SU758024A1

SU758024A1 - METHOD OF MEASURING COERTSITIVE FORCE 1

Info

Publication number: SU758024A1
Application number: SU782612791A
Authority: SU
Inventors: Vladimir M Tyurin; Aleksandr Gridnev; Vyacheslav P Muzyukin
Original assignee: Vladimir M Tyurin; Aleksandr Gridnev; Vyacheslav P Muzyukin
Priority date: 1978-05-10
Filing date: 1978-05-10
Publication date: 1980-08-23

Description

The invention relates to the field of electrical measuring technology and can be used in the study and measurement of parameters of highly coercive materials.

A method for measuring coercive force by magnetization in both closed and open magnetic circuits is known. However, this method does not provide sufficient measurement accuracy due to the significant error in fixing the zero induction or magnetization of the measured sample.

A method for measuring coercive force is also known, according to which the number of periods of oscillations of a constant frequency is measured from the start of magnetization until the moment the induction reaches zero, and then the number of periods is measured from the moment the induction equals zero until saturation, whereby the desired parameter is characterized by the difference in the numbers of measured periods £2].

In its technical essence, the specified method is closest to the proposed one and was chosen as a prototype.

Another disadvantage of the known method is the low accuracy of fixation2

zero adjustment due to the large sensitivity zone of the zero indicators, as well as the error associated with the operation of integrating the information signal from the inductive converter.

The aim of the invention is to improve the accuracy of coercive force measurements.

This goal is achieved by the fact that in the method of measuring the coercive force by linearly changing the intensity of the demagnetizing field along the limiting hysteresis loop and simultaneously counting the number of pulses of constant frequency, demagnetization is carried out from the state of residual induction and the number of pulses of constant frequency P _o is measured from the beginning of demagnetization to the moment of the first coincidence

θ signal proportional to the rate of change of induction in the sample, with the reference signal, then demagnetization is continued and the number of frequency pulses P _σ /2 is measured until the moment of the second

$ coincidence of signals, and the coercive force is judged by the total number of measured pulses.

The essence of the invention is explained

figures, where Fig. 1 shows

θ functional diagram of the device for

3

758024

4

implementation of the proposed method, Fig. 2, 3 show timing diagrams explaining the operating principle of the device, and the dependence B=6(H) and L=G(H).

From Fig. 2 it follows that point Hς ₇ of the I=t(H) dependence corresponds in strength of the demagnetizing field to the inflection point “A” of the descending branch of the hysteresis loop B = t(H) or the maximum rate of change of induction in the sample.

The device implementing this method contains a control unit 1, a system for linear regulation of the magnetic field strength at

consisting of a linearly varying voltage generator 2, a controlled current source 3, an electromagnet 4 and a Hall sensor 5 included in the feedback circuit. The circuit for determining the extremum ^=max includes a series-connected inductive converter 6, an amplifier 7, a comparator 8, an electronic switch 9 and an inverter 10, wherein the second input of the comparator is connected to a reference voltage source 11. The measurement result indication unit consists of a quartz generator 12, a trigger 13, two AND circuits 14 and 15, an OR circuit 16 and a pulse counter 17. The AND circuits 14 and 15 are connected by their second inputs to the outputs of the electronic switch 9 and the inverter 10, respectively. The output of the switch 9 is connected to the second input of the pulse counter 17 through a differentiating circuit 18, an inhibit circuit 19 and a second electronic switch 20.

The device works as follows.

<p>The control unit simultaneously outputs synchronizing signals to generator 2 and to the "Start" input of pulse counter 17. In this case, the demagnetizing field strength changes linearly H = k1, and pulses of the reference frequency P _o are fed to counter 17 through the AND circuit 14 and the OR circuit 16. The latter is possible, since at = at the second input of the AND circuit 14, there is a high potential. In the time interval ^ν 6 ^>ν<sub>οπ</sub> ^and the AND circuit 14 is inhibited,</p>

and the AND 15 circuit is open, and through the trigger 13, the AND 15 and OR 16 circuits go to the counter

pulses with a frequency of P _o /2 are supplied. At the moment of the second coincidence ΐ = ν _0η , the differentiating circuit 18 generates a positive pulse, which is fed through the inhibit circuit 19 and the switch 20 to the "Stop" input of the counter and stops it. At the moment of time t _1, the negative pulse from the differentiating circuit 18 to the counter input will not pass through the inhibit circuit 19.

Thus, the measurement of the magnetic field strength proportional to the coercive force is reduced to measuring the time interval from the start of demagnetization to the moment of reaching the maximum voltage Y&=max, and the moment of the maximum is determined by the method of double comparison of the information signal with the reference signal and dividing the time interval between the two coincidences of the above-mentioned signals in half, which allows for a significant increase in the accuracy of measuring the coercive force.

Claims

Claim

The method of measuring the coercive force by linearly varying the intensity of the demagnetizing field along the limiting hysteresis loop and simultaneously counting the number of pulses of constant frequency, characterized in that, in order to increase accuracy, demagnetization is carried out from the state of residual induction and the number of pulses of constant frequency P _{o is} measured from the beginning of demagnetization to the moment the first match of the signal, proportional to the measurement rate of induction in the sample, with the reference signal, then continue demagnetization and measure h pulse frequency layer P _o / 2 until the second coincidence signals and the coercivity is judged by the total number of measured pulses.