SF6 gas density measurement and error compensation system based on dynamic segment calibration

Abstract

The application discloses a kind of SF6 gas density measurement and error compensation system based on dynamic segmentation calibration, it is related to gas pressure and density measurement technical field, including gas pressure sampling module, for the weak analog signal amplified and complete analog-digital conversion to pressure sensor output, obtain the digital sampling data for pressure calculation;Gas density calculation module is used to establish density solution model based on the preset physical state equation and output gas density calculation value;Gas density calibration module is used to segment calibration with preset reference pressure point as reference to the pressure interval corresponding to density calculation value and output calibrated density measurement result, the application proposes a kind of weak signal high-precision sampling amplification, based on betty-brichman equation's fast iteration density, with 0.5MPa as the benchmark of dynamic segmentation asymmetric calibration three system linkage SF6 gas density high-precision measurement system.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of gas pressure and density measurement, and particularly relates to an SF6 gas density measurement and error compensation system based on dynamic segmented calibration. BACKGROUND

[0002] SF6 gas is used in gas insulated switchgear (GIS) to maintain insulation and arc extinguishing performance. The density of SF6 gas changes with temperature fluctuation and leakage. If the density is lower than a threshold value, the insulation performance will be significantly reduced, and a safety risk will be caused. Therefore, a real-time density monitoring system is required according to relevant standards.

[0003] The existing density monitoring scheme has the following problems: a weak voltage signal is easily disturbed by noise in a sampling link, resulting in insufficient precision; a single calibration strategy is difficult to compensate for nonlinear errors of a sensor in different pressure intervals; and when a complex physical state equation is used, the limited computing power of an embedded device makes it difficult to realize fast solving and real-time output. SUMMARY

[0004] The application aims to provide an SF6 gas density measurement and error compensation system based on dynamic segmented calibration to solve the problems in the background.

[0005] To solve the above technical problems, the application provides the following technical scheme: an SF6 gas density measurement and error compensation system based on dynamic segmented calibration, comprising a gas pressure sampling module, a gas density calculation module and a gas density calibration module.

[0006] According to the above technical scheme, the gas pressure sampling module comprises a pressure sensor interface unit, an instrument amplification unit, an analog-to-digital conversion unit and a sampling calculation unit, wherein the pressure sensor interface unit is used to access a 0-20 mV level sensor output signal, the instrument amplification unit is used to amplify the signal to a voltage range suitable for an ADC reference voltage, the analog-to-digital conversion unit is used to output a digital sampling value, and the sampling calculation unit is used to convert the digital sampling value to obtain a pressure initial value.

[0007] The gas density calculation module comprises an equation construction unit, a density equation transformation unit, an iterative solution unit and a convergence determination unit, wherein the equation construction unit is configured to load a parameterized model of the Bethe-Bridgman equation, the density equation transformation unit is configured to form a root-finding equation with density as an unknown quantity, the iterative solution unit is configured to quickly iterate to obtain a density value under embedded computing power conditions, and the convergence determination unit is configured to determine whether the iteration result meets a preset accuracy threshold;

[0008] The gas density calibration module comprises a reference point setting unit, a low-pressure section calibration unit, a high-pressure section calibration unit and an adaptive adjustment unit, wherein the reference point setting unit is configured to set 0.5 MPa as a calibration reference point, the low-pressure section calibration unit and the high-pressure section calibration unit are respectively configured to apply a proportional coefficient and an offset in corresponding pressure intervals, and the adaptive adjustment unit is configured to update the proportional coefficient and the offset according to an error direction.

[0009] According to the above technical solution, the following steps are included:

[0010] S1: Perform pressure signal acquisition to obtain an analog voltage signal output by a pressure sensor, and perform amplification processing on the analog voltage signal to meet the input range requirements of subsequent analog-to-digital conversion;

[0011] S2: Perform analog-to-digital conversion and pressure initial value calculation to obtain a digital sampling value by performing analog-to-digital conversion on the amplified voltage signal, and obtain a pressure initial value based on a sampling calculation relationship;

[0012] S3: Perform density calculation to convert a physical state equation into a density solving model and obtain a density calculation value through iteration to meet the real-time calculation requirements of embedded devices;

[0013] S4: Perform dynamic segmented calibration to divide a full-range pressure into at least two pressure intervals with reference to a preset reference pressure point, and apply different calibration parameters in different pressure intervals to compensate for nonlinear errors;

[0014] S5: Output measurement results to display, communication or monitoring interfaces after calibration, and meet the requirements of industrial real-time monitoring on response time.

