WO2018126808A1 - Electromagnetic method prospected primary field loose coupling receiving device and method - Google Patents

Abstract

An electromagnetic method prospected primary field loose coupling receiving device and method. The device comprises: a transmitter (1), a transmit coil (2), a signal conditioning module (4), and a receiver (5). Two transmit output ends of the transmitter (1) are connected to both ends of the transmit coil (2). The device further comprises n receive coils. The n receive coils constitute a receive coil module (3). The receive coil module (3) is connected to the signal conditioning module (4). The output end group of the signal conditioning module (4) is connected to the receiver (5). The receive coil module (3) is disposed at an edge of the transmit coil (2). The receive coil module (3) partially intersects the transmit coil (2). Part of the orthographic projection of the transmit coil (2) overlaps part of the orthographic projection of the receive coil module (3). Aliasing of a primary field and second field of a conventional receive coil is eliminated; the dynamic range of a receive signal is reduced, and the problem of being difficult to receive a signals of a weak second field is resolved; the application range is wide; an integrated system and convenient use are achieved; easy operation and accurate and reliable conditioning effect are achieved.

Description

Primary field weak coupling receiving device and method for electromagnetic method exploration Technical field

The invention relates to the technical field of electromagnetic method exploration, in particular to a field weak coupling receiving device and method for electromagnetic method exploration.

Background technique

Electromagnetic exploration has been widely used in mineral exploration, engineering geological exploration, groundwater resources, underground pipelines and environmental geological exploration. Among them, frequency domain electromagnetic method and time domain electromagnetic method are commonly used, and electromagnetic transmitter is used to generate excitation field. The secondary field induced by the geological body is collected by the receiver, and the structure of the geological body is detected by analyzing the secondary field.

However, in the prior art, electromagnetic exploration still has the following disadvantages: 1. There is mutual inductance between the transmitting coil and the receiving coil, and the signal sensed by the receiving coil not only has the secondary field signal collected by the receiver, but also has electromagnetic transmission. The machine generates the excitation primary field, and there is a problem of primary field and secondary field aliasing. 2. Since the amplitude of the primary field signal is large and the amplitude of the secondary field is small, it is very difficult to distinguish the secondary field in the background of one field. The receiving signal has a large fluctuation range and is difficult to receive the secondary field signal. 3. The conventional small wire frame same-point device has a large number of transmitting and receiving coils, and the mutual inductance is strongly affected. The conventional small wire frame and the same point device have poor reliability, and it is difficult to obtain practical application; The transmission and reception are relatively independent of the two systems. The relative position of the exploration is uncertain, the mutual inductance changes greatly, the distortion of the signal is uncertain, and the error of the detection data is large, and the use is inconvenient. For example, the patent authorization number is ZL200720151836.7 "a transient electromagnetic instrument", which can eliminate the influence of the field during the power supply and after a short time after the shutdown, but after the switch is switched, the mutual inductance still exists, and there is still a signal mixture. The stacking problem, in addition, uses four switches, the structure is complicated, and the switching of the switch has an adverse effect on the received signal. 5. The patent transmission authorization number is 2010101145349 "An integrated method and device for transmitting and receiving electromagnetic surveys" can achieve the elimination of one field by adjusting the number of turns of the receiving coils disposed inside and outside the transmitting coil, but this adjustment mode relies on The combination of the number of turns is prone to non-integer 匝, resulting in lower accuracy of the primary field elimination, and the concentrated winding of the receiving coil has a large self-inductance, which easily causes distortion of the received signal. Summary of the invention

In view of the above problems, the present invention provides an apparatus and method for transmitting and receiving integrated for electromagnetic method exploration, which cancels the mutual inductance effect between the transmitting coil and the receiving coil, and eliminates the influence of the excitation primary field generated by the electromagnetic transmitter.

To achieve the above objectives, the specific technical solutions adopted by the present invention are as follows:

A field weak coupling receiving device for electromagnetic method exploration, comprising a transmitter, a transmitting coil, a signal conditioning module and a receiver, wherein two transmitting output ends of the transmitter are connected with two ends of the transmitting coil, and the key thereof The method further includes: n receiving coils, the n receiving coils constitute a receiving coil module, the receiving coil module is connected to the signal conditioning module, and the signal conditioning module output end group is connected to the receiver; A receiving coil module is disposed at an edge of the transmitting coil, the two of which partially intersect, a partial orthographic projection of the transmitting coil and a partial orthographic projection of the receiving coil module coincide.

The n receiving coils are arranged at the edge of the transmitting coil, and the two parts are partially overlapped. The magnetic lines of the two directions in the receiving coil pass through, which can achieve the function of canceling, so that the magnetic flux generated by the transmitting coil passing through the receiving coil is zero, eliminating The action of the primary field generated by the transmitting coil improves the detection accuracy of the receiving coil. Wherein, the transmitting coil is either circular or square or elliptical or a polygonal coil. The receiving coil is either square or elliptical or polygonal or circular.

The magnetic flux emitted by the transmitting coil passing through the receiving coil module receiving coil is adjustable.

