Digital non-contact ac voltage sensor and voltage measurement method

Abstract

The application provides a kind of digital non-contact AC voltage sensor and voltage measurement method, sensor includes open type AC voltage probe, and the sensing component in the inside of probe is based on the principle of capacitive voltage division, and the high voltage on the wire is converted into the first voltage analog signal, and the interference protection is provided by the external ground shielding layer.Signal output by probe is sent to signal acquisition module, and the signal conditioning circuit in the module first carries out filtering, direct current isolation and amplification to signal, generates the second voltage analog signal more easily handled.Subsequently, the main control unit integrated with analog-digital converter converts the signal into digital sampling value, and finally the measurement result is output in the form of digital signal by communication unit.The sensor realizes safe, convenient AC high voltage detection through non-contact measurement and full digital processing, and can output stable, anti-interference digital signal.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of power monitoring, and particularly relates to a digital non-contact AC voltage sensor and a voltage measurement method. BACKGROUND

[0002] Daily monitoring, equipment maintenance and fault diagnosis of a power system are key links for guaranteeing safe and stable operation of a power grid, and accurate measurement of AC voltage of a line or a terminal of equipment is a basic and frequent operation. Existing voltage measurement technologies, especially in the field of non-contact measurement, although avoid the risk of direct physical contact with a high-voltage conductor, still face the challenge that operation convenience and measurement accuracy are difficult to be balanced in actual application.

[0003] At present, common non-contact voltage probes on the market mostly adopt a ring-shaped closed structure. Such a probe can provide good electromagnetic shielding and ensure high measurement accuracy, but the closed structure also brings inherent limitations. When measuring an installed cable, an operator must first power off the circuit, then detach one end of the cable from the terminal, pass through the closed aperture of the probe, and then reconnect after measurement. This process is not only cumbersome, time-consuming and labor-intensive, but more importantly, the power-off operation will interrupt the normal operation of the equipment or system, which may cause unnecessary economic losses. In some continuous production or critical power supply situations where power-off is not allowed, such a probe cannot be used. SUMMARY

[0004] The application provides a digital non-contact AC voltage sensor and a voltage measurement method to solve the above technical problems.

[0005] In a first aspect, the application provides a digital non-contact AC voltage sensor, comprising:

[0006] An open-type AC voltage probe, the open-type AC voltage probe has an openable and closable clamping structure for non-contact accommodation of a to-be-measured wire inside; the open-type AC voltage probe is internally provided with a sensing assembly based on a capacitive voltage division principle, the sensing assembly converts high voltage on the to-be-measured wire into a first voltage analog signal; the open-type AC voltage probe further comprises a grounding shielding layer, the grounding shielding layer is wrapped outside the sensing assembly;

[0007] A signal acquisition module, an input end of the signal acquisition module is connected with an output end of the open-type AC voltage probe;

[0008] The signal acquisition module comprises:

[0009] signal conditioning circuit, configured to receive and filter, direct-current isolate and amplify the first voltage analog signal to generate a second voltage analog signal;

[0010] a master control unit integrated with an analog-to-digital converter, configured to convert the second voltage analog signal into digital sample values;

[0011] a communication unit connected to the master control unit, configured to output the measurement results processed by the master control unit in the form of digital signals.

[0012] Optionally, the signal conditioning circuit comprises a first signal processing channel and a second signal processing channel.

[0013] When the signal conditioning circuit receives the first voltage analog signal, the first voltage analog signal is input to the first signal processing channel and the second signal processing channel simultaneously.

[0014] The first signal processing channel is configured with a first amplification factor for processing signals within a first preset voltage range.

[0015] The second signal processing channel is configured with a second amplification factor different from the first amplification factor for processing signals within a second preset voltage range.

[0016] The master control unit adaptively selects channel data corresponding to an effective measurement range for processing according to the output signals of the first signal processing channel and the second signal processing channel.

[0017] Optionally, the sensor further comprises a power module, which comprises:

[0018] a first-stage DC-DC conversion circuit configured to convert an external direct-current power supply into a first internal direct-current voltage;

[0019] a second-stage DC-DC conversion circuit configured to convert the first internal direct-current voltage into an operating voltage for the master control unit and the signal conditioning circuit;

[0020] a voltage reference circuit configured to generate a reference voltage for an operational amplifier in the signal conditioning circuit as a bias voltage and for the analog-to-digital converter as a reference.

[0021] In a second aspect, the present application further provides a digital non-contact AC voltage measurement method, which is applied to a sensor comprising an open-type AC voltage probe and a signal acquisition module, the open-type AC voltage probe is internally provided with symmetrically divided first and second electrode segments, and the signal acquisition module is integrated with a master control unit and a communication unit, and the method comprises the following steps:

[0022] a first voltage analog signal and a second voltage analog signal related to the voltage of the conductor under test are synchronously induced and collected by the first electrode segment and the second electrode segment based on the principle of capacitive voltage division;

[0023] the first voltage analog signal and the second voltage analog signal are converted into a first digital signal and a second digital signal by the master control unit, and a main amplitude signal representing the voltage amplitude and a position offset factor representing the radial position of the conductor under test in the probe are calculated according to the first digital signal and the second digital signal;

[0024] if the absolute value of the position offset factor is less than or equal to a preset effective installation threshold, it is determined that the installation state of the open-type AC voltage probe is effective, and the main amplitude signal and the position offset factor are taken as inputs to obtain a compensated voltage measurement value by querying a two-dimensional correction model preset in the master control unit and performing calculation;

[0025] the compensated voltage measurement value is output externally through the communication unit.

