Device and method for detecting live conductor in wall and judging phase sequence

Abstract

The invention discloses a device and a method for detecting an electrified conductor in a wall and judging a phase sequence, and the device comprises a plurality of independent test pens, and each test pen is provided with a magnetoresistive sensor, a signal processing circuit, a control unit and a wireless communication module; the magnetoresistive sensor is of a single-shaft structure, and the output end of the magnetoresistive sensor is connected with the signal processing circuit. The signal processing circuit comprises a differential amplifier and a band-pass filter, an input end of the signal processing circuit receives a magnetoresistive sensor signal, an output end of the signal processing circuit is connected with a control unit, and the control unit is configured to calculate a forward zero crossing timestamp of a current signal; the wireless communication module is used for time synchronization among a plurality of test pens, one test pen is used as a reference pen, and the wireless communication module initiates a time synchronization instruction and summarizes zero crossing point data of each pen; after the zero crossing point timestamps are compared, phase sequence identifiers are distributed according to a time ascending sequence.

Description

Technical Field

[0001] This application relates to the field of electrical testing technology, and in particular to an apparatus and method for detecting live conductors and determining phase sequence within a wall. Background Technology

[0002] Ensuring the safe operation of electrical circuits and preventing misoperation are fundamental and crucial requirements in power systems, building construction, and household electrical use. With the acceleration of urbanization and the increase in residential electricity density, electrical wiring layouts are becoming increasingly complex, with more and more lines hidden inside walls or enclosed structures. Accurately determining the presence of live conductors and the phase sequence of circuits without damaging the wall structure has become a technical challenge in electrical testing.

[0003] Traditional voltage testing tools, such as ordinary voltage testers, analog meters, and multimeters, typically use contact methods to detect voltage. While these tools can determine the presence of voltage, they pose a risk of electric shock during operation, especially when testing electrical equipment while it is running, which can easily lead to personal injury accidents. Furthermore, these tools cannot penetrate walls, pipes, or other obstacles, failing to meet the needs of testing concealed wiring. Non-contact voltage testers, as an improved voltage testing tool, operate based on the principle of electric field induction. They offer advantages such as simple structure, convenient operation, and high safety, and are widely used in power line inspections and household electrical testing. Users can sense the alternating electric field signal by bringing the pen tip close to the cable or switch under test, thus determining whether the line is energized. However, most existing non-contact voltage testers on the market have limited sensitivity. They can only determine whether the line is energized, not the phase sequence, making them unsuitable for the electrical testing needs of three-phase systems, especially in scenarios such as phase sequence identification, detection of incorrect phase wiring, and power circuit fault analysis.

[0004] Therefore, there is an urgent need to design a non-contact voltage tester with high sensitivity and phase sequence judgment capability, so as to provide a more intelligent, efficient and reliable detection method for electrical construction, power maintenance and household safe electricity use, and comprehensively improve the convenience and safety of electrical testing. Summary of the Invention

[0005] This application provides an apparatus and method for detecting live conductors and determining phase sequence within walls, in order to solve the aforementioned problems.

[0006] On one hand, this application provides a device for detecting and determining the phase sequence of live conductors within a wall. The device includes: several independent voltage testers, each of which is equipped with a magnetoresistive sensor, a signal processing circuit, a control unit, and a wireless communication module; the magnetoresistive sensor has a single-axis structure, and its output is connected to the signal processing circuit; the signal processing circuit includes a differential amplifier and a bandpass filter, its input receives the magnetoresistive sensor signal, and its output is connected to the control unit, which is configured to calculate the positive zero-crossing timestamp of the current signal; the wireless communication module is used for time synchronization among multiple voltage testers, with one voltage tester serving as a reference tester, initiating a time synchronization command through the wireless communication module and summarizing the zero-crossing data of each tester; after comparison, the zero-crossing timestamps are assigned phase sequence identifiers in ascending order of time.

[0007] In one implementation of this application, the magnetoresistive sensor is a differential output type magnetoresistive sensor, with its positive output terminal V+out and negative output terminal V-out respectively connected to the differential input terminal of the signal processing circuit.

