Signal high-frequency interference resisting device and method for electrical resistance tomography

Abstract

The invention discloses a signal high-frequency interference resisting device and method for electrical resistance tomography. A high-frequency filtering unit in the device comprises a magnetic ring, a coaxial shielding line, a first resistor and a second resistor; the coaxial shielding lines are connected between the corresponding detection electrodes and the signal sampling ends, and the first resistors are connected between the first ends of the signal lines in the corresponding coaxial shielding lines and the first ends of the signal lines in the next coaxial shielding lines. The second resistor is connected between the second end of the signal line in the corresponding coaxial shielding line and the second end of the signal line in the next coaxial shielding line; the first end of the signal line in the coaxial shielding line is also connected with the first end of the shielding layer in the next coaxial shielding line; the magnetic rings sleeve the outer layers of all the coaxial shielding wires and are tightly attached to the outer layers of the coaxial shielding wires, filtering on a transmission line is achieved, the twisted-pair coaxial shielding wire magnetic rings are combined to serve as transmission wire harnesses, a hardware coupling filter circuit between the wire harnesses is constructed, the suppression effect of common-mode interference is improved, sampling signals are more real, and imaging is clearer.

Description

Technical Field

[0001] This invention relates to the field of electrical resistance tomography signal acquisition and processing technology, and in particular to a device and method for resisting high-frequency interference in electrical resistance tomography signals. Background Technology

[0002] Electrical resistance tomography (ERT) technology, as a non-invasive process monitoring method, has been gradually applied to the real-time monitoring of solid particle concentration in the mud pipes of dredging vessels.

[0003] However, the electromagnetic environment at dredging sites is complex, posing significant challenges to the practical application of ERT technology. The continuous operation of high-voltage motors, frequency converters, high-power pumps, and other strong electromagnetic equipment generates high-frequency electromagnetic interference ranging from 10kHz to 1MHz. This interference intrudes into the signal acquisition link of the ERT system through spatial or conductive coupling, often leading to severe distortion of the sampled signal. Ultimately, this results in a significant decrease in the accuracy of the concentration reconstruction image, making it difficult to meet the engineering requirements for real-time monitoring of the dredging process. Summary of the Invention

[0004] This invention provides a signal anti-high frequency interference device and method for resistive tomography to improve the suppression effect of common-mode interference, making the sampled signal more realistic and the imaging clearer.

[0005] According to one aspect of the present invention, a signal anti-high frequency interference device for resistive tomography is provided. The signal anti-high frequency interference device for resistive tomography includes a high frequency filtering unit, a signal acquisition board, a signal excitation board, and an even number of detection electrodes sequentially distributed in the circumferential direction of the pipe under test.

[0006] Each of the detection electrodes is connected to a corresponding signal sampling terminal on the signal acquisition board via the high-frequency filtering unit. The high-frequency filtering unit includes a magnetic ring, a coaxial shielding wire, a first resistor, and a second resistor, each corresponding to one of the detection electrodes. The coaxial shielding wire is connected between the corresponding detection electrode and the signal sampling terminal. The first resistor is connected between the first end of the signal line in the corresponding coaxial shielding wire and the first end of the signal line in the next coaxial shielding wire. The second resistor is connected between the second end of the signal line in the corresponding coaxial shielding wire and the second end of the signal line in the next coaxial shielding wire. The first end of the signal line in the coaxial shielding wire is also connected to the first end of the shielding layer in the next coaxial shielding wire. The magnetic ring is sleeved on the outer layer of all the coaxial shielding wires and is in close contact with the outer layer of the coaxial shielding wires.

[0007] The signal excitation board is configured to connect to at least one pair of the detection electrodes and apply excitation to the detection electrodes being tested;

[0008] The signal acquisition board is configured to acquire the sampling signal of the detection electrode via the signal sampling terminal, and determine the true impedance value between the paired detection electrodes based on the sampling signal.

[0009] Optionally, the signal anti-high frequency interference device for resistive tomography further includes a current sensor, which is connected to the pump motor corresponding to the pipe under test and the signal excitation board respectively, and the current sensor is configured to sample the current of the pump motor.

[0010] The signal excitation board is also configured to apply excitation to the detection electrode under test when the current of the pump motor is detected to be zero crossing.

[0011] Optionally, the signal anti-high frequency interference device for resistive tomography also includes redundant electrodes;

[0012] The signal acquisition board is also connected to the redundant electrode. The signal acquisition board is configured to acquire the ambient noise spectrum using the redundant electrode and dynamically adjust the number of wavelet threshold denoising decomposition layers applied to the sampled signal of the detection electrode based on the ambient noise spectrum.

[0013] Optionally, the dynamic adjustment formula for the number of decomposition layers is as follows: ,in, The number of decomposition layers, Sampling rate, For environmental noise frequency, Indicates less than or equal to The largest integer.