With the above technical solution, when the magnetic lines of force passing through and out of the receiving coil are not equal, the area of the intersection area between the receiving coil and the transmitting coil can be adjusted, or the relative heights of the receiving coil and the transmitting coil can be adjusted.

The receiving coil module is a receiving coil array, and the receiving coil array is composed of n independent working n receiving coils, and all receiving coil wires are wound in the same direction. The n receiving coils are independent of each other, complement each other, and receive each. The independent effect is good and the mutual interference is small. Still further described, the signal conditioning module comprises n independent signal conditioning circuits, each of the receiving coil is connected to a separate signal conditioning circuit, the starting end of the receiving coil corresponding to A _m and the signal conditioning circuit being The input terminal is connected, and the receiving coil end terminal B _{m is} connected to a reference end corresponding to the signal conditioning circuit. The signals received by the n receiving coils are processed by n independent signal conditioning circuits.

As another technical solution, the signal conditioning module includes a signal conditioning circuit, and all of the receiving coils are sequentially connected in series, wherein a starting end A ₁ of the first receiving coil is connected to a positive input end of the signal conditioning circuit, The end receiving end point B _n of the receiving coil is connected to a reference end corresponding to the signal conditioning circuit.

According to the above technical solution, n receiving coils are sequentially connected in series, disposed at the edge of the transmitting coil, and the n receiving coils are subjected to receiving signal adjustment by a signal conditioning circuit, and the signal processing is simple and convenient. Wherein, among the n receiving coils, n ₁ of the receiving coils are uniformly disposed at an edge of the transmitting coil (2), and the n ₁ receiving coils partially intersect with the transmitting coil (2); n ₂ receiving coils are completely located in the transmitting coil (2); n ₃ receiving coils are completely outside the transmitting coil (2); wherein n ₁ , n ₂ , n ₃ are integers greater than or equal to 0, and n ₁ +n ₂ +n ₃ =n.

Further, the receiving coil is a strip coil, the strip coil is annular, and is disposed around the edge of the transmitting coil, the two portions are partially intersected, and part of the orthographic projection of the transmitting coil and a portion of the strip coil are positive The projections coincide.

In the above solution, the receiving coil is wound into a strip shape by a wire, and the inner coil portion of the strip coil is disposed in the transmitting coil, and the outer ring portion is disposed outside the transmitting coil, by adjusting the overlapping portion of the strip coil and the transmitting coil. Adjust the size of the magnetic flux.

Further, the signal conditioning circuit includes a damping resistor R ₀ , a voltage follower A ₁ , an operational amplifier A ₂ , an input resistor R ₁ and a feedback resistor R ₂ ; one end of the damping resistor R ₀ serves as the signal conditioning end of the reference circuit, the reference end, the noninverting input damping resistor R ₀ and the other end of the voltage follower a ₁ is connected to the noninverting input of voltage follower a ₁ as the signal conditioning a positive input terminal, an output of the voltage follower A ₁ is connected to the inverting input terminal of the voltage follower A _{1 ;} an output end of the voltage follower A ₁ is connected to _one end of the input resistor R ₁ The other end of the input resistor R ₁ is connected to the inverting input terminal of the operational amplifier A ₂ , the non-inverting input terminal of the operational amplifier A ₂ is connected to the reference terminal, and the output terminal of the operational amplifier A ₂ is said feedback resistor R ₂ is connected to the inverting input terminal a ₂ of the operational amplifier, the output of the operational amplifier a ₂ and the receiver is connected to a positive input terminal, a reference terminal of said signal conditioning circuit Common reference of the receiver Test terminal connection.

With the above technical solution, the signal conditioning circuit processes the signal received by the receiving coil.

An independent exploration method for a field weakly coupled receiving device for electromagnetic surveying, the key of which comprises the following steps:

S1: starting the transmitter, and applying a current i(t) to the transmitting coil;

S2: Calculating the primary field flux ψ _{m1 of} the mth receiving coil (m=1, 2, ..., n,)

Where: N ₁ : total number of turns of the transmitting coil; N _m : total number of turns of the mth receiving coil; the structural specification should add that each coil can be single or multiple turns; k: summation variable of the transmitting coil ;i: summation variable of the mth receiving coil; μ ₀ : vacuum permeability, μ ₀ = 4π × 10 ^-7 H/m;

i(t): the current through which the transmitting coil passes; θ _mki : the angle between the i-th coil plane of the mth receiving coil and the normal direction of the kth coil of the transmitting coil; l _1k : the path of the kth coil of the transmitting coil;

a line element vector on the kth coil of the transmitting coil;

The mth receiving coil, the i-th coil plane, and the transmitting coil 1, the kth coil element vector

Relative position vector; R _mki : a certain point of the mth receiving coil, the i-th coil plane, and the k-th coil element vector of the transmitting coil 1

a mode of the relative position vector; S _mi : a planar range of the mth receiving coil of the i-th coil;

a plane bin vector of the i-th coil of the mth receiving coil;

S3: adjusting the size of the n receiving coils and the relative position of the transmitting coil (2) such that the primary field magnetic flux ψ _m1 =0 of the n receiving coils;

S4: Calculate the magnetic flux ψ _m2 (m=1, 2..., n) passing through the mth receiving coil under the action of the secondary field:

