Cathodic protection of pipelines and anticorrosion coating detection equipment and control method

Abstract

The application discloses a pipeline cathodic protection and anticorrosion layer detection equipment and a control method. The equipment comprises a general control unit, a direct current unit, an alternating current unit, an output switching unit and a data acquisition unit. The general control unit is provided with a microcontroller. The direct current unit is connected with the general control unit and is used for providing programmable direct current voltage or direct current output. The alternating current unit is connected with the general control unit and is used for providing programmable multi-frequency alternating current signal output. The output switching unit is connected between the direct current unit, the alternating current unit and the equipment output end and is controlled by the general control unit and is used for switching the output of the direct current unit or the alternating current unit to the equipment output end. The data acquisition unit is connected with the general control unit and is used for synchronously acquiring the voltage and current signals of the equipment output end. The direct current step direct current feeding and the alternating current multi-frequency sweep impedance test two functional modules are organically integrated in the same equipment, the full-flow detection automation is realized, and the quantitative evaluation and fault diagnosis on the anticorrosion layer state are facilitated.

Description

Technical Field

[0001] This invention relates to the field of pipeline inspection technology, and in particular to a pipeline cathodic protection and anti-corrosion layer inspection equipment and control method. Background Technology

[0002] Metal pipelines typically employ a combined protection method of external anti-corrosion coating and cathodic protection. The insulation performance of the anti-corrosion coating directly affects the effectiveness of cathodic protection and the service life of the pipeline. Currently, on-site inspection of the condition of pipeline anti-corrosion coatings mainly uses two methods: one is to assess the macroscopic condition of the anti-corrosion coating through cathodic protection parameter testing; the other is to analyze the microscopic characteristics of the anti-corrosion coating through AC impedance spectroscopy testing.

[0003] However, existing technologies have serious drawbacks. Field testing typically requires assembling multiple instruments to complete a complex testing process. For example, DC power supply testing requires a programmable DC power supply to provide a stepped current from zero to tens of amperes to measure the pipe-to-ground potential polarization curve; AC impedance testing requires a function generator to produce a sinusoidal signal, a power amplifier to provide sufficient drive capability, and an oscilloscope or lock-in amplifier to measure the voltage and current amplitude and phase difference. This split-type approach leads to the following prominent problems: 1. Low degree of process decentralization and automation: DC stepped DC feeders require operators to manually switch the current level step by step based on experience. After each switch, an uncertain period of time is required for the system to stabilize before data is manually recorded. This operating mode is highly subjective, and the test results obtained by different operators vary greatly. It is also impossible to guarantee that the complete test process will be completed within the standard time window. Moreover, there is a lack of objective criteria for current stability, and when to start recording data depends entirely on human experience, resulting in poor reproducibility of test data.

[0004] 2. Inconsistent Measurement Standards and Difficult Data Verification: In multi-frequency impedance measurement, frequency switching is accomplished by a function generator, voltage and current measurements are performed by an oscilloscope, and phase difference calculations may be done by a lock-in amplifier or post-processing software. These devices each have independent clock standards and triggering mechanisms, resulting in a lack of consistency in time and phase standards for measurements at different frequencies. When comparing and analyzing data measured at different time points, the lack of a unified timestamp and verification mechanism significantly reduces data verifiability. This is particularly problematic when performing simultaneous multi-point measurements on long-distance pipelines, where time synchronization of data at each point is virtually impossible.

[0005] 3. High System Complexity and Operator Specialization Requirements: Multiple instruments and equipment need to be carried on-site, resulting in numerous connecting cables and time-consuming and labor-intensive system setup. Operators need to be familiar with the operation of DC power supplies, signal sources, and measuring instruments, and also understand the basic principles of corrosion electrochemical testing. This complexity limits the widespread application of this technology and increases the risk of misoperation.

[0006] 4. Insufficient environmental adaptability and reliability: Laboratory instruments are typically designed for indoor environments with relatively good conditions, while pipeline testing sites are often in harsh environments with strong electromagnetic interference, temperature fluctuations, and humidity effects. Existing instruments and equipment may become unstable under such conditions, leading to decreased measurement accuracy or even damage. Summary of the Invention

[0007] This invention aims to solve at least one of the technical problems existing in the prior art. To this end, this invention proposes a pipeline cathodic protection and anti-corrosion coating detection device and control method, which organically integrates two major functional modules, DC stepped DC power supply and AC multi-frequency sweep impedance testing, into a single device. Through innovative device architecture and intelligent control logic, it achieves full-process automation from test preparation, signal output, data acquisition to result analysis, forming an integrated frequency response testing and data recording system, which facilitates quantitative evaluation and fault diagnosis of the anti-corrosion coating condition.

[0008] On one hand, embodiments of the present invention provide a pipeline cathodic protection and anti-corrosion coating detection device, comprising: The central control unit is equipped with a microcontroller, which is used to parse instructions, generate control signals, process data, and execute test procedures. A DC unit, connected to the main control unit, is used to provide programmable DC voltage or DC current output; An AC unit, connected to the main control unit, is used to provide programmable multi-frequency AC signal output; An output switching unit is connected between the DC unit, the AC unit and the device output terminal, and is controlled by the main control unit. It is used to switch the output of the DC unit or the AC unit to the device output terminal. A data acquisition unit, which is connected to the main control unit, is used to synchronously acquire voltage and current signals from the output of the device; The central control unit is configured with two execution modes: In the stepped DC power supply mode, the output switching unit is controlled to connect the DC unit to the device output terminal, and the DC unit is controlled to output current according to a preset stepped current sequence. At each current step, the output is judged to be stable based on the feedback from the data acquisition unit, and the data is recorded after it is stable. The multi-frequency sweep impedance mode controls the output switching unit to connect the AC unit to the device output terminal and controls the AC unit to output AC signals according to a preset frequency sequence; at each frequency point, voltage, current and phase difference data are collected synchronously.

[0009] According to some embodiments of the present invention, the DC unit is connected to the front-end power supply bus, and the main control unit controls the DC unit to output an adjustable DC voltage in multi-frequency sweep impedance mode, which serves as a bias power supply to power the front-end of the AC unit, so that the output signal of the AC unit is superimposed on the DC bias.

[0010] According to some embodiments of the present invention, the data acquisition unit includes an analog-to-digital converter (ADC) and a signal conditioning circuit. The signal conditioning circuit includes a pre-amplified programmable gain amplifier (PGA) and a hybrid filter architecture. The hybrid filter architecture includes at least two analog anti-aliasing filters connected in parallel and a digital filter implemented by the microcontroller. The master control unit automatically switches the path of the analog anti-aliasing filter and adjusts the parameters of the digital filter according to the frequency of the current output signal.

