SU1265666A1 - Method of determining magnetic characteristics - Google Patents

Abstract

The invention relates to magnetic measurements. The purpose of the invention is to improve the accuracy of determining magnetic characteristics. The sample is re-magnetized by an external magnetic field, changing the latter in time so that the modulus of the gradient remains constant. In order to ensure the constancy of the registration error of the hysteresis loop of various samples, the value of the intensity of the external field at each time point must be set depending on the current values of both the derivatives of the magnetic induction and the intensity of the magnetic field in time, and the values of magnetic induction floor in ob- (L perce.

Description

The invention relates to magnetic measurements and is intended to determine the magnetic characteristics of ferromagnetic materials.

A known method for determining the magnetic characteristics of ferromagnetic materials, based on the reversal of the sample by an external magnetic field, measurement of the magnetic induction and the intensity of the magnetic field and their recording Q.

In the implementation of the known method, the law of changes in the external magnetic field on time in the process of reversal of the sample is established depending on the first derivatives of the magnetic induction and the intensity of the magnetic field in time. It does not take into account the current values of magnetic induction B and the intensity H of the magnetic field, but for different samples even the same material of the hysteresis loop may differ, both in configuration and in size. Due to these differences in the recorded hysteresis loss, the error in determining the magnetic characteristics of different samples also turns out to be different, namely, for samples with higher values of the main magnetic parameters, it increases. The uncertainty of the error makes it difficult to process the measurement results. Thus, the accuracy of the known method is insufficient.

A known method of obtaining static magnetization curves and hysteresis loops of samples of ferromagnetic materials, in which the sample is reversible by an external field and a sample hysteresis loop is recorded.

In this method, the effect of the hysteresis loop shape on the measurement error is taken into account, since the mode of magnetization reversal of the sample is established depending on its magnetic permeability, which is a differential characteristic of the shape of the hysteresis loop z.

I:

However, in this method, the difference in the sizes of the hysteresis loops of the distinguished samples leads to inconsistency in the detection of hysteresis loops. The inconstancy of the measurement error makes it difficult to process the measurement results | therefore, the accuracy of this method is insufficient.,.

The purpose of the invention is to improve the accuracy of determining magnetic characteristics.

The invention is clear. in the following way.

The internal magnetic energy E of the samples is an integral characteristic of their magnetic state in the process of magnetization reversal at each time point.

The eddy currents arising in the sample during magnetization reversal and the magnetic viscosity of the sample material lead to an increase in the recorded hysteresis loop compared to its static hysteresis loop, which causes an error in the determination of magnetic characteristics.

To ensure that the registration error of the hysteresis loop of different samples is constant, the value of the external field strength at each time point must be set depending on the values of both derivatives of magnetic induction and the magnetic field strength i in dB / dt and dH / dt, and caf / oix values of magnetic induction 6 and the intensity of the magnetic field H in the sample.

The module of the internal magnetic energy gradient characterizes the absolute error in determining the internal magnetic energy of the sample. Since the internal magnetic energy is P,

equals

four-..

E

(ABOUT

determined by the values of magnetic induction 5 achieved at a given time and the intensity of the magnetic field H, the error in determining it also characterizes the error in registering the hysteresis loop.

The internal magnetic energy is a function of two variables 5 and N, each of which in turn depends on time:

In B (t); H H (t).

(2)

From equality (1) and (2), by definition of the gradient, it follows that the modulus 55 of the gradient of the internal magnetic energy is

..f2E.dH.

g

| t) (||. | 5

(3)

) CHN dt

Since ЗЕ / 3 В Н and ЗЕ / ЗН В, THEN equality can be written as

- | j (“W

. (B. | S,

jgrad E

df

According to the proposed method, in the process of reversal of the sample by an external magnetic field, the latter is varied over time so that the magnitude of the gradient is kept constant, iT.e. provide equality performance

1 grand E

const

..-.

at any time t. The constancy of the modulus of the E gradient ensures the constancy of the absolute error in determining the magnetic state of the sample. Consequently, at each instant of time, for the same values, the sample dB / dt and dH / dt are derived from a sample with large current values of B and H, i.e. greater internal magnetic energy should be re-magnetized more slowly than a sample having smaller values of 1 and B and H.

Equation (4) and (5) implies that the error in determining the magnetic state of the sample at each time point is determined by the text values of dB / dt, dH / dt, B, and N. Therefore, constant ns1; in the modulus of the internal magnetic energy in the process, remagnetized ensures a constant error in determining the characteristics with different shapes and sizes of hysteresis loops.

Invention Formula

The method of determining the magnetic characteristics,. including reversal of the sample by an external magnetic field, measurement of magnetic induction and magnetic field strength, and their registration, characterized in that, in order to improve accuracy, derivatives of magnetic induction and magnetic field strength are additionally measured, and the intensity of the external magnetic field is changed, support constant Hbw the gradient modulus of the internal magnetic energy of the sample.

Claims (1)

Claim fifteen . A method for determining magnetic characteristics. including magnetization reversal of the sample by an external magnetic field, measurement of magnetic induction and magnetic field strength and their registration, which consists in the fact that, in order to increase accuracy, the magnetic induction derivatives of the magnetic field strength are additionally measured, and the external magnetic field strength is changed, maintaining constant modulus of the gradient of the internal magnetic energy of the sample.