Air natural electric field frequency selection detection method and system

Abstract

The invention relates to the technical field of geological exploration, in particular to an air natural electric field frequency selection detection method and system. A capacitance detector is adopted to replace a potentiometer for measurement, and the capacitance detector is adopted to directly observe the horizontal electric field component of an electric field in the x direction of a measuring line in the earth surface air at an exploration point; the size of the horizontal electric field component is equal to the ratio of the observation value of the original potentiometer to the distance between two adjacent detection points, and the tangential components of the electric field intensity on the two sides of the dielectric interface are continuous; therefore, the control host obtains the actual potential difference corresponding to each exploration point based on the observation potential difference corresponding to each exploration point, subsequently determines the potential curve graph of the to-be-measured area based on the actual potential difference corresponding to each exploration point under different set frequencies, and carries out exploration analysis on the underground geological condition of the to-be-measured area through the potential curve graph. In the whole process, a detection electrode does not need to be embedded into a detection point, and a capacitance detector is directly placed at each exploration point on the ground surface.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of geological exploration, in particular to an aerial natural electric field frequency selection detection method and system. BACKGROUND

[0002] The natural electric field frequency selection sounding method is an important geophysical exploration method. The uneven distribution of electric charges on the earth's surface and inside will form a natural electric field. For example, the oxidation and reduction effect of the contact surface between the electronic conductor and the solution, the seepage and filtration effect of the underground water, and the ion diffusion of the mineralized solution and the adsorption effect of the rock skeleton will all generate an electric field. Based on the resistivity and other physical differences of the underground rock and ore, the variation law of the electric field components of multiple different frequencies generated by the ground electromagnetic field is measured on the ground, and the characteristics of different frequencies of electromagnetic waves in the conductor are used to change the detection depth by changing the working frequency.

[0003] The existing natural electric field frequency selection method needs to detect along the survey line (or profile), embed the detection electrodes into the ground, and then move the detection electrodes forward synchronously to detect the horizontal potential difference of multiple different frequencies, record the midpoint between the two detection electrodes, and generate the potential curve diagram corresponding to multiple different frequencies based on the midpoint and the potential difference. However, when the frequency selection method is used to detect on the hardened surface such as cement, asphalt, and exposed rock surface, the detection electrodes cannot be smoothly inserted into the underground, resulting in the inability to conduct geological exploration. SUMMARY

[0004] The main purpose of the present application is to provide an aerial natural electric field frequency selection detection method and system, which aims to solve the problem that the detection electrodes cannot be smoothly inserted into the underground when the frequency selection method is used to detect on the hardened surface such as cement, asphalt, and exposed rock surface, resulting in the inability to conduct geological exploration.

[0005] The technical solution provided by the present application is as follows: An aerial natural electric field frequency selection detection method is applied to an aerial natural electric field frequency selection detection system. The system includes a control host and a capacitive detector. The capacitive detector includes a first clamping plate and a second clamping plate parallel to each other, and an insulating layer is arranged between the first clamping plate and the second clamping plate. A first conductive foil is arranged between the first clamping plate and the insulating layer, and a second conductive foil is arranged between the second clamping plate and the insulating layer. The first conductive foil and the second conductive foil are electrically connected to the control host. The method comprises the following steps: Artificially determining the detection points and the exploration points of the to-be-detected area, wherein the multiple detection points are arranged at equal intervals and in a straight line in the to-be-detected area, and the midpoint between the adjacent two detection points is the exploration point. The capacitive probe is placed in each exploration point in sequence from front to back and close to the ground surface, wherein, when the capacitive probe is placed in each exploration point, the first clamping plate and the second clamping plate are both vertically arranged, and the first clamping plate is perpendicular to the direction of the connecting line of each exploration point; When the capacitive probe is placed in each exploration point, the control host obtains the potential difference between the first clamping plate and the second clamping plate at multiple different set frequencies through the first conductive foil and the second conductive foil, and marks as the observed potential difference corresponding to each exploration point; The control host obtains the actual potential difference corresponding to each exploration point based on the observed potential difference corresponding to each exploration point; The control host determines the potential curve of the to-be-measured region based on the actual potential difference corresponding to each exploration point at different set frequencies.