[0014] Optionally, the signal acquisition board is further configured to, after adjusting the number of decomposition layers, calculate impedance information under different frequency harmonic excitations based on the excitation parameters and the sampling signal; and then, based on the impedance information, the sampling signal, the excitation signal, and the number of decomposition layers, determine the weighted impedance value between the pairs of detection electrodes at different frequencies and approximate the true impedance value between the pairs of detection electrodes through rapid iteration.

[0015] Optionally, the resistance values ​​of the first resistor and the second resistor in the high-frequency filtering unit are impedance matching results determined by signal matching tests based on the parasitic inductance parameters of the shielding wire and the parasitic resistance parameters of the signal line corresponding to the coaxial shielding wire.

[0016] Optionally, the sum of the capacitance values ​​of the two transfer function capacitors of the high-frequency filtering unit is greater than 10pF and less than 100pF, and the filtering cutoff frequency of the high-frequency filtering unit is greater than twice the excitation frequency and less than ten times the excitation frequency.

[0017] According to another aspect of the present invention, a method for resistive electrical tomography (EDT) signal anti-high frequency interference is provided, the method comprising:

[0018] The signal excitation board applies excitation to the pairs of detection electrodes in sequence, wherein the frequency of the i-th excitation is 50×ikHz, N is the number of detection electrodes, and i is an integer between 1 and N;

[0019] Each time an excitation is applied, the signal sampling board samples the electrical signals on each of the detection electrodes via a high-frequency filtering unit;

[0020] The signal sampling board determines the true resistance value between the paired detection electrodes based on the sampled signal.

[0021] Optionally, before the signal excitation board sequentially applies excitation to the paired detection electrodes, it further includes:

[0022] The current sensor samples the current of the pump motor;

[0023] When the current of the pump motor crosses zero, the current sensor generates a synchronous trigger signal and sends it to the signal excitation board to instruct the signal excitation board to apply excitation.

[0024] Optionally, the signal sampling board determines the true resistance value between the paired detection electrodes based on the sampled signal, including:

[0025] Using redundant electrodes, the ambient noise spectrum is obtained;

[0026] Based on the ambient noise spectrum, the number of wavelet threshold denoising decomposition layers applied to the sampled signal of the detection electrode is dynamically adjusted.

[0027] Based on the excitation parameters and the sampled signal, the impedance information under different frequency harmonic excitations is calculated;

[0028] Based on the impedance information, the sampling signal, the excitation parameters, and the number of decomposition layers, the weighted impedance value between the pairs of detection electrodes at different harmonics is determined, and the true impedance value between the pairs of detection electrodes is approximated by fast iteration.

[0029] The present invention discloses a signal anti-high-frequency interference device and method for resistive tomography. The device includes a high-frequency filtering unit, a signal acquisition board, a signal excitation board, and an even number of detection electrodes sequentially distributed around the circumference of the pipe under test. The high-frequency filtering unit includes a magnetic ring, coaxial shielded wires corresponding to each detection electrode, a first resistor, and a second resistor. The coaxial shielded wires are connected between the corresponding detection electrodes and the signal sampling ends. The first resistor is connected between the first end of the signal line in the corresponding coaxial shielded wire and the first end of the signal line in the next coaxial shielded wire. The second resistor is connected between the second end of the signal line in the corresponding coaxial shielded wire and the second end of the signal line in the next coaxial shielded wire. The first end of the signal line in the coaxial shielded wire is also connected to the first end of the shielding layer in the next coaxial shielded wire. The magnetic ring is sleeved on the outer layer of all coaxial shielded wires and is in close contact with the outer layer of the coaxial shielded wires, realizing filtering on the transmission line. The combination of twisted coaxial shielded wires and magnetic rings is used as a transmission line bundle, constructing a hardware coupling filtering circuit between the line bundles, which improves the suppression effect of common-mode interference, making the sampled signal more realistic and the imaging clearer.

[0030] It should be understood that the description in this section is not intended to identify key or essential features of the embodiments of the present invention, nor is it intended to limit the scope of the invention. Other features of the invention will become readily apparent from the following description. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 This is a schematic diagram of the composition of a signal anti-high frequency interference device for resistive tomography provided in an embodiment of the present invention;

[0033] Figure 2 This is a schematic diagram illustrating the composition of a high-frequency filtering unit provided in an embodiment of the present invention;

[0034] Figure 3 A schematic diagram of another signal anti-high frequency interference device for resistive tomography provided in an embodiment of the present invention;

[0035] Figure 4 A schematic diagram illustrating the composition of another signal anti-high frequency interference device for resistive tomography provided in this embodiment of the invention;

[0036] Figure 5 A flowchart illustrating a method for resistive tomography to resist high-frequency interference provided in an embodiment of the present invention;

[0037] Figure 6 This is a flowchart illustrating another method for resistive tomography to resist high-frequency interference, provided in an embodiment of the present invention. Detailed Implementation

[0038] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. 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 should fall within the scope of protection of the present invention.

