Ungrounded earth electric field measurement method

Abstract

The invention relates to the technical field of electromagnetic measurement, and discloses an ungrounded earth electric field measurement method, which comprises the following steps of: measuring a vortex magnetic field induced by a variable electric field at a point to be measured through an annular induction coil; converting the vortex magnetic field into an induced voltage signal; performing signal processing on the induced voltage signal; calculating according to the induced voltage signal to obtain a value of a to-be-measured electric field; the to-be-measured electric field is indirectly measured by measuring the vortex magnetic field, electric field measurement at any position and in any direction in the space is achieved in an ungrounded mode, the influence of dielectric distribution, a grounded environment, a grounded electrode and the like on electric field measurement is overcome, and the application field of the electric field measurement device is expanded.

Description

Technical Field

[0001] This invention relates to the field of electromagnetic measurement technology, specifically to a method for measuring the electric field of an ungrounded earth. Background Technology

[0002] Traditional methods for measuring the earth's electric field typically employ the grounding electrode method, which involves placing a pair of electrodes on the earth's surface, measuring the potential difference between the electrodes, and then calculating the electric field strength. While this method is direct, it inevitably introduces the following limitations: (1) This measurement method can only obtain the average electric field between the two electrodes. When the electrode spacing is relatively large and the dielectric between the two electrodes is not uniform, the measured electric field value cannot accurately represent the electric field value at a certain point. (2) When measuring in areas where grounding is difficult, such as cement ground, exposed bedrock, or piles of pebbles, the electrode grounding method cannot be used to measure the electric field; (3) The vertical electric field perpendicular to the horizontal plane is of great significance for geophysical electromagnetic measurement, but it is difficult to measure using the electrode grounding method; (4) When the grounding electrode comes into contact with the earth, polarization will inevitably occur, generating polarization potential that interferes with the measurement of the potential difference between the electrodes. The electrodes themselves also have problems such as drift and aging, which affect the accuracy and precision of the electric field measurement by the grounding method.

[0003] Based on this, the present invention provides a method for measuring the electric field of an ungrounded earth. Summary of the Invention

[0004] The purpose of this invention is to provide a method for measuring the electric field of an ungrounded earth, which indirectly calculates the electric field value by measuring the vortex magnetic field, thus overcoming the limitations of traditional grounding methods.

[0005] The objective of this invention can be achieved through the following technical solutions: A method for measuring the electric field of an ungrounded earth includes the following steps: The vortex magnetic field induced by the changing electric field at the point to be measured is measured by a loop induction coil. The vortex magnetic field is converted into an induced voltage signal; The induced voltage signal is processed. The value of the electric field to be measured is calculated based on the induced voltage signal.

[0006] As a further aspect of the present invention: the annular induction coil is placed at the point to be measured, and its plane is perpendicular to the direction of the electric field to be measured.

[0007] As a further aspect of the present invention, the signal processing includes at least one of resonant amplification, preamplification, filtering, and negative feedback control.

[0008] As a further aspect of the present invention: the process of calculating the value of the electric field to be measured based on the induced voltage signal is as follows: V is the induced voltage, B is the vortex magnetic field, t is time, S is the area of ​​a single turn, N is the number of turns of the coil, and μ r The core permeability, Let B be the derivative of the vortex magnetic field with respect to time t, representing the rate of change of the vortex magnetic field. It means proportional to.

[0009] As a further aspect of the present invention: a device for measuring the electric field of an ungrounded earth, comprising: Ring-shaped induction coil; A resonant capacitor, together with the coil, forms a resonant network; The preamplifier circuit is used to amplify the sensed signal; Filtering circuits are used to filter out noise; Electric field negative feedback network is used to extend the system bandwidth.

[0010] As a further aspect of the present invention: the annular induction coil has a magnetic core, and the magnetic core material is a high permeability material.

[0011] As a further aspect of the present invention: the electric field negative feedback network includes a resistor RF, a resistor R1, and a capacitor C2.