[0006] Preferably, the areas of the first clamping plate and the second clamping plate are consistent; the control host obtains the actual potential difference corresponding to each exploration point based on the observed potential difference corresponding to each exploration point, comprising: The control host calculates the capacitance of the capacitive probe: (1), In the formula, is the capacitance of the capacitive probe; is the dielectric constant of the insulating layer; d is the distance between the first clamping plate and the second clamping plate; S is the area of the first clamping plate; The control host sets the internal resistance of the capacitive probe to 2R, and calculates the voltage of the capacitive probe: (2), In the formula, U is the voltage of the capacitive probe; is the horizontal electric field component measured by the capacitive probe.

[0007] Preferably, the control host sets the internal resistance of the capacitive probe to 2R, and calculates the voltage of the capacitive probe, and then further comprises: The control host simultaneously solves formula (1) and formula (2) to calculate the charge quantity of the capacitive probe: (3), In the formula, Q is the charge quantity of the capacitive probe; The control host sets the charge quantity measured by the capacitive probe in a preset time period to be , and calculates the current of the capacitive probe: (4), In the formula, j is the current of the capacitive probe; is the horizontal electric field component measured by the capacitive probe in a preset time period .

[0008] Preferably, the control host sets the capacitance detector to operate for a preset time period. The internally measured charge is Calculate the current of the capacitive detector, and then include: The control host calculates the potential difference between the first clamping plate and the second clamping plate: (5), In the formula, The potential difference between the first and second clamping plates; The control host substitutes formula (4) into formula (5) to obtain: (6), The propagation of the natural electromagnetic waves of the control host varies with the sampling time. Obey the harmonic variation law, let To transform formula (6): (7), In the formula, i is the imaginary unit. ; It is the angular frequency. , f The frequency is set; A is the amplitude of the horizontal electric field component.

[0009] Preferably, the propagation of the natural electromagnetic wave of the control host varies with the sampling time. Obey the harmonic variation law, let To transform formula (6), the following is also included: The control host sets the electric field between two adjacent detection points of the exploration point to a uniform field, and the electric field between two adjacent detection points of the exploration point is... To calculate the actual potential difference between two adjacent detection points at an exploration point: (8), In the formula, MN represents the actual potential difference between two adjacent detection points; MN represents the distance between two adjacent detection points. The control host command = Substituting formula (7) into formula (8), we get: (9), The control host uses the actual potential difference between two adjacent detection points as the actual potential difference between the two detection points and the exploration point. The control host divides both sides of formulas (7) and (9) respectively to obtain the observed potential difference corresponding to each exploration point. Actual potential difference corresponding to each exploration point The ratio between them: (10).

[0010] Preferably, the control host divides both sides of formula (7) and formula (9) respectively to obtain the observed potential difference corresponding to each exploration point. Actual potential difference corresponding to each exploration point The ratio between them, and then includes: The control host obtains the actual potential difference corresponding to each exploration point based on formula (10) and the observed potential difference corresponding to each exploration point.

[0011] Preferably, the control host determines the potential curve of the area to be measured based on the actual potential difference corresponding to each exploration point at different set frequencies, including: The control host determines the potential curve of the area to be measured based on the actual potential difference corresponding to each exploration point under different set frequencies. The potential curve includes multiple potential curves. The x-axis of the potential curve is the horizontal position of each exploration point, and the y-axis is the actual potential difference corresponding to each exploration point. The control host determines whether there is a good electrical conductor underground in the area to be tested based on the potential curve.

[0012] Preferably, the number of potential curves is the same as the number of set frequencies, and the potential curves correspond one-to-one with the set frequencies; different set frequencies correspond to different detection depths.

[0013] This invention also proposes a frequency-selective detection system for natural electric fields in the air, applying a frequency-selective detection method for natural electric fields in the air; the system includes a control host and a capacitor detector; the capacitor detector includes a first clamping plate and a second clamping plate that are parallel to each other, with an insulating layer disposed between the first clamping plate and the second clamping plate; a first conductive foil is disposed between the first clamping plate and the insulating layer, and a second conductive foil is disposed between the second clamping plate and the insulating layer; both the first conductive foil and the second conductive foil are electrically connected to the control host.

