RU2316781C1 - Digital ferro-probe magnetometer - Google Patents

Abstract

FIELD: ferro-probe radar magnetometers.

SUBSTANCE: digital ferro-probe radar magnetometer has master oscillator, sinusoid former, which has output connected with first inputs of ferro-probes, and digital-to-analog converters. Outputs of ferro-probes are connected with inputs of selective amplifiers. Ferro-probe magnetometer has logic unit, and sample and storage unit. Any channel of magnetometer is enclosed by deep negative magnetic field feedback. Separation of windings of ferro-probe and application of three independent measuring channels results in high reliability of magnetometer. Magnetic field induction vector is measured with high precision.

EFFECT: improved precision of measurement; higher stability of measurement.

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Description

The invention relates to fluxgate navigation magnetometers and can be used to measure the three orthogonal components of the Earth's magnetic field induction vector and to provide signals proportional to the measured components in the form of a digital code.

A device is known for measuring magnetic field strength in accordance with RU 2155968 C2 of 09/10/2000, MKI: G01R 33/02, containing a rectangular pulse generator, a flux gate with a core made of permalloy with a hysteresis loop with a square ratio close to unity, to the output the winding of which is connected to the integrator. The output of the integrator is connected to the input of the amplifier, the output of which is connected to the input of the threshold block. The first AND gate is connected in series with the first reversible pulse counter, a digital-to-analog converter controlled by a current source, a key, and an excitation coil of a flux gate. The second input of the first reversible pulse counter and the first input of the first logic element AND are connected to the output of the threshold block, the second logic element And and the second reversible pulse counter. The output of the generator is connected to the first inputs of the second logic element And and the second reversible pulse counter, the output of the second logic element And is connected to the second inputs of the first logic element And, the second reverse pulse counter and key, the third input of the second reverse pulse counter is connected to the output of the first reversible pulse counter , and the output is to the second input of the second logic element.

The disadvantage of this device is, despite the additional element And and a reversible counter, a complex conversion circuit and the inability to adjust zero to measure the absolute value of the components of the magnetic field induction vector.

The closest in technical essence to the proposed one is a flux-gate magnetometer according to RU 2153682 from 07.27.2000, MKI: G01R 33/02, which includes three fluxgates with mutually orthogonal magnetic axes and series-connected output windings and field windings connected to the corresponding outputs switched excitation unit, series-connected amplifier-converter unit connected to the output winding of the first flux gate, the first threshold device and the OR element, connected in series data is an integrator, the control input of which is connected to the output of the OR element, and the third to the output of the inverter, and a second threshold device, a recording unit, a control unit, a generator, the first, second and third outputs of which are connected respectively to the control input of the amplifier-converter unit, frequency the input of the switched excitation unit and the control (synchronization) input of the control unit, the first to fourth outputs of which are connected respectively to the first to fourth inputs of the control of the switched block and excitations, an integrating unit with linear and quadratic outputs, the frequency input of which is connected to the fourth output of the generator, the first linear output is with the second input of the first threshold device and with the input of the integrator, the second is with the information input of the recording unit, the quadratic output is connected with the second input of the second threshold device, and the first and second control inputs respectively with the fifth and fourth outputs of the control unit, the first and fifth through an inverter, the outputs of which are connected respectively to the inputs and the And element, the output of which is connected to the integrator zeroing input, the mode setting unit and the logic device, the first input of which is connected to the output of the second threshold device, the eleventh, eighth, fifth and second inputs are connected respectively to the first to fourth outputs of the control unit, twelfth, ninth , the sixth and third inputs are connected respectively to the first to fourth outputs of the mode setting unit, the fourth, seventh and tenth inputs are connected to the output of the first threshold device, and the output to the control input of the register guide block. This fluxgate magnetometer is selected as a prototype.

The disadvantage of this magnetometer is its low reliability, accuracy and stability of measurement of the components of the magnetic field induction vector. When the circuit of the series-connected windings of flux gates is broken, information on all three components is lost.

The aim of the invention is to improve the accuracy and stability of the measurement by introducing deep negative feedback across the field and increasing the reliability of the device by simplifying the algorithm for the conversion and separation of the flux-gate windings.

To achieve this goal, a logic unit and sampling-storage devices 8, 9, 10 are introduced into the digital flux-gate magnetometer, the first inputs of which are connected to the outputs of selective amplifiers 5, 6, 7, respectively, the first outputs are connected to the first inputs of analog-to-digital converters 11, 12 , 13, respectively, the second outputs are connected to the second inputs of the flux gates 2, 3, 4, respectively, the control logic unit 14, the first output of which is connected to the input of the power supply 1, the second output is connected to the second inputs of the devices RCT-storage 8, 9, 10, a third output connected to second inputs of analog-to-digital converters 11, 12, 13, and the control logic block input 14 connected to the output of the master oscillator 15.

