RU1774296C - Magnetic field metering device - Google Patents

Abstract

The invention relates to techniques for magnetic measurements and can be used in instruments and devices for measuring the magnetic induction of a constant or slowly changing magnetic field. The aim of the invention is to increase the accuracy and range of the measured magnetic fields. The goal is achieved by the fact that a differentiating circuit, a voltage comparator, a synchronization pulse shaper and a D-trigger, as well as a rectangular symmetrical pulse shaper 1 zp are introduced into the device f-ly, 2 ill.

Description

The invention relates to techniques for magnetic measurements and can be used in instruments and devices for measuring the magnetic induction of a constant or slowly changing magnetic field.

The purpose of the invention is to increase accuracy and expand the measurement range.

In FIG. 1 shows a functional diagram of the device; in Fig 2 - timing diagrams of the operation of its functional units.

The device (Fig. 1) contains an excitation generator 1 supplying a triangular bipolar current d (see Fig. 2a) a solenoidal coil 2, inside which a thin-film magnetoresistive element (MRE) 3 of an iron-nickel alloy is deposited on a substrate (in the figures not shown) MRE 3 is included in the four-arm resistive magnetoresistive bridge 4 circuit (the remaining arms are resistors R1 and R2), which is powered by a direct current source 5. The measuring diagonal of the bridge 4 is connected to the input of the amplifier 6, to the output

of which a differentiating circuit 7 is connected, and its output is connected to one of the inputs of the comparator 8, to the other input of which a constant reference voltage Don is applied. A synchronizer pulse generator 9 is connected to the output of the comparator 8, the output of which is connected to the synchronization input of the D-trigger 10, the outputs of the D-trigger 10 are connected to the inputs of the recording device 11. The information input of the D-trigger is connected to the output of the rectangular symmetrical pulse generator 12, the input of which connected to the output of excitation generator 1.

The device operates as follows.

The generator 1 supplies a triangular bipolar current to a solenoidal coil 2, as a result of which an alternating magnetic field Hd is created inside it having the same time dependence as q (see Fig. 2a). The amplitude of the current is chosen such that the amplitude of the field is NT

Yo

VJ XI N GO

u o

there was a greater value of the anisotropy field Hk (Fig. 2a), at which the magnetoresistive characteristic of the thin-film MRE saturates. Due to this, as can be seen from Fig. 26, the MRE is in the saturation state most of the time T (and its resistance is minimal). and at times ti, t2, tz, t4, when the field strength acting on the MRE 3 is zero, it goes out of saturation and its resistance increases. Obviously, under the same law of changing the resistance of the MRE with the constant current through the MRE 3, which is provided by the choice of the ratios of the arms R1, R2 of the bridge 4, the voltage drop across the MRE and the output voltage of the bridge 4 A Dm, in which the MRE 3 is connected, change. (Capacitor C of Fig. 1 is turned on to prevent the voltage drop of the wanted signal from resistor R2). Therefore, FIG. 26 illustrates not only the change in the resistance of the MRE 3, but mainly the output voltage of the resistive-magnetoresistive bridge 4.

In the absence of a constant (measurable) field Н А Н 0 (see Fig. 2a, column T), the moment of equality to zero (ti, t2, t3-t) follows evenly through each half of the period of the excitation frequency (РВзб 1 / Т ), Under the action of a constant magnetic field with a strength, for example, equal to N AN (see Fig. 2a, column II), the uniformity of the following these moments of time is violated: the moments ti and t2 are consumed by a certain amount of 2 At, and r and ts approach each other by the same amount. Under the influence of a constant field of the same value, but the opposite polarity H - L H, the picture becomes opposite (see figa, column). It is easy to show that the temporal displacement of the moments ti ..., t4 is related to the value of the constant field А Н by the dependence

A.-JANG

Nt

those. in the triangular shape, the field of the coil 2 between At and A H there is a direct proportionality and correspondence of the directions of movement of the moments t, ..., t4 to the directions of action of the field AN.

The amplifier 6 amplifies and inverts the voltage of the bridge AUm (see Fig. 2 b, c) and from the output of the amplifier 6, the voltage Uy is supplied to the input of the differentiating circuit 7, which is designed to more clearly isolate and fix the moments ti. ..,

t4 (see FIG. 2d). From the output of the differentiating circuit 7, the voltage of the IDC goes to the input of the comparator 8, and from its output, the voltage UK is applied to the input of the generator 9 synchronization pulses, which generates short synchronization pulses 1) fsi with the edges most accurately fixing

time moments ti t. 4 (see fig.2d, e).

IFSI pulses from the output of the shaper 9

synchronization pulses are fed to the synchronization input of the D-flip-flop 10. To the output of the excitation generator 1, a rectangular symmetric pulse generator 12 is connected, which generates the IF pulses shown in Fig. 2g. It can be seen that the logical 1 level of these pulses corresponds to changes in the field Nd values from - NT to + NT, and to the logical O - transitions from + Hm i -Hm. These pulses arrive at

the information input of the D-flip-flop 10, by means of which the temporary sequences of short pulses ifsi are converted into a sequence of pulses (at the outputs of the flip-flop) UTp and Llfp, modulated in width in accordance with dependence (1) (see Fig. 2k, l).

Obviously, the average values of the pulse voltages UTp and Ufp at the outputs Q and Q (at their constant amplitude)

proportional to the values of 2 At and, consequently, to A. N. The outputs of the D-flip-flop 10 are connected to an information presentation device - a recording device 11 that responds to the difference in average values

voltage Ucp (see Fig. 2m) coming from the outputs Q and Q of the D-flip-flop 10, which is proportional to the measured constant field AH, i.e.

UCp Ki At KAH,

where K, Ki are the proportionality coefficients. Thus, the converter provides a linear dependence of the output voltage on the measured magnetic field.

Claims (2)

1. A device for measuring a magnetic field containing an excitation generator, a solenoidal coil connected to it, in which is placed thin-film magnetoresistive element included in a bridge resistive magnetoresistive circuit powered by a constant current source, connected to the measuring diagonal of the bridge amplifier and a recording device, characterized in that. that, in order to increase the accuracy and extend the measuring range, the device additionally introduced a series-connected differentiating circuit, a voltage comparator, a synchronization pulse shaper and a D-trigger, as well as a rectangular symmetrical pulse shaper, the input of which is connected. the output of the excitation generator, the output to the information the input of the D-trigger, and the input of the differentiating circuit is connected to the output of the amplifier, 2. Device pop. 1, characterized in that the excitation generator is made in the form of a triangular-shaped current pulse generator. Fie. 1