Where: B(t): secondary field magnetic induction; S _mi : area of the i-th coil of the mth receiving coil; α _mi : direction of the first direction of the coil and the direction of the secondary field magnetic induction of the coil m Angle

S5: calculating the induced voltage of the mth receiving coil

among them:

a field induced voltage between the start and end points of the mth receiving coil;

a secondary field induced voltage between the start and end points of the mth receiving coil;

S6: obtained in combination with step S3

Then the induced voltage of the n receiving coils

for:

A series exploration method for a field weakly coupled receiving device for electromagnetic surveying, the key of which comprises the following steps:

S1: starting the transmitter, and applying a current i(t) to the transmitting coil;

S2: calculated m-th receiving coil of the primary field flux _{ψ m1 (m = 1,2, ...} , n)

Where: N ₁ : total number of turns of the transmitting coil; N _m : total number of turns of the mth receiving coil; the structural specification should add that each coil can be single or multiple turns; k: summation variable of the transmitting coil ;i: summation variable of the mth receiving coil; μ ₀ : vacuum permeability, μ ₀ = 4π × 10 ^-7 H/m;

i(t): the current through which the transmitting coil passes; θ _mki : the angle between the i-th coil plane of the mth receiving coil and the normal direction of the kth coil of the transmitting coil; l _1k : the path of the kth coil of the transmitting coil;

a line element vector on the kth coil of the transmitting coil;

The mth receiving coil, the i-th coil plane, and the transmitting coil 1, the kth coil element vector

Relative position vector; R _mki : a certain point of the mth receiving coil, the i-th coil plane, and the k-th coil element vector of the transmitting coil 1

a mode of the relative position vector; S _mi : a planar range of the mth receiving coil of the i-th coil;

a plane bin vector of the i-th coil of the mth receiving coil;

S3: adjusting the size of the n receiving coils and the relative position of the transmitting coils (2) so that the primary field fluxes of the n receiving coils

S4: Calculate the magnetic flux ψ _m2 (m=1, 2..., n) passing through the mth receiving coil under the action of the secondary field:

Where: B(t): secondary field magnetic induction; S _mi : area of the i-th coil of the mth receiving coil; α _mi : direction of the first direction of the coil and the direction of the secondary field magnetic induction of the coil m Angle

S5: calculating the induced voltage of the mth receiving coil

among them:

a field induced voltage between the start and end points of the mth receiving coil;

a secondary field induced voltage between the start and end points of the mth receiving coil;

S6: obtained in combination with step S3

Then the induced voltage of the n receiving coils

for:

The invention has the beneficial effects that the field magnetic flux cancellation is realized on each receiving coil by adjusting the relative arrangement positions of the receiving coil and the transmitting coil, thereby eliminating the phenomenon of the primary field and the secondary field aliasing of the conventional receiving coil; Conventional receiving coil primary field and secondary field aliasing phenomenon, the dynamic range of the received signal is reduced, solving the problem of receiving weak secondary field signal; wide application range; integrated system, easy to use; convenient operation, accurate and reliable adjustment effect .

DRAWINGS

1 is a block diagram showing the structure of a first system series coil of the present invention;

Figure 2 is a block diagram showing the structure of the independent coil of the second system of the present invention;

3 is a circuit schematic diagram of a detecting device composed of a series receiving coil of the present invention;

Figure 4 is a circuit diagram of a detecting device composed of a strip-shaped receiving coil of the present invention;

Figure 5 is a vector diagram of the calculation of the primary field flux of the present invention;

Figure 6 is a vector diagram of the calculation of the secondary field flux of the present invention;

7 is a schematic circuit diagram of a spiral coil transmitting and receiving integrated device of the present invention;

Figure 8 is a waveform diagram of currents passed by the time domain electromagnetic method transmitting coil of Figure 7;

Figure 9 is a waveform diagram of the induced voltage of the time domain electromagnetic receiving coil of Fig. 7 and the induced voltage of the receiving coil n;

Figure 10 is a voltage waveform diagram of the induced voltage of the time domain electromagnetic receiving coil of Fig. 7 and the end point of the receiving coil group;

Figure 11 is a waveform diagram of currents passed through the frequency domain electromagnetic transmitting coil of Figure 7;

Figure 12 is a waveform diagram of the induced voltage of the frequency domain electromagnetic receiving coil of Fig. 7 and the induced voltage of the receiving coil n;

Figure 13 is a voltage waveform diagram of the induced voltage of the frequency domain electromagnetic receiving coil of Figure 7 and the end of the receiving coil group;

Figure 14 is a schematic circuit diagram of a square coil transmitting and receiving integrated device of the present invention;

Figure 15 is a current waveform diagram of the passage of the time domain electromagnetic method transmitting coil of Figure 14;

Figure 16 is a waveform diagram of the induced voltage of the time domain electromagnetic receiving coil of Fig. 14 and the induced voltage of the receiving coil n;

Figure 17 is a voltage waveform diagram of the induced voltage of the time domain electromagnetic receiving coil of Fig. 14 and the end point of the receiving coil group;

Figure 18 is a circuit diagram of the hexagonal coil transmitting and receiving integrated device of the present invention;

Figure 19 is a schematic circuit diagram of an elliptical coil transmitting and receiving integrated device of the present invention;

Figure 20 is a graph showing the comparison of induced voltages of distributed and single receiving coils of the present invention;

In the figure, 1. transmitter, 2. transmitting coil, 3. receiving coil module, 4. signal conditioning module, 5. receiver;

In Figure 3, Figure 4, Figure 7, Figure 14, Figure 18, Figure 19:

The transmitting coil passes the forward current i(t) counterclockwise, and the symbol '×' in the outer receiving coil region indicates that the magnetic induction direction is from the paper inward, and the '·' in the inner receiving coil region indicates that the magnetic induction direction is from the paper direction. outer.

detailed description

The specific embodiments and working principles of the present invention will be further described in detail below with reference to the accompanying drawings.

