RU2632265C2 - Device for operational treatment of magnetite ores - Google Patents

Abstract

FIELD: measuring equipment.

SUBSTANCE: invention can be used to measure the magnetic susceptibility of magnetite ores during the operative testing of the walls of mine openings, and also to assess the quality of the ore mass in bulks, jubilee trucks and dump trucks. The device includes a sinusoidal voltage generator loaded on a generator coil, two compensating and receiving coils located at different distances from the generator coil in one plane perpendicular to the surface of the investigated medium, two amplifying and converting units, a calculating unit, an ultrasonic sensor and a logger. In parallel to the compensating and receiving coils, three capacitors are installed, forming three oscillatory circuits with the same resonance frequency.

EFFECT: increase of sensitivity and accuracy of the device for operative testing of magnetite ores in the non-contact measurement of magnetic susceptibility with increasing the permissible range of distances from the probe to the surface of the investigated medium.

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Description

Device for operational testing of magnetite ores

The invention relates to the field of non-destructive testing and can be used to measure the magnetic susceptibility of magnetite ores during operational testing of the walls of mine workings, as well as to assess the quality of the ore mass in bulk, trolleys and dump trucks.

A well-known RIMV-3 mine measuring magnetic effect medium is designed for geophysical studies and assessing the quality of magnetite ores when measuring in wells, on the walls of mine workings, ore mass in bulk, trolleys and dump trucks, as well as in the study of powder samples (see. Catalog of geophysical equipment . - M.: Nedra, 2005. The list of geophysical equipment produced by GNPP "Geological exploration. Ground-based equipment for magnetic research). The RIMV-3 device excites an electromagnetic field and measures its intensity using an induction converter, the generator coil of which is connected to a low-frequency voltage source, and the measuring coil is connected to a secondary electronic converter. The operation of this device is based on the excitation of an electromagnetic field in the volume of the space under study and the measurement of the relative change in the magnetic component of the intensity of this field depending on the change in the magnetic properties of the medium under study. Under the influence of an electromagnetic field, an EMF is induced in the measuring coil, the value of which is maximum when the induction transducer (probe) is located in a non-magnetic medium (in air) and decreases with increasing magnetic susceptibility of the rock or ore. The increment of the EMF of the measuring coil of the probe depends on the quantitative content of the magnetic component in the controlled medium. For testing in bulk rock and dump trucks with iron ore, an induction probe is used with coaxially located generator and receiving coils, which are about 0.5 m apart from each other.

The disadvantage of the RIMV-3 device is its low accuracy and low sensitivity of measurements, due to the dependence of its readings on surface irregularities and the distance to the medium under study.

The closest technical solution to the claimed invention is a device for testing magnetite ores. As part of this device, a probe is used that contains a generator, receiver and two compensation coils located at different distances from the generator coil. The axes of all coils are parallel to each other and are located in the same plane perpendicular to the surface of the medium under study. The device also uses a sinusoidal voltage generator connected to the generator coil, two amplifier-converter blocks, the largest signal extraction unit, and a recorder. The receiver coil of the probe is connected between the common bus and the combined terminals of two compensation coils, the free terminals of which are connected respectively to the inputs of two amplifier-converter blocks, and the outputs of these blocks are connected to the first and second inputs of the block for extracting a larger signal, the output of which is connected to a recorder recording the results control (see patent No. 20066888, IPC G01V 3/165, G01V 3/18, publ. 1994).

The disadvantages of this device are the low sensitivity due to a weak change in the amplitude of the signals at the receiving and compensation windings when the magnetic susceptibility of the medium under study changes, as well as a limited range of tolerances of the probe ± Δh from the optimal distance h _opt to the surface of the medium under study.

In particular, when a sinusoidal voltage with a frequency of 1 kHz and an amplitude of 50 V is applied to the generator coil, the EMF value at the receiving and compensation coils in the air is no more than 20.5 mV, i.e. approximately 2400 times less with the same number of turns in the generator and receiver coils. Moreover, the range of the measured voltage does not exceed several millivolts, which practically limits the accuracy of the magnetic susceptibility control due to the influence of instrumental errors of the device and the influence of external noise. In addition, the measurement accuracy is affected by the methodological error caused by the wave-like dependence of the sensitivity of the device on the distance between the probe and the medium under study. In particular, when using a probe with a length l _gn = 100 cm and errors from an uneven surface of the medium and a change in height h between the probe and the test medium of ± 5%, it is necessary to maintain the optimal distance from the probe to the surface of the medium h _opt = 77 cm with an allowable deviation Δh not more than ± 25 cm.

