A method for processing pressure data in calibration of a standard cylinder of a gas cylinder
By using discrete Fourier transform and standard deviation discrimination methods, the problem of pressure data fluctuation and error during the calibration of gas cylinder standard cylinders was solved, and the accurate acquisition and processing of pressure data was achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2023-02-17
- Publication Date
- 2026-04-07
AI Technical Summary
In the calibration process of standard gas cylinders, existing technologies suffer from periodic fluctuations and peak pressures in pressure data acquisition, and the acquisition system is susceptible to electrical interference, leading to data errors and making it impossible to accurately obtain precise pressure values.
The fluctuation period is calculated by discrete Fourier transform, the real pressure curve is fitted by least squares method, and the error is judged by standard deviation. Peaks and gross errors are eliminated and real pressure data are retained.
Effectively distinguish and retain real pressure, eliminate erroneous data, and ensure the accuracy and authenticity of the collected data.
Smart Images
Figure CN116108671B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of data processing technology, and in particular to a method for processing pressure data in the calibration of gas cylinder standard bottles. Background Technology
[0002] Standard cylinders are specialized cylinders used to calibrate and verify the accuracy of external hydrostatic testing devices for gas cylinders. They serve as auxiliary and derivative standards for verifying and proving the accuracy and integrity of the testing system. The calibration process for standard cylinders is described in the national standard GB / T35015—2018. This standard specifies the rated working pressure and precise pressurization rate of the pressurizing equipment, and recommends the use of precision pressurization devices such as plunger pumps.
[0003] Current external pressure measurement methods for water pressure equipment generally employ precision pressure sensors as the acquisition front-end and PLCs or data acquisition cards as the acquisition hardware. Two data issues arise during pressure data acquisition: Firstly, due to the characteristics of the pressurizing device, its pressure output exhibits periodic fluctuations; secondly, at certain points in the period, pressure spikes may occur due to mechanical structure limitations; and thirdly, due to the electrical characteristics of the acquisition system or environmental interference, the acquired data may contain numerical pulses rather than the true pressure. The first case represents the true pressure and is periodic; the second case represents a gross error and should be eliminated. However, filtering the acquired pressure will reduce the true pressure and cannot effectively eliminate the second type of interference. Current technology does not address these issues in standard bottle pressure acquisition, resulting in the inability to obtain precise pressure values. Summary of the Invention
[0004] The purpose of this invention is to provide a pressure data processing method in the calibration of gas cylinder standard bottles, which can effectively distinguish different situations in the pressure acquisition process of standard bottles, retain the true pressure, eliminate gross error data, and ensure the authenticity of the acquired data.
[0005] To achieve the above objectives, the present invention provides a method for processing pressure data during the calibration of gas cylinder standard cylinders, the specific steps of which include:
[0006] S1 acquires the pressure rise curve of the standard bottle, calculates the fluctuation period, divides the time into six moments according to the fluctuation period, obtains five periods, and determines the number of points of the periodic fluctuation according to the sampling frequency.
[0007] S2 takes the waveform of the standard bottle pressure rise curve with five points of the periodic fluctuation length, and calculates the pressure rise rate based on five times the number of pressure points of the periodic fluctuation length.
[0008] S3 calculates the pressure value based on the number of pressure points in the five described periodic fluctuations, and transforms the real pressure curve into an isobaric straight line.
[0009] S4 calculates the standard deviation of the pressure value sequence in each cycle based on the number of points of the cycle fluctuation and the pressure value of each point, and uses three times the standard deviation for error discrimination in one cycle;
[0010] S5 After the five cycles are determined, the subsequent standard bottle pressure rise curve is processed using steps S1-S4.
[0011] The specific steps of S1 are as follows:
[0012] Obtain the pressure rise curve of the standard bottle and determine the first moment. Start collecting data from the first moment and take a number of points along the collection length. Perform a discrete Fourier transform on the data. The reciprocal of the fundamental frequency is the fluctuation period, which is the period from the first moment to the second moment, the second moment to the third moment, the third moment to the fourth moment, the fourth moment to the fifth moment, and the fifth moment to the sixth moment, for a total of five fluctuation periods.
[0013] The number of points of periodic fluctuation is obtained by multiplying the system's sampling frequency by the fluctuation period. The number of points of periodic fluctuation is the pressure value difference between two adjacent moments.
