Calibration compensation method for non-contact direct current voltage measuring device

Abstract

The application provides a calibration compensation method for a non-contact DC voltage measuring device. In a calibration stage, the non-contact DC voltage measuring device is in a plurality of calibration coupling states, a known calibration voltage is applied to a measured conductor in each calibration coupling state, and a calibration signal is obtained. According to the ratio of the first channel calibration signal and the second channel calibration signal in each calibration coupling state, a ratio characteristic quantity corresponding to each calibration coupling state is determined. Voltage compensation parameters corresponding to each calibration coupling state are determined. A calibration mapping relationship is established and stored. In a real-time measurement stage, a measurement signal is obtained. According to the ratio of the current first channel measurement signal and the current second channel measurement signal, a current ratio characteristic quantity is determined. According to the current ratio characteristic quantity, the calibration mapping relationship is called to obtain a current voltage compensation parameter. According to the current voltage compensation parameter, the current first channel measurement signal is compensated to obtain an output value of the measured DC voltage.

Description

Technical Field

[0001] This invention belongs to the field of non-contact voltage measurement and calibration technology, specifically relating to a calibration compensation method for a non-contact DC voltage measuring device. Background Technology

[0002] Non-contact voltage measurement calculates the voltage by sensing the electric field signal around the conductor being measured. It has advantages such as no need to disconnect power, no direct contact with high-voltage lines, and high safety. It can be applied to fields such as power line inspection, industrial monitoring, smart homes, and electrical equipment condition monitoring.

[0003] Ideally, the electric field distribution around the conductor under test has a definite relationship with the relative position of the probe to the conductor. The output signal of the sensing unit is related to the local electric field strength or electric field coupling state, so the measured voltage can be inverted based on the induced signal. However, in actual systems, factors such as edge effects, parasitic capacitance, input impedance, circuit nonlinearity, temperature and humidity changes, wire diameter, insulation thickness, probe mounting posture, and surrounding grounding bodies can cause the input-output relationship to deviate from the ideal model. Relying solely on theoretical formulas to calculate the measured voltage can easily lead to large measurement errors.

[0004] Among existing calibration methods, one common approach is single-point linear calibration, which measures the induced signal at a known distance and voltage, obtains a single proportionality coefficient, and uses it for subsequent measurements. This method is simple to implement, but its accuracy drops significantly when the actual measured distance differs from the calibration distance, or when the system exhibits significant nonlinear errors. Another approach is multi-point linear interpolation, which collects data at multiple distances and voltages and establishes a lookup table with distance or single-channel output as the primary index. This method improves measurement accuracy to some extent, but it typically does not fully utilize the ratio information between the two electric field induction channels, making it difficult to achieve automatic compensation when the distance or electric field coupling state changes. Furthermore, it still lacks systematic processing in terms of calibration data acquisition, compensation model construction, and real-time compensation applications.

[0005] Therefore, in non-contact DC voltage measurement scenarios with wide range and wide distance, there is a need for a technical solution that can use the information from dual electric field sensing channels to characterize the distance or electric field coupling state and perform calibration compensation accordingly, so as to improve the voltage measurement accuracy under different measurement distances and different coupling states. Summary of the Invention

[0006] To address the shortcomings and deficiencies of existing technologies, this invention provides a calibration compensation method and apparatus for a non-contact DC voltage measurement device. This method is applicable to a non-contact DC voltage measurement system with a first electric field induction channel and a second electric field induction channel. During the calibration phase, the measuring device is placed in multiple different electric field coupling states, and a known calibration voltage is applied in each coupling state, acquiring calibration signals from both electric field induction channels. The ratio between the two calibration signals forms a ratio characteristic quantity characterizing the coupling state between the measuring device and the conductor being measured. Simultaneously, voltage compensation parameters are determined based on the correspondence between the known calibration voltage and the first channel calibration signal, and a calibration mapping relationship is established with the ratio characteristic quantity as an index and the voltage compensation parameters as the output. In the real-time measurement phase, the measuring device determines the current ratio characteristic quantity based on the current signals from the two electric field induction channels, and obtains the current voltage compensation parameters by calling the pre-established calibration mapping relationship. These voltage compensation parameters are then used to compensate the current first channel measurement signal, thereby obtaining the output value of the measured DC voltage. This scheme transforms the dual-channel ratio from a simple signal processing quantity into an index quantity of the electric field coupling state, and associates this index quantity with the voltage conversion compensation parameter of the first channel signal. This enables non-contact voltage measurement to compensate for distance changes, coupling state changes, and system nonlinearity errors without explicitly solving for the actual distance.

