Low temperature thermometer calibration device and cooling control method

Abstract

This invention relates to the field of cryogenic metrology technology, and provides a cryogenic thermometer calibration device and a cooling control method. The device includes a vacuum chamber, a pre-cooling mechanism, a cryogenic refrigeration mechanism, a calibration mechanism, and a control mechanism. A comparison temperature block in the calibration mechanism is mounted on a pre-cooling plate. A first thermal switch connects the comparison temperature block to the pre-cooling plate, and a second thermal switch connects the comparison temperature block to the end cold head. The control mechanism allows the comparison temperature block to selectively connect to either the pre-cooling plate or the end cold head. By placing a pre-cooling plate and an end cold head within the vacuum chamber, and by using the first and second thermal switches, the comparison temperature block can switch between the refrigeration path corresponding to the pre-cooling plate and the refrigeration path corresponding to the end cold head. This enables continuous calibration over a wide temperature range, reduces the need for manual replacement of the cold source and manual adjustment of device connections during calibration, and improves calibration efficiency.

Description

Technical Field

[0001] This invention relates to the field of cryogenic metrology technology, and in particular to a cryogenic thermometer calibration device and a cooling control method. Background Technology

[0002] Cryothermometers are widely used in fields such as superconductivity, cryogenic physics, aerospace exploration, and cryogenic engineering. Their measurement accuracy directly affects the reliability of related equipment and experimental results. Therefore, cryothermometers usually need to be calibrated before use to obtain the correspondence between a certain parameter of the thermometer and temperature, ensuring that the actual measurement results are accurate and reliable.

[0003] Existing low-temperature thermometer calibration devices typically require a low-temperature cold source to establish the calibration environment. In some calibration devices, different cooling stages often rely on different cooling paths or different cold sources; for example, a higher-temperature cold source is used for pre-cooling, followed by a lower-temperature cold source for further cooling. When switching from one cooling stage to another, it is often necessary to manually change the cold source or adjust the connections between the heat transfer components. Manual pre-cooling, replacement, and vacuuming operations are also required, making the entire calibration process cumbersome and complex, affecting the continuity of the calibration process, and reducing calibration efficiency. Summary of the Invention

[0004] This invention provides a low-temperature thermometer calibration device and a cooling control method to solve the problem that existing calibration processes require manual adjustment of the cooling path or replacement of the cold source, resulting in complex operation and low calibration efficiency.

[0005] This invention provides a low-temperature thermometer calibration device, comprising: Vacuum cavity; A precooling mechanism having a precooling tray, the precooling tray being disposed within the vacuum chamber; A low-temperature refrigeration mechanism is disposed on the pre-cooling cold plate, and the low-temperature refrigeration mechanism has a terminal cold head; The calibration mechanism includes a comparison temperature block, a first thermal switch, and a second thermal switch. The comparison temperature block is disposed on the pre-cooling plate and is used to install a standard thermometer and a thermometer to be tested. The first thermal switch connects the comparison temperature block to the pre-cooling plate, and the second thermal switch connects the comparison temperature block to the end cold head. A control mechanism, connected to both the first thermal switch and the second thermal switch, is used to selectively connect the comparison temperature block to either the precooled cold plate or the end cold head.

[0006] According to a low-temperature thermometer calibration device provided by the present invention, a heater and a temperature sensor are provided on the comparison temperature block, and both the heater and the temperature sensor are connected to the control mechanism.

[0007] According to a cryogenic thermometer calibration device provided by the present invention, the cryogenic refrigeration mechanism includes a first component and a second component, the second component having the terminal cold head, and the first component being used to pre-cool and liquefy the working fluid in the second component.

[0008] According to the present invention, a low-temperature thermometer calibration device further includes a calibration cylinder, the calibration cylinder including a cylinder body and a connecting flange disposed on the cylinder body, and the vacuum cavity is formed in the cylinder body; The precooling mechanism includes a refrigerator and a precooling head. The refrigerator is located outside the vacuum chamber and has an intermediate cold head. The end of the intermediate cold head extends into the vacuum chamber through the connecting flange. The precooling head is disposed at the end of the intermediate cold head and is connected to the precooling plate through a first connector.