[0015] According to the above technical solution, the S1-S2 are specifically:

[0016] S1-1: signal conditioning and amplification, the analog voltage signal output by the pressure sensor is connected to the input terminal of the instrument amplifier, and the analog voltage signal is a weak signal of 0-20mV; by setting the resistance network of the instrument amplifier, the gain is fixed as G=85.32, so that the amplified sampling voltage falls within the range of 0-2.5V and matches the ADC reference voltage, thereby improving the signal-to-noise ratio on the hardware side and avoiding ADC input overload; wherein G is the amplification factor of the instrument amplifier, and the amplified sampling voltage is denoted as Vs;

[0017] S2-1, analog-to-digital conversion and digital quantity definition, analog-to-digital conversion of the sampling voltage Vs under the ADC reference voltage Vref, satisfying: Vs / Vref=Nadc / NFS; wherein Nadc is the ADC output code value obtained by one sampling, and NFS is the upper limit value of the ADC range, NFS is 4095; the one-to-one correspondence between the analog quantity Vs and the digital quantity Nadc is established through the proportional relationship, so as to subsequently calculate the pressure initial value and error compensation in a digital manner;

[0018] S2-2: inverse calculation of amplification factor and formation of pressure initial value, the sampling voltage Vs is obtained according to Nadc, NFS and Vref, and the sampling voltage is converted into the original voltage at the output end of the sensor combined with the amplification factor G, and then the original voltage is converted into the pressure initial value Praw according to the pre-stored calibration curve of the pressure sensor; wherein Praw is the pressure value before the segmented calibration is performed, which is used as the input quantity for subsequent density equation solving and segmented calibration, so as to ensure that the input definition of the calculation link is single and traceable.

[0019] According to the above technical solution, the S3 is specifically:

[0020] S3-1: density solving model construction, the Betti-Bridgman equation is parameterized and loaded on the controller side, and the equation is equivalent transformed according to the form that the density is unknown, to form the density solving equation f(D)=0; wherein D is the SF6 gas density to be solved, and f(D) is the density residual function, which is obtained by substituting the pressure initial value Praw obtained in step S2 into the parameterized equation, so that the subsequent solving target is to find the root of the residual function.

[0021] S3-2: Iterative update and derivative meaning definition, using Newton-Leibniz iteration method to iteratively update the density solving equation, the iterative relationship is: D{n+1}=Dn−f(Dn) / f'(Dn); wherein Dn is the density value of the nth iteration, D{n+1} is the density value of the n+1 iteration, f'(Dn) is the derivative value of the derivative of the density residual function f(D) with respect to the density D at Dn; By introducing f'(Dn), the iteration direction and step size are adaptively changed with the local slope of the residual curve, so as to improve the convergence speed under the embedded condition and reduce the number of iterations;

[0022] S3-3: Initial value and convergence output rule, initialize the density value D0=0, and set the convergence threshold ε; When |D{n+1}−Dn|≤ε is satisfied, it is determined that the iteration result converges and the density calculation value Dout is output; Dout is the density calculation output before performing the segmented calibration, which is used to enter the subsequent segmented calibration link, so as to determine when to stop iteration and output which density value.

[0023] According to the above technical scheme, the S4 includes the following sub-steps:

[0024] S4-1: Reference point setting and alignment purpose, set the reference pressure point Pb=0.5MPa, and take this reference point as the demarcation point between the low pressure section and the high pressure section; The measured value and the theoretical value at the reference pressure point are compared to determine which point is used as the overall error alignment point, so as to avoid that the interval nonlinear error is amplified due to the full range unified coefficient;

[0025] S4-2: Slope correction coefficient introduction, calculate the slope correction coefficient ks based on the measured value and the theoretical value, the ks is 0.981, which is used to uniformly correct the proportional error accumulated with the range growth in the pressure link; The coefficient is used as a common multiplier for subsequent segmented linear correction, so as to ensure that the segmented calibration does not damage the overall scale consistency;

