Ultramicro direct current monitoring device and monitoring method thereof

Abstract

The invention provides an ultramicro direct current monitoring device and method, and the device is used for monitoring an ultramicro direct current signal, and comprises a power board, a pulse voltage excitation board, a metal isolation board, an acquisition board, a backboard, and a metal housing. The ultramicro direct current monitoring method adopts the ultramicro direct current monitoring device and comprises a pulse excitation voltage frequency searching control step and an ultramicro direct current calculation step, and high-precision monitoring of ultramicro direct current signals is achieved through the pulse excitation voltage frequency searching control step and the ultramicro direct current calculation step. According to the invention, accurate monitoring of the microampere-level direct current can be realized, and reliable data support is provided for insulation state evaluation and fault diagnosis of a power system.

Description

Technical Field

[0001] This invention relates to the field of electrical intelligent monitoring technology for power systems, specifically to an ultra-micro DC monitoring device and method capable of accurately monitoring microampere-level DC current. Background Technology

[0002] In recent years, with the implementation and development of policies such as Digital China and Smart Grid, the intelligentization of electrical equipment has gradually advanced to the practical application stage. Intelligent monitoring devices have been widely used in various power grid supply and distribution systems, among which ultra-micro DC monitoring has a wide and urgent application demand.

[0003] On the one hand, in the fields of high-voltage direct current (HVDC) transmission and light-duty direct current (DC) transmission, a large number of insulators, surge arresters, bushings, DC transmission and distribution equipment, and cables are used. During these applications, leakage current is widespread. When monitored, the current characteristic is DC, and the leakage magnitude exhibits small current characteristics such as microamperes and milliamperes. For example, after a period of operation, some insulators may develop contamination on their surface, leading to an increase in leakage current. If this is not detected and addressed in a timely manner, it may cause insulation faults, affecting the safe and stable operation of the power grid.

[0004] On the other hand, in the field of new energy, the DC-side insulation problem of photovoltaic power generation has always been a pain point in the industry. The leakage current generated on the DC side needs to be monitored to assess the quality of the insulation. If the insulation has problems, it may lead to a DC-side short circuit, damaging the photovoltaic equipment and affecting the power generation efficiency.

[0005] In addition, when monitoring the insulation resistance of the system using the DC superposition method, DC leakage current will be generated in each branch after DC injection. Therefore, microampere-level current monitoring is also required when locating the insulation problem of the branch.

[0006] However, effective measures for monitoring microampere-level currents have traditionally been lacking. Conventional measurements using Hall effect sensors typically have milliampere-level accuracy, which is insufficient for the precise monitoring of microampere-level currents. Therefore, achieving microampere-level current monitoring is of significant practical importance and is urgently needed. Summary of the Invention

[0007] To address the various shortcomings of existing technologies, this invention provides an ultra-micro DC monitoring device and its monitoring method, which can achieve accurate monitoring of microampere-level DC current and provide reliable data support for insulation status assessment and fault diagnosis of power systems.

[0008] The present invention achieves the above objectives through the following technical solutions: An ultra-micro DC monitoring device, used for monitoring ultra-micro DC signals, includes a power supply board, a pulse voltage excitation board, a metal isolation board, a data acquisition board, a backplate, and a metal casing, wherein: The power board is configured to receive power from an external source, perform voltage conversion, and then guide the converted voltage to the backplane for use by the internal components of the monitoring device. The pulse voltage excitation board is electrically connected to the backplane, obtains power from the backplane and generates a pulse excitation voltage to provide excitation power to the sensors connected to the monitoring device. The acquisition board is electrically connected to the backplane, obtains power from the backplane, and is used to acquire analog signals from the sensors. The metal isolation plate, together with the metal casing, physically divides the inside of the monitoring device into two independent electrical spaces. The power supply board and the acquisition board are placed in the same electrical space, while the pulse voltage excitation board is placed independently in another electrical space to achieve electrical isolation and interference suppression.