[0026] Optionally, the calculation of the main amplitude signal representing the voltage amplitude and the position offset factor representing the radial position of the conductor under test in the probe according to the first digital signal and the second digital signal comprises the following steps:

[0027] the first digital signal and the second digital signal are summed to obtain the main amplitude signal representing the voltage amplitude;

[0028] the first digital signal and the second digital signal are subtracted to obtain a difference signal;

[0029] the difference signal is normalized with the main amplitude signal to obtain the position offset factor.

[0030] Optionally, the method further comprises the following steps:

[0031] if the absolute value of the position offset factor is greater than the effective installation threshold, it is determined that the installation state of the open-type AC voltage probe is invalid;

[0032] the main amplitude signal and the position offset factor calculated in the current collection period are discarded, and an alarm signal is generated by the master control unit;

[0033] the alarm signal is output externally through the communication unit.

[0034] Optionally, the step of inputting the main amplitude signal and the position offset factor into the two-dimensional correction model pre-stored in the master control unit and performing calculation to obtain the compensated voltage measurement value comprises the following steps:

[0035] Positioning the main amplitude signal and the position offset factor as target coordinates to four adjacent reference grid points in the two-dimensional correction model pre-stored in the master control unit;

[0036] Reading reference voltage values pre-stored in the four reference grid points;

[0037] Based on the relative position relationship between the target coordinates and the four reference grid points, performing weighted calculation on the four reference voltage values by using a bilinear interpolation algorithm to obtain the compensated voltage measurement value.

[0038] Optionally, the method further comprises the following steps:

[0039] Receiving a self-calibration trigger instruction in a state that the open-type AC voltage probe does not accommodate any to-be-measured conductor;

[0040] In response to the self-calibration trigger instruction, collecting no-load signals generated by the first electrode segment and the second electrode segment, and converting the no-load signals into first baseline digital signals and second baseline digital signals respectively;

[0041] Storing the first baseline digital signals and the second baseline digital signals as baseline bias values, which are used for calibrating the first digital signals and the second digital signals.

[0042] Optionally, the two-dimensional correction model is generated by the following steps:

[0043] Moving the to-be-measured conductor to a plurality of pre-stored radial position points inside the open-type AC voltage probe by using an actuator;

[0044] At each radial position point, applying a plurality of standard voltage values to the to-be-measured conductor by using a standard voltage source;

[0045] At each combined calibration point composed of a radial position point and a corresponding standard voltage value, calculating a set of calibration main amplitude signals and calibration position offset factors;

[0046] Establishing a mapping relationship between the standard voltage values and the corresponding set of calibration main amplitude signals and calibration position offset factors;

[0047] Solidifying the mapping relationship into the two-dimensional correction model and pre-storing the two-dimensional correction model in the master control unit.

[0048] Optionally, the step of outputting the compensated voltage measurement value to the outside by using the communication unit comprises the following steps:

[0049] acquiring a plurality of compensated voltage measurement values in a continuous measurement cycle;

[0050] storing the plurality of compensated voltage measurement values in a data buffer queue;

[0051] performing a sliding average digital filtering algorithm on the data in the data buffer queue to generate a filtered final voltage measurement value;

[0052] encapsulating the final voltage measurement value into a data frame conforming to a predetermined communication protocol and transmitting the data frame to an external device through the communication unit.

[0053] The present application has the following advantages:

[0054] By combining a unique open-type AC voltage probe with a signal acquisition module with built-in intelligent algorithms, safe, convenient and high-precision voltage measurement of AC conductors is achieved without the need to disconnect the electrical circuit. The open-type clamping structure of the probe greatly simplifies the on-site installation steps, avoiding the power loss and operational complexity caused by threading the traditional closed-type probe. The internally integrated ground shielding layer, especially the preferred solution containing a permalloy material layer, provides excellent electromagnetic shielding for the sensing assembly, effectively suppressing external noise interference in complex industrial environments and ensuring the purity of signal acquisition. The multi-channel parallel processing circuit used in the signal acquisition module performs segmented amplification for different voltage ranges, ensuring excellent measurement linearity and resolution in a wide dynamic range of 50V to 500V. The core main control unit not only takes charge of data acquisition and conversion, but also actively identifies and compensates for potential measurement errors introduced by the uncertainty of the relative position between the probe and the conductor, fundamentally solving the technical pain point that the precision of traditional open-type sensors is easily affected by installation methods. BRIEF DESCRIPTION OF DRAWINGS

[0055] Figure 1 is a schematic diagram of the application scenario of the digital non-contact AC voltage sensor in one embodiment of the present application.

[0056] Figure 2 is a structural schematic diagram of the open-type AC voltage probe in one embodiment of the present application.

[0057] Figure 3 is a complete structural schematic diagram of the digital non-contact AC voltage sensor in one embodiment of the present application.

[0058] Figure 4 is a connection schematic diagram of the signal acquisition module and the power supply module in one embodiment of the present application.

[0059] Figure 5Fig. 1 is a flowchart of a digital non-contact AC voltage measurement method according to an embodiment of the present application. DETAILED DESCRIPTION

[0060] The technical solutions in the embodiments of the present application will be clearly described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art belong to the scope of protection of the present application.

[0061] The terms "first", "second", and the like in the specification and claims of the present application are used to distinguish similar objects, and are not used to describe a specific order or sequence. It should be understood that the data used in this way can be exchanged under appropriate circumstances, so that the embodiments of the present application can be implemented in an order other than those illustrated or described herein, and the objects distinguished by "first", "second", and the like are generally of a kind and do not limit the number of objects, for example, the first object can be one or more. In addition, "and / or" in the specification and claims indicates at least one of the connected objects, and the character " / ", generally indicates that the front and rear associated objects are in an "or" relationship.