[0039] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0040] As in the background technology, high-frequency electromagnetic interference during dredging can intrude into the signal acquisition link of the ERT system through spatial coupling or conductive coupling, often leading to severe distortion of the sampling signal and ultimately causing a significant decrease in the accuracy of the concentration reconstruction image, making it difficult to meet the engineering requirements for real-time monitoring of the dredging process.

[0041] To address the aforementioned issues, existing technologies primarily employ three suppression schemes: First, conventional signal acquisition lines utilize a dual-layer structure design of "signal transmission core layer + external shielding layer," where the external shielding layer typically isolates external noise from the inner signal line through a single-point grounding method. However, research by the inventors revealed that, on the one hand, this single-point grounding method is insufficient to completely block the path of high-frequency interference coupled to the inner signal line via distributed capacitance, resulting in limited common-mode interference suppression. On the other hand, parasitic capacitance between the shielding layer and the core layer forms a coupling channel at high frequencies, causing the shielding effectiveness to decrease sharply with increasing frequency. In practical applications, additional hardware costs are still required to improve the shielding effect, posing a dual challenge to both economy and reliability. Second, post-processing methods for signal distortion often employ techniques such as FFT frequency domain filtering. While this can suppress interference components through frequency domain analysis, increasing the filter order significantly increases the computational complexity of the algorithm. Under the real-time requirements of dredging sites (typically requiring millisecond-level response times), the computational delay generated during high-frequency interference suppression severely affects the synchronization of data acquisition and processing, making it difficult to achieve real-time inversion and monitoring of concentration parameters. Third, although the differential amplification scheme at the hardware circuit level can suppress common-mode interference to a certain extent through dual-ended input, its effective suppression frequency band is limited by the bandwidth characteristics of the amplification chip. For high-frequency interference components above 100kHz, the gain attenuation and phase shift of the amplification circuit will cause a significant decrease in interference suppression capability, which cannot meet the signal acquisition requirements of the high-frequency electromagnetic interference environment at the dredging site.

[0042] To address the aforementioned issues, this application proposes a signal anti-high-frequency interference device for resistive tomography. Figure 1 This is a schematic diagram of the composition of a signal anti-high frequency interference device for resistive tomography provided in an embodiment of the present invention, referring to... Figure 1The high-frequency interference suppression device 100 for resistive tomography includes a high-frequency filtering unit 101, a signal acquisition board 102, a signal excitation board 103, and an even number of detection electrodes 104 sequentially distributed along the circumference of the pipe under test. Each detection electrode 104 is connected to a corresponding signal sampling terminal on the signal acquisition board 102 via the high-frequency filtering unit 101. The high-frequency filtering unit 101 includes a magnetic ring 105, a coaxial shielded wire corresponding to each detection electrode 104, a first resistor R1, and a second resistor R2. The coaxial shielded wire is connected between the corresponding detection electrode 104 and the signal sampling terminal. The first resistor R1 is connected between the first end of the signal line 106 in the corresponding coaxial shielded wire and the first end of the signal line 106 in the next coaxial shielded wire. The second resistor R2 is connected between the second end of the signal line 106 in the corresponding coaxial shielded wire and the second end of the signal line 106 in the next coaxial shielded wire. The first end of the signal line 106 in the coaxial shielded cable is also connected to the first end of the shielding layer 107 in the next coaxial shielded cable; the magnetic ring 105 is sleeved on the outer layer of all coaxial shielded cables and is in close contact with the outer layer of the coaxial shielded cables. The signal excitation board 103 is configured to connect to at least one pair of detection electrodes 104 and apply excitation to the detection electrodes 104 under test. The signal acquisition board 102 is configured to acquire the sampling signal of the detection electrodes 104 via the signal sampling terminal and determine the true impedance value between the paired detection electrodes 104 based on the sampling signal.

[0043] Specifically, the signal excitation board 103 refers to a core hardware module that integrates signal processing functions such as excitation signal generation, digital-to-analog conversion and filtering, as well as signal output functions such as electrode driving and signal isolation. Its function is to convert the received excitation command into a stable and controllable electrical signal and apply it precisely to the electrode array of the area under test, providing a standard excitation source for subsequent response signal acquisition and impedance distribution inference. For example, the signal excitation board 103 can integrate an FPGA software processing unit, a digital-to-analog converter unit, a low-pass filter unit, an excitation signal output unit, and at least one pair of excitation signal output terminals. The FPGA software integrated in the FPGA software processing unit can generate corresponding digital excitation signals according to the excitation instructions issued by the front-end controller. The digital-to-analog converter unit can further convert the digital excitation signals into analog signals to obtain the required frequency, waveform, and amplitude of the excitation signals. Furthermore, the low-pass filter unit can perform low-pass filtering on the excitation signals to avoid the electrode polarization effect caused by DC signals, which would interfere with subsequent impedance measurements. The excitation signal output unit can realize the power amplification of the excitation signals and motor drive, accurately outputting the excitation signals to the corresponding detection electrodes 104 through the corresponding excitation signal output terminals. The positive terminal of the paired excitation signal output terminals is connected to one of the corresponding detection electrodes 104 through the high-frequency filter unit 101, and the negative terminal can be directly connected to the other detection electrode 104, so as to apply the excitation signal to the paired detection electrodes 104.