[0008] In one implementation of this application, the signal processing circuit includes two processing units; wherein, the first stage is a differential amplifier circuit composed of an instrumentation amplifier, which receives the differential output of the magnetoresistive sensor, and the second stage is a bandpass filter circuit, the center frequency of which is matched with the power frequency current frequency, and the output terminal is connected to the control unit via an analog-to-digital converter.

[0009] In one implementation of this application, the control unit includes:

[0010] External analog-to-digital converter chip, supporting multi-channel synchronous sampling;

[0011] A microcontroller is configured to execute a zero-crossing detection algorithm, which includes: digitally filtering sampled current data; identifying the zero-crossing point of the current waveform from negative to positive; and calculating the precise zero-crossing time through interpolation.

[0012] In one implementation of this application, the wireless communication module adopts a master-slave architecture; wherein, the reference pen acts as the master node to broadcast a synchronization clock signal, the other slave nodes calibrate their local clocks and provide synchronization confirmation, and after synchronization is completed, the master node triggers all nodes to start current sampling simultaneously.

[0013] In one implementation of this application, each voltage tester is equipped with a four-color LED indicator group, corresponding to phase A, phase B, phase C and phase N respectively; in single-pen mode, the LED group cycles on and off in a preset order to indicate the energized state; in phase sequence judgment mode, the LED group of the reference pen is constantly lit according to the phase sequence judgment result, corresponding to the phase line indicator light.

[0014] This application also provides a method for detecting live conductors and determining phase sequence within a wall. The method includes: placing four voltage testers in the area of ​​the wall to be tested, designating one of them as a reference tester; the reference tester broadcasts a time synchronization command via wireless communication, while the other testers calibrate their local clocks; after synchronization is completed, the four testers simultaneously collect the current signals of each phase line; the control unit of each tester calculates the positive zero-crossing timestamp of the collected current; each tester sends its zero-crossing timestamp to the reference tester; the reference tester compares the order of all timestamps; wherein the order determination logic is as follows: the earliest timestamp corresponds to phase A, the latest timestamp corresponds to phase C, the remaining timestamps correspond to phase B, and the phase with the current amplitude continuously approaching zero is phase N.

[0015] In one implementation of this application, the execution of the time synchronization instruction includes:

[0016] The reference pen sends a synchronization instruction packet containing a precise start timestamp;

[0017] After receiving the instruction packet from the node pen, calculate the signal transmission delay and calibrate the local clock;

[0018] The node pen returns an acknowledgment packet with a time calibration mark;

[0019] After receiving all confirmation packets, the reference pen broadcasts a sampling start command.

[0020] In one implementation of this application, the calculation of the zero-crossing timestamp includes:

[0021] Digital bandpass filtering is applied to the sampled current data to extract the power frequency component; two consecutive sampling points in the current waveform are identified to satisfy the condition that the first point is less than or equal to zero and the second point is greater than zero.

[0022] The precise time of the zero-crossing point is calculated using linear interpolation between these two points;

[0023] A local timestamp aligned with the synchronous clock for marking zero crossings.

[0024] The device and method provided in this application for detecting and determining the phase sequence of charged conductors inside walls have the following advantages:

[0025] (1) A single-axis differential magnetoresistive sensor is used in combination with a signal processing circuit containing a differential amplifier and a bandpass filter to achieve non-contact detection of charged conductors inside the wall. This does not require damaging the wall structure and avoids the risk of electric shock from traditional contact tools. At the same time, it can capture weak magnetic field signals inside the wall, solving the problem that traditional tools cannot penetrate the wall to detect concealed wiring, and is suitable for complex wiring scenarios.

[0026] (2) By wirelessly synchronizing multiple voltage testers (the reference tester initiates synchronization as the master node), the control unit calculates the positive zero-crossing timestamp of the current. After the reference testers are summarized, they are assigned phase sequence identifiers according to "earliest phase A, latest phase C, middle phase B, and phase N with amplitude approaching zero". This makes up for the shortcomings of traditional non-contact voltage testers, which can only determine the current and cannot determine the phase sequence. It is suitable for three-phase system construction, maintenance and other scenarios.