[0062] The embodiments of the present application provide a digital non-contact AC voltage sensor, as shown in Fig. 1, in a typical industrial application scenario, the digital non-contact AC voltage sensor can be conveniently deployed on the measured conductor in the power distribution cabinet, and the measurement data is transmitted to the terminal device in real time through the RS485 communication bus, to complete the remote online monitoring of the field voltage. The sensor is mainly composed of an open type AC voltage probe and a signal acquisition module in physical structure, and the two work cooperatively to form a complete link from physical signal capture to digital information output. Figure 1

[0063] Referring to Fig. 1, the digital non-contact AC voltage sensor is mainly composed of an open type AC voltage probe and a signal acquisition module, and the two work cooperatively to form a complete link from physical signal capture to digital information output. Figure 2 ​, the core feature of the probe is the open design, this openable clamping structure allows the operator to directly and conveniently buckle the probe on the primary conductor to be measured without the need to power off or disconnect the circuit. This design fundamentally solves the pain points of traditional closed sensor which must be threaded, resulting in cumbersome operation, time-consuming and laborious, and possible production interruption. The probe is internally provided with a sensing component based on the principle of capacitive voltage division, which is the key to realizing high voltage to low voltage signal conversion. Specifically, when the primary conductor is placed inside the probe, the conductor, one or more sensing electrodes (illustrated as a voltage division ring) inside the probe, and the internal reference ground of the probe form an equivalent capacitor network composed of input coupling capacitor C1 and reference capacitor C2. The high voltage U1 on the measured conductor is divided on this capacitor network, inducing a first voltage analog signal U2 on the sensing electrode which is proportional to it and much smaller in amplitude.

[0064] As shown in Figure 2 , in order to ensure the accuracy and anti-interference of the measurement, the outside of the sensing component is covered with a complete ground shielding layer, i.e. the shielding cover in the figure. The ground shielding layer is connected to the circuit ground of the signal acquisition module through electrical connection, forming a Faraday cage structure that can effectively isolate the electric field noise in the external space from the internal sensing capacitor. In order to further improve the anti-interference performance in more complex electromagnetic environment of industrial field, a layer of permalloy material layer is specially added in the ground shielding layer in a preferred embodiment of the present application. As a soft magnetic material with extremely high magnetic permeability and low coercivity, permalloy can provide a low magnetic resistance path for electromagnetic interference such as power frequency magnetic field, thereby bypassing it from around the sensitive sensing component, achieving precise electromagnetic shielding of the sensing head, which provides a solid physical guarantee for obtaining pure first voltage analog signal.

[0065] The input end of the signal acquisition module is connected to the output end of the open-type alternating voltage probe, responsible for receiving the first voltage analog signal and converting it to digital output after processing. Referring to Figure 3 , specifically, after the first voltage analog signal is input from the probe to the signal acquisition module, it will first enter a signal conditioning circuit. The function of the signal conditioning circuit is to perform a series of necessary preprocessing on the first voltage analog signal to generate a second analog signal suitable for subsequent digital acquisition. These preprocessing steps usually include: first, filtering through an RC filter network to filter out noise and interference components higher than the power frequency; then, direct current isolation through a direct current isolation capacitor to eliminate possible direct current bias in the signal and ensure that only pure alternating signal components are processed; finally, the signal is amplified by the core operational amplifier, because the signal induced from the probe is usually very weak and must be fully amplified to be effectively recognized by the analog-to-digital converter.

[0066] In order to achieve high-precision measurement in a wide voltage range (e.g. 50V-500V), the signal conditioning circuit of the present application preferably adopts a multi-channel parallel processing design. As shown in Figure 4 and Figure 5 The signal conditioning circuit includes at least two parallel signal processing channels, i.e. a first signal processing channel and a second signal processing channel. The signals input from the probe and after preliminary filtering and direct current isolation will enter these two channels at the same time. The core of each channel is an operational amplifier, such as operational amplifier A and operational amplifier B in the figure. The circuit topologies of the two channels can be completely consistent, but the key parameter, i.e. the amplification factor, is set to different values through different resistance configurations. For example, the first signal processing channel (with operational amplifier A as the core) is configured with a first amplification factor, which is relatively high and is specially used for accurate measurement of signals in a lower voltage range (e.g. 50V-150V); while the second signal processing channel (with operational amplifier B as the core) is configured with a second amplification factor, which is relatively low and is used to prevent signal saturation distortion when measuring a higher voltage range (e.g. 150V-500V). The two second analog signals (Vout1 and Vout2) generated after amplification by the two channels will be sent to the main control unit (MCU) at the same time.

[0067] The main control unit in this embodiment can adopt a high-performance single-chip microcomputer, and the main control unit is internally integrated with an analog-to-digital converter (ADC) for converting the input two-channel second analog signals into digital sampling values. The firmware program of the main control unit will analyze the digital sampling values of the two channels in real time, determine the range of the current measured voltage through intelligent algorithms, and adaptively select the channel data corresponding to the effective measurement range for processing. After completing all digital operations, the main control unit will obtain an accurate voltage measurement result. Finally, the measurement result will be sent to the communication unit connected to the main control unit, which is responsible for outputting the measurement result processed by the main control unit in the form of digital signals. In this embodiment, the communication unit is a 485 module.