[0007] The specific technical solution adopted by this invention to solve its technical problem is as follows:

[0008] To address the problems in existing non-contact DC voltage measurements, which are easily affected by changes in the distance between the probe and the conductor being measured, variations in the electric field coupling state, and system nonlinearity, this invention provides a calibration and compensation method and apparatus for a non-contact DC voltage measurement device. This scheme utilizes the ratio between the output signals of the first and second electric field induction channels to characterize the electric field coupling state between the measuring device and the conductor being measured, and establishes a calibration mapping relationship between the ratio characteristic quantity and the voltage compensation parameters through experimental calibration. During real-time measurement, the current ratio characteristic quantity is obtained based on the current dual-channel signals. This ratio characteristic quantity is then used to call the pre-established calibration mapping relationship to obtain the current voltage compensation parameters. Finally, the measurement signal of the first electric field induction channel is compensated according to the current voltage compensation parameters to obtain the output value of the measured DC voltage.

[0009] The voltage compensation parameters may include calibration coefficients, or calibration coefficients and residual bias; wherein, the calibration coefficients are used to characterize the proportional relationship between the first channel signal and the measured voltage under the current coupling state, and the residual bias is used to compensate for the residual offset in the linear model.

[0010] The calibration mapping relationship can be a one-dimensional mapping from the ratio characteristic quantity to the voltage compensation parameter, or a two-dimensional mapping with the ratio characteristic quantity and the first channel signal as input and the measured voltage as output.

[0011] The key concept of this invention lies in using the relative response relationship of the two electric field sensing channels as an index of the coupling state, rather than directly using the ratio of the two channels as the measured voltage output. The signal of the first electric field sensing channel is mainly used to carry the amplitude information of the measured voltage, while the ratio between the first and second electric field sensing channels is used to reflect the relative response differences caused by changes in the distance, relative position, or other electric field coupling conditions between the probe and the conductor being measured. By calibrating and associating this ratio characteristic with voltage compensation parameters, suitable voltage compensation parameters can be selected or calculated based on the current coupling state without explicitly solving for the actual distance, thereby reducing the impact of distance changes and non-ideal electric field coupling on the measurement results.

[0012] The calibration and compensation method provided by this invention is applicable to non-contact DC voltage measuring devices including a first electric field induction channel and a second electric field induction channel. The method includes a calibration stage and a real-time measurement stage.

[0013] During the calibration phase, the non-contact DC voltage measuring device is placed in multiple calibration coupling states. In each calibration coupling state, a known calibration voltage is applied to the conductor under test, and the first channel calibration signal of the first electric field induction channel and the second channel calibration signal of the second electric field induction channel are acquired. The calibration coupling states represent the electric field coupling conditions between the non-contact DC voltage measuring device and the conductor under test. These electric field coupling conditions can be influenced by factors such as measurement distance, relative position, installation orientation, the structure of the conductor under test, or surrounding electric field boundary conditions.

[0014] In this invention, the calibration coupling state refers to the electric field coupling condition between the non-contact DC voltage measuring device and the conductor under test. Specifically, multiple calibration coupling states can be formed by changing the distance between the probe and the conductor under test; in other ways, different calibration coupling states can also be formed by changing the relative position, installation orientation, conductor specifications, or surrounding electric field boundary conditions.

[0015] Based on the ratio of the first channel calibration signal to the second channel calibration signal under each calibration coupling state, a ratio characteristic quantity corresponding to each calibration coupling state is determined. This ratio characteristic quantity is used to characterize the coupling state between the non-contact DC voltage measuring device and the conductor being measured. Since both electric field sensing channels are affected by the amplitude of the measured voltage under the same measured voltage, and the two channels have different responses due to differences in spatial position, electric field coupling strength, or sensing structure, the relative response information related to the coupling state can be extracted by the ratio between the two signals. Therefore, this ratio characteristic quantity can be used as an index variable for subsequent retrieval of voltage compensation parameters.

[0016] Based on the known correspondence between the calibration voltage and the first channel calibration signal under each calibration coupling state, voltage compensation parameters are determined for each calibration coupling state. These voltage compensation parameters are used to convert the first channel signal into the measured DC voltage. Thus, the dual-channel ratio is used to identify the current coupling state, the first channel signal provides voltage amplitude information, and the voltage compensation parameters complete the voltage conversion compensation under the current coupling state; these three elements work together to form a calibration compensation chain.

[0017] A calibration mapping relationship is established and stored, using the ratio characteristic quantity as the index variable and the voltage compensation parameter as the mapping output. This calibration mapping relationship can be represented by a discrete data table, a fitting function, or other callable data structures to record the correspondence between the ratio characteristic quantity and the voltage compensation parameter under different coupling states. Since this correspondence originates from actual calibration data, factors that are difficult to fully theoretically model, such as edge effects, parasitic parameters, channel gain differences, circuit nonlinearity, and installation environment, can be incorporated into the compensation process.

[0018] During the real-time measurement phase, the current first channel measurement signal of the first electric field induction channel and the current second channel measurement signal of the second electric field induction channel are acquired. The current ratio characteristic quantity is determined based on the ratio of the current first channel measurement signal to the current second channel measurement signal. Subsequently, the current voltage compensation parameter is obtained by calling the pre-stored calibration mapping relationship based on the current ratio characteristic quantity, and the current first channel measurement signal is compensated according to the current voltage compensation parameter to obtain the output value of the measured DC voltage.

