Mass measurement device and method based on thermal pressure-mechanical pressure balance

Abstract

The invention relates to the technical field of measurement, and provides a mass measurement device and method based on thermal pressure-mechanical pressure balance, and the device comprises a low-temperature constant-temperature measurement system which is used for obtaining a gas pressure parameter through a gas resonance characteristic, and comprises a pressure cabin; a refrigerator; the resonant cavity is arranged in the pressure cabin and is provided with a microwave antenna, the microwave antenna is connected with a network analyzer so as to realize emission and acquisition of microwave frequency, and the gas refractive index and the gas thermal pressure are calculated through the resonant frequency; the pressure measuring system is used for reversely calculating the mass to be measured based on the thermal pressure of the gas and comprises a high-purity gas cylinder; a piston pressure gauge; according to the invention, a gas refractive index pressure measuring method is adopted to obtain gas pressure, and the piston pressure gauge is communicated with the pressure chamber through the gas transmission pipeline, so that the internal gas pressures of the piston pressure gauge and the pressure chamber are equal, direct coupling of thermal pressure and mechanical pressure is realized, and high precision and reliability of a final mass measurement result are ensured.

Description

Technical Field

[0001] This invention relates to the field of measurement technology, and in particular to a mass measurement device and method based on thermal pressure-mechanical pressure balance. Background Technology

[0002] Mass, as one of the seven fundamental physical quantities, is often used to measure the magnitude of an object's inertia. It plays a crucial role in many fields such as modern economic technology, public safety, and scientific research. Its accurate measurement is key to operational efficiency and cost optimization, a cornerstone for promoting international trade and technological exchange, and fundamental to ensuring the accuracy and reliability of experimental results.

[0003] Traditional mass measurement methods, such as physical balances, primarily rely on the principles of gravity or mechanical force equilibrium to measure the absolute mass of static objects. However, this classical method has certain limitations. First, it cannot accurately detect mass changes at the microscopic scale, resulting in relatively low sensitivity. Second, its measurement accuracy is affected by external environmental conditions such as temperature and vibration. Furthermore, the accuracy of these instruments depends on precise calibration; as usage time increases or calibration deviations occur, their measurement uncertainty increases significantly.

[0004] Therefore, quality measurement needs to address the problems of high uncertainty, low sensitivity, and susceptibility to environmental influences inherent in traditional measurement methods.

[0005] In 2019, the International System of Units (SI) underwent a reform, redefining the kilogram as a unit of mass using Planck's constant, aiming to fundamentally improve the stability and accuracy of measurements. Currently, the leading international mass measurement technologies primarily include the Kibbull balance method and the X-ray crystal density method. The Kibbull balance method uses complex quantum electrodynamic experiments to balance mechanical and electrical power to determine the mass of an object. The X-ray crystal density method determines mass by calculating the number of atoms in a near-perfect single crystal (usually silicon). Both methods offer high precision and traceability; however, the measuring devices are precise and complex, have stringent requirements for materials and environment, high maintenance costs, and long measurement cycles. Summary of the Invention

[0006] This invention provides a mass measurement device and method based on thermo-pressure-mechanical pressure balance, which solves the shortcomings of traditional mass measurement methods such as low sensitivity, inability to accurately detect microscale mass changes, and susceptibility to interference from external environmental factors such as temperature and vibration, and achieves accurate mass measurement and calibration.

[0007] This invention provides a mass measurement device based on thermo-pressure-mechanical pressure balance, comprising: A low-temperature isothermal measurement system, used to obtain gas pressure parameters through gas resonance characteristics, including: Pressure chamber; A refrigeration unit is used to provide a low-temperature constant-temperature environment for the pressure chamber. A resonant cavity is set inside the pressure chamber and equipped with a microwave antenna. The microwave antenna is connected to a network analyzer to realize the transmission of microwave frequency and the acquisition of corresponding complex scattering parameters. The resonant frequency of the microwave is determined by fitting the scattering parameters, and then the refractive index and thermal pressure of the gas are calculated from the resonant frequency. A pressure measurement system, used to calculate the mass to be measured in reverse based on the gas thermal pressure, includes: High-purity gas cylinders are used to supply gas for measurement media. A piston pressure gauge is connected to the pressure chamber via a gas transmission pipeline to ensure that the gas pressure measured inside both is equal.

[0008] According to the mass measuring device based on thermo-mechanical pressure balance provided by the present invention, the piston pressure gauge includes: Vacuum enclosure; The cylinder is housed inside the vacuum chamber; A piston is provided, which can slide within the cylinder and divide the cylinder into an upper space and a lower space. A weight tray is provided in the upper space for placing weights. The weight tray is connected to the top of the piston. The lower space is connected to the gas transmission pipeline.

[0009] The mass measurement device based on thermo-mechanical pressure balance provided by the present invention further includes a vacuum pump group, which is connected to the vacuum shroud.

[0010] The mass measuring device based on thermo-mechanical pressure balance provided by the present invention further includes: A pressure control component is used to regulate gas pressure and flow rate; the outlet of the high-purity gas cylinder is connected to a gas delivery pipeline, and the pressure control component is disposed in the gas delivery pipeline, including: A pressure relief valve is used to reduce the pressure of the gas output from the high-purity gas cylinder; A shut-off valve is used to control the gas flow rate; A three-way valve is installed at the connection between the gas supply pipeline and the gas transmission pipeline. The inlet of the three-way valve is connected to the gas supply pipeline, and a pair of outlets of the three-way valve are respectively connected to the gas transmission pipeline connecting the lower space of the piston pressure gauge and the pressure chamber.

[0011] According to the mass measurement device based on thermo-pressure-mechanical pressure balance provided by the present invention, the refrigeration unit includes: The refrigeration unit head is equipped with a zero-level flange, which is connected to the open end of the zero-level radiation shield so that the zero-level radiation shield forms a first sealed space. A primary cold head is provided in the first enclosed space. The primary cold head is provided with a primary flange, which is connected to the open end of the primary radiation shield so that the primary radiation shield forms a second enclosed space. A secondary cold head is disposed in the second sealed space. The secondary cold head is provided with a secondary flange, which is connected to the open end of the secondary radiation shield, so that the secondary radiation shield forms a third sealed space. A third-level flange is provided in the third enclosed space. The third-level flange is connected to the open end of the third-level radiation shield so that the third-level radiation shield forms the pressure chamber. The pressure tube has one end connected to the gas transmission pipeline, and the other end passes through the first sealed space, the second sealed space and the third sealed space in sequence before communicating with the pressure chamber.

