RU2174235C1 - Gear measuring periodic magnetic fields and securing their distribution in space and time - Google Patents

Abstract

FIELD: information and measurement technology, specifically, magnetometry. SUBSTANCE: technical result of invention lies in measurement of magnetic induction in one point, in securing distribution of magnetic fields in space and time and in visualization of their images with the aid of algorithm of computer tomography. Proposed gear has bus, stepping motors connected to control units, transmitting screw connected to first motor and source of emission of magnetic fields positioned on rotary table. Gear is supplemented with additional bus and two measurement circuits in the form of narrow rectangular frames orthogonally oriented one relative to another and made fast to mechanism of two-coordinate positioning. Electric outputs of circuits are connected to amplifiers which outputs are connected to inputs of two-channel analog-to-digital converter whose both output buses are linked to interface. Transmitting screw is linked to rotating mechanism which carries rotary table, second and third stepping motors connected via horizontal and vertical guides to mechanism of two-coordinate positioning. Units of limit switches which outputs are connected to interface are anchored on all stepping motors. Interface is connected by outputs to computer and to source of emission of magnetic fields via former of synchronization pulse. EFFECT: measurement of magnetic induction in one point, securing of distribution of magnetic fields in space and time and visualization of their images. 4 dwg

Description

 The invention relates to information measuring equipment, in particular to magnetometry, and can be used to measure the characteristics of dynamic magnetic fields, as well as to obtain the distribution of magnetic fields in space and time and to visualize their images using the computational tomography procedure.

 A device for topography of a magnetic field [1], containing a semiconductor wafer with a matrix placed on it, consisting of columns and rows of interconnected elements. Moreover, the measurement of the magnetic field, due to the matrix regular structure, is carried out simultaneously in a large number of points on the plane. However, the known device allows to obtain only one component of the magnetic induction vector, equally directed with the normal to the semiconductor wafer. In addition, the device has limitations on the number of matched point sensors (elements).

 A device for scanning magnetic fields [2], containing a matrix of sensitive elements, including N flux-gates, in which the magnetic field is measured alternately in a large number of plane points, followed by processing the measured voltage using a computer. However, the known device allows to obtain only one (of three) component of the magnetic induction vector. In addition, the device has limitations on the number of flux gates and, as a consequence, on resolution.

 Closest to the claimed is a device for measuring and topography of magnetic fields of scattering near the surface of the object of study [3], containing a measuring and computing unit, a common bus, stepper motors and their control and power units, a magnetic induction measuring transducer, a three-component Hall sensor, micro displacement strain sensors , a block of mechanical movements with gearboxes and transmission screws, a rotary table, three movable carriages, a pulse shaper, a voltage generator. In the specified device, the measurement of the magnetic field is based on sequential movement in accordance with a predetermined path using the measuring rod of one three-component Hall sensor relative to the measurement object by means of a mechanical displacement unit, followed by statistical processing of the measurement results by the measuring and computing unit. However, the known device requires multiple measurements at each point, whereby the procedure becomes time-consuming and lengthy. In addition, the used statistical approach involving averaging does not allow one to obtain distributions characterizing the instantaneous state of an alternating magnetic field.

 The technical result of the invention is the expansion of functionality, which consists in providing measurements of the components of the magnetic induction vector at any individual points, as well as in obtaining distributions of the magnetic field induction both in sections and in the volume of the radiation source space with the ability to visualize images of these distributions. The essence of the claimed invention lies in the fact that the device comprises stepper motors connected to control units, a transmission screw connected to the first stepper motor, and also a source of periodic magnetic fields located on the turntable. The technical result is also achieved by the fact that two measuring circuits are introduced into the device in the form of narrow rectangular frames orthogonally oriented relative to each other, mechanically rigidly connected to the two-coordinate positioning mechanism and connected to it through horizontal and vertical guides, respectively. The second and third stepper motors, stepper motor control units, an electronic computer connected to the outputs of an interface connected via a synchronization pulse generator to a source of periodic magnetic fields, a two-channel analog-to-digital converter, two output data buses of which are connected to the interface, are also introduced into the device . The outputs of the measuring circuits are connected to amplifiers, the outputs of which are connected to the inputs of a two-channel analog-to-digital converter, and the transmitting screw is connected to a rotating mechanism on which the turntable is mounted. Limit switch blocks are fixed on all stepper motors, the outputs of which are connected to the interface, the outputs of the interface are connected to stepper motors via control units, the stepper motor control units, synchronization pulse shaper and electronic computer are designed to provide successive sequential discrete translational movements with a given step of the two-coordinate positioning mechanism and rotations of the turntable relative to the source of periodic magnetic field with a step angle of rotation and measurement after each translational step movement induced in the measuring circuit voltage. In this case, the electronic computer provides measurement of the components of the magnetic induction vector at any individual points and reconstruction of the distribution image of the magnetic induction module in the coordinates of the source of periodic magnetic fields.