[0019] Furthermore, the multiple calibration coupling states can be formed by changing the distance between the non-contact DC voltage measuring device and the conductor under test. Changes in distance alter the coupling strength between the electric field induction channel and the conductor under test, causing changes in the relative response of the two channels. By calibrating at different distances, the correspondence between the ratio characteristic quantity covering a predetermined range of use and the voltage compensation parameters can be obtained, enabling the automatic recall of compensation parameters adapted to the current distance or coupling state based on the current ratio characteristic quantity during real-time measurement.

[0020] Furthermore, in each calibration coupling state, multiple known calibration voltages of different amplitudes can be applied to the conductor under test, and the first-channel calibration signal and the second-channel calibration signal corresponding to each known calibration voltage can be obtained. At least one of the following methods—averaging, median filtering, or outlier removal—is applied to the multiple ratios obtained under the same calibration coupling state to obtain the ratio characteristic quantity corresponding to that calibration coupling state. By acquiring data from multiple voltage points under the same coupling state and performing statistical processing, the influence of random noise, occasional interference, or abnormal sampling points on the ratio characteristic quantity can be reduced, and the stability of the ratio characteristic quantity under that coupling state can be verified.

[0021] Furthermore, the first channel calibration signal, the second channel calibration signal, the current first channel measurement signal, and the current second channel measurement signal can all be corrected signals obtained by subtracting the zero-point output of the corresponding channel from the original output signal of the corresponding channel. Zero-point correction can reduce the impact of channel bias, amplifier zero drift, static offset comparison value calculation, and voltage compensation. The zero-point output can be obtained during the factory calibration stage, under no-electric-field or shielded conditions, or updated according to the equipment's operating status.

[0022] Furthermore, before determining the ratio characteristic or the current ratio characteristic, it can be determined whether the absolute value of the second channel calibration signal or the current second channel measurement signal reaches a preset signal threshold. When the second channel signal does not reach the preset signal threshold, the corresponding data is marked as invalid data, or a measurement anomaly prompt is output during the real-time measurement phase. This processing can prevent abnormal amplification in the ratio calculation when the second channel signal is too weak, thereby improving the reliability of the ratio characteristic and the real-time measurement results.

[0023] Furthermore, the voltage compensation parameters may include calibration coefficients. These calibration coefficients can be obtained by fitting a zero-crossing linear model between the known calibration voltage and the first channel calibration signal. This method is suitable for cases where zero-point compensation is sufficient and residual bias is negligible. In the case of residual system offset, the voltage compensation parameters may also include calibration coefficients and residual bias, which can be obtained by fitting a linear model with intercept between the known calibration voltage and the first channel calibration signal. Through the above methods, a suitable voltage conversion model can be selected based on the actual relationship between the first channel signal and the measured voltage.

[0024] Furthermore, when obtaining the current voltage compensation parameters by calling the calibration mapping relationship based on the current ratio characteristic, two mapping nodes adjacent to the current ratio characteristic can be found in the calibration mapping relationship, and linear interpolation can be performed based on the voltage compensation parameters corresponding to the two mapping nodes. Through linear interpolation, continuously changing compensation parameters can be obtained with a limited number of calibration points. When the current ratio characteristic exceeds the effective range of the calibration mapping relationship, boundary value clamping can be used to determine the current voltage compensation parameters, or an out-of-range warning can be output to reduce the risk of errors that may arise from unfounded extrapolation.

[0025] Furthermore, the calibration mapping relationship can be stored in at least one of the following forms: discrete mapping table, piecewise linear function, polynomial function, or neural network model. Discrete mapping tables are easy to look up and retrieve, and are suitable for controllers with limited computing resources; piecewise linear functions can approximate the mapping relationship with lower computational cost within a segmented range; polynomial functions can reduce the amount of table data by storing fitting coefficients; neural network models can be used to fit mapping relationships with a high degree of nonlinearity. The specific form used can be selected based on the system's degree of nonlinearity, storage resources, and computing power.

[0026] Furthermore, the calibration mapping relationship can also include a two-dimensional calibration mapping relationship with the ratio characteristic quantity and the first channel calibration signal as inputs and the known calibration voltage as the output. During the real-time measurement phase, the current first channel measurement signal can be compensated using the two-dimensional calibration mapping relationship based on the current ratio characteristic quantity and the current first channel measurement signal, and the output value of the measured DC voltage can be determined. This method is suitable for situations where there is significant voltage-dependent nonlinearity between the first channel signal and the measured voltage, and can simultaneously utilize coupling state information and first channel signal amplitude information for compensation.

[0027] Furthermore, at least one of the auxiliary information, including temperature, humidity, and the polarity of the measured voltage, can be acquired. When the auxiliary information includes at least one of temperature and humidity, the calibration mapping relationship or the current voltage compensation parameter can be corrected based on at least one of temperature and humidity to reduce the impact of environmental condition changes on the measurement results. When the auxiliary information includes the polarity of the measured voltage, the sign of the output value of the measured DC voltage can be determined based on the polarity of the measured voltage, thereby outputting a signed DC voltage measurement result.