[0012] According to the mass measurement device based on thermo-mechanical pressure balance provided by the present invention, the resonant cavity is a quasi-spherical microwave resonant cavity, and a pair of microwave antennas are respectively disposed in the upper and lower hemispherical spaces of the quasi-spherical microwave resonant cavity and electrically connected to the network analyzer.

[0013] According to the mass measurement device based on thermo-pressure-mechanical pressure balance provided by the present invention, the resonant cavity is a quasi-spherical microwave resonant cavity, and the quasi-spherical microwave resonant cavity is located in a pressure chamber. The resonant frequency of the quasi-spherical microwave resonant cavity is used to invert the refractive index of the gas.

[0014] According to the mass measurement device based on thermo-pressure-mechanical pressure balance provided by the present invention, the pressure measurement system further includes: A temperature control chamber, which is installed outside the piston pressure gauge, is used to control the temperature of the piston pressure gauge in order to reduce the influence of room temperature on the measurement.

[0015] According to the mass measurement device based on thermo-pressure-mechanical pressure balance provided by the present invention, the gas in the high-purity gas cylinder is helium, neon, argon or nitrogen, and the gas can maintain a single gas phase state within the measured temperature and pressure range.

[0016] In a second aspect, the present invention also provides a mass measurement method based on thermal pressure-mechanical pressure balance, applied to the mass measurement device described in the first aspect, comprising the following steps: S1: Evacuate the pressure chamber of the low-temperature constant temperature measurement system, start the refrigerator to lower the temperature of the resonant cavity to the target temperature, and after the system temperature stabilizes, measure the resonant frequency of the resonant cavity under vacuum conditions. S2: Without adding weights to the weight tray of the piston pressure gauge, evacuate the vacuum hood, open the pressure control component to allow gas from the high-purity gas cylinder to flow into the lower space of the piston pressure gauge, and adjust the gas flow rate to make the piston float up and maintain a specific height. S3: After the gas enters the pressure chamber and the system temperature and piston height stabilize, the resonant frequency of the resonant cavity is acquired using a network analyzer, and the gas pressure at this time is calculated. P 1; S4: Add the weight to be measured to the weight tray, repeat steps S2-S3, collect the resonant frequency and calculate the gas pressure at this time. P 2; S5: Calculate the pressure difference Δ P = P 2- P 1. The mass of the weight to be measured is calculated in reverse based on the pressure measurement principle of the piston pressure gauge.

[0017] The mass measurement method based on thermo-mechanical pressure balance provided by the present invention further includes a relative mass measurement step: The mass of a silicon sphere traced back to Planck's constant is selected as the reference mass. m ref ; Measure the mass without and with the mass placed. m ref Place the mass to be measured m Gas refractive index at time n 1. n 2,ref , n 2; According to the formula: The mass to be measured is calculated. m By measuring the difference in refractive index, a relative mass comparison is achieved, thereby eliminating the first-order influence of temperature and piston area on mass measurement.

[0018] The mass measurement method based on thermo-mechanical pressure balance provided by the present invention further includes a mass cross-comparison step: Select a quality standard that has been calibrated using the Kibbull balance method or X-ray crystal density method; its certified quality is... m known ; Using the quality standard as the object to be measured, repeat steps S1-S5 to calculate the measured quality. m measured ; contrast m measured and m knownAnalyze the deviation Δ between the two. m = m measured - m known This enables cross-validation of quality measurement methods.

[0019] This invention provides a mass measurement device based on thermo-mechanical pressure balance, comprising a low-temperature isothermal measurement system and a pressure measurement system. The low-temperature isothermal measurement system is used to obtain thermo-pressure with high precision, while the pressure measurement system is used to convert pressure into mass. The two are coupled only through a gas transmission pipeline, eliminating the need for complex signal interaction or multi-system collaborative control, further simplifying the debugging and operation of the overall system. Mass measurement and calibration are achieved by using a piston pressure gauge as an intermediate bridge. Compared with the Kibbull balance method (which requires complex quantum electrodynamic experiments to balance mechanical and electrical power) and the X-ray crystal density method (which requires the preparation of perfect silicon crystals and counting atoms), this device does not require precision quantum components or special materials. The system structure is simpler, the operation process is more intuitive, and the development cost and maintenance difficulty of the device are significantly reduced. During mass measurement, the refractive index of the gas inside the microwave resonant cavity is first measured under the high-stability temperature environment of the cryogenic thermostat. Then, the pressure value is obtained through theoretical calculation. This value is the gas pressure in the space below the piston pressure gauge connected to the cryogenic thermostat. Based on the working principle of the piston pressure gauge, the mass of the weight on the piston, i.e., the mass to be measured under mechanical pressure, is calculated in reverse from this pressure value. Compared with traditional mechanical pressure measurement methods such as gravity sensing relied on by physical balances, this invention uses the gas refractive index pressure measurement method to obtain gas pressure, which can accurately capture micro-pressure changes and achieve high-precision measurement. By connecting the piston pressure gauge and the pressure chamber through a gas transmission pipeline, the gas pressure inside the two is ensured to be equal, realizing the direct coupling of thermal pressure (cryo-temperature thermostat system) and mechanical pressure (piston pressure gauge), avoiding mass calculation errors caused by pressure transmission deviations, and ensuring the high accuracy and reliability of the final mass measurement result. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in this 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 some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0021] Figure 1 This is a schematic diagram of a mass measurement device based on thermal pressure-mechanical pressure balance provided in an embodiment of the present invention.

[0022] Figure 2This is a schematic flowchart of a mass measurement method based on thermal pressure-mechanical pressure balance provided by an embodiment of the present invention.