[0011] According to some embodiments of the present invention, the pipeline cathodic protection and anti-corrosion layer detection equipment further includes a communication unit, which includes a CAN bus interface. The central control unit receives an external synchronization trigger signal through the CAN bus interface or sends a synchronization trigger signal to other slave devices so that multiple devices start stepped DC power supply or frequency sweep impedance measurement under a unified clock. The central control unit is configured to execute a linkage analysis mode, controlling the equipment to perform a multi-frequency sweep impedance test at multiple different DC polarization potential points to obtain impedance spectrum data at different polarization potentials.

[0012] According to some embodiments of the present invention, the device output modes include DC constant current and constant voltage mode, DC constant current and variable voltage mode, DC constant voltage and variable current mode, AC constant frequency and constant voltage mode, AC constant frequency and variable voltage mode, and AC constant voltage and variable frequency mode; the device output direction is divided into rising and falling, rising refers to the output signal value gradually rising from low to high, and falling refers to the output signal value gradually falling from high to low.

[0013] On the other hand, embodiments of the present invention provide a control method for pipeline cathodic protection and anti-corrosion layer detection equipment, including: Select the execution mode and set the parameters accordingly; If the selected execution mode is stepped DC power supply mode, the control output switching unit connects the DC unit to the device output terminal and controls the DC unit to output current according to the preset stepped current sequence to perform stepped DC power supply control. If the selected execution mode is multi-frequency sweep impedance mode, the control output switching unit connects the AC unit to the device output terminal and controls the AC unit to output AC signals according to the preset frequency sequence to perform multi-frequency sweep impedance measurement.

[0014] According to some embodiments of the present invention, the step of performing stepped DC power supply control includes: The built-in stepped current sequence is invoked, which includes multiple target current values; Control the DC unit to output the first-stage target current value; The output voltage and current are monitored by the data acquisition unit, and the dynamic stability criteria are used to determine whether the voltage and current have reached stability. Once the voltage and current have stabilized, record the stable current value, voltage value, and timestamp. Continue outputting and recording the target current value for the next step until the last item in the step current sequence.

[0015] According to some embodiments of the present invention, the step of determining whether the voltage and current have reached stability based on the dynamic stability criterion includes: When determining whether each current step in the stepped DC feeding mode is stable, the volatility and trend derivative of the collected voltage or current data are calculated in real time. When the volatility is less than a first threshold and the derivative of the trend approaches zero and remains so for a first predetermined time, stability is determined to have been achieved.

[0016] According to some embodiments of the present invention, the step of performing multi-frequency sweep impedance measurement includes: Call the built-in frequency sequence; The control unit outputs an AC signal at the first frequency point; During the stabilization waiting period, intermittent pre-sampling is performed, and the stability of the pre-sampled data is used to intelligently determine whether the system has reached the state where it can be formally sampled. When the sampling state is reached, formal sampling is started, and voltage and current are synchronously collected and phase difference is calculated under a unified timestamp. The credibility of the data obtained from the formal sampling was assessed. Switch to the next frequency point according to the preset timing and sample and evaluate the reliability until the last frequency point of the frequency sequence.

[0017] According to some embodiments of the present invention, the credibility assessment of the data obtained from formal sampling includes: In the multi-frequency sweep impedance mode, for each frequency point, multiple intermittent pre-sampling is performed during the stabilization waiting period before formal sampling. Analyze the stability of the pre-sampled data and dynamically adjust the timing of the start of formal sampling based on the analysis results; After the formal sampling is completed, the variance or confidence interval of the multiple sampling data is calculated, and the reliability of the frequency point data is evaluated based on the calculation results. If the confidence level is lower than a predetermined threshold, automatic retesting or marking of frequency point data will be triggered.

[0018] The pipeline cathodic protection and anti-corrosion coating detection equipment and control method of the present invention have at least the following beneficial effects: The pipeline cathodic protection and anti-corrosion coating testing equipment provided by this invention includes a central control unit, a DC unit, an AC unit, an output switching unit, and a data acquisition unit. Through integrated stepped DC power supply and multi-frequency swept impedance functions, automated data acquisition and protection control, and an expandable human-machine interface and communication system, it improves testing efficiency, result accuracy, and system reliability, overcoming the shortcomings of existing multi-device splicing schemes in terms of consistency, repeatability, and safety. It completes unified acquisition and calculation of voltage, current, and phase, improving the repeatability and efficiency of power supply range testing; and forms an integrated frequency response testing and data recording system, facilitating quantitative evaluation and fault diagnosis of the anti-corrosion coating condition.

[0019] 1. Integration of testing functions and standardization of processes This equipment integrates two functions within a single system: stepped DC power supply and multi-frequency sweep impedance, enabling fully automated switching from DC power supply to multi-frequency AC excitation. Tasks that previously required multiple instruments can now be completed automatically with a single device, outputting a preset stepped current (0→10A, settling time ≤30s per step) and performing multi-frequency signal sweep (1Hz–100kHz). This integrated design simplifies the testing system and improves the automation and data consistency of experiments.

[0020] 2. Data acquisition is synchronized and results are verifiable. During frequency sweeping, voltage, current, and phase difference data are acquired in real time, and the impedance state (resistance, inductive reactance, and capacitive reactance components) of the tested object is automatically calculated on the computer according to the impedance calculation formula. All data are timestamped and verified. Compared with traditional split-type test equipment, the data acquisition synchronization is significantly improved, phase deviation and time drift are reduced, and the test results are traceable and verifiable.

[0021] 3. Enhanced reliability and security The equipment is internally designed with comprehensive overcurrent, overvoltage, short-circuit, and overtemperature protection circuits, and is equipped with a fan temperature control system to ensure stable operation under high current and long-term running conditions. This is particularly suitable for long-term field pipeline cathodic protection testing, improving system reliability and safety.

[0022] 4. Enhanced ease of operation and intelligent features It enables visual operation, allowing users to switch modes, set parameters, and monitor operating status directly on the screen. It also supports USB flash drive data storage and CAN bus communication, enabling multi-device connectivity and automated data archiving. This enhances the ease of use and scalability of the equipment, meeting the needs of both laboratory and field applications.

[0023] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0024] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which: Figure 1 This is a block diagram of the pipeline cathodic protection and anti-corrosion layer detection equipment according to an embodiment of the present invention; Figure 2 A circuit diagram of the stepped DC power supply mode for the pipeline cathodic protection and anti-corrosion coating detection equipment according to an embodiment of the present invention; Figure 3 This is a circuit diagram of the multi-frequency sweep impedance mode of the pipeline cathodic protection and anti-corrosion layer detection equipment according to an embodiment of the present invention; Figure 4 This is a flowchart of the control method for pipeline cathodic protection and anti-corrosion coating detection equipment according to an embodiment of the present invention; Figure 5 This is a flowchart of the stepped DC power supply control method for the pipeline cathodic protection and anti-corrosion coating detection equipment control method according to an embodiment of the present invention; Figure 6 This is a flowchart of the multi-frequency sweep impedance measurement process for the pipeline cathodic protection and anti-corrosion coating detection equipment control method according to an embodiment of the present invention; Figure 7 This is a schematic diagram of the current and voltage measured by the control method of the pipeline cathodic protection and anti-corrosion layer detection equipment in an embodiment of the present invention; Figure 8 This is a schematic diagram of the frequency and phase measured by the control method of the pipeline cathodic protection and anti-corrosion layer detection equipment in an embodiment of the present invention; Figure 9 This is a schematic diagram of the impedance measured by the control method of pipeline cathodic protection and anti-corrosion layer detection equipment in an embodiment of the present invention; Figure 10 This is a schematic diagram of the frequency and mode obtained by the control method of pipeline cathodic protection and anti-corrosion layer detection equipment in an embodiment of the present invention. Detailed Implementation

[0025] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0026] In the description of this invention, it should be understood that the orientation descriptions, such as up, down, front, back, left, right, etc., are based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention.

