RU2533347C1 - Device for independent recording of pulse magnetic field - Google Patents

Abstract

FIELD: measurement equipment.

SUBSTANCE: device includes the primary induction transducer, a resistor, a piece of a thin wire, a magnetoresistive bridge and electrical connectors. The transducer includes a magnetic field concentrator and a coil wound on the concentrator. The bridge made as per a thin-film integral technology includes magnetoresistors made from a ferromagnetic alloy having a rectangular hysteresis loop. The coil is connected through the resistor to the piece of the thin wire laid onto the surface of two of four magnetoresistors forming opposite arms of a magnetoresistive bridge. The device is connected through connectors to an information reading unit.

EFFECT: increasing sensitivity of a magnetoresistive device to a measured magnetic field; excluding influence of electrical noises on a measurement result.

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Description

The present invention relates to measuring technique, namely to devices for autonomous registration of the amplitude of the intensity of a single pulsed magnetic field.

A device [1] is known for measuring the induction of strong magnetic fields in the range of 1-10 T, containing magnetoresistance transducers having a linear calibration characteristic in this range, in which magnetoresistance is placed in one of the arms of a resistive bridge circuit powered from a constant voltage source. The unbalance voltage of the bridge, resulting from a change in the magnitude of the magnetoresistance under the influence of a magnetic field, is measured directly during the period of action of the magnetic field using a pointer or digital device. In order to increase the sensitivity of the device for powering the bridge circuit, an AC voltage source can be used, which allows the use of a selective amplifier with the most preferred characteristics.

However, the sensitivity of this device is insufficient to measure the magnitude of the magnetic fields in the range of less than 1 T.

There is also known a method and device [2] for measuring the magnitude of a magnetic field, containing two magnetoresistive sensors, which are fed with periodic bipolar voltage of the same amplitude, and simultaneously create a magnetization field of the sensors, while receiving in the measured magnetic field an alternation of positive and negative increments of the magnetoresistance of the sensors, the magnitude of which determines the magnitude of the magnetic field. Compared with the device [1], the output signal of the device is doubled, which increases the sensitivity with this conversion method.

However, the measuring range of the device in the limit refers to the range of 0.1-10 T and does not allow measurements of magnetic fields in the range of less than 0.1 T.

The closest in its technical essence (prototype) is a device [3], which generally contains a magnetoresistive bridge made using thin-film integrated technology, an electrical connector, a wired communication line, a power supply and balancer for the magnetoresistive bridge, a reading unit for measuring information.

Before measurement, the magnetoresistive bridge is connected to the power and balancing unit and the reading unit for measuring information using an electrical connector and a communication line, and the bridge is powered and balanced. Then, the magnetoresistive bridge is placed in a measuring magnetic field and, using the measuring information reading unit, measurements are made of the unbalance of the bridge caused by the action of a measured magnetic field on it. The measurement process runs continuously in real time.

Thin-film magnetoresistors of the prototype are larger than "monolithic" ones, suitable for measuring weak magnetic fields of less than 0.1 T. Their sensitivity threshold, characterized by many parameters (residual voltage, level of intrinsic noise, magnitude of the control current, ambient temperature, etc. ) is close to the limit for the magnetoresistive material used. In addition, their temperature stability and converting ability in the range of millitesla units is 5-10 times higher than that of "monolithic" [4].

The prototype, with satisfactory linearity, has the sensitivity necessary to measure the magnetic field in the range of 0.8-40 mT.

The disadvantages of the prototype is the lack of sensitivity of the magnetoresistive device, as well as the impact on the measurement result of electrical interference. The prototype does not allow the measurement of pulsed magnetic fields in the range of 0.01-0.8 mT, which is typical for testing technical equipment for electromagnetic resistance, for example, resistance to lightning. In addition, in the conditions of conducting electromagnetic resistance tests, the presence of a wired communication line in the measurement process as a part of the prototype leads to the induction of electrical noise in it, which impedes reliable measurements and distorts their result.

The technical result of the invention is to increase the sensitivity of the magnetoresistive device to the measured magnetic field, eliminating the influence of electrical interference on the measurement result.