[0023] Figure label: 1. Pressure chamber; 2. Resonant cavity; 3. Microwave antenna; 4. Network analyzer; 5. High-purity gas cylinder; 6. Piston pressure gauge; 7. Gas transmission pipeline; 8. Gas delivery pipeline; 9. Vacuum hood; 10. Cylinder; 11. Piston; 12. Weight tray; 13. Weight; 14. Vacuum pump assembly; 15. Pressure relief valve; 16. Shut-off valve; 17. Three-way valve; 18. Refrigeration unit head; 19. Primary cold head; 20. Secondary cold head; 21. Zero-level radiation shield; 22. Primary radiation shield; 23. Secondary radiation shield; 24. Tertiary radiation shield; 25. Pressure pipe; 26. Zero-level flange; 27. Primary flange; 28. Secondary flange; 29. ​​Tertiary flange. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0025] The following is combined with Figure 1-Figure 2 This invention describes a mass measurement device and method based on thermo-pressure-mechanical pressure balance.

[0026] This invention provides a mass measurement device based on thermal pressure-mechanical pressure balance, comprising: a low-temperature constant temperature measurement system and a pressure measurement system.

[0027] The low-temperature constant temperature measurement system is used to accurately obtain gas pressure parameters through gas resonance characteristics. The low-temperature constant temperature measurement system includes a pressure chamber 1, a refrigerator and a resonant cavity 2. The refrigerator is used to provide a low-temperature constant temperature environment for the pressure chamber 1. The resonant cavity 2 is set inside the pressure chamber 1 and is equipped with a microwave antenna 3. The microwave antenna 3 is connected to a network analyzer 4 to realize the transmission of microwave frequency and the acquisition of corresponding complex scattering parameters. The resonant frequency of the microwave is determined by fitting the scattering parameters, and then the gas refractive index and gas thermal pressure are calculated from the resonant frequency.

[0028] The measurement of microwave resonant frequency involves transmitting a series of discrete microwave frequencies f0 using a network analyzer 4 and collecting their corresponding complex scattering parameters. The microwave resonant frequency (referred to as resonant frequency) f is then determined by fitting the scattering parameters, and the gas refractive index and gas thermal pressure are calculated from the resonant frequency.

[0029] This setup, by providing a low-temperature, constant-temperature environment for pressure chamber 1 through a refrigeration unit, eliminates the influence of environmental factors such as room temperature fluctuations and thermal radiation on the physical properties of the gas from the source. It avoids errors caused by environmental interference in traditional mass measurement methods, such as the susceptibility of physical balance measurements to temperature-induced expansion and contraction of components. The resonant cavity 2 achieves non-contact resonant frequency acquisition via microwave antenna 3 and network analyzer 4, eliminating the need for direct contact with the gas or precision components within pressure chamber 1. This avoids physical disturbances to the gas state in resonant cavity 2 during measurement and also prevents the impact of component wear on measurement accuracy.

[0030] The pressure measurement system is used to calculate the mass to be measured based on the gas thermal pressure. It includes a high-purity gas cylinder 5 and a piston pressure gauge 6. The high-purity gas cylinder 5 is used to provide the measuring medium gas, such as helium, to prevent the gas from liquefying during the experiment at low temperature. The lower space of the piston pressure gauge 6 is connected to the pressure chamber 1 through a gas transmission pipeline 7 to ensure that the gas pressure measured inside the two are equal.

[0031] As can be seen from the above scheme, the low-temperature constant temperature measurement system of the present invention is used to obtain thermal pressure with high precision, and the pressure measurement system is used to convert pressure and mass. The two are coupled only through the gas transmission pipeline 7, without the need for complex signal interaction or multi-system collaborative control, which further simplifies the debugging and operation difficulty of the overall system. The piston pressure gauge 6 is used as an intermediate bridge to realize the measurement and calibration of mass. Compared with the Kibbull balance method and X-ray crystal density method, it does not require precision quantum components or special materials. The system structure is simpler and the operation process is more intuitive, which significantly reduces the development cost and maintenance difficulty of the device.

[0032] When performing mass measurement, the refractive index of the gas inside the microwave resonant cavity 2 is first measured under the high stable temperature environment of the cryogenic thermostat. Then, the pressure value is obtained through theoretical calculation. This value is the gas pressure in the space below the piston pressure gauge 6 connected to the cryogenic thermostat. Based on the working principle of the piston pressure gauge 6, the mass of the weight 13 on the piston 11, i.e., the mass to be measured under mechanical pressure, is calculated in reverse using this pressure value. Compared with traditional mechanical pressure measurement methods such as gravity sensing relied on physical balances, this invention uses the gas refractive index pressure measurement method to obtain gas pressure, which can accurately capture micro-pressure changes and achieve high-precision measurement. By connecting the piston pressure gauge 6 and the pressure chamber 1 through the gas transmission pipeline 7, the gas pressure inside the two is ensured to be equal, realizing the direct coupling of thermal pressure (from the cryogenic thermostat system) and mechanical pressure (from the piston pressure gauge 6). This avoids the mass calculation error caused by pressure transmission deviation and ensures the high accuracy and reliability of the final mass measurement result.

[0033] The piston pressure gauge 6 of the present invention includes: a vacuum chamber 9, a cylinder 10, and a piston 11. The cylinder 10 is disposed inside the vacuum chamber 9, and the influence of external atmospheric pressure fluctuations can be eliminated by evacuating the inside of the vacuum chamber 9. The piston 11 can slide inside the cylinder 10 and divide the cylinder 10 into an upper space and a lower space. A weight tray 12 is disposed in the upper space for placing weights 13. The weight tray 12 is connected to the top of the piston 11. The lower space is connected to a gas transmission pipeline 7.

[0034] The piston 11 slides within the cylinder 10, dividing it into an upper space and a lower space. The upper space is directly affected by the gravity of the weight 13 without any gas pressure interference. The lower space is connected only to the gas transmission pipeline 7, receiving the gas thermal pressure from the cryogenic constant temperature system. This avoids pressure crosstalk caused by the mixing of gases in the upper and lower spaces. Through the force balance of the piston 11, the gravity of the upper weight 13 is transferred to the gas in the lower space without any lateral force loss. This structure ensures that the magnitude of the mechanical pressure is determined only by the mass of the weight 13, the acceleration due to gravity, and the effective area of ​​the piston 11, and ensures that the gas pressure in the lower space is completely equal to the thermal pressure of the cryogenic constant temperature system pressure chamber 1.