[0009] According to the present invention, an ultra-micro DC monitoring device is provided, wherein the sensor is an ultra-micro DC inductive sensor, and the sensor specifically includes: Both magnetic cores are made of 1J85 permalloy. Three windings: Each magnetic core has a first winding and a second winding with the same number of turns, and the two windings are wound in opposite directions. The two first windings and second windings with opposite directions are connected in series to form an excitation winding. The remaining two ends of the excitation winding are connected to the output port of the pulse voltage excitation board. The third winding is wound on two magnetic cores at the same time and is used as a monitoring winding. Its two ends are connected to the input port of the acquisition board.

[0010] According to the present invention, an ultra-micro DC monitoring device is provided, wherein the magnetic core is designed with a square cross-section and a side length of a, and the number of turns of the winding on each magnetic core is set to N turns. Based on the geometric relationship between the magnetic core and the winding, the number of turns of the monitoring winding is calculated as follows:

[0011] A monitoring method for an ultra-micro DC monitoring device, the method employing the aforementioned ultra-micro DC monitoring device, includes the following steps: The pulse excitation voltage frequency search control steps and the ultra-micro DC calculation steps, among which: The pulse excitation voltage frequency search control step is used to apply an initial pulse excitation voltage signal to the excitation winding of the sensor and determine the optimal pulse excitation voltage frequency for powering the excitation winding of the sensor, so as to improve the sensor's sensitivity to ultra-micro DC signals. The ultra-micro DC calculation step is used to calculate the actual input DC signal value based on the signal output from the sensor's monitoring winding; High-precision monitoring of ultra-micro DC signals is achieved by combining the control steps of pulse excitation voltage frequency search with ultra-micro DC calculation steps.

[0012] According to a monitoring method for an ultra-micro DC monitoring device provided by the present invention, the pulse excitation voltage frequency search and control step includes: A 100μA DC signal is applied to the sensor, allowing the DC signal to pass through the sensor; The pulse excitation voltage output is set to an alternating positive and negative pulse voltage wave with a 50% duty cycle; The frequency fx of the positive and negative voltage waves is increased in steps of 0.01Hz according to a preset time interval until the frequency reaches the preset value. During the frequency increase process, the acquisition board is used to collect and monitor the signal of the winding in real time; The acquired signal is decomposed using the current frequency fx as the fundamental frequency and the component with twice the frequency fx is calculated. As the frequency fx continues to increase, the peak signal curve of the frequency component twice fx is plotted. Find the maximum peak value in the signal peak curve, and determine the frequency of the positive and negative pulse voltage waves corresponding to the maximum peak value as fNx; A fixed frequency fNx and a 50% duty cycle are used to output positive and negative pulse voltages to power the excitation winding of the sensor, thereby determining the optimal pulse excitation voltage frequency for powering the sensor's excitation winding.

[0013] According to the present invention, a monitoring method for an ultra-micro DC monitoring device includes an ultra-micro DC calculation step, comprising: After the pulse voltage is fixed with fNx as the base frequency and 50% duty cycle, positive and negative pulse voltages are output. A 100μA DC signal is given to the sensor, and the signal output from the monitoring winding is decomposed by FFT. The decomposition yields frequencies of fNx, f2Nx, f4Nx, f6Nx, f8Nx, and f... 10 Nx, with amplitudes of ANx, A2Nx, A4Nx, A8Nx, and A 10 The signal components of Nx, where 2, 4, 6, 8, and 10 represent 2 times, 4 times, 6 times, 8 times, and 10 times the frequency of fNx, respectively; Calculate the root mean square value A of the even-order harmonics corresponding to a given 100μA DC signal. 100μ ; Calculate the root mean square value A of the even harmonics corresponding to a given 0 μA DC signal. 0μ ; Determine the proportionality coefficient k between the sensor output and the sampled value based on the calculation results; When the actual input DC signal is Idc, the root mean square value of the corresponding even harmonic is calculated based on the proportional coefficient. This leads to the actual DC signal value. .

[0014] According to the monitoring method of the ultra-micro DC monitoring device provided by the present invention, the root mean square value of the even-order harmonics corresponding to 100uA DC is calculated and expressed as: ,in fs This represents the sampling frequency, which can be calculated similarly using the formula above. A 0u , A Idc .