[0012] The beneficial effects of the present invention are as follows: The present invention proposes an ungrounded electric field measurement method that calculates the electric field perpendicular to the plane of the vortex magnetic field by measuring the vortex magnetic field. It can measure the electric field at any point in space, rather than the average value of the electric field over a certain range; since it is an ungrounded measurement, there are no requirements for grounding conditions, and the vertical electric field can be easily measured simply by placing the loop coil horizontally; it completely overcomes the influence of factors such as electrode polarization, drift, and aging on electric field measurement. Attached Figure Description

[0013] The invention will now be further described with reference to the accompanying drawings.

[0014] Figure 1 This is a schematic diagram of the structure for measuring the ungrounded electric field of the vortex magnetic field plane of the present invention; Figure 2 This is a schematic diagram of the structure of the ring induction coil of the present invention; Figure 3 This is a schematic diagram of the structure implementing the electric field to be measured in this invention; Figure 4 This is a schematic diagram of the amplitude-frequency response curve of the resonant network of the present invention; Figure 5 This is a schematic diagram of the parallel plate capacitor of the present invention. Detailed Implementation

[0015] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0016] Example 1 This invention proposes an ungrounded electric field measurement method that indirectly measures the magnitude of the changing electric field (displacement current) perpendicular to the plane at a point by measuring the magnitude of the changing magnetic field of a vortex on a closed curve passing through a point in space. This solves the problem in general earth electric field measurements that can only obtain the average electric field value at the distance between the electrodes and cannot obtain the electric field value at a specific point. In areas where grounding is difficult, it is hard to calculate the magnitude of the electric field by measuring the potential difference between two electrodes through grounding, or the electric field perpendicular to the ground cannot be measured, as well as the technical challenges that affect the accuracy of earth electric field measurement due to problems such as polarization, drift, and aging of measuring electrodes. like Figure 1 As shown, let P be a point in space, E be the changing electric field to be measured at point P, A be a plane passing through point P and perpendicular to the electric field E, and B be the vortex-induced magnetic field generated by the changing electric field E on plane A.

[0017] Specifically: According to Maxwell's electromagnetic theory, the rate of change of the electric field is called "displacement current", and the current formed by the directional movement of charges is called "conduction current". The induced magnetic field caused by displacement current is equivalent to the induced magnetic field caused by conduction current.

[0018] The line integral of magnetic flux density B along any closed path is equal to the algebraic sum of the currents (displacement current and conduction current) enclosed by the closed path multiplied by the permeability (i.e., Ampere's circuital law). Therefore, theoretically, any change in the electric field at any point in space, in any direction, will generate a vortex magnetic field on a plane passing through that point and perpendicular to the direction of the electric field, such as... Figure 1 As shown, the magnitude and direction of the vortex magnetic field are related to the rate of change of the electric field and the direction of the electric field, i.e., satisfying: ,in, Indicates proportional to; Based on the above principles, such as Figure 2 The ring-shaped induction coil shown is placed horizontally. Figure 1 As shown in plane A, the receiving vortex magnetic field is B. Let the area of ​​a single turn of the ring induction coil be S, the number of turns be N, and the core permeability be μ. r If the output induced voltage is V, then ,in, Indicates proportional to; That is, as long as the output voltage of the loop induction coil is measured, the electric field perpendicular to the loop coil can be calculated.

[0019] Further: According to the above implementation method, such as Figure 3 As shown, it consists of a ring induction coil, resonant capacitor C1, negative feedback network RF, resistor R1, capacitor C2, preamplifier, low-pass filter, etc. The ring induction coil is used to pick up the vortex magnetic field induced by the change of the electric field to be measured. The resonant capacitor C1 and the ring induction coil together form a resonant network.

[0020] The preamplifier circuit is used to amplify the measurement signal with low noise, and the electric field feedback network is used to widen the bandwidth of the measurement device.

