RU2723153C1 - Method of controlling magnetic field conversion characteristic by ferroprobe - Google Patents

Abstract

FIELD: measuring equipment.

SUBSTANCE: invention relates to measuring equipment. Essence of the invention consists in the fact that increase of informativity is provided by control of ferroprobe zero offset by measurement of voltage amplitude of the second harmonic of the output electromotive force of the ferroprobe placed in the ferromagnetic screen.

EFFECT: high information value of determining control parameters of the characteristic of converting a magnetic field (MF) to a ferroprobe.

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Description

Application area

The method is intended for production control of the conversion characteristics of a projection of the Earth’s magnetic field (MP) vector projection by a flux gate when the measured magnetic field strength is much less than the saturation magnetic field intensity of the flux-gate core [1]. The amplitude of the second harmonic voltage in the EMF (electromotive force) of the signal winding of the flux gate is considered as an information parameter.

State of the art

A known method of controlling the characteristics of a flux gate [2], which consists in coaxially installing two magnets at a distance of 40 cm, between which a flux gate is coaxially mounted. The probe of the reference magnetometer is installed in close proximity to the controlled flux-gate. The readings of the reference magnetometer are monitored and the magnets are moved to obtain a zero value of induction according to the readings of the reference magnetometer. They supply power to the field winding of a controlled flux-gate. One magnet is moved closer to the controlled flux gate until the reference magnetometer reads equal to 70 μT. A voltmeter controls the average value of the EMF of the signal gate fluxgate. Compare the measured value with the value specified in the documentation of 200 mV, which should be at least. Measure the signal winding signal frequency. Compare the measured value with the value specified in the documentation. The first magnet is returned to its original position - the zero value of induction according to the readings of the reference magnetometer. Repeat the described procedure with the movement of the second magnet.

The method allows to control the presence of the functioning of the flux gate. The disadvantage of this method is the low information content, which consists in the absence of data on the steepness of the characteristics of the conversion of MP to an electrical signal and the lack of data on the zero shift of the flux gate.

The closest in technical essence is the method described in [3] and representing the control of the conversion characteristics of the magnetometer. This method is selected as a prototype. The method is intended to control the steepness of the conversion characteristics of the projection of the Earth's MP vector on its axis by a magnetometer. In this case, the magnetometer with a flux gate as an MP sensor is made according to a block diagram with negative feedback (a method of compensating an MP in the core of a flux gate). The essence of the method lies in the fact that in the normal (working) mode of operation of the magnetometer measure the value of parameter P ₁ external MP. In the control mode, the conversion characteristics to the winding (for example, signal) of the flux gate in addition to the compensation current MP provide a normalized test direct current i _k = i _{k1 of the} same polarity, measure the parameter P ₂ MP, change the normalized test direct current to i _k = i _k2 ( change the direction of the current), calculate the increment of the test DC current Δi _k = i _k1 - i _k2 , measure the parameter P ₃ MP. The difference in the control measurements of the parameter ΔP (Δi _k ) = P ₂ -P ₃ MP is calculated. The steepness of the magnetic field transformation of the magnetometer is calculated in the form of the ratio S = ΔP (Δi _k ) / Δi _k , where the information part of the prototype calculation is used in a generalized form - the dependence of the steepness of the characteristic on the argument Δi _k .

The method for its original purpose is intended to control the steepness of the conversion of the magnetometer. In production conditions with a constant value of the conversion coefficient of the electronic part of the magnetometer, the method provides control of the steepness of the conversion of various flux gates under normal climatic conditions. For example, in the workplace of monitoring fluxgates, the same unit of the electronic part of the magnetometer is used, made on a modern element base with sufficient ADC (analog-to-digital converter), PAP (digital-to-analog converter) and error of other elements up to 0.1%, which is significant fewer errors in flux-gates determined by technological reasons for production and material properties.

The disadvantage of the method of controlling the characteristics of the conversion of the magnetic field by a flux gate is the lack of information, which consists in the absence of information about the zero offset of the flux gate. In addition, the method does not allow for temperature production tests in terms of the stability of the characteristics of a particular flux-gate by MP conversion due to compensation of its temperature changes in a magnetometer, organized by the method of MP compensation in a flux-gate core.

The purpose of the invention

The aim of the invention is to increase information content and expand functionality.

An increase in information content is provided by controlling the zero-shift of the flux gate by measuring the amplitude of the second harmonic voltage of the output EMF of the flux gate located in the ferromagnetic screen. The expansion of functionality, for example, temperature testing of a flux gate, is ensured by monitoring its characteristics directly from direct measurements of the main parameter - the voltage amplitude of the second harmonic of the output EMF.

SUMMARY OF THE INVENTION

The method involves the use of, for example, a selective voltmeter for measuring the amplitude of the second harmonic voltage E _m in the EMF of the flux-gate, a highly stable excitation generator of the flux-gate, and an adjustable test direct current source in a manufacturing workplace for controlling the parameters of a flux gate. It is also possible to use the electronic part of the magnetometer (organized using a microcontroller using the method of compensating the magnetic field in the core of the flux gate) with a corresponding change in its software. In the zone of the placement of the flux gate, there should be no sources of magnetic field, ferromagnetic masses. In the presence of variable industrial interference in the MP, the results of the proposed method can be subjected to statistical processing.