[0044] The detection electrode 104 is a sensing element that directly contacts the pipe under test, applies an excitation signal to the pipe, and collects the electrical response signal on the pipe. Its function is to convert the potential distribution generated by the excitation signal in the pipe into a measurable voltage signal, providing raw measured data for subsequent calculation of apparent impedance and reconstruction of impedance distribution. The detection electrodes 104 are distributed equidistantly along the circumference of the pipe under test. For example, when the pipe under test has a circular cross-section, the equidistant distribution means that the central angles between the two rays from any two adjacent detection electrodes 104 to the center of the pipe cross-section are equal.

[0045] The signal acquisition board 102 is a sampling hardware component that receives the output of the detection electrode 104 and preprocesses, converts, and transmits the original electrical response signal on the detection electrode 104. Its function is to convert the weak and easily interfered analog sampling signal acquired by the detection electrode 104 into a digital signal that can be processed by the subsequent signal processing equipment, and improve the signal quality through noise reduction, amplification and other processing, so as to provide a signal basis for subsequent apparent impedance calculation and impedance distribution reconstruction. For example, the signal acquisition board 102 may include signal sampling terminals corresponding one-to-one with the detection electrodes 104, as well as a signal conditioning unit, a second-order Butterworth filter unit, an analog-to-digital converter unit, and an FPGA software processing unit. The signal sampling terminals are connected to their corresponding detection electrodes 104 via a high-frequency filter unit 101, enabling sampling of the voltage signal on the detection electrodes 104. The signal conditioning unit may include a signal amplification function, precisely amplifying the sampled signal through an instrumentation amplifier or a programmable gain amplifier. The amplification factor can be dynamically adjusted according to the signal strength, ensuring that the amplitude of the processed sampled signal falls within the high sensitivity range of the subsequent analog-to-digital converter unit, ensuring that minute signal differences can be accurately identified by the subsequent analog-to-digital converter unit. The second-order Butterworth filter unit... The unit is a filter circuit capable of accurately filtering out interference at specific frequencies and retaining effective signals. It is designed based on Butterworth filtering theory. Its core feature is that the effective signal frequency range has the flattest amplitude-frequency characteristics, while achieving stable attenuation in the interference signal frequency range. It can effectively suppress power frequency interference and high-frequency electromagnetic noise in the sampled signal and ensure the quality of the sampled signal. For example, the second-order Butterworth filter unit can use a dynamically adjusted adaptive digital filtering algorithm to adaptively filter the sampled signal; the analog-to-digital conversion unit can convert the analog sampled signal after signal conditioning and filtering into a digital sampled signal; and the FPGA software processing unit can determine the true impedance value between the paired detection electrodes 104 based on the digital sampled signal using integrated FPGA software.

[0046] The high-frequency filtering unit 101 refers to the high-frequency filtering component disposed between the signal acquisition board 102 and the detection electrode 104. It includes a magnetic ring 105, and coaxial shielded wires corresponding to the detection electrodes 104, a first resistor R1, and a second resistor R2. The coaxial shielded wire includes a built-in signal line 106 and a shielding layer 107 wrapped around the signal line 106. The first end of the signal line 106 is connected to the corresponding signal sampling end on the signal acquisition board 102 and the first end of the shielding layer 107 in the next coaxial shielded wire, respectively. The second end of the signal line 106 is connected to the corresponding detection electrode 104. The first resistor R1 is connected between the first end of the signal line 106 in the corresponding coaxial shield and the first end of the signal line 106 in the next coaxial shield. The second resistor R2 is connected between the second end of the signal line 106 in the corresponding coaxial shield and the second end of the signal line 106 in the next coaxial shield. For example, the resistance values ​​of the first resistor R1 and the second resistor R2 are impedance matching results determined by signal matching tests based on the parasitic inductance parameters of the shielding layer of the corresponding coaxial shield and the parasitic resistance parameters of the signal line 106.

