AU2020100382A4 - A Transient Electromagnetic Transmitting And Receiving Device - Google Patents

Abstract

The present invention provides a transient electromagnetic transmitting and receiving device, consisting of a transmitter, a transmitting coil, a compensating coil and a conversion circuit. The transmitter is connected with the conversion circuit, which is connected with the transmitting coil and the compensating coil respectively at the same time. In this device, the transmitting coil and the compensating coil are of the same size and they overlap together. The reverse connection between the transmitting coil and the compensating coil is realized through the conversion circuit. Under power supply, the transmitter emits bipolar square wave current, and through conversion circuit, the transmitting coil becomes connected while the compensating coil is still open. At the very moment the transmitting coil is shutted down, the compensating coil is connected to the transmitting coil, so that the current in the transmitting wire frame which is not completely disappeared flows in the compensating coil in the opposite direction. The current flows in the compensating coil can counteract the influence of the primary field in the transmitting coil and reduce the shallow blind depth of TEM detection. 9+ 10 5-7 11_ _8

Description

A TRANSIENT ELECTRONMAGNETIC TRANSMITTING AND RECEIVING DEVICE

TECHNICAL FIELD

The present invention relates to the technical field of geophysical exploration,in particular to a transient electronmagnetic transmitting and receiving device.

BACKGROUND ART

Transient electromagnetic method(TEM) is one of the main methods of geophysical exploration. In recent years, TEM has been widely used in the fields of metal mine exploration, engineering geology, coal mine goaf exploration and so on. It has achieved both economic and social benefits. TEM is a reconnoitre method by sending out a pulse transient magnetic field toward underground using the loop not connecting ground,and then measuring again quadric backsets that is caused by the change of the magnetic field, so as to obtain the electrical information of underground medium. As the transmitter coil is an imperfect conductor, the primary field can not be completely turned off at zero time, which will produce a certain delay, resulting in the oblique step effect in the actual observation data, that is, the so-called ramp effect. Moreover, in engineering pratice,the larger the wire frame and the more turns, the more obvious the turn-off effect will be.In the case of non-ideal turn-off, the performance of the transmitter hardware switch, the response of coil to transient electromagnetic field, the coupling mutual inductance between coils,the displacement current and so on will all affect the tum-off(T/O) time. If the T/O time is neglected, there will be a big error in the apparent resistivity of the first several channels,which will directly affect the inversion result.If the T/O time is not short enough, the shallow geological signal will be included in the turn-off process. Therefore, it is necessary to analyze the change law of the secondary field during the process of turn-off, find out the method to eliminate the influence of primary field, and then get pure secondary field signal for effective inversion results, so as

2020100382 12 Mar 2020 ____________________SPECIFICATION____________________ to explain the underground geological structure. That is to say, the turn-off effect will affect the inversion results. Also, the turn-off effect increases the blind depth of TEM detection, which makes the shallow information unavailable. As the inherent property of the TEM, turn-off effect can not be avoided,otherwise it will lead to distortion of data interpretation. With the application of TEM in shallow engineering fields such as geotechnical engineering and tunnel engineering, how to shorten or even eliminate the turn-off effect and improve the shallow resolution of TEM is an urgent technical problem waiting to be solved.

SUMMARY OF THE INVENTION

To solve the problems existing in the prior art,a transient electromagnetic transmitting and receiving device according to the present invention,as defined in the claims, is provided. The present invention can suppress the influence of the turn-off effect on the correctness of the final measurement result effectively, and improve the resolution of the TEM in the field of shallow engineering.

To achieve the above object, the present invention provides the following scheme: the invention provides a transient electromagnetic transmitting and receiving device, including a transmitter, a conversion circuit, a transmitting coil and a compensating coil. The transmitter is connected with the conversion circuit, and the conversion circuit is connected with the transmitting coil and the compensating coil respectively at the same time.

Preferably, the size of the transmitting coil and the compensating coil are exactly the same and they overlap together. The number of turns of the transmitting coil and the compensating coil is equal, and the number of turns is one or more.

Preferably, the conversion circuit comprises an input terminal and an output terminal. The input terminal comprises a first positive pole and a first negative pole, and the output terminal comprises a second positive pole, a second negative pole,a third negative pole and a third positive pole.

