Transient electromagnetic secondary field receiving circuit and use method thereof

Abstract

The invention provides a transient electromagnetic secondary field receiving circuit and a use method thereof. The transient electromagnetic secondary field receiving circuit comprises a transmitting part, a current sensing and converting part, a control and switch part and a signal receiving and processing part, wherein the transmitting part comprises a transmitting bridge circuit and a transmitting coil, and the output end of the transmitting bridge circuit is connected with the input end of the transmitting coil; the current sensing and converting part comprises a current sensor and a voltage comparator, the current sensor is connected in series or in parallel in a current loop of the transmitting coil, and the output end of the current sensor is connected to the input end of the voltage comparator; the control and switch part comprises a control circuit and an electronic switch; the control circuit is respectively connected to the transmitting bridge circuit, the electronic switch and the voltage comparator; the signal receiving and processing part comprises a receiving coil and an acquisition circuit, and the output end of the receiving coil is connected to the input end of the acquisition circuit through an electronic switch. Through the high-speed electronic switch, the receiving coil is closed after emission current is completely cut off, and then the receiving coil is connected to the acquisition circuit.

Description

Technical Field

[0001] The present invention relates to the technical field of mine disaster detection and prevention, and in particular to a transient electromagnetic secondary field receiving circuit and a use method thereof. Background Art

[0002] Transient electromagnetic method is a method that uses an ungrounded return line or a grounded line source to emit a pulse magnetic field underground, and uses a coil or a grounding electrode to observe the secondary induced eddy current field caused in the underground medium during the interval of a pulse magnetic field. According to the scope of application, transient electromagnetic method includes aviation, ground, ocean, and mine transient electromagnetic method. Mine transient electromagnetic method is widely used in the field of coal mine underground excavation front, roadway roof and floor, working face roof and floor, and side wall water hazard detection. It is a time domain method.

[0003] Transient electromagnetic detection technology in mines is mainly used for the detection of water bodies that can cause disasters in underground projects. Since the traditional transient electromagnetic instrument directly connects the receiving coil to the receiving circuit, the primary field of the transmitting current will cause the transmitting current to form an induced current in the receiving coil and store energy. After the transmitting current is completely turned off, the primary field in the receiving coil will not completely disappear, resulting in the expansion of the blind area of ​​shallow detection.

[0004] Therefore, it is necessary to propose a transient electromagnetic secondary field receiving device to solve the above problems. Summary of the invention

[0005] Aiming at the problem that the existing transient electromagnetic receiving coil is always connected to the collection circuit during the transmission period, which leads to the expansion of the shallow detection blind area, the present invention proposes a transient electromagnetic secondary field receiving circuit and a use method thereof.

[0006] In order to achieve the above object, the embodiments of the present invention are implemented in the following manner:

[0007] In the first aspect, the present invention provides a transient electromagnetic secondary field receiving device, including a transmitting part, a current sensing and conversion part, a control and switch part, and a signal receiving and processing part; the transmitting part includes a transmitting bridge and a transmitting coil, wherein the output end of the transmitting bridge is connected to the input end of the transmitting coil; the current sensing and conversion part includes a current sensor and a voltage comparator, wherein the current sensor is connected in series or in parallel in the current loop of the transmitting coil, and the output end of the current sensor is connected to the input end of the voltage comparator; the control and switch part includes a control circuit and an electronic switch, wherein the control circuit is respectively connected to the transmitting bridge, the electronic switch and the voltage comparator; the signal receiving and processing part includes a receiving coil and an acquisition circuit, wherein the output end of the receiving coil is connected to the input end of the acquisition circuit through the electronic switch.

[0008] Furthermore, the output end of the receiving coil is connected to the input end of the acquisition circuit through an electronic switch, and the electronic switch is disconnected during the transmission and shutdown of the transmitting current; when the current sensor senses that the transmitting current is completely shut down, the electronic switch is controlled to be closed through the voltage comparator, and the receiving coil is connected to the acquisition circuit.

[0009] Furthermore, the response time of the electronic switch does not exceed 1 us.

[0010] Furthermore, the threshold of the emission current voltage comparator can be adjusted and set according to actual needs.