[0027] In the description of this invention, "several" means one or more, "multiple" means two or more, "greater than," "less than," "exceeding," etc. are understood to exclude the stated number, and "above," "below," "within," etc. are understood to include the stated number. If "first," "second," etc. are used in the description, they are only for the purpose of distinguishing technical features and should not be construed as indicating or implying relative importance or implicitly indicating the number of indicated technical features or the order of the indicated technical features.

[0028] In the description of this invention, unless otherwise explicitly defined, the terms "setting", "installing", "connecting" and "linking" should be interpreted broadly, and those skilled in the art can reasonably determine the specific meaning of the above terms in this invention in conjunction with the specific content of the technical solution.

[0029] Currently, some high-precision electrochemical workstations used in laboratories have AC impedance testing capabilities, and a few models even support combined DC polarization and AC impedance testing. However, their design goals differ fundamentally from the needs of pipeline field testing: electrochemical workstations are primarily designed for low-current (typically less than 1A), low-voltage (typically less than ±10V), and high-precision measurements within the laboratory, and cannot meet the high-current (e.g., 10A) and high-voltage (e.g., 0-60V) output requirements of pipeline testing. Furthermore, electrochemical workstations are expensive, typically costing hundreds of thousands of yuan or more, and are bulky and heavy, lacking protective design and portability considerations for outdoor environments.

[0030] Therefore, there is an urgent need in this field for an integrated device specifically designed for pipeline field testing that can organically integrate the two major functions of DC power supply and AC sweep frequency impedance testing. Through innovative hardware architecture and intelligent control algorithms, the complex testing process can be solidified into a standardized operating procedure that is automatically executed within the device, fundamentally solving the problems of low efficiency, poor consistency and complex operation of existing technologies.

[0031] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0032] Please see Figures 1 to 3This embodiment discloses a pipeline cathodic protection and anti-corrosion layer detection device provided by the present invention, including a main control unit 100, a DC unit 200, an AC unit 300, an output switching unit 400, and a data acquisition unit 500. The main control unit 100 is equipped with a microcontroller, which is used to parse instructions, generate control signals, process data, and execute test procedures. The DC unit 200 is connected to the main control unit 100 and is used to provide programmable DC voltage or DC current output. The AC unit 300 is connected to the main control unit 100 and is used to provide programmable multi-frequency AC signal output. The output switching unit 400 is connected between the DC unit 200, the AC unit 300, and the device output terminal, and is controlled by the main control unit 100, used to switch the output of the DC unit 200 or the AC unit 300 to the device output terminal. The data acquisition unit 500 is connected to the main control unit 100 and is used to synchronously acquire the voltage and current signals of the device output terminal.

[0033] The main control unit 100 has two execution modes: stepped DC power supply mode and multi-frequency sweep impedance mode. In stepped DC power supply mode, the main control unit 100 controls the output switching unit 400 to connect the DC unit 200 to the equipment output terminal and controls the DC unit 200 to output current according to a preset stepped current sequence. At each current step, the output stability is determined based on feedback from the data acquisition unit 500, and data is recorded after stability is achieved. In multi-frequency sweep impedance mode, the main control unit 100 controls the output switching unit 400 to connect the AC unit 300 to the equipment output terminal and controls the AC unit 300 to output AC signals according to a preset frequency sequence. At each frequency point, voltage, current, and phase difference data are simultaneously acquired.

[0034] The central control unit 100 is the brain of the entire device, employing a high-performance microcontroller, such as the STM32H743 series. This controller is based on the ARM Cortex-M7 core, with a maximum clock frequency of 480MHz, and features abundant on-chip peripherals and powerful computing capabilities. The central control unit 100 is responsible for coordinating the work of all functional modules within the device, including: parsing user commands, generating control signals, processing acquired data, executing test procedures, managing human-machine interaction, and handling communication protocols. Specifically, the central control unit 100 internally incorporates control algorithms that implement the core functions of this invention, including a stepped current control algorithm, a swept-frequency impedance test algorithm, a dynamic stability criterion algorithm, and a data reliability evaluation algorithm. The central control unit 100 is also used to control fan operation, display output, storage, and debugging functions.

[0035] The DC unit 200 is based on a synchronous buck-boost topology and provides a programmable DC output of 0-60V and 0-10A. It employs a dual-loop control strategy with an outer voltage loop and an inner current loop, allowing operation in both constant voltage (CV) and constant current (CC) modes. Low on-resistance MOSFETs are used as power switches to reduce conduction losses. The drive circuit utilizes a dedicated driver chip (such as TI's LM5118) to provide fast switching speeds and comprehensive protection functions. High-frequency, low-loss magnetic core materials are used for the inductors to reduce core losses and size.

[0036] The AC unit 300 offers two optional implementation paths to adapt to different application requirements. Path one is a switching implementation scheme, employing a full-bridge inverter circuit structure. A half-bridge driver (such as IR2110) drives four power MOSFETs to form an H-bridge. A sine wave signal is generated using sinusoidal pulse width modulation (SPWM) technology, and then filtered by an LC low-pass filter to remove high-frequency switching harmonics, resulting in a high-quality sine wave output. Path two is a linear implementation scheme, using a high-power operational amplifier (such as OPA544) to directly synthesize a sine wave signal. This scheme has the advantages of low output waveform distortion and low electromagnetic interference, but its efficiency is relatively low. The AC unit 300 has an output frequency range of 1Hz to 100kHz, an output voltage range of 0-±15V, and a total harmonic distortion (THD) of no more than 3%.

[0037] The output switching unit 400 is a key component for achieving functional integration in this invention. It consists of a high-current relay or a solid-state switch and is controlled by the main control unit 100, enabling flexible connection between the outputs of the DC unit 200 and the AC unit 300 and the device output terminals. In DC test mode, the switching matrix directly connects the DC unit 200 to the output terminal; in AC test mode, the switching matrix connects the AC unit 300 to the output terminal. More importantly, the switching matrix in this invention supports a special operating mode: during AC impedance testing, the output of the DC unit 200 can be simultaneously connected in series with the output of the AC unit 300 as a bias power supply, superimposing the AC test signal onto the DC polarization potential. This allows for the measurement of the impedance characteristics of the anti-corrosion layer under actual cathodic protection conditions, improving the engineering practicality of the test results.

