Test method and system for observing time domain waveform and frequency domain waveform

Abstract

The invention relates to the technical field of power supply characteristic tests, and aims to provide a test method and system for observing a time domain waveform and a frequency domain waveform, and the method comprises the following steps: configuring synchronization parameters between a signal source and an oscilloscope; calling a control command to obtain a group of time domain data on the signal source and the oscilloscope to obtain a time domain waveform; converting the time domain waveform into a frequency domain waveform by using an FFTW library; and transmitting the time domain waveform and the frequency domain waveform to a display interface for display. And converting the time-domain waveform into a frequency-domain waveform by using an FFTW library, transmitting the time-domain waveform and the frequency-domain waveform to a display interface for display, and providing the time-domain waveform and the frequency-domain waveform for a user to observe and record. A user can simultaneously see the time-domain waveform and the frequency-domain waveform on the same display interface, so that the time-domain waveform and the frequency-domain waveform can be conveniently and intuitively compared and analyzed.

Description

Technical Field

[0001] The present invention relates to the technical field of power supply characteristic tests, and particularly relates to a test method and system for observing time-domain waveforms and frequency-domain waveforms. Background Art

[0002] The GJB181 "Aircraft Power Supply Characteristics" series of standards is the leading and interface standard for coordinating aircraft power supply systems and electrical equipment, and is the main standard and important basis to be implemented during the development of airborne electronic equipment; the GJB181 aircraft power supply characteristic standard is not only a requirement for the output characteristics of the aircraft power supply system, but also a restrictive requirement for the electrical energy use of airborne electronic equipment.

[0003] Since a large number of airborne electronic equipment need to perform pulsating voltage tests, when performing pulsating voltage tests, users need to observe signals from two perspectives of time domain and frequency domain, deeply understand and analyze the signals, and check the state of the device under test. However, in actual experiments, it is found that the frequency-domain value cannot be directly read from the oscilloscope, and only the time-domain signal on the oscilloscope can be read. Summary of the Invention

[0004] The purpose of the present invention is to provide a test method and system for observing time-domain waveforms and frequency-domain waveforms, and the technical problem to be solved is how to observe time-domain waveforms and frequency-domain waveforms simultaneously.

[0005] The present invention is achieved by the following technical solutions: In a first aspect, a test method for observing time-domain waveforms and frequency-domain waveforms is provided, including the following steps: Configure synchronization parameters between the signal source and the oscilloscope; Call a control command to obtain a set of time-domain data on the signal source and the oscilloscope to obtain a time-domain waveform; Use the FFTW library to convert the time-domain waveform into a frequency-domain waveform; Transmit the time-domain waveform and the frequency-domain waveform to a display interface for display.

[0006] Configuring synchronization parameters between the signal source and the oscilloscope ensures that the signal output from the signal source corresponds to the signal collected by the oscilloscope in time; collecting a set of time-domain data through control commands can truly reflect the time-domain characteristics of the signal; using the FFTW library to convert the time-domain waveform into a frequency-domain waveform, the FFTW library can calculate the discrete Fourier transform (DFT) in one or more dimensions, eliminating complex algorithm conversions and improving conversion efficiency; transmitting the time-domain waveform and the frequency-domain waveform to the display interface for display, providing it for users to observe and record. Users can simultaneously see the time-domain waveform and the frequency-domain waveform on the same display interface, facilitating intuitive comparison and analysis of the two. For example, when analyzing a periodic signal, users can observe characteristics such as the period and amplitude of the signal through the time-domain waveform, and at the same time observe the frequency components of the signal and their relative magnitudes through the frequency-domain waveform, which helps users to more deeply understand the characteristics of the signal and quickly discover possible problems in the signal.

[0007] Furthermore, using the FFTW library to convert the above time-domain waveform into a frequency-domain waveform, the specific steps include: Storing the above time-domain waveform into a container; wherein, the above time-domain waveform is composed of time-domain component waveforms at several frequencies at the same moment; Separating the above time-domain waveform according to frequency to obtain several time-domain component waveforms; Calling the library function fftw_plan_dft_r2c_1d in the above FFTW library to perform discrete Fourier transform on the time-domain component waveforms respectively to obtain several groups of frequency-domain waveforms.