The technical result is achieved in that the device for the autonomous registration of a pulsed magnetic field containing a magnetoresistive bridge made by thin-film integrated technology, an electrical connector, contains an induction primary converter with a magnetic field concentrator and a coil wound on a magnetic field concentrator and connected in series with a resistor and a thin segment a wire laid on the surface of two of the four magnetoresistors forming the opposite shoulders of the magnet resistive bridge, wherein the thin film magnetoresistors made of a ferromagnetic alloy having a rectangular hysteresis loop.

The structural diagram of the proposed device autonomous registration of a pulsed magnetic field is presented in figure 1.

In figure 1, the following notation:

1 - induction primary converter with a magnetic field concentrator and with a coil wound on a magnetic field concentrator;

2 - load resistor;

3 - a piece of thin wire;

4 - magnetoresistive bridge with thin-film magnetoresistors 5, 6, 7, 8 of a ferromagnetic alloy with a rectangular hysteresis loop;

9 - electrical connector magnetoresistive bridge 4;

10 - wire line;

11 - electrical connector wireline 10;

12 - unit for reading measurement information;

13 - block magnetization.

The device for autonomous registration of a pulsed magnetic field contains an induction primary converter with a magnetic field concentrator and a coil wound on a magnetic field concentrator 1 loaded on a resistor 2, and a piece of thin wire 3 laid on the surface of thin-film magnetoresistors 5, 6 made of a ferromagnetic alloy with a rectangular hysteresis loop forming together with thin-film magnetoresistors 7, 8 of an identical with magnetoresistors 5, 6 ferromagnetic alloy with a rectangular loop hyster zis, opposite shoulders of the magnetoresistive bridge 4, the diagonals of which are connected to the electrical connector 9.

Device autonomous registration of a pulsed magnetic field works as follows.

Before starting the measurement cycle of the amplitude of the pulsed magnetic field, the magnetoresistive elements 5, 6, 7, 8 of the magnetoresistive bridge 4 are magnetized until the magnetization block 13 is saturated in the magnetic field. Then, the device containing the inductive primary converter 1 connected in series with the resistor 2 and a piece of thin wire 3 laid on the surface of magnetoresistive elements 5, 6, and magnetoresistive bridge 4, is placed in a controlled point in space with the necessary spatial orientation of the primary of the developer. When a measured magnetic field pulse (for example, from a lightning discharge simulator) acts on the primary transducer 1, a current pulse is induced in its coil, which flows through the load resistor 2 and the length of wire 3, exciting a secondary pulsed magnetic field around the length of wire 3, the lines of force of which lie in the plane of thin-film magnetoresistors 5, 6, demagnetizing them the more, the stronger the measured magnetic field. In this case, a proportional change in the magnitude of their resistances and a corresponding unbalance of the bridge 4. The ferromagnetic magnetoresistive elements 5, 6, 7, 8 register (remember) this state. After the pulse of the measured magnetic field passes, the magnetoresistive bridge 4 through the electrical connectors 9, 11 and the communication line 10 are connected to the reading information reading unit 12, using the controls of the block 12, the supply voltage is applied to one diagonal of the bridge 4, and the voltage is measured on the other diagonal of the bridge 4 imbalance proportional to the amplitude of the measured pulsed magnetic field.

A quantitative assessment of the effect of the invention can be carried out as follows.

We define the external magnetic field H in general as a function of time of infinite duration

H (t) = H _m 1 (t),

where H _m is the magnitude of the magnetic field;

1 (t) is the unit time function (“step”).

Then the EMF induced in the coil of the primary Converter 1, is written as

,

,

where Ψ (t) is the flux linkage due to an external magnetic field;

µ ₀ - magnetic permeability of air;

µ _eff is the relative effective magnetic permeability of the concentrator (core) of the primary transducer 1;

S _cat - the cross-sectional area of the coil of the primary Converter 1;

W is the number of turns in the coil of the primary Converter 1.

To simplify the calculations, we pass from the originals of the functions H (t) and ε (t) to their Laplace images:

H (p) = H _m / p,

ε (p) = µ ₀ µ _eff S _cat WpH (p) = µ ₀ µ _eff S _cat WH _m ,

where p is the Laplace operator, and we find the current in the series circuit of the primary transducer 1 with an emf ε (p) and passive elements L _cat and R _n neglecting the impedance of a piece of thin wire 3:

where L _cat - the inductance of the coil of the primary Converter 1;

R _n - load resistance 2;

- постоянная времени контура первичного преобразователя 1.