[0038] The data acquisition unit 500 is responsible for accurately measuring the voltage and current response of the object under test. The core of this unit is a high-precision analog-to-digital converter (ADC), such as the ADS1256, a 24-bit Δ-Σ ADC with low noise and high resolution. The ADC pre-amplifier is equipped with signal conditioning circuitry, including a programmable gain amplifier (PGA), an anti-aliasing filter, and input protection circuitry. A hybrid filtering architecture is employed for signal conditioning: multiple analog filters with different cutoff frequencies (e.g., two channels, 10kHz and 100kHz) and software-implemented digital filters (e.g., FIR and IIR filters). The central control unit 100 automatically selects the optimal analog filter channel based on the current test frequency and dynamically adjusts the parameters of the digital filters to achieve the optimal signal-to-noise ratio across the entire frequency band (1Hz-100kHz).

[0039] Please see Figure 1 The DC unit 200 is connected to the front-end power supply bus. In the multi-frequency sweep impedance mode, the main control unit 100 controls the DC unit 200 to output an adjustable DC voltage as a bias power supply to power the front-end of the AC unit 300, so that the output signal of the AC unit 300 is superimposed on the DC bias.

[0040] Please see Figure 1 The data acquisition unit 500 includes a high-resolution analog-to-digital converter (ADC) and a signal conditioning circuit. The signal conditioning circuit includes a pre-amplified programmable gain amplifier (PGA) and a hybrid filter architecture. The hybrid filter architecture includes at least two parallel analog anti-aliasing filters and a digital filter implemented by a microcontroller. The main control unit 100 automatically switches the path of the analog anti-aliasing filter and adjusts the parameters of the digital filter according to the frequency of the current output signal.

[0041] In some embodiments of the present invention, when the central control unit 100 determines whether each current step of the stepped DC power supply mode is stable, it calculates the volatility and trend derivative of the collected voltage or current data in real time; when the volatility is less than a first threshold and the trend derivative approaches zero and remains so for a first predetermined time, it determines that stability has been achieved.

[0042] In some embodiments of the present invention, in multi-frequency sweep impedance mode, the control unit 100 performs multiple intermittent pre-samplings for each frequency point during the stabilization waiting period before formal sampling; analyzes the stability of the pre-sampling data and dynamically adjusts the timing of formal sampling based on the analysis results; after formal sampling is completed, calculates the variance or confidence interval of the multiple sampling data, and evaluates the reliability of the frequency point data based on the calculation results. If the reliability is lower than a predetermined threshold, it triggers automatic retesting or marks the frequency point data.

[0043] In some embodiments of the present invention, the central control unit 100 is configured to execute a linkage analysis mode, controlling the device to perform a multi-frequency sweep impedance test at multiple different DC polarization potential points to obtain impedance spectrum data at different polarization potentials.

[0044] In some embodiments of the present invention, the pipeline cathodic protection and anti-corrosion layer detection equipment further includes a communication unit 600, which includes a CAN bus interface. The central control unit 100 receives external synchronization trigger signals through the CAN bus interface or sends synchronization trigger signals to other slave devices so that multiple devices can start stepped DC power supply or sweep frequency impedance measurement under a unified clock.

[0045] The communication and storage module offers multiple data interfaces, including a USB host interface supporting direct storage from a USB flash drive, a USB device interface for communication with a host computer, an Ethernet interface, and a CAN bus interface. The CAN bus interface is particularly suitable for networking multiple devices for synchronous measurement over long distances. All test data is accurately timestamped and supports dual backup via local storage on a USB flash drive and remote transmission over a network.

[0046] It should be noted that the pipeline cathodic protection and anti-corrosion layer detection equipment also includes a power supply unit 700, a human-machine interface module, and a protection control unit. The power supply unit 700 includes a DC power supply module, a main control power supply module, an AC power supply module 1, and an AC power supply module 2. The power supply unit 700 is used to supply power to each functional module unit.

[0047] The human-machine interface unit includes a high-resolution LCD screen and a touchscreen, providing an intuitive graphical user interface. Users can select test modes, set parameters, start tests, monitor progress, and view results via the touchscreen. The device is also equipped with physical buttons and indicator lights as a supplement and backup to the touch operation.

[0048] The protection control unit provides comprehensive system protection functions, including overcurrent protection, overvoltage protection, short-circuit protection, and overtemperature protection. The protection circuit uses dedicated chips, such as the MAX4372 chip for current sensing and the TL431 chip for voltage reference, to achieve fast and accurate protection action. The cooling system uses temperature-controlled fans that automatically adjust fan speed based on the temperature of the power devices, ensuring effective heat dissipation while reducing noise and power consumption.

[0049] The output modes of this pipeline cathodic protection and anti-corrosion coating detection equipment include DC constant current and constant pressure mode, DC constant current and variable pressure mode, DC constant pressure and variable current mode, AC constant frequency and constant pressure mode, AC constant frequency and variable pressure mode, and AC constant pressure and variable frequency mode. The output direction is divided into rising and falling. Rising refers to the output signal value gradually increasing from low to high; falling refers to the output signal value gradually decreasing from high to low. The variation mode is divided into linear mode and exponential mode, with only the frequency exhibiting an exponential variation mode. Linear mode requires setting the step value, step time, and index range, while exponential mode only requires setting the frequency range and time.

[0050] DC constant current and constant voltage mode is a fixed voltage and current mode. The DC constant current transformer mode is a fixed current mode. You can set the minimum voltage value, the maximum voltage value, the output direction (rising, falling), the step value (how much to add each time), and the step time (how long to add the step value).

[0051] The DC constant voltage converter mode is a fixed voltage mode. You can set the minimum current value, the maximum current value, the output direction (rising, falling), the step value (how much to add each time), and the step time (how long to add the step value).

[0052] AC constant frequency and constant voltage mode is a fixed voltage frequency: The AC constant frequency transformer mode is a fixed frequency mode. You can set the minimum voltage value, the maximum voltage value, the output direction (rising, falling), the step value (how much to add each time), and the step time (how long to add the step value).

[0053] The AC constant voltage frequency conversion mode has a fixed voltage, minimum frequency, maximum frequency, output direction (rising, falling), step value (how much to add each time), and step time (how long to add the step value).

[0054] Please see Figure 2 The system utilizes the KUB6060 module to provide DC power output. Its core function is to provide a wide-range, high-power DC power supply to the tested pipeline, making it suitable for scenarios with high DC power requirements, such as pipeline corrosion layer inspection. The output voltage is continuously adjustable within the range of 0-60V, and the output current supports adjustment from 0-10A, allowing for precise matching of power supply parameters according to the testing process requirements. The start / stop and parameter adjustment of the DC power supply are achieved through PWM signal adjustment and MOSFET enable control. Combined with a dual closed-loop feedback mechanism for voltage and current, output parameter deviations are corrected in real time, ensuring stable DC voltage and current output during testing and preventing parameter fluctuations from affecting the accuracy of the test results.