[0015] According to the monitoring method of the ultra-micro DC monitoring device provided by the present invention, the proportional system number between the sensor and the sampled value is:

[0016] Therefore, compared with the prior art, the ultra-micro DC monitoring device and its monitoring method proposed in this invention have the following beneficial effects: 1. This invention enables precise monitoring of microampere-level DC current, solving the problem of insufficient accuracy in traditional monitoring methods and providing more accurate data for insulation status assessment and fault diagnosis of power systems.

[0017] 2. The monitoring device of the present invention uses a metal isolation plate to separate the power board, analog quantity acquisition board and pulse excitation board into different spaces, which effectively reduces electromagnetic interference and improves the stability and reliability of the monitoring device.

[0018] 3. The monitoring method of the present invention has clear physical meaning, simple identification method, good engineering feasibility, and is easy to apply and promote in actual power systems.

[0019] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of an embodiment of an ultra-micro DC monitoring device according to the present invention.

[0021] Figure 2 This is a schematic diagram of the excitation winding method of the two magnetic cores A and B of the sensor and their connection with the device in an embodiment of the ultra-micro DC monitoring device of the present invention.

[0022] Figure 3 This is a schematic diagram of the winding method of the third winding of the sensor and its connection with the device in an embodiment of an ultra-micro DC monitoring device of the present invention. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0024] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0025] An embodiment of an ultra-micro DC monitoring device See Figures 1 to 3 This embodiment provides an ultra-micro DC monitoring device for monitoring ultra-micro DC signals. The device includes a power supply board, a pulse voltage excitation board, a metal isolation board, a data acquisition board, a backplane, and a metal casing. The power board is configured to receive power from an external source, perform voltage conversion, and then guide the converted voltage to the backplane for use by the internal components of the monitoring device. The pulse voltage excitation board is electrically connected to the backplane, obtains power from the backplane and generates a pulse excitation voltage to provide excitation power to the sensors connected to the monitoring device. The acquisition board is electrically connected to the backplane, obtains power from the backplane, and is used to acquire analog signals from the sensors. The metal isolation plate, together with the metal casing, physically divides the inside of the monitoring device into two independent electrical spaces. The power supply board and the acquisition board are placed in the same electrical space, while the pulse voltage excitation board is placed independently in another electrical space to achieve electrical isolation and interference suppression.

[0026] The sensor is an ultra-micro DC inductive sensor, which specifically includes: Both magnetic cores are made of 1J85 permalloy. Three windings: Each magnetic core has a first winding and a second winding with the same number of turns, and the two windings are wound in opposite directions. The two first windings and second windings with opposite directions are connected in series to form an excitation winding. The remaining two ends of the excitation winding are connected to the output port of the pulse voltage excitation board. The third winding is wound on two magnetic cores at the same time and is used as a monitoring winding. Its two ends are connected to the input port of the acquisition board.

[0027] The magnetic core is designed with a square cross-section and a side length of 'a'. The number of turns in the winding on each magnetic core is set to N turns. Based on the geometric relationship between the magnetic core and the winding, the number of turns in the monitoring winding is calculated as follows: (Take positive integers) The magnetic core is a square with side length 'a', so the perimeter is 4a. With N turns, the total length is 4a. N, if the two magnetic cores have the same number of turns and side length, then the total length is 4a. N 2. The winding length of the monitoring winding is kept basically consistent with that of the other two magnetic cores. The purpose is that if the winding length is the same, the overall impedance will remain consistent. Two square magnetic cores stacked together form a rectangle with side lengths a, 2a, a, and 2a respectively. The total side length is 2a + 4a, and the total length is 4a. N 2, then the number of turns is 4a N 2 / (2a+4a).

[0028] An embodiment of a monitoring method for an ultra-micro DC monitoring device This embodiment provides a monitoring method for an ultra-micro DC monitoring device. The method uses the aforementioned ultra-micro DC monitoring device and includes: The pulse excitation voltage frequency search control steps and the ultra-micro DC calculation steps, among which: The pulse excitation voltage frequency search control step is used to apply an initial pulse excitation voltage signal to the excitation winding of the sensor and determine the optimal pulse excitation voltage frequency for powering the excitation winding of the sensor, so as to improve the sensor's sensitivity to ultra-micro DC signals. The ultra-micro DC calculation step is used to calculate the actual input DC signal value based on the signal output from the sensor's monitoring winding; High-precision monitoring of ultra-micro DC signals is achieved by combining the control steps of pulse excitation voltage frequency search with ultra-micro DC calculation steps.