[0009] According to the low-temperature thermometer calibration device provided by the present invention, the pre-cooling mechanism further includes: An intermediate cold plate is disposed within the vacuum cavity and connected to the intermediate cold head via a second connector. A primary radiant tube is disposed on the intermediate cold plate, and the precooling cold head passes through the intermediate cold plate and is located inside the primary radiant tube. The precooling cold plate is disposed on the intermediate cold plate and is located inside the primary radiant tube. A secondary radiation tube is disposed on the precooling plate, and the end cold head and the calibration mechanism are both located inside the secondary radiation tube.

[0010] According to the low-temperature thermometer calibration device provided by the present invention, both the first connector and the second connector are flexible connectors.

[0011] According to a low-temperature thermometer calibration device provided by the present invention, a vibration damper is provided between the refrigeration unit and the connecting flange, and the intermediate cold head is inserted into the vibration damper.

[0012] According to a low-temperature thermometer calibration device provided by the present invention, the comparison temperature block is suspended on the pre-cooled cold plate by a suspension member.

[0013] According to the present invention, a low-temperature thermometer calibration device is provided, wherein the suspension component is one of Kevlar rope, epoxy fiberglass rod or stainless steel tube.

[0014] The present invention also provides a cooling control method, applied to the aforementioned low-temperature thermometer calibration device, the cooling control method comprising: Turn on the first thermal switch and turn off the second thermal switch, so that the comparison temperature block is connected to the pre-cooling plate through the first thermal switch to pre-cool the comparison temperature block; When the comparison temperature block drops below the preset switching temperature, the first thermal switch is disconnected and the second thermal switch is turned on, so that the comparison temperature block is connected to the end cold head through the second thermal switch to continue cooling the comparison temperature block; After the comparison temperature block is cooled to the target low temperature, the temperature of the comparison temperature block is adjusted by a heater and a temperature sensor to calibrate the standard thermometer and the thermometer to be tested.

[0015] The present invention provides a low-temperature thermometer calibration device and a cooling control method. By setting a pre-cooling cold plate and an end cold head in a vacuum cavity, and by setting a first thermal switch and a second thermal switch, the comparison temperature block can switch between the cooling path corresponding to the pre-cooling cold plate and the cooling path corresponding to the end cold head, thereby realizing continuous calibration over a wide temperature range, reducing the need for manual replacement of the cold source and manual adjustment of the device connection during the calibration process, and improving calibration efficiency. Attached Figure Description

[0016] 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.

[0017] Figure 1 This is a schematic diagram of the low-temperature thermometer calibration device provided by the present invention.

[0018] Figure 2 This is a schematic diagram of the calibration cylinder in the low-temperature thermometer calibration device provided by the present invention.

[0019] Figure 3 This is a schematic diagram of the pre-cooling mechanism in the low-temperature thermometer calibration device provided by the present invention.

[0020] Figure 4 This is a schematic diagram of the calibration mechanism in the low-temperature thermometer calibration device provided by the present invention.

[0021] Figure 5 This is a flowchart of the cooling control method provided by the present invention.

[0022] Figure Labels 1. Calibration cylinder; 11. Vacuum chamber; 12. Cylinder body; 13. Connecting flange; 2. Pre-cooling mechanism; 21. Pre-cooling plate; 22. Refrigeration unit; 221. Intermediate cold head; 222. Pre-cooling cold head; 23. First connecting piece; 24. Intermediate cold plate; 25. Second connecting piece; 26. Primary radiation cylinder; 27. Secondary radiation cylinder; 28. First support piece; 29. ​​Second support piece; 3. Low-temperature refrigeration mechanism; 31. First component; 311. Low-temperature cold head; 32. Second component; 321. Terminal cold head; 4. Calibration mechanism; 41. Comparison temperature block; 42. First thermal switch; 43. Second thermal switch; 44. Suspension piece; 5. Vibration damper. Detailed Implementation

[0023] 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.