[0068] In the present embodiment, the sensor further comprises a power module, which includes a first-stage DC-DC conversion circuit, for example, composed of chip TPS54302, responsible for converting an external wide-range direct-current power supply (for example, 12 V) into a stable first internal direct-current voltage (for example, 4.2 V). Subsequently, the first internal direct-current voltage is sent to a second-stage DC-DC conversion circuit, for example, composed of chip TPS63802, for more precise voltage conversion, which is further converted into a lower-noise working voltage (for example, 3.3 V) required by the system core, which is directly supplied to the digital part of the main control unit and the signal conditioning circuit. However, for high-precision analog circuits, an absolutely accurate reference is also required. For this purpose, the power module further specifically integrates a voltage reference circuit, for example, composed of a special voltage reference chip AZ31LAN. The circuit generates a high-stability reference voltage (for example, 3.0 V) with extremely small temperature drift and extremely low noise, with the relatively stable 3.3 V working voltage as input. This reference voltage has a dual role: on the one hand, it is supplied to the operational amplifier in the signal conditioning circuit as a bias voltage, ensuring that the amplification process of the analog signal will not drift due to power fluctuations; on the other hand, it is also directly connected to the ADC reference pin of the main control unit MCU as a reference during analog-to-digital conversion, fundamentally ensuring the accuracy of the entire measurement link.

[0069] Figure 5 A flowchart of the digital non-contact AC voltage measurement method in one embodiment. Figure 5 The digital non-contact AC voltage measurement method shown is applied to a sensor comprising an open-type AC voltage probe and a signal acquisition module, the open-type AC voltage probe being internally provided with symmetrically divided first and second electrode segments, and the signal acquisition module being internally integrated with a main control unit and a communication unit. It should be understood that, although Figure 5 The steps in the flowchart are shown in sequence according to the arrows, but these steps are not necessarily executed in the order indicated by the arrows. Unless otherwise specified herein, the execution of these steps is not strictly limited in sequence, and these steps can be executed in other orders. Moreover, Figure 5 At least part of the steps in the flowchart can include multiple sub-steps or multiple stages, which are not necessarily executed at the same time, but can be executed at different times, and the execution order of these sub-steps or stages is not necessarily sequential, but can be executed in rotation or alternation with at least part of other steps or sub-steps or stages of other steps. For example, Figure 5 As shown, the digital non-contact AC voltage measurement method disclosed specifically includes the following steps:

[0070] S101. Non-contacting the to-be-tested conductor in the open-type AC voltage probe, based on the principle of capacitive voltage division and through the first electrode segment and the second electrode segment, synchronously sensing and collecting the first voltage analog signal and the second voltage analog signal generated in relation to the voltage of the to-be-tested conductor.

[0071] The core principle of which is to utilize the capacitive coupling effect between the alternating electric field around the to-be-tested conductor and the symmetrically arranged sensing electrodes in the probe. In specific implementation, the operator opens the clamping structure of the probe, places the to-be-tested conductor inside, and after closing, the conductor forms input coupling capacitors with the first electrode segment and the second electrode segment inside the probe respectively. The values of the two capacitors will differ due to the different radial positions of the conductor relative to the two electrode segments. To accurately capture this instantaneous state, the main control unit will synchronously sample the voltages induced on the two electrode segments under the same clock pulse, thereby generating two time-fully-corresponding first voltage analog signal and second voltage analog signal.

[0072] S102. Using the main control unit to convert the first voltage analog signal and the second voltage analog signal into first digital signal and second digital signal, and calculating the main amplitude signal representing the voltage amplitude and the position offset factor representing the radial position of the to-be-tested conductor in the probe according to the first digital signal and the second digital signal.

[0073] The main control unit processes the two acquired analog signals, first sampling and quantizing the first voltage analog signal and the second voltage analog signal into first digital signal Va and second digital signal Vb through the internal analog-to-digital converter (ADC), and then the firmware program in the main control unit performs parallel calculation on the two digital signals according to the preset algorithm to decouple the information. A specific implementation is to calculate the main amplitude signal Vs and the position offset factor Pf through the following formula:

[0074]

[0075] Vs mainly reflects the overall strength of the measured voltage, and Pf, through normalization processing, eliminates the influence of the voltage amplitude itself and becomes a dimensionless index related only to the relative position of the conductor.

[0076] S103. If the absolute value of the position offset factor is less than or equal to the preset effective installation threshold, it is determined that the installation state of the open-type AC voltage probe is effective, and the main amplitude signal and the position offset factor are taken as input to obtain the compensated voltage measurement value by querying the two-dimensional correction model preset in the main control unit and performing calculation.

[0077] wherein the absolute value of the calculated position offset factor Pf is compared with an effective installation threshold value Pt preset in the master control unit. If |Pf| is less than or equal to Pt, it is determined that the installation state of the current probe is within the effective and compensable range. At this time, the master control unit inputs the master amplitude signal Vs and the position offset factor Pf calculated in the previous step as two independent coordinates to query a two-dimensional correction model pre-calibrated through experiments and stored in its internal. The model stores the mapping relationship between different (Vs, Pf) combinations and the true voltage value. By querying the model and performing interpolation and other operations, a dynamically compensated voltage measurement value Vc can be obtained.

[0078] S104. The compensated voltage measurement value is output externally through the communication unit.

[0079] wherein the compensated voltage measurement value Vc is output externally through the communication unit, which is the final link in the entire intelligent measurement process. The principle is to encapsulate the high-precision digital results obtained through complex operations in the master control unit into a standardized data format, and reliably transmit them to external devices through physical channels. A specific embodiment is that the master control unit packages the final compensated voltage measurement value Vc into a complete data frame according to the Modbus communication protocol widely used in the industry. In addition to containing the core voltage data, the data frame also includes device address, function code, and CRC code for error checking. Subsequently, the master control unit sends the data frame to the communication unit, such as an RS-485 transceiver chip, through its UART interface. The chip is responsible for converting the signal into a differential signal with extremely strong anti-interference ability, and outputting it externally through a twisted pair.