The objective of the invention is to provide a device for the operational testing of magnetite ores, which allows to increase the sensitivity and accuracy of the device for measuring magnetic susceptibility with non-contact operational testing of magnetite ores with an increase in the allowable range of distances from the probe to the surface of the medium under study.

The problem is solved in that in a device for the operational testing of magnetite ores containing a sinusoidal voltage generator connected to a generator coil, a receiving coil installed between a common bus and the combined terminals of two compensation coils located between the generator and receiving coils in one plane perpendicular to the surface of the investigated environment, the second conclusions of the compensation coils are connected to the inputs of the first and second amplification-conversion blocks containing therefore coupled AC amplifier, synchronous detector and the DC amplifier, and a recorder for outputting test results, further administered three capacitors connected respectively in parallel and receiving the two compensation coils, ultrasonic transducer and computing unit. The outputs of the first and second amplification-conversion blocks are connected to the first and second inputs of the computing unit, the third input of which is connected to the output of the ultrasonic sensor, and the output of the computing unit is connected to the recorder.

The technical result consists in increasing the sensitivity and accuracy of the device for the operational testing of magnetite ores with non-contact measurement of magnetic susceptibility with an increase in the allowable range of distances from the probe to the surface of the medium under study.

The structural diagram of the proposed device is shown in the drawing.

A device for operational testing of magnetite ores contains a sinusoidal voltage generator 1 to which a generator coil 2 is connected, a first compensation coil 3 with a first capacitor 4, a second compensation coil 5 with a second capacitor 6 and a receiving coil 7 with a third capacitor 8. Structurally, all coils are placed in a probe (not shown in the figure) at different distances from the generator coil parallel to each other in the same plane perpendicular to the surface of the medium under study. One terminal of the winding of the receiving coil 7 is connected to a common bus 9, and the other is connected to the combined first terminals of the first compensation coil 3 and the second compensation coil 5, which are turned on in the opposite direction. The first 10 and second 11 amplification-conversion blocks are made according to the same type and contain AC amplifiers 12 and 13, synchronous detectors 14 and 15 and DC amplifiers 16 and 17. The control inputs of synchronous detectors 14 and 15 are connected to the generator 1. The second terminals of the compensation coils 3 and 5 are connected respectively to the inputs of AC amplifiers 13 and 12, the outputs of which through synchronous detectors 14 and 15 and DC amplifiers 16 and 17 are connected to the first and second inputs of computing unit 18. Ultrasound The sensor 19 is connected to the third input of the computing unit 18, the output of which is connected to a recorder 20, which is used to output the results of monitoring the magnetic susceptibility of the test medium.

A device for operational testing of magnetite ores works as follows.

When an alternating current flows from the generator 1 of a sinusoidal voltage through the turns of the generator coil 2, an alternating electromagnetic field is created in the surrounding space. Structurally, the receiving coil 7 is mounted in the probe at a fixed distance from _rn l transmitter coil 2. The first bucking coil 3 is located at a distance 0,2l _rn, and the second bucking coil 5 - 0,8l distance _r from the transmitter coil 2. The air in the absence of in an electromagnetic environment, this electromagnetic field induces, in two counter-activated compensation coils 3 and 5, equal in amplitude and opposite in phase EMF Ε ₁ and E ₂ .

When the probe is placed with generator 2, two compensation 3 and 5 and 7 receiving coils above the test medium, it is magnetized by the alternating electromagnetic field of the generator coil 2. The emerging secondary magnetic field induces in the receiving 7 and compensation 3 and 5 coils EMFs of different amplitudes. As a result, at the input of amplifier 13, a differential EMF ΔΕ _{1 of the} output signals of the receiving 7 and the first compensation 3 coils appears, and at the input of the amplifier 12, a differential EMF ΔE _{2 of the} output signals of the receiving 7 and the second compensation 5 coils appears. After amplification of these differential emfs ΔE ₁ and ΔE _{2 by} amplifiers 13, 12 and their rectification by synchronous detectors 15 and 14, constant or slowly changing signals are amplified by amplifiers 17 and 16 and fed to the first two inputs of computing unit 18 based on a microcontroller containing a commutator of input signals and An analog-to-digital converter for receiving and processing control results in digital form (not shown in the figure). The third input of the computing unit 18 receives pulses from an ultrasonic sensor 19, which determines the distance h from the probe to the test medium to correct the conversion results, which are displayed on the recorder 20. The magnetic susceptibility of the medium is determined by the value of the result recorded in digital form.

