SU1499292A1 - Apparatus for measuring magnetic fields - Google Patents

Abstract

The invention relates to magnetic measurements, in particular, to fluxgate magnetometers. The purpose of the invention is to improve accuracy and reduce power consumption. A device for measuring magnetic fields contains a ferrosonde 1, a conversion unit 2, a master oscillator 3, a binary counter 4, a phase-shifting circuit 5, a memory 6 and a digital-analog converter 7. 2 Il.

Description

i (L

four

WITH

with to

with

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The invention relates to magnetic measurements, in particular to flux-gate magnetometers.

The purpose of the invention is to simultaneously increase noise immunity and reduce power consumption of a device for measuring magnetic fields.

Fig. I is a block diagram of a device for measuring magnetic fields; 2 shows timing diagrams for the operation of the device.

The device contains a series-connected ferrosonde 1 and a conversion unit 2, a series-connected generator 3, a binary counter-divider 4 frequencies and a phase-shifting circuit 5, and also, consequently, a fixed memory (ROM) and a digital-analog converter 7, the output of which is connected to the excitation winding of the flux-gate 1, and the control inputs by coupling of the permanent storage device are connected to the outputs of the parallel code of the counter 4.

The way to set the variable

flooring is described by the following function:

I (t)

I / sin wt / sign sinwt,

Where

, tj)

f - w amplitude of alternating current; 2irf;

the frequency of the excitation signal can be any positive number.

By selecting the exponent m, it is possible to provide an optimal choice of the shape of the excitation signal for a given type of ferrosonde.

.) The device works as follows.

Using the master oscillator

3, the formation of pulse frequency (e.g., stabilized by quartz) is carried out. In the counter

4In the process of binary counting, there is a process of periodic accumulation of im-, pulses and zeroing of counter 4 at the moments of overflow, as a result of which the output code N of the counter (Fig. 2) is formed in the form of a periodic linearly increasing function contained in the time interval T

 r is the number of code combinations equal to 2, where n is the number of counter bits

o

5 0 5

0

five

0

five

0

five

4. To each code value I, corresponds to the address of the cell of ROM 6, in which the digital equivalent of the corresponding point of the alternating current function If (t), which is read by code N, is written and stored and fed to the input of the DAC 7 as an H code. 7 linear conversion of the N code into current and power amplification is carried out. Under the action of an external measured field, during the ferromodulated conversion, the output current of the measuring coil of the fluxgate 1 causes an alternating current voltage in the spectrum of which even-harmonics are contained. These are the components whose amplitude is proportional to the magnitude of the measured magnetic field induction. In the converter unit 2, the second harmonic signal of the output spectrum of the fluxgate is extracted and amplified and the DC voltage U is formed proportionally to the amplitude of the second harmonic, and hence the magnitude of the magnetic field induced by phase-sensitive alternating current voltage. The pulse sequence with a frequency twice the frequency of the excitation signal of the fluxgate from the first output of the divider counter enters the input of the phase shifter of the circuit 5. The phase of the control signals of the converter unit 2 is established with the help of the phase-shifting circuit 5 and the phase shift of the control signals is thereby compensated relative to the phase of the useful signals of the second harmonic of the excitation frequency f.

Claims (1)

Invention Formula A device for measuring magnetic fields containing a series-connected flux probe, a conversion unit, as well as a series-connected master oscillator, a binary counter and a phase-shifting circuit, the output of which is connected to the control input of the converter; block, characterized by the fact that, in order to improve accuracy and reduce power consumption; ferrosonde excitation circuits, additionally inserted in series with a permanent storage device and a digital-to-analog converter 1499292. at the receiver, the output of which is connected to the foot of the memory device under the exciter winding of the fluxgate, a. The read-out control inputs of a constant n-binary counter are connected to the outputs of the parallel code. 1L l l l V V v v yy f FIG. 2