[0080] In one embodiment, calculating the master amplitude signal representing the voltage amplitude and the position offset factor representing the radial position of the measured conductor in the probe from the first digital signal and the second digital signal includes the following steps:

[0081] Summing the first digital signal and the second digital signal to obtain the master amplitude signal representing the voltage amplitude;

[0082] Subtracting the first digital signal and the second digital signal to obtain the difference signal;

[0083] Normalizing the difference signal and the master amplitude signal to obtain the position offset factor.

[0084] In this embodiment, after the main control unit converts the analog signals from the two symmetrical electrode segments into a first digital signal Va and a second digital signal Vb, the primary calculation step is to sum these two digital signals. The principle behind this step is that when the tested conductor undergoes radial displacement within the probe, its coupling capacitance with one electrode segment increases (leading to signal enhancement), while its coupling capacitance with the other electrode segment decreases (leading to signal weakening). This inverse relationship ensures that the sum of the two signals remains relatively stable within a certain displacement range. Specifically, the arithmetic logic unit (ALU) of the main control unit executes a simple addition instruction to obtain the main amplitude signal Vs using the following formula: This initially reduces the measurement fluctuations caused by the uncertainty of the conductor position at the algorithm level, thus obtaining a preliminary measurement value that more stably reflects the true strength of the measured voltage than any single signal.

[0085] While acquiring the main amplitude signal, the difference between the first digital signal Va and the second digital signal Vb is calculated in parallel. This step aims to initially extract raw information directly related to the conductor's position offset. The principle is that the signal difference between the two symmetrical electrode segments directly reflects the degree and direction of the conductor's deviation from its geometric center. When the conductor is centered, Va and Vb are theoretically equal, with a difference of zero; when the conductor shifts to one side, the absolute value of the difference increases with the shift, and its sign indicates the direction of the shift. Specifically, the main control unit executes a subtraction instruction to obtain the differential signal Vd using the following formula: This makes the positional information implicit in the two signals explicit, generating an intermediate variable that can initially quantify the positional shift.

[0086] Finally, the differential signal Vd and the main amplitude signal Vs are normalized. This crucial step aims to completely eliminate the interference of the measured voltage amplitude on position determination, thereby obtaining a pure quantitative index that is only related to the relative position of the conductor. The principle is that dividing a position-related quantity (differential signal) by a quantity primarily related to voltage amplitude (main amplitude signal) eliminates the common amplitude influence. Specifically, the main control unit executes a division instruction to obtain the position offset factor Pf using the following formula: This step ultimately yields a unique, dimensionless index that varies between -1 and +1 and can precisely characterize the radial position of the conductor.

[0087] In one embodiment, the method further includes the following steps:

[0088] If the absolute value of the position offset factor is greater than the effective installation threshold, the installation status of the open-type AC voltage probe is determined to be invalid.

[0089] discard the main amplitude signal and the position offset factor calculated in the current acquisition cycle, and generate an alarm signal through the master control unit;

[0090] output the alarm signal to the outside through the communication unit.

[0091] In this embodiment, if the wire offset is too large, the electric field distribution of the sensor will be distorted, exceeding the correction capability of the preset model. At this time, forced compensation will produce misleading results. Therefore, a boundary condition, i.e. an effective installation threshold Pt, is needed for comparison. If it is determined that |Pf| is greater than Pt, it means that the physical position of the wire has exceeded the tolerance limit designed by the sensor, and the installation state of the open-type alternating voltage probe is determined to be invalid. Once it is determined that the installation state is invalid, the master control unit will immediately perform a series of cascading response actions to prevent the further spread of false data and provide immediate feedback to the user. One specific embodiment is that the firmware program in the master control unit will trigger an interrupt or jump instruction, skipping all subsequent compensation operations and normal data output processes. At the same time, the main amplitude signal Vs and the position offset factor Pf calculated in the current acquisition cycle are cleared from the memory or register, or marked as invalid, to prevent them from being used incorrectly in other calculations. Next, the master control unit will generate an internal alarm signal. After generating the internal alarm signal, the alarm information must be effectively transmitted to the external user or upper system to prompt human intervention.

[0092] In one embodiment, the main amplitude signal and the position offset factor are inputted, and the compensated voltage measurement value is obtained by querying the two-dimensional correction model preset in the master control unit and performing operations as follows:

[0093] The main amplitude signal and the position offset factor are taken as target coordinates, and are positioned to four adjacent reference grid points in the two-dimensional correction model preset in the master control unit;

[0094] The pre-stored reference voltage values in the four reference grid points are read;

[0095] Based on the relative position relationship between the target coordinates and the four reference grid points, the four reference voltage values are weighted and operated by using a bilinear interpolation algorithm to obtain the compensated voltage measurement value.

[0096] In this embodiment, when the installation state is determined to be valid, the measured data can be accurately corrected using a pre-established mathematical model capable of describing the error distribution of the sensor under different working conditions. One specific implementation is to take the main amplitude signal Vs and the position offset factor Pf as a target coordinate (Vs, Pf). The main control unit queries a two-dimensional correction model pre-stored in its non-volatile flash memory in this coordinate system. The model is a two-dimensional lookup table (2D-LUT) in form. When querying, the algorithm searches for a minimum rectangular grid containing the target coordinate in the table, and the four vertices of the grid are the adjacent reference grid points, represented as (V1, P1), (V2, P1), (V1, P2), (V2, P2) respectively.

