SU658513A1 - Arrangement for determining magnetic properties of specimens made of magnetic-soft materials - Google Patents

Description

one

The invention relates to a measuring technique and can be applied for determining the magnetic properties of ferromagnetic materials and recording with the help of a recorder periodic high-frequency signals obtained by re-magnetization of samples of such materials.

Strobe devices for studying the magnetic properties of samples of ferromagnetic materials are known, which contain sources of magnetizing currents, stroboscopic mixers, an integrator, a system for shifting strobe pulses 1.

However, the measurement accuracy of such devices is insufficient.

Also known are devices that include a standard signal generator, connected to the input of a power amplifier, a pulse shift system on a phase shifter, a voltage regulator connected to the magnetizing winding of a test sample, in series with which a resistor is connected, two strobe mixers, each of which through corresponding pulses digital voltmeters are connected to digital printers, and the measuring winding of the core through

the integrator is connected to the input of one stroboscopic mixer, the magnetizing winding through a resistor is connected to the input of another strobe mixer 2.

Signals proportional to the values of H — the intensity of the magnetic field and B — the induction in the test sample are fed to the input of the mixers. In the initial state, the mixers are closed and open only for the duration of the strobe pulses coming from the node of their automatic shift and formation. The mixers open and thereby read the instantaneous values of the signals. The voltage at the output of the mixers is measured by digital pulse voltmeters.

However, in such a device, when magnetically soft materials are studied in fast-changing magnetic fields (for example, nano- and microsecond ranges), a significant fault occurs due to the inertia of the recording devices.

The purpose of the invention is to improve the measurement accuracy.

For this purpose, a device for determining the magnetic properties of samples from magnetic materials, containing a series-connected master oscillator, a magnetizing current generator, a magnetizing winding of the sample under test, and a resistor, successively connected to the sample sample winding, the first stroboscopic mixer, the first filter - amplifier, and the first integrator connected to a second stroboscopic mixer and a second filter amplifier connected in series to a resistor; a fast sawtooth generator, a reference element and a pulse generator, a output connected to the second inputs of both stroboscopic mixers and a slow sawtooth generator, are inputted by a generator; a rectifier connected in series, a second integrator and a subtractor, the rectifier input connected to the first filter output -amplifier, the output of the slow sawtooth generator is connected to the second input of the subtraction unit, and the output of the latter is connected to the second input of the ementa comparison. FIG. 1 given the structural scheme of the proposed device; in fig. 2 - time diagrams of the device operation. The device contains a master oscillator 1, the oscillator 2 magnetizing current pulses; magnetizing winding 3 of the test sample; test sample 4, measuring winding 5 of the test sample; strobe mixers 6 and 7, respectively, of the induction and magnetic field measurement channels, filter amplifiers 8 and 9, respectively, of the induction measurement channels and the magnetizing field, the integrator 10 of the induction measurement channel, rectifier II; feedback circuit integrator 12, subtraction unit 13, slow sawtooth generator 14, stroby pulse shaper 15; reference element 16; a fast sawtooth generator 17, a resistor 18. The device operates as follows. The signals of the master oscillator 1 start the generator 2 magnetizing current pulses. Under the influence of current pulses entering the magnetizing winding 3, the test sample 4 is magnetised and an emf is induced in the measuring winding 5 proportional to the rate of change of the magnetic flux (induction) in the sample. This signal enters mixer 6. In mixer 7, a resistor 18 connected in series with the magnetizing winding receives a voltage proportional to the magnetizing current (magnetic field strength). From the master oscillator 1, a fast sawtooth voltage generator 17 is also started. The "fast saw" voltage is supplied to one of the inputs of the comparison element 16, to the second input of which the voltage of the slow sweep Up is applied. At the moments of equality of the voltage of the fast sawtooth and slow sweep, the pulses shifted in relative to the pulses of the master oscillator appear at the output of the comparison element 16. The time shift of the received pulses will be proportional to the instantaneous value of the qaaBHHBae.Mbix pressure. In view of the fact that the rate of change of the fast sawtooth voltage is chosen constant, the change in the time shift of the pulses will be determined by the instantaneous value of the voltage of the slow sweep. From the output of the comparison element 16, the pulses go to the driver of the 15 strobe pulses. The latter enter the mixers 6 and 7. As a result of the interaction of the strobe pulses and signals from the test sample, the mixer produces signals that follow the filter amplifiers 8 and 9. At the output of the filter amplifier 8, a time-transformed signal is obtained} 1al proportional to the rate of change of the magnetic flux (induction) d willow) ;. , and at the output of the amplifier 9 - a signal proportional to the intensity of the magnetic field - Uv. Next, the signal from the output of the filter amplifier 8 goes to the integrator 10, the output of which receives a voltage proportional to the magnetic flux (induction) - Ubfcu.B. From the output of the filter amplifier 8, a voltage proportional to the rate of change of the magnetic flux (induction) in the sample ( see Fig. 2a), enters rectifier 11, where the selection of a signal proportional to the module of the input signal occurs (cf. Fig. 26). Then the voltage is proportional to the module of the rate of change of the magnetic flux fed to the integrator 12 of the feedback circuit. The voltage at the output of the integrator 12 is shown in FIG. 2c. The received signal is fed to one of the inputs of the subtraction unit 13, to the second input of which from the generator 14 a slow saw-tooth voltage U "n. From block 13, where the incoming voltages are subtracted, the slow sweep voltage Up is applied to one of the inputs of the comparison element 16. At the output of subtraction unit 13, the slow sweep voltage is reduced by an amount proportional to the change in the magnetic flux in the sample at the moments when these measurements occur. This leads to a decrease in the time shift of the strobe pulses and an increase in the time of registration of a part of the signals, where the rate of change of the magnetic flux is quite large (see Fig. 2e).

Claims (2)

1. Chernyshev E. T. et al. Magnetic measurements. M., ed. Committee of Standards, 1969, p. 39 2. USSR author's certificate number 353222, cl. G 01 R 33/12, 1971. dj