The operation of the device is based on the following theoretical provisions (see patent No. 20066888, IPC G01V 3/165, G01V 3/18, publ. 1994).

When the probe is placed above the flat surface of the medium under study, the difference EMF ΔE ₁ = E ₀ G _1χms and _{ΔE 2} = E ₀ G ₂ χ _ms depend on the product of the EMF induced in the air E ₀ , geometric factors of the probe G ₁ , G ₂ n magnetic susceptibility χ _ms = Ι / Η, proportional to its magnetization I from the intensity Η of the electromagnetic field. The values of the geometric factors of the probe G ₁ , G ₂ depend on the location of the compensation coils relative to the generator coil and vary over a wide range depending on the ratio of the distance to the test medium and the probe length h / l _gp .

The differential EMF ΔE ₁ , ΔE _{2 are} amplified and detected by the amplifier-conversion blocks 11, 10 with the conversion factors K ₁₁ , K ₁₀ , so the voltage at the two inputs of the computing unit 18 is

where to obtain the same maximum values of these voltages ΔU _1max = ΔU _{2 max} it is necessary to fulfill the condition K ₁₁ G _1max = K ₁₀ G _2max , which when using amplification-conversion blocks 11 and 10 with equal conversion factors K ₁₁ = K ₁₀ is reduced to ensure the same the maximum values of the geometric factors of the probe G _1max = G _2max . Performing such equality is possible to provide a decrease in 4 times the number of turns in the first compensating coil 3 relative to the number of turns in the second compensating coil 5 (when they are placed at distances 0,2l 0,8l _rn and _rn from the transmitter coil).

The ultrasonic sensor 19 determines the distance h from the probe to the test medium and feeds pulses of different durations to the third input of the computing unit 18, which automatically changes the conversion coefficient of the signals ΔU _1K and ΔU _2K from the amplifiers 17 and 16, compares them and selects the largest of them , the magnitude of which is calculated magnetic susceptibility of the investigated medium for its output to the recorder 20.

In the proposed device circuit, the first compensation coil 3 with a capacitor 4, the second compensation coil 5 with a capacitor 6 and the receiving coil 7 with a capacitor 8 form three parallel oscillatory circuits. To increase sensitivity, the resonant frequency f _{P of} these circuits, taking into account the inductances L ₃ , L ₅ , L _{7 of} coils 3, 5, 7 and capacitances C ₄ , C _6, C _{8 of} capacitors 4, 6 and 8, must be set equal to the frequency of the sinusoidal voltage generator 1 by condition (see Izyumov N.M., Linde D.P. Fundamentals of Radio Engineering. - M.: Radio and Communications, 1983. - 376 p.):

where L ₃ is the inductance of the first compensation coil (GN);

C ₄ is the capacity of the first capacitor (F);

L ₅ - inductance of the second compensation coil (GN);

C ₆ is the capacity of the second capacitor (F);

L ₇ - inductance of the receiving coil (GN);

C ₈ is the capacity of the third capacitor (F).

The resistance of such oscillating circuits at the resonant frequency is ten times higher than the inductive resistance of two compensation and receiving coils, which can significantly increase the amplitude of the signals on these circuits with a change in the magnetic susceptibility of the medium and reduce the instrumental conversion error.

The increase in the amplitude of the signals at two compensation and receiving circuits also allows the use of amplifiers 12 and 13 with small amplification factors and to form voltages per unit volt at the inputs of synchronous detectors 14 and 15. This reduces the influence of instrumental errors of synchronous detectors 14, 15 and temperature drift of DC amplifiers 16 and 17 on the conversion accuracy.

Practically due to the increase in the amplitude of the signals at the outputs of the compensation and receiving oscillatory circuits, the relative influence of external interference and interference is additionally weakened and the random conversion error is reduced with a relatively small complication of the device circuit.

To assess the effectiveness of the proposed technical solution, a PC device was simulated in the Electronics Workbench Pro program, which established the following:

1) applied to the coil generating a sinusoidal voltage with an amplitude of ₁ U = 10 V and the frequency ƒ ₁ = 1 kHz, the inductance change of one of the compensation coils 10% relative to the initial value of L = 0.1 Gn _nach gives rise to a difference voltage ΔU ≈ ₁ 2.28 mV;

2) when capacitors with the same capacitance C = 200 nF are connected parallel to the compensation coils, a change in the inductance of one of them by ± 10% changes the difference voltage by ΔU _1K ≈80 mV at the loop resonance frequency ƒ _p = 1 kHz at input impedances of AC amplifiers 12 and 13 constituting 10 kΩ, i.e. the amplitude of the measured signal increases approximately K = ΔU _1K / ΔU ₁ = 80.2 / 2.28≈35 times.