[0008] The above time-domain waveform is a composite signal synthesized by time-domain component waveforms with different frequencies and different amplitudes. Storing the time-domain waveform synthesized by time-domain component waveforms with different frequencies and different amplitudes into a suitable container is convenient for subsequent access and data processing; decomposing the complex composite signal into basic components, each component corresponding to a specific frequency; through separation, it is possible to more clearly analyze the contribution of the time-domain component corresponding to each frequency to the overall signal. For each separated time-domain component waveform, call the fftw_plan_dft_r2c_1d function in the FFTW library to perform discrete Fourier transform (DFT); the frequency-domain data obtained through the above steps can be used to generate frequency-domain waveforms. These frequency-domain waveforms can display the amplitude and phase information of each frequency component, thereby helping users to better understand the frequency-domain characteristics of the signal.

[0009] Furthermore, through the above frequency-domain waveform, determine the frequency and voltage amplitude of the frequency-domain waveform; Call the standard voltage change range and standard duration at this frequency from the standard experimental data; Compare the above voltage amplitude with the standard voltage variation range to determine whether the above voltage amplitude is within the standard voltage variation range; If it is within the range, accumulate the continuous duration; when the above continuous duration is equal to the standard continuous duration, complete the test at this frequency; If it is not within the range, initialize the continuous duration; where the initial value of the above continuous duration is 0.

[0010] Through the frequency-domain waveform, determine the frequency of each frequency component and the corresponding voltage amplitude. Each peak in the frequency-domain waveform corresponds to a frequency component, and its amplitude represents the voltage amplitude of that frequency component. Standard experimental data usually includes a series of predefined parameters for evaluating whether the voltage amplitude and duration of the signal meet the expectations. Compare the voltage amplitude of the current frequency component with the standard voltage variation range to determine whether the voltage amplitude is within this range. The purpose is to check whether the voltage amplitude of the signal at this frequency is within the allowable range, record the duration of the signal within the allowable range, and the corresponding continuous time indicates the completion of the test at this frequency. Otherwise, reset the continuous duration to the initial value and adjust the input signal to re-perform the test operation at this frequency; when the voltage amplitude of the signal at this frequency does not meet the requirements, reset the continuous duration to the initial value and adjust the input signal to re-perform the test operation at this frequency.

[0011] Furthermore, take the modulus of the above frequency-domain waveform to obtain the voltage amplitude at the corresponding frequency.

[0012] Furthermore, define the WaveGenerator class and the SaveProject class, and define an access pointer in the SaveProject class; The above WaveGenerator class is used as the implementation class to obtain experimental data through the above WaveGenerator class; where the above experimental data includes the time-domain waveform and the frequency-domain waveform; The above SaveProject class is used as an externally visible class to access the WaveGenerator class through the access pointer in the above SaveProject class and save the access result.

[0013] Using the Pimpl design pattern, the implementation details of an externally visible class are placed in a separate implementation class, and the implementation class is indirectly accessed through a private pointer in the externally visible class. Since the results to be saved include not only experimental data but also the waveforms of the experiments, the waveforms are obtained through the interface of the WaveGenerator class. Because the WaveGenerator class contains the interface, if the traditional method of the Qt framework is used to transmit data by defining signals and slots, it will be complicated. To improve the system coupling degree, the Pimpl design pattern is selected to use the WaveGenerator class as the implementation class to obtain experimental data, and a new SaveProject class is defined as the externally visible class to implement the specific details of saving files.

[0014] In a second aspect, a test system for observing time-domain waveforms and frequency-domain waveforms is provided, and the test system is used to implement the above test method; The test system includes: a signal source, an oscilloscope, a device under test, and a host computer. The signal source is connected to the input end of the device under test, the oscilloscope is connected to the output end of the device under test, and the host computer is connected to the signal source and the oscilloscope; Synchronization parameters are configured between the signal source and the oscilloscope; The following operations are performed by the host computer: Call a control command to obtain a set of time-domain data on the signal source and the oscilloscope to obtain a time-domain waveform; Use the FFTW library to convert the time-domain waveform into a frequency-domain waveform; Transmit the time-domain waveform and the frequency-domain waveform to the display interface of the host computer for display.