[0024] The following is combined with Figures 1 to 4 This invention describes a low-temperature thermometer calibration device, which includes a vacuum chamber 11, a pre-cooling mechanism 2, a low-temperature refrigeration mechanism 3, a calibration mechanism 4, and a control mechanism. The pre-cooling mechanism 2 has a pre-cooling plate 21 disposed within the vacuum chamber 11. The low-temperature refrigeration mechanism 3 is disposed on the pre-cooling plate 21 and has a terminal cold head 321. The calibration mechanism 4 includes a comparison temperature block 41, a first thermal switch 42, and a second thermal switch 43. The comparison temperature block 41 is disposed on the pre-cooling plate 21 and is used to mount a standard thermometer and a thermometer to be tested. The first thermal switch 42 connects the comparison temperature block 41 to the pre-cooling plate 21, and the second thermal switch 43 connects the comparison temperature block 41 to the terminal cold head 321. The control mechanism is connected to both the first thermal switch 42 and the second thermal switch 43, and is used to selectively connect the comparison temperature block 41 to either the pre-cooling plate 21 or the terminal cold head 321.

[0025] By setting a pre-cooling cold plate 21 and an end cold head 321 in the vacuum chamber 11, and by setting a first thermal switch 42 and a second thermal switch 43, the comparison temperature block 41 can switch between the cooling path corresponding to the pre-cooling cold plate 21 and the cooling path corresponding to the end cold head 321, thereby achieving continuous calibration over a wide temperature range, reducing the need for manual replacement of the cold source and manual adjustment of the device connection during the calibration process, and improving calibration efficiency.

[0026] In some embodiments, the precooling plate 21 is used for precooling, and the terminal cold head 321 is used for further cooling, thereby allowing the cooling process of the comparison temperature block 41 to be carried out in stages. The precooling plate 21 is used to reduce the initial heat load of the comparison temperature block 41 and the cryogenic refrigeration mechanism 3, so that the cryogenic refrigeration mechanism 3 reaches the starting temperature required for operation, which is beneficial for the cryogenic refrigeration mechanism 3 to enter the working state and ensure its normal operation. The terminal cold head 321 is used to achieve further cooling on the basis of the cooling of the precooling plate 21, thereby improving the stability of the cooling process and completing wide temperature range calibration on the same comparison temperature block 41.

[0027] The precooling mechanism 2 includes a precooling plate 21, which is disposed within the vacuum chamber 11. The precooling mechanism 2 cools the comparison temperature block 41 from room temperature to a preset switching temperature, which can be 4 Kelvin or 3 Kelvin, etc. This preset switching temperature represents the temperature range achievable by the precooling mechanism 2, and therefore changes synchronously depending on the specific precooling mechanism 2. In this embodiment, the preset switching temperature of the precooling mechanism 2 is 4 Kelvin.

[0028] In this embodiment, the pre-cooling plate 21 can be made of a high thermal conductivity material such as oxygen-free copper to give it good temperature uniformity.

[0029] The cryogenic refrigeration unit 3 is mounted on the pre-cooling plate 21. Utilizing the low-temperature environment of the pre-cooling plate 21, it reaches the required initial operating temperature, ensuring normal operation, and outputs the low temperature through the terminal cold head 321. The terminal cold head 321 is used to lower the comparison temperature block 41 to the target low temperature, which can be approximately 0.3 Kelvin. In some other applications, the target low temperature can be 0.2 Kelvin, 0.5 Kelvin, or 1 Kelvin, etc.

[0030] The calibration mechanism 4 includes a comparison temperature block 41, a first thermal switch 42, and a second thermal switch 43. The comparison temperature block 41 is mounted on the pre-cooling plate 21 and is used to mount a standard thermometer and a thermometer to be tested. The comparison temperature block 41 is provided with mounting holes or slots for fixing the standard thermometer and the thermometer to be tested, and to ensure good thermal contact between the temperature sensing elements of the standard thermometer and the thermometer to be tested and the comparison temperature block 41, thereby ensuring that the standard thermometer and the thermometer to be tested are in the same temperature environment.

[0031] Optionally, the comparison temperature block 41 can be made of high-purity oxygen-free copper or high-purity silver. In this embodiment, the comparison temperature block 41 is made of high-purity oxygen-free copper. High-purity oxygen-free copper has good thermal conductivity, which is beneficial to forming a uniform temperature field inside the comparison temperature block 41, so that the standard thermometer and the thermometer to be measured installed on it are in the same temperature environment.