As can be seen from FIG. 1, FIG. 2, FIG. 3, FIG. 4, FIG. 7, FIG. 14, FIG. 18 and FIG. 19, a field weak coupling receiving apparatus and method for electromagnetic method exploration, including a transmitter 1 and a transmission a coil 2, a signal conditioning module 4 and a receiver 5, the two transmission outputs of the transmitter 1 being connected to both ends of the transmitting coil 2, further comprising n receiving coils, the n receiving coils forming a receiving coil Module 3, the receiving coil module 3 is connected to the signal conditioning module 4, and the output processing group of the signal conditioning module 4 is connected to the receiver 5;

The receiving coil module 3 is disposed at an edge of the transmitting coil 2, partially overlapping, and a partial orthographic projection of the transmitting coil 2 coincides with a partial orthographic projection of the receiving coil module 3.

Wherein, the transmitting coil is either circular or square or elliptical or a polygonal coil, and the receiving coil is either circular or square or elliptical or a polygonal coil. As can be seen from Figures 3, 4 and 7, the transmitting coil is a circular coil. As can be seen from Fig. 14, the transmitting coil is a square coil, and the receiving coil is a square coil; as can be seen from Fig. 18, the transmitting coil is a polygonal coil, and the receiving coil is a square coil; as can be seen from Fig. 19, the transmitting coil is elliptical. The coil and the receiving coil are circular coils.

Preferably, the n receiving coils are located in the same plane and at a certain distance from the transmitting coil.

The size of the magnetic flux emitted by the transmitting coil 2 passing through the receiving coil module 3 is adjustable, and the relative height of the receiving coil and the transmitting coil 2 can be adjusted by changing the area of the intersection area.

As an embodiment, in FIG. 2, the receiving coil module 3 is a receiving coil array, which is composed of n independent working n receiving coils, and all receiving coil wires are wound in the same direction.

The signal conditioning module 4 comprises n independent signal conditioning circuits, each of the receiving coil is connected to a separate signal conditioning circuit, said positive input terminal receiving coil corresponding to the start point to the end of A _m and the signal conditioning circuit is connected to The receiving coil end point B _{m is} connected to a reference end corresponding to the signal conditioning circuit.

As can be seen in conjunction with FIG. 1, FIG. 3, FIG. 4, FIG. 7, FIG. 14, FIG. 18, FIG. 19, as another embodiment, the signal conditioning module (4) includes a signal conditioning circuit, and all of the receiving coils in series, where the starting point of the first end a receiving coil ₁ is connected to the positive input terminal of said signal conditioning circuit, receiving said endmost side coil end B _n corresponding to the reference terminal is connected to the signal conditioning circuit.

The receiving coil is a strip coil, the strip coil is annular, and is disposed around the edge of the transmitting coil 2, the two portions are partially overlapped, a partial orthographic projection of the transmitting coil 2 and a partial orthographic projection of the strip coil coincide. See Figure 4 for details.

Where n of the receiving coils are connected in series, n ₁ of the receiving coils are evenly disposed at the edge of the transmitting coil (2), and the n ₁ receiving coils are partially intersected with the transmitting coil (2) ; n ₂ receiving coils are completely located in the transmitting coil (2); n ₃ receiving coils are completely outside the transmitting coil (2); wherein n ₁ , n ₂ , n ₃ are integers greater than or equal to 0, And n ₁ + n ₂ + n ₃ = n.

The signal conditioning circuit includes a damping resistor R ₀ , a voltage follower A ₁ , an operational amplifier A ₂ , an input resistor R ₁ and a feedback resistor R ₂ ;

One end of the damping resistor R ₀ serves as a reference end of the signal conditioning circuit, the reference terminal is grounded, and the other end of the damping resistor R ₀ is connected to the non-inverting input terminal of the voltage follower A ₁ . Follow-inverting input terminal a is _a signal conditioning circuit as the positive input, the output of voltage follower a voltage follower a and the inverting input terminal of _a connection _1; the output of voltage follower a ₁ end of the input end of the resistor R ₁ is connected to the inverting input terminal of the input resistor R ₁ and the other end of the operational amplifier a ₂ is connected to the positive input of the operational amplifier a ₂ of said reference termination terminal, the output terminal of the operational amplifier a ₂ is connected via the ₂ and a ₂ of the inverting input terminal of the operational amplifier feedback resistor R, the output of the operational amplifier a ₂ and the receiver 5 a positive input The terminal is connected, and the reference end of the signal conditioning circuit is connected to the common reference terminal of the receiver 5.