 In FIG. 1 shows a block diagram of a device.

 The device contains orthogonally oriented in space rectangular measuring circuits 1 and 2, amplifiers 3 and 4, two-channel analog-to-digital converter (ADC) 5, interface: control units 7, 8, 9 with stepper motors, step motors 10, 11, 12, blocks 13, 14, 15 limit switches, two-axis positioning mechanism, 16, rotary mechanism 17, rotary stage 18, magnetic field radiation source 19, synchronization pulse shaper 20, electronic computer 21, horizontal guide 22, vertical cial guide 23 transmitting the screw 24, the output bus analog-digital converter 25, 26.

 The computer 21 is connected to the interface 6, the outputs of which are connected via control units 7, 8, 9, to the stepper motors 10, 11, 12. The radiation source of the magnetic fields 19 is located on the turntable 18. Two measuring circuits 1 and 2, made in the form of orthogonally oriented with respect to each other, narrow rectangular frames are mechanically rigidly connected with the two-coordinate positioning mechanism 16. In this case, the electrical outputs of circuits 1 and 2 are connected respectively to amplifiers 3 and 4, the outputs of which are connected to the inputs of the two-channel ADC 5. All output data buses 25, 26 of the ADC 5 are connected to the interface 6. The stepper motor 10 is connected through a transmission screw 24 to a rotary mechanism 17 on which the rotary table is fixed 18. The stepper motors 11 and 12 are connected through the horizontal 22 and vertical 23 guides to the mechanism two-coordinate positioning 16. Blocks 13, 14, 15 of limit switches are fixed on all stepper motors, the outputs of which are connected to interface 6, which is also connected via a synchronization pulse shaper 20 to the source I magnetic fields 19.

 The device operates as follows.

 Differential signals from each of the two orthogonally oriented measuring loops 1 and 2 are fed to amplifiers 3 and 4, respectively, where they are amplified to a certain level and normalized. From the outputs of the amplifiers, the signals are fed to the inputs of a two-channel analog-to-digital converter (ADC) 5, two output data buses 25, 26 of which are connected to the inputs of the interface 6 connected to the computer 21.

 By means of a two-coordinate positioning mechanism 16, driven by a stepper motor 11 through a horizontal guide 22 and a stepper motor 12 through a vertical guide 23, mechanically connected orthogonally-oriented measuring circuits 1 and 2 are moved horizontally and vertically, respectively. In addition, the stepper motor 10 through the transmission screw 24 and the rotating mechanism 17 performs rotations (with a given angular pitch) of the rotary table 18, on which is located the radiation source of the studied magnetic fields 19.

 The limit switches of block 14, mounted on the stepper motor 11 (or located on the edges of the horizontal rail 22), and the limit switches of block 15, mounted on the stepper motor 12 (or located on the edges of the vertical rail 23), limit the horizontal movement of the two-coordinate positioning mechanism 16 and vertically, respectively. The limit switches of the block 13 limit the rotation of the rotary table 18. All the outputs of the limit switches of the blocks 13, 14, 15 are connected to the corresponding inputs of the interface 6.

 To find the total distribution of the vector function of magnetic induction in the volume of the radiation space of the object, the following approach is used. The volume under investigation is represented by a set of parallel sections (Fig. 2). This condition allows us to reduce the dimension of the problem, which then reduces to obtaining the distribution of magnetic induction in the plane of the section.

 Distributions in the flow plane are obtained by applying the theory of computational tomography [4] to the voltages induced according to the Faraday law in two orthogonally oriented narrow rectangular contours of width h moving along a section in a magnetic field with a certain sequence (Fig. 3). As a result, the spatial distribution for each of the three components of the vector function is represented as a square matrix of "n" rows and "n" columns (Fig. 2). Each element of the matrix is the value of the component of the magnetic induction vector averaged within the elementary area. It should be noted that although the whole sequence of measurements determined by computed tomography is not instantaneous, since mechanical displacements take place between the measurements, the procedure used allows one to obtain distributions characterizing the instantaneous state of the field. This is due to the periodicity property of the magnetic field, which exactly repeats its values at the same time intervals equal to the period. Thus, if appropriate measurements are taken at time intervals that are multiples of the period, then in this case the distributions of the magnetic induction vector function will be the same and characterize a single instantaneous state of the field.

