SU1170390A1 - Ferroprobe magnetometer - Google Patents

Abstract

A ferrozondogometometer comprising an excitation generator, two ferromagnetic cores with excitation windings and a series-connected resonant amplifier, a detector, a measuring device, characterized in that, in order to improve the measurement accuracy, two linear inductances, two integrators, two bilateral limiters and a differential force are additionally introduced -tel, the excitation winding of the first ferromagnetic core connected to the output of the excitation generator in series with the first linear Inductance, the excitation winding of the second ferromagnetic core is connected to the output of the excitation generator in series with the second linear inductance, the connection point of the excitation winding of the first core and the first linear inductance is connected to the input of the first integrator, the output of which is connected to the input of the first two-sided limiter, the output connected to the first the input of the differential amplifier, the connection point of the excitation winding of the second core and the second linear inductance connected to the input of the second integrator, the output of which is connected to the input of the second two-way limiter, the output of the differential amplifier connected to the second input, to the output of which a resonant amplifier input is connected. about with so

Description

1 The invention relates to a measurement technique, intended for measuring constant and variable magnetic fields in geology, defect scopy, and as a receiver of the magnetic component of an electromagnetic field when solving a series of problems where conversion of a magnetic field into an electrical signal is required. The purpose of the invention is to increase the measurement accuracy by separating magnetic noise from the useful signal. In FIG. 1 shows the principle of the electrical circuit of the magnetometer; FIG. 2 shows a graphical understanding of the principle of operation of the device. The device contains an excitation generator 1 representing the voltage source, the first winding of the exciter with the first ferromagnetic core 2, the first linear inductance 3, the second winding of the exciter with the second ferromagnetic core 4, the second linear inductance 5, the first 6 and the second 7 integrators , the first 8 and second 9 double-sided stops, the differential amplifier 10, the resonant amplifier 11, the detector 12, the measuring device 13, while the excitation winding of the first ferromagnetic core 2 is connected to the output of the generator and excitation 1, successively with the first linear inductance 3, the excitation winding of the second ferromagnetic core 4 is connected to the output of the excitation generator 1 in series with the second linear inductance 5, the output of the second integrator 7 is connected to the input of the second double-sided suppressor 9, the output connected to the second differential input amplifier 10. The device operates as follows. The excitation generator 1 reverses the first ferromagnetic core 2 using the first excitation winding. As a result, a voltage drop is formed on the first linear inductance 3. This voltage is applied to the first integrator 6 (for example, an integrating RC chain), at the output of which it varies in shape — the pulses carrying information about the measured magnetic field are located in its upper 02 part. This makes it easy to separate the part of the voltage with the information signal from the part of the voltage containing magnetic noise 1 by two-way limitation from below. The voltage from the first integrator 6 is supplied to the first two-sided limiter 8, through which only that part of the pulse passes, the voltage that includes information about the measured field. From the first two-sided limiter (bottom) 8, the signal goes to the first input of the differential amplifier 10. Similarly, the signal from the second linear inductance 5 passes to the second input of the differential amplifier 10. The excitation windings .with ferromagnetic cores 2 and 4 are connected so that the current flowing into them creates in the volume of cores equal in size, but opposite in direction to the floor. If there is an external field directed along the cores, in the volume of one of them the difference in the field strengths of the field of excitation and the measured (external) field acts, in the volume of the other core - their sum. Thus, the signals arriving at the differential amplifier 10 are equal in the absence of a measured field and different in its presence. As a result of the subtraction of the signals on the differential amplifier 10, even harmonics of the excitation frequency are selected. From the output of the differential amplifier 10, the signal goes to the resonant amplifier 11, where the second harmonic is output, which goes to the detector 12 and the measuring device 13. The operation of the device can be seen in the diagrams in FIG. 2 and by comparison with the prototype. Consider the operation of a single core with an excitation winding and its corresponding channel up to differential amplification of FIG. Figure 2a shows the approximated magnetization curve of an 8 (H) ferromagnetic core of a fluxgate. As a result of the harmonic voltage of the generator, the excitation i, and the constant measured field HO induction of the heart

The nickname becomes a function of the HV time. The core periodically re-magnetized (Fig. 26, solid line).

