SU1215023A1 - Apparatus for screening magnetic fields - Google Patents

Abstract

The invention relates to a measuring process and can be used, for example, for 3aiiQiTH measures of magnetic induction from the effects of the external magnetic field of the Earth. The purpose of the invention is to increase the stability of the magnetic field. Conductive shells 4, 6, and 8 are located inside, and conductive shells 5, 7, and 9, cut along the generatrix, are located outside the corresponding ferromagnetic shells 1,2 and 3. All the shells are located coaxially. Conductive busbars 13 of shells 4, 6 and 8 are placed at their ends with electric contact along the entire perimeter. Conductive tires 14 of shells 5, 7 and 9 are located on opposite edges of the cut with electrical contact along the entire length of these shells. Conductive tires 13 and 14 are connected to a source of demagnetizing floor. In the description, a formula is given to determine the optimal distance between the ends of each inner ferromagnetic shell and the adjacent outer shell. 1 h, para. f-ly, 2 ill. t 2 th SP n9 OO

Description

The invention relates to a measurement technique and can be used to protect magnetic induction measures against the effects of an external magnetic field of the Earth, its variations and industrial magnetic interference, as well as to create a working volume with a small magnetic field induction required for tuning, testing and evaluating basic metrological magnetometer equipment parameters (sensitivity threshold, zero offset, noise level, etc.).

The purpose of the invention is to increase the stability of the magnetic field due to the fact that the device for shielding the magnetic fields, containing the ferromagnetic shield, consisting of co-located ferromagnetic shells and an demagnetizing current source with an air gap, is provided with non-magnetic 2h conductive shells In this case, all the conductive envelopes with respect to the corresponding ferromagnetic shells are made in the form of cylinders, the current-conducting busbars of which are located at their ends, and the outer ones with respect to

to the corresponding ferromagnetic magnetising current.

The conductor sheaths are made in the form of cylinders cut along the generatrices, their conductive busbars are located on opposite edges of the slot, the source of demagnetizing current is connected to the conductor busbars

wife coaxially with ferromagnets. In addition, the goal is achieved by the fact that each inner ferromagnetic shell is shorter than the adjacent outer ferromagnetic shell by an amount chosen from the ratio b / D 5 0.22 (1+) dB L is the difference

between the lengths of the outer and inner ferromagnetic shells, J) is the diameter of the outer shell, d is the wall thickness of the outer shell, N is the demagnetization factor of the outer shell, K is a constant coefficient equal to two for shells with open ends and equal to one for shells with bottom .

FIG. 1 schematically shows the proposed device; FIG. 2 is a view A of FIG. one.,

The device consists of a ferromagnetic screen containing three ferro

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Magnetic shells 1-3, made, for example, of permallo 81NMA, six conductive shells 4-9 of a highly conductive nonmagnetic material, for example, copper, and a demagnetizing current source 10 consisting of a voltage generator 11 and an autotransformer 12. From Six wires of three shells (4.6 and 8) are placed inside, and the other three conductive shells 5, 7 and 9, cut along the generator, are located outside the corresponding ferromagnetic shells 1, 2 and 3. All

15, ferromagnetic shells 1–3 and conductive shells 4–9 are aligned. Conductive busbars 13 of the inner shells 4,6 and 8, made, for example, of a thick copper strip, are located at the ends of the shells with electrical contact around the perimeter of the end face, and the current-conducting busbars 14 of the outer wires of the shells of 5.7 and 9 are located on opposite edges of the slit with electrical contact along the entire length of these shells. The specified busbars 13 and 14 are connected to the source 10 times by wires 20

five

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 The device for shielding magnetic fields works as follows.

The ferromagnetic screen is influenced by the Earth’s magnetic fields, industrial installations and electrified transport. Due to the choice of a certain number of ferromagnetic 1-3 and conductive 4-9 shells, high magnetic permeability of ferromagnetic shells 1-3, high conductivity and non-magnetization of conductive shells 4-9, a certain ratio between length L and diameter D (U / D ) ferromagnetic 1-3 and conductive 4–9 shells and the thickness of their walls external constant and variable magnetic fields are weakened in three orthogonal directions X, Y, Z by ferromagnetic 1-3 and conductive 4–9 shells, so that the central area of the magnetic induction screen l is determined by the residual magnetic field associated with the ferromagnetic-H1L4I shells 1-3.

In the central region of the screened volume of the screen is placed,

For example, a ferrosoid transducer and measure the magnetometer zero level over time. The value of the induction of the residual floor of the screen largely depends on the history of the material of ferromagnetic shells 1-3, moreover, over time, under the influence of extra magnetic fields and magnetic fields of primary converters placed in the screen, magnetization of the ferromagnetic layers 1-3 occurs, due to which the residual magnetic field of the screen increases. These ferromagnetic shells, starting with an ankle 3 and ending with an inner 1, are demagnetized by passing an alternating current with an amplitude decreasing for, for example, 200-300 seconds from maximum value to zero, according to the conducting shells, respectively 9 and 8, 7 and 6, 5 and 4 from the source 10 of demagnetizing current through the conductive busbars 13 and 14 located at the ends of the shells 4, 6 and 8 and opposite edges of the slot. shells 5.7 and 9, which ensures a uniform distribution of the demagnetizing current along the conductors shells 4–9. - Thanks to the high electrical conductivity and low inductance of the conductive shells 4-9, therefore, the small active and inductive reactance of these shells, the amplitudes of the variable demagnetizing currents reach a large value, which occurs at low voltages at the output of the autotransformer 12. As a result The amplitudes of Induction of demagnetizing alternating fields easily reach values exceeding their induction values for the technical saturation of the material of ferromagnetic shells 1-3, and each Yes, the ferromagnetic shell is demagnetized in both longitudinal and transverse directions. As a result, the value of the residual magnetic field in the pre-set device is reduced by 215023.4

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Claims (2)

1. A device for shielding magnetic fields, including a ferromagnetic shield containing h coaxial ferromagnetic shells, and a source of demagnetizing current, due to the fact that, in order to increase the stability of the magnetic field, 2h cylindrical conducting shells are introduced into it with conductive women located coaxially with ferromagnetic shells, and inside and outside each ferromagnetic shell are placed inside and the outer cylindrical conductive shells, while the conductive tires are located at the ends of the inner cylindrical conductive shells, and at the outer pindric conductive shells cuts are made along the generator and the conductive buses are located along both sides; 2. The device in accordance with claim 1, 1, which is such that the optimal distance between the ends of the cable of the inner ferromagnetic shell and the adjacent outer shell is chosen from the ratio 35 b..2i-k H (I) where D is the diameter of the outer ferric filament sheath; d is the wall thickness of the outer ferromagnetic shell; N is the demagnetization coefficient of the outer ferromagnetic shell; K is a constant coefficient equal to two for shells with open ends and equal to one for shells with a bottom; / - relative magnetic permeability. I "" 37 one one  ... 1 Ti .. w. L V ,. L. / l j /, - X y f f f f x y f f f f f r tt f f f f 3 r f f f f ri r f cif f f rifi r r r) U       X. S.-4. L%. TiTi 1 n rl t 111      l v -. , - -v - -. .. . . v. . -. -v .y -v  j | 7. ijf Y Y | / D 71T7TG 7TR 7 G TTTTTTUUV1U | T gT | 1iT " -r-f-f-7-g f f V I r r f f  (BvIbmAvvbsh & Ajmi P U /one / f f f f I r f f f f f f f f f ue.1 VNIILI Circulation 778 Order 902/52, Subscription Fi82 Branch ram Patent, Uzhgorod, Proektna St., 4