где j = 1, 2,...M; a_ij - весовые коэффициенты, отражающие вклад индукции B_i, i-й элементарной площадки в j-й магнитный поток Φ_j, пронизывающий контур; N - число элементов в матрице распределения; M - общее число отсчетов (уравнений).Unlike the existing ones, the proposed device makes it possible to avoid measurements at each point and at the same time allows to obtain the distribution of the components of the vector function of the magnetic induction determined at any point of the scanned section and at any time during the period. This is possible by measuring a number of integral values - magnetic fluxes induced in narrow contours for many intersecting at different angles of the trajectories. For each j-th measurement, the magnetic flux penetrating the contour is the sum of the fluxes of elementary sites located along the contour with the corresponding values of the induction B _i . Therefore, for the j-th magnetic flux, the indicated sum can be written in the form of the equation:

where j = 1, 2, ... M; a _ij are weights reflecting the contribution of induction B _i , of the i-th elementary site to the j-th magnetic flux Φ _j penetrating the contour; N is the number of elements in the distribution matrix; M is the total number of samples (equations).

где i = 1, 2,...N; (a_ij)^-1 - матрица, обратная матрице a_ij.Expression (1) is a system of M linear equations with N = n • n unknowns. If the experimental results (separate equations) are linearly independent and the number of equations M is equal to the number of unknowns N, then the system has a unique solution that can be obtained by inverting the matrix of weight coefficients a _ij :

where i = 1, 2, ... N; (a _ij ) ^-1 is the matrix inverse to the matrix a _ij .

 The equations will be linearly independent if the measurement procedure is implemented in the following way. These circuits alternately make sequential discrete translational displacements with a given step, thereby covering the entire investigated section plane, and rotations relative to the measurement object in the interval from 0 to π with a step of the angle of rotation ΔΦ = π / n. During such a scan, after each translational step movement, the induced voltages are measured. Thus obtained for each frame of "n" samples make up one linear "projection of stresses corresponding to a certain angle of rotation Φ (Fig. 3). And" n "of such linear projections, obtained sequentially and differing in angle Φ, make it possible to compose a system of equations for each component whose solution is the distribution in the section plane.

(13)
где Φ $\genfrac{}{}{0ex}{}{\text{r}}{\text{j}}$ - отсчет магнитного потока, индуцируемого в контуре с нормалью в направлении оси r; Φ $\genfrac{}{}{0ex}{}{\text{l}}{\text{j}}$ - отсчет магнитного потока, индуцируемого в контуре с нормалью в направлении оси l, a Φ $\genfrac{}{}{0ex}{}{\text{z}}{\text{j}}$ - отсчет магнитного потока, индуцируемого в контуре с нормалью в направлении оси z.The relationship between the components of the magnetic flux in the coordinate systems of the scanning frames r, l, z and the measurement object x, y, z is determined by the following expressions:

(thirteen)
where Φ $\genfrac{}{}{0ex}{}{\text{r}}{\text{j}}$ - reference magnetic flux induced in the circuit with a normal in the direction of the r axis; Φ $\genfrac{}{}{0ex}{}{\text{l}}{\text{j}}$ is the countdown of the magnetic flux induced in the circuit with a normal in the direction of the l axis, a Φ $\genfrac{}{}{0ex}{}{\text{z}}{\text{j}}$ - reference magnetic flux induced in the circuit with a normal in the direction of the z axis.

осуществляется посредством измерительного контура 1, перпендикулярного плоскости сканирования. Причем необходимо учитывать, что в системе уравнений (3) отсчету Φ $\genfrac{}{}{0ex}{}{\text{r}}{\text{j}}$ , измеренному под углом Φ, соответствует отсчет Φ $\genfrac{}{}{0ex}{}{\text{l}}{\text{j}}$ , измеренный под углом ^{Φ + π/2.} Измерение магнитного потока

осуществляется посредством измерительного контура 2, параллельного плоскости сканирования.Magnetic flux measurement Φ $\genfrac{}{}{0ex}{}{\text{r}}{\text{j}}$ and

carried out by means of a measuring circuit 1, perpendicular to the scanning plane. Moreover, it should be taken into account that in the system of equations (3), the reference Φ $\genfrac{}{}{0ex}{}{\text{r}}{\text{j}}$ measured at an angle Φ corresponds to a reference Φ $\genfrac{}{}{0ex}{}{\text{l}}{\text{j}}$ measured at an angle ^{Φ + π / 2.} Magnetic flux measurement

carried out by means of a measuring circuit 2 parallel to the scanning plane.