[0029] The pulse excitation voltage frequency search control steps include: A 100μA DC signal is applied to the sensor, allowing the DC signal to pass through the sensor; The pulse excitation voltage output is set to an alternating positive and negative pulse voltage wave with a 50% duty cycle; The frequency fx of the positive and negative voltage waves is increased in increments of 0.01Hz according to a preset time interval until the frequency reaches the preset value, which is generally below 1000Hz or 1000Hz (empirical value). During the frequency increase process, the acquisition board is used to collect and monitor the signal of the winding in real time; The acquired signal is decomposed using the current frequency fx as the fundamental frequency and the component with twice the frequency fx is calculated. As the frequency fx continues to increase, the peak signal curve of the frequency component twice fx is plotted. Find the maximum peak value in the signal peak curve, and determine the frequency of the positive and negative pulse voltage waves corresponding to the maximum peak value as fNx; A fixed frequency fNx and a 50% duty cycle are used to output positive and negative pulse voltages to power the excitation winding of the sensor, thereby determining the optimal pulse excitation voltage frequency for powering the sensor's excitation winding.

[0030] The ultra-micro DC calculation steps include: After the pulse voltage is fixed with fNx as the base frequency and 50% duty cycle, positive and negative pulse voltages are output. A 100μA DC signal is given to the sensor, and the signal output from the monitoring winding is decomposed by FFT. The decomposition yields frequencies of fNx, f2Nx, f4Nx, f6Nx, f8Nx, and f... 10 Nx, with amplitudes of ANx, A2Nx, A4Nx, A8Nx, and A 10 The signal components of Nx, where 2, 4, 6, 8, and 10 represent 2 times, 4 times, 6 times, 8 times, and 10 times the frequency of fNx, respectively; Calculate the root mean square value A of the even-order harmonics corresponding to a given 100μA DC signal. 100μ ; Calculate the root mean square value A of the even harmonics corresponding to a given 0 μA DC signal. 0μ ; Determine the proportionality coefficient k between the sensor output and the sampled value based on the calculation results; When the actual input DC signal is Idc, the root mean square value of the corresponding even harmonic is calculated based on the proportional coefficient. This leads to the actual DC signal value. .

[0031] The root mean square value of the even-order harmonics corresponding to 100uA DC is calculated as follows:

[0032] Where fs is the sampling frequency, and similarly, the above formula is used to calculate... A 0u , A Idc .

[0033] The proportional system number between the sensor and the sampled value is:

[0034] Specifically, in this embodiment, a pulse generator can be used to generate... fNx The signal consists of a fundamental frequency, a positive and negative pulse voltage signal with a 50% duty cycle. The frequency parameters of the pulse generator are set as follows: fNx With a duty cycle parameter of 50%, it alternately outputs positive and negative pulses at set time intervals to form a stable pulse voltage sequence. Connect the sensor to the monitoring device and provide it with a 100μA DC signal. To ensure the stability and accuracy of the DC signal, a high-precision current source can be used. This current source can provide a precise and stable 100μA current output, providing a foundation for subsequent signal monitoring.

[0035] After the pulse voltage is applied to the monitored object, the monitoring winding will output a corresponding electrical signal. This signal contains comprehensive information under the influence of the pulse voltage excitation and the DC signal of the sensor, and is used as the input signal for FFT decomposition.

[0036] Use a data acquisition board to acquire the signal output from the monitoring winding. Set an appropriate sampling frequency that satisfies the Nyquist sampling theorem, i.e., it should be at least twice the highest frequency component of the signal, to ensure that all frequency information of the signal can be accurately acquired.

[0037] The acquired signal data undergoes preliminary processing to eliminate potential noise and interference. Digital filtering methods, such as finite impulse response (FIR) filters or infinite impulse response (IIR) filters, are employed. Based on the characteristics of the signal and the frequency range of the noise, appropriate filter parameters are designed to filter out high-frequency noise and low-frequency interference, making the signal smoother and more stable.