[0028] This invention also provides a non-contact DC voltage measuring device. The device includes a dual electric field sensing unit, a storage unit, and a signal processing unit. The dual electric field sensing unit includes a first electric field sensing channel and a second electric field sensing channel, used to sense the electrostatic field generated by the DC voltage being measured and output a corresponding electrical signal. The storage unit stores a calibration mapping relationship with a ratio characteristic quantity as an index variable and a voltage compensation parameter as the mapping output. The signal processing unit is configured to acquire the current first channel measurement signal of the first electric field sensing channel and the current second channel measurement signal of the second electric field sensing channel; determine the current ratio characteristic quantity based on the ratio of the current first channel measurement signal to the current second channel measurement signal; obtain the current voltage compensation parameter based on the calibration mapping relationship in the storage unit; compensate the current first channel measurement signal based on the current voltage compensation parameter; and output the output value of the DC voltage being measured.

[0029] Compared to existing technologies, this invention and its preferred embodiment utilize the ratio between the first and second electric field induction channels to characterize the electric field coupling state between the measuring device and the conductor under test. This ratio characteristic is used as an index to call voltage compensation parameters, freeing measurement compensation from dependence on fixed installation distances or a single linear proportional coefficient. This improves the adaptability of non-contact DC voltage measurement under different distances and coupling states. By establishing a mapping relationship between the ratio characteristic and voltage compensation parameters during the calibration phase, the influences that are difficult to fully theoretically model, such as edge effects, parasitic parameters, channel gain differences, circuit nonlinearity, and environmental changes, can be absorbed into the calibration compensation process, thereby reducing the errors caused by relying solely on ideal models to invert voltage. Furthermore, through preferred solutions such as multi-voltage calibration, ratio statistical processing, zero-point correction, validity judgment, interpolation compensation, boundary processing, two-dimensional mapping, environmental parameter compensation, and polarity output, the stability of calibration data, the reliability of real-time compensation, and the engineering applicability of measurement results can be enhanced. This method has a clear flow and is suitable for integration with storage and signal processing units to form a real-time non-contact DC voltage measuring device. Attached Figure Description

[0030] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments:

[0031] Figure 1 This is a flowchart illustrating the calibration data acquisition process in an embodiment of the present invention.

[0032] Figure 2 This is a flowchart illustrating the real-time measurement and table lookup compensation process in an embodiment of the present invention. Detailed Implementation

[0033] To make the features and advantages of the present invention more apparent and understandable, specific embodiments are described below in detail:

[0034] It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used in this specification have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0035] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0036] (I) Overview of the Plan

[0037] This invention provides a nonlinear calibration and compensation method for non-contact DC voltage measurement devices, applicable to voltage sensors with dual electric field sensing channels. The method utilizes the ratio of the output signals from two sensing channels with different spatial positions or electric field coupling characteristics to characterize the distance or equivalent coupling state between the probe and the conductor being measured. A nonlinear mapping relationship between this ratio and calibration coefficients is established through experimental calibration. During real-time measurement, the ratio is calculated based on the current dual-channel output, and the corresponding calibration coefficients are obtained through table lookup or interpolation. The measured voltage is then calculated by combining this with the output amplitude of the first sensing channel. This method eliminates the need for explicit calculation of the actual distance between the probe and the conductor being measured, achieving automatic compensation and system nonlinear correction under varying distances, effectively improving the accuracy of non-contact voltage measurements over a wide range and distance.

[0038] In an idealized approximation model, the corrected outputs of the first and second electric field induction channels can be expressed as:

[0039]

[0040]

[0041] in, and These are the correction outputs for the first and second sensing channels, respectively. The voltage being measured. The distance between the probe and the conductor being measured. and These are the equivalent gains of the two channels, respectively. and These are the electric field coupling functions of the two channels, which are related to the distance.

[0042] From this, the ratio of the two channels can be obtained:

[0043]

[0044] Within the predetermined conductor specifications, probe orientation, installation boundary conditions, and measurement range, the ratio It can be used as an equivalent characteristic or index quantity for distance or coupling state. Gain differences, edge effects, and other non-ideal factors between the two channels can be absorbed through subsequent experimental calibration.

[0045] (ii) Applicable non-contact DC voltage measuring devices

[0046] The non-contact DC voltage measuring device to which this invention applies includes a dual electric field sensing unit and a signal processing unit. The dual electric field sensing unit is used to sense the electrostatic field generated by the DC voltage being measured and outputs two electrical signals related to the electric field strength or electric field coupling state.