[0035] This configuration avoids interference from external pressure on the force balance of the piston 11 by setting up a vacuum cover 9. At the same time, the vacuum cover 9 can also prevent external air dust from entering the cylinder 10, preventing impurities from adhering to the inner wall of the piston 11 or cylinder 10 and affecting the smoothness of sliding. The vacuum environment can also reduce local thermal disturbance caused by air convection, indirectly ensuring the temperature stability of the piston 11 and cylinder 10, and further reducing system errors.

[0036] Furthermore, it also includes a vacuum pump assembly 14, which is connected to the vacuum shroud 9 and is used to evacuate the inside of the vacuum shroud 9 to eliminate residual pressure interference in the upper space of the piston 11.

[0037] In addition, a vacuum pump set (not shown in the figure) is also provided to evacuate the pressure chamber 1, the first sealed space, the second sealed space and the third sealed space.

[0038] In a further embodiment, the outlet of the high-purity gas cylinder 5 is connected to a gas delivery pipeline 8, and a pressure control component is provided on the gas delivery pipeline 8. The pressure control component is used to regulate the gas pressure and flow rate, including: a pressure relief valve 15, a shut-off valve 16, and a three-way valve 17. The pressure relief valve 15 is used to reduce the pressure of the gas output from the high-purity gas cylinder 5; the shut-off valve 16 is used to control the gas flow rate; the three-way valve 17 is located at the connection between the gas delivery pipeline 8 and the gas transmission pipeline 7. The inlet of the three-way valve 17 is connected to the gas delivery pipeline 8, and a pair of outlets of the three-way valve 17 are respectively connected to the lower space of the piston pressure gauge 6 and the gas transmission pipeline 7 of the pressure chamber 1.

[0039] This setup addresses the issue that, since the gas in the high-purity gas cylinder 5 is typically stored at high pressure, such as high-pressure helium, direct introduction into the device would impact precision components like pipelines and piston pressure gauge 6, and could even compromise the airtightness of the pressure chamber 1. By pre-pressurizing the high-pressure gas output from the high-purity gas cylinder 5, the gas pressure is reduced to a measurement pressure range suitable for the device, such as meeting the precision pressure measurement requirements of the low-temperature constant-temperature system pressure chamber 1. This avoids the physical impact of high-pressure airflow on components like the gas transmission pipeline 7, piston 11, and resonant cavity 2, extending the service life of precision components. By fine-tuning the gas flow rate through the shut-off valve 16, it prevents the piston 11 from floating excessively and causing a sudden pressure surge due to excessive gas flow, or prevents the piston 11 from stabilizing at the target height due to excessively slow flow. Ultimately, this ensures that the gas pressure in the space below the piston 11 and the pressure chamber 1 remains stable at the set value, providing a stable pressure environment for resonant frequency acquisition.

[0040] In this embodiment, the refrigeration unit includes: a refrigeration unit head 18, a primary cold head 19, and a secondary cold head 20. The refrigeration unit head 18 is provided with a zero-level flange 26, which is connected to the open end of a zero-level radiation shield 21, so that the zero-level radiation shield 21 forms a first sealed space. The primary cold head 19 is disposed in the first sealed space and is provided with a primary flange 27, which is connected to the open end of a primary radiation shield 22, so that the primary radiation shield 22 forms a second sealed space. The secondary cold head 20 is disposed in... The second sealed space includes a secondary flange 28 on the secondary cold head 20, which is connected to the open end of the secondary radiation shield 23, so that the secondary radiation shield 23 forms a third sealed space; a tertiary flange 29 is located in the third sealed space and is connected to the open end of the tertiary radiation shield 24, so that the tertiary radiation shield 24 forms a pressure chamber 1; one end of the pressure pipe 25 is connected to the gas transmission pipeline 7, and the other end passes through the first sealed space, the second sealed space and the third sealed space in sequence before communicating with the pressure chamber 1.

[0041] like Figure 1As shown, the low-temperature constant-temperature measurement system is equipped with four layers of radiation shields and four levels of flanges. The four layers of radiation shields are used to reduce radiative heat dissipation and weaken the influence of room temperature on internal pressure measurement. The four levels of flanges are used to couple with the radiation shields to form a sealed space. Among them, the zero-level flange 26 is connected to the refrigeration unit head 18, the first-level flange 27 is connected to the first-level cold head 19 of the refrigeration unit via a flexible thermal connection, the second-level flange 28 is connected to the second-level cold head 20 of the refrigeration unit via a flexible thermal connection, and the pressure chamber 1 is located below the third-level flange 29. The zero-level radiation shield 21 is made of stainless steel or aluminum and is bolted to the zero-level flange 26, serving as the outermost shield of the entire device. The first-level radiation shield 22, the second-level radiation shield 23, and the third-level radiation shield 24 are all made of copper or oxygen-free copper and are bolted to the first-level flange 27, the second-level flange 28, and the third-level flange 29, respectively. Furthermore, pressure pipes 25 can be installed on each level of flange to connect with the pressure measurement system composed of an external piston pressure gauge 6, ensuring that the internal pressures measured by both are equal.

[0042] In some embodiments, the resonant cavity 2 is a quasi-spherical microwave resonant cavity, and a pair of microwave antennas 3 are respectively disposed in the upper and lower hemispherical spaces of the quasi-spherical microwave resonant cavity and electrically connected to the network analyzer 4.

[0043] Preferably, the pressure measurement system also includes a temperature control chamber, which uses semiconductor refrigeration and is enclosed outside the piston pressure gauge 6 to control the temperature of the piston pressure gauge 6, thereby reducing the influence of room temperature on the measurement.

[0044] In some alternative embodiments, in addition to helium, the gas in the high-purity gas cylinder 5 may also be neon, argon or nitrogen, and the gas can maintain a single gas phase state within the measured temperature and pressure range.

[0045] In other words, based on the set operating temperature range, neon, argon, nitrogen, etc. are selected to ensure that the working medium remains in a single gaseous state throughout the temperature and pressure range of the entire experiment, avoiding liquefaction or solidification.

[0046] In some alternative embodiments, the cryogenic constant temperature measurement system is a room temperature optical Fabry-Perot cavity measurement system, and the optical Fabry-Perot cavity and the piston pressure gauge 6 are both placed in the same constant temperature chamber. The gas refractive index is inverted by the change in the resonant frequency or transmission spectrum of the optical Fabry-Perot cavity.