[0055] (1) In terms of hardware structure, the DC unit 200 is based on synchronous Buck / Boost to realize CV / CC output of 0–60 V and 0–10 A; the current and voltage are sampled and conditioned by Hall and shunt, and then sent to the main control unit 100; overcurrent / overvoltage / short circuit, etc. are realized by dedicated devices such as MAX4372 and TL431; the fan is automatically speed regulated by temperature closed loop.

[0056] (2) Regarding software control, the following measures are taken: Sequence generation: Built-in standard sequence 0→0.5 A→…→10 A, where the step and upper / lower current gradient are configurable; Stability criterion: Set the stabilization time for each output stage to ≤30 s, and wait until the fluctuation / ripple threshold is met within the stabilization window before resuming data acquisition; Recording and verification: After each level stabilizes, the target value and measured mean / variance are automatically recorded, and a second retest or anomaly rollback can be triggered; Safety Interlock: If over-temperature, over-voltage, or over-current abnormalities occur, protection mechanisms will be triggered and reported. If the equipment triggers over-voltage (exceeding 120% of rated capacity), over-current (exceeding 110% of rated capacity), short circuit, over-temperature (exceeding 85℃), or reverse connection protection, a fault alarm will be displayed, and the equipment will automatically cut off the output. The cause of the fault will be investigated, such as abnormal load, incorrect wiring, or equipment overheating. After resolving the issue, the equipment will be restarted.

[0057] It can solidify "built-in sequence, stability criteria, recording / verification, and safety linkage" into the same device and the same time base, replacing manual step-by-step switching and external scripts, and significantly improving the repeatability and efficiency of power supply range tests.

[0058] Please see Figure 3 Leveraging the OPA544 high-power operational amplifier, this system provides AC power output, specifically designed for scenarios such as pipeline insulation performance testing. It offers adjustable AC voltage up to 15V and a current output capacity of up to 2A. AC power is polarity-insensitive, eliminating the need for additional wiring polarity distinctions and enhancing on-site operational convenience. The AC signal is generated via a DAC digital signal driver, coupled with real-time voltage and current acquisition and feedback, ensuring stable AC output waveforms and accurate parameters. It is adaptable to the AC power testing needs of oil and gas pipelines of different materials and diameters.

[0059] (1) In terms of hardware structure, the AC unit 300 adopts two implementation paths: full-bridge inverter (IR2110+MOSFET+LC filter) or linear high-power operational amplifier (such as OPA544), outputting 0-±15 V, 50 Hz, THD≤3%; voltage, current and phase difference are synchronously collected and transmitted back to the main control unit 100.

[0060] (2) The frequency sweeping process is as follows: Frequency list: 1 Hz → 10 Hz → 30 Hz → 50 Hz → 60 Hz → 100 Hz → 1 kHz → 10 kHz → 100 kHz; Switching and waiting: When switching to a frequency point, first stop the previous frequency point, wait 10 seconds, start the new frequency point, and wait 5 minutes for it to stabilize; Data Acquisition and Verification: After stabilization, acquire 10 sets (1 s interval) of voltage / current / phase and timestamp; frequency accuracy can be checked with an oscilloscope; shutdown sequence: first reduce voltage, then stop frequency, direct power off is prohibited; timestamps and data records throughout the process are backed up to the cloud / locally.

[0061] It can solidify frequency switching, stabilization waiting, unified sampling, and phase calculation into a collaborative SOP for equipment / host computer, forming a consistent frequency and time reference, a unified data structure, and a shutdown sequence, solving the problems of process dispersion and verification difficulties caused by multiple machines. Built-in step sequence + steady-state criteria + automatic recording / verification form a replicable "0→10 A" standard process, avoiding the uncertainties of manual switching and external scripts, and ensuring reproducible step power supply. A unified frequency list, waiting / acquisition / verification SOPs, and standardized shutdown ensure consistent frequency and time reference, verifiable phase acquisition, and traceable data, achieving integrated frequency sweep testing.

[0062] Please see Figure 4 This embodiment also provides a control method for pipeline cathodic protection and anti-corrosion layer detection equipment, applied to the aforementioned pipeline cathodic protection and anti-corrosion layer detection equipment. This control method includes stepped DC power supply control and multi-frequency sweep impedance measurement. The stepped DC power supply control involves the main control unit 100 controlling the output switching unit 400 to connect the DC unit 200 to the equipment output terminal, and controlling the DC unit 200 to output current according to a preset stepped current sequence. The multi-frequency sweep impedance measurement involves the main control unit 100 controlling the output switching unit 400 to connect the AC unit 300 to the equipment output terminal, and controlling the AC unit 300 to output AC signals according to a preset frequency sequence. Specifically, this includes, but is not limited to, the following steps: S100. Select the execution mode and set the parameters according to the selected execution mode; S200. If the selected execution mode is stepped DC power supply mode, the control output switching unit connects the DC unit to the device output terminal and controls the DC unit to output current according to the preset stepped current sequence to perform stepped DC power supply control. S300. If the selected execution mode is multi-frequency sweep impedance mode, the control output switching unit connects the AC unit to the device output terminal and controls the AC unit to output AC signals according to the preset frequency sequence to perform multi-frequency sweep impedance measurement.

[0063] Please see Figure 5The stepped DC power supply control in step S200 above includes: S201. Call the built-in stepped current sequence, which includes multiple target current values; S202, Control the DC unit 200 to output the first-step current target value; S203. The output voltage and current are monitored by the data acquisition unit 500, and it is determined whether stability has been achieved based on the dynamic stability criterion. S204. Once the system reaches a stable state, record the stable current value, voltage value, and timestamp. S205. Determine whether it is the last item in the stepped current sequence. If not, control the DC unit 200 to output the target current value of the next step and return to step S103; if yes, execute the closing process.

[0064] The stepped DC power supply control function is specifically designed for pipeline cathodic protection parameter testing, used to automatically execute standard stepped current polarization tests. The equipment has a pre-defined standard current step sequence (e.g., 0→0.5A→1.0A→...→10A), and users can also customize the sequence parameters. The innovation of this function lies in the introduction of a dynamic stability criterion algorithm, replacing the traditional fixed-time waiting method. The specific algorithm flow is as follows: When the system outputs a certain stepped current, the data acquisition unit 500 continuously monitors the output voltage and current at a high sampling rate (e.g., 1kSPS). Two key parameters are calculated in real time: the standard deviation of short-term (e.g., the most recent second) data (reflecting the magnitude of fluctuation) and the first derivative of the data (reflecting the trend of change). The system presets two thresholds: a fluctuation threshold (e.g., 0.5% of full scale) and a rate of change threshold (close to zero). The system determines that it has reached a stable state when the following conditions are met simultaneously: first, the standard deviation for multiple consecutive calculation cycles (e.g., 3 cycles) is less than the fluctuation threshold; second, the first derivative of the data remains close to zero for a certain period of time. Once the stability condition is met, regardless of how much time has passed since the start of that step (even if it's much less than the preset maximum waiting time, such as 30 seconds), the current data is immediately recorded and the process moves to the next step. Conversely, if the system is still unstable after the maximum waiting time, potentially unreliable data is not mechanically recorded. Instead, an anomaly handling process is initiated: such as slightly adjusting the current value and retrying, or recording the abnormal state and prompting user intervention. This intelligent criterion algorithm significantly improves testing efficiency, avoids unnecessary waiting when the system is stable, and prevents the recording of invalid data when the system is unstable.