[0015] Furthermore, the host computer is used to convert the time-domain waveform into a frequency-domain waveform using the FFTW library. The specific steps include: Store the time-domain waveform in a container; wherein, the time-domain waveform is composed of time-domain component waveforms at several frequencies at the same moment; Separate the time-domain waveform according to frequency to obtain several time-domain component waveforms; Call the library function fftw_plan_dft_r2c_1d in the FFTW library to perform discrete Fourier transform on the time-domain component waveforms respectively to obtain several groups of frequency-domain waveforms.

[0016] Furthermore, the host computer is also used to perform the following steps: Determine the frequency and voltage amplitude of the frequency-domain waveform through the frequency-domain waveform; Call the standard voltage change interval and standard duration at this frequency from the standard experimental data; Compare the above voltage amplitude with the standard voltage change range to determine whether the above voltage amplitude is within the standard voltage change range; If it is within the range, accumulate the continuous duration; when the above continuous duration is equal to the standard continuous duration, complete the test at this frequency; If it is not within the range, initialize the continuous duration; where the initial value of the above continuous duration is 0.

[0017] Compared with the prior art, the present invention has the following advantages and beneficial effects: Configure synchronization parameters between the signal source and the oscilloscope to ensure that the signal output from the signal source corresponds to the signal collected by the oscilloscope in time; collect a set of time-domain data through control commands, which can truly reflect the time-domain characteristics of the signal; use the FFTW library to convert the time-domain waveform into a frequency-domain waveform. The FFTW library can calculate the discrete Fourier transform (DFT) in one or more dimensions, eliminating complex algorithm conversions and improving conversion efficiency; transmit the time-domain waveform and the frequency-domain waveform to the display interface for display, providing them for the user to observe and record. The user can simultaneously see the time-domain waveform and the frequency-domain waveform on the same display interface, facilitating intuitive comparison and analysis of the two. For example, when analyzing a periodic signal, the user can observe characteristics such as the period and amplitude of the signal through the time-domain waveform, and at the same time observe the frequency components of the signal and their relative magnitudes through the frequency-domain waveform, which helps the user to more deeply understand the characteristics of the signal and quickly discover possible problems in the signal. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the following will briefly introduce the drawings required in the embodiments. It should be understood that the following drawings only show some embodiments of the present invention, and therefore should not be regarded as limiting the scope. For those of ordinary skill in the art, without creative efforts, other related drawings can also be obtained based on these drawings. In the drawings: Figure 1 is the test flow chart; Figure 2 is the time-domain waveform diagram of the oscilloscope; Figure 3 is the converted frequency-domain waveform diagram; Figure 4 is the schematic diagram of the display interface. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0019] To make the objectives, technical solutions, and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below with reference to the embodiments and the drawings. The illustrative embodiments of the present invention and their descriptions are only used to explain the present invention and are not intended to limit the present invention.

[0020] First Embodiment: A test method for observing time-domain waveforms and frequency-domain waveforms, comprising the following steps: Configure synchronization parameters between the signal source and the oscilloscope; Call a control command to obtain a set of time-domain data on the signal source and the oscilloscope, and obtain a time-domain waveform; Use the FFTW library to convert the above time-domain waveform into a frequency-domain waveform; Transmit the above time-domain waveform and frequency-domain waveform to a display interface for display.

[0021] Configuring synchronization parameters between the signal source and the oscilloscope ensures that the signal output from the signal source corresponds to the signal collected by the oscilloscope in time; collecting a set of time-domain data through a control command can truly reflect the time-domain characteristics of the signal; using the FFTW library to convert the time-domain waveform into a frequency-domain waveform, the FFTW library can calculate the discrete Fourier transform (DFT) in one or more dimensions, eliminating complex algorithm conversions and improving conversion efficiency; transmitting the time-domain waveform and frequency-domain waveform to the display interface for display provides it for users to observe and record. Users can simultaneously view the time-domain waveform and frequency-domain waveform on the same display interface, facilitating intuitive comparison and analysis of the two. For example, when analyzing a periodic signal, users can observe characteristics such as the period and amplitude of the signal through the time-domain waveform, and at the same time observe the frequency components of the signal and their relative magnitudes through the frequency-domain waveform, which helps users understand the characteristics of the signal more deeply and quickly discover possible problems in the signal.