[0097] After locating the four adjacent reference grid points, the main control unit reads the pre-stored reference voltage values corresponding to the four grid points from the two-dimensional correction model. These reference voltage values are the true values measured by applying standard voltage at each grid point during the calibration stage before the sensor is shipped, and they represent the most accurate measurement results at these discrete points. One specific implementation is that the main control unit directly reads the reference voltage values corresponding to the four grid points (V1, P1), (V2, P1), (V1, P2), (V2, P2) respectively through memory address indexing, denoted as Q11, Q21, Q12, Q22. Assuming that the voltage value changes linearly within the small surface formed by the four reference grid points, the distance can be used to determine the weight of the four reference voltage values, and finally the relative position relationship between the target coordinate and the four reference grid points can be used to perform weighted operation to obtain the final compensated voltage measurement value. Specifically, the bilinear interpolation algorithm can be used to first calculate the relative position of the target coordinate (Vs, Pf) in two axial directions, and then perform linear interpolation twice. The final compensated voltage measurement value Vc can be calculated by the following formula based on the core idea:

[0098]

[0099] where t and u are the normalized distances in two axial directions calculated based on the coordinates of the target coordinate (Vs, Pf) and the four reference grid points, taking values between 0 and 1. Through smooth mathematical interpolation, the discrete reference true values are converted into continuous and accurate compensation values serving specific working conditions, thereby eliminating the nonlinear error introduced by position offset at the algorithm level and achieving high-precision dynamic compensation.

[0100] In one embodiment, the sensor further includes at least one auxiliary physical sensor for monitoring the current environmental variables, and the method further includes the following steps of adaptively correcting the two-dimensional correction model:

[0101] The real-time environmental variable parameter is obtained through an auxiliary physical sensor while the bilinear interpolation operation is being performed.

[0102] Under the preset reference measurement condition, a compensation residual error between the compensation output generated by the two-dimensional correction model and the theoretical model output is identified;

[0103] The compensation residual error is associated with the real-time environmental variable parameter and is provided as input to an online learning model;

[0104] An operation is performed through the online learning model to generate a set of dynamic compensation parameters for correcting the output of the two-dimensional correction model;

[0105] Based on the dynamic compensation parameters and the real-time environmental variable parameter, a secondary compensation operation is performed on the compensated voltage measurement value obtained through the bilinear interpolation operation to generate an adaptive and compensated final voltage measurement value.

[0106] In the present embodiment, to realize the self-adaptation and self-optimization of the sensor, an environmental perception process is started in parallel while the conventional dynamic compensation is performed. The principle is that the performance of electronic components will drift due to the influence of environmental factors such as temperature, thereby causing the deviation of the solidified correction model, and thus the real-time monitoring of these variables is needed as the basis for subsequent correction. A specific implementation is that, in the same measurement period in which the main control unit performs the bilinear interpolation operation, the current real-time environmental variable parameter Te is collected through an auxiliary physical sensor integrated in the sensor. This parameter can be temperature, humidity or a combination thereof. Thus, the sensor is endowed with environmental perception capability, so that each measurement is associated with not only the voltage and position information but also a snapshot of the then environmental state, thereby providing key and synchronous data input for analyzing and compensating the measurement drift caused by environmental changes.

[0107] When the sensor works under the preset reference measurement condition, for example, the absolute value of the position offset factor Pf is extremely small (close to zero), indicating that the wire is almost perfectly centered, the main control unit calculates the compensation output Vc generated by the two-dimensional correction model, and simultaneously calculates a simplified theoretical model output Vt which is only related to the main amplitude signal Vs. Then, the compensation residual error Er is calculated through the following formula: By performing internal comparison under the most ideal physical installation condition, the compensation residual error of the current solidified model caused by environmental drift and other factors is successfully quantified, thereby providing a clear and explicit optimization target for the online learning algorithm, i.e., the residual error tends to zero by adjusting the parameters.

[0108] After obtaining the compensation residual Er and the corresponding environmental variable parameter Te, the data pair (Te, Er) is provided as input to a lightweight online learning model, such as a recursive least square (RLS) algorithm. The algorithm updates and optimizes one or more internal weight coefficients in real time according to each new input sample, and these coefficients collectively constitute a dynamic model that can describe the environmental impact. After processing the latest data sample, the recursive least square (RLS) algorithm outputs a set of updated dynamic compensation parameters, such as the slope parameter Ks and the intercept parameter Ki. These two parameters together define a linear correction function that describes how much adjustment needs to be made to the original compensation value under different environmental variables Te.

[0109] Finally, based on the generated dynamic compensation parameters, the voltage value obtained by the conventional compensation process is fine-tuned again. Thus, the static model calibrated at the factory is combined with the dynamic model obtained by online learning to achieve complementary advantages. A specific implementation is to substitute the compensated voltage measurement value Vc obtained by bilinear interpolation, the dynamic compensation parameters Ks and Ki output by the online learning model, and the current real-time environmental variable parameter Te into the following secondary compensation formula to obtain the final adaptive compensation voltage measurement value Vf: By adding a dynamic correction amount related to the real-time environment to the original compensation value, the final output voltage value not only corrects the error introduced by the position offset, but also compensates for the drift error caused by environmental changes. This allows the sensor to maintain high measurement accuracy throughout its life cycle.

[0110] In one embodiment, the method further includes the following steps:

[0111] In the state that the open-type AC voltage probe does not accommodate any measured wire, a self-calibration trigger instruction is received;

[0112] In response to the self-calibration trigger instruction, a no-load signal generated by the first electrode segment and the second electrode segment is collected and converted into a first baseline digital signal and a second baseline digital signal, respectively;

[0113] The first baseline digital signal and the second baseline digital signal are stored as baseline bias values, which are used to calibrate the first digital signal and the second digital signal.