[0047] For example, Figure 2 This is a schematic diagram of the composition of a high-frequency filtering unit provided in an embodiment of the present invention, combined with... Figure 1 and Figure 2 The high-frequency filtering unit 101 includes a first resistor R1, a second resistor R2, two transfer function capacitors C1 and C2, the parasitic inductance L1 of the shielding layer 107, and the parasitic resistance R3 of the signal line. The first resistor R1, the second resistor R2, the two transfer function capacitors C1 and C2, the parasitic inductance L1 of the shielding layer 107, and the parasitic resistance R3 of the signal line 106 are connected in a specific configuration. The parasitic inductance L1 of the shielding layer 107 and the parasitic resistance R3 of the signal line 106 are measured using an inductance-capacitance-resistance tester. The matching impedance, i.e., the first resistor R1 and the second resistor R2, is selected through a signal matching test. The resistance values ​​of the first resistor R1 and the second resistor R2 are between 50 and 100 Ω. The transfer function... Determine the cutoff frequency of the high-frequency filter unit 101 By cutoff frequency Calculate the values ​​of the transfer function capacitances C1 and C2. The transfer function is determined by the following formula, where s is a complex frequency domain variable introduced in the Laplace transform, s = jω, jω is the imaginary part, ω is the angular frequency, j is the imaginary unit, and s 0 s represents s to the power of 0. 1 s represents the first power of s. 2 s represents the power of 2, s 3 This represents s raised to the power of 3; , , and The values ​​are determined by the first resistor R1, the second resistor R2, the parasitic resistance of the signal line R3, and the parasitic inductance L1 of the shielding layer 107, respectively. The excitation frequency is set to a single multiple. Then the filter cutoff frequency Satisfy the following relationship The equations representing the two transfer functions of capacitors C1 and C2 and the filter cutoff frequency. The relationships can be combined into a formula. In other words, the sum of the capacitance values ​​of the two transfer function capacitors C1 and C2 of the high-frequency filter unit 101 is greater than 10pF and less than 100pF, and makes the filter cutoff frequency of the high-frequency filter unit 101... Excitation frequency greater than one Excitation frequency that is twice as high as but less than one times the frequency of the excitation frequency It is 10 times that of the original. In addition, the magnetic ring 105 is fitted on the outer layer of the coaxial shielded wire harness and is in close contact with the outer layer of the harness. The magnetic ring impedance of the magnetic ring 105 should be ≥1kΩ@1MHz to suppress common-mode interference.

[0048] The high-frequency interference suppression device for resistive tomography provided in this embodiment includes a high-frequency filtering unit, a signal acquisition board, a signal excitation board, and an even number of detection electrodes sequentially distributed around the circumference of the pipe under test. The high-frequency filtering unit includes a magnetic ring, coaxial shielded wires corresponding to each detection electrode, a first resistor, and a second resistor. The coaxial shielded wires are connected between the corresponding detection electrodes and the signal sampling ends. The first resistor is connected between the first end of the signal line in the corresponding coaxial shielded wire and the first end of the signal line in the next coaxial shielded wire. The second resistor is connected between the second end of the signal line in the corresponding coaxial shielded wire and the second end of the signal line in the next coaxial shielded wire. The first end of the signal line in the coaxial shielded wire is also connected to the first end of the shielding layer in the next coaxial shielded wire. The magnetic ring is fitted around the outer layer of all coaxial shielded wires, closely adhering to the outer layer, thus achieving filtering on the transmission line. Using a combination of twisted-pair coaxial shielded wires and magnetic rings as a transmission bundle constructs a hardware coupling filtering circuit between the bundles, improving the suppression effect of common-mode interference and making the sampled signal more realistic and the imaging clearer.

[0049] Optionally, Figure 3 This is a schematic diagram of another signal anti-high frequency interference device for resistive tomography provided in an embodiment of the present invention. Based on the foregoing embodiments, refer to... Figure 3 The high-frequency interference suppression device 100 for resistive tomography also includes a current sensor 301, which is connected to the pump motor corresponding to the pipe under test and the signal excitation board 103. The current sensor 301 is configured to sample the current of the pump motor. The signal excitation board 103 is also configured to apply excitation to the detection electrode 104 under test when the zero-crossing point of the pump motor current is detected.

[0050] Specifically, the pump motor refers to the power motor connected to the tested pipeline, which drives the pump body to operate and thus provides transportation power for the fluid in the tested pipeline. For example, the pump motor may include a mud pump motor. The inventors have discovered that the connection of the pump motor to the tested pipeline and its operating state can interfere with the excitation signal during the resistivity tomography (RTG) process of the tested pipeline, thereby affecting the accuracy of the RTG. Based on this, the RTG signal anti-high-frequency interference device 100 proposed in this application also includes a current sensor 301. The current sensor 301 is used to sample the current of the pump motor connected to the tested pipeline. The current sensor 301 is also connected to the signal excitation board 103 (either directly or via a control device). The current sensor 301 can output a synchronous trigger signal to trigger the signal excitation board 103 to apply excitation to the detection electrode 104 when the pump motor's phase crosses zero. Furthermore, the excitation applied by the signal excitation board 103 to the detection electrode 104 uses a multi-frequency excitation method to avoid interference between two excitations.