[0026] S4-3: Definition of segmented intervals and parameter sets, divide the full range of pressure into a low pressure section ΓL and a high pressure section ΓH, wherein ΓL is a 0-0.5MPa interval, and ΓH is a 0.5-1MPa interval; Set the proportional coefficient ratioL and the offset offsetL for ΓL, and set the proportional coefficient ratioH and the offset offsetH for ΓH; wherein ratioL and ratioH are used to represent the segmented proportional correction strength, and offsetL and offsetH are used to represent the segmented zero point compensation, so that the calibration parameters of different pressure intervals are independent of each other;

[0027] S4-4: Piecewise linear correction and output pressure definition, perform piecewise linear correction on pressure initial value Praw to get calibrated pressure Pcal: when Praw falls into low pressure segment ΓL, complete linear correction with ks, ratioL and offsetL; when Praw falls into high pressure segment ΓH, complete linear correction with ks, ratioH and offsetH; wherein Pcal is the calibrated pressure output, used as the final output basis for density measurement results, thereby defining the execution rule of using different correction parameters in different intervals for the same pressure initial value.

[0028] According to the above technical solution, the S4 further comprises an adaptive calibration sub-step:

[0029] S4-5: Piecewise error calculation and sign meaning fixing, select corresponding reference calibration points in low pressure segment ΓL and high pressure segment ΓH respectively, compare the calibrated pressure Pcal at the reference calibration points with the reference pressure Pref to get low pressure segment error eL and high pressure segment error eH; wherein the positive and negative signs of eL and eH are used to represent the deviation direction, e>0 indicates that the calibration output is higher than the reference value, e<0 indicates that the calibration output is lower than the reference value, thereby converting the error direction into an executable parameter update trigger condition;

[0030] S4-6: Deterministic update rule based on error direction, when eL>0, simultaneously decrease ratioL and offsetL by a preset update step; when eL<0, simultaneously increase ratioL and offsetL by a preset update step; when eL=0, keep ratioL and offsetL unchanged; the same update rule is applied to ratioH and offsetH for high pressure segment error eH; wherein the update step is a positive number fixed in advance, so that the parameter update has a determined direction and a determined amplitude in each adaptive iteration, thereby avoiding the understanding obstacle of adjusting but not knowing how to adjust;

[0031] S4-7: Closed-loop calibration termination condition, after completing a parameter update, execute step S4-4 again to get new Pcal, and recalculate eL and eH; when the full range error is less than 0.1%, terminate the adaptive calibration process and fix the current ratioL, offsetL, ratioH and offsetH; wherein the full range error is the maximum value of the relative error at each calibration point, used as the only judgment index for whether to end the adaptive calibration.

[0032] According to the above technical solution, the S5 comprises the following constraints and output control:

[0033] S5-1: Real-time linkage scheduling boundary, pressure sampling, density calculation and segmented calibration are executed as a serial processing link in the same measurement cycle, and one measurement result is output after completing one link processing, so that the response time of the whole process of sampling-processing-output is less than 10ms; wherein the response time is defined as the time interval from triggering one ADC sampling to obtaining the final output result, so as to give a clear and verifiable measurement criterion for real-time indicators;

[0034] S5-2: Density calculation accuracy constraint and output association, the solving error of the density calculation module is controlled to be less than 0.05% in the link, and the density calculation output Dout meeting the accuracy constraint is taken as the input of the segmented calibration, so that the density calculation result meets the basic accuracy requirement before entering the segmented calibration, thereby ensuring that the subsequent calibration is mainly used to compensate the segmented nonlinear error of the sensor rather than to compensate the model solving error;

[0035] S5-3: Final output quantity definition, the final density measurement result Dcal is formed based on the calibrated pressure Pcal and is output, the Dcal is the density result compensated by the segmented calibration parameters, and is used for real-time monitoring and safety threshold determination of the GIS device, so that the output object remains unique and consistent.

