RU2732473C1 - Frequency-measuring device based on fluxgate transmitter - Google Patents

Abstract

FIELD: measuring equipment.SUBSTANCE: invention relates to measurement of magnetic field parameters based on fluxgate transmitter. Frequency-measuring device based on fluxgate transmitter, designed to measure magnetic field strength, consists of a flux gate fed by a generator, wherein supply of the flux gate is carried out by a generator of modulated rectangular voltage pulses, wherein modulation frequency corresponds to rated frequency of flux gate, and the filling frequency generated by the generator, which feedback circuit includes the flux gate winding output, depends on the measured magnetic field intensity, wherein the frequency readings of the generator are calibrated in units of magnetic field intensity.EFFECT: high sensitivity of the flux gate, as well as high efficiency of using generation frequency as a useful signal.1 cl, 3 dwg

Description

The technical field to which the invention relates

The invention relates to the field of techniques for measuring magnetic field parameters based on a fluxgate converter and can be used in control and monitoring systems in which magnetic field parameters are used as diagnostic parameters.

State of the art

In the known devices for measuring the magnetic field strength, various sensitive elements are used that convert the magnitude of the strength into an electrical quantity - current or voltage. Thus, current or voltage is a useful signal carrying information about the magnitude of the magnetic field strength.

The use of the generation frequency as a useful signal is preferable because modern digital frequency meters provide the highest metrological characteristics (accuracy and resolution) among all measuring instruments; they operate in a wide range of measured frequencies, are fast, reliable and easy to use.

The possibility of converting the magnetic field to the generation frequency exists, and this conversion can be provided by various devices using different physical principles.

Known converter (RU 2035808 C1) of electric voltage to frequency, which allows measurements of physical quantities by converting the current or voltage of the sensor into frequency. The device is expensive, it is a complex multilayer semiconductor structure, for the manufacture of which special technological equipment is required.

Known devices based on nuclear magnetic resonance, containing a broadband amplifier, in the positive feedback of which is included a magnetically tunable resonant element. To reduce the relative instability of generation, for example, in a similar device (SU 292202 A1), a filter selector is used as a resonant element, in which a working substance is used with level splitting in a zero magnetic field (for example, rutile, barium ferrite, ruby). These are complex and expensive devices related to the field of quantum electronics.

From the works of Yu.V. Afanasyev It is known that in measuring devices based on fluxgate converters, the measured magnetic field affects the frequency of the generator feeding the excitation winding of the fluxgate. Thus, in fluxgate devices it is possible to convert the magnetic field into the generation frequency.

Known devices based on fluxgate converters, in which the excitation winding of the fluxgate is powered from a generator made on logical elements NOT or AND NOT (for example, RU 2645840). In this case, the excitation winding is actually an element of the generator, and its frequency naturally depends on the magnitude of the measured magnetic field strength. However, it is impractical to use the generator frequency as a useful signal. This is due to the fact that, firstly, the magnitude of the frequency change under the action of the field is insufficient to judge the magnitude of the field from it, and, secondly, this magnitude of the change should not be large, since it is undesirable to go far from the operating frequency, which indicated in the passport for the ferroprobe.

The closest to the claimed technical solution in terms of technical essence is the measuring device RU 2690729, in which the excitation winding of the flux gate is powered by modulated rectangular pulses. In this case, the measured magnetic field affects the filling frequency, while the frequency of the modulating voltage remains constant and corresponds to the passport frequency of the flux gate. This device is taken as a prototype of the invention.

The disadvantage of the prototype is a narrow frequency range depending on changes in the measured magnetic field strength. For this reason, the prototype does not imply the use of frequency as a useful signal, and the measuring device is a pointer microammeter.

Disclosure of invention

The objective of the invention is to create a device for measuring the magnetic field strength based on a flux-gate transducer, which makes it possible to effectively use the generation frequency as a useful signal.

The technical result is the creation of a frequency-measuring device based on a flux-gate converter with improved metrological parameters. The digital frequency meter becomes the measuring instrument.

The technical result is achieved by powering the fluxgate excitation winding with modulated rectangular voltage pulses. With such a power supply, only the filling frequency depends on the magnitude of the measured magnetic field strength. The magnitude of the change in the filling frequency is not critical for the flux gate and can be expanded, since the rated frequency, determined by the properties of the core, corresponds to the frequency of the modulating pulses and remains constant.

где: Δƒ - величина изменения частоты генератора; ΔН - величина изменения напряженности измеряемого магнитного поля, вызвавшего это изменение частоты Δƒ) достигается нестандартным использованием освободившейся выходной обмотки феррозонда в качестве элемента генератора импульсов заполнения. Увеличение информативности частоты заполнения позволяет эффективно использовать частоту в качестве полезного сигнала.Expansion of the range of variation of the filling frequency or, in other words, an increase in the informative value of the frequency (which is defined as the ratio

where: Δƒ - the amount of change in the generator frequency; ΔH is the magnitude of the change in the strength of the measured magnetic field that caused this change in frequency Δƒ) is achieved by non-standard use of the vacated output winding of the flux gate as an element of the filling pulse generator. Increasing the information content of the filling frequency allows you to effectively use the frequency as a useful signal.