[0065] Please see Figure 6 The multi-frequency sweep impedance measurement in step S300 above includes: S301, Receive user commands or invoke built-in frequency sequences; S302, Control AC unit 300 outputs AC signal at the first frequency point; S303. During the stable waiting period, perform intermittent pre-sampling and intelligently determine whether the system has reached the state where it can be formally sampled based on the stability of the pre-sampled data. S304. When the state of formal sampling is reached, formal sampling is started, and voltage and current are synchronously collected and phase difference is calculated under a unified timestamp. S305. Conduct a credibility assessment on the data obtained from formal sampling; S306. Determine whether it is the last frequency point of the frequency sequence. If not, switch to the next frequency point according to the preset timing and return to step S203. If yes, control the AC unit 300 to stop output according to the preset shutdown sequence.

[0066] The multi-frequency sweep impedance measurement function is used to automatically measure the impedance characteristics of pipeline corrosion protection coatings at different frequencies and generate impedance spectra (such as Bode plots or Nyquist plots). The device has built-in standard frequency sequences (such as 1Hz, 10Hz, 30Hz, 50Hz, 60Hz, 100Hz, 1kHz, 10kHz, 100kHz), and users can also customize sequences. It employs an intelligent intermittent sampling and data reliability assessment mechanism: when the system switches to a new test frequency, it does not immediately begin formal sampling, but first enters a stabilization waiting period. During this period, low-frequency intermittent pre-sampling is performed (such as collecting one set of data per minute). By analyzing the stability and consistency of the pre-sampled data, it intelligently determines whether a truly stable state has been reached. Once the system is confirmed to be stable through pre-sampling, formal sampling is immediately initiated. During the formal sampling phase, voltage and current signals are acquired synchronously, and the fundamental component is extracted using Fast Fourier Transform (FFT) or least squares algorithms to calculate the impedance magnitude and phase difference. After sampling is completed, statistical analysis is performed on all sampled data at that frequency point to calculate variance, standard deviation, and confidence interval, and to quantitatively evaluate data quality. If the evaluation result does not reach the preset confidence threshold (e.g., 95% confidence), the frequency point will be automatically retested, or a quality marker will be added to the data file. Throughout the frequency sweep process, all frequency point measurements are performed under a unified high-precision clock reference to ensure the consistency of timestamps and the accuracy of phase measurements.

[0067] It should be noted that the pipeline cathodic protection and anti-corrosion layer detection equipment and control method provided in this embodiment also support the following working modes: Linked analysis mode: At different DC polarization potential points (such as -0.85V, -1.0V, -1.2V relative to the Cu / CuSO4 reference electrode), an AC impedance frequency sweep test is automatically performed to obtain a set of three-dimensional "potential-frequency-impedance" datasets. Through this linked test, the influence of polarization potential on the impedance characteristics of the anti-corrosion coating can be studied in depth, providing richer evidence for the condition assessment of the anti-corrosion coating.

[0068] Multi-device network synchronous measurement mode: Multiple testing devices are networked via CAN bus or Ethernet, with one device acting as the master and the others as slaves. The master sends a global synchronization trigger signal, and all devices begin measurement simultaneously under the unified GPS clock or high-precision crystal oscillator synchronization. This mode is particularly suitable for surveying the corrosion protection layer of long-distance pipelines, and can accurately locate the location of corrosion protection layer defects.

[0069] Adaptive test mode: Intelligently adjusts subsequent test parameters based on preliminary test results. For example, in frequency sweep impedance testing, if drastic impedance changes are found in certain frequency bands, the test point density is automatically increased in these bands to obtain more refined impedance characteristics.

[0070] This pipeline cathodic protection and anti-corrosion coating testing equipment can convert 220V AC power into DC or AC outputs of different specifications, providing a stable and reliable power supply for various loads, and possessing a variety of convenient control, monitoring, and communication functions. The programmable DC output function supports voltage and current modes, adapting to scenarios requiring precise programmable DC output and multi-dimensional parameter acquisition. Programmable adjustment is achieved based on an output curve control strategy; the voltage mode output range is 0-60V, and the current mode output range is 0-10A. Control attributes include starting voltage, ending voltage, amplitude of change, and period of change; acquired parameters include current voltage, current current, and DC / AC components of voltage and current. The AC output features impedance analysis and frequency conversion impedance acquisition functions, adapting to load impedance characteristic testing scenarios. Impedance analysis is achieved based on frequency conversion impedance acquisition, supporting programmable adjustment; control attributes include starting frequency, ending frequency, amplitude of change, and period of change; acquired parameters include real-time output voltage data and real-time output current data, combined with data to calculate impedance characteristics.

[0071] Example 1: Equipment Configuration and Testing Process The testing equipment features a portable chassis made of metal, offering excellent electromagnetic shielding and heat dissipation, and is easy to carry in the field. The internal design is modular, with each functional module connected via an internal bus. For example, the main control unit 100 uses an STM32H743VIT6 microcontroller, equipped with 1MB Flash memory and 512KB RAM, and an external 25MHz crystal oscillator. The DC unit 200 uses an LM5118 controller to construct a synchronous buck-boost circuit, employing an IRF3205 (55V / 110A) power switch and a 20μH / 20A output filter inductor. The AC unit 300 uses a full-bridge inverter, with an IR2110S driver, an IRF540 (100V / 33A) power transistor, and an output LC filter with parameters L=100μH / 10A and C=10μF / 100V. The data acquisition unit 500 is based on the ADS1256, with a maximum sampling rate of 30kSPS and a built-in PGA (programmable gain of 1, 2, 4, 8, 16, 32, and 64 times).

[0072] After the testing equipment is powered on, the main control unit 100 first performs a self-test, including memory testing, ADC calibration, and power supply voltage monitoring. After passing the self-test, it enters standby mode and displays the main operation interface.

[0073] (1) After selecting the stepped DC power supply mode, set the parameters; select the built-in standard sequence (0→10A, step size 0.5A) or a custom sequence. After setting, click the start button to begin the automatic execution of the test process: The main control unit 100 controls the output switching unit 400 to connect the DC unit to the equipment output terminal.