When all of the receiving coils are sequentially connected in series, the serial exploration method includes the following steps:

S1: the transmitter 1 is activated, and the transmitting coil 2 is connected to a current i(t);

S2: calculated m-th receiving coil of the primary field flux _{ψ m1 (m = 1,2, ...} , n)

Where: N ₁ : total number of turns of the transmitting coil 2; N _m : total number of turns of the mth receiving coil; each coil may be single or multiple turns; k: summation variable of the transmitting coil 2; i: mth The summation variable of the receiving coil; μ ₀ : vacuum permeability, μ ₀ = 4π × 10 ^-7 H / m; i (t): current passing through the transmitting coil 2 θ _mki : the mth receiving coil i _匝 The angle between the coil plane and the normal direction of the kth turn of the transmitting coil 2; l _1k : the path of the kth turn of the transmitting coil 2;

Transmitting a line element vector on the kth coil of the coil 2;

The mth receiving coil, the i-th coil plane, and the transmitting coil 1, the kth coil element vector

Relative position vector; R _mki : a certain point of the mth receiving coil, the i-th coil plane, and the k-th coil element vector of the transmitting coil 1

a mode of the relative position vector; S _mi : a planar range of the mth receiving coil of the i-th coil;

a plane bin vector of the mth receiving coil ith coil; S3: adjusting the size of the n receiving coils and the relative position of the transmitting coil 2, so that the first field flux of the n receiving coils

S4: Calculate the magnetic flux ψ _m2 (m=1, 2..., n) passing through the mth receiving coil under the action of the secondary field:

Where: B(t): secondary field magnetic induction; S _mi : area of the i-th coil of the mth receiving coil; α _mi : direction of the first direction of the coil and the direction of the secondary field magnetic induction of the coil m Angle

S5: calculating the induced voltage of the mth receiving coil

among them:

a field induced voltage between the start and end points of the mth receiving coil;

The secondary field induced voltage between the start and end points of the mth receiving coil;

;S6: combined with step S3

Then the induced voltage of the n receiving coils

for:

In Fig. 4, u(t) is an induced voltage generated by the transmitting coil and the receiving coil; u ₀ (t) is an amplified voltage of u(t), and its amplification factor is R ₂ /R ₁ . In FIG. 5, when the kth coil of the transmitting coil 2 passes the current i(t), a vector diagram of the first field flux of the i-th coil of the inner receiving coil and the j-th coil of the outer receiving coil is calculated;

Where: i(t): the current through which the transmitting coil passes; θ _2ki : the angle between the i-th coil plane of the receiving coil and the normal direction of the k-th coil of the transmitting coil; l _1k : the path of the k-th coil of the transmitting coil;

a line element vector on the kth coil of the transmitting coil;

a point at the i-th coil plane of the receiving coil and a k-th coil element vector of the transmitting coil

Relative position vector; θ _nki : the angle between the j-th coil plane of the receiving coil and the normal direction of the k-th coil of the transmitting coil; l _nk : the path of the k-th coil of the transmitting coil;

a point of the j-th coil of the receiving coil and a k-th coil element vector of the transmitting coil

Relative position vector between.

In FIG. 6, a vector diagram for calculating a second field flux of the ith coil of the receiving coil m is calculated;

Where: B(t): secondary field magnetic induction; S _mi : area of the first coil of the receiving coil m; l _mi : path of the first coil of the receiving coil m;

The normal direction of the coil ith coil of the receiving coil m; αm: the angle between the normal direction of the ith coil of the receiving coil m and the direction of the secondary field magnetic induction intensity;

Embodiment 1, applied to the time domain electromagnetic method, is performed in the following sequence steps:

As shown in Fig. 7, the plane selects the center point O, and the design transmitting coil 2 is a 20-inch planar spiral coil, and each coil is approximately a circle; the innermost coil has a radius of 400 mm, the outermost coil has a radius of 460 mm, and the line width is 2.5 mm. , the distance between lines is 0.5mm;

Each sub-receiving coil is designed to be a 300-turn spiral coil, and each turn coil is approximately a circle; the innermost coil has a radius of 100.5 mm, the outermost coil has a radius of 120.5 mm, the line width is 0.5 mm, and the line-to-line distance is 0.5.

2. Calculate the magnetic flux ψ _m1 (m=1, 2, 3,...7) that the sub-receiving coil m passes under the action of one field.

得:ψ _m1 ≈1.5149×10 ^-9 i(t)(Wb)

3. Start the transmitter and send the current as shown in Figure 8. The horizontal axis is time t, each cell is 0.02 ms; the vertical axis is current, each cell is 1 A; the signal is the transmission current in Embodiment 1, and the current is transmitted. Frequency is 32Hz, the current is sent by current sensing The current measurement has a conversion ratio of 100mV/A, so the peak value of the transmission current is 7.1A.