[0036] Compared with the prior art, the beneficial effects achieved by the present application are: the present scheme amplifies the 0-20mV level weak signal through the instrument amplifier and maps it into the ADC reference range, realizes high-precision sampling and pressure initial value calculation of the low-level signal, converts the Betti-Bridgman equation into a density solving equation and uses the iterative method to quickly converge on the embedded side, realizes microsecond-level solving and reduces the calculation burden, at the same time, sets the proportional coefficient and offset of the low-pressure section and the high-pressure section independently with 0.5MPa as the reference point, and combines the error direction for adaptive adjustment, so that the full-range error is controlled within 0.1%; the real-time linkage of the three modules makes the whole process of sampling-processing-output less than 10ms, which meets the real-time and accuracy requirements of GIS online monitoring. BRIEF DESCRIPTION OF DRAWINGS

[0037] The accompanying drawings are included to provide a further understanding of the application, and constitute a part of the specification, which together with the embodiments of the application, serve to explain the application, and do not constitute a limitation on the application. In the drawings:

[0038] Figure 1 is a schematic diagram of the overall module structure of the present application. DETAILED DESCRIPTION

[0039] With reference to the drawings of the embodiments of the present application, the technical solutions in the embodiments of the present application will be described clearly and completely. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments of the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0040] Please refer to Figure 1 The present application provides a technical solution: an SF6 gas density measurement and error compensation system based on dynamic segmentation calibration, comprising a gas pressure sampling module, which is used for amplifying and completing analog-to-digital conversion of a weak analog signal output by a pressure sensor, to obtain digital sampling data for pressure calculation; a gas density calculation module, which is used for establishing a density solving model based on a preset physical state equation and outputting a gas density calculation value; and a gas density calibration module, which is used for segmenting and calibrating a pressure interval corresponding to the density calculation value with reference to a preset reference pressure point and outputting a calibrated density measurement result.

[0041] The gas pressure sampling module comprises a pressure sensor interface unit, an instrument amplification unit, an analog-to-digital conversion unit, and a sampling calculation unit, wherein the pressure sensor interface unit is used for accessing a 0-20 mV level sensor output signal, the instrument amplification unit is used for amplifying the signal to a voltage range suitable for an ADC reference voltage, the analog-to-digital conversion unit is used for outputting a digital sampling value, and the sampling calculation unit is used for converting the digital sampling value to obtain a pressure initial value.

[0042] The gas density calculation module comprises an equation construction unit, a density equation transformation unit, an iterative solving unit, and a convergence judgment unit, wherein the equation construction unit is used for loading a parameterized model of the Bethe-Bridgman equation, the density equation transformation unit is used for forming a root-finding equation with density as an unknown quantity, the iterative solving unit is used for quickly iterating to obtain a density value under the condition of embedded computing power, and the convergence judgment unit is used for judging whether the iteration result meets a preset accuracy threshold.

[0043] The gas density calibration module comprises a reference point setting unit, a low-pressure segment calibration unit, a high-pressure segment calibration unit, and an adaptive adjustment unit, wherein the reference point setting unit is used for setting 0.5 MPa as a calibration reference point, the low-pressure segment calibration unit and the high-pressure segment calibration unit are respectively used for applying a proportionality coefficient and an offset in the corresponding pressure interval, and the adaptive adjustment unit is used for updating the proportionality coefficient and the offset according to the error direction.

[0044] The method comprises the following steps:

[0045] S1: Perform pressure signal acquisition, acquire an analog voltage signal output by a pressure sensor, and amplify the analog voltage signal to meet the input range requirement of subsequent analog-to-digital conversion;

[0046] S2: performing analog-digital conversion and pressure initial value calculation, performing analog-digital conversion on the amplified voltage signal to obtain a digital sampling value, and obtaining a pressure initial value based on the sampling calculation relationship;

[0047] S3: performing density calculation, converting the physical state equation into a density solving model and obtaining a density calculation value through iteration to meet the real-time calculation requirements of the embedded device;

[0048] S4: performing dynamic segmented calibration, taking a preset reference pressure point as a reference, dividing the full range of pressure into at least two pressure intervals, and applying different calibration parameters in different pressure intervals to compensate for nonlinear errors;

[0049] S5: outputting the measurement results, outputting the calibrated density measurement results to a display, communication or monitoring interface, and meeting the requirements of industrial real-time monitoring on response time;

[0050] S1-S2 are specifically:

[0051] S1-1: signal conditioning and amplification, connecting the analog voltage signal output by the pressure sensor to the input end of the instrument amplifier, the analog voltage signal being a weak signal of 0-20mV magnitude; setting the resistance network of the instrument amplifier to make its gain fixed at G=85.32, so that the amplified sampling voltage falls within the range of 0-2.5V and matches the ADC reference voltage, thereby improving the signal-to-noise ratio on the hardware side and avoiding ADC input overload; where G is the amplification factor of the instrument amplifier, and the amplified sampling voltage is denoted as Vs;