[0074] Output the first step current (0.5A) and start the dynamic stability criterion algorithm.

[0075] The data acquisition unit 500 synchronously samples the output voltage and current at a rate of 1 kSPS. It calculates the standard deviation and rate of change derivative of the data within the most recent second in real time.

[0076] The system is considered stable when the standard deviation is less than 0.5% of full scale and the rate of change is close to zero for 3 consecutive seconds. Record the stable current value, voltage value, timestamp, and fluctuation range.

[0077] Determine if this is the last step; if not, output the current for the next step and repeat the process.

[0078] After the test is completed, a test report is automatically generated, including a data table and a polarization curve; it can be saved to a USB flash drive or transferred to a host computer via a USB interface.

[0079] (2) After selecting the multi-frequency sweep impedance mode, set the frequency; select a standard frequency sequence or a custom sequence. After starting the test, perform the following steps: The main control unit 100 first controls the DC unit 200 to output an adjustable DC bias voltage (such as -1.2V) to simulate the cathodic protection potential of the pipeline.

[0080] The control output switching unit 400 connects the AC unit and simultaneously connects the DC bias in series.

[0081] Switch to the first frequency point (1Hz) in sequence and output a sine wave signal of the corresponding frequency.

[0082] Entering a stable waiting period, during which pre-sampling is performed once per minute, collecting 10 cycles of data.

[0083] When the deviation between the effective voltage values ​​of two consecutive pre-sampled samples is less than 1%, the system is considered stable and formal sampling is initiated.

[0084] Please see Figure 7 Voltage and current signals were synchronously acquired at a rate of 10 kSPS for 60 seconds, with a total of 600,000 points collected.

[0085] Please see Figure 8 , Figure 9 and Figure 10 The collected data is analyzed by FFT to calculate the fundamental amplitude and phase difference, and the impedance magnitude and phase are obtained.

[0086] Statistical analysis was performed on 10 sets of sampling results at this frequency point to calculate the 95% confidence interval.

[0087] If the confidence interval meets the requirements, store the data and switch to the next frequency point; otherwise, retest or mark.

[0088] After the test is completed, the system automatically plots the impedance Bode plot (amplitude and phase frequency characteristics) and calculates the parameters of the equivalent circuit model.

[0089] Example 2: Application of Linkage Analysis Mode Based on Example 1, a linked analysis mode was initiated to conduct an in-depth study of the impedance characteristics of the pipeline anti-corrosion coating under different polarization states. The test procedure is as follows: The device first controls the DC unit to output a polarization potential of -0.85V (relative to the Cu / CuSO4 reference electrode).

[0090] At this potential, perform an AC impedance sweep test from 1Hz to 1kHz (frequency point density can be set).

[0091] After completing the frequency sweep, switch the DC polarization potential to -1.0V, and repeat the AC impedance frequency sweep after it stabilizes.

[0092] Switch the polarization potential back to -1.2V and repeat the AC impedance frequency sweep.

[0093] It automatically integrates impedance data from three different potentials to create a three-dimensional impedance spectrum, such as Nyquist plots at different potentials.

[0094] By analyzing the variation of impedance spectrum with polarization potential, we can assess the integrity, moisture content, aging degree, and other state parameters of the anti-corrosion coating, providing a more in-depth basis for anti-corrosion coating maintenance decisions.

[0095] Example 3: Multi-device network synchronous measurement application In a 100-kilometer long-distance pipeline inspection project, three inspection devices were networked together for synchronous measurement. The devices were connected via a CAN bus, with a maximum distance of 1 kilometer, which could be extended using CAN repeaters. One device served as the master, and the other two as slaves. The master device acquired precise pulse-per-second (PPS) signals via a GPS module and transmitted time synchronization information to each slave device via the CAN bus.

[0096] The testing process is as follows: Each testing device is connected to three test points on the pipeline (e.g., points A, B, and C), with a distance of approximately 1 kilometer between them.

[0097] The host sends a synchronization trigger command, and all devices simultaneously begin AC impedance frequency sweep testing upon receiving the next GPS second pulse signal.

[0098] After each testing device completes its test independently, it transmits the data to the host computer via the CAN bus.

[0099] By integrating the data from the three test points, a curve showing the change in impedance value with the location of the pipe was plotted.

[0100] Test results showed that the impedance modulus at point B was significantly lower than that at points A and C, approximately 50% of that at points A and C, thus pinpointing the location of damage or defects in the anti-corrosion layer at point B. Maintenance personnel then excavated and inspected point B, confirming damage to the anti-corrosion layer, and promptly repaired it.

[0101] Example 4: Application of Adaptive Testing Mode Building upon Example 1, an adaptive test mode is activated for precise measurements of key frequency bands. First, a rapid frequency sweep (with a limited number of frequency points, such as 1Hz, 10Hz, 100Hz, 1kHz, and 10kHz) is performed to identify characteristic frequency bands with drastic impedance changes based on preliminary results. Then, the test point density is automatically increased within these characteristic frequency bands for a more refined frequency sweep. For example, if a drastic change in impedance phase is detected in the 100Hz-1kHz frequency band, 10 test points are automatically added at logarithmic intervals within that band (e.g., 126Hz, 158Hz, 200Hz, 251Hz, 316Hz, 398Hz, 501Hz, 631Hz, and 794Hz) to obtain more detailed impedance characteristics. This adaptive test strategy ensures testing efficiency while obtaining high-resolution impedance data for critical frequency bands.

[0102] The embodiments of the present invention have the following significant beneficial effects: 1. High Integration and Standardized Processes: Functions that previously required multiple expensive instruments are now highly integrated into a single portable device, significantly reducing system complexity and cost. More importantly, testing processes that relied on human experience are formalized into standardized operating procedures that are automatically executed within the device, lowering the technical requirements for operators and ensuring consistency in the testing process and reliability of the results.

[0103] 2. High Data Consistency and Verifiability: A unified hardware clock and control core ensure that all measurement data during DC power supply and AC frequency sweep have a consistent time and frequency reference, fundamentally eliminating system errors caused by the assembly of multiple devices. All data is accurately timestamped and its integrity is guaranteed through a verification mechanism, ensuring complete traceability and verifiability of the test results.

[0104] 3. Intelligent Adaptability and High Reliability: Innovative dynamic stability criteria, intelligent sampling mechanisms, and data reliability assessment algorithms enable the equipment to make intelligent decisions and adapt, significantly improving testing efficiency and data quality. A hybrid filtering architecture, multiple protection circuits, and a temperature control system specifically designed for field environments ensure long-term stable operation of the equipment under harsh conditions.

[0105] 4. Powerful Functions and Excellent Expandability: The equipment not only possesses basic DC power supply and AC frequency sweep functions, but also supports advanced functions such as DC bias AC measurement, linkage analysis, and multi-unit network synchronous measurement, meeting multi-level needs from routine testing to in-depth diagnostics. Abundant communication interfaces and storage options facilitate integration into larger monitoring systems.