Brief Description of Drawings

FIG. 1. Differential flux gate with windings:

L1 - excitation winding, consisting of two oppositely wound halves L1 'and L1' ';

L2 - output winding;

L3 - compensation winding;

Н0 - measured (external) magnetic field;

H - magnetic fields created by each half of the excitation winding L1 and balancing each other in the absence of an external magnetic field H0.

FIG. 2. Scheme of power supply of the fluxgate excitation winding, which is based on two generators (generator 1 and generator 2).

FIG. 3. Timing diagrams of voltages and explanations to them.

Implementation of the invention

A standard differential flux gate is used as a sensitive element (Fig. 1).

The inventive measuring device is represented by the circuit for feeding the excitation winding of the flux gate, which contains the following components (Fig. 2).

1. Excitation winding of the flux gate, consisting of two oppositely wound halves L1 'and L1' '.

2. Connecting capacitors C3, C4, through which the fluxgate excitation winding is powered. The capacitances of the capacitors are determined from the condition of ensuring the resonance of the voltages in the series circuit "connecting capacitors - excitation winding of the flux gate" at the frequency of the modulating voltage.

3. Generator 1 (made on three elements 2I-NOT DD1.1-DD1.3 of the 564LA7 microcircuit) is a generator of unipolar modulating rectangular voltage pulses, the frequency of which is adjusted by means of a resistor R1 to the operating (passport) frequency specified in the documentation for the flux gate.

4. Generator 2 (made on three elements 2I-NOT DD2.1-DD2.3 of the 564LA7 microcircuit) is a generator of unipolar rectangular pulses, the frequency of which is orders of magnitude higher than the passport frequency of the flux gate and is set using the resistor R2. Generator 2 generates voltage pulses, which fill the voltage pulses of generator 1. The output winding of the flux gate is connected to the feedback circuit of generator 2. The pulse frequency of generator 2 (filling frequency) depends on the measured magnetic field strength and is used as a useful signal.

5. D-flip-flop, made on three elements 2I-NOT DD2.2, DD2.3, DD2.4 of the 564LA7 microcircuit (while elements DD2.2 and DD2.3 are simultaneously elements of generator 2).

Timing diagrams of voltages (without taking into account distortions) and explanations for the diagrams are shown in Fig. 3.

The entire circuit shown in FIG. 2 is made on two 564LA7 2I-NOT microcircuits.

A fundamental feature of the proposed solution is the frequency deviation of voltage pulses generated by generator 2 and filling the modulating pulses of generator 1, depending on the amplitude and direction of the measured magnetic field strength vector. The inclusion of the output winding of the flux gate in the open circuit of the generator 2 between the output of the element DD2.1 and the input of the element DD2.2 (Fig. 2) allows to significantly increase the frequency deviation when the strength of the measured magnetic field changes. An increase in the frequency deviation, determined by the number of turns in the output winding of the fluxgate, increases the sensitivity and provides the device's ability to distinguish frequency changes in the magnetic field by a magnitude of the order of

The filling frequency dependent on the measured voltage is recorded by a frequency meter, which can be connected directly to one of the outputs of the D-flip-flop (output of element DD2.3 or element DD2.4) or to the output of element DD2.2 (Fig. 2).

The proposed device has been tested on a prototype. The experiments were carried out with a differential flux gate (Fig. 1), consisting of two permalloy cores and having a passport frequency of 2 kHz, which is set by generator 1. The number of turns of each half of the excitation winding L1 'and L1' '- 200 each, wire 0.3 mm in diameter ... One-layer winding coil to coil. Above two cores with windings L1 'and L1' 'the output winding L2 is wound, the number of turns is 2000, the diameter is 0.1 mm. Winding multilayer coil to coil. The compensation winding is located on top of the first two, diameter 0.1 mm, the number of turns 500. The use of the compensation winding is standard.

The capacity of the connecting capacitors C3 and C4 at each output of the D-flip-flop is 0.68 μF. The inductance of the excitation winding of the used flux gate is 0.01 G.

The frequency of generator 2 is of the order of 20 kHz (in the absence of an external magnetic field).

The experimental studies carried out indicate the effectiveness of the proposed solution. The obtained measuring device is characterized by compactness, low energy consumption, does not contain complex and expensive elements and does not require careful adjustment. Sufficient sensitivity of the device and the convenience of measurement allow it to be used in various control and monitoring devices, in particular, for the online measurement of the cutting force during machining on a metal-cutting machine. Measurements can be performed remotely and there is no need to build the flux gate into a structure containing a magnetic field source.

At the same time, as in the case of using the traditional power supply scheme, preparing the device for operation consists in calibrating the scale of the measuring device (digital frequency meter).

Claims (1)

A frequency measuring device based on a fluxgate converter, designed to measure the magnetic field strength, consisting of a fluxgate fed by a generator, characterized in that, in order to improve metrological parameters by increasing the information content of the frequency, the fluxgate is fed by a generator of modulated rectangular voltage pulses, and the modulation frequency corresponds to the rated frequency of the flux gate (generator 1), and the filling frequency formed by the generator 2, the feedback circuit of which includes the output winding of the flux gate, depends on the magnitude of the measured magnetic field strength, while the frequency readings of the generator 2 measured by the digital frequency meter are calibrated in units of the magnetic field strength.

Images