обеспечивается посредством измерения напряжений U_j ^r(t) и U_j ^l(t), наводимых в контуре 1, перпендикулярном плоскости сканирования (фиг. 3). Распределение z-компоненты получается посредством измерения напряжений U_j ^z(t) с помощью контура 2, параллельного плоскости сканирования. Затем для определения компонент распределения векторной функции магнитной индукции необходимо решить систему уравнений:

где B_i ^z(t_k), B_i ^y(t_k) и B_i ^z(t_k) - x-, y- и z- компоненты векторной функции магнитной индукции

соответственно; T - период изменения магнитной индукции; m = 1,2,... - номер периода; t_k - текущий k-й отсчет в периоде;

K- число отсчетов на период.The voltage induced in the circuits will be determined by a change in the magnetic flux penetrating the circuit: U = - d Φ / dt. Thus, obtaining the distributions of the x- and y-components of the vector function

is provided by measuring the voltages U _j ^r (t) and U _j ^l (t) induced in circuit 1, perpendicular to the scanning plane (Fig. 3). The distribution of the z component is obtained by measuring the voltages U _j ^z (t) using circuit 2 parallel to the scanning plane. Then, to determine the components of the distribution of the vector function of magnetic induction, it is necessary to solve the system of equations:

where B _i ^z (t _k ), B _i ^y (t _k ) and B _i ^z (t _k ) are the x-, y- and z-components of the vector function of magnetic induction

respectively; T is the period of variation of magnetic induction; m = 1,2, ... - period number; t _k is the current k-th sample in the period;

K is the number of samples per period.

L - число возможных сечений по вертикали. Если определяется распределение магнитной индукции в объеме, то устанавливается начальный уровень z=z_l.Before starting measurements of the computer 21 through the control unit 9 of the stepper motor 12 using the two-coordinate positioning mechanism 16 sets the circuits 1 and 2 to the vertical level z = z _l corresponding to a given l-th section, where

L is the number of possible vertical sections. If the distribution of magnetic induction in the volume is determined, then the initial level z = z _{l is established} .

 After that, in the plane of the established section at different angles Φ, the procedure of scanning the magnetic field is carried out. The entire scanning procedure consists of "n" cycles, where the number of cycles "n" is determined by the number of angles Φ at which to scan.

One scan cycle consists in sequentially moving with a step Δr the two-coordinate positioning mechanism 16 along the horizontal guide 22 from one extreme position to another (from left to right or, conversely, from right to left). During such a scan, after each step, the projection data U _j ^r (t), U _j ^l (t) and U _j ^z (t) necessary for the computational tomography procedure are obtained (Fig. 3). In addition, each scan step is assigned an end-to-end serial number j (where j = 1 ... N, and N = n • n is the number of steps in one scan cycle).

начинается с того, что механизм двухкоординатного позиционирования 16 отводится в крайнее положение, о чем свидетельствует сигнал с концевого выключателя блока 14. Кроме того, вращающим механизмом 17, приводимым в движение шаговым двигателем 10 через передающий винт 24, поворотный столик 18 устанавливается в положение, соответствующее углу поворота Φ_q = (q-1)π/n, о чем также свидетельствует сигнал с концевого выключателя блока 13. Сигналы от концевых выключателей блоков 14 и 13 указывают на то, что система готова к получению проекционных данных в пространстве и во времени. Получение проекционных данных заключается в измерении напряжений, индуцируемых в контурах 1 и 2 согласно закону Фарадея.Each qth scan cycle (where q =

begins with the fact that the two-coordinate positioning mechanism 16 is pushed to the extreme position, as evidenced by the signal from the limit switch of the unit 14. In addition, the rotary mechanism 17, driven by the stepper motor 10 through the transmission screw 24, the rotary table 18 is set to the position corresponding the angle of rotation Φ _q = _(q-1) π / n, as also evidenced by the signal from the switch terminal unit 13. the signals from the limit switches blocks 14 and 13 indicate that the system is ready to receive the projection data in the pro transtve and time. Obtaining projection data consists in measuring the voltages induced in circuits 1 and 2 according to the Faraday law.