[0022] For reference, the above synchronization parameters include: OUTPUT: SYNC{OFF|0|ON|1} SYNC: MODE{NORMAL|CARRIER} POLarity{NORMAL|INVERTED} Defines the status values related to SYNC under OUTPUT (the synchronization function can be turned off as OFF / 0 or turned on as ON / 1), as well as some attribute modes of SYNC itself (MODE can be the normal synchronization mode NORMAL or the carrier synchronization mode CARRIER) and polarity (POLarity can be the normal polarity NORMAL or the inverted polarity INVERTED).

[0023] For reference, at the start of the experiment, obtain the time-domain data points on the oscilloscope through the control command WAVEFORM:DATA?, and obtain a set of time-domain waveforms. The graph of this time-domain waveform displayed on the software interface is as Figure 2As shown in the figure; the number of time-domain data points collected depends on the storage depth. The larger the depth value, the more time-domain data points are obtained. Next, this data is transformed into frequency-domain data through FFTW, and then the calculated frequency-domain waveform is displayed on the interface, as Figure 3 shown, and provided to the user for observation and recording. The interface for displaying time-domain data and frequency-domain data is as Figure 4 shown, and the dots represent the time-domain data and frequency-domain data of the signal generator and the oscilloscope at the same moment.

[0024] Second Embodiment: Based on the first embodiment, use the FFTW library to transform the above time-domain waveform into a frequency-domain waveform. The specific steps include: Store the above time-domain waveform into a container; wherein, the above time-domain waveform is composed of time-domain component waveforms at several frequencies at the same moment; Separate the above time-domain waveform according to the frequency to obtain several time-domain component waveforms; Call the library function fftw_plan_dft_r2c_1d in the above FFTW library to perform discrete Fourier transform on the time-domain component waveforms respectively to obtain several groups of frequency-domain waveforms.

[0025] The above time-domain waveform is a composite signal synthesized by time-domain component waveforms with different frequencies and amplitudes. Store the time-domain waveform synthesized by time-domain component waveforms with different frequencies and amplitudes into a suitable container for subsequent access and data processing; decompose the complex composite signal into basic components, and each component corresponds to a specific frequency; through separation, the contribution of the time-domain component corresponding to each frequency to the overall signal can be analyzed more clearly. For each separated time-domain component waveform, call the fftw_plan_dft_r2c_1d function in the FFTW library to perform discrete Fourier transform (DFT); the frequency-domain data obtained through the above steps can be used to generate frequency-domain waveforms. These frequency-domain waveforms can display the amplitude and phase information of each frequency component, thereby helping the user better understand the frequency-domain characteristics of the signal.

[0026] For reference, first call the get_waveform() function to obtain the oscilloscope data points; then calculate the vertical scale, horizontal scale value, delay, and offset of the oscilloscope based on a pre-defined array containing preamble-related data; finally, process the waveform data through a loop and store the processing results in the xs container.

[0027] For reference, first obtain the size of the input data xs as the size fft_size of the fast Fourier transform (FFT); create the input / output buffer for the FFT; create an FFT calculation plan, specifying that the input is a real number array and the output is a complex number array, and use the FFTW_ESTIMATE flag to estimate the optimal execution strategy; perform the FFT transform; traverse the first half of the FFT result (since the FFT result is symmetric), calculate the amplitude of each frequency component, and store it in the frequencies vector; finally, release the created plan and buffer resources.

[0028] Third Embodiment: Based on any of the above embodiments, determine the frequency and voltage amplitude of the frequency-domain waveform through the above frequency-domain waveform; Call the standard voltage change range and standard duration at this frequency from the standard experimental data; Compare the above voltage amplitude with the standard voltage change range to determine whether the above voltage amplitude is within the standard voltage change range; If it is within, accumulate the duration; when the above duration is equal to the standard duration, complete the test at this frequency; If it is not within, initialize the duration; where the initial value of the above duration is 0.