[0051] For example, one port of the current sensor 301 is connected to the pump motor via signal line 106 to monitor the current signal of the pump motor in real time; the other port of the current sensor 301 is connected to the signal excitation board 103 via signal line 106 and transmits the current signal of the mud pump motor to the signal excitation board 103. When the signal excitation board 103 detects that the current signal of the pump motor is 0, it outputs an excitation signal to the corresponding pair of detection electrodes 104.

[0052] The application of the excitation signal and the voltage sampling of the detection electrode 104 are illustrated in the following embodiment: Each pair of detection electrodes 104 is excited once, and for an array of N detection electrodes 104, a total of N excitations are applied. i is an integer between 1 and N, representing the i-th excitation, and the frequency of the i-th excitation is 50 × i kHz. Each time excitation is applied, the voltage of all detection electrodes 104 is sampled. It should be noted that, on the one hand, the paired detection electrodes 104 are directly opposite each other, meaning the line connecting them passes through the center of the cross-section of the pipe being measured. For example, when i is less than N / 2, the sequence number of the paired detection electrodes 104 excited in the i-th instance is (i, N / 2 + i); when i is greater than N / 2, the sequence number of the paired detection electrodes 104 excited in the i-th instance is (iN / 2, i). On the other hand, the detection electrodes 104 are polarity-distinguished; that is, the two electrodes are counted as two different pairs of electrodes before and after the polarity is reversed. The relationship between the target voltage and the sampled voltage obtained in this way is as follows: As shown, the target voltage can be calculated using this formula, where, Indicates the target voltage. This represents the data set formed by the i-th sampling voltage, where n represents the total number of samplings, which is equal to the number N of the detection electrodes 104.

[0053] The resistivity tomography signal anti-high frequency interference device 100 provided in this embodiment also includes a current sensor, which is connected to the pump motor corresponding to the pipe under test and the signal excitation board 103 respectively. The current sensor is configured to sample the current of the pump motor. The signal excitation board 103 is also configured to apply excitation to the detection electrode 104 under test when the zero-crossing point of the pump motor current is detected, thereby avoiding interference of the pump motor operation on the excitation signal and further improving the realism of the imaging.

[0054] Optionally, Figure 4 This is a schematic diagram of another signal anti-high frequency interference device for resistive tomography provided in an embodiment of the present invention. Based on the foregoing embodiments, refer to... Figure 4 The high-frequency interference suppression device 100 for resistive tomography also includes a redundant electrode 401. The signal acquisition board 102 is also connected to the redundant electrode 401. The signal acquisition board 102 is configured to acquire the ambient noise spectrum using the redundant electrode 401, and dynamically adjust the number of wavelet threshold denoising decomposition layers applied to the sampled signal of the detection electrode 104 based on the ambient noise spectrum.

[0055] Specifically, wavelet threshold denoising is a digital denoising algorithm set in the signal acquisition board 102 that decomposes the signal through wavelet transform and applies a threshold to the wavelet coefficients corresponding to noise, thereby achieving effective signal preservation and noise suppression. For example, the wavelet threshold denoising algorithm can be designed in the FPGA software processing unit after the analog-to-digital conversion unit of the signal acquisition board 102. The number of decomposition layers of wavelet threshold denoising refers to the number of times the original signal is decomposed into low-frequency approximate components and high-frequency detail components according to frequency when performing wavelet transform. Its core function is to accurately separate the effective components and noise components of different frequencies in the sampled signal through multi-scale decomposition, providing a basis for layered processing for subsequent threshold denoising.

[0056] Redundant electrode 401 refers to an electrode distinct from detection electrode 104 and disposed in the detection environment for detecting interference signals in the environment. For example, redundant electrode 401 can be disposed around the circumference of the pipe under test or in the environment where the pipe is located. Signal acquisition board 102 is connected to redundant electrode 401 and can sample the environmental electrical signals generated by environmental factors on redundant electrode 401. Based on the environmental noise spectrum, it dynamically adjusts the number of decomposition layers for wavelet threshold denoising of the sampled signal from detection electrode 104. For example, the FPGA software processing unit in signal acquisition board 102 can integrate a dynamically adjusted adaptive digital filtering algorithm. This algorithm can utilize the sampled signal from redundant electrode 401 to monitor the environmental noise spectrum in real time and dynamically adjust the number of decomposition layers for wavelet threshold denoising based on the environmental noise spectrum. The dynamic adjustment formula for the number of decomposition layers in wavelet threshold denoising is... ,in, The number of decomposition layers, Sampling rate, For environmental noise frequency, Indicates less than or equal to The largest integer.