[0047] This configuration, with the optical Fabry-Perot cavity and piston pressure gauge 6 residing in the same constant temperature chamber, avoids temperature inconsistencies caused by their separate temperature control systems. The shared chamber ensures identical ambient temperatures for both, guaranteeing that the thermal pressure remains equal to the pressure in the space beneath piston 11, thus ensuring accurate pressure balance. Furthermore, the measurement process of the optical Fabry-Perot cavity is non-contact, interacting with the gas within the cavity solely through incident / exit optical signals, eliminating the need for physical contact and further enhancing the long-term reliability of the device.

[0048] It should be noted that the optical Fabry-Perot cavity is based on the principle of optical resonance, utilizing the light interference between two parallel high-reflectivity mirrors to form resonance characteristics. Compared with the aforementioned spherical microwave resonant cavity 2, the optical Fabry-Perot cavity is more sensitive to changes in the refractive index of the gas inside the cavity. Small fluctuations in the gas refractive index (corresponding to small changes in thermal pressure) will directly cause a shift in the resonant frequency or a shift in the peak value of the transmission spectrum. Moreover, the resolution (such as wavelength accuracy) of optical signals is much higher than that of microwave signals, which can capture more microscopic differences in refractive index. In this way, through the inversion logic of refractive index → ​​thermal pressure, the uncertainty of thermal pressure measurement can be reduced, providing more accurate basic pressure parameters for the subsequent inverse calculation of mechanical pressure → mass.

[0049] Furthermore, the optical Fabry-Perot cavity can be adapted to gas refractive index measurements in different pressure ranges by adjusting the mirror spacing and incident light wavelength. For example, the optical interference signal can still be stably identified under low pressure, avoiding the measurement blind zone caused by signal attenuation in the microwave resonant cavity 2 under low pressure.

[0050] Reference Figure 2 This invention also provides a mass measurement method based on thermal pressure-mechanical pressure balance, applied to the aforementioned mass measurement device, comprising the following steps: S1: Evacuate the pressure chamber 1 of the low-temperature constant temperature measurement system, start the refrigerator to lower the temperature of the resonant cavity 2 to the target temperature, and after the system temperature stabilizes, measure the resonant frequency of the resonant cavity 2 under vacuum conditions. S2: Without adding weights 13 to the weight tray 12 of the piston pressure gauge 6, evacuate the vacuum hood 9, open the pressure control component to allow the gas in the high-purity gas cylinder 5 to flow into the lower space of the piston pressure gauge 6, and adjust the gas flow rate to make the piston 11 float up and maintain a specific height. S3: After the gas enters pressure chamber 1 and the system temperature and piston height 11 stabilize, the resonant frequency of the quasi-spherical microwave resonant cavity is acquired by network analyzer 4, and the gas pressure at this time is calculated. P 1; S4: Add the weight to be measured 13 to the weight tray 12, repeat steps S2-S3, collect the resonant frequency and calculate the gas pressure at this time. P 2; S5: Calculate the pressure difference ΔP = P 2- P 1. The mass of the weight 13 to be measured is calculated in reverse according to the pressure measurement principle of the piston pressure gauge 6.

[0051] Compared with the prior art, the present invention has the following advantages: 1. This invention uses a classic piston pressure gauge 6 as an intermediate bridge to achieve mass measurement and calibration. Compared with complex quantum metrology methods such as the Kibbull balance, it greatly simplifies the complexity of the system and the operation process, and reduces the technical threshold and the cost of device development.

[0052] 2. This invention uses the internationally advanced gas refractive index pressure measurement method to obtain gas pressure. This method itself has high accuracy, thus ensuring the high precision and reliability of the final mass measurement results.

[0053] 3. The pressure measurement of this invention is performed in the highly stable temperature environment of a cryogenic thermostat. First, the highly stable low-temperature environment can suppress noise caused by thermal fluctuations at the source, reducing measurement interference. Second, the measurement based on microwave resonant frequency is non-contact, avoiding physical interference or damage to precision components during the measurement process. This method of mass measurement through calculation rather than direct weighing fundamentally ensures the stability and repeatability of the measurement.

[0054] 4. This invention provides a novel approach to quality measurement and traceability, which can be used to compare with existing quality measurement methods and conduct cross-validation of different methods. This is of great significance for ensuring the consistency and stability of global quality values ​​and for promoting the process of quality measurement and comparison under the new International System of Units.

[0055] The following describes three implementation schemes in detail: Example 1 is an absolute mass measurement scheme, which is the foundation of the entire mass measurement technology. It aims to establish a direct correspondence between physical quantities and mass values ​​and is suitable for determining basic mass values.

[0056] Example 2 is a relative mass measurement scheme, which is a more accurate measurement method. By introducing a high-precision reference mass, such as the mass of a silicon sphere traced back to Planck's constant, this method can eliminate the first-order influence of the two main interference factors, temperature and the effective area of ​​piston 11, on the measurement results, thereby significantly improving the measurement accuracy and stability.

[0057] Example 3 is a quality cross-comparison scheme, which replaces the conventional weight 13 with a weight 13 calibrated using a benchmark measurement method, so that the measurement results can be directly cross-compared with other internationally leading quality traceability methods to ensure its reliability.

[0058] Example 1 When using the above-mentioned mass measurement device based on thermal pressure-mechanical pressure balance for mass measurement, since the weight tray 12 and piston 11 themselves have mass, the mass calculated after directly measuring the gas pressure is not the mass of the weight 13 itself. Therefore, two measurements are required: one without adding the weight 13 and one with adding the weight 13.

