SU1404989A1 - Senor of magnetic field of closely situated sources - Google Patents

Abstract

The invention relates to magnetic measurements. The magnetic field sensor of closely located sources consists of three coaxial induction coils (IR), the frames of which are made of a nonmagnetic material. IR 1 has an inner radius of g, outer g, is wound with a wire of diameter d, with a winding density coefficient and, IR 2 has an inner radius of g, outer g, wire diameter dj and a winding density coefficient of w.IR 3 has an inner radius of g, outer g wire diameter d, and the coefficient of winding density | b | . IR 1-3 are related by the relation (r3 - r |) (1 + / 3, -d2, // 3, .d |) r | - r, (r | - rj) (1 + / 3, -d2 //, dp r | - rf. The sensor has increased noise immunity from the fields of distant interference sources, 2 Il. W (L

Description

NU

:about

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The invention relates to magnetic measurements and can be used to measure the components of the MarHiiTHHX field strengths of closely located sources when exposed to strong fields of distant sources.

The purpose of the invention is to increase the interference immunity from the fields of distant interference sources with a slight increase in weight and size characteristics.

Figs, 1 and 2 show the magnet field sensor circuit,

The sensor consists of three coaxial coils, the frames of which are made of non-magnetic material, such as plastic. The coil 1 has an inner radius r and an outer radius r and is wound with a wire of diameter dj 5, with a winding density factor PJ.

Coil 2 is a signal coil, it has an internal rgadius g and an external radius g and is wound with a wire of diameter d 2 with a winding density coefficient j},

The coil 3 has an inner radius Tj and an outer radius r, wound with a wire with a diameter d, with a density coefficient p-nyuki.

Coil 1 is connected in opposite with coil 2 and in series with coil 3, t, e. The output of the first coil, on which a positive potential is induced, is connected to the pin of coil 2, on which the negative potential is induced and is one of the output. The negative side of the first coil is connected to the positive top of the third, and the positive lead of the second coil is connected to the negative side of the third coil and is the second output.

The sensor works as follows;

The total alternating magnetic field from nearby and distant sources induces EMF in the windings of the induction coils. The induced EMFs of the first and third coils are added up, since the windings of the coils are included in the sequences and this amount is subtracted from the EMF of the second (signal) Kai-ymKHj because the second coil is embedded in the first and third. For remote sources (x + 2) g, where X and Z are the coordinates of the source, and under the condition x O you can get

Ф - Црш, r, s-M2s + 1) 1) (2z 5

(-23) s

;

(one)

de F - magnetic flux;

S - 0,1,2,. ,, ,,

Differential signal at the output of the sensor (EMF)

 iOjUom (-) (2s + 1) l,,

9 3f-- 93cl72S 1 h

2z3

-N ,, rr,

 2. -g

tib

where r

-

CO

PO

- distance to the source;

 radius of the second (signal) coil

N ,, Nj, Nj - the number of turns of the first, second and third coils;

 the radius of the third coil, and g, i g g,

i- output CURRENT;

-frequency, -magnetic constant j

base gradientometer. To compensate for the signal from a remote source, it is necessary to get the first terms of the row (1) equal to zero,

In the above formulas it is considered that the windings are wound with an infinitely thin wire. In the case of bulk coils (there is a wire diameter and there may be several windings) and to ensure the equality to zero: the first two terms of the sum (1) must fulfill the following conditions:

R j2

fv.3 r S lM +) g - g g / | 3, d2, 4 п

(d - d) (1 + b r - t VTj .i f a,.

In this case, the suppression of a signal from a remote source at the sensor output is obtained as in fourth-order gradiometers, which significantly increases the noise immunity of the sensor, the emf from a remote source at the sensor output is proportional to:

 . one .

z z

It is advisable to use the sensor when measuring weak magnetic fields of closely located sources — in the presence of strong magnetic fields from distorted interference sources, i.e. in those cases in which it was necessary to use room shielding

Claims (1)

Invention Formula Magnetic field sensor - nearby sources, containing the first and second induction coils of equal height, connected oppositely and located coaxially with a common center of symmetry, characterized in that, in order to increase the noise immunity, the third induction coil of the same height, located coaxially to the first two, and the coil radii are related by -v sh --1 gr (1 /, dV   g / 3 .d | - where r rg -JQg 15 20  PI g inner radius of the first coil; the outer radius of the first and the inner radius of the second coil; outer radius of the second and inner radius of the third coil outer radius of the third coil wire diameter of the first and third coil and the coefficient of winding density, respectively; wire diameter and winding density coefficient of the second coil.  / 2 / J