[0029] Through the frequency-domain waveform, determine the frequency and corresponding voltage amplitude of each frequency component. Each peak in the frequency-domain waveform corresponds to a frequency component, and its amplitude represents the voltage amplitude of that frequency component. The standard experimental data usually includes a series of predefined parameters for evaluating whether the voltage amplitude and duration of the signal meet the expectations. Compare the voltage amplitude of the current frequency component with the standard voltage change range to determine whether the voltage amplitude is within this range, aiming to check whether the voltage amplitude of the signal at this frequency is within the allowable range, record the duration of the signal within the allowable range, and continue for the corresponding time, which means completing the test at this frequency. Otherwise, reset the duration to the initial value and adjust the input signal, and re-perform the test operation at this frequency; when the voltage amplitude of the signal at this frequency does not meet the requirements, reset the duration to the initial value and adjust the input signal, and re-perform the test operation at this frequency.

[0030] In a specific embodiment, take the modulus of the above frequency-domain waveform to obtain the voltage amplitude at the corresponding frequency.

[0031] Fourth Embodiment: Based on any of the above embodiments, during the implementation of the software, add an experimental result saving function and use the Pimpl design pattern; define the WaveGenerator class and the SaveProject class, and define an access pointer in the SaveProject class; The above WaveGenerator class is used as an implementation class to obtain experimental data through the above WaveGenerator class. Among them, the above experimental data includes time-domain waveforms and frequency-domain waveforms. The above SaveProject class is used as an externally visible class to access the WaveGenerator class through the access pointer in the above SaveProject class and save the access result.

[0032] Using the Pimpl design pattern, the implementation details of an externally visible class (usually all private non-virtual members) are placed in a separate implementation class, and in the externally visible class, a private pointer is used to indirectly access the implementation class. Since the results to be saved include not only experimental data but also the waveform diagrams of the experiments, and the waveform diagrams are obtained through the interface of the WaveGenerator class. Because the WaveGenerator class contains the interface, if the traditional Qt framework method of defining signal slots is used for data transmission, it will be complex. To improve the system coupling degree, the Pimpl design pattern is selected and the WaveGenerator class is used as the implementation class to obtain experimental data. By defining a new SaveProject class as the externally visible class, the specific details of saving files are implemented.

[0033] The fifth embodiment: An experimental system for observing time-domain waveforms and frequency-domain waveforms, which is used to implement the above experimental method. The experimental system includes: a signal source (which can be a signal generator), an oscilloscope, a device under test, and a host computer. The above signal source is connected to the input end of the device under test, the above oscilloscope is connected to the output end of the device under test, and the above host computer is connected to the signal source and the oscilloscope. Synchronization parameters are configured between the above signal source and the oscilloscope. The following operations are performed by the above host computer: Call the control command to obtain a set of time-domain data on the above signal source and oscilloscope to obtain the time-domain waveform. Use the FFTW library to convert the above time-domain waveform into a frequency-domain waveform. Transmit the above time-domain waveform and frequency-domain waveform to the display interface of the host computer for display.

[0034] A reference usage scenario is that both the oscilloscope and the signal generator are connected via network cables. Similar standard digital instruments and meters are generally equipped with USB / LAN / GPIB interfaces to control the devices through these interfaces. In these programmable instruments, the VISA technology is used to communicate with the control device. VISA is a high-level application programming interface for communicating with various instrument buses, providing a simple and easy-to-use set of control functions (i.e., control command set). In terms of application form, it is relatively simple, eliminating the complex network programming stage. The control commands use SCPI, which is an ASCII-based instrument command language. SCPI commands are based on a hierarchical structure (also known as a tree system). For example, there are two SCPI commands under a certain brand of signal generator: SYSTem:LFRequency:MODE AUTO means setting the mode of the line frequency under the SYSTem system to automatic; SYSTem:LFRequency:MODE? is used to obtain the line frequency under the SYSTem system.

[0035] In a specific embodiment, the above host computer is used to convert the above time-domain waveform into a frequency-domain waveform by using the FFTW library. The specific steps include: Store the above time-domain waveform in a container; wherein, the above time-domain waveform is composed of time-domain component waveforms at several frequencies at the same moment; Separate the above time-domain waveform according to frequency to obtain several time-domain component waveforms; Call the library function fftw_plan_dft_r2c_1d in the above FFTW library to perform discrete Fourier transform on the time-domain component waveforms respectively to obtain several groups of frequency-domain waveforms.