[0032] The control mechanism is connected to both the first thermal switch 42 and the second thermal switch 43. The control mechanism allows the comparison temperature block 41 to selectively connect to either the pre-cooling plate 21 or the end cold head 321. Specifically, the control mechanism can initially turn on the first thermal switch 42 and turn off the second thermal switch 43. At this point, the comparison temperature block 41 is thermally connected to the pre-cooling plate 21, and the pre-cooling mechanism 2 rapidly pre-cools the comparison temperature block 41. Once the temperature drops to the preset switching temperature, the control mechanism turns off the first thermal switch 42 and turns on the second thermal switch 43, disconnecting the comparison temperature block 41 from the pre-cooling plate 21 and connecting it to the end cold head 321, thereby further cooling the comparison temperature block 41 to the target low temperature. This solves the temperature range limitation of a single cooling method, enables free switching of the cold source, and ensures the continuity and stability of the calibration process over a wide temperature range.

[0033] Optionally, the structures of the first thermal switch 42 and the second thermal switch 43 can be the same or different. The first thermal switch 42 and the second thermal switch 43 can be either air gap thermal switches or mechanical thermal switches. By setting the first thermal switch 42 and the second thermal switch 43, thermal isolation and thermal connection between cold heads of different temperature zones can be achieved without manually replacing the cold source, and the temperature zone transition is smooth.

[0034] In some embodiments, the comparison temperature block 41 is equipped with a heater and a temperature sensor, both of which are connected to a control mechanism. The heater is used to regulate heating after the comparison temperature block 41 drops to the target low temperature, and the temperature sensor is used to detect the temperature of the comparison temperature block 41 in real time. The control mechanism controls the heater to operate based on the temperature information fed back by the temperature sensor, thereby stabilizing the comparison temperature block 41 at the target calibration temperature. By setting up the heater and temperature sensor, the comparison temperature block 41 can achieve stable control of the target calibration temperature after reaching the low temperature, thus enabling multi-temperature point calibration.

[0035] Of course, the control mechanism can also calculate the difference between the real-time temperature and the target calibration temperature, and dynamically adjust the heating current according to the magnitude and trend of the difference, thereby maintaining the comparison temperature block 41 at the set temperature point. Specifically, in the lower temperature range, when the second thermal switch 43 is on and the first thermal switch 42 is off, the heat generated by the heater and the cooling energy transferred from the end cold head 321 reach a dynamic balance. In the higher temperature range, when both the second thermal switch 43 and the first thermal switch 42 are off, the comparison temperature block 41 dissipates heat through radiative heat exchange and conductive heat leakage between itself and the low-temperature environment formed by the pre-cooling mechanism 2. The heat provided by the heater and the heat lost by the comparison temperature block 41 to the low-temperature environment formed by the pre-cooling mechanism 2 reach a dynamic balance, thus allowing the comparison temperature block 41 to remain stable at different temperature points. This eliminates temperature fluctuations during passive cooling, enabling the device to achieve a stable constant temperature environment at any temperature point within a wide temperature range of 0.3 Kelvin to 120 Kelvin, ensuring the stability of the temperature environment.

[0036] Optionally, the low-temperature thermometer calibration device may also include a data acquisition mechanism, which is electrically connected to the control mechanism to acquire recorded data.

[0037] like Figure 1 As shown, in some embodiments, the cryogenic refrigeration mechanism 3 includes a first component 31 and a second component 32. The second component 32 has a terminal cold head 321. The first component 31 is used to pre-cool and liquefy the working fluid in the second component 32. By first pre-cooling and liquefying the working fluid in the second component 32 through the first component 31, the second component 32 is equipped with the working conditions to output a lower cryogenic capacity. Then, the second component 32 outputs the cryogenic capacity through the terminal cold head 321 to achieve further cooling of the comparison temperature block 41.

[0038] Specifically, the first component 31 has a low-temperature cold head 311, which is thermally connected to the part of the second component 32 used for pre-cooling and liquefying the working fluid. When the first component 31 is working, the low-temperature cooling energy it generates is transferred to the part for pre-cooling and liquefying the working fluid, thereby bringing the working fluid in the second component 32 to a pre-cooled state. By pre-cooling and liquefying the working fluid in the second component 32 through the first component 31, the heat load that the second component 32 needs to overcome to enter the working state can be reduced, thus improving the cooling efficiency of the second component 32.