[0014] The above technical solution can achieve the following beneficial effects: The frequency-selective detection method for natural electric fields proposed in this invention solves the problem that when conducting frequency-selective detection on hardened surfaces such as cement and asphalt, as well as exposed rock surfaces, the detection electrodes cannot be smoothly inserted into the ground, thus hindering geological exploration. In this application, a capacitive detector is used instead of a potentiometer for measurement. The capacitive detector directly observes the horizontal electric field component along the x-direction of the measurement line in the air at the exploration point. The magnitude of the horizontal electric field component is equal to the ratio of the original potentiometer observation value (potential difference) to the distance between two adjacent detection points. This is because the tangential component of the electric field intensity on both sides of the medium interface is continuous. Therefore, the main unit obtains the actual potential difference corresponding to each exploration point based on the observed potential difference. Subsequently, the potential curve of the area to be measured can be determined based on the actual potential difference corresponding to each exploration point at different set frequencies. The underground geological conditions of the area to be measured can be explored and analyzed through the potential curve. The entire process does not require the use of detection electrodes embedded in the detection points; the capacitive detector can be directly placed at each exploration point on the ground surface. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0016] Figure 1 This is a flowchart of the first embodiment of the frequency-selective detection method for natural electric fields in the air proposed in this invention; Figure 2 This is a schematic diagram of the structure of a capacitor detector in the first embodiment of the frequency-selective detection method for natural electric fields in the air proposed in this invention; Figure 3 This is a schematic diagram showing the arrangement of the capacitor detector in use during the first embodiment of the frequency-selective detection method for natural electric fields in the air proposed in this invention. Figure 4 This is a schematic diagram of the natural electric field distribution in the first embodiment of the frequency-selective detection method for natural electric fields in the air proposed in this invention. Figure 5 This is a schematic diagram of the capacitor inductive charging principle in the sixth embodiment of the frequency-selective detection method for natural electric fields in the air proposed in this invention; Figure 6 This is a schematic diagram of the electric field distribution of the electric field detector in the sixth embodiment of the frequency-selective detection method for natural electric fields in the air proposed in this invention. Detailed Implementation

[0017] It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of the invention.

[0018] This invention proposes a frequency-selective detection method and system for natural electric fields in the air.

[0019] As attached Figure 1 As shown, in the first embodiment of the frequency-selective detection method for natural electric fields in the air proposed in this invention, the frequency-selective detection method for natural electric fields in the air is applied to a frequency-selective detection system for natural electric fields in the air; the system includes a control host and a capacitor detector; the capacitor detector includes a first clamping plate and a second clamping plate that are parallel to each other, and an insulating layer is disposed between the first clamping plate and the second clamping plate; a first conductive foil is disposed between the first clamping plate and the insulating layer, and a second conductive foil is disposed between the second clamping plate and the insulating layer; the structure of the capacitor detector is shown in the attached figure. Figure 2 As shown; both the first conductive foil and the second conductive foil are electrically connected to the control host; this embodiment includes the following steps: Step S110: Manually determine the detection points and exploration points in the area to be tested. Multiple detection points are evenly spaced and arranged in a straight line within the area to be tested, and the midpoint between two adjacent detection points is the exploration point.

[0020] Step S120: Place the capacitive detectors at each exploration point in order from front to back and close to the ground surface. When the capacitive detectors are placed at the exploration points, the first clamp and the second clamp are both set vertically, and the first clamp is perpendicular to the line connecting each detection point.

[0021] As attached Figure 3 As shown in the figure, MN are two adjacent detection points, and the middle point O is the exploration point.

[0022] Step S130: When the capacitive detector is placed at each exploration point, the control host obtains the potential difference between the first clamp and the second clamp at multiple different set frequencies through the first conductive foil and the second conductive foil, and marks it as the observation potential difference corresponding to each exploration point.