[0014] The specific steps of S2 are as follows:
[0015] Obtain the number of pressure value points that fluctuate five times the cycle between the pressure value at the first moment and the pressure value at the sixth moment;
[0016] By applying the least squares method to the pressure values of the five-fold periodic fluctuations, a straight line that best reflects the overall linear upward trend is obtained.
[0017] The specific steps of S3 are as follows:
[0018] Subtract the linear pressure value from the pressure values of the five-fold periodic fluctuations to obtain the waveform curve after removing the pressure increase. The timing of the peak pressure or sharp pulse remains unchanged, and the collected pressure values are transformed into isobaric linear values.
[0019] The specific steps of S4 are as follows:
[0020] Calculate the standard deviation of the pressure value sequence within each cycle based on the number of points of cycle fluctuation and the pressure value of each point;
[0021] There are no spikes if the pressure value in each cycle does not exceed three times the standard deviation;
[0022] If a pressure value exceeding three standard deviations is found in a cycle, the distance between that pressure value and the start of that cycle is set as the accounting distance. In the remaining four cycles, it is calculated whether there are pressure values exceeding three standard deviations within the pressure value point one accounting distance away from the start of each cycle and within the three pressure value points plus or minus one nearby.
[0023] If pressure values exceeding three standard deviations are found in the other four cycles, the pressure value cannot be identified as a spike, but rather as a cycle peak pressure; if no pressure values exceeding three standard deviations are found in the other four cycles, the pressure value is a spike and should be discarded.
[0024] This invention discloses a pressure data processing method for standard cylinder calibration. Starting from the first moment, data is collected at a length of points. A Discrete Fourier Transform is performed on these points, and the reciprocal of the fundamental frequency is the fluctuation period. There are five fluctuation periods in total. The number of points in the periodic fluctuation is obtained by multiplying the system's sampling frequency by the fluctuation period. Five pressure value points representing five times the periodic fluctuation are obtained between the pressure value at the first moment and the pressure value at the sixth moment. The least squares method is used to obtain a straight line that best reflects the overall linear upward trend. The linear pressure line value is subtracted from each of the five pressure value points representing five times the periodic fluctuation to obtain a waveform curve after removing the pressure increase portion. If the pressure value in each fluctuation period does not exceed three times the standard deviation, there are no spikes. If a spike occurs within a fluctuation period... If a pressure value exceeding three standard deviations is found, the distance between that pressure value and the starting point of the fluctuation cycle is set as the calculation distance. In the remaining four fluctuation cycles, the pressure value at one calculation distance from the starting point of each fluctuation cycle, and within three pressure values plus or minus one of those distances, is checked for pressure values exceeding three standard deviations. If pressure values exceeding three standard deviations are found in all four fluctuation cycles, this pressure value cannot be classified as a spike, but rather as a peak pressure of the fluctuation cycle. If no pressure values exceeding three standard deviations are found in the other four fluctuation cycles, this pressure value is considered a spike and is discarded. This effectively distinguishes different situations during the pressure acquisition process of the standard bottle, retains the true pressure, eliminates gross error data, and ensures the authenticity of the acquired data. Attached Figure Description
[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0026] Figure 1This is a flowchart of a pressure data processing method for standard gas cylinder calibration provided by the present invention.
[0027] Figure 2 This is a flowchart of step S1 of a pressure data processing method in the calibration of a gas cylinder standard provided by the present invention.
[0028] Figure 3 This is a flowchart of step S2 in a pressure data processing method for standard cylinder calibration provided by the present invention.
[0029] Figure 4 This is a flowchart of step S4 in a pressure data processing method for standard cylinder calibration provided by the present invention.
[0030] Figure 5 This is a standard bottle pressure rise curve of the present invention. Detailed Implementation
[0031] Embodiments of the present invention are described in detail below, examples of which are illustrated 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 intended to explain the present invention, and should not be construed as limiting the present invention.
[0032] Please see Figures 1 to 5 This invention provides a method for processing pressure data during the calibration of a gas cylinder standard, the specific steps of which include:
[0033] S1 acquires the pressure rise curve of the standard bottle, calculates the fluctuation period, divides the time into six moments according to the fluctuation period, obtains five periods, and determines the number of points of the periodic fluctuation based on the sampling frequency. The specific steps are as follows:
[0034] S101 acquires the pressure rise curve of the standard bottle and determines the first moment. Starting from the first moment, it collects data at a length of points and performs a discrete Fourier transform on the data. The reciprocal of the fundamental frequency is the fluctuation period, which is the period from the first moment to the second moment, the second moment to the third moment, the third moment to the fourth moment, the fourth moment to the fifth moment, and the fifth moment to the sixth moment, for a total of five fluctuation periods.