[0038] In practical applications, accurate monitoring of microampere-level DC current is crucial during the operation of power systems. Traditional monitoring methods, due to technological limitations, often exhibit significant errors when measuring minute currents, failing to meet the increasingly sophisticated demands of power systems for insulation condition assessment and fault diagnosis. For example, when evaluating the insulation performance of power equipment, minute current changes may indicate aging of insulation materials or potential faults. Traditional monitoring methods, due to insufficient accuracy, may fail to capture these subtle changes, leading to misjudgments of equipment condition and increasing operational risks to the power system.

[0039] This invention, through the aforementioned technical means, enables precise monitoring of microampere-level DC current. The high-precision sensors and optimized signal processing algorithms employed effectively reduce measurement errors, allowing the power system to acquire more accurate current data and providing a reliable basis for insulation condition assessment and fault diagnosis. For example, by accurately monitoring the minute DC current in transformer insulating oil, abnormal conditions such as partial discharge or moisture absorption within the insulation material can be detected in a timely manner, allowing for proactive maintenance measures to prevent equipment failure and ensure the safe and stable operation of the power system.

[0040] Power systems exhibit various complex electromagnetic environments, and electromagnetic interference (EMI) can severely impact the normal operation of monitoring devices, leading to inaccurate measurement data, degraded device performance, and even system shutdowns. Traditional monitoring devices, due to their unreasonable structural design and lack of effective isolation measures between functional modules, are susceptible to EMI and exhibit poor stability. The monitoring device of this invention uses a metal isolation plate to separate the power supply board, analog signal acquisition board, and pulse excitation board into different spaces, effectively cutting off the propagation path of EMI and reducing electromagnetic coupling between different functional modules. For example, electromagnetic noise generated by the power supply board will not easily interfere with the signal acquisition of the analog signal acquisition board, and the high-frequency signal from the pulse excitation board will not affect other modules. Simultaneously, the metal isolation plate also possesses excellent shielding performance, resisting interference from external electromagnetic fields, further enhancing the anti-interference capability of the monitoring device. This ensures stable and reliable operation of the monitoring device in various harsh electromagnetic environments, reducing measurement errors and equipment failures caused by interference, improving the accuracy and reliability of monitoring data, and providing strong protection for the safe operation of the power system.

[0041] Traditional power monitoring methods often suffer from unclear physical meaning and complex identification methods, making them difficult to understand and operate accurately in practical engineering applications and limiting their widespread adoption. For example, while some complex algorithm models can achieve certain monitoring functions, their unclear physical mechanisms make them difficult for engineers to effectively debug and maintain, increasing application costs and complexity. In contrast, the monitoring method of this invention has clear physical meaning. Based on an understanding of the inherent physical relationship between microampere-level DC current and the insulation state of the power system, it allows for accurate judgment of the insulation state through a simple identification method. For instance, by monitoring the magnitude and trend of DC current at a specific location, combined with known physical models, changes in the performance of the insulation material can be directly inferred.

[0042] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0043] The above embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-substantial changes and substitutions made by those skilled in the art based on the present invention shall fall within the scope of protection claimed by the present invention.

Claims

1. A micro DC monitoring device, characterized in that, The monitoring device is used to monitor ultra-micro DC signals, and includes a power supply board, a pulse voltage excitation board, a metal isolation board, a data acquisition board, a backplane, and a metal casing, wherein: The power board is configured to receive power from an external source, perform voltage conversion, and then guide the converted voltage to the backplane for use by the internal components of the monitoring device. The pulse voltage excitation board is electrically connected to the backplane, obtains power from the backplane and generates a pulse excitation voltage to provide excitation power to the sensors connected to the monitoring device. The acquisition board is electrically connected to the backplane, obtains power from the backplane, and is used to acquire analog signals from the sensors. The metal isolation plate, together with the metal casing, physically divides the inside of the monitoring device into two independent electrical spaces. The power supply board and the acquisition board are placed in the same electrical space, while the pulse voltage excitation board is placed independently in another electrical space to achieve electrical isolation and interference suppression.