Therefore, the use of the resonant mode of operation of the receiving and compensation loops makes it possible to increase the sensitivity of the device to changes in the electromagnetic field almost tenfold and makes it possible, for example, to increase the sensitivity of the device by more than 30 times.

The device calibration process is performed in the following order.

The probe with generator, two compensation and receiving coils placed on it is placed horizontally at a minimum distance above a large metal sheet, for example 2 × 1.2 m. Then the probe gradually rises to the maximum distance from this sheet. In the process of its lifting, the distance to the sheet is measured discretely through each 1 cm by an ultrasonic sensor 19, which generates pulses whose duration is directly proportional to the distance to the metal sheet. The width of each pulse coming from the ultrasonic sensor 19 is measured in digital form by the microcontroller of the computing unit 18. The resulting digital code Ν _{τ is} used as the cell address of the random access memory included in the microcontroller. In this case, the output voltages ΔU _1K and ΔU _{2K of the} amplifier-converter blocks 11 and 10 are also encoded by an analog-to-digital converter, a comparison of the obtained codes ΔΝ ₁ and ΔN ₂ and recording of the largest of them at the address Ν _T , determined by the duration of the output pulse of the ultrasonic sensor 19.

After completion of the process of raising the probe from minimum to maximum distance from the metal sheet, linearization of the characteristics of the device is performed. In this case, the microcontroller of the computing unit 18 determines the maximum value of the code ΔN _max corresponding to the optimal distance h _om to the metal sheet, which is taken as the reference value, relative to which the device readings should be adjusted. Then, the ratios of the codes recorded in the cells of the random access memory are calculated to the maximum code and correction factors K _k = ΔNmax / ΔN _{k are} determined. After that, each ΔNk value previously recorded in the random access memory cell is multiplied by the correction coefficient K _k calculated for it and copied to the memory of the permanent storage device at the same address corresponding to the distance of the probe to the metal sheet measured by the ultrasonic sensor 19.

As a result of such operations, the computing unit 18 will output to the recorder 20 the values of magnetic susceptibility, practically independent of changes in the distance to the medium being studied. Moreover, when assessing the magnetic properties of various rocks, it is necessary to take into account their specific parameters, i.e. multiply the results by a certain constant coefficient, which is determined experimentally and can be entered into the microcontroller during the final setup of the device.

The use of an additional ultrasonic sensor with such a signal processing algorithm in the computing unit eliminates the influence of the distance between the probe and the surface of the medium on the geometric factors of the probe G ₁ , G ₂ and linearizes the conversion characteristic of the device.

It was experimentally established that the use of an ultrasonic sensor for correction of readings allows it to be used when measuring the magnetic susceptibility of the medium with an error of less than 1.5% in an extended range of distances h / l _rn = 0.4 - 1.5, which is 1.5 times the range measuring a prototype also having lower conversion accuracy.

Thus, the proposed device provides high sensitivity and accuracy of non-contact measurement of the magnetic susceptibility of magnetite ores through the use of the resonant mode of the receiving and compensation loops with an increase in the range of distances from the probe to the surface of the medium under study due to the use of an ultrasonic sensor and a computing unit with automatic signal processing for correction of the distance to the investigated medium.

The device can be implemented on a modern elemental base when reaching a specified destination. For example, you can use an HC-SR04 ultrasonic distance measuring sensor with a measuring range of 2-400 cm and a resolution of 0.3 cm with a supply voltage of 5 V (see info@sensoren.ru, Arduino Library For Ultrasonic Ranging Module HC-SR04: documentation on HC-SR04), and as a computing unit - a microcontroller type TMP90С840Р.

Claims (1)

A device for operational testing of magnetite ores, containing a recorder for outputting control results, a sinusoidal voltage generator connected to a probe containing a generator, receiving and two compensation coils located at different distances from the generator coil parallel to each other in one plane perpendicular to the surface of the medium under study, the second the conclusions of the compensation coils are connected to the inputs of the first and second amplification-conversion blocks, each of which contains after They are connected to an alternating voltage amplifier, a synchronous detector connected to a generator, and a DC amplifier, characterized in that it additionally contains three capacitors connected in parallel with the receiver and two compensation coils, an ultrasonic sensor and a computing unit, the outputs of the first and second amplifying -transformation blocks are connected to the first and second inputs of the computing unit, the third input of which is connected to the output of the ultrasonic sensor, and the output to numeral unit is connected to the logger.

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