[0027] (3) The wireless communication module adopts a master-slave architecture, with reference pen broadcast synchronization clock and slave node calibration feedback to ensure that multiple pens are sampled simultaneously; zero-crossing calculation combined with digital bandpass filtering (extracting power frequency components) and linear interpolation improves timestamp accuracy, avoids judgment deviations caused by synchronization errors and signal interference, and ensures the accuracy of phase sequence and live detection results.

[0028] (4) Each voltage tester is equipped with four-color LED lights corresponding to phases A / B / C / N. In single-pen mode, the lights cycle on and off to indicate the live status. In phase sequence mode, the reference pen is always lit to correspond to the phase line, eliminating the need for complicated reading operations. The device supports single-pen independent voltage testing and multi-pen collaborative phase sequence judgment, which is suitable for simple household live testing as well as professional testing needs of industrial three-phase systems. The user has a low learning curve. Attached Figure Description

[0029] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings:

[0030] Figure 1 A schematic diagram of a device for detecting and determining the phase sequence of a live conductor inside a wall, provided as an embodiment of this application;

[0031] Figure 2 This is a block diagram of the hardware structure of a single voltage tester provided in an embodiment of this application;

[0032] Figure 3 This is a block diagram of the internal structure of a uniaxial magnetoresistive sensor provided in an embodiment of this application;

[0033] Figure 4 This is a signal amplification circuit diagram provided for an embodiment of this application;

[0034] Figure 5 is a filter circuit diagram provided in an embodiment of this application;

[0035] Figure 6 The communication module circuit diagram provided in the embodiments of this application;

[0036] Figure 7 This is a schematic diagram used for execution phase sequence discrimination in the embodiments of this application. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below in conjunction with specific embodiments and corresponding drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0038] This application provides an apparatus and method for detecting live conductors and determining phase sequence within a wall. The technical solution proposed in this application will be described in detail below with reference to the accompanying drawings.

[0039] Figure 1 This diagram illustrates a device for detecting and determining the phase sequence of live conductors within a wall, as provided in an embodiment of this application. Figure 1 As shown, the device consists of four individual voltage testers, which can simultaneously measure the voltage of phases A, B, C, and N of a live conductor inside the wall and determine the phase sequence.

[0040] The internal structure of a single voltage tester is as follows: Figure 2 As shown, it mainly includes a sensing unit and peripheral circuits, a signal processing unit, a microcontroller core, and a communication unit.

[0041] Furthermore, to achieve non-contact voltage detection, the sensing unit uses a magnetoresistive sensor to detect the current in a charged conductor inside the wall. Given that wiring is typically buried 0–5 cm deep in the wall, the magnetic field generated by a single conductor directly above and outside the wall is approximately 10... -6 ~10 -8 T falls under the category of weak magnetic field detection. Therefore, this application selects a sensor with a sensitivity of up to 10. -9 The HMC1001 single-axis magnetoresistive sensor of T is used as the core of the sensing unit. Its internal structure is shown in [link to internal structure]. Figure 3 Its output terminals are V+out and V-out.

[0042] Furthermore, the signal processing unit includes a preamplifier circuit and a filter circuit. For example... Figure 4As shown, the amplifier circuit is built based on the AD620 differential amplifier to effectively amplify the weak signal output from the magnetoresistive sensor to a level range that can be processed by the subsequent processing unit. The AD620, with its advantages of high precision, low noise, high common-mode rejection ratio (CMRR), low linearity error, high input impedance, and ease of use, is particularly suitable for amplifying weak signals. Its gain is set by a single resistor connected between pins 1 and 8. Given that the system detects a 50Hz power frequency signal, a bandpass filter with a center frequency of 50Hz is configured in the subsequent stage for frequency selection. This signal processing design offers significant advantages: the high precision and low noise characteristics of the AD620 ensure that the weak magnetic field signal output from the magnetoresistive sensor is not distorted after amplification; the single-resistor gain setting simplifies circuit design and debugging; the 50Hz center-frequency bandpass filter accurately filters out noise, retaining only the target power frequency signal, providing a clean signal source for the subsequent control unit to accurately calculate the zero-crossing timestamp, effectively improving detection stability.