[0023] Step S140: The control host obtains the actual potential difference corresponding to each exploration point based on the observed potential difference corresponding to each exploration point.

[0024] Step S150: The control host determines the potential curve of the area to be measured based on the actual potential difference corresponding to each exploration point under different set frequencies.

[0025] The frequency-selective detection method for natural electric fields in the air proposed in this invention solves the problem that when conducting frequency-selective detection on hardened surfaces such as cement and asphalt, as well as exposed rock surfaces, the detection electrodes cannot be smoothly inserted into the ground, thus preventing geological exploration. In this application, a capacitive detector is used instead of a potentiometer for measurement. The capacitive detector directly observes the horizontal electric field component along the x-direction of the measurement line in the air at the exploration point. The magnitude of the horizontal electric field component is equal to the ratio of the original potentiometer observation value (potential difference) to the distance between two adjacent detection points. This is because the tangential component of the electric field intensity on both sides of the medium interface is continuous. Therefore, the control host obtains the actual potential difference corresponding to each exploration point based on the observed potential difference. Subsequently, the control host can determine the potential curve of the area to be measured based on the actual potential difference corresponding to each exploration point at different set frequencies. The underground geological conditions of the area to be measured can be explored and analyzed through the potential curve. The entire process does not require the use of detection electrodes to embed into the detection points; the capacitive detector can be directly placed at each exploration point on the ground surface.

[0026] Compared with the prior art, this application has the following advantages: 1. The field source is a natural field, and there are no power supply electrodes A and B or their power supply equipment in the equipment. Compared with the traditional resistivity method, the equipment is lightweight.

[0027] 2. When conducting conventional natural electric field frequency selection detection on hardened surfaces such as cement and asphalt, as well as on exposed rock surfaces, there is no need to insert underground detection electrodes as in conventional frequency selection methods, thus avoiding the difficulties of construction on hardened surfaces.

[0028] 3. It does not require electrode wires of 10m (or 20m) or the space for electrode arrangement, and can carry out frequency-selective detection in confined spaces (such as factories, towns and other densely populated areas), while also being more efficient.

[0029] 4. Compared with the magnetic field frequency selection method, since this system observes the electric field component in the air, it avoids the defect that the observed magnetic field component is easily affected by human electromagnetic interference.

[0030] 5. The use of a capacitor detector to observe the electric field eliminates the errors caused by the inaccurate electrode spacing and the relative height difference between the two detector electrodes in the conventional natural electric field frequency selection method, thus improving the detection accuracy.

[0031] As attached Figure 4 As shown, n represents the surface normal unit vector, and t represents the surface tangential unit vector; the potential difference between the two points M and N is observed by the probe points. The horizontal component of the electric field intensity in the underground medium at exploration point O can be obtained. ,Right now ; This represents the horizontal electric field component in the air at exploration point O, directly observed using a capacitive sensor. According to the boundary conditions for electromagnetic wave propagation, the tangential component of the electric field intensity is continuous, i.e., the horizontal electric field component measured in the air at exploration point O. The horizontal electric field component in the underground medium between detection points M and N, measured using detection electrodes, should be considered. They are equal, therefore, Therefore, it can be seen that using a capacitance detector to measure the electric field component in the air above the Earth's surface is effective. It can replace the original natural electric field frequency selection method and adopt the observation method of detection electrodes.

[0032] In the second embodiment of the frequency-selective detection method for natural electric fields in the air proposed in this invention, based on the first embodiment, the areas of the first clamping plate and the second clamping plate are the same; step S140 includes the following steps: Step S210: The control host calculates the capacitance of the capacitance detector: (1), In the formula, The capacitance of the capacitor detector; denoted as ρ, where d is the dielectric constant of the insulating layer; d is the distance between the first and second clamping plates; and S is the area of ​​the first clamping plate.

[0033] Step S220: The control host sets the internal resistance of the capacitive detector to 2R and calculates the voltage of the capacitive detector: (2), In the formula, U is the voltage of the capacitive detector; This represents the horizontal electric field component measured by the capacitive detector.