[0035] The six time points are T0, T1, T2, T3, T4, T5, and T6. The interval between any two adjacent time points is the period T, resulting in a total of five periods. Assuming the system's sampling frequency is Fs, the number of points in the periodic fluctuation is L, where L = T * Fs, meaning T1 = L + T0, T2 = T1 + L, T3 = T2 + L, and so on. Thus, the positions from T0 to T5 are completely determined. This method considers data processing for every five consecutive periods.
[0036] S102 calculates the number of points of periodic fluctuation based on the product of the system's sampling frequency and the fluctuation period. The number of points of periodic fluctuation is the pressure value difference between two adjacent moments.
[0037] Assuming the system's sampling frequency is Fs, then the number of periodic fluctuation points is L, where L = T * Fs, meaning T1 = L + T0, T2 = T1 + L, T3 = T2 + L, and so on; thus, the positions from T0 to T5 are completely determined. This method considers data processing for every 5 consecutive periods.
[0038] S2 takes the waveform of the standard bottle pressure rise curve with a length of five points of the aforementioned periodic fluctuations, and calculates the pressure rise rate based on five pressure value points with a length of five times the aforementioned periodic fluctuations. The specific steps are as follows:
[0039] S201 obtains a number of pressure value points with a five-fold cycle fluctuation between the pressure value at the first moment and the pressure value at the sixth moment;
[0040] Take five consecutive waveforms of length L, such as from time T0 to T5. Let the pressure value at T0 be P0 and the pressure value at T5 be P5, then there are 5*L pressure value points between them.
[0041] S202 uses the least squares method on the pressure values of the five-fold periodic fluctuation to obtain a straight line that best reflects the overall linear upward trend.
[0042] Applying the least squares method to these points yields a straight line L', which best reflects the overall linear increase characteristic.
[0043] S3 calculates the pressure values based on the number of pressure points in the five described periodic fluctuations, transforming the actual pressure curve into an isobaric straight line. The specific steps are as follows:
[0044] Subtract the linear pressure value from the pressure values of the five-fold periodic fluctuations to obtain the waveform curve after removing the pressure increase. The timing of the peak pressure or sharp pulse remains unchanged, and the collected pressure values are transformed into isobaric linear values.
[0045] Subtracting the linear pressure value from each of the 5*L pressure values yields a waveform curve with the pressure increase removed. However, the timing characteristics of the curve remain unchanged; that is, the timing of peak pressure or sharp pulses remains the same. Transforming the collected pressure values into isobaric linear values can be considered as a case of repeatable measurement with equal precision.
[0046] S4 calculates the standard deviation of the pressure value sequence within each cycle based on the number of points in the cycle fluctuation and the pressure value at each point, and uses three times the standard deviation for error discrimination within a cycle. The specific steps are as follows:
[0047] S401 calculates the standard deviation of the pressure value sequence in each cycle based on the number of points of cycle fluctuation and the pressure value of each point;
[0048] Assume T0 to T1 is the first cycle, T1 to T2 is the second cycle, T2 to T3 is the third cycle, T3 to T4 is the fourth cycle, and T4 to T5 is the fifth cycle. Within each cycle, perform the following processing: calculate the standard deviation σ of the pressure value sequence for that cycle based on the number of points L and the pressure value at each point.
[0049] S402: If the pressure value in each cycle does not exceed three times the standard deviation, there will be no spikes.
[0050] If the pressure value in each cycle does not exceed 3σ, then it is considered that there is no spike in that cycle.
[0051] S403 If a pressure value exceeding three standard deviations is found in a cycle, the distance between the pressure value and the start of the cycle is set as the accounting distance. In the remaining four cycles, it is calculated whether there are pressure values exceeding three standard deviations within the pressure value point one accounting distance away from the start of each cycle and within the three pressure value points plus or minus one nearby.