[0011] On the other hand, the present invention provides a transient electromagnetic secondary field receiving method, comprising the following parts:

[0012] S101: The controller turns off the electronic switch to disconnect the electrical connection between the receiving coil and the acquisition circuit to ensure that the receiving coil is not disturbed during the signal transmission. Subsequently, the controller turns on the field effect transistors on the transmitting bridge circuit one by one in sequence to control the current to flow to the transmitting coil, providing the transmitting coil with a square wave current to generate an electromagnetic field;

[0013] S102: After the transmission of the electrical signal is completed, the controller is connected again to turn off the field effect transistors on the transmitting bridge circuit one by one in sequence to stop supplying current to the transmitting coil. At the same time, the current in the transmitting coil will naturally decay to zero;

[0014] S103: When the current of the transmitting coil decays to a predetermined threshold voltage, the current sensor detects this change and triggers the voltage comparator, and the output signal of the voltage comparator is then received by the controller as a trigger interrupt signal;

[0015] S104: After receiving the trigger interrupt, the controller immediately executes to turn on the electronic switch and re-establish the electrical connection between the receiving coil and the acquisition circuit, so that the acquisition circuit starts to work, acquires and processes the received pure secondary field signal.

[0016] Furthermore, before starting to transmit a field, the electronic switch is turned off by the controller to physically disconnect the electrical connection between the receiving coil and the acquisition circuit, so that the receiving coil remains open-circuited, ensuring that the transmitting coil will not be directly interfered by the transmitting signal, thereby ensuring the purity of the received signal.

[0017] Furthermore, the threshold of the emission current voltage comparator can be adjusted and set according to actual needs.

[0018] In combination with the first aspect, when the current of the transmitting coil decays to a predetermined threshold voltage, the current sensor detects this change and transmits the signal to the voltage comparator for comparison. Once the voltage comparator confirms that the current decays to the preset threshold, it outputs a trigger signal to the controller. After receiving the trigger interrupt signal, the controller immediately performs a predetermined operation, that is, turns on the electronic switch to re-establish the electrical connection between the receiving coil and the acquisition circuit. Subsequently, the acquisition circuit starts to work, and collects and processes the pure secondary field signal received by the receiving coil with high precision for subsequent data analysis.

[0019] Since the traditional transient electromagnetic instrument directly connects the receiving coil to the receiving circuit, the primary field of the transmitting current will cause the transmitting current to form a primary induced current in the receiving coil and store energy. After the transmitting current is completely turned off, the primary field in the receiving coil will not completely disappear, resulting in the expansion of the blind area of ​​shallow detection. The present invention can solve the problem of blind area expansion by lagging the connection of the transient electromagnetic receiving coil and lagging the reception and collection of the secondary field signal.

[0020] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, preferred embodiments are given below and described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0022] Figure 1 A schematic structural diagram of a transient electromagnetic secondary field receiving device provided by an embodiment of the present invention;

[0023] Figure 2 One of the flow charts of a receiving method of a transient electromagnetic secondary field receiving device provided by an embodiment of the present invention;

[0024] Figure 3 The present invention provides a second flowchart of a receiving method for a transient electromagnetic secondary field receiving device according to an embodiment of the present invention. DETAILED DESCRIPTION

[0025] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0026] See also Figure 1 , Figure 1 A schematic structural diagram of a transient electromagnetic secondary field receiving device provided by the present invention.

[0027] The present invention provides a transient electromagnetic secondary field receiving device, comprising a control circuit 5, which is used to control the on and off of a transient electromagnetic bridge circuit 1, and the connection and disconnection of a receiving coil 2; a transmitting bridge circuit 1, which is connected to the transmitting coil 2 and the control circuit 5, and is used to provide a transmitting current loop for the transmitting coil 2, and to produce a bipolar square wave; the transmitting coil 2, which is connected to the transmitting bridge circuit 1, is used to transmit a primary magnetic field outward; a current sensor 3, which is connected to the transmitting coil 2 and a voltage comparator 4, is used to detect the current in the transmitting coil 2; the voltage comparator 4, which is connected to the current sensor 3 and the control circuit 5, is used to set a transmitting current comparison threshold; an electronic switch 7, which is connected to the receiving coil 8, the control circuit 5 and the acquisition circuit 6, is used to switch the connection and disconnection of the receiving coil 8; the receiving coil 8, which is connected to the electronic switch 7, is used to receive a secondary magnetic field; and the acquisition circuit 6, which is connected to the electronic switch 7 and the control circuit 6, is used to acquire the secondary magnetic field.