[0034] In the third embodiment of the frequency-selective detection method for natural electric fields in the air proposed in this invention, based on the second embodiment, step S220 is followed by the following steps: Step S310: The control host combines formulas (1) and (2) to calculate the charge of the capacitive detector: (3), In the formula, Q is the charge of the capacitive detector.

[0035] Step S320: The control host sets the capacitance detector to operate for a preset time. The internally measured charge is Calculate the current of the capacitive detector: (4), In the formula, j is the current of the capacitive detector; For the capacitive detector at a preset time The measured horizontal electric field components.

[0036] In the fourth embodiment of the frequency-selective detection method for natural electric fields in the air proposed in this invention, based on the third embodiment, after step S320, the following steps are further included: Step S410: The control host calculates the potential difference between the first clamping plate and the second clamping plate: (5), In the formula, This represents the potential difference between the first and second clamping plates.

[0037] Step S420: The control host substitutes formula (4) into formula (5) to obtain: (6), Step S430: The propagation of the natural electromagnetic wave of the control host varies with the sampling time. Obey the harmonic variation law, let To transform formula (6): (7), In the formula, i is the imaginary unit. ; It is the angular frequency. , f The frequency is set; A is the amplitude of the horizontal electric field component.

[0038] In the fifth embodiment of the frequency-selective detection method for natural electric fields in the air proposed in this invention, based on the fourth embodiment, after step S430, the following steps are further included: Step S510: The control host sets the electric field between two adjacent detection points of the exploration point to a uniform field, and the electric field between two adjacent detection points of the exploration point is... To calculate the actual potential difference between two adjacent detection points at an exploration point: (8), In the formula, MN represents the actual potential difference between two adjacent detection points; MN represents the distance between two adjacent detection points.

[0039] Step S520: The control host command = Substituting formula (7) into formula (8), we get: (9), Step S530: The control host uses the actual potential difference between two adjacent detection points as the actual potential difference between the exploration points.

[0040] Step S540: The control host divides both sides of formula (7) and formula (9) respectively to obtain the observed potential difference corresponding to each exploration point. Actual potential difference corresponding to each exploration point The ratio between them: (10).

[0041] Specifically, the above formula (10) is the basic principle formula for using an air capacitor detector to replace the ground electrodes M and N for natural electric field frequency selection detection.

[0042] In the sixth embodiment of the frequency-selective detection method for natural electric fields in the air proposed in this invention, based on the fifth embodiment, after step S540, the following steps are further included: Step S610: The control host obtains the actual potential difference corresponding to each exploration point based on formula (10) and the observed potential difference corresponding to each exploration point.

[0043] As attached Figure 5 As shown, the first and second clamps of the capacitive detector are in a uniform electric field. In this case, if all the charge migrates, there will be no electric field within a single capacitor plate; only the electric field remains. , making If the wire connection is disconnected at this time, the capacitor will be fully charged.

[0044] As attached Figure 6 As shown, if two parallel plates are placed in an alternating electromagnetic field, with a certain medium filling the space between them, the two parallel plates will be alternately charged and discharged due to the continuous change of the alternating electric field. Before the electric field alternates... As the electric field decays, the charge also begins to flow in the opposite direction at its maximum value. In other words, the current begins to flow in the opposite direction as soon as the electric field begins to decay.

[0045] If a highly sensitive ammeter A is connected to the two ends of two capacitor plates located in an alternating electric field, the magnitude of the capacitor plates charging and discharging can be read, thereby calculating the voltage and electric field in the air. Figure 6 This is a schematic diagram of the basic model for detecting electric fields using the frequency-selective method with natural electric fields in the air. The charge is calculated from the current, and then the voltage U and the external electric field can be obtained using the capacitance formula. .

[0046] In the seventh embodiment of the frequency-selective detection method for natural electric fields in the air proposed in this invention, based on the first embodiment, step S150 includes the following steps: Step S710: The control host determines the potential curve of the area to be measured based on the actual potential difference corresponding to each exploration point under different set frequencies. The potential curve includes multiple potential curves. The x-axis of the potential curve is the horizontal position of each exploration point, and the y-axis of the potential curve is the actual potential difference corresponding to each exploration point.