According to FIG. 9, the horizontal axis is time t, each cell is 20 μs; the vertical axis is voltage, and each cell is 10 mV; in the above figure, in the present embodiment, the transmitting current i(t) is turned off, and the receiving coil n= 2 induced voltage

The transmit current turn-off time is 30μs;

4. The calculation of the primary field induced voltage during the forward and reverse turn-off of the transmit current:

Calculate the primary field induced voltage u _{AB1 of the} receiving coil group:

As shown in Figure 10, the above figure shows the induced voltage generated by the receiving coil. The transmitting current i(t) is positively decreased and turned off. The induced voltage of the receiving coil is shown.

The horizontal axis is time t, each cell is 20 μs, and the vertical axis is voltage, and each cell is 10 mV.

The following figure shows the voltage output from the receiving coil group; the transmitting current i(t) is forward-decreasing and the switching-off starts, and the receiving coil group output voltage

The horizontal axis is time t, each cell is 20 μs, and the vertical axis is voltage, and each cell is 50 mV.

By comparison, during the current off period, the device of the present invention receives the signal of the primary field very small, eliminating the strong primary field background, and achieving the purpose of effectively receiving the secondary field transient signal generated by the underground geological body.

Embodiment 2, applied to the frequency domain electromagnetic method, is performed in the following sequential steps;

1. The transmitting coil and the receiving coil group designed in Embodiment 1 are obtained according to the second step of Embodiment 1.

ψ _m1 ≈1.5149×10 ^-9 i(t)(Wb)

2. Start the transmitter and send a sinusoidal current as shown in Figure 11. In Figure 11, the horizontal axis is time t, each cell is 0.02 ms; the vertical axis is current, and each cell is 1 A;

The signal is the transmission current in the second embodiment, the frequency of the transmission current is 10000 Hz, and the transmission current is measured by the current sensor. The conversion ratio of the current sensor is 100 mV/A, so the peak value of the transmission current is 5.8 A. Approximate sinusoidal current expression: i(t)=5.5×cos(20000πt)(A);

3. Calculate the primary field induced voltage of the inner receiving coil

Get:

In Figure 12: the horizontal axis is time t, each cell is 20 μs; the vertical axis is voltage, each cell is 20 mV;

The above figure is the second embodiment, the transmission current i(t) starts to turn off, and the induced voltage of the receiving coil

The following figure shows the induced voltage of the receiving coil n starting from the forward turn-off of the transmitting current i(t) in the second embodiment.

As shown in Figure 13, the above figure shows the induced voltage generated by the receiving coil. The following figure shows the voltage u ₀ (t) after the output voltage u(t) of the receiving coil group is amplified by 1 time;

By comparison, during the current turn-off period, the primary field signal received by the device of the present invention is weak, eliminating the strong primary field background.

Embodiment 3, applied to the time domain electromagnetic method, is performed in the following sequence steps:

1. Design of transmitting coil and receiving coil:

As shown in FIG. 14, at the plane selection center point O, the design transmission coil 2 is a 20-inch square solenoid; the square side length is 300 mm, the line width is 2 mm, and the line-to-line distance is 3 mm;

The design sub-receiving coil is a 300-inch square solenoid; the square side length is 110 mm, the line width is 2 mm, and the line-to-line distance is 1.8 mm;

2. Calculate the magnetic flux ψ _m1 that the inner receiving coil 1 passes under the action of one field:

Get: ψ _m1 ≈2.3149×10 ^-9 i(t)(Wb)

Where: l ₁ : the side length of each coil of the sub-receiving coil; x: the x coordinate of a point of the i-th coil plane of the sub-receiving coil; y: the y coordinate of a point of the i-th coil plane of the sub-receiving coil; z: sub The z coordinate of a point on the i-th coil plane of the receiving coil; z _k : the z coordinate of a point on the _k- th coil of the transmitting coil 1, the symbol appearing in the following formula has the same meaning; L: the length of the side of the transmitting coil 1 , the symbol appearing in the following formula has the same meaning;

The arc through which the current of one side of the coil 1 of the transmitting coil 1 passes, and the symbol appearing in the following formula has the same meaning;

3. Start the transmitter and send the bipolar square wave current as shown in Figure 15. The horizontal axis is time t, each cell is 0.02 ms; the vertical axis is current, and each cell is 1 A. Among them, the current waveform is measured by a current sensor, and the conversion ratio of the current sensor is 100 mV/A, so the peak value of the transmission current is 7.1 A. According to FIG. 15, the transmission current off time is 30 μs;

In Figure 16: the horizontal axis is time t, each cell is 20 μs; the vertical axis is voltage, each cell is 20 mV;

The figure above shows the induced voltage of the receiving coil starting from the forward turn-off of the transmitting current i(t) in the third embodiment.

The following figure shows the induced voltage of the receiving coil n starting from the forward turn-off of the transmitting current i(t) in the third embodiment.

4. The calculation of the primary field induced voltage during the forward and reverse turn-off of the transmit current:

Calculate the primary field induced voltage of the receiving coil group

As shown in Figure 17, the above figure shows the induced voltage waveform generated by the receiving coil. The following figure shows the voltage u(t) output from the receiving coil group. By comparison, during the current turn-off, the strong primary field background is eliminated and the effective receiving is achieved. The purpose of early secondary field transient signals generated by subterranean geological bodies.