[0021] The electric field negative feedback network consists of a negative feedback resistor RF, a low-pass filter resistor R1, and a capacitor C2. The resistor R1 and capacitor C2 are connected in series and then in parallel with the negative feedback resistor RF. This not only constitutes a voltage negative feedback circuit, but also gives the circuit new characteristics by introducing capacitor C2. Adding resistor R1 and capacitor C2 allows it to form a flexible active low-pass filter with the negative feedback resistor RF. This not only enables frequency compensation and broadens the measurement frequency bandwidth, but also suppresses high-frequency noise, ensuring stable operation of the amplifier without oscillation. The resonant capacitor C1 is connected in parallel with the ring induction coil to form an LC resonant network. By adjusting the LC parameters, the resonant point of the resonant network is placed within the frequency band of the electric field to be measured. After the output signal of the resonant network is amplified by the low-noise preamplifier circuit, part of the signal is fed back to the resonant network through the negative feedback network to flatten the frequency phase curve, and the other part of the signal is driven to output after passing through the low-pass filter circuit. The output signal reflects the magnitude of the electric field to be measured.

[0022] The amplitude-frequency response curves of the resonant network and the amplitude-frequency response curves of the resonant network after adding negative electric field feedback are shown below. Figure 4 As shown.

[0023] The core of this invention lies in: indirectly measuring the electric field to be measured by measuring the vortex magnetic field, realizing electric field measurement at any location and in any direction in space without grounding, overcoming the influence of dielectric distribution, grounding environment, grounding electrode, etc. on electric field measurement, and expanding the application field of electric field measurement device.

[0024] Example 2 In one specific embodiment, in order to achieve electric field measurement at any location and in any direction in space without grounding; like Figure 5As shown, a parallel-plate capacitor can also be used to measure an ungrounded electric field, that is, to measure the potential difference between a pair of parallel plates in space and thus calculate the electric field. It should be noted that when measuring the electric field using a parallel plate capacitor, the signal source impedance is high, making it highly susceptible to external interference.

[0025] The foregoing has provided a detailed description of one embodiment of the present invention, but this description is merely a preferred embodiment and should not be construed as limiting the scope of the invention. All equivalent variations and modifications made within the scope of the claims of this invention should still fall within the patent coverage of this invention.

Claims

1. A method for measuring the electric field of an ungrounded earth, characterized in that, Includes the following steps: The vortex magnetic field induced by the changing electric field at the point to be measured is measured by a loop induction coil. The vortex magnetic field is converted into an induced voltage signal; The induced voltage signal is processed. The value of the electric field to be measured is calculated based on the induced voltage signal.

2. The method for measuring the electric field of an ungrounded earth according to claim 1, characterized in that, The ring-shaped induction coil is placed at the point to be measured, with its plane perpendicular to the direction of the electric field to be measured.

3. The method for measuring the electric field of an ungrounded earth according to claim 1, characterized in that, The signal processing includes at least one of resonant amplification, preamplification, filtering, and negative feedback control.

4. The method for measuring the electric field of an ungrounded earth according to claim 1, characterized in that, The process of calculating the value of the electric field to be measured based on the induced voltage signal is as follows: V is the induced voltage, B is the vortex magnetic field, t is time, S is the area of ​​a single turn, N is the number of turns of the coil, and μ r The core permeability, Let B be the derivative of the vortex magnetic field with respect to time t, representing the rate of change of the vortex magnetic field. It means proportional to.

5. An apparatus for implementing the method of claim 1, characterized in that, include: Ring-shaped induction coil; A resonant capacitor, together with the coil, forms a resonant network; The preamplifier circuit is used to amplify the sensed signal; Filtering circuits are used to filter out noise; Electric field negative feedback network is used to extend the system bandwidth.

6. The apparatus according to claim 5, characterized in that, The ring-shaped induction coil has a magnetic core, and the magnetic core material is a high permeability material.

7. The apparatus according to claim 5, characterized in that, The electric field negative feedback network includes resistor RF, resistor R1, and capacitor C2.

8. A geodetic electric field measurement system, comprising the apparatus as described in any one of claims 5-7.

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