- time constant of the circuit of the primary Converter 1.

From the image (1) we find the original of the transition function of the current in the load circuit of the primary Converter 1.

Having put the coil of a flat, square section, it is possible to inductance its taking into account [5] in the form

where c is the side size of the square of the coil;

r is the thickness of the winding;

Ф = Ф (ρ) is the numerical function of the parameter ρ;

- геометрический параметр намотки катушки.

- geometric parameter of the coil winding.

, выражение (3) можно записать проще:Considering the winding is thin, such that

, expression (3) can be written more simply:

Substituting (4) into (2), taking into account the fact that S _cat = c ² , we have

Since the length of wire 3 is directly adjacent to the surface of thin-film (flat) magnetoresistive elements 5, 6 of the magnetoresistive bridge 4, the magnitude of the magnetic field H _cart (t) of the current i (t) acting on the elements 5, 6 with the approximate equality of the diameter d _{pr of} wire 3 and the widths of elements 5, 6 will be determined by the surface current density j (t) on wire 3:

Then the magnitude of the effect of increasing the sensitivity in the proposed device, in comparison with the prototype, will be determined by the gain K _us magnetic field H _cart (t) in comparison with the external field H (t) and for all pulsed actions for which t _char <<< τ , where t _har is the characteristic pulse duration, and taking into account (5) and (6) it will be equal to

Substituting in (7) the real numerical values of the parameters c≈10 mm, d _ave ≈0,1 mm at W → 1, we obtain K _yc ≈160, i.e. is at least two orders of magnitude.

It is possible to keep the time constant τ at the value required for measurements at one turn in the coil of the primary transducer 1 by optimizing the combination of parameters µ _eff , s and R _n .

The achieved dynamic range of the amplitudes of the intensities and the pulsed magnetic field, in which the proposed device is linearly and successfully functioning, was 5-500 A / m, or approximately 0.006-0.6 mT by field induction.

In order to increase the accuracy of measurements for each device for the autonomous registration of a pulsed magnetic field, it is necessary to construct a calibration graph by placing its field-sensitive assembly in a pulsed magnetic field with a known amplitude or induction amplitude. A typical calibration graph of the voltage imbalance of the magnetoresistive bridge (output characteristic of the device) Uout of the amplitude of the external magnetic field Hm is shown in Fig.2. From this graph it follows that the output signal of the device in the entire dynamic range is quite acceptable for perception by conventional digital devices.

The achieved main measurement error in the range of 5-500 A / m with pulse durations from 1 ns to 1 μs was ± 15%. The maximum storage time of the fixed state of the bridge unbalance is at least 6 months.

Thus, thanks to the adopted technical solutions, in the proposed device, in comparison with the prototype, the sensitivity to the magnitude of the magnetic field increased by at least two orders of magnitude, and also, due to the autonomous recording, the interference effect of electromagnetic fields on the measurement result is excluded.

Literature

1. Yu.V. Afanasyev, N.V. Studentsov et al. Measuring instruments for magnetic field parameters. L .: Energy, 1979, p. 166.

2. Copyright certificate of the USSR, No. 702325, cl. G01R 33/06, 1979.

3. M.L. Lamb. Micromagnetoelectronics, T.1. M. DMK Press, 2001, p. 140 (table 2.18, p. 4).

4. M.L. Barannikov Micromagnetoelectronics, T.1. M. DMK Press, 2001, p. 77.

5. P.L. Kalantarov, L.A. Zeitlin Calculation of inductances. L .: Energoatomizdat, 1986, pp. 360-361.

Claims (1)

A device for autonomous registration of a pulsed magnetic field, comprising a magnetoresistive bridge made by thin-film integrated technology, an electrical connector, characterized in that it contains an induction primary converter with a magnetic field concentrator and a coil wound around a magnetic field concentrator and connected in series with a resistor and a piece of thin wire, laid on the surface of two of the four magnetoresistors forming the opposite shoulders of the magnetoresistive bridge, p Therefore, thin-film magnetoresistors are made of a ferromagnetic alloy having a rectangular hysteresis loop.

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