[0052] S2-1, analog-digital conversion and digital quantity definition, analog-digital conversion of the sampling voltage Vs under the ADC reference voltage Vref, satisfying: Vs / Vref=Nadc / NFS; where Nadc is the ADC output code value obtained by one sampling, and NFS is the upper limit value of the ADC range, NFS being 4095; the analog quantity Vs and the digital quantity Nadc are established in a one-to-one correspondence through this proportional relationship, so as to subsequently perform pressure initial value calculation and error compensation in a digital manner;

[0053] S2-2: amplification factor inverse calculation and pressure initial value formation, inversely calculating the sampling voltage Vs based on Nadc, NFS and Vref, and converting the sampling voltage into the original voltage at the output end of the sensor in combination with the amplification factor G, and then converting the original voltage into the pressure initial value Praw according to the pre-stored calibration curve of the pressure sensor; where Praw is the pressure value before segmented calibration is performed, and is used as the input quantity for subsequent density equation solving and segmented calibration to ensure that the input definition of the calculation link is single and traceable;

[0054] S3 is specifically:

[0055] S3-1: Density solving model construction, parameterized loading of the Bethe-Bridgman equation on the controller side, and equivalent transformation of the equation in the form of density as an unknown quantity to form a density solving equation f(D)=0; wherein D is the SF6 gas density to be solved, f(D) is a density residual function, and the residual function is obtained by substituting the pressure initial value Praw obtained in step S2 into the parameterized equation, so that the subsequent solving target is clear as a root-finding problem of making the residual zero;

[0056] S3-2: Iterative update and derivative meaning limitation, the Newton-Leibnitz iteration method is used to iteratively update the density solving equation, and the iterative relationship is: D{n+1}=Dn−f(Dn) / f'(Dn); wherein Dn is the density value of the nth iteration, D{n+1} is the density value of the n+1th iteration, and f'(Dn) is the derivative value of the density residual function f(D) with respect to the density D at Dn; by introducing f'(Dn), the iteration direction and step length are adaptively changed with the local slope of the residual curve, so as to improve the convergence speed and reduce the number of iterations under the embedded condition;

[0057] S3-3: Initial value and convergence output rule, initialize the density value D0=0, and set the convergence threshold ε; when |D{n+1}−Dn|≤ε is satisfied, it is determined that the iteration result converges and the density calculation value Dout is output; Dout is the density calculation output before performing the segmented calibration, which is used to enter the subsequent segmented calibration link, so as to determine when to stop iteration and output which density value;

[0058] S4 includes the following sub-steps:

[0059] S4-1: Reference point setting and alignment purpose, set the reference pressure point Pb=0.5MPa, and take this reference point as the dividing point of the low pressure section and the high pressure section; compare the measured value and the theoretical value at the reference pressure point to determine which point is used as the overall error alignment point, so as to avoid that the interval nonlinear error is amplified due to only the unified coefficient of the full range;

[0060] S4-2: Slope correction coefficient introduction, calculate the slope correction coefficient ks based on the measured value and the theoretical value, ks takes 0.981, and is used for unified correction of the proportional error accumulated with the increase of the range in the pressure link; the coefficient is used as a common multiplier for subsequent segmented linear correction, so as to ensure that the segmented calibration does not damage the overall scale consistency;

[0061] S4-3: Subsection interval and parameter set definition, the full range of pressure is divided into low pressure section GL and high pressure section GH, wherein GL is 0-0.5 MPa interval, GH is 0.5-1 MPa interval; the proportional coefficient ratioL and the offset offsetL are set for GL respectively, the proportional coefficient ratioH and the offset offsetH are set for GH; wherein ratioL, ratioH are used to represent the subsection proportional correction strength, offsetL, offsetH are used to represent the subsection zero point compensation amount, so that the calibration parameters of different pressure intervals are independent of each other;

[0062] S4-4: Subsection linear correction and output pressure definition, the subsection linear correction is performed on the pressure initial value Praw to obtain the calibrated pressure Pcal: when Praw falls into the low pressure section GL, the linear correction is completed by using ks, ratioL and offsetL; when Praw falls into the high pressure section GH, the linear correction is completed by using ks, ratioH and offsetH; wherein Pcal is the calibrated pressure output, which is used as the final output basis of the density measurement result, thereby the execution rule of using different correction parameters in different intervals for the same pressure initial value is determined;