[0047] As a further preferred embodiment, the dual-field sensing unit can employ a chopper-modulated dual-field sensing structure. This structure includes two spatially different metal sensing electrodes, an electronic chopper switch, a signal conditioning circuit, and a reference signal generator. The two sensing electrodes can be arranged front-to-back or in other fixed spatial relationships, with a constant distance between them. The electrode diameter can be designed from 5mm to 20mm depending on the range and sensitivity requirements; this size range is preferred and does not constitute a limitation on the scope of protection of this invention. The electronic chopper switch can be a CMOS analog switch or other equivalent switching device, periodically modulating the connection state between the sensing electrode and the reference potential or signal conditioning circuit at a frequency of 1kHz to 10kHz, converting the induced charge corresponding to the static electric field into an alternating electrical signal. The signal conditioning circuit includes a low-noise preamplifier, a bandpass filter, a synchronous demodulator, and a low-pass filter. The synchronous demodulator uses a reference signal of the same frequency generated by the reference signal generator for demodulation, outputting a DC signal related to the static electric field strength. This structure can convert the static electric field into a stably detectable AC modulated signal, and the polarity of the measured voltage can be determined through the phase information of the synchronous demodulation result.

[0048] As another preferred embodiment, the dual electric field sensing unit can also employ an electrometer-type dual electric field sensing structure. This structure includes two metal sensing electrodes and two high-input-impedance charge amplifiers or electrometer amplifiers. Each sensing electrode is connected to a high-input-impedance detection circuit composed of a JFET-input or MOSFET-input operational amplifier, with the input impedance preferably not lower than [missing information]. The feedback capacitor can be selected from 1pF to 10pF, and the feedback resistor can be selected from 1GΩ to 10GΩ. Under the conditions of a clear reference potential, good insulation, reasonable shielding, and leakage control, the electrostatic field generated by the measured DC voltage forms a measurable charge or potential change on the sensing electrode. The charge amplifier or electrometer amplifier converts this into an output voltage. The amplitude of the output signal is related to the local electric field, and the sign can be used to reflect the polarity of the measured voltage. It should be noted that the innovation of this invention lies in the back-end nonlinear calibration and compensation method. The front-end dual electric field sensing unit can also be implemented using field milling, vibration electrode, MEMS modulation, or other existing electric field sensing structures. This invention is not limited to a specific front-end structure.

[0049] (III) Calibration Experiment Design and Data Acquisition

[0050] The complete procedure for the calibration experiment in this embodiment is as follows: Figure 1 As shown. First, a calibration platform is built, and the conductor to be measured is fixed on a precisely movable displacement stage. An adjustable DC standard power supply is connected to provide a known standard voltage. The dual electric field induction probe is then fixedly installed, and the distance between the probe and the conductor to be measured is adjusted. Let the calibration distance range be... If equal-interval calibration is used, then the first... The calibration distance is:

[0051]

[0052] in, For the first A calibration distance, For the minimum calibration distance, For the maximum calibration distance, The distance step size, This specifies the number of distance points to be calibrated. As a non-limited example, It can be set to 5 to 10, and the calibration distance can be selected as 5mm, 10mm, 15mm, 20mm, 30mm, 40mm, or 50mm.

[0053] For each calibration distance Apply sequentially to cover the entire measurement range A known DC voltage ,in As a non-limiting example, It can be set to 6 to 10, and the calibration voltage can be selected as 5V, 12V, 24V, 48V, 110V, or 220V. At each calibration point... Below, record the raw output of the first channel. Second channel raw output ,in Indicates the first The distance, the first The original output of the first channel at the rated voltage. This indicates the original output of the corresponding second channel.

[0054] (iv) Data preprocessing and mapping relationship construction

[0055] After data acquisition, the data is preprocessed. First, zero-point correction is performed by pre-measuring the zero-point output of both channels under zero-voltage or no-electric-field conditions. and Zero-point correction is performed on the raw output at each calibration point, and the calculation formula is as follows:

[0056]

[0057]

[0058] in, and These are the first and second channel outputs after zero-point correction, respectively. As a further preferred embodiment, the zero-point output... and Measurements can be taken and stored during factory calibration, and automatic updates can be performed in the field under conditions of no electric field or shielding. When temperature drift is significant, a compensation model for zero-point variation with temperature can be established. ,in , For temperature.

[0059] Then calculate the dual-channel ratio at each measurement point. The calculation formula is:

[0060]

[0061] To avoid abnormal ratios caused by excessively small output from the second channel, only when the following conditions are met... If the ratio is valid, it is considered valid; otherwise, it is marked as invalid data. The preset threshold can be dynamically set based on system noise level, ADC resolution, and full-scale range. This is a non-limiting example. It can be taken as approximately 1% of the full-scale output. Define the first... The set of effective voltage points at a distance is The number of valid samples is When the number of valid samples If the number is less than the preset number, the calibration data of that distance point will not be included in the mapping table construction, or the data of that distance point will be re-collected.