[0043] Furthermore, the hardware system detects the 50Hz power frequency signal, therefore a 50Hz bandpass filter is needed to extract the 50Hz signal. This filter adopts a Sallen-Key type second-order bandpass filter structure (circuit schematic shown). Figure 5a Simulation calculations were performed on a 50Hz bandpass filter, and its amplitude-frequency response is as follows: Figure 5b As shown, the center frequency is approximately 50Hz, and the circuit gain is 2. In practical applications, deviations in resistor and capacitor parameters may lead to an excessively high quality factor, resulting in excessive attenuation of the 50Hz signal. Therefore, the quality factor Q is set to 2.5 in the design. This filter design has significant advantages: the Sallen-Key second-order circuit is simple, highly stable, and easily integrated into the compact hardware of the voltage tester; the precise 50Hz center frequency and 2x gain can efficiently capture the target power frequency signal and match the subsequent processing level; the setting of Q=2.5 can avoid excessive signal attenuation caused by deviations in resistor and capacitor parameters, ensuring a pure output signal and laying a solid signal foundation for the control unit to accurately calculate the zero-crossing timestamp.

[0044] Furthermore, since the built-in ADC of the microcontroller could not meet the speed and accuracy requirements, an external high-resolution ADC chip was added. This chip provides 7 channels, 16-bit resolution input, and uses a single 5V power supply to reduce power consumption, with a sampling rate of up to 200kSPS per channel. Its ±5V analog input range allows it to support signal frequencies up to 22kHz, fully meeting the system requirements. The advantages of this external ADC chip are obvious: the 16-bit high resolution solves the problem of insufficient accuracy of the built-in ADC of the microcontroller, ensuring accurate sampling data of current signals; the high sampling rate of 200kSPS can fully capture the details of power frequency signals and avoid information loss; the 7-channel design reserves expansion space for simultaneous acquisition of multiple signals; the 5V single power supply meets the low power consumption requirements of the voltage tester; and the ±5V input range fully covers the system signal frequency band, providing reliable data support for subsequent accurate zero-crossing calculations.

[0045] Specifically, the core controller of the system uses the STM32F103C8T6 microcontroller, a series of chips known for its ultra-low power consumption, flexible operating modes, and excellent processing capabilities. The chip's ultra-low power consumption significantly extends the battery life of the voltage detector, perfectly suited for handheld and portable applications; its flexible operating modes allow switching between working and sleep states according to testing needs, further optimizing energy consumption. Its excellent processing capabilities efficiently perform digital filtering and zero-crossing interpolation calculations, and can also quickly respond to wireless synchronization commands, process multiple data interactions, and control LED indicators, providing a reliable core guarantee for the stable and smooth operation of conductor detection and phase sequence determination within the wall.

[0046] The data interaction and storage section consists of a wireless communication module and a storage unit. Considering factors such as low power consumption, a simple data format, and peripheral circuit design, the nRF24L01 chip was selected as the wireless transceiver core. This module operates in the 2.4GHz ISM band, supports transmission rates up to 2Mbps, and has extremely low power consumption. The specific circuit design of the wireless communication module is as follows... Figure 6 As shown, this module is precisely matched to system requirements: its low power consumption extends the battery life of the voltage detector, making it suitable for handheld and portable scenarios; the 2.4GHz ISM unlicensed frequency band requires no additional application, lowering the barrier to entry; the 2Mbps high transmission rate enables rapid transmission of zero-point timestamps, avoiding delays that could affect multi-transaction synchronization; and the simple peripheral circuit design facilitates the miniaturization of the voltage detector while ensuring stable communication, providing reliable data interaction support for multi-transaction collaborative detection and phase sequence determination.

[0047] Only one voltage tester is needed to perform the voltage testing function. When it is necessary to test the conductor for voltage, if the conductor is energized, the four LEDs A, B, C, and N on the voltage tester will light up and turn off in a scrolling manner.

[0048] Four voltage testers are required to perform phase sequence identification. All voltage testers must be turned on simultaneously. See the diagram below for usage instructions. Figure 7 As shown. The reference voltage tester will send a time synchronization request to the other voltage testers. After the time synchronization is completed, the four voltage testers will simultaneously collect the current on lines A, B, C, and N, and calculate the positive zero-crossing time of the current on each line.

[0049] The zero-crossing times will be summarized and sent to the reference test pen. The phase with the earliest zero-crossing time is phase A, followed by phase B, and then phase C. The phase with a current value of 0 is phase N.