The essence of the invention is illustrated by drawings, in which Fig. 1 shows a block diagram of a digital flux-gate magnetometer, Fig. 2 is a schematic diagram of one channel of a digital flux-gate magnetometer, and Fig. 3 is a voltage diagram of a circuit of a single channel of a digital flux-gate magnetometer.

A digital fluxgate magnetometer consists of a sinusoid former 1, fluxgates 2, 3, 4, selective amplifiers 5, 6, 7, sample-storage devices 8, 9, 10, analog-to-digital converters 11, 12, 13, a logic unit 14, and a master oscillator 15. Shaper 1 of the sine wave, the logic unit 14 and the master oscillator 15 are common to all three measuring channels.

The device operates as follows.

The measurement of the three components of the magnetic field induction vector is carried out by three independent channels X, Y and Z. All channels are made according to identical schemes. Consider the operation of one channel. The frequency from the master oscillator 15 is fed to a logical unit 14, in which frequency grids are formed, which are supplied to the sinusoid shaper 1 and to the control of the storage sampling device 8. In the logic block 14, a signal is also generated to control the analog-to-digital converter 11. In the shaper 1 digitally a sinusoidal voltage Uv is formed with a frequency fv = 10 kHz, which is supplied to the excitation winding of the flux gate 2. The flux gate converts the external signal acting on it (the projection of the magnetic induction vector Proportion on its longitudinal axis) in the AC electromotive force containing the even harmonic frequencies of the excitation signal. The amplitude of this emf is proportional to the value of the magnetic field induction, and the phase changes by π radian when the direction of the field induction vector changes by 180 °. There is also interference in the output emf of the fluxgate, which has odd harmonics in the spectrum.

Figure 2 shows a schematic diagram of a selective amplifier, a logic unit, a sampling-storage device and an analog-to-digital converter. The selective amplifier is designed to isolate from the general spectrum of the signal coming from the measuring winding of the flux gate, the voltage of the second harmonic and its amplification to the desired value. The gain at the resonant frequency (fp = 20 kHz) -Kr = 5000. The passband is 2Δf = 1800 Hz. The transmission coefficient at the frequencies of the first and third harmonics of the excitation frequency of the flux gate is not more than 30 and 10, respectively.

Thus, the second harmonic 2fv = 20 kHz, which is amplified to the value of Uf and then fed to the sampling-storage device 8, is extracted from the output emf of the flux-gate by selective amplifier 5.

Figure 3 shows four sine waves:

+ Umax - the maximum positive value of Uf;

-Umax - maximum negative value of Uf;

+ Ui is one of the intermediate positive values of Uф;

-Ui is one of the intermediate negative values of Uf.

Using the logical block 14 in the device, the selection-storage 8 once a period is the memorization of a certain value of Uf. The constant voltage Uext from the output of the sample-storage device 8 is fed to the input of an analog-to-digital converter 11, where it is converted into a digital code N = f (Bx), which is proportional to the projection of the magnetic field induction vector. The moment of starting the conversion of Uf into a digital code is delayed by the time Δt to exclude the influence of transients. The processes of forming a sinusoid, sample-storage and analog-to-digital conversion are synchronized by the frequency of the generator 15. The position of the sample on the sinusoid Uf is determined by the logical unit 14 based on the condition of the necessary steepness of the output characteristic of the magnetometer. To stabilize the transmission coefficient, each channel is covered by a negative field feedback circuit. The negative feedback signal is taken from the outputs of the sample-storage devices 8, 9, 10 and is fed to the feedback windings of the flux gates.

The separation of the flux-gate windings and the use of three independent measurement channels made it possible to increase the reliability of the magnetometer.

The introduction of a sampling-storage device, a logical unit, and a negative feedback loop across the field significantly improved the accuracy and stability of measurements.

Of the patent information materials known to the applicant, no signs were found that are similar to the totality of the features of the claimed object.

This device has been tested on a prototype. The test results indicate the achievement of the task. FSUE NPOPM proposes to use this technical solution on standard products.

Claims (1)

A digital fluxgate magnetometer containing a master oscillator, a sine wave shaper, the output of which is connected to the first inputs of the fluxgates, the outputs of which are connected to the inputs of the selective amplifiers, and digital-to-analog converters, characterized in that a logic unit and sampling-storage devices are introduced into the magnetometer, the first inputs of which are connected with outputs of selective amplifiers, the first outputs are connected to the first inputs of analog-to-digital converters, the second outputs are connected to the second inputs of flux gates, l a logical control unit, the first output of which is connected to the input of the power source, the second output is connected to the second inputs of the sample-storage devices, the third output is connected to the second inputs of analog-to-digital converters, and the input of the logical control unit is connected to the output of the master oscillator, each magnetometer channel is covered deep negative magnetic field feedback.

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