In the core of the fluxgate create a field of excitation. A flux gate is placed horizontally in a room with the Earth's magnetic field. The value of the test direct current i _k in the winding of the flux gate is set equal to i _k = i _k1 = 0. Rotate the flux gate in a horizontal plane (around the vertical axis) to obtain the maximum value of the measured amplitude E _m = E _max voltage of the second harmonic of the output EMF of the flux gate. The winding (e.g., signal) supplied ferroprobe test DC current i _{to the} E ≠ 0. By controlling the voltage amplitude _m of the second harmonic output emf ferroprobe, establish the amount of DC test _for i = i _k2, wherein the voltage amplitude value of the second harmonic in the output emf fluxgate E _m (i _k2 ) = 0. Note that the dependence E _m (i _k ) has a nonlinearity, the value of which is determined by the ratio of the intensity H _k (i _k ) and the saturation intensity H _{s of the} core material of the flux gate. Next, place the flux gate in the ferromagnetic screen. Accordingly, in the core of the fluxgate there is no component of the external magnetic field strength. In the winding of a flux gate, the test direct current is reduced to i _k = 0. In this case, the output signal E _m = E _{m_cm} in the form of the amplitude of the second harmonic voltage in the EMF of the flux gate will be determined, in particular, by the production asymmetry of the flux gate - “zero offset”. The measured value of E _{m_cm is} compared with the first manufacturing tolerance for a zero offset: E _m1 <E _{m_cm} <E _m2 , where E _m1 , E _m2 are the boundaries of permissible deviations. Next, calculate the slope S of the conversion characteristics of the MP by a flux gate according to the formula S = E _max / i _k2 . The calculated value is compared with the second manufacturing tolerance — the steepness of the conversion characteristics of the MP by a flux gate: S ₁ <⏐S⏐ <S ₂ , where S ₁ , S ₂ are the boundaries of permissible deviations in positive values. The test direct current i _k = i _k2 can have any sign depending on the orientation of the axis of the flux gate relative to the Earth’s magnetic field vector. For the sake of unambiguity, the control of the correspondence of the steepness to the manufacturing tolerance is performed by the absolute value ⏐S⏐. If the results of the comparison are consistent with the manufacturing tolerances, the flux-gate is transferred to operation.

The physical foundations of the nonlinearity of the dependence E _m (i _k ) are similar to the well-known reasons leading to nonlinearity in the measurement of the MP parameter by a magnetometer by the direct conversion method (direct measurement of the amplitude E _{m of a} flux gate). At H _к (i _к0 ) / H _s ≤0.1, the non-linearity value in the calculation using arctg of the approximation of the hysteresis loop of the core material of the flux gate is ≤3%. This difference from linearity does not prevent the sorting of flux-gates during their manufacture with a tolerance of ΔS = ± 15 ... 30% or more. The difference between S and the flux gate to the flux gate during their manufacture within the tolerance ΔS is eliminated at the stage of adjustment of the magnetometer, for example, using precision control methods [4]. If necessary, the considered nonlinearity of the characteristics of the flux gate during their sorting can be taken into account as a systematic error.

Technical result

The application of the method in a production environment increases the information content of determining the control parameters of the conversion characteristics of the MP by a flux gate. At the same time, it is possible to control the considered parameters of the flux gate without the use of expensive and difficult to operate standard MP standard or Helmholtz rings, which greatly simplifies the control procedure. Another positive feature of the method is the possibility of analyzing (controlling) the temperature error directly of the MP conversion characteristics by a flux probe, for example, when a flux probe is heated with a hot air gun.

Sources of information

1. Afanasyev Yu. Ferrozones. L .: Energoatomizdat, 1969.

2. FERROSENDAL SENSOR DF-002 Instructions for monitoring the parameters of OTHER. 411511.002 I22, St. Petersburg, 2018.

3. Fluxgate magnetometer. Copyright certificate No. 930176, IPC G01R 33/02 (1982/05).

4. Analog magnetometer MA-5 Specifications KMIIV.411172.004 TU, Ramenskoye, 2000

Claims (1)

A method for controlling the magnetic field conversion characteristics of a flux gate consists in generating an excitation field strength in the core of the flux gate, measuring the magnetic field parameter P ₁ , applying a test direct current i _k = i _k1 to the flux gate, measuring the magnetic field parameter P ₂ , changing test direct current up to i _k = i _k2 , measure the magnetic field parameter P ₃ , calculate the increment of the test direct current Δi _k = i _k1 - i _k2 , calculate the increment of the magnetic field parameter ΔP (Δi _k ) = P ₂ -P ₃ , calculate the slope S characteristics of the transformation of the magnetic field in the form of the ratio S = ΔP (Δi _k ) / Δi _k , characterized in that in order to increase the information content and expand the functionality, the parameter P _{j of the} magnetic field with j = 1, 2, 3 is measured at the terminals of the signal winding of the flux gate in units of the amplitude E _m , the second-harmonic voltage of the output EMF of the fluxgate, before measuring the magnetic field parameter, the fluxgate is placed horizontally in a room with gnitnym earth's field, set the amount of test DC i _k1 = 0, storing the value of i _k1 to calculate Δi _to rotate flux gate in a horizontal plane to obtain the maximum value of the measured parameter P ₂ = P _max = E _max of the magnetic field, and then change the test DC i _k2 , controlling the parameter P ₃ = E _{m of the} magnetic field to obtain the value E _m = 0, remember the value i _k2 (E _m = 0) for calculating Δi _k , set the current value i _k = 0, measure the value of the parameter P ₁ = E _{m_cm of the} magnetic field is carried out with a fluxgate, which is placed in the ferromagnetic screen, the value of E _{m_cm is compared} with the first manufacturing tolerance, the value of ⏐S⏐ is compared with the second manufacturing tolerance, if the results of comparison are consistent with the manufacturing tolerances, the fluxgate is transferred to operation.