[0057] Furthermore, the signal acquisition board 102 is also configured to utilize its integrated dynamically adjusted adaptive digital filtering algorithm to further calculate the impedance information Z1, Z2…Z under different frequency harmonic excitations based on the excitation parameters and sampled signals after adjusting the number of decomposition layers. N The numbers 1, 2, ... N indicated by the subscripts represent the order of the harmonics; furthermore, based on impedance information, the sampled signal, the excitation signal, and the number of decomposition layers, combined with the formula... The weighted impedance values ​​between paired detection electrodes 104 at different frequencies are determined, and the true impedance values ​​between paired detection electrodes 104 are approximated through rapid iteration. The impedance is the true impedance between the paired detection electrodes, where N represents the order of the harmonic and C represents the number of decomposition layers. This represents the voltage sampled at the i-th time. Indicates the target voltage. This represents the impedance information under i-fold frequency excitation.

[0058] The high-frequency interference suppression device for resistive tomography provided in this embodiment also includes redundant electrodes. The signal acquisition board is also connected to the redundant electrodes. The signal acquisition board is configured to acquire the ambient noise spectrum using the redundant electrodes. Based on the ambient noise spectrum, the number of wavelet threshold denoising decomposition layers applied to the sampling signal of the detection electrode is dynamically adjusted, realizing dynamic adjustment of the algorithm, reducing the impact of ambient noise on resistive tomography, and further improving the accuracy of imaging.

[0059] The present invention also provides a method for resisting high-frequency interference in resistive tomography. Figure 5 This is a flowchart illustrating a method for resistive tomography signal anti-high frequency interference provided in an embodiment of the present invention. Based on the foregoing embodiments, refer to... Figure 5 Methods for resistive tomography to resist high-frequency interference include:

[0060] S501, the signal excitation board applies excitation sequentially to the paired detection electrodes.

[0061] Wherein, the frequency of the i-th excitation is 50×i kHz, N is the number of detection electrodes, and i is an integer between 1 and N.

[0062] S502. Each time an excitation is applied, the signal sampling board samples the electrical signals on each detection electrode via a high-frequency filtering unit.

[0063] S503, the signal sampling board determines the true resistance between the paired detection electrodes based on the sampled signal.

[0064] The high-frequency interference suppression method for resistive tomography provided in this embodiment involves a signal excitation board that sequentially excites paired detection electrodes. During each excitation application, a signal sampling board samples the electrical signals on each detection electrode via a high-frequency filtering unit. Based on the sampled signals, the signal sampling board determines the true resistance value between the paired detection electrodes, achieving reliable sampling in resistive tomography. The high-frequency filtering unit uses a combination of twisted-pair coaxial shielded wire and magnetic rings as the transmission line bundle, constructing a hardware coupling filtering circuit between the bundles, which improves the suppression of common-mode interference, resulting in more realistic sampled signals and clearer imaging.

[0065] Figure 6 This is a flowchart illustrating another method for resistive tomography signal anti-high frequency interference provided in an embodiment of the present invention. Based on the foregoing embodiments, refer to... Figure 6 Methods for resistive tomography to resist high-frequency interference include:

[0066] S601, the current sensor samples the current of the pump motor.

[0067] S602. When the pump motor current crosses zero, the current sensor generates a synchronous trigger signal and sends it to the value signal excitation board to instruct the signal excitation board to apply excitation.

[0068] S603, the signal excitation board applies excitation sequentially to pairs of detection electrodes.

[0069] S604. Each time an excitation is applied, the signal sampling board samples the electrical signals on each detection electrode via a high-frequency filtering unit.

[0070] S605, the signal sampling board determines the true resistance between the paired detection electrodes based on the sampled signal.

[0071] For example, determining the true tissue may include: acquiring the ambient noise spectrum using redundant electrodes; dynamically adjusting the number of decomposition levels for wavelet threshold denoising applied to the sampled signals of the detection electrodes based on the ambient noise spectrum; calculating impedance information under different harmonic excitation frequencies based on excitation parameters and sampled signals; and determining the weighted impedance values ​​between pairs of detection electrodes at different harmonic excitation frequencies based on the impedance information, sampled signals, excitation parameters, and number of decomposition levels, and approximating the true impedance values ​​between pairs of detection electrodes through rapid iteration.

[0072] In the high-frequency interference suppression method for resistive tomography provided in this embodiment, a current sensor samples the current of the pump motor. When the pump motor current crosses zero, the current sensor generates a synchronous trigger signal and sends it to the excitation board to instruct the excitation board to apply excitation. This method reduces the interference of pump motor operation on the excitation signal and further improves the realism of the imaging.

[0073] It should be understood that the various forms of processes shown above can be used, with steps reordered, added, or deleted. For example, the steps described in this invention can be executed in parallel, sequentially, or in different orders, as long as the desired result of the technical solution of this invention can be achieved, and this is not limited herein.