2. The apparatus according to claim 1, characterized in that: The sensor is an ultra-micro DC inductive sensor, which specifically includes: Both magnetic cores are made of 1J85 permalloy. Three windings: Each magnetic core has a first winding and a second winding with the same number of turns, and the two windings are wound in opposite directions. The two first windings and second windings with opposite directions are connected in series to form an excitation winding. The remaining two ends of the excitation winding are connected to the output port of the pulse voltage excitation board. The third winding is wound on two magnetic cores at the same time and is used as a monitoring winding. Its two ends are connected to the input port of the acquisition board.

3. The apparatus according to claim 1, characterized in that: The magnetic core is designed with a square cross-section and a side length of 'a'. The number of turns in the winding on each magnetic core is set to N turns. Based on the geometric relationship between the magnetic core and the winding, the number of turns in the monitoring winding is calculated as follows: 。 4. A monitoring method for an ultra-micro DC monitoring device, characterized in that, The method employs the ultra-micro DC monitoring device as described in any one of claims 1-3, comprising: The pulse excitation voltage frequency search control steps and the ultra-micro DC calculation steps, among which: The pulse excitation voltage frequency search control step is used to apply an initial pulse excitation voltage signal to the excitation winding of the sensor and determine the optimal pulse excitation voltage frequency for powering the excitation winding of the sensor, so as to improve the sensor's sensitivity to ultra-micro DC signals. The ultra-micro DC calculation step is used to calculate the actual input DC signal value based on the signal output from the sensor's monitoring winding; High-precision monitoring of ultra-micro DC signals is achieved by combining the control steps of pulse excitation voltage frequency search with ultra-micro DC calculation steps.

5. The method according to claim 4, characterized in that, The pulse excitation voltage frequency search control step includes: A 100μA DC signal is applied to the sensor, allowing the DC signal to pass through the sensor; The pulse excitation voltage output is set to an alternating positive and negative pulse voltage wave with a 50% duty cycle; The frequency fx of the positive and negative voltage waves is increased in steps of 0.01Hz according to a preset time interval until the frequency reaches the preset value. During the frequency increase process, the acquisition board is used to collect and monitor the signal of the winding in real time; The acquired signal is decomposed using the current frequency fx as the fundamental frequency and the component with twice the frequency fx is calculated. As the frequency fx continues to increase, the peak signal curve of the frequency component twice fx is plotted. Find the maximum peak value in the signal peak curve, and determine the frequency of the positive and negative pulse voltage waves corresponding to the maximum peak value as fNx; A fixed frequency fNx and a 50% duty cycle are used to output positive and negative pulse voltages to power the excitation winding of the sensor, thereby determining the optimal pulse excitation voltage frequency for powering the sensor's excitation winding.

6. The method according to claim 5, characterized in that, The ultra-micro DC calculation steps include: After the pulse voltage is fixed with fNx as the base frequency and 50% duty cycle, positive and negative pulse voltages are output. A 100μA DC signal is given to the sensor, and the signal output from the monitoring winding is decomposed by FFT. The decomposition yields frequencies of fNx, f2Nx, f4Nx, f6Nx, f8Nx, and f... 10 Nx, with amplitudes of ANx, A2Nx, A4Nx, A8Nx, and A 10 The signal components of Nx, where 2, 4, 6, 8, and 10 represent 2 times, 4 times, 6 times, 8 times, and 10 times the frequency of fNx, respectively; Calculate the root mean square value A of the even-order harmonics corresponding to a given 100μA DC signal. 100μ ; Calculate the root mean square value A of the even harmonics corresponding to a given 0 μA DC signal. 0μ ; Determine the proportionality coefficient k between the sensor output and the sampled value based on the calculation results; When the actual input DC signal is Idc, the root mean square value of the corresponding even harmonic is calculated based on the proportional coefficient. This leads to the actual DC signal value. .

7. The method according to claim 6, characterized in that: The root mean square value of the even-order harmonics corresponding to 100uA DC is calculated as follows: in, fs This represents the sampling frequency, which can be calculated similarly using the formula above. A 0u , A Idc .

8. The method according to claim 6, characterized in that, The proportional system number between the sensor and the sampled value is: 。

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