[0063] S4 further comprises an adaptive calibration sub-step:

[0064] S4-5: Subsection error amount calculation and sign meaning fixation, the corresponding reference calibration points are selected in the low pressure section GL and the high pressure section GH, the calibrated pressure Pcal at the reference calibration points is compared with the reference pressure Pref, the low pressure section error eL and the high pressure section error eH are obtained; wherein the positive and negative signs of eL, eH are used to represent the deviation direction, e>0 represents that the calibration output is higher than the reference value, e<0 represents that the calibration output is lower than the reference value, thereby the error direction is converted into an executable parameter update trigger condition;

[0065] S4-6: Deterministic update rule based on error direction, when eL>0, ratioL and offsetL are simultaneously reduced by a preset update step; when eL<0, ratioL and offsetL are simultaneously increased by a preset update step; when eL=0, ratioL and offsetL remain unchanged; the same update rule is used for eH to act on ratioH and offsetH; wherein the update step is a positive number fixed in advance, so that the parameter update has a determined direction and a determined amplitude in each adaptive iteration, thereby avoiding the understanding obstacle that adjustment is made but it is not clear how to adjust;

[0066] S4-7: Closed-loop calibration termination condition. After completing one parameter update, step S4-4 is executed again to obtain the new Pcal, and eL and eH are recalculated. When the full-range error is less than 0.1%, the adaptive calibration process is terminated and the current ratioL, offsetL, ratioH, and offsetH are fixed. The full-range error is the maximum value of the relative error at each calibration point, which is used as the sole criterion for determining whether the adaptive calibration has ended.

[0067] S5 includes the following constraints and output controls:

[0068] S5-1: Real-time linkage scheduling boundary, pressure sampling, density calculation and segment calibration are executed as a series processing link within the same measurement cycle. After completing one link processing, one measurement result is output, so that the entire process response time of sampling-processing-output is less than 10ms. The response time is defined as the time interval from the start of triggering an ADC sampling to the end of obtaining the final output result, so as to provide a clear and verifiable measurement standard for real-time indicators.

[0069] S5-2: Density calculation accuracy constraints are associated with output. The solution error of the density calculation module in the link is controlled to be less than 0.05%, and the density calculation output Dout that meets the accuracy constraints is used as the input for segment calibration. This ensures that the density calculation results meet the basic accuracy requirements before entering the segment calibration, thereby ensuring that the subsequent calibration is mainly used to compensate for the segment nonlinearity error of the sensor rather than to make up for the model solution error.

[0070] S5-3: Final output definition. Based on the calibration pressure Pcal, the final density measurement result Dcal is generated and output. Dcal is the density result after compensation by segmented calibration parameters. It is used for real-time monitoring and safety threshold determination of GIS equipment to ensure the uniqueness and consistency of the output object.

[0071] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "include," "contain," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus.

[0072] Finally, it should be noted that the above only describes the preferred embodiments of the present application and is not intended to limit the present application. Although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art will appreciate that the technical solutions described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalent ones. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A system for measuring and compensating the density of SF6 gas based on dynamic segmented calibration, characterized in that: It includes a gas pressure sampling module, which amplifies the weak analog signal output by the pressure sensor and performs analog-to-digital conversion to obtain digital sampling data for pressure calculation; and a gas density calculation module, which establishes a density solution model based on a preset physical state equation and outputs the calculated gas density value. The gas density calibration module is used to perform segmented calibration of the pressure range corresponding to the density calculation value with a preset reference pressure point and output the calibrated density measurement results. The gas pressure sampling module includes a pressure sensor interface unit, an instrument amplification unit, an analog-to-digital conversion unit, and a sampling calculation unit. The pressure sensor interface unit is used to receive the output signal of a 0–20mV level sensor, the instrument amplification unit is used to amplify the signal to a voltage range that matches the ADC reference voltage, the analog-to-digital conversion unit is used to output digital sampled values, and the sampling calculation unit is used to calculate the initial pressure value from the digital sampled values. The gas density calculation module includes an equation construction unit, a density equation transformation unit, an iterative solution unit, and a convergence determination unit. The equation construction unit is used to load the parameterized model of the Bertie-Bridgeman equation, the density equation transformation unit is used to form a root-finding equation with density as the unknown, the iterative solution unit is used to quickly iterate to obtain the density value under embedded computing power conditions, and the convergence determination unit is used to determine whether the iteration result meets the preset accuracy threshold. The gas density calibration module includes a reference point setting unit, a low-pressure section calibration unit, a high-pressure section calibration unit, and an adaptive adjustment unit. The reference point setting unit is used to set 0.5MPa as the calibration reference point. The low-pressure section calibration unit and the high-pressure section calibration unit are used to apply a proportional coefficient and an offset in the corresponding pressure range, respectively. The adaptive adjustment unit is used to update the proportional coefficient and the offset according to the error direction.