[0114] In this embodiment, a self-calibration procedure can be performed to eliminate the zero-point error introduced by the DC bias, thermal noise or slow drift of the sensor's own electronic components before the regular measurement task is carried out. In one specific embodiment, a self-calibration trigger command is sent to the main control unit through an external button, communication instruction or specific power-on timing when the open-type AC voltage probe is not clamped to any live conductor, i.e. in a completely unloaded natural state. The command initiates a pre-set calibration program. The main control unit starts collecting and processing the unloaded signals immediately after receiving the self-calibration trigger command. The main control unit drives its internal analog-to-digital converter (ADC) to continuously and synchronously collect the weak unloaded signals generated by the first electrode segment and the second electrode segment in the unloaded state for a pre-set period of time (e.g. hundreds of sampling periods). Subsequently, the collected signal samples are converted into digital form and averaged to eliminate the effects of random noise, and finally a stable first baseline digital signal B1 and a second baseline digital signal B2 are obtained.

[0115] After the baseline digital signals of the two channels are calculated, they are stored as baseline bias values and used for real-time calibration in subsequent measurements. In each subsequent regular measurement, the pre-stored static bias is subtracted from the original measurement value, thereby obtaining a pure value reflecting only the change in the true external signal. For example, the main control unit writes the calculated first baseline digital signal B1 and second baseline digital signal B2 to a specific address in its internal non-volatile memory (such as EEPROM or Flash). When the original first digital signal Va and second digital signal Vb are obtained, the following calibration operation to subtract the baseline is performed first:

[0116]

[0117] wherein Va' and Vb' are the calibrated digital signals. Subsequently, all subsequent calculations (such as the main amplitude signal and position offset factor) are based on these two calibrated signals.

[0118] In one embodiment, a two-dimensional correction model is generated by the following steps:

[0119] Using an actuator to move the measured conductor to a plurality of pre-set radial position points inside the open-type AC voltage probe;

[0120] At each radial position point, a plurality of standard voltage values are applied to the measured conductor by a standard voltage source;

[0121] At each combined calibration point consisting of a radial position point and a corresponding standard voltage value, a set of calibration main amplitude signals and calibration position offset factors are calculated;

[0122] establishing a mapping relationship between the standard voltage value and a corresponding set of calibration main amplitude signals and calibration position offset factors;

[0123] solidifying the mapping relationship into a two-dimensional correction model and presetting it in the main control unit.

[0124] In the present embodiment, the sensor to be calibrated is fixed, and a high-precision three-axis actuator (robot arm) driven by a stepper motor is used to hold a section of the measured wire. According to the preset program, the actuator controls the wire to move to dozens or even hundreds of preset radial position points in a grid-like path on the internal cross-section of the open-type AC voltage probe. These position points cover the entire effective measurement area from the geometric center to the allowed offset edge. After the measured wire is accurately positioned at each radial position point, different measured voltages need to be simulated at this position. A high-precision programmable standard voltage source can be used to connect to the measured wire through the wire clamp. While the wire remains stationary at a particular radial position point, the standard voltage source will sequentially apply a series of stable and known standard voltage values covering the entire range of the sensor (e.g. from 50V to 500V, stepping 10V) to the wire according to the program instructions.

[0125] At each combined calibration point, the main control unit of the sensor will collect and convert to obtain a first digital signal and a second digital signal, and use the same algorithm as in actual work to calculate a corresponding set of calibration main amplitude signals Vsc and calibration position offset factors Pfc. At the same time, the standard voltage value Ut applied by the standard voltage source at this moment is recorded. This process is automatically repeated at all combined calibration points. All collected data sets (Vsc, Pfc, Ut) are used as a training data set. Taking Vsc and Pfc as two independent variables and Ut as the dependent variable, a mapping relationship describing the relationship between the three is constructed through data fitting or interpolation algorithm. This mapping relationship can be a complex multivariate polynomial or a discrete data lookup table. The implementation effect of this step is to convert the unordered and large amount of discrete data points into a structured mathematical model with predictive ability, which inherently contains the systematic error information of the sensor under all working conditions.

[0126] Finally, the final determined mapping relationship is organized in the form of a two-dimensional array or lookup table (Lookup Table, LUT) to form a two-dimensional correction model. The two index dimensions of this two-dimensional correction model are the quantized calibration main amplitude signals and the calibration position offset factors, and the content stored in the table is the corresponding standard voltage value. Subsequently, during the production process, the two-dimensional correction model file containing complete data is programmed and burned into the non-volatile flash memory of the main control unit of each sensor.

[0127] In one embodiment, outputting the compensated voltage measurement value to the outside via the communication unit includes the following steps:

[0128] Multiple compensated voltage measurements are acquired within a continuous measurement cycle;

[0129] Store multiple compensated voltage measurements into a data buffer queue;

[0130] A moving average digital filtering algorithm is applied to the data in the data buffer queue to generate the final filtered voltage measurement value.

[0131] The final voltage measurement value is encapsulated into a data frame conforming to a predetermined communication protocol, and the data frame is sent to an external device through the communication unit.

