SU1659942A1 - Method and apparatus for detecting non-uniformity of magnetic field - Google Patents

Abstract

The invention relates to a detection technique, intended for use when searching for cable lines with current, lost pipelines, drills in geological wells, to search for magnetized objects in the human body, to detect hidden weapons at checkpoints. The purpose of the invention is to improve accuracy. When measuring, four points are chosen that are located on the same axis so that the extreme and middle points are located symmetrically relative to the center point on the axis. The magnetic induction vectors are measured at points. The compensation vectors of magnetic induction are reproduced at the extreme points. Judgment of the inhomogeneity of the magnetic field on the measured differences of the projection of the vector of the magnetic field on the axis between the extreme points. The device for implementing the method contains four magnetically sensitive converters, two subtraction units, an addition unit, a variable-voltage generator, two gradient windings, two additional windings, a rigid non-magnetic base, and a recording instrument. To improve the accuracy of detecting the inhomogeneity of the magnetic field against the background of a uniform magnetic field and a non-uniform magnetic field, the interference created by the most distant sources is ensured by using additional and gradient windings reproducing the magnetic induction compensation vectors at the measurement points. 2 sec. f-ly, 1 ill. Yo

Description

The invention relates to a detection technique and is intended for use in searching for cable lines with current, lost pipelines, drills in geological wells, for searching for magnetized objects in the human body, for detecting hidden weapons at checkpoints.

The purpose of the invention is to improve accuracy.

The drawing shows a block diagram of the device for implementing the method.

The device for implementing the method contains four magnetically sensitive converters 1-4 with coaxial

magnetic axes, four transducer amplifiers 5-8, two blocks 9, 10 subtraction, block 11 adding, variable voltage generator 12, two gradient windings 13 and 14, two additional windings 15 and 16, rigid non-magnetic base 17, recording device 18 .

The method is implemented in the following way.

Four measurement points A, C, D, E are selected that are located on the same axis so that the extreme points A, E and mid-points C, D are located symmetrically relative to the center point on the axis. Magnetic induction vectors BA, Bc, Bo, BE are measured, respectively, at points A, C, D, E.

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At the extreme points A and E, the compensation vectors of the magnetic induction VAK and VEK are determined by formulas;

VAK - K (Su + Su) - (Su + BD); Vek | k (Sun + Bo) - | (Sun + B0);

where IAE, ICD are the distances between points A and E, CuO.

The inhomogeneity of the magnetic field is judged by the measured differences of the projections of the magnetic field on the axis between the extreme points A and E.

A device for implementing the method works as follows.

The first inputs of the magnetosensitive transducers 1–4 are fed from a generator 12 of a variable EMF exciter. At the output of each magneto-sensitive transducer, a second harmonic emf appears, proportional to the value of the component of the magnetic induction vector acting on the corresponding transducer. The output signals of the converters 1-4 are amplified and detected in the corresponding amplifiers x-converters 5-8, and then fed to the first inputs of the magnetically sensitive converters 1-4, providing negative feedback on the measured components of the magnetic induction vectors. The output signals of the converter amplifiers b and 7 are fed to the inputs of the subtracting unit 9 and the adding unit 11. From the output of block 9, a signal proportional to the measured spatial derivative of the magnetic induction, created by the most distant sources of the interference field and the magnetic field of the nearby source of the useful signal, goes to the gradient windings 13 and 14, fully compensating the inhomogeneity of the magnetic field from the most distant and partially compensation - from a nearby source of magnetic field. The output signal of the addition unit 11, proportional to the uniform magnetic field, is fed to the additional windings 15 and 16, compensating the field in the magnetically sensitive transducers 1 and 4. Thereby, the components of the external uniform magnetic field in these transducers are compensated.

The output signals of the amplifier-converters 5 and 8, proportional to the components of the magnetic induction vectors,

created by a nearby magnetic field source, is fed to the subtraction unit 10, the output signal of which, proportional to the heterogeneity of the magnetic field of the nearby source field, is fed to the recording device 18.

Claims (2)

Claims of the invention - (. Method of detecting heterogeneity The magnetic field at which four measurement points A, C, D, E are selected, located on the same axis, measures the difference in the projections of the magnetic field vector on the measurement axis at the indicated points, judging according to the measured projection differences about the presence of a non-uniform magnetic field, characterized in that, in order to improve the accuracy, the location of four measurement points is chosen so that the end points A, E and midpoints C, D are located symmetrically relative to the center point on the axis, and the magnetic induction vectors Wd, Be, BD are measured. BE, respectively, at points A, C, D, E, reproduce in the extreme points A and E are the compensation vectors of magnetic induction HAC and CENTURY, determined by the formulas: BAK (BC-BD) - (BC + BD); VEK | k () - {(Sun + Bo); Icd where IAE, ICD are the distances between points A and E, C and D, respectively, and the magnetic field inhomogeneities are judged by the measured differences of the projections of the magnetic field vector. 2. A device for detecting inhomogeneity of a magnetic field containing first, second, third and fourth magnetosensitive transducers placed on a rigid non-magnetic base successively along one axes, first, second, third, fourth transducer amplifiers, a variable emf generator, a registering device, with the outputs of magnetically sensitive transducers connected to the first the inputs of the respective amplifiers-converters, the output of the variable-emf generator is connected to the second inputs of the amplifiers-converters and to the second inputs of magnetically sensitive converters, characterized in that it contains the first and second gradient windings, the first and second additional windings, the first and second subtractors, the adder block In this case, the first gradient and the first additional windings are located on the first magnetosensitive transducer, and the second gradient and the second additional windings ki-fourth magnetosensitive converter, the second outputs of amplifiers converters are connected to first inputs magnitochuvst- pheno- transducers, the first outputs of the first and fourth amplifiers converters - a second subtracting unit outputs, whose output is connected to the input 0 registering device, the first output of the second amplifier converter is connected to the first inputs of the first addition unit and the subtraction unit, the outputs of which are connected to counter-connected gradient windings, the first output of the third amplifier converter is connected to the second inputs of the first subtraction unit and the addition unit, the outputs of which are connected to series-connected additional windings.