RU2549545C2 - Digital ferroprobe magnetometer - Google Patents

Abstract

FIELD: measurement equipment.

SUBSTANCE: digital ferroprobe magnetometer includes a setting generator, the output of which is connected to the input of a logic control unit, the first output of which is connected to the input of a sinusoid shaper, the output of which is connected to the first inputs of three ferroprobes, the outputs of which are connected to inputs of three selective amplifiers, the first outputs of which are connected to the first inputs of three sampling-storage devices, the first outputs of which are connected to the second inputs of three ferroprobes, and the second inputs are connected to the second output of the logic control unit, the third output of which is connected to the second inputs of analogue-to-digital converters, in addition, it includes three adding amplifiers and three sampling-storage devices of quadrature voltage, the first inputs of which are connected to the fourth output of the logic control unit, the second inputs are connected to the second outputs of selective amplifiers, and outputs are connected to the second inputs of the adding amplifiers, the outputs of which are connected to the first inputs of the analogue-to-digital converters, and the first inputs are connected to the second outputs of sampling-storage devices.

EFFECT: increasing stability of a measurement channel of a magnetometer, accuracy and stability of measurements.

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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 for measuring magnetic field strength according to RU 2155968 C2 of 09/10/2000, MKI: G01R 33/02, comprising 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 logical element And and the second reversible pulse counter, the output of the second logical element And is connected to the second inputs of the first logical 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 2316781 C1, 02/10/2008, IPC: G01R 33/02, which includes a master oscillator, the output of which is connected to the input of the logic unit, the first output of which is connected to the input of the sine wave former, the output which is connected to the inputs of three flux gates, the outputs of which are connected to the inputs of three sampling-storage devices, the outputs of which are connected to the inputs of three analog-to-digital converters. This fluxgate magnetometer is selected as a prototype.

The disadvantage of this magnetometer is the low stability of selective amplifiers and the measurement error of the components of the magnetic field induction vector, due to the bias voltage of the measurement circuit.

The objective of the present invention is to increase the stability of the magnetometer circuit and eliminate measurement errors caused by stray bias voltage by introducing sampling devices - storing quadrature voltages and summing amplifiers.

To solve this problem, a digital fluxgate magnetometer containing a master oscillator 15 (ZG), the output of which is connected to the input of the logic control unit 14 (LB), the first output of which is connected to the input of the sine wave shaper 1 (FS), the output of which is connected to the first inputs of three fluxgates 2, 3, 4 (Ф3), the outputs of which are connected to the inputs of three selective amplifiers 5, 6, 7 (DUT), the first outputs of which are connected to the first inputs of three devices 8, 9, 10 of sampling-storage (UVX), the first outputs which are connected to the second inputs of three f of the balloons 2, 3, 4, and the second inputs are connected to the second output of the control logic unit 14, the third output of which is connected to the second inputs of the analog-to-digital converters 11, 12, 13 (ADC), three summing amplifiers 19, 20, 21 (SU ) and three devices 16, 17, 18 sampling-storage of quadrature voltages (UVHKN), the first inputs of which are connected to the fourth output of the logical control unit 14, the second inputs are connected to the second outputs of the selective amplifiers 5, 6, 7, and the outputs are connected to the second inputs summing amplifiers 19, 20, 21, outputs of which ryh are connected to the first inputs of the analog-to-digital converters 11, 12, 13, and the first inputs are connected to the second outputs of the storage sampling devices 8, 9, 10.

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 flux-gate magnetometer consists of a sinusoid former 1, flux-gates 2, 3, 4, selective amplifiers 5, 6, 7, sampling-storage devices 8, 9, 10, sampling-storage devices of quadrature voltages 16, 17, 18, summing amplifiers 19, 20, 21, analog-to-digital converters 11, 12, 13, the control logic unit 14 and the master oscillator 15. The sine wave generator 1, the logic block 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 X.