The technical solution of the invention is not only suitable for geophysical exploration, engineering geological exploration, but also for detecting underground military targets and non-destructive testing.

Embodiment 4, applied to the time domain electromagnetic method, is performed in the following sequence steps:

1. Design of transmitting coil and receiving coil:

As shown in Fig. 7, at the plane selected center point O, the design transmission coil is a 20-inch planar spiral coil, each coil is approximately a circle; the innermost coil has a radius of 400 mm, the outermost coil has a radius of 460 mm, and the line width is 2.5 mm. , the distance between lines is 0.5mm;

Design comparison experiment: (1) Seven sub-receiving coils form a receiving coil group, each sub-receiving coil is a 300-turn spiral coil, each coil is approximately a circle; the innermost coil has a radius of 100.5 mm, and the outermost coil has a radius of 120.5 mm. The width is 0.5mm, and the distance between lines is 0.5mm;

(2) Only one receiving coil is a 2100-turn spiral coil, each coil is approximately a circle; the innermost coil has a radius of 100.5 mm, the outermost coil has a radius of 160.5 mm, the line width is 0.5 mm, and the line-to-line distance is 0.5 mm;

2. Start the transmitter and send the current as shown in Figure 8. The current waveform is measured by the current sensor. The conversion ratio is 100mV/A, so the current amplitude is 7.1A. According to Figure 9, the transmission current turn-off time is 30μs;

3. During the positive fall of the transmit current, the secondary field output voltage is observed as shown in Figure 20:

The solid line voltage curve is the output voltage of the distributed receiving coil, and the dotted line voltage curve is the voltage output by a single 2100 匝 receiving coil;

By comparison, since the self-inductance coefficient of the receiving coil group is only 427.1mH, which is much smaller than the self-inductance 2.0248H of the single effective coil of the same effective area, it has better signal sensitivity and is beneficial to realize the reception of the secondary generated by the underground geological body. The purpose of the field transient signal.

Claims (10)

1. A field weak coupling receiving device for electromagnetic method exploration, comprising a transmitter (1), a transmitting coil (2), a signal conditioning module (4) and a receiver (5), and two transmitting outputs of the transmitter (1) The terminal is connected to both ends of the transmitting coil (2), characterized in that it further comprises n receiving coils, the n receiving coils constitute a receiving coil module (3), the receiving coil module (3) and the The signal conditioning module (4) is connected, and the output group of the signal conditioning module (4) is connected to the receiver (5);

   A receiving coil module (3) is disposed at an edge of the transmitting coil (2), the two of which partially intersect, a partial orthographic projection of the transmitting coil (2) and a partial orthographic projection of the receiving coil module (3) coincide.
2. The primary field weak coupling receiving apparatus of the electromagnetic method according to claim 1, characterized in that the magnetic flux emitted by the transmitting coil (2) through which the receiving coil module (3) receives the coil is adjustable.
3. The field weak coupling receiving device of the electromagnetic method according to claim 1, wherein the receiving coil module (3) is a receiving coil array, and the receiving coil array is composed of n independent receiving n receiving coils. All receiving coil wires are wound in the same direction.
4. A field weak coupling receiving apparatus for electromagnetic survey according to claim 3, wherein said signal conditioning module (4) comprises n independent signal conditioning circuits, each of said receiving coils being connected to an independent signal conditioning circuitry, a _m and the positive input terminal corresponding to the signal conditioning circuit connected to the receiving coil starting end, the end of the receiving coil and the terminal B _m corresponding to the reference terminal is connected to the signal conditioning circuit.
5. The field weak coupling receiving device of the electromagnetic method according to claim 1, wherein the signal conditioning module (4) comprises a signal conditioning circuit, and all of the receiving coils are sequentially connected in series, wherein the first receiving coil The starting end A _{1 is} connected to the positive input end of the signal conditioning circuit, and the end receiving end point B _n of the receiving coil is connected to a reference end corresponding to the signal conditioning circuit.
6. An electromagnetic survey method of claim 5 weakly coupled primary field receiving apparatus, as claimed in claim wherein: one of said n receiving coils, the transmitting coil in an edge (2) of said n receive coils ₁ are arranged uniformly Wherein the n ₁ receiving coils partially intersect the transmitting coil (2); n ₂ receiving coils are completely located in the transmitting coil (2); n ₃ receiving coils are completely outside the transmitting coil (2) Wherein n ₁ , n ₂ , and n ₃ are integers greater than or equal to 0, and n ₁ + n ₂ + n ₃ = n.
7. The field weak coupling receiving device of the electromagnetic method according to claim 5, wherein the receiving coil is a strip coil, the strip coil is annular, and is disposed around an edge of the transmitting coil (2) The two portions are partially intersected, and a partial orthographic projection of the transmitting coil (2) coincides with a partial orthographic projection of the strip coil.
8. The primary field weakly coupled receiving apparatus of the electromagnetic method according to claim 4 or 5, wherein the signal conditioning circuit comprises a damping resistor R ₀ , a voltage follower A ₁ , an operational amplifier A ₂ , and an input resistor R ₁ and a feedback resistor R ₂ ; one end of the damping resistor R ₀ serves as a reference end of the signal conditioning circuit, the reference terminal is grounded, and the other end of the damping resistor R _{0 is} in phase with the voltage follower A ₁ input terminal, the noninverting input terminal of the voltage follower a ₁ as the signal conditioning circuit is a positive input terminal, an output terminal of the voltage follower a _1-inverting input terminal of the voltage follower is connected to a _1; the a ₁ output terminal of said voltage follower is connected to one end of the input resistors R _1, the input terminal of the inverting input terminal of the other resistors R ₁ of the operational amplifier a ₂ is connected to the operational amplifier a _n-2 input is connected to the reference terminal, the output of the operational amplifier a ₂ is connected via the ₂ and a ₂ of the inverting input terminal of the operational amplifier feedback resistor R, the output of the operational amplifier a ₂ and the a positive receiver (5) The terminal is connected, the reference terminal of the signal conditioning circuit and the receiver (5) connected to a common reference terminal.
9. An independent surveying method for a field weak coupling receiver of an electromagnetic method according to any one of claims 1 to 4, characterized in that: S1: activating the transmitter (1) to the transmitting coil ( 2) pass current i(t);