[0074] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A signal anti-high frequency interference device for resistive tomography, characterized in that, include: The system consists of a high-frequency filtering unit, a signal acquisition board, a signal excitation board, and an even number of detection electrodes arranged sequentially around the circumference of the pipe under test. Each of the detection electrodes is connected to a corresponding signal sampling terminal on the signal acquisition board via the high-frequency filtering unit. The high-frequency filtering unit includes a magnetic ring, a coaxial shielding wire, a first resistor, and a second resistor, each corresponding to one of the detection electrodes. The coaxial shielding wire is connected between the corresponding detection electrode and the signal sampling terminal. The first resistor is connected between the first end of the signal line in the corresponding coaxial shielding wire and the first end of the signal line in the next coaxial shielding wire. The second resistor is connected between the second end of the signal line in the corresponding coaxial shielding wire and the second end of the signal line in the next coaxial shielding wire. The first end of the signal line in the coaxial shielding wire is also connected to the first end of the shielding layer in the next coaxial shielding wire. The magnetic ring is sleeved on the outer layer of all the coaxial shielding wires and is in close contact with the outer layer of the coaxial shielding wires. The signal excitation board is configured to connect to at least one pair of the detection electrodes and apply excitation to the detection electrodes being tested; The signal acquisition board is configured to acquire the sampling signal of the detection electrode via the signal sampling terminal, and determine the true impedance value between the paired detection electrodes based on the sampling signal.

2. The signal anti-high frequency interference device for resistive tomography according to claim 1, characterized in that, It also includes a current sensor, which is connected to the pump motor corresponding to the pipe under test and the signal excitation board respectively. The current sensor is configured to sample the current of the pump motor. The signal excitation board is also configured to apply excitation to the detection electrode under test when the current of the pump motor is detected to be zero-crossing.

3. The signal anti-high frequency interference device for resistive tomography according to claim 1, characterized in that, It also includes redundant electrodes; The signal acquisition board is also connected to the redundant electrode. The signal acquisition board is configured to acquire the ambient noise spectrum using the redundant electrode and dynamically adjust the number of wavelet threshold denoising decomposition layers applied to the sampled signal of the detection electrode based on the ambient noise spectrum.

4. The signal anti-high frequency interference device for resistive tomography according to claim 3, characterized in that, The dynamic adjustment formula for the number of decomposition layers is as follows: Where C is the number of decomposition layers. Sampling rate, For environmental noise frequency, Indicates less than or equal to The largest integer.

5. The signal anti-high frequency interference device for resistive tomography according to claim 3, characterized in that, The signal acquisition board is further configured to, after adjusting the number of decomposition layers, calculate impedance information under different frequency harmonic excitations based on the excitation parameters and the sampling signal; then, based on the impedance information, the sampling signal, the excitation signal, and the number of decomposition layers, determine the weighted impedance value between the pairs of detection electrodes at different frequencies and approximate the true impedance value between the pairs of detection electrodes through rapid iteration.

6. The signal anti-high frequency interference device for resistive tomography according to any one of claims 1-5, characterized in that, The resistance values ​​of the first resistor and the second resistor in the high-frequency filtering unit are impedance matching results determined by signal matching tests based on the parasitic inductance parameters of the shielding wire and the parasitic resistance parameters of the signal line corresponding to the coaxial shielding wire.

7. The signal anti-high frequency interference device for resistive tomography according to any one of claims 1-5, characterized in that, The sum of the capacitance values ​​of the two transfer function capacitors of the high-frequency filtering unit is greater than 10pF and less than 100pF, and the filtering cutoff frequency of the high-frequency filtering unit is greater than twice the excitation frequency and less than 10 times the excitation frequency.

8. A method for resistive tomography to resist high-frequency interference, characterized in that, include: The signal excitation board applies excitation to the pairs of detection electrodes in sequence, wherein the frequency of the i-th excitation is 50×i kHz, N is the number of detection electrodes, and i is an integer between 1 and N; Each time an excitation is applied, the signal sampling board samples the electrical signals on each of the detection electrodes via a high-frequency filtering unit; The signal sampling board determines the true resistance value between the paired detection electrodes based on the sampled signal.

9. The method for resistive high-frequency interference suppression of resistive tomography according to claim 8, characterized in that, Before the signal excitation board sequentially applies excitation to the paired detection electrodes, it further includes: The current sensor samples the current of the pump motor; When the current of the pump motor crosses zero, the current sensor generates a synchronous trigger signal and sends it to the signal excitation board to instruct the signal excitation board to apply excitation.

10. The method for resistive electrical tomography signal anti-high frequency interference according to claim 8, characterized in that, The signal sampling board determines the true resistance value between the paired detection electrodes based on the sampled signal, including: Using redundant electrodes, the ambient noise spectrum is obtained; Based on the ambient noise spectrum, the number of wavelet threshold denoising decomposition layers applied to the sampled signal of the detection electrode is dynamically adjusted. Based on the excitation parameters and the sampled signal, the impedance information under different frequency harmonic excitations is calculated; Based on the impedance information, the sampling signal, the excitation parameters, and the number of decomposition layers, the weighted impedance value between the pairs of detection electrodes at different harmonics is determined, and the true impedance value between the pairs of detection electrodes is approximated by fast iteration.

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