 The procedure for obtaining projection data in time for each j-th position of the two-coordinate positioning mechanism 16 in space relative to the radiation source of magnetic fields 19 is that the device expects a synchronization signal from the output of the synchronization pulse shaper 20. In this case, the signal supplied to the synchronization pulse shaper 20 from a radiation source 19, can be obtained both galvanically, i.e. from a device that feeds the emitter, and through a magnetic field sensor (not yet Done). As soon as the synchronization signal appears at the input of the interface 6, the computer 21 generates a control signal to start the procedure for measuring voltages characterizing different points in time over a period. During one period T, at equal time intervals Δt, K measurements are made. Each dimension is assigned a serial number k (where k = 0 ... K-1). During each k-th measurement, both channels of the two-channel ADC 5 are interrogated and the measurement results over the data buses 25 and 26 of the ADC 5 are transmitted via the interface 6 to the computer 21, where for each circuit at the jth step, the data obtained are presented in the form of a column vector with the size l x K. The time interval Δt equal to T / K between the k-th and (k + 1) -th measurements characterizes the time resolution and is determined by the upper informative frequency of the magnetic field change. After the last K-th measurement is completed, the computer 21 through the control unit 8 and the stepper motor 11 moves the two-coordinate positioning mechanism 16 by a distance Δr, which characterizes the spatial resolution and is determined by the resolution of the system. Then, for the (j + 1) -th step, the synchronization signal is again expected and with its appearance, the following K voltage measurements are performed, induced in circuits 1 and 2.

в сечении z=z_l (в координатах объекта излучения x, y, z, масштабы указаны на осях).Therefore, during each scan cycle, the two-coordinate positioning mechanism 16 with a step Δr goes all the way along the horizontal guide 22 from one end switch of the block 14 to the other. The results of one such scanning cycle are reduced to an array of size n • K, and “n” cycles with different angles Φ make it possible to obtain all the information necessary for reconstruction of the image about the radiation source of the magnetic field 19 in the section plane z = z _l . The reconstruction of the image of the distribution of the vector function of magnetic induction in the section plane z = z _l can be carried out in accordance with the system of equations (4) using, for example, the computing environment "Mathcad 5.0 PLUS". As an example in FIG. 4 shows a combined image of a cylindrical coil creating a magnetic field, as well as experimentally obtained and reconstructed distribution of the magnetic induction module

in the section z = z _l (in the coordinates of the radiation object x, y, z, the scales are indicated on the axes).

 As a result of the repetition of the described procedure over all sections, i.e. L times, a data array of size LxNxK is obtained, which allows one to obtain the distribution of the vector function of the magnetic field induction of the radiation object over the period and in the entire volume of the measurement setup.

 Thus, the proposed device allows you to measure the components of the magnetic induction vector at any individual points in space and time, as well as to obtain the distribution of the magnetic field induction both in sections and in the volume of the radiation source space with the ability to visualize images of these distributions on a computer screen.

Literature
1. USSR author's certificate N 1652951, cl. G 01 R 33/02, 1991

 2. USSR author's certificate N 1762282, cl. G 01 R 33/02, 1992

 3. Copyright certificate of the USSR N 1684761, cl. G 01 R 33/06, 1991

 4. X-ray engineering. Reference book in 2 books. Prince 2 / Ed. V.V. Klyueva. M .: Engineering. from. 319-326.

Claims (1)

 A device for measuring periodic magnetic fields and obtaining their distributions in space and time, containing stepper motors connected to control units, a transmission screw connected to the first stepper motor, and also a source of periodic magnetic fields located on the turntable, characterized in that two measuring contours were introduced in the form of narrow rectangular frames orthogonally oriented relative to each other, mechanically rigidly connected with the mechanism of two-coordinate positions ionization and connected to it respectively through horizontal and vertical guides, second and third stepper motors, stepper motor control units, an electronic computer connected to the outputs of the interface connected via a synchronization pulse generator to a source of periodic magnetic fields, a two-channel analog-to-digital converter, two output data buses of which are connected to the interface, the outputs of the measuring circuits are connected to amplifiers, the outputs of which are connected to the input two-channel analog-to-digital converter, moreover, the transmitting screw is connected to the rotary mechanism on which the rotary table is mounted, limit switch blocks are fixed on all stepper motors, the outputs of which are connected to the interface, the outputs of the interface are connected to stepper motors through the control units, and stepper motor control units , the synchronization pulse shaper and the electronic computer are designed to provide sequentially sequential discrete translational movements with a given step of the two-coordinate positioning mechanism and rotations of the turntable relative to the source of periodic magnetic fields with a step of the angle of rotation and measurement after each translational step movement of the voltage induced in the measuring circuits, and the electronic computer provides measurement of the components of the magnetic induction vector at any individual points and reconstruction images of the distribution of the magnetic induction module in the coordinates of the source of periodic magnetic fields.

Images