[0050] The above is an embodiment of the present application providing a device for detecting and determining the phase sequence of a live conductor inside a wall. Based on the same inventive concept, the present application also provides a method for detecting and determining the phase sequence of a live conductor inside a wall, including: placing four voltage testers in the area of ​​the wall to be tested, designating one of them as a reference tester; the reference tester broadcasts a time synchronization command via wireless communication, and the other testers calibrate their local clocks; after synchronization is completed, the four testers simultaneously collect the current signals of each phase line; the control unit of each tester calculates the positive zero-crossing timestamp of the collected current; each tester sends the zero-crossing timestamp to the reference tester; the reference tester compares the order of all timestamps; wherein, the order determination logic is: the earliest timestamp corresponds to phase A, the latest timestamp corresponds to phase C, the remaining timestamps correspond to phase B, and the phase with the current amplitude continuously approaching zero is phase N.

[0051] Specifically, the execution of the time synchronization command includes: the reference pen sending a synchronization command packet containing a precise start timestamp; after receiving the command packet from the node pen, calculating the signal transmission delay and calibrating the local clock; the node pen returning an acknowledgment packet with a time calibration mark; and the reference pen broadcasting a sampling start command after receiving all acknowledgment packets.

[0052] Specifically, the calculation of the zero-crossing timestamp includes: performing digital bandpass filtering on the sampled current data to extract the power frequency component; identifying two consecutive sampling points in the current waveform that satisfy: the first point is less than or equal to zero and the second point is greater than zero; calculating the precise time of the zero-crossing point using linear interpolation between the two points; and marking the zero-crossing point with a local timestamp aligned with the synchronization clock.

[0053] This application provides a device and method for detecting live conductors and determining phase sequence within walls. It employs a single-axis differential magnetoresistive sensor combined with a signal processing circuit containing a differential amplifier and a bandpass filter to achieve non-contact detection of live conductors within walls. This eliminates the need to damage the wall structure and avoids the risk of electric shock associated with traditional contact tools. Simultaneously, it can capture weak magnetic field signals within the wall, solving the problem that traditional tools cannot penetrate walls to detect concealed wiring, making it suitable for complex wiring scenarios. Through wireless time synchronization of multiple voltage testers (with the reference tester initiating synchronization as the master node), the control unit calculates the positive zero-crossing timestamp of the current. After the reference testers aggregate the data, they assign phase sequence identifiers according to "earliest phase A, latest phase C, middle phase B, and phase N with amplitude approaching zero," overcoming the limitation of traditional non-contact voltage testers that can only detect live conductors but cannot determine phase sequence. This makes it suitable for three-phase system construction and maintenance scenarios. The wireless communication module adopts a master-slave architecture, with the reference pen broadcasting a synchronous clock and slave nodes providing calibration feedback to ensure simultaneous sampling of multiple pens. Zero-crossing calculation, combined with digital bandpass filtering (extracting power frequency components) and linear interpolation, improves timestamp accuracy, avoids judgment deviations caused by synchronization errors and signal interference, and ensures the accuracy of phase sequence and live-line detection results. Each voltage tester has four-color LEDs corresponding to phases A / B / C / N. In single-pen mode, the LEDs cycle on and off to indicate the live-line status, while in phase sequence mode, the reference pen remains constantly lit corresponding to the phase line, eliminating the need for complex reading operations. The device supports independent single-pen voltage testing and collaborative phase sequence determination of multiple pens, making it suitable for simple household live-line testing as well as meeting the professional testing needs of industrial three-phase systems, with a low learning curve for users.

[0054] The various embodiments in this application are described in a progressive manner. Similar or identical parts between embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. In particular, the device embodiments are basically similar to the method embodiments, so the description is relatively simple; relevant parts can be referred to the descriptions of the method embodiments.

[0055] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0056] The above description is merely an embodiment of this application and is not intended to limit the scope of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of the claims of this application.