[0028] As a preferred embodiment, the output end of the receiving coil 8 is connected to the input end of the acquisition circuit 6 through the electronic switch 7. During the transmission and shutdown of the transmitting current, the electronic switch 7 is disconnected; when the current sensor 3 senses that the transmitting current is completely shut down, the electronic switch 7 is controlled to be closed through the voltage comparator 4, and the receiving coil 8 is connected to the acquisition circuit.

[0029] As a preferred implementation, the response time of the electronic switch does not exceed 1 us.

[0030] As a preferred implementation, the threshold of the emission current voltage comparator can be adjusted and set according to actual needs.

[0031] As a preferred embodiment, the present invention provides a method for using a transient electromagnetic secondary field receiving device, specifically as follows: Figure 3 Said include:

[0032] Step 1: The controller turns off the electronic switch to disconnect the electrical connection between the receiving coil and the acquisition circuit, so that the receiving coil remains open circuit to ensure that the receiving coil is not disturbed during the transmission of the signal. Subsequently, the controller turns on the field effect transistors on the transmitting bridge circuit one by one in sequence to control the current to flow to the transmitting coil, providing the transmitting coil with a square wave current to generate an electromagnetic field;

[0033] Step 2: After the transmission of the electrical signal is completed, the controller is connected again and the field effect tubes on the transmitting bridge are turned off one by one in sequence to stop supplying current to the transmitting coil. At the same time, the current in the transmitting coil will naturally decay to zero;

[0034] Step 3: When the current of the transmitting coil decays to a predetermined threshold voltage, the current sensor detects this change and triggers the voltage comparator, and the output signal of the voltage comparator is then received by the controller as a trigger interrupt signal;

[0035] Step 4: After receiving the trigger interrupt, the controller immediately executes, turns on the electronic switch, and re-establishes the electrical connection between the receiving coil and the acquisition circuit, so that the acquisition circuit starts working, collects and processes the pure secondary field signal received previously.

[0036] In addition, the present invention provides another operation process of a transient electromagnetic secondary field receiving device which may be:

[0037] See also Figure 2 , Figure 2 A schematic diagram of the use process of a transient electromagnetic secondary field receiving device provided by the present invention:

[0038] S1, the controller 5 turns off the electronic switch 7, disconnecting the receiving coil 8 from the acquisition circuit 6;

[0039] S2, under the control of the controller 5, the transmitting bridge circuit 1 turns on the field effect transistors on the bridge circuit 1 in sequence according to the opening sequence of the transient electromagnetic bridge circuit 1, and provides a square wave current for the transmitting coil 2;

[0040] S3, under the control of the controller 5, the transmitting bridge circuit sequentially closes the field effect tubes on the bridge circuit 1 according to the closing order of the transient electromagnetic bridge circuit 1;

[0041] S4, the current in the transmitting coil 2 gradually decays to zero;

[0042] S5, after the current sensor 3 detects that the current in the transmitting coil decays to the threshold voltage set in the voltage comparator 4, a trigger interrupt is caused in the controller 5 through the voltage comparator 4;

[0043] S6, after the controller 5 receives the trigger interrupt caused by the voltage comparator 4, it turns on the electronic switch 7, connects the receiving coil 8 to the acquisition circuit, and the acquisition circuit 6 acquires the pure secondary field;

[0044] The present invention has the following beneficial effects:

[0045] Transient electromagnetic detection technology in mines is mainly used for the detection of disaster-causing water bodies in underground projects. Since the traditional transient electromagnetic instrument directly connects the receiving coil to the receiving circuit, the primary field of the transmitting current will cause the transmitting current to form a primary induced current in the receiving coil and store energy. After the transmitting current is completely turned off, the primary field in the receiving coil will not completely disappear, resulting in the expansion of the shallow detection blind area. The present invention has a delayed access to the transient electromagnetic receiving coil and a delayed reception and collection of the secondary field signal, which can solve the problem of the expansion of the blind area.

[0046] More specifically, the present invention proposes a transient electromagnetic secondary field receiving device, which uses an electronic switch with a response time of no more than 1μs to close the receiving coil and connect it to the acquisition circuit after the transmitting current is completely turned off. Since the receiving coil is not closed and there is no current loop during the transmission and shutdown of the transmitting current, no energy is stored in the receiving coil. After the transmitting current is completely turned off, the receiving coil receiving signal only contains the secondary field signal. This avoids the disadvantage that the transmitting current forms a primary induced current in the receiving coil and stores energy because the receiving coil is closed during the transmission period, and the primary field in the receiving coil does not completely disappear after the transmitting current is completely turned off. The influence time of the primary field is shortened, and the detection blind area is shortened.