[0062] For the same calibration distance Calculate the eigenvalues ​​of all effective ratios. The calculation formula is:

[0063]

[0064] As a further preferred implementation, outliers can be removed first using the Grubbs criterion, the three-standard-deviation criterion, or median filtering before calculating the average value, thus improving the robustness of the ratio. Since the dual-channel ratio primarily reflects the distance or equivalent coupling state between the probe and the conductor being measured, the ratio corresponding to different calibration voltages at the same calibration distance will vary. They should be basically the same. If at the same distance... Follow Significant changes indicate the presence of voltage-related nonlinearity in the system. In this case, a two-dimensional voltage mapping mode is preferred. The process of establishing the two-dimensional mapping relationship is similar to that of the one-dimensional mapping relationship; it simply requires converting the one-dimensional... Extended to two dimensions Dataset.

[0065] Next, the mapping relationship is constructed. This invention provides two mapping modes, which can be selected according to the system's nonlinearity and accuracy requirements. The first is a one-dimensional coefficient mapping mode, suitable for scenarios where the output of the first channel is approximately linear with the measured voltage at a fixed distance. When zero-point compensation is sufficient and residual bias can be ignored, a zero-crossing linear model is adopted. The calibration coefficients are obtained using the least squares method. :

[0066]

[0067] Establish eigenratio With calibration coefficient Correspondence between To form a one-dimensional mapping table .

[0068] When residual zero-point bias or system offset exists, a linear model with intercept can be used. ,in For the first The residual bias term at a given calibration distance. Let Define the mean of the effective samples. and Then, by using the least squares method, we can obtain:

[0069]

[0070]

[0071] At this time, it is necessary to establish simultaneously. and The mapping relationship, the corresponding mapping table is as follows .

[0072] In this invention, the measured characteristic ratio and calibration coefficients typically exhibit a nonlinear relationship, which can be stored in a discrete table or fitted as a continuous function. The second method is a two-dimensional voltage mapping mode, suitable for systems with strong voltage-related nonlinearities. This mode directly establishes the dual-channel ratio. First channel correction output With the voltage being measured Two-dimensional mapping relationship between A two-dimensional mapping dataset can be represented as This mode can simultaneously compensate for errors caused by distance variations and nonlinear errors in the voltage direction, making it suitable for scenarios where the front-end circuit exhibits nonlinearity, channel gain varies with voltage, or high accuracy is required across a wide measurement range.

[0073] The completed mapping table and related parameters are stored in the microcontroller's non-volatile memory. The storage capacity of a one-dimensional mapping table is typically no more than 2KB, which is sufficient to meet the storage requirements of a typical microcontroller.

[0074] (v) Real-time measurement and compensation process

[0075] The real-time measurement process is as follows: Figure 2 As shown. First, the raw output signals of the first and second channels are acquired in real time. and Zero-point correction is performed in the same manner as in the calibration phase to obtain the corrected channel signal. and If a temperature compensation model exists, the current temperature will be used. Correcting the zero point, that is ,in .

[0076] Check if the absolute value of the second channel correction signal meets the requirements. If the condition is not met, an invalid signal or alarm will be output. If the condition is met, the currently valid dual-channel ratio will be calculated. .

[0077] Look up the ratio to the current value in the pre-stored mapping table. Two adjacent entries and ,satisfy Their corresponding calibration coefficients are respectively and If an intercept model is used, the corresponding bias term is: and When satisfied When defining the interpolation factor The current calibration coefficient is:

[0078]

[0079] If an intercept model is used, the current bias term is:

[0080]

[0081] If the current ratio If the value exceeds the calibration range, boundary values ​​are used for clamping calculation, and an out-of-range warning is output to avoid large errors caused by unfounded extrapolation. The interpolation calculation process is simple and efficient, with an execution time of no more than 1ms on a typical microcontroller, which can meet the requirements of real-time measurement.

[0082] Preferably, the feature ratio can be verified during the calibration phase. Whether there is monotonicity or unique correspondence within the predetermined distance range; if there is a non-monotonic interval, the effective measurement range can be limited, auxiliary characteristic quantities can be added, or a two-dimensional voltage mapping mode can be adopted.

[0083] The amplitude of the measured voltage is calculated based on the calibration coefficients and the corrected first channel signal. For the zero-crossing linear model, the calculation formula is:

[0084]

[0085] For linear models with intercepts, the calculation formula is:

[0086]

[0087] like If the signal is a signed demodulated value, the above formula can directly output the signed voltage. If... If only the amplitude is represented, then the polarity sign of the output from the front-end signal processing unit should be considered. Obtain signed output:

[0088]

[0089] Or in the intercept model:

[0090]

[0091] in For the two-dimensional voltage mapping mode, based on the current ratio... and the first channel correction signal The measured voltage can be directly obtained in a two-dimensional mapping table through bilinear interpolation (bilinear interpolation calculation between four adjacent grid points in the two-dimensional mapping table). .

[0092] (vi) Nonlinear enhancement methods and accuracy iteration

[0093] To further optimize the nonlinear compensation effect, various fitting methods can be used to approximate the mapping relationship. The ratio... The effective range is divided into several intervals. ,in A linear function is used in each interval. Perform fitting, where and The first The slope and intercept of each interval can reduce storage space while ensuring accuracy.