[0132] In this embodiment, the main control unit repeatedly executes the complete measurement and compensation process at a fixed frequency (e.g., 100 times per second). Each process generates a compensated voltage measurement value Vc(i), where i is the sequence number of the measurement cycle. The main control unit continuously generates such a data stream. A fixed-size storage area is allocated in the main control unit's RAM as a data buffer queue. Whenever a new compensated voltage measurement value Vc(i) is generated, it is pushed to the end of the queue; if the queue is full, the oldest data at the head of the queue is discarded. Thus, the queue always stores the results of the most recent N measurement cycles, where N is the length of the queue, i.e., the size of the filtering window. Whenever the data buffer queue is updated, the firmware of the main control unit recalculates the sum of all N data in the queue, divides it by N, and obtains the final filtered voltage measurement value Vout using the following formula: .in, It is the i-th compensated voltage measurement value in the queue. This calculation process continues as the queue slides.

[0133] After generating a stable and smooth final voltage measurement value Vout, the main control unit packages the final voltage measurement value Vout into a complete data frame according to the Modbus RTU protocol commonly used in the industrial field. This data frame has a rigorous structure, typically including the device address for addressing, a function code defining the operation type, bytes indicating the data length, and the core voltage data itself, and finally, a Cyclic Redundancy Check (CRC) code to ensure data integrity. Subsequently, this encapsulated data frame is transmitted to the physical bus through a communication unit, such as an RS-485 transceiver, for external devices to receive.

[0134] Those skilled in the art should understand that the above discussion of any embodiment is only intended to be illustrative and is not intended to be limiting to the scope of the present application; the above embodiments or technical features among different embodiments can also be combined, the steps can be implemented in any order, and there are many other changes such as the different aspects of one or more embodiments of the present application as described above, which are not provided in details for the sake of brevity.

[0135] One or more embodiments of the present application are intended to cover all such alternatives, modifications, and variations as fall within the broad scope of the present application. Accordingly, any one of the above-cited examples, or any other unrecited example, can be prepared without departing from the spirit and principles of one or more embodiments of the present application, and the present application is not limited to any one of the examples.

Claims

1. A digital non-contact AC voltage measurement method, characterized in that, A method is applied to a sensor comprising an open-type AC voltage probe and a signal acquisition module. The open-type AC voltage probe has symmetrically divided first and second electrode segments. The signal acquisition module integrates a main control unit and a communication unit. The method includes the following steps: The test wire is non-contactly housed inside the open-type AC voltage probe. Based on the principle of capacitive voltage division, the probe synchronously senses and collects the first and second electrode segments to generate a first voltage analog signal and a second voltage analog signal related to the voltage of the test wire. The main control unit converts the first and second analog voltage signals into first and second digital signals, and performs a summation operation on the first and second digital signals to obtain the main amplitude signal characterizing the voltage amplitude. The difference between the first digital signal and the second digital signal is obtained by performing a difference operation on the first digital signal and the second digital signal; The differential signal and the main amplitude signal are normalized to obtain the position offset factor; If the absolute value of the position offset factor is less than or equal to the preset effective installation threshold, the installation status of the open-type AC voltage probe is determined to be valid. The main amplitude signal and the position offset factor are used as inputs, and the compensated voltage measurement value is obtained by querying the two-dimensional correction model preset in the main control unit and calculating. The compensated voltage measurement value is output externally through the communication unit; The two-dimensional correction model is generated through the following steps: The actuator moves the wire under test inside the open-type AC voltage probe to multiple preset radial position points; At each radial position point, multiple standard voltage values ​​are applied to the conductor under test using a standard voltage source; At each calibration point consisting of a radial position point and a corresponding standard voltage value, a set of calibration main amplitude signals and calibration position offset factors are calculated. Establish a mapping relationship between the standard voltage value and the corresponding set of calibration main amplitude signals and calibration position offset factors; The mapping relationship is solidified into a two-dimensional correction model and preset in the main control unit.

2. The digital non-contact AC voltage measurement method according to claim 1, characterized in that, The method further includes the following steps: If the absolute value of the position offset factor is greater than the effective installation threshold, the installation status of the open-type AC voltage probe is determined to be invalid. Discard the main amplitude signal and the position offset factor calculated within the current acquisition period, and generate an alarm signal through the main control unit; The alarm signal is output to the outside through the communication unit.

3. The digital non-contact AC voltage measurement method according to claim 1, characterized in that, The step of taking the main amplitude signal and the position offset factor as inputs, and obtaining the compensated voltage measurement value by querying the two-dimensional correction model preset in the main control unit and calculating it includes the following steps: Using the main amplitude signal and the position offset factor as target coordinates, four adjacent reference grid points are located in the two-dimensional correction model preset in the main control unit; Read the pre-stored reference voltage values ​​from the four reference grid points; Based on the relative positional relationship between the target coordinates and the four reference grid points, a bilinear interpolation algorithm is used to perform weighted calculations on the four reference voltage values ​​to obtain the compensated voltage measurement value.

4. The digital non-contact AC voltage measurement method according to claim 1, characterized in that, The method further includes the following steps: The open-type AC voltage probe receives a self-calibration trigger command when no test lead is present. In response to the self-calibration trigger command, the system acquires the no-load signal generated by the first electrode segment and the second electrode segment, and converts it into a first baseline digital signal and a second baseline digital signal, respectively. The first baseline digital signal and the second baseline digital signal are stored as baseline bias values, which are used to calibrate the first digital signal and the second digital signal.

5. The digital non-contact AC voltage measurement method according to claim 1, characterized in that, The step of outputting the compensated voltage measurement value to the outside via the communication unit includes the following steps: Multiple compensated voltage measurements are acquired within a continuous measurement cycle; Store multiple compensated voltage measurements into a data buffer queue; A moving average digital filtering algorithm is applied to the data in the data buffer queue to generate the final filtered voltage measurement value. The final voltage measurement value is encapsulated into a data frame conforming to a predetermined communication protocol, and the data frame is sent to an external device through the communication unit.

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