[0106] 5. Significant Economic Benefits: The price of a single testing device is far lower than that of a split-type testing system, and it significantly reduces the number of personnel and time costs required for on-site testing, resulting in significant economic benefits. The portability and ease of use of the equipment enable its wider application and are of great value in improving pipeline safety management.

[0107] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A device for detecting cathodic protection and anti-corrosion coatings in pipelines, characterized in that, include: A central control unit (100) is provided with a microcontroller, which is used to parse instructions, generate control signals, process data and execute test procedures; A DC unit (200) is connected to the main control unit (100) and is used to provide programmable DC voltage or DC current output; An AC unit (300) is connected to the main control unit (100) and is used to provide programmable multi-frequency AC signal output; An output switching unit (400) is connected between the DC unit (200), the AC unit (300) and the device output terminal, and is controlled by the main control unit (100) to switch the output of the DC unit (200) or the AC unit (300) to the device output terminal. A data acquisition unit (500) is connected to the main control unit (100) and is used to synchronously acquire voltage and current signals at the output of the device; The main control unit (100) is configured with two execution modes: In the stepped DC power supply mode, the output switching unit (400) is controlled to connect the DC unit (200) to the output terminal of the device, and the DC unit (200) is controlled to output current according to a preset stepped current sequence; at each current step, the output is judged to be stable based on the feedback from the data acquisition unit (500), and the data is recorded after it is stable. In the multi-frequency sweep impedance mode, the output switching unit (400) is controlled to connect the AC unit (300) to the device output terminal, and the AC unit (300) is controlled to output AC signals according to a preset frequency sequence; at each frequency point, voltage, current and phase difference data are collected synchronously.

2. The pipeline cathodic protection and anti-corrosion coating detection equipment according to claim 1, characterized in that, The DC unit (200) is connected to the front-end power supply bus. In the multi-frequency sweep impedance mode, the main control unit (100) controls the DC unit (200) to output an adjustable DC voltage as a bias power supply to power the front-end of the AC unit (300), so that the output signal of the AC unit (300) is superimposed on the DC bias.

3. The pipeline cathodic protection and anti-corrosion coating detection equipment according to claim 1, characterized in that, The data acquisition unit (500) includes an analog-to-digital converter (ADC) and a signal conditioning circuit. The signal conditioning circuit includes a pre-amplified programmable gain amplifier (PGA) and a hybrid filter architecture. The hybrid filter architecture includes at least two analog anti-aliasing filters connected in parallel and a digital filter implemented by the microcontroller. The master control unit (100) automatically switches the path of the analog anti-aliasing filter and adjusts the parameters of the digital filter according to the frequency of the current output signal.

4. The pipeline cathodic protection and anti-corrosion coating detection equipment according to claim 1, characterized in that, The pipeline cathodic protection and anti-corrosion layer detection equipment also includes a communication unit (600), which includes a CAN bus interface. The main control unit (100) receives external synchronization trigger signals through the CAN bus interface or sends synchronization trigger signals to other slave devices so that multiple devices can start stepped DC power supply or sweep frequency impedance measurement under a unified clock. The main control unit (100) is configured to execute a linkage analysis mode, controlling the equipment to perform a multi-frequency sweep frequency impedance test at multiple different DC polarization potential points to obtain impedance spectrum data at different polarization potentials.

5. The pipeline cathodic protection and anti-corrosion coating detection equipment according to claim 1, characterized in that, The equipment output modes include DC constant current and constant voltage mode, DC constant current and variable voltage mode, DC constant voltage and variable current mode, AC constant frequency and constant voltage mode, AC constant frequency and variable voltage mode, and AC constant voltage and variable frequency mode. The output direction of the equipment is divided into rising and falling. Rising means that the output signal value gradually increases from low to high, and falling means that the output signal value gradually decreases from high to low.

6. A control method for pipeline cathodic protection and anti-corrosion coating detection equipment, characterized in that, The control method, applied to the pipeline cathodic protection and anti-corrosion coating detection equipment as described in any one of claims 1 to 5, includes: Select the execution mode and set the parameters accordingly; If the selected execution mode is stepped DC power supply mode, the control output switching unit (400) connects the DC unit (200) to the device output terminal and controls the DC unit (200) to output current according to the preset stepped current sequence to perform stepped DC power supply control. If the selected execution mode is multi-frequency sweep impedance mode, the control output switching unit (400) connects the AC unit (300) to the device output terminal and controls the AC unit (300) to output AC signals according to the preset frequency sequence to perform multi-frequency sweep impedance measurement.

7. The control method for pipeline cathodic protection and anti-corrosion layer detection equipment according to claim 6, characterized in that, The steps for performing stepped DC power supply control include: The built-in stepped current sequence is invoked, which includes multiple target current values; The DC control unit (200) outputs the first-step target current value; The output voltage and current are monitored by the data acquisition unit (500), and it is determined whether the voltage and current have reached stability based on the dynamic stability criterion. Once the voltage and current have stabilized, record the stable current value, voltage value, and timestamp. Continue outputting and recording the target current value for the next step until the last item in the step current sequence.

8. The control method for pipeline cathodic protection and anti-corrosion coating detection equipment according to claim 7, characterized in that, The determination of whether voltage and current have reached stability based on dynamic stability criteria includes: When determining whether each current step in the stepped DC feeding mode is stable, the volatility and trend derivative of the collected voltage or current data are calculated in real time. When the volatility is less than a first threshold and the derivative of the trend approaches zero and remains so for a first predetermined time, stability is determined to have been achieved.

9. The control method for pipeline cathodic protection and anti-corrosion coating detection equipment according to claim 8, characterized in that, The steps for performing multi-frequency sweep impedance measurement include: Call the built-in frequency sequence; The control unit (300) outputs an AC signal at the first frequency point; During the stabilization waiting period, intermittent pre-sampling is performed, and the stability of the pre-sampled data is used to intelligently determine whether the system has reached the state where it can be formally sampled. When the sampling state is reached, formal sampling is started, and voltage and current are synchronously collected and phase difference is calculated under a unified timestamp. The credibility of the data obtained from the formal sampling was assessed. Switch to the next frequency point according to the preset timing and sample and evaluate the reliability until the last frequency point of the frequency sequence.

10. The pipeline cathodic protection and anti-corrosion coating detection equipment according to claim 9, characterized in that, The credibility assessment of the data obtained from formal sampling includes: In the multi-frequency sweep impedance mode, for each frequency point, multiple intermittent pre-sampling is performed during the stabilization waiting period before formal sampling. Analyze the stability of the pre-sampled data and dynamically adjust the timing of the start of formal sampling based on the analysis results; After the formal sampling is completed, the variance or confidence interval of the multiple sampling data is calculated, and the reliability of the frequency point data is evaluated based on the calculation results. If the confidence level is lower than a predetermined threshold, automatic retesting or marking of frequency point data will be triggered.

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