[0059] The specific steps include: Step S11: Evacuate the sealed pressure chamber 1, which consists of the level 3 radiation shield 24 and the level 3 flange 29, until the vacuum level reaches 10. -4 -10 -5 When the Pa level is reached, the refrigeration unit 18 is turned on to cool down the low-temperature constant temperature measurement system. Step S12: When the temperature of the quasi-spherical microwave resonant cavity drops to the target temperature, high-stability temperature control is performed through a low-temperature constant temperature measurement system, and the microwave resonant frequency is measured under vacuum conditions. Step S13: No weights 13 are added to the weight tray 12 of the piston pressure gauge 6, and the vacuum pump group 14 evacuates the space inside the vacuum chamber 9. Step S14: Open the pressure relief valve 15 and the shut-off valve 16. The gas in the high-purity gas cylinder 5 is depressurized through the pressure relief valve 15 and flows into the lower space of the piston pressure gauge 6 through the gas transmission pipeline 7. Step S15: Control the gas flow into the piston pressure gauge 6 through the shut-off valve 16, so that the piston 11 floats up in the cylinder 10 and is maintained at a certain height. Step S16: The gas enters the pressure chamber 1 of the low-temperature constant temperature measurement system. The low-temperature constant temperature measurement system controls the temperature of the gas in the three-level radiation shield 24 through its own temperature control system to keep its temperature at a certain level. Step S17: After the height of piston 11 and the gas temperature inside pressure chamber 1 stabilize, the resonant frequency under pressurized conditions inside the quasi-spherical microwave resonant cavity is acquired by network analyzer 4. Then, the gas pressure inside pressure chamber 1, i.e., the gas pressure below piston pressure gauge 6, is calculated based on the resonant frequency. P 1; Step S18: Add weight 13 to piston pressure gauge 6 and repeat the above operation. After the height of piston 11 and the gas temperature in pressure chamber 1 stabilize, the resonant frequency in the quasi-spherical microwave resonant cavity is collected again by network analyzer 4. Then, the gas pressure in pressure chamber 1, i.e., the gas pressure at the bottom of piston pressure gauge 6, is calculated based on the resonant frequency. P 2; Step S19: Combine the gas pressures obtained from the two calculations. P 1 and PBy subtracting the two pressure measurements from piston pressure gauge 6, the difference can be obtained. Then, based on the pressure measurement principle of piston pressure gauge 6, the mass of the added weight 13 can be calculated in reverse, and the mass of weight 13 can be calibrated.

[0060] The following is a brief explanation of the relevant calculation ideas and methods: For piston pressure gauge 6, the measured gas pressure P A It can be calculated using formula (1).

[0061] in, A T,P This represents the effective area of ​​piston 11, in meters (m²). 2 ; M Indicates the load mass, in kg; P HA The static pressure correction amount corresponds to the height difference between the reference position of piston pressure gauge 6 and the center position of resonant cavity 2, in Pa. P vac This indicates the residual pressure above piston 11, in Pa. g This represents the local gravitational acceleration, with units of m / s². 2 If the pressure is below 1 kPa, the effect of thermal molecular pressure difference must also be considered; however, the relevant expressions are not shown in the formulas presented in this paper.

[0062] Among them, the effective area of ​​piston 11 A T,P Using the measured area under a specific temperature and pressure as a reference, the actual effective area near the specific state is obtained by correcting for expansion and compressive deformation, as shown in formula (2).

[0063] in, A ( T r , p r For piston 11 at temperature ) T r The pressure is p r The effective area at that time, in m 2 ; T This represents the actual temperature of piston 11, in Kelvin (K). α p and α c , respectively, are the linear thermal expansion coefficients of piston 11 and cylinder 10, used to correct for the effective area change of piston 11 caused by thermal expansion, 1 / K; l1 / Pa is the elastic deformation coefficient of the piston 11-cylinder 10 assembly.

[0064] Without adding weight 13, the pressure of piston pressure gauge 6 is calculated using formula (3).

[0065] After adding weight 13, the pressure of piston pressure gauge 6 is calculated using formula (4).

[0066] Since the same vacuum pump group 14 is used, it can be considered that... P vac,1 = P vac,2 Then the mass of weight 13 can be obtained by formula (5).

[0067] Among them, the weights are 13 in mass. m = M 2- M 1, P HA,2 and P HA,1 It can be calculated using the static pressure correction formula.

[0068] For low-temperature isothermal measurement systems P 1 and P 2 can be calculated from the perspective of thermal pressure, and the specific calculation method is as follows.

[0069] First, the gas refractive index is calculated from the experimental measurement results, as shown in formula (6).

[0070] in, f It is the resonant frequency, and the unit is Hz; k T ( T ) is the resonator at temperature T The isothermal compressibility coefficient at 1 / Pa; n The value is the refractive index of the gas; the subscript exp indicates the result calculated based on experimental measurements.

[0071] Secondly, the refractive index of the gas is calculated using a theoretical model.

[0072] The refractive index can be determined based on the relative permittivity of the gas. e r and relative permeability m r It is calculated using formula (7).

[0073] In this context, the subscript calc indicates the result calculated by the theoretical model. e r and m r All are related to the molar density of the gaseous medium r The relevant equations can be obtained from the Clausius-Mossotti equations, as shown in equations (8) and (9).

[0074] in, A ε and A μ These are the molar polarizability and molar magnetic susceptibility at the zero density limit of the gas (ρ=0), also known as the first dielectric virial coefficient and the first magnetic susceptibility virial coefficient, respectively. 3 / mol; B ε and C ε These are the second and third dielectric virial coefficients, respectively, with units of m. 6 / mol 2 and m 9 / mol 3 .

[0075] The simultaneous equations (7)-(9) can eliminate e r and m r Thus establish n calc and r direct contact, n calc and r The approximate relationship is given by formula (10).

[0076] Among them, molar density r It's pressure p and temperature T The function is expressed in kg / mol, and its calculation formula is shown in formula (11).

[0077] in, B ρ , C ρ ,and D ρ These are the second, third, and fourth density virial coefficients, respectively, with units of m. 3 / mol, m 6 / mol 2 m 9 / mol 3 .

[0078] Combining equations (7)-(11), omitting higher-order terms, the thermal pressure can be obtained. p The first-order approximation relation is (12).

[0079] In actual calculations, thermal pressure is calculated using formulas (7)-(11). Here, we will only use a first-order approximation to explain the measurement approach and method.

[0080] Finally, maintain the temperature. T Unchanged, under pressure p Make assumptions about the values ​​and solve the system of equations. n exp and n calc Perform iterative solutions, calculating multiple times until... n exp and n calc If the two are approximately equal, then the assumed pressure value at this point is the gas pressure value measured by the low-temperature constant-temperature measurement system. Repeating the above calculation before and after adding weight 13 will yield the result. P 1 and P 2, and you can get P 2 and P The difference of 1 is shown in formula (13).