[0052] If pressure values exceeding three standard deviations are found in the other four cycles, the pressure value cannot be identified as a spike, but rather as a cycle peak pressure. If no pressure value exceeding three standard deviations is found in the other four cycles, the pressure value is identified as a spike and is discarded.
[0053] If a point exceeding 3σ is found within a cycle, such as point K1 in the figure, and this point is Δ points away from the start of that cycle, then calculate whether there are any points exceeding 3σ within Δ points and their vicinity plus or minus 3 points in the remaining 4 cycles. If points exceeding 3σ are found in all other cycles, they cannot be identified as pulse spikes, but rather as periodic peak pressures, such as point J1 in the figure. If no such points are found in other cycles, then this point is a pulse spike and is discarded, such as point K1.
[0054] S5 After the five cycles are determined, the subsequent standard bottle pressure rise curve is processed using steps S1-S4.
[0055] The above-disclosed embodiments are merely one or more preferred embodiments of this application and should not be construed as limiting the scope of this application. Those skilled in the art can understand that all or part of the processes for implementing the above embodiments and equivalent changes made in accordance with the claims of this application still fall within the scope of this application.
Claims
1. A method for processing pressure data during the calibration of a gas cylinder standard bottle, characterized in that, The specific steps include: S1 acquires the pressure rise curve of the standard bottle, calculates the fluctuation period, divides the time into six moments according to the fluctuation period, obtains five periods, and determines the number of points of the periodic fluctuation according to the sampling frequency. S2 takes the waveform of the standard bottle pressure rise curve with five points of the periodic fluctuation length, and calculates the pressure rise rate based on five times the number of pressure points of the periodic fluctuation length. S3 calculates the pressure value based on the number of pressure points in the five described periodic fluctuations, and transforms the real pressure curve into an isobaric straight line. S4 calculates the standard deviation of the pressure value sequence in each cycle based on the number of points of the cycle fluctuation and the pressure value of each point, and uses three times the standard deviation for error discrimination in one cycle; S5 After the five cycles are determined, the subsequent standard bottle pressure rise curve is processed using steps S1-S4. The specific steps of S1 are as follows: Obtain the pressure rise curve of the standard bottle and determine the first moment. Start collecting data from the first moment and take a number of points along the collection length. Perform a discrete Fourier transform on the data. The reciprocal of the fundamental frequency is the fluctuation period, which is the period from the first moment to the second moment, the second moment to the third moment, the third moment to the fourth moment, the fourth moment to the fifth moment, and the fifth moment to the sixth moment, for a total of five fluctuation periods. The number of points of periodic fluctuation is obtained by multiplying the system's sampling frequency by the fluctuation period. The number of points of periodic fluctuation is the pressure value difference between two adjacent moments.
2. The pressure data processing method in the calibration of a gas cylinder standard bottle as described in claim 1, characterized in that, The specific steps of S2 are as follows: Obtain the number of pressure value points that fluctuate five times the cycle between the pressure value at the first moment and the pressure value at the sixth moment; By applying the least squares method to the pressure values of the five-fold periodic fluctuations, a straight line that best reflects the overall linear upward trend is obtained.
3. The pressure data processing method in the calibration of a gas cylinder standard bottle as described in claim 2, characterized in that, The specific steps for S3 are as follows: Subtract the linear pressure value from the pressure values of the five-fold periodic fluctuations to obtain the waveform curve after removing the pressure increase. The timing of the peak pressure or sharp pulse remains unchanged, and the collected pressure values are transformed into isobaric linear values.
4. The pressure data processing method in the calibration of a gas cylinder standard bottle as described in claim 3, characterized in that, The specific steps of S4 are as follows: Calculate the standard deviation of the pressure value sequence within each cycle based on the number of points of cycle fluctuation and the pressure value of each point; There are no spikes if the pressure value in each cycle does not exceed three times the standard deviation; If a pressure value exceeding three standard deviations is found in a cycle, the distance between that pressure value and the start of that cycle is set as the accounting distance. In the remaining four cycles, it is calculated whether there are pressure values exceeding three standard deviations within the pressure value point one accounting distance away from the start of each cycle and within the three pressure value points plus or minus one nearby. If pressure values exceeding three standard deviations are found in the other four cycles, the pressure value cannot be identified as a spike, but rather as a cycle peak pressure; if no pressure values exceeding three standard deviations are found in the other four cycles, the pressure value is a spike and should be discarded.
Citation Information
Patent Citations
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