[0094] A polynomial function is used to fit the entire mapping relationship, and the calculation formula is as follows:

[0095]

[0096] in These are the polynomial fitting coefficients. Since the order is a polynomial, only the coefficients need to be stored, further reducing storage requirements.

[0097] For highly nonlinear systems, a small neural network can be used to approximate the mapping relationship. In the one-dimensional coefficient mapping mode, it can be represented as... In the two-dimensional voltage mapping mode, it can be represented as ,in The parameter is The neural network model can adopt lightweight structures such as 1-3-1 and 2-m-1. After offline training, the network weight parameters are stored in the microcontroller for fast inference during real-time measurement.

[0098] After calibration, the measurement accuracy is tested using verification data that was not used in the calibration. For the first... There are 1 verification point, and the relative error is defined as:

[0099]

[0100] in For the first Measurement output at each verification point This corresponds to the reference voltage. If it satisfies... If the verification point meets the accuracy requirement, then the verification point is considered to meet the accuracy requirement. The preset error threshold is used. If the verification error exceeds the preset threshold, iterative optimization can be achieved by increasing the density of calibration points, changing the fitting model, optimizing the data preprocessing method, adding temperature and humidity compensation, or performing rapid on-site recalibration.

[0101] As a further preferred embodiment, if changes in temperature and humidity significantly affect the sensor output, a temperature-sensitive element can be introduced. and humidity As a compensation variable, the one-dimensional coefficient mapping pattern can be extended to... If an intercept model is used, it is further extended to The corresponding voltage is calculated as follows or The two-dimensional voltage mapping mode can be extended to... .

[0102] Compared to existing technologies, the solutions provided in the embodiments of this invention firstly establish a nonlinear mapping relationship based on experimental data, bypassing the complex and difficult-to-accurate theoretical electric field model. This effectively compensates for errors caused by various practical factors such as edge effects, parasitic parameters, circuit nonlinearity, and probe structural non-ideality. Provided that the calibration point density, sensor signal-to-noise ratio, installation orientation, environmental conditions, and front-end linearity meet the requirements, this invention is expected to control the measurement error across the entire range within the target accuracy range.

[0103] Secondly, by using the dual-channel ratio to characterize the distance or equivalent coupling state between the probe and the conductor under test, automatic compensation under distance changes can be achieved without the need for the user to input the actual distance or to explicitly solve the distance through complex theoretical formulas. This solves the problem that traditional single-point calibration methods cannot adapt to distance changes.

[0104] Furthermore, it provides a complete engineering workflow, covering all aspects including calibration experiment design, data acquisition, zero-point correction, anomaly detection, mapping relationship construction, data storage, real-time lookup table compensation, and accuracy verification iteration, demonstrating strong operability and engineering feasibility. It also supports both one-dimensional coefficient mapping and two-dimensional voltage mapping modes, as well as various nonlinear fitting methods such as piecewise linear, polynomial, and neural networks, allowing for flexible selection based on different accuracy requirements and hardware resources. One-dimensional lookup tables and linear interpolation can be implemented on ordinary 8-bit or 32-bit microcontrollers, while two-dimensional lookup tables, polynomial fitting, and neural networks can be implemented using fixed-point, lookup table, or offline training followed by online inference methods, depending on the microcontroller's computing power, making it suitable for mass production and low-cost applications.

[0105] Furthermore, this invention supports rapid on-site recalibration and can perform personalized calibration for specific installation distances, wire specifications, and environmental conditions, further improving measurement accuracy and environmental adaptability in practical use.

[0106] It should be noted that, unless otherwise defined, the technical or scientific terms used in this invention should have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms "first," "second," and similar terms used in this invention do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "comprising" or "including" mean that the element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0107] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

[0108] This invention is not limited to the preferred embodiment described above. Anyone inspired by this invention can derive various other calibration and compensation methods for non-contact DC voltage measuring devices. All equivalent variations and modifications made within the scope of the claims of this invention should be included within the scope of this invention.

Claims

1. A calibration compensation method for a non-contact DC voltage measuring device, the non-contact DC voltage measuring device comprising a first electric field sensing channel and a second electric field sensing channel, characterized in that, The method includes: During the calibration phase, the non-contact DC voltage measuring device is placed in multiple calibration coupling states. A known calibration voltage is applied to the conductor under test in each calibration coupling state to obtain the first channel calibration signal of the first electric field induction channel and the second channel calibration signal of the second electric field induction channel. Based on the ratio of the first channel calibration signal to the second channel calibration signal under each calibration coupling state, the ratio characteristic quantity corresponding to each calibration coupling state is determined. The ratio characteristic quantity characterizes the coupling state between the non-contact DC voltage measuring device and the conductor under test. Based on the correspondence between the known calibration voltage and the first channel calibration signal under each calibration coupling state, determine the voltage compensation parameters corresponding to each calibration coupling state. Establish and store a calibration mapping relationship with the ratio characteristic quantity as the index variable and the voltage compensation parameter as the mapping output; During the real-time measurement phase, the current first channel measurement signal of the first electric field sensing channel and the current second channel measurement signal of the second electric field sensing channel are acquired, and the current ratio feature quantity is determined based on the ratio of the current first channel measurement signal to the current second channel measurement signal. The current voltage compensation parameters are obtained by calling the calibration mapping relationship based on the current ratio characteristic value; The current first channel measurement signal is compensated according to the current voltage compensation parameters to obtain the output value of the measured DC voltage.