2. The SF6 gas density measurement and error compensation system based on dynamic segmented calibration according to claim 1, characterized in that: Includes the following steps: S1: Perform pressure signal acquisition, obtain the analog voltage signal output by the pressure sensor, and amplify the analog voltage signal to meet the input range requirements of subsequent analog-to-digital conversion; S2: Perform analog-to-digital conversion and initial pressure calculation. Perform analog-to-digital conversion on the amplified voltage signal to obtain digital sampled values, and obtain the initial pressure value based on the sampling calculation relationship; S3: Perform density calculation, transform the physical state equation into a density solution model and obtain the density calculation value through an iterative method to meet the real-time computing requirements of embedded devices; S4: Perform dynamic segmented calibration, using a preset reference pressure point as a reference, divide the entire pressure range into at least two pressure intervals, and apply different calibration parameters in different pressure intervals to compensate for nonlinear errors; S5: Output measurement results. Output the calibrated density measurement results to the display, communication or monitoring interface, and meet the response time requirements of industrial real-time monitoring.

3. The SF6 gas density measurement and error compensation system based on dynamic segmented calibration according to claim 2, characterized in that: Specifically, S1-S2 are: S1-1: Signal conditioning and amplification. The analog voltage signal output by the pressure sensor is connected to the input of the instrumentation amplifier. The analog voltage signal is a weak signal in the range of 0–20mV. By setting the resistor network of the instrumentation amplifier to fix its gain at G=85.32, the amplified sampling voltage falls into the range of 0–2.5V and matches the ADC reference voltage, thereby improving the signal-to-noise ratio on the hardware side and avoiding ADC input overload. Here, G is the amplification factor of the instrumentation amplifier, and the amplified sampling voltage is denoted as Vs. S2-1. Analog-to-digital conversion and digital quantity definition: The sampling voltage Vs is converted from analog to digital under the ADC reference voltage Vref, satisfying: Vs / Vref=Nadc / NFS; where Nadc is the ADC output code value obtained from one sampling, and NFS is the upper limit of the ADC range, with NFS set to 4095. S2-2: Amplification factor back calculation and initial pressure value formation. Based on Nadc, NFS and Vref, the sampling voltage Vs is back calculated, and combined with the amplification factor G, the sampling voltage is converted into the original voltage of the sensor output terminal. Then, according to the pre-stored pressure sensor calibration curve, the original voltage is converted into the initial pressure value Praw; where Praw is the pressure value before segmented calibration is performed.

4. The SF6 gas density measurement and error compensation system based on dynamic segmented calibration according to claim 3, characterized in that: Specifically, S3 is: S3-1: Density solution model construction. The Bertie-Bridgeman equation is parameterized on the controller side, and the equation is equivalently transformed with density as the unknown quantity to form the density solution equation f(D)=0; where D is the density of SF6 gas to be determined, and f(D) is the density residual function. The residual function is obtained by substituting the initial pressure value Praw obtained in step S2 into the parameterized equation. S3-2: Iterative Update and Derivative Meaning Definition. The Newton-Leibniz iterative method is used to iteratively update the density solution equation. The iterative relationship is: D{n+1}=Dn−f(Dn) / f'(Dn); where Dn is the density value of the nth iteration, D{n+1} is the density value of the (n+1)th iteration, and f'(Dn) is the derivative of the density residual function f(D) with respect to density D at Dn. By introducing f'(Dn), the iteration direction and step size are adaptively changed with the local slope of the residual curve. S3-3: Initial value and convergence output rules. Initialize the density value D0=0 and set the convergence threshold ε. When |D{n+1}−Dn|≤ε is satisfied, the iteration result is determined to be converged and the density calculation value Dout is output. Dout is the density calculation output before the piecewise calibration is performed.