[0047] Step S720: The control host determines whether there is a good conductor underground in the area to be tested based on the potential curve.

[0048] Specifically, potential difference can reflect the underground geological conditions of two detection points (i.e., exploration points). When an electric field propagates underground, it encounters geological bodies with different resistivity, causing changes in the electric field components. For example, metallic ore bodies typically have low resistivity, while the surrounding rocks have relatively high resistivity. In this case, when the electric field passes through the ore body, the current flows more easily within it, causing changes in the electric field components around the ore body. By comparing the changes in potential difference, it is possible to infer the existence of low-resistivity geological bodies underground, and thus, the possible presence of metallic mineralization areas. Conversely, high-resistivity geological bodies (such as certain granite bodies) will impede the electric field, causing specific patterns of change in the electric field components around them; therefore, the underground geological conditions of the exploration point can be reflected through potential difference curves.

[0049] In the eighth embodiment of the frequency-selective detection method for natural electric fields in the air proposed in this invention, based on the seventh embodiment, the number of potential curves is consistent with the number of set frequencies, and the potential curves and set frequencies correspond one-to-one; different set frequencies correspond to different detection depths.

[0050] This invention also proposes a frequency-selective detection system for natural electric fields in the air, applying a frequency-selective detection method for natural electric fields in the air; the system includes a control host and a capacitor detector; the capacitor detector includes a first clamping plate and a second clamping plate that are parallel to each other, with an insulating layer disposed between the first clamping plate and the second clamping plate; a first conductive foil is disposed between the first clamping plate and the insulating layer, and a second conductive foil is disposed between the second clamping plate and the insulating layer; both the first conductive foil and the second conductive foil are electrically connected to the control host.

[0051] The sequence numbers of the above embodiments of the present invention are for descriptive purposes only and do not represent the superiority or inferiority of the embodiments.

[0052] The embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of the present invention without departing from the spirit and scope of the claims. All of these forms are within the protection scope of the present invention.

Claims

1. A method for frequency-selective detection of natural electric fields in the air, characterized in that, An application is made in a frequency-selective detection system for natural electric fields in the air; the system includes a control host and a capacitor detector; the capacitor detector includes a first clamping plate and a second clamping plate that are parallel to each other, with an insulating layer disposed between the first clamping plate and the second clamping plate; a first conductive foil is disposed between the first clamping plate and the insulating layer, and a second conductive foil is disposed between the second clamping plate and the insulating layer; The first conductive foil and the second conductive foil are both electrically connected to the control host; the method includes: The detection points and exploration points in the area to be measured are determined manually. Among them, multiple detection points are equally spaced and arranged in a straight line in the area to be measured, and the midpoint between two adjacent detection points is the exploration point. Capacitive detectors are placed at each exploration point in order from front to back and close to the ground surface. When the capacitive detector is placed at the exploration point, the first clamp and the second clamp are both set vertically, and the first clamp is perpendicular to the line connecting each detection point. When the capacitive detector is placed at each exploration point, the control host obtains the potential difference between the first clamp and the second clamp at multiple different set frequencies through the first conductive foil and the second conductive foil, and marks it as the observation potential difference corresponding to each exploration point. The control host obtains the actual potential difference corresponding to each exploration point based on the observed potential difference corresponding to each exploration point. The control host determines the potential curve of the area to be measured based on the actual potential difference corresponding to each exploration point at different set frequencies.

2. The method for frequency-selective detection of natural electric fields in the air according to claim 1, characterized in that, The first and second clamping plates have the same area; the control host obtains the actual potential difference corresponding to each exploration point based on the observed potential difference, including: The control host calculates the capacitance of the capacitance detector: （1）， In the formula, The capacitance of the capacitor detector; denoted as ρ, where ρ is the dielectric constant of the insulating layer; d is the distance between the first and second clamping plates; and S is the area of ​​the first clamping plate. The control host sets the internal resistance of the capacitive detector to 2R and calculates the voltage of the capacitive detector: （2）， In the formula, U is the voltage of the capacitive detector; This represents the horizontal electric field component measured by the capacitive detector.

