle φ between the axis and the y' axis, the angle θ between the z axis and the z' axis, and the angle λ between the x axis and a plane containing both the z and z' axes. Therefore, these angles should be precisely measured in advance.

In Fig. 3, the magnetic field to be measured is indicated by a double arrow He. Here, if the unit vectors in the x', y', and z'3 axis directions are i', j', k', these are x, y,
Unit vector of z orthogonal axis system (100), (010) (001)
When expressed using φ, θ, and λ, it can be written as i'=1 0 0, j'=sinφ cosφ 0, k'=sinφ cosλ sinφ sinλ cosθ. The direction cosine of the magnetic field He to be measured with respect to the x, y, z orthogonal axis system is
Assuming h1, h2, h3, the magnitude of He is h0, He=h0h1 h2 h3 On the other hand, the Fx etc. of the magnetometer shows the magnitude of the components of Te in the x′, y′, and z′ axis directions as output. Therefore, if the respective outputs are Hx′, Hy′, Hz′, Hx′=He・i′, Hy′=He・j′, Hz′=He・k′, so i′=(1, 0 . Axial component Hx,
Hy, Hz is Hx Hy Hz=h0h1 h2 h3 ……(2), so substituting equation (2) into equation (1), Hx′ Hy′ Hz′=1, sinφ, sinθcosλ, 0, cosφ, sinθsinλ, 0 0 cosθHx Hy Hz ……(3) From equation (3), Hx, Hy, Hz are: Hx Hy Hz=h01, sinφ, sinθcosλ, 0, cosφ, sinθsinλ, 0 0 cosθ〓 ^-1 | | 〓Hx′ Hy′ Hz′ ……(4) Here, sinφ=y1, cosφ=y2, sinφcosλ=Z1,
If we write sinθsinλ=Z2 and cosθ=Z3 and rearrange equation (4), we get Hx, Hy, Hz can be found from the outputs Hx', Hy', Hz' of the magnetometers Fx, Fy, Fz, and the magnetic field strength h0 is h0 = √ ² + ² + ² Figure 4 shows the above (5 ) shows a circuit configuration that calculates h0 by calculating the equation.

Hx＝Hx′ Hy＝Hy′−Hx′sinφ／cosφ Hz={Hx′(sinφsinθsinλ−sinφcosλcosφ) −Hy′sinθsinλ＋Hz′cosφ}／cosφcosθ Since the trigonometric function part is a constant, Hx＝Hx′ Hy＝aHx′＋bHy 'Hz=cHx'+dHy'+fHz' where a to f can be obtained by calculation by precisely measuring φ, θ, and λ in advance. In Figure 4, Fx, Fy, Fz are the magnetometers shown in Figure 2, and 2
x, 2y, 2z are amplifiers that amplify the output of Fx, etc., and those written as Xa, Xb, etc. are amplifiers that amplify the output of Fx, etc.
Coefficient multiplication circuits that multiply, b times, and equal, 3y, 3z are addition circuits, 4x, 4y, 4z are square circuits,
5 is an adder circuit, 6 is a square root circuit, and the output of this square root circuit gives the required magnetic field strength h0.

If the amount of variation in the direction of the magnetic field to be measured is small and the approximate direction is known, the magnetometers described above should be placed at narrow angles to each other so as to surround the range of variation in the direction of the magnetic field to be measured, rather than being orthogonal. Crossing them reduces the influence of measurement errors in the mounting angle. In other words, when the angle is close to 90°, the ratio of measurement error to the angular difference from 90° (φ, θ, λ, etc.) becomes large, and the influence of the error is particularly strong in terms that are effective due to sine, so the mutual Measurement accuracy can be improved by setting the mounting angle as far away from the right angle as the measurement purpose allows.

In addition, in the case of a deviation magnetometer that measures only the amount of change in the magnetic field without considering the absolute value of the magnetic field,
This is particularly effective because the influence of measurement errors due to deviations from the right angle between the angles of the magnetometers is reduced.

In the above embodiment, three magnetometers are used, but four or more magnetometers are used, several sets of three magnetometers are created from these, and the above calculation configuration is applied to each set. If the magnetic field is calculated using the average method or the like from the magnetic field strength determined using the method, the measurement accuracy will be further improved.

Conventionally, there have been methods that measure magnetic field strength by arranging three magnetometers perpendicular to each other and detecting the axial component of the magnetic field, but the sensitivity of the magnetometers is limited by the fact that the mounting angle of the magnetometers deviates from the right angle. It wasn't so high that it had to be a problem. The present invention is significant when using highly sensitive magnetometers in which the recognition error of the angle between the magnetometers cannot be ignored when calculating the magnetic field strength from the component in the direction of the magnetometer. Focusing on the fact that it is easier to improve accuracy by measuring the error from a specific angle than by fixing the magnetometer extremely precisely, we calculated the magnetic field from the angular error instead of making an effort to make the mounting angle of the magnetometer highly accurate. Since it is designed to find the following, a highly sensitive and highly accurate magnetometer can be obtained with relatively easy work.

[Brief explanation of the drawing]

Fig. 1 is a diagram explaining the function of the magnetometer, Fig. 2 is a perspective view showing the arrangement of the magnetometer in the present invention, and Fig. 3 is a diagram explaining the function of the magnetometer.
The figure is a perspective view showing the angle formed between the axis of the magnetometer and the orthogonal coordinate axes, and FIG. 4 is a block diagram showing the arithmetic circuit of an apparatus according to an embodiment of the present invention. Fx, Fy, Fz……magnetometer, Xa, Xb, ~XF……
Coefficient multiplier.

Claims (1)

[Claims] 1. Fix three or more magnetometers so that their detection axes are at arbitrary angles to each other so that each magnetometer is arranged three-dimensionally,
Using data obtained by measuring the angle formed between the detection axis of these magnetometers and an appropriately assumed orthogonal coordinate axis, calculate the magnetic field component with respect to the above orthogonal coordinate axis from the magnetic field component in the direction of the detection axis of each magnetometer. magnetometer connected to a circuit.