[0047] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A transient electromagnetic secondary field receiving circuit, comprising a transmitting part, a current sensing and conversion part, a control and switching part, and a signal receiving and processing part; characterized in that: The transmitting part comprises a transmitting bridge circuit (1) and a transmitting coil (2), wherein the output end of the transmitting bridge circuit (1) is connected to the input end of the transmitting coil (2); The signal sensing and conversion part comprises a current sensor (3) and a voltage comparator (4), wherein the current sensor (3) is connected in series or in parallel to the current loop of the transmitting coil (2), and the output end of the current sensor (3) is connected to the input end of the voltage comparator (4); The control and switch part comprises a control circuit (5) and an electronic switch (7), wherein the control circuit (5) is connected to the transmitting bridge circuit (1), the electronic switch (7) and the voltage comparator (4) respectively; The signal receiving and processing part comprises a receiving coil (8) and a collection circuit (6), and the output end of the receiving coil (8) is connected to the input end of the collection circuit (6) through an electronic switch (7).

2. A transient electromagnetic secondary field receiving circuit according to claim 1, characterized in that: The output end of the receiving coil (8) is connected to the input end of the acquisition circuit (6) through an electronic switch (7); during the transmission and shutdown of the transmission current, the electronic switch (7) is disconnected; when the current sensor (3) senses that the transmission current is completely shut off, the electronic switch (7) is controlled to be closed through the voltage comparator (4), and the receiving coil (8) is connected to the acquisition circuit.

3. A transient electromagnetic secondary field receiving circuit according to claim 1, characterized in that: The response time of the electronic switch does not exceed 1us.

4. A transient electromagnetic secondary field receiving circuit according to claim 2, characterized in that: The threshold of the emission current voltage comparator can be adjusted and set according to actual needs.

5. A method for receiving and using a transient electromagnetic secondary field, comprising the following parts: S101: The controller turns off the electronic switch to disconnect the electrical connection between the receiving coil and the acquisition circuit to ensure that the receiving coil is not disturbed during the signal transmission. Subsequently, the controller turns on the field effect transistors on the transmitting bridge circuit one by one in sequence to control the current to flow to the transmitting coil, providing the transmitting coil with a square wave current to generate an electromagnetic field; S102: After the transmission of the electrical signal is completed, the controller is connected again to turn off the field effect transistors on the transmitting bridge circuit one by one in sequence to stop providing current to the transmitting coil. At the same time, the current in the transmitting coil will naturally decay to zero; S103: When the current of the transmitting coil decays to a predetermined threshold voltage, the current sensor detects this change and triggers the voltage comparator, and the output signal of the voltage comparator is then received by the controller as a trigger interrupt signal; S104: After receiving the trigger interrupt, the controller immediately executes to turn on the electronic switch and re-establish the electrical connection between the receiving coil and the acquisition circuit, so that the acquisition circuit starts to work, acquires and processes the received pure secondary field signal.

6. A method for receiving and using a transient electromagnetic secondary field according to claim 5, characterized in that: Before starting to transmit the electromagnetic signal, the controller turns off the electronic switch to physically disconnect the electrical connection between the receiving coil and the acquisition circuit, keeping the receiving coil open and ensuring that the transmitting coil will not be directly interfered by the primary field of the transmitting current, thereby ensuring the purity of the received signal.

7. The method for receiving and using a transient electromagnetic secondary field according to claim 5, characterized in that: The threshold of the emission current voltage comparator can be adjusted and set according to actual needs.

8. A transient electromagnetic secondary field receiving and application method according to claim 5, characterized in that: When the current of the transmitting coil decays to a predetermined threshold voltage, the current sensor detects this change and transmits the signal to the voltage comparator for comparison. Once the voltage comparator confirms that the current has decayed to the preset threshold, it outputs a trigger signal to the controller. After receiving the trigger interrupt signal, the controller immediately performs a predetermined operation, that is, turns on the electronic switch and reestablishes the electrical connection between the receiving coil and the acquisition circuit. Subsequently, the acquisition circuit starts to work, and collects and processes the pure secondary field signal received by the receiving coil with high precision for subsequent data analysis.

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