DD293656A5 - ARRANGEMENT FOR AUTOMATIC MEASUREMENT MAGNETIC SIZES - Google Patents

Abstract

The invention relates to an arrangement for automatically measuring magnetic magnitudes on a sample vibrating in a direct magnetic field. The essential feature of the invention is that a phase-locked coupling between mechanical movement of the sample and electronic evaluation of the measured quantities polarization I and field intensity H during each individual oscillation of the sample results in a measurement at the same time. This gives the possibility of instantaneous detection, increases the accuracy of the Meszanordnung and increases the reliability in a high degree. The assembly can be used to measure small solids, powders, or tape pieces to determine characteristic magnetic values such as coercive field strength (Hc) and remanent polarization (IR). Fig. 1 {Meszanordnung; Coupling, phase-locked; Evaluation, electronic; Measurement, automatic; Instantaneous values; Powder; Bandstueckchen}

Description

For this 2 pages drawings

Field of application of the invention

The invention relates to an arrangement for automatically measuring magnetic quantities of small quantities of solids (powder, tape samples). It can be used in investigations of magnetic materials.

For the characterization of the magnetic properties of the substances important parameters such as the maximum polarization (l _m3 x), the remanent polarization (l " _m ), the coercive field strength (H _c ) can be determined. Since the magnetic field strength and the polarization are measured at the same time at each measuring time, the complete recording of the characteristic hysteresis loop is possible with suitable control of the arrangement. The invention belongs to the field of magnetic measuring technology.

Characteristic of the known state of the art

It is known that to measure the substantial magnetic quantities of solids, vibrating sample magnetometers can be used.

In this case, vibrations of the sample perpendicular to the magnetic field (DD-PS 93601) and parallel to the magnetic field (DD-PS 134142) are common. Important is the simultaneous detection of the resulting magnetic quantities for the polarization (I) and the field strength (H). An arrangement for this purpose is described in DD-PS 134144. The associated measuring method describes the DD-PS 137019. The display of the variables polarization and magnetic field strength take in the cited patents two Digitalvoltmetergruppen to 2 volt meters. These voltmeters are switched or stopped by a control circuit, which comes into force when the measurement is automatic. The disadvantage is that the system of mechanical vibration of the sample works independently of the electronic evaluation.

In the said arrangement, the polarity of the polarization I must be determined by auxiliary subassemblies, and all the values given are average values arising after integration of the rectified AC voltage.

All this leads to a long measuring time per automatic cycle and the susceptibility of the arrangement to temperature fluctuations and glitches.

Object of the invention

The aim of the invention is to eliminate the disadvantages mentioned. At the same time, it should be possible to detect instantaneous values of the magnetic quantities.

The economic effect consists in increasing the reliability of the measuring arrangement and in the saving of electronic assemblies. There is a time saving by shortening the measuring cycle. The evaluation of the measured data is facilitated since a constant number of data is recorded per measuring cycle.

-2- 293 656 Explanation of the nature of the invention

The invention has for its object to develop an arrangement for measuring magnetic quantities on a vibrating in a direct magnetic field sample (vibrating magnetometer), which allows the main magnetic quantities of solids such as the maximum polarization (I _n ,,,,) to automatically measure the remanent polarization (I _lem ) and the coercive field strength (H _c ), the reliability of the measurement being high and the measurement cycle being short. It must be possible to capture instantaneous values. During the measurement, the valid values for the polarization and the magnetic field strength should be continuously displayed.

The known arrangements do not meet these requirements. For an automatic measurement cycle, the individual tasks movement of the sample (4) in the same field (6), detecting the measured data and their processing, and to change the magnetic DC field (6) in the positive and negative directions to solve.

The invention relates to an arrangement for the automatic measurement of magnetic quantities, comprising (1) clock generator (1), multi-stage pulse divider (2), voltage synthesizer (3), sample (4) to be examined, and a transducer (5). in the magnetic track field (6), the amplifiers for the signals of the polarization and the magnetic field strength (7) and (8)> lit the downstream analog-to-digital converters (9) and (10) for the display and evaluation units (12) and (13) (each for the polarization and the magnetic field strength) and a selection circuit (11).

In order to be able to measure quickly and to acquire instantaneous values, it is necessary to obtain a measured value for the polarization and the applied magnetic constant field at each individual period of the vibration of the sample (4).