5. The SF6 gas density measurement and error compensation system based on dynamic segmented calibration according to claim 4, characterized in that: S4 includes the following sub-steps: S4-1: The purpose of setting and aligning the reference point is to set a reference pressure point Pb=0.5MPa and use this reference point as the boundary between the low-pressure section and the high-pressure section; the measured value and the theoretical value are obtained at the reference pressure point and compared. S4-2: Slope correction coefficient is introduced. The slope correction coefficient ks is calculated based on the measured value and the theoretical value. The ks is 0.981 and is used to uniformly correct the proportional error that accumulates with the increase of the range in the pressure link. S4-3: Definition of segmented intervals and parameter sets. The full pressure range is divided into a low-pressure segment ΓL and a high-pressure segment ΓH, where ΓL is the 0–0.5MPa range and ΓH is the 0.5–1MPa range. A proportional coefficient ratioL and an offset L are set for ΓL, and a proportional coefficient ratioH and an offset H are set for ΓH. Among them, ratioL and ratioH are used to characterize the segmented proportional correction strength, and offsetL and offsetH are used to characterize the segmented zero-point compensation amount. S4-4: Piecewise linear correction and output pressure definition. Piecewise linear correction is performed on the initial pressure value Praw to obtain the calibrated pressure Pcal. When Praw falls into the low-pressure range ΓL, linear correction is performed using ks, ratioL, and offsetL. When Praw falls into the high-pressure range ΓH, linear correction is performed using ks, ratioH, and offsetH. Pcal is the calibrated pressure output.

6. The SF6 gas density measurement and error compensation system based on dynamic segmented calibration according to claim 5, characterized in that: S4 further includes an adaptive calibration sub-step: S4-5: The calculation and symbol meaning of segmented error are fixed. Corresponding reference calibration points are selected in the low-pressure segment ΓL and the high-pressure segment ΓH respectively. The calibration pressure Pcal at the reference calibration point is compared with the reference pressure Pref to obtain the low-pressure segment error eL and the high-pressure segment error eH. The positive and negative signs of eL and eH are used to characterize the direction of deviation. e>0 indicates that the calibration output is higher than the reference value, and e<0 indicates that the calibration output is lower than the reference value. S4-6: Deterministic update rule based on error direction. When eL>0, ratioL and offsetL are simultaneously decreased by a preset update step size; when eL<0, ratioL and offsetL are simultaneously increased by a preset update step size; when eL=0, ratioL and offsetL remain unchanged; the same update rule is applied to ratioH and offsetH for the high-voltage section error eH; wherein the update step size is a pre-fixed positive number, so that the parameter update has a definite direction and a definite magnitude in each adaptive iteration; S4-7: Closed-loop calibration termination condition. After completing one parameter update, step S4-4 is executed again to obtain the new Pcal, and eL and eH are recalculated. When the full-range error is less than 0.1%, the adaptive calibration process is terminated and the current ratioL, offsetL, ratioH, and offsetH are fixed. The full-range error is the maximum value of the relative error at each calibration point.

7. The SF6 gas density measurement and error compensation system based on dynamic segmented calibration according to claim 6, characterized in that: S5 includes the following constraints and output controls: S5-1: Real-time linkage scheduling boundary, pressure sampling, density calculation and segment calibration are executed as a series processing link within the same measurement cycle. After completing one link processing, one measurement result is output, so that the entire process response time of sampling-processing-output is less than 10ms; where response time is defined as the time interval from the start of triggering an ADC sampling to the end of obtaining the final output result; S5-2: Density calculation accuracy constraint and output association. In the link, the solution error of the density calculation module is controlled to be less than 0.05%, and the density calculation output Dout that meets the accuracy constraint is used as the input for segment calibration, so that the density calculation result meets the basic accuracy requirements before entering the segment calibration. S5-3: Final output definition: Based on the calibration pressure Pcal, the final density measurement result Dcal is generated and output. Dcal is the density result after compensation by segmented calibration parameters, which is used for real-time monitoring and safety threshold determination of GIS equipment.

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