2. The calibration compensation method for a non-contact DC voltage measurement device according to claim 1, characterized in that: The multiple calibration coupling states are formed by changing the distance between the non-contact DC voltage measuring device and the conductor being measured.

3. The calibration compensation method for a non-contact DC voltage measurement device according to claim 1, characterized by: In each of the calibration coupling states, multiple known calibration voltages of different amplitudes are applied to the conductor under test, and the first channel calibration signal and the second channel calibration signal corresponding to each known calibration voltage are obtained. By performing at least one of the following processing methods on multiple ratios obtained under the same calibration coupling state: averaging, median filtering, or outlier removal, the ratio characteristic quantity corresponding to that calibration coupling state is obtained.

4. The calibration compensation method for a non-contact DC voltage measurement device according to claim 1, characterized by: The first channel calibration signal, the second channel calibration signal, the current first channel measurement signal, and the current second channel measurement signal are all correction signals obtained by subtracting the zero-point output of the corresponding channel from the original output signal of the corresponding channel. Before determining the ratio characteristic or the current ratio characteristic, it is determined whether the absolute value of the second channel calibration signal or the current second channel measurement signal reaches a preset signal threshold. Data that does not reach the preset signal threshold is marked as invalid data or a measurement abnormality prompt is output.

5. The calibration and compensation method for a non-contact DC voltage measuring device according to claim 1, characterized in that: The voltage compensation parameters include calibration coefficients, which are obtained by fitting a zero-crossing linear model between a known calibration voltage and a first channel calibration signal; or, the voltage compensation parameters include calibration coefficients and residual bias, which are obtained by fitting a linear model with intercept between a known calibration voltage and a first channel calibration signal.

6. The calibration and compensation method for a non-contact DC voltage measuring device according to claim 1, characterized in that: When the current voltage compensation parameter is obtained by calling the calibration mapping relationship based on the current ratio feature, two mapping nodes adjacent to the current ratio feature are found in the calibration mapping relationship, and linear interpolation is performed based on the voltage compensation parameters corresponding to the two mapping nodes; when the current ratio feature exceeds the effective range of the calibration mapping relationship, the current voltage compensation parameter is determined by boundary value clamping, or an out-of-range prompt is output.

7. The calibration and compensation method for a non-contact DC voltage measuring device according to claim 1, characterized in that: The calibration mapping relationship is stored in at least one of the following forms: discrete mapping table, piecewise linear function, polynomial function, or neural network model.

8. The calibration and compensation method for a non-contact DC voltage measuring device according to claim 1, characterized in that: The calibration mapping relationship also includes a two-dimensional calibration mapping relationship with the ratio feature quantity and the first channel calibration signal as input and the known calibration voltage as output; in the real-time measurement stage, the current first channel measurement signal is compensated by the two-dimensional calibration mapping relationship according to the current ratio feature quantity and the current first channel measurement signal, and the output value of the measured DC voltage is determined.

9. The calibration and compensation method for a non-contact DC voltage measuring device according to claim 1, characterized in that: Further acquire at least one of the auxiliary information, including temperature, humidity, and polarity information of the measured voltage; when the auxiliary information includes at least one of temperature and humidity, correct the calibration mapping relationship or the current voltage compensation parameter according to at least one of temperature and humidity; when the auxiliary information includes polarity information of the measured voltage, determine the sign of the output value of the measured DC voltage according to the polarity information of the measured voltage.

10. A non-contact DC voltage measuring device, characterized in that, It includes a dual electric field sensing unit, a storage unit, and a signal processing unit; The dual electric field sensing unit includes a first electric field sensing channel and a second electric field sensing channel, which are used to sense the electrostatic field generated by the DC voltage being measured and output a corresponding electrical signal. The storage unit is used to store the calibration mapping relationship with the ratio characteristic quantity as the index variable and the voltage compensation parameter as the mapping output; The signal processing unit is configured to acquire the current first channel measurement signal of the first electric field sensing channel and the current second channel measurement signal of the second electric field sensing channel, determine the current ratio feature based on the ratio of the current first channel measurement signal to the current second channel measurement signal, obtain the current voltage compensation parameter based on the calibration mapping relationship in the storage unit, compensate the current first channel measurement signal based on the current voltage compensation parameter, and output the output value of the measured DC voltage.

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