[0036] In a specific embodiment, the above host computer is further used to perform the following steps: Determine the frequency and voltage amplitude of the above frequency-domain waveform through the frequency-domain waveform; Call the standard voltage change range and standard duration at this frequency from the standard experimental data; Compare the above voltage amplitude with the standard voltage change range to determine whether the above voltage amplitude is within the standard voltage change range; If it is within, accumulate the duration; when the above duration is equal to the standard duration, complete the test at this frequency; If it is not within, initialize the duration; wherein, the initial value of the above duration is 0.

[0037] The specific embodiments described above further elaborate on the objective, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only for the specific embodiments of the present invention and is not used to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A test method for observing time-domain waveforms and frequency-domain waveforms, characterized in that, It includes the following steps: Configure synchronization parameters between the signal source and the oscilloscope; Call the control command to obtain a set of time-domain data on the signal source and the oscilloscope, and obtain the time-domain waveform; Use the FFTW library to convert the time-domain waveform into a frequency-domain waveform; Transmit the time-domain waveform and the frequency-domain waveform to the display interface for display.

2. The test method according to claim 1, characterized in that, Use the FFTW library to convert the time-domain waveform into a frequency-domain waveform. The specific steps include: Store the time-domain waveform in a container; wherein, the time-domain waveform is composed of time-domain component waveforms at several frequencies at the same moment; Separate the time-domain waveform according to the frequency to obtain several time-domain component waveforms; Call the library function fftw_plan_dft_r2c_1d in the FFTW library to perform discrete Fourier transform on the time-domain component waveforms respectively to obtain several groups of frequency-domain waveforms.

3. The test method according to claim 1, characterized in that Determine the frequency and voltage amplitude of the frequency-domain waveform through the frequency-domain waveform; Call the standard voltage change range and standard duration at this frequency from the standard experimental data; Compare the voltage amplitude with the standard voltage change range to determine whether the voltage amplitude is within the standard voltage change range; If it is within, accumulate the duration; when the duration is equal to the standard duration, complete the test at this frequency; If it is not within, initialize the duration; wherein, the initial value of the duration is 0.

4. The test method according to claim 3, characterized in that, Take the modulus of the frequency-domain waveform to obtain the voltage amplitude at the corresponding frequency.

5. The test method according to claim 1, characterized in that Define the WaveGenerator class and the SaveProject class, and define an access pointer in the SaveProject class; The WaveGenerator class is used as the implementation class to obtain experimental data through the WaveGenerator class; wherein, the experimental data includes the time-domain waveform and the frequency-domain waveform; The SaveProject class is used as the externally visible class to access the WaveGenerator class through the access pointer in the SaveProject class and save the access result.

6. A test system for observing time-domain waveforms and frequency-domain waveforms, characterized in that, This test system is used to implement the test method described in any one of claims 1 to 5; This test system includes: a signal source, an oscilloscope, a device under test, and a host computer. The signal source is connected to the input end of the device under test, the oscilloscope is connected to the output end of the device under test, and the host computer is connected to the signal source and the oscilloscope; Configure synchronization parameters between the signal source and the oscilloscope; The host computer performs the following operations: Call the control command to obtain a set of time-domain data on the signal source and the oscilloscope, and obtain the time-domain waveform; Use the FFTW library to convert the time-domain waveform into a frequency-domain waveform; Transmit the time-domain waveform and the frequency-domain waveform to the display interface of the host computer for display.

7. The test system according to claim 6, characterized in that, The host computer is used to use the FFTW library to convert the time-domain waveform into a frequency-domain waveform. The specific steps include: Store the time-domain waveform in a container; wherein, the time-domain waveform is composed of time-domain component waveforms at several frequencies at the same moment; Separate the time-domain waveform according to the frequency to obtain several time-domain component waveforms; Call the library function fftw_plan_dft_r2c_1d in the FFTW library to perform discrete Fourier transform on the time-domain component waveforms respectively, and obtain several groups of frequency-domain waveforms.

8. The test system according to claim 6, wherein The host computer is further configured to perform the following steps: Determine the frequency and voltage amplitude of the frequency-domain waveform through the frequency-domain waveform; Call the standard voltage change range and standard duration at this frequency from the standard experimental data; Compare the voltage amplitude with the standard voltage change range to determine whether the voltage amplitude is within the standard voltage change range; If it is within, accumulate the duration; when the duration is equal to the standard duration, complete the test at this frequency; If it is not within, initialize the duration; where the initial value of the duration is 0.

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