The frequency from the master oscillator 15 is supplied to the control logic unit 14, in which digital signals are generated that are supplied to the sine wave former 1, to the storage sampler 8, to the quadrature voltage storage sampler 16 and to the analog-to-digital converter 11. In the digital sine wave former 1 The method generates a sinusoidal voltage Uv with a frequency fv = 10 kHz, which is applied to the excitation winding of the flux gate 2. The flux gate 2 converts the external signal acting on it (projection of the inductor vector and a magnetic field on its longitudinal axis) in the emf of an alternating current containing even harmonics of the frequency 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 180º. There is also interference in the output emf of the flux-gate 2, which has odd harmonics in the spectrum.

Figure 2 shows a schematic diagram of a selective amplifier 5, a logical control unit 14, a sampling-storage device 8, a sampling-storage device 16 of a quadrature voltage, a summing amplifier 19 and an analog-to-digital converter 11. Selective amplifier 5 is designed to extract from the total signal spectrum coming from the measuring winding of the flux gate 2, the voltage of the second harmonic and amplifying it to the desired value. The gain at the resonant frequency (fp = 20 kHz) -Kr = 2500. 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 2fB = 20 kHz is extracted from the output emf of the flux-gate by selective amplifier 5, which is amplified and then fed to the sampling-storage devices 8 and the quadrature voltage storage sampling device 16 in the form of quadrature voltages Usin (output U3, FIG. 2) and Ucos (output U2, Figure 2), equal in amplitude.

Using the logical unit 14 in the sample-storage device 8 and the quadrature voltage storage sample device 16 once per period at the time points Δt and Δt + T / 4, not one prototype Usin, but two values Usin and Ucos. Constant voltages Uвх and Uвхкн from the outputs of the sample-storage device 8 and the quadrature-voltage sample-storage device 16 are supplied to the input of the summing amplifier 19, where they are summed up and the output voltage of the summing amplifier 19 is supplied to the input of the analog-to-digital converter 11, where it is converted to digital code N = f (Bx), proportional to the projection of the magnetic field induction vector (see Figure 3).

As a result, the output of the summing amplifier 19 forms a doubled, in comparison with the prototype, constant voltage:

This allowed, at the same output voltage as the prototype, to halve the gain of the selective amplifier from 5000 to 2500. Simultaneously with the doubling of the output voltage, which follows from formula (1), the parasitic bias voltages that are present in the quadrature voltages Usin and Ucos and have different signs.

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 samples (Δt and Δt + T / 4) on the sinusoids Usin and Ucos is determined by the logic unit 14 based on the condition of the necessary steepness of the output characteristic of the magnetometer and the equality of the samples of quadrature voltages Usin and Ucos.

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 introduction into the magnetometer circuit of three devices 16, 17, 18 of sample-storage of quadrature voltages and three summing amplifiers 19, 20, 21 made it possible to compensate for stray bias voltages and halve the gain of the selective amplifier. It is especially important that as the gain of the selective amplifier decreases, the stability of the entire measuring circuit of the magnetometer increases.

The elimination of the measurement error caused by the stray bias voltage, significantly improved the accuracy of measuring stresses proportional to the components of the magnetic field induction vector.

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.

The electronic simulation of the device circuit in the environment of the OrCAD 16.3 package is performed. The simulation results indicate the achievement of the task. ISS OJSC intends to use this technical solution on standard products.

Claims (1)

A digital fluxgate magnetometer containing a master oscillator, the output of which is connected to the input of the logic control unit, the first output of which is connected to the input of the sine wave shaper, the output of which is connected to the first inputs of three flux gates, the outputs of which are connected to the inputs of three selective amplifiers, the first outputs of which are connected to the first the inputs of three sampling-storage devices, the first outputs of which are connected to the second inputs of the three flux gates, and the second inputs are connected to the second output of the logical control unit phenomena, the third output of which is connected to the second inputs of analog-to-digital converters, characterized in that three summing amplifiers and three quadrature voltage sampling and storage devices are introduced into it, the first inputs of which are connected to the fourth output of the logic control unit, the second inputs are connected to the second outputs selective amplifiers, and the outputs are connected to the second inputs of summing amplifiers, the outputs of which are connected to the first inputs of analog-to-digital converters, and the first inputs are connected to the second output outputs of storage retrieval devices.

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