According to the invention, a measurement at each individual period is possible by the mechanical movement of the sample (4) is phase-locked coupled with the detection of the measured values by the analog-to-digital converters for the polarization (9) and the magnetic field strength (10).

This coupling is achieved by supplying the entire arrangement with a common clock generator (1) whose pulses reach a multistage pulse divider (2). This pulse divider has several outputs that are phase-locked together by predetermined divider ratios. The output a of the pulse divider (2) provides the alternating voltage with the frequency necessary for the oscillator (5).

The output b of the multi-stage pulse divider (2) gives a higher frequency to the input of the selection circuit (11). The selection circuit (11) outputs exactly one narrow pulse per period of the frequency of the output a to the analog-to-digital converters for the polarization (9) and the magnetic field strength (10). Due to the phase-locked coupling of all outputs of the multi-stage pulse divider, this narrow pulse is always at exactly the same time of each period of the AC voltage of the output a and thus to the same phase of movement of the sample (4) in the DC magnetic field (6). It is within the meaning of the invention to generate the narrow pulse of the selection circuit (strobe pulse) by a counter with a downstream decoder or by a shift register. It makes sense to choose the time for the strobe pulse at which the electrical signal representative of the current magnetic magnitudes is maximum. Thus, the amplifiers for the polarization (7) and the magnetic field strength (8) can be built more economically. Therefore, the connections between counter and decoder of the selection circuit (3) according to the invention are freely selectable. For the automatic measurement of all data of a hysteresis loop of magnetic materials, it is necessary that the DC magnetic field (6) changes up to a maximum value, then above zero to the maximum value of opposite sign and back above zero to the original maximum value. The control voltage for the thus changing magnetic field (6) is formed by the voltage synthesizer (3). For this purpose, the multi-stage pulse divider (2) with a fixed predetermined multiple frequency of the output a of the divider (2) at its output c pulses available. These arrive at the voltage synthesizer (3), which consists of a further counter with a downstream digital-to-analog converter, and are converted to the control voltage for the direct magnetic field (6). According to the invention, by coupling the voltage synthesizer (3) to the oscillator (5) by means of the multistage pulse filter (2), a predetermined relationship exists between the time of the automatic passage of the hysteresis curve (measurement cycle) and the number of recorded measured values per cycle.

It is within the meaning of the invention to selectively remove the output c of the multi-stage pulse divider (2) by switches of different stages of the pulse divider (2) to effect a change in the time of the measuring cycle. Advantageous in the context of the invention is to use the count of the counter in the voltage synthesizer (3) for the evaluation of certain magnetic variables such as the maximum field strength H _m "and the remanent polarization L, _e ,". Furthermore, it is advantageous to set by the counter start and end of the measurement cycle and thereby control the arrangement. At the same time, the number of data accumulating per measuring cycle is precisely known. This is advantageous for an evaluation of the data by means of an instrument computer which displays a part of the evaluation circuits for the polarization (12) and for the magnetic field strength (13) and after completion of the measurement cycle the characteristic magnetic values maximum field strength H _m , _x , coercive field strength H _c , maximum polarization l _mM and remanent polarization l " _{m determined} from the data recorded and stored during the measuring cycle. At the same time, the data is displayed concurrently during the measurement process.

It makes sense to build the clock generator (DaIs quartz generator and stabilize the amplitude of the vibrator (5) electromechanically.

embodiment

The invention will be explained below using an exemplary embodiment. For this Fig. 2 and Appendix 1.

The quartz generator 1 provides the pulses for the dividers 14,15,16 available. The divider chain is constructed so that the frequency at the output b corresponds to 16 times the frequency at the output a. The frequency of the output a (divider 16) is fed to a sinusoidal former 20, which for the oscillator 5 processes the shape of the oscillation with which the sample 4 vibrates in the constant field 6.

It makes sense to design the Sinusformer as a low-pass filter. The output b of the divider 14 provides the pulses for the counter 31 which, with the aid of the decoder 32, produces a 1-out-of-1 pulse.