FIG. Figure 2c shows the voltage form at the excitation winding of the core, And git, this voltage co, holds the second harmonic of the excitation frequency, carrying information about the measured magnetic field. Since the process of remagnetization of the core to saturation is accompanied by hysteresis and magnetic noise due to the discrete nature of the magnetization reversal of individual domains 1 and the microregions of the core — Barkgausen jumps, the voltage U (, (i} contains the noise-generating components.

For a circuit containing a series-connected voltage generator. (4),. an excitation winding with a ferromagnetic core and a linear inductance L, is performed

Kirchhoff's law. ,

er (t) ULltHU9 (t),

where ll (-fc) is the voltage across the linear inductance. With known

 erW E co5utnUBtt) k, (where K is the coefficient of proportionality) the voltage across the linear inductance is (Fig. 2d):

  E cogut-W, -jp.

The voltage U (i is fed to the input of the integrator, at the output of which we have the signal (J (i) completely coinciding in form with the current flowing through the inductance L, i.e. the excitation current of the fluxgate 1 g (t (Fig. 2a), because

UH (ibeW LjU ld E 5; ncot-ilsttb4,

where Hg is the excitation field of the fluxgate (Fig. 2a).

The function 6 () 1 contained in this expression containing the harmonics used to measure the magnetic field, Nd, can be represented as (Fig. 26)

Bit) - B 5 TiCoi B fBAt),

- constant value; Now on;

90,

6, (t) sequence

asymmetrical with respect to the zero level of the pulses.

Consequently, the useful signal in the form of even harmonics can be separated from the pulse train 8, (i),.

For the excitation current (Fig. 2a),

8W-- - Us; ncot (8 5; nui48), (t,

As can be seen from FIG. 2a, b, during

the action of pulses And, (t the core is in saturation, the process of magnetization reversal is completed and the accompanying magnetic noise is minimal. In addition, at these time intervals the voltage at the output of the integrator and k (t) - i in (Omeet value exceeding the figure determined by

using the Hg field (Fig. 2a), which allows, by means of a two-sided limitation on the bottom, to separate part of the voltage U (i (i) J containing magnetic noise from the information signal,

proportional to B (-t),

Thus, removing the voltage from the linear inductance, then conducting its integration and two-sided limiting from the bottom to the level.

determined by the saturation field H, it is possible to separate the magnetic noise from the signal, the harmonic components of which carry information about the measured field.

In order not to apply resonant

amplifiers with high selectivity to the second harmonic, which is technically difficult to implement, used a bridge circuit (differential two-element ferrosonde - two ferromagnetic cores with windings). The transformation channel of the ferromagnetic core (the second channel) operates in a manner similar to the first.

Winding of the second ferromagnetic

the ferrosonde element is turned on so that its field of excitation is shifted by 180 relative to the field of excitation of the first element. Therefore, if under

the influence of the external field g positive pulses at the output of the first channel increase in duration and amplitude, and the negative ones decrease, then at the output of the second channel, on the contrary, the negative ones increase and the positive ones decrease (FIG. 2d,

and). Outputs

and,

and

respectively

the first and second channels are connected respectively to the direct and inverse inputs of the differential amplifier. The output of which is the signal

& U (t) U, (t) -Uj (t) -B, {ibBj (t),

containing only even harmonics of the excitation frequency (Fig. 2g).

/ J

Claims (1)

A FERROZONDER MAGNETOMETER containing an excitation generator, two ferromagnetic cores with field windings and a resonant amplifier, a detector, a measuring device connected in series, characterized in that, in order to increase the measurement accuracy, two linear inductances, two integrators, two bilateral limiters and a differential amplifier are additionally introduced moreover, the field winding of the first ferromagnetic core 'is connected to the output of the field generator in series with the first linear inductor Obviously, the excitation winding of the second ferromagnetic core is connected to the output of the excitation generator in series with the second linear inductance, the connection point of the excitation winding of the first core and the first linear inductance is connected to the input of the first integrator, the output of which is connected to the input of the first two-way limiter, the output connected to the first input _l Nogo differential amplifier, a connection point § excitation winding of the second core and the second linear inductor is connected to a Odom second integrator whose output is connected to the input of the second bilateral limiter output coupled to a second input of the differential amplifier, which is connected to the output of the resonance amplifier input. SU, „. 1170390> 1170390 2