   S2: calculated m-th receiving coil of the primary field flux _{ψ m1 (m = 1,2, ...} , n)

   

   Where: N ₁ : total number of turns of the transmitting coil (2); N _m : total number of turns of the mth receiving coil; k: summation variable of the transmitting coil (2); i: summation of the mth receiving coil Variable; μ ₀ : vacuum permeability, μ ₀ = 4π × 10 ^-7 H / m; i (t): current through the transmitting coil (2); θ _mki : the mth receiving coil, the i-th coil plane and The angle of the normal direction of the k-th coil of the transmitting coil (2); l _1k : the path of the k-th coil of the transmitting coil (2);

   

   a line element vector on the kth coil of the transmitting coil (2);

   

   The mth receiving coil, the i-th coil plane, and the transmitting coil 1, the kth coil element vector

   

   Relative position vector; R _mki : a certain point of the mth receiving coil, the i-th coil plane, and the k-th coil element vector of the transmitting coil 1

   

   a mode of the relative position vector; S _mi : a planar range of the mth receiving coil of the i-th coil;

   

   a plane bin vector of the mth receiving coil ith coil; S3: adjusting the size of the n receiving coils and the relative position of the transmitting coils (2) so that the primary field fluxes of the n receiving coils ψ _m1 =0; S4: Calculate the magnetic flux ψ _m2 (m=1, 2..., n) through the mth receiving coil under the action of the secondary field:

   

   Where: B(t): secondary field magnetic induction; S _mi : area of the i-th coil of the mth receiving coil; α _mi : direction of the first direction of the coil and the direction of the secondary field magnetic induction of the coil m Angle; S5: calculating the induced voltage of the mth receiving coil

   

   

   among them:

   

   a field induced voltage between the start and end points of the mth receiving coil;

   

   a secondary field induced voltage between the start and end points of the mth receiving coil; S6: obtained in combination with step S3

   

   Then the induced voltage of the n receiving coils

   

   for:

   
10. A tandem surveying method for a field weak coupling receiver of an electromagnetic method according to any one of claims 1 or 2 or 5 or 6 or 7, characterized in that: S1: starting the transmitter (1), Passing the transmitting coil (2) with current i(t); S2: calculating the primary field flux ψ _{m1 of} the mth receiving coil (m=1, 2, . . . , n)

    

    Where: N ₁ : total number of turns of the transmitting coil (2); N _m : total number of turns of the mth receiving coil; k: summation variable of the transmitting coil (2); i: summation of the mth receiving coil Variable; μ ₀ : vacuum permeability, μ ₀ = 4π × 10 ^-7 H / m; i (t): current through the transmitting coil (2); θ _mki : the mth receiving coil, the i-th coil plane and The angle of the normal direction of the k-th coil of the transmitting coil (2); l _1k : the path of the k-th coil of the transmitting coil (2);

    

    a line element vector on the kth coil of the transmitting coil (2);

    

    The mth receiving coil, the i-th coil plane, and the transmitting coil 1, the kth coil element vector

    

    Relative position vector; R _mki : a certain point of the mth receiving coil, the i-th coil plane, and the k-th coil element vector of the transmitting coil 1

    

    a mode of the relative position vector; S _mi : a planar range of the mth receiving coil of the i-th coil;

    

    a plane bin vector of the mth receiving coil ith coil; S3: adjusting the size of the n receiving coils and the relative position of the transmitting coil (2) so that the primary field flux of the n receiving coils

    

    S4: Calculate the magnetic flux ψ _m2 (m=1, 2..., n) passing through the mth receiving coil under the action of the secondary field:

    

    Where: B(t): secondary field magnetic induction; S _mi : area of the i-th coil of the mth receiving coil; α _mi : direction of the first direction of the coil and the direction of the secondary field magnetic induction of the coil m Angle; S5: calculating the induced voltage of the mth receiving coil

    

    

    among them:

    

    a field induced voltage between the start and end points of the mth receiving coil;

    

    a secondary field induced voltage between the start and end points of the mth receiving coil; S6: obtained in combination with step S3

    

    Then the induced voltage of the n receiving coils

    

    for:

    

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