[0081] Combined with formula (5), the quality result can be obtained as shown in formulas (14) and (15).

[0082] in, The temperature of the gas inside pressure chamber 1 is K, which remains constant during the experiment. It can be the triple point temperature of water, the triple point temperature of neon, or other thermodynamic temperatures, and can be measured by other temperature measurement methods such as acoustic methods and dielectric constant methods.

[0083] In the experiment, the reference position of piston pressure gauge 6 can be kept at the same height as the center position of resonant cavity 2, thereby reducing the influence of static pressure correction on the measurement. P HA ≈0; This is particularly applicable to situations where the thermal pressure is determined by optical resonators such as optical Fabry-Perot cavities at room temperature.

[0084] Example 2 This solution aims to compare with a reference standard of known quality. m ref Comparison is performed to achieve the quality of the test. mIt enables higher precision measurements. Its core advantage lies in its ability to eliminate or significantly reduce systematic errors introduced by uncertainties in the effective area of ​​piston 11 and gas temperature.

[0085] This method requires three consecutive measurement operations to obtain the gas refractive index under three different conditions.

[0086] First, following the complete experimental procedures in Example 1, without placing any mass (weight 13 or reference object) on the weight tray 12, the gas refractive index was measured after stabilizing the system. n 1; Then, a silicon sphere mass carrier traceable to Planck's constant is placed on the weight tray 12 as a reference mass. m ref (Alternatively, weights 13 calibrated using other mass measurement methods can be used.) Repeat the experimental steps of Example 1, and measure the gas refractive index after the system stabilizes. n 2,ref ; Then, place a weight of mass on the weight tray 12. m Using the test weight 13, repeat the experimental steps of Example 1, and measure the gas refractive index after the system stabilizes. n 2; Finally, the reference mass can be obtained according to formula (15). m ref And the mass of the 13 weights to be tested m As shown in formulas (16) and (17) respectively.

[0087] Where the reference position of piston pressure gauge 6 is kept at the same height as the center position of resonant cavity 2, then Δ P HA ≈0; The temperature of piston 11 was measured in two experiments. T r The pressure difference correction is approximately 1. A ( T r , p r They are approximately equal. Solving equations 16 and 17 simultaneously... m and m ref The first-order approximate ratio is shown in formula (18).

[0088] Known reference mass m ref By measuring the microwave resonant frequency under different experimental conditions, and thus obtaining the gas refractive index under those conditions, the mass to be measured can be determined. mThe calculation formula is shown in formula (19).

[0089] This formula indicates that the mass to be measured... m Depends only on reference quality m ref The ratio of the refractive index to the three measurements. This comparative measurement mode effectively eliminates the dependence on physical quantities that are difficult to measure precisely, such as the effective area of ​​piston 11 and the absolute temperature of the gas, thereby significantly improving the final accuracy and reliability of mass measurement.

[0090] Example 3 The purpose of this scheme is to verify the accuracy of the absolute mass measurement method established in Example 1. By measuring a standard with an internationally recognized mass value, it ensures that the measurement results of this invention can be traced back to the International System of Units (SI) and are consistent with the mass measurement results obtained by other methods.

[0091] First, a quality standard whose quality value has been precisely calibrated using other benchmark measurement methods such as the Kibbull balance method or X-ray crystal density method is selected. The example of a silicon sphere mass carrier directly traceable to Planck's constant is used, assuming its known certified quality is... m known ; Using the quality standard as the test object, the experimental operation steps and theoretical calculation process in Example 1 were repeated to obtain the pressure measured before and after placing the quality standard. P 1 and P 2; According to the calculation formula in Example 1, based on the measured pressure difference Δ P = P 2- P Based on parameters such as the effective area of ​​piston 11 and gravitational acceleration, the mass value of the standard is calculated, and this calculation result is recorded as... m measured ; Finally, the mass value obtained from this method will be measured and calculated. m measured Certification quality value of the standard m known A direct comparison is performed to analyze the deviation between the two: Δ m = m measured - m known ; This cross-validation ensures the reliability of the quality measurement method proposed in this invention, achieving consistency and stability with the global quality measurement system.

[0092] It should be noted that the operating temperature of the low-temperature isothermal measurement system in this mass measurement method can be set not only at the triple point of water or the triple point of neon. In principle, any low-temperature point that can be reproduced, measured, and stably controlled with high precision can be considered. The key to selection is ensuring high temperature stability, rather than its specific value, to meet the core requirements of precision pressure measurement.

[0093] The mass measuring device of this invention is essentially a high-precision pressure gauge or gas density meter based on fundamental physical principles. Therefore, in addition to its use for mass measurement, it can also be used directly as a metrological standard for absolute pressure or gas density, or for fundamental physics research, such as for the precise measurement of physical properties of gases, such as molar polarizability.

[0094] Furthermore, the method used to measure gas pressure in this mass measurement method is not limited to obtaining it by measuring the gas refractive index. It can also employ acoustic methods or dielectric constant methods, obtaining the gas pressure value by obtaining the sound velocity or dielectric constant and then performing theoretical calculations.

[0095] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A mass measuring device based on thermo-pressure-mechanical pressure balance, characterized in that, include: A low-temperature isothermal measurement system, used to obtain gas pressure parameters through gas resonance characteristics, including: Pressure chamber (1); A refrigeration unit is used to provide a low-temperature constant-temperature environment for the pressure chamber (1); The resonant cavity (2) is set inside the pressure chamber (1) and equipped with a microwave antenna (3). The microwave antenna (3) is connected to a network analyzer (4) to realize the transmission of microwave frequency and the acquisition of corresponding complex scattering parameters. The resonant frequency of the microwave is determined by fitting the scattering parameters, and then the gas refractive index and gas thermal pressure are calculated from the resonant frequency. A pressure measurement system, used to calculate the mass to be measured in reverse based on the gas thermal pressure, includes: High-purity gas cylinder (5) is used to provide the gas for measuring the medium; A piston pressure gauge (6) is connected to the pressure chamber (1) via a gas transmission pipeline (7) to ensure that the gas pressure measured inside the two chambers is equal.