Preferably, the positive pole of the transmitter is connected with the first

2020100382 12 Mar 2020 ____________________SPECIFICATION____________________ positive pole of the input end, and the negative pole of the transmitter is connected with the first negative pole of the input end.

Preferably, the positive pole of the transmitting coil is connected with the second positive pole of the output end, and the negative pole of the transmitting coil is connected with the second negative pole of the output end.

Preferably, the positive pole of the compensating coil is connected with the third positive pole of the output end, and the negative pole of the compensating coil is connected with the third negative pole of the output end.

EFFECT OF THE PRESENT INVENTION

The present invention discloses the following technical effects: in the present invention, the transmitting coil and the compensating are of the same size and they overlap together, and the number of turns of the two coils are equal. Thus,the primary field after the current is turned off in all ranges inside the transmitting coil can be cancelled, and the influence of the turn-off effect on the correctness of the final measurement result can be suppressed effectively, which allows the receiving sensor to transmit. Compared with the traditional technology, the observation of secondary field at any point in the coil , the present invention is much more advanced.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to explain the embodiments of the present invention or the technological schemes in the prior art more clearly, the drawings needed in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention.For those skilled in the art, they can also be obtained according to these drawings without any creative labor.

FIG. 1 is a structural diagram of the transient electromagnetic transmitting and receiving device of the present invention;

FIG.2 is a structural diagram of the conversion circuit of the present invention;

2020100382 12 Mar 2020 ____________________SPECIFICATION____________________

FIG.3 is a curve of the secondary field attenuation signal obtained when the device of the present invention is used for geology exploration.

EXPLANATIONS OF LETTERS OR NUMERALS

The transmitter

The conversion circuit

The transmitting coil

The compensating coil

The input end of the conversion circuit

The output end of the conversion circuit

The first positive pole of the input end of the conversion circuit

The first negative pole of the input end of the conversion circuit

The second positive pole of the output end of the conversion circuit

The second negative pole of the output end of the conversion circuit

The third negative pole of the output end of the conversion circuit

The third positive pole of the output terminal of the conversion circuit BEST MODE(S) FOR CARRYING OUT THE PRESENT INVENTION

The technical scheme in the embodiment of the present invention will be described clearly and completely in combination with the drawings in the embodiment of the present invention. Obviously, the described embodiment is only a part of the embodiment of the present invention, not all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by those skilled in the art without creative labor belong to the scope of the protection of the present invention.

The disclosure may be more completely understood in consideration of the following detailed of the disclosure in connection with the accompanying drawings.

As shown in FIG 1-3, the present invention provides a transient

2020100382 12 Mar 2020 ____________________SPECIFICATION____________________ electromagnetic transmitting and receiving device. As shown in FIG.1, the present invention includes a transmitted 1), a conversion circuit(2), a transmitting coil(3) and a compensating coil(4), wherein the transmitted 1) is connected with the conversion circuit(2), and the conversion circuit(2) is simultaneously connected with the transmitting coil(3) and the compensating coil(4), respectively.The size of the transmitting coil(3) and the compensating coil(4) are both 50mX50m, and they overlap together. The emission voltage of the transmitting coil(3) is 24V.

As shown in FIG.2, the conversion circuit(2) comprises an input terminal(5) and an output terminal(6), the input terminal(5) comprises a first positive pole(7) and a first negative pole(8), and the output terminal(6) comprises a second positive pole(9), a second negative pole(10), a third negative pole(ll) and a third positive pole(12).

The positive pole of the transmitted 1) is connected with the first positive pole(7) of the input terminal(5), and the negative pole of the transmitted 1) is connected with the first negative pole(8) of the input terminal(5). The positive pole of the transmitting coil(3) is connected with the second positive pole(9) of the output end, and the negative pole of the transmitting coil(3) is connected with the second negative pole(10) of the output end(6). The positive pole of the compensating coil(4) is connected with the third positive pole(12) of the output terminal(6), the negative pole of the compensating coil(4) is connected with the third negative pole(ll) of the output terminal(6), and the transmitting coil(3) and the compensating coil(4) are connected in reverse through the conversion circuit(2).