Claims

1. A device for detecting and determining the phase sequence of charged conductors within a wall, characterized in that, The device includes: several independent voltage testers, each equipped with a magnetoresistive sensor, a signal processing circuit, a control unit, and a wireless communication module; the magnetoresistive sensor is a single-axis structure, with its output connected to the signal processing circuit; the signal processing circuit includes a differential amplifier and a bandpass filter, its input receiving the magnetoresistive sensor signal, and its output connected to the control unit, which is configured to calculate the positive zero-crossing timestamp of the current signal; the wireless communication module is used for time synchronization among the multiple voltage testers, with one voltage tester serving as a reference tester, initiating a time synchronization command through the wireless communication module and summarizing the zero-crossing data of each tester; after comparison, the zero-crossing timestamps are assigned phase sequence identifiers in ascending order of time.

2. The device for detecting and determining the phase sequence of charged conductors within a wall according to claim 1, characterized in that, The magnetoresistive sensor is a differential output type magnetoresistive sensor, with its positive output terminal V+out and negative output terminal V-out connected to the differential input terminal of the signal processing circuit, respectively.

3. The device for detecting and determining the phase sequence of charged conductors within a wall according to claim 1, characterized in that, The signal processing circuit includes two processing units; the first stage is a differential amplifier circuit composed of an instrumentation amplifier, which receives the differential output of the magnetoresistive sensor; the second stage is a bandpass filter circuit, whose center frequency matches the power frequency current frequency, and whose output is connected to the control unit via an analog-to-digital converter.

4. The device for detecting and determining the phase sequence of charged conductors within a wall according to claim 1, characterized in that, The control unit includes: External analog-to-digital converter chip, supporting multi-channel synchronous sampling; A microcontroller is configured to execute a zero-crossing detection algorithm, which includes: digitally filtering sampled current data; identifying the zero-crossing point of the current waveform from negative to positive; and calculating the precise zero-crossing time through interpolation.

5. The device for detecting and determining the phase sequence of live conductors within a wall according to claim 1, characterized in that, The wireless communication module adopts a master-slave architecture; wherein, the reference pen acts as the master node to broadcast a synchronization clock signal, and the other slave nodes calibrate their local clocks and provide feedback on synchronization confirmation. After synchronization is completed, the master node triggers all nodes to start current sampling simultaneously.

6. The device for detecting and determining the phase sequence of charged conductors within a wall according to claim 1, characterized in that, Each voltage tester is equipped with a four-color LED indicator group, corresponding to phase A, phase B, phase C and phase N respectively; in single-pen mode, the LED group lights up and turns off in a preset order to indicate the live state. In phase sequence judgment mode, the LED group of the reference pen will keep the corresponding phase line indicator light constantly lit according to the phase sequence judgment result.

7. A method for detecting and determining the phase sequence of live conductors within a wall, characterized in that, The method includes: placing four voltage testers in the area of ​​the wall to be tested, designating one of them as a reference tester; the reference tester broadcasts a time synchronization command via wireless communication, while the other testers calibrate their local clocks; after synchronization is completed, the four testers simultaneously collect the current signals of each phase line; the control unit of each tester calculates the positive zero-crossing timestamp of the collected current; each tester sends its zero-crossing timestamp to the reference tester; the reference tester compares the order of all timestamps; wherein the order determination logic is as follows: the earliest timestamp corresponds to phase A, the latest timestamp corresponds to phase C, the remaining timestamps correspond to phase B, and the phase with the current amplitude continuously approaching zero is phase N.

8. A method for detecting and determining the phase sequence of a live conductor within a wall, as described in claim 7, is characterized in that... The execution of the time synchronization instruction includes: The reference pen sends a synchronization instruction packet containing a precise start timestamp; After receiving the instruction packet from the node pen, calculate the signal transmission delay and calibrate the local clock; The node pen returns an acknowledgment packet with a time calibration mark; After receiving all confirmation packets, the reference pen broadcasts a sampling start command.

9. A method for detecting and determining the phase sequence of a live conductor within a wall, as described in claim 7, characterized in that... The calculation of the zero-crossing timestamp includes: Digital bandpass filtering is applied to the sampled current data to extract the power frequency component; two consecutive sampling points in the current waveform are identified to satisfy the condition that the first point is less than or equal to zero and the second point is greater than zero. The precise time of the zero-crossing point is calculated using linear interpolation between these two points; A local timestamp aligned with the synchronous clock for marking zero crossings.

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