3. The method for frequency-selective detection of natural electric fields in the air according to claim 2, characterized in that, The control host sets the internal resistance of the capacitance detector to 2R and calculates the voltage of the capacitance detector. The subsequent steps also include: The control host combines formulas (1) and (2) to calculate the charge of the capacitive detector: （3）， In the formula, Q is the charge of the capacitive detector; The control host sets the capacitance detector to a preset time. The internally measured charge is Calculate the current of the capacitive detector: （4）， In the formula, j is the current of the capacitive detector; For the capacitive detector at a preset time The measured horizontal electric field components.

4. The method for frequency-selective detection of natural electric fields in the air according to claim 3, characterized in that, The control host sets the capacitance detector to a preset time. The internally measured charge is Calculate the current of the capacitive detector, and then include: The control host calculates the potential difference between the first clamping plate and the second clamping plate: （5）， In the formula, The potential difference between the first and second clamping plates; The control host substitutes formula (4) into formula (5) to obtain: （6）， The propagation of the natural electromagnetic waves of the control host varies with the sampling time. Obey the harmonic variation law, let To transform formula (6): （7）， In the formula, i is the imaginary unit. ; It is the angular frequency. , f The frequency is set; A is the amplitude of the horizontal electric field component.

5. The method for frequency-selective detection of natural electric fields in the air according to claim 4, characterized in that, The propagation of the natural electromagnetic waves of the control host varies with the sampling time. Obey the harmonic variation law, let To transform formula (6), the following is also included: The control host sets the electric field between two adjacent detection points of the exploration point to a uniform field, and the electric field between two adjacent detection points of the exploration point is... To calculate the actual potential difference between two adjacent detection points at an exploration point: （8）， In the formula, MN represents the actual potential difference between two adjacent detection points; MN represents the distance between two adjacent detection points. The control host command = Substituting formula (7) into formula (8), we get: （9）， The control host uses the actual potential difference between two adjacent detection points as the actual potential difference between the two detection points and the exploration point. The control host divides both sides of formulas (7) and (9) respectively to obtain the observed potential difference corresponding to each exploration point. Actual potential difference corresponding to each exploration point The ratio between them: （10）。 6. The method for frequency-selective detection of natural electric fields in the air according to claim 5, characterized in that, The control host divides both sides of formulas (7) and (9) respectively to obtain the observed potential difference corresponding to each exploration point. Actual potential difference corresponding to each exploration point The ratio between them, and then includes: The control host obtains the actual potential difference corresponding to each exploration point based on formula (10) and the observed potential difference corresponding to each exploration point.

7. The method for frequency-selective detection of natural electric fields in the air according to claim 1, characterized in that, The control host determines the potential curve of the area to be measured based on the actual potential difference corresponding to each exploration point at different set frequencies, including: The control host determines the potential curve of the area to be measured based on the actual potential difference corresponding to each exploration point under different set frequencies. The potential curve includes multiple potential curves. The x-axis of the potential curve is the horizontal position of each exploration point, and the y-axis is the actual potential difference corresponding to each exploration point. The control host determines whether there is a good electrical conductor underground in the area to be tested based on the potential curve.

8. The method for frequency-selective detection of natural electric fields in the air according to claim 7, characterized in that, The number of potential curves is the same as the number of set frequencies, and there is a one-to-one correspondence between the potential curves and the set frequencies; different set frequencies correspond to different detection depths.

9. A frequency-selective detection system for natural electric fields in the air, characterized in that, The method for selectively detecting natural electric fields in the air as described in any one of claims 1-8 is applied; the system includes a control host and a capacitor detector; the capacitor detector includes a first clamping plate and a second clamping plate that are parallel to each other, and an insulating layer is disposed between the first clamping plate and the second clamping plate; a first conductive foil is disposed between the first clamping plate and the insulating layer, and a second conductive foil is disposed between the second clamping plate and the insulating layer; both the first conductive foil and the second conductive foil are electrically connected to the control host.

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