Install the device of the present invention in the terra TEM instrument, then the exploration and measurement can be carried out by using the transient electromagnetic method. First, turn on the power supply of the transmitted 1), when the transmitted 1) is powered on, only the second positive(9) and the second negative(lO) circuits in the output terminal(6) are connected, while the third positive(12) and the third negative(ll) circuits are open, so as to ensure that only

2020100382 12 Mar 2020 ____________________SPECIFICATION____________________ the current in the transmitting coil(3) flows and no current flows in the compensating coil(4). Second, turn off the power supply of the transmitted 1), when the transmitted 1) is powered off, the compensating coil(4) will be connected, that is to say, the second positive(9) and the second negative(lO) circuits will be connected in series with the transmitting coil(3). At this very moment, the circuit loop can be expressed as follows:

the second positive ( 9) to the second negative (1O) to the third negative (11) -> the third positive (12) to the second positive (9)

When the transmitted 1) is powered off, the current of the transmitting coil(3) will not be eliminated completely, whereas the residual current continues to flow in the compensating coil(4) in the opposite direction, so that the primary field generated in the transmitting coil(3) can be offseted, and the intensity of the secondary field will not be weakened. Finally, the measured secondary field attenuation signal curve graph shown in FIG.3 can be obtained. It can be clearly seen that since the size of the transmitting coil(3) and the compensating coil(4) in this embodiment are the same and they overlap together, the primary field after the current switch off can be cancelled in all ranges within the transmitting coil(3), which reduce the blind depth of TEM detection effectivly. According to the results recorded by the instrument, the T/O time is only about 2 microseconds, which effectively suppresses the influence of the turn-off effect on the accuracy of the measurement results. In this way, the receiving sensor can perform secondary field observation at any point inside the transmitting coil(3). Compared with the traditional technology, which can only observe at the center of the transmitting coil, the present invention has made obvious technical progress.

While the specification has described in detail certain exemplary embodiments, it will be appreciated that those skilled in the art, upon attaining an understanding of the foregoing, may readily conceive of alterations to, variations of, and equivalents to these embodiments.

2020100382 12 Mar 2020 ____________________SPECIFICATION____________________

Embodiments of the present disclosure may take on various modifications and alternations without departing from the spirit and scope of the disclosure. Accordingly, it should be appreciated that the embodiments of the present disclosure are not to be limited to the above described exemplary embodiments, but is to be controlled by the limitations set forth in the claims and any equivalents thereof.

Claims (6)

1 .A transient electromagnetic transmitting and receiving device,comprising: a transmitter/1), a conversion circuit(2), a transmitting coil(3) and a compensating coil(4),wherein the transmitter/1) is connected with the conversion circuit(2);the conversion circuit(2) is connected with the transmitting coil(3) and the compensating coil(4).

2. The transient electromagnetic transmitting and receiving device as claimed in claim 1, wherein the dimensions of the transmitting coil(3) and the compensating coil(4) are exactly the same and they overlap together;the turns of the transmitting coil(3) and the compensating coil(4) are equal, the turns are one or more.

3. The transient electromagnetic transmitting and receiving device as claimed in claim 1, wherein the conversion circuit(2) comprises an input terminal(5) and an output terminal(6);the input terminal(5) comprises a first positive pole(7) and a first negative pole(8), and the output terminal(6) comprises a second positive pole(9), a second negative pole(10), a third negative pole/ll) and a third positive pole(12).

4. The transient electromagnetic transmitting and receiving device as claimed in claim 3, wherein the positive pole of the transmitter/1) is connected with the first positive pole(7) of the input end(5);the negative pole of the transmitter/1) is connected with the first negative pole(8) of the input end(5).

5. The transient electromagnetic transmitting and receiving device as claimed in claim 3, wherein the positive pole of the transmitting coil(3) is connected with the second positive pole(9) of the output end(6);the negative pole of the transmitting coil(3) is connected with the second negative pole/10) of the output end(6).

6. The transient electromagnetic transmitting and receiving device as claimed in claim 3, wherein the positive pole of the compensating coil(4) is connected with the third negative pole/ll) of the output end(6); the negative pole of the compensating coil(4) is connected with the third positive pole/12) of the output end(6).