SU1613883A1 - Method of measuring induction of magnetic field - Google Patents

Abstract

The invention relates to magnetic measurements and can be used in the development of magnetic measuring transducers of constant and alternating magnetic fields used in geophysics. The aim of the invention is to improve the measurement accuracy. The device implementing the method comprises an excitation generator 1, a resistor 2, an inductor 3, a ferromagnetic core 4, a phase detector 5, an electronic controller 6, a feedback coil 7, a bias field coil 8, a bias current source 9, an indicator 10. The method involves exposing the core to a constant magnetic field until it is saturated. The magnitude of the magnetic field induction is determined by the phase shift between the excitation and resonance signals. 2 Il.

Description

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The invention relates to magnetic measurements and can be used in the development of magnetic measuring transducers of constant and alternating magnetic fields used in geophysics.

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

FIG. Figure 1 shows the dependence of the frequency of the mechanical resonance of a ferromagnet on the magnetic induction arising due to the E effect (change of the Young's modulus under the action of a magnetic field), where Bs is the induction of the saturation of the ferromagnet; Bxcm - magnetic displacement field; in fig. 2 is a block diagram of a device implementing the method.

FIG. 2 The following notation is accepted: excitation generator 1; resistor 2; inductance coil 3; ferromagnetic core 4; phase detector 5; electronic controller 6; feedback coil 7; displacement coil B; source 9 of the bias field current; indicator 10.

A change in the Young's modulus causes a change in the speed of propagation of the sound wave in a ferromagnet and, consequently, a change in the frequency of mechanical resonance. Prior to saturation induction (Fig. 1), the dependence of the resonant frequency of the magnetic field is linear, at least for iron-silicon-boron amorphous alloys. In the field of technical saturation, this relationship becomes nonlinear, but there is a section with a fairly high positive slope (the slope is positive if an increase in the floor causes an increase in the resonance frequency). By applying the displacement field, one can bring the ferromagnet to. plot with the highest positive slope. In this case, the zero phase shift corresponds to the induction of the displacement field.

The source 9 (Fig. 2) with the help of the coil 8 creates a magnetic bias field exceeding the saturation induction of the ferromagnetic core and the corresponding section with a positive slope (Fig. 1).

The generator 1 (Fig. 2) excites a ferromagnet (core 4) at the frequency of its mechanical resonance with the help of coil 3 through the isolating resistor 2. The resonance signal from the coil 3 and the excitation signal from generator 1 arrive at the phase detector 5. If the measured field differs From the induction of the displacement field between the excitation signal and the resonance signal, a phase difference appears. causing a voltage at the output of the phase detector proportional to the magnitude of the phase shift and in sign indicating an advance or a lag in the phase of the resonance signal relative to the excitation signal of the generator 1. The output of the phase detector is connected to the input of the electronic regulator 6, performing negative feedback on magnetic field using feedback coils. Any deviation of the magnetic field induction from the induction of the displacement field causes a phase shift between the excitation signal and the resonance signal, which is compensated for by negative feedback. The magnitude of the output signal of the electronic controller is proportional to the magnitude of the induction of the measured field, and the polarity of the output signal corresponds to the direction of the measured field.

Claims (1)

The invention The method of measuring the induction of a magnetic field, based on the effect on the core of the exciting magnetic field and the change in the resonant frequency. This also affects the core at the frequency of mechanical resonance. a constant magnetic field until it is saturated, corresponding to the positive slope of the characteristic magnetic field — the mechanical resonance frequency; the magnitude of the magnetic field induction is determined by the phase shift between the excitation signals and zonance, and the direction of the induction component is based on the sign of the phase difference. eight, SHU1 / In cm 6k