2. The mass measuring device based on thermo-pressure-mechanical pressure balance according to claim 1, characterized in that, The piston pressure gauge (6) includes: Vacuum shroud (9); Cylinder (10) is disposed inside the vacuum shroud (9); The piston (11) is able to slide inside the cylinder (10) and divide the cylinder (10) into an upper space and a lower space. The upper space is provided with a weight tray (12) for placing weights (13). The weight tray (12) is connected to the top of the piston (11). The lower space is connected to the gas transmission pipeline (7).

3. The mass measuring device based on thermo-pressure-mechanical pressure balance according to claim 2, characterized in that, It also includes a vacuum pump assembly (14), which is connected to the vacuum shroud (9).

4. The mass measuring device based on thermo-pressure-mechanical pressure balance according to claim 2, characterized in that, Also includes: Pressure control components are used to regulate gas pressure and flow rate; The outlet of the high-purity gas cylinder (5) is connected to a gas delivery pipeline (8), and the pressure control component is disposed in the gas delivery pipeline (8), including: Pressure relief valve (15) is used to reduce the pressure of the gas output from the high-purity gas cylinder (5); The shut-off valve (16) is used to control the gas flow rate; A three-way valve (17) is installed at the connection between the gas supply pipeline (8) and the gas transmission pipeline (7). The inlet of the three-way valve (17) is connected to the gas supply pipeline (8), and a pair of outlets of the three-way valve (17) are respectively connected to the gas transmission pipeline (7) connecting the lower space of the piston pressure gauge (6) and the pressure chamber (1).

5. The mass measuring device based on thermo-pressure-mechanical pressure balance according to claim 2, characterized in that, The refrigeration unit includes: The refrigeration unit head (18) is provided with a zero-level flange (26), which is connected to the open end of the zero-level radiation shield (21) so that the zero-level radiation shield (21) forms a first sealed space. A primary cold head (19) is provided in the first sealed space. The primary cold head (19) is provided with a primary flange (27). The primary flange (27) is connected to the open end of the primary radiation shield (22) so that the primary radiation shield (22) forms a second sealed space. A secondary cold head (20) is provided in the second sealed space. The secondary cold head (20) is provided with a secondary flange (28). The secondary flange (28) is connected to the open end of the secondary radiation shield (23) so that the secondary radiation shield (23) forms a third sealed space. A third-level flange (29) is provided in the third enclosed space. The third-level flange (29) is connected to the open end of the third-level radiation shield (24) so ​​that the third-level radiation shield (24) forms the pressure chamber (1). The pressure pipe (25) is connected at one end to the gas transmission pipeline (7), and at the other end passes through the first sealed space, the second sealed space and the third sealed space in sequence before communicating with the pressure chamber (1).

6. The mass measuring device based on thermo-pressure-mechanical pressure balance according to claim 5, characterized in that, The resonant cavity (2) is a quasi-spherical microwave resonant cavity. A pair of microwave antennas (3) are respectively located in the upper and lower hemispherical spaces of the quasi-spherical microwave resonant cavity and are electrically connected to the network analyzer (4).

7. The mass measuring device based on thermo-mechanical pressure balance according to claim 5, characterized in that, The resonant cavity (2) is a quasi-spherical microwave resonant cavity, and the quasi-spherical microwave resonant cavity is placed in the pressure chamber (1). The refractive index of the gas is inverted by the change of the resonant frequency of the quasi-spherical microwave resonant cavity.

8. The mass measuring device based on thermo-pressure-mechanical pressure balance according to claim 5, characterized in that, The pressure measurement system also includes: A temperature control chamber is installed outside the piston pressure gauge (6) to control the temperature of the piston pressure gauge (6) in order to reduce the influence of room temperature on the measurement.

9. The mass measuring device based on thermo-pressure-mechanical pressure balance according to claim 2, characterized in that, The gas in the high-purity gas cylinder (5) is helium, neon, argon or nitrogen, and the gas can maintain a single gas phase state within the measured temperature and pressure range.

10. A mass measurement method based on thermo-pressure-mechanical pressure balance, characterized in that, The mass measuring device according to any one of claims 2-9 comprises the following steps: S1: Evacuate the pressure chamber (1) of the low-temperature constant temperature measurement system, start the refrigerator to lower the temperature of the resonant cavity (2) to the target temperature, and after the system temperature stabilizes, measure the resonant frequency of the resonant cavity (2) under vacuum conditions. S2: Without adding weights (13) to the weight tray (12) of the piston pressure gauge (6), evacuate the vacuum hood (9), open the pressure control component to allow the gas in the high-purity gas cylinder (5) to flow into the lower space of the piston pressure gauge (6), adjust the gas flow rate to make the piston (11) float up and maintain a specific height; S3: After the gas enters the pressure chamber (1) and the system temperature and piston (11) height stabilize, the resonant frequency of the resonant cavity (2) is collected by the network analyzer (4), and the gas pressure at this time is calculated. P 1; S4: Add the weight to be measured (13) to the weight tray (12), repeat steps S2-S3, collect the resonant frequency and calculate the gas pressure at this time. P 2; S5: Calculate the pressure difference Δ P = P 2- P 1. The mass of the weight (13) to be measured is calculated in reverse according to the pressure measurement principle of the piston pressure gauge (6).

11. The mass measurement method based on thermo-pressure-mechanical pressure balance according to claim 10, characterized in that, It also includes a relative mass measurement step: The mass of a silicon sphere traced back to Planck's constant is selected as the reference mass. m ref ; Measure the mass without and with the mass placed. m ref Place the mass to be measured m Gas refractive index at time n 1. n 2,ref , n 2; According to the formula: The mass to be measured is calculated. m The relative mass comparison is achieved by measuring the difference in refractive index, thereby eliminating the first-order influence of temperature and piston (11) area on mass measurement.

12. The mass measurement method based on thermo-mechanical pressure balance according to claim 10, characterized in that, It also includes a quality cross-comparison step: Select a quality standard that has been calibrated using the Kibbull balance method or X-ray crystal density method; its certified quality is... m known ; Using the quality standard as the object to be measured, repeat steps S1-S5 to calculate the measured quality. m measured ; contrast m measured and m known Analyze the deviation Δ between the two. m = m measured - m known This enables cross-validation of quality measurement methods.

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