By the vibration of the magnetized sample 4 in the constant field 6, a voltage is induced in the coil 22 (as a sensor for the Polaristion), which is an expression for the polarization I of the sample 4. This voltage is an AC voltage (towards Appendix 1), whose shape depends on the shape of the vibration of the vibrator 5, the amplitude of which depends on the size of the polarization I of the sample 4 and whose frequency is equal to the frequency of the vibrator 5. The said voltage has a phase angle of 0 ° with positive polarization and 180 ° with negative polarization (i in Appendix 1). The induced AC voltage is conditioned by the amplifier 7 for the polarization.

As a sensor for the applied field strength of the DC magnetic field 6 is a Hall probe 21, the Hall voltage of the amplifier 8 is processed for the magnetic field strength. Through the selection bridges 33 2 consecutive pulses of the decoder 32 are selected. The first pulse (f in Anaige 1) controls the sample and hold circuits 23 for the magnetic field strength and 24 for the polarization, the instantaneous values for the polarization (dashed segments of the curves h or i of Appendix 1) and the magnetic field strength while the second pulse (g in Appendix 1) effects the acquisition of the stored values into the analog-to-digital converters 9 for polarization and magnetic field strength 10 and their conversion in the transducers. The selection bridges are to be set so that there is a maximum for the applied signal for further processing and that the pulse for the analog-to-digital converter is always after the pulse for the sample and hold circuits. Those in the analog-to-digital converters 9 for the polarization and 10 for the magnetic field strength directly drive the associated tracking displays 25 and 26 and transmit the resulting data to the instrument computer 27 for storage. The divider 15 has a plurality of outputs c, which are selectively applied to the input of the up-down counter 17 by the selection switch of the cycle duration 30.

At the output of this counter, a digital-to-analog converter 18 is connected, which converts the voltage applied to its input counter reading in a DC voltage at the output. The up-down counter 17 is coupled in such a way that it passes through the necessary for the generation of positive and negative voltage by the digital-to-analog converter 18 counts as often as necessary for a complete recording of a hysteresis loop. At the same time, it supplies signals to the instrument computer 27 at certain counter readings in order to facilitate the evaluation of the measured data. If the measurement cycle is completed, the up-down counter 17 stops the clock generator 1, which is started by the start button 34 for a new measurement cycle. The DC magnetic field generating amplifier 19 converts the voltage of the D / A converter 18 into a current for the DC magnetic field generating coils 6.

After completion of the measurement cycle, the instrument calculator 27 determines the magnitudes maximum magnetic field strength H _max , coercive field strength H _c , maximum induction l _max and remanent induction l, _5m and outputs them on the display 28 of the instrument computer. He also operates a computer interface 29 for data output.

The entire circuit design can be designed using C-MOS series devices and monolithic analog-to-digital and digital-to-analog converters, respectively, so as to realize the measuring arrangement as a table concept.

Claims (2)

1. Arrangement for automatically measuring magnetic quantities of a sample in the DC magnetic field vibrating with digital electronic evaluation of the measurement signals for polarization and magnetic field strength, consisting of clock generator, multi-stage pulse divider, voltage synthesizer, the sample to be measured, oscillator, DC magnetic field, measuring amplifier for Polarization and for the DC magnetic field, associated analog-to-digital converters for the polarization and the magnetic field strength, a selection circuit and the evaluation circuits for the polarization and the magnetic field strength, the measurement signals for the polarization and the magnetic field strength processed in a known manner by amplifiers are characterized in that the basic clock of the clock generator (Dan a multi-stage pulse divider (2) is set, the first output a, the frequency for the oscillator (5) of the sample (4) provides and its second output b having a higher frequency in a fixed divider ratio to the output a pulses to a selection circuit (11), which at each period of the frequency of the output a of the multi-stage pulse divider (2) phase locked a pulse for taking over the values of the magnetic magnitudes from the amplifiers ( 7) and (8) in the analog-to-digital converter (9) and (10) and outputs that a third output c of the multi-stage pulse divider (2) pulses mi a higher frequency in a fixed divider ratio to the output a to one of a counter and a digital-to-analog converter voltage synthesizer (3), which generates in synchronism with the movement of the sample (4), the control voltage for the automatic change of the DC magnetic field (6). 2. Arrangement according to claim 1, characterized in that the selection circuit (11) consists of a pulse counter with a downstream decoder, wherein the coupling of the decoder to the counter is freely selectable by connections.