[0039] After the working fluid in the second component 32 is pre-cooled and liquefied by the first component 31, it can reach the target low temperature at the end cold head 321 through evaporative cooling. The low-temperature cooling provided by the end cold head 321 is transferred to the comparison temperature block 41 through the second thermal switch 43, so that the comparison temperature block 41 continues to cool down after pre-cooling and reaches the temperature required for calibration. Therefore, compared with the method of direct cooling through a single cooling component, this device can achieve a lower limit temperature, and the staged cooling process is more stable and controllable.

[0040] Optionally, the first component 31 and the second component 32 can each employ cryogenic refrigeration components of different temperature levels. Specifically, the first component 31 can be a component providing higher temperature-level cryogenic cooling capacity, and the second component 32 can be a component providing lower temperature-level cooling capacity. Further, the first component 31 can be a helium-4 component, and the second component 32 can be a helium-3 component. The working fluid in the second component 32 is helium-3, and the first component 31 is used to pre-cool and liquefy the helium-3 working fluid, enabling the temperature of the terminal cold head 321 to reach the target low temperature. In this embodiment, the target low temperature is 0.3 Kelvin.

[0041] Furthermore, the first component 31 and the second component 32 can employ adsorption refrigeration, or other low-temperature refrigeration methods capable of combining pre-cooling and liquefaction. Taking adsorption refrigeration as an example, the first component 31 can pre-cool and liquefy the working fluid in the second component 32 by creating a lower temperature environment, and the second component 32 can then further refrigerate using the liquefied working fluid. This allows the terminal cold head 321 to output a lower temperature cooling capacity.

[0042] In addition, the first component 31 and the second component 32 in the cryogenic refrigeration mechanism 3 can each be provided in one set or two sets, so as to form two sets of cryogenic refrigeration mechanisms 3 working alternately, so as to continuously maintain the cryogenic environment after reaching the target low temperature, so as to meet the needs of long-term continuous operation.

[0043] In this embodiment, the device employs a dry calibration method to calibrate the cryogenic thermometer. During the calibration process, the comparison temperature block 41, the standard thermometer, and the thermometer to be tested are all housed within the vacuum chamber 11, without needing to be immersed in liquid helium, liquid nitrogen, or other liquid refrigerants. The cooling capacity required for the comparison temperature block 41 is provided by the pre-cooling mechanism 2 and the cryogenic refrigeration mechanism 3, and is transferred to the comparison temperature block 41 through the pre-cooling cold plate 21, the end cold head 321, and the first thermal switch 42 or the second thermal switch 43. Compared to the traditional method of providing cooling capacity through liquid helium vacuum evaporation or an external helium-3 vacuum evaporation system, this device does not require the replenishment of liquid helium or helium-3 refrigerant. Instead, it creates a cryogenic environment through the refrigerator 22 and the cryogenic refrigeration mechanism 3, and then adjusts the temperature of the comparison temperature block 41 through a heater and a temperature sensor, thereby achieving dry calibration of the standard thermometer and the thermometer to be tested on the same comparison temperature block 41.

[0044] Reference Figures 1-4 Specifically, the comparison temperature block 41 is first connected to the pre-cooling plate 21 via the first thermal switch 42, and the comparison temperature block 41 is cooled by the pre-cooling capacity provided by the refrigerator 22. Then, the comparison temperature block 41 is connected to the end cold head 321 via the second thermal switch 43, and the first component 31 and the second component 32 form a low-temperature cooling capacity, thereby continuing to cool the comparison temperature block 41. After reaching the target low temperature, the temperature of the comparison temperature block 41 is adjusted and monitored by the heater and temperature sensor installed on the comparison temperature block 41, thereby realizing dry calibration at different temperature points. When the comparison temperature block 41 is heated to a temperature above 4 Kelvin by the heater, the second thermal switch 43 is disconnected and calibration is performed. In addition, the heater can heat up to 120 Kelvin, thereby realizing a wide temperature range detection from 0.3 Kelvin to 120 Kelvin, meeting the full-range calibration requirements of the low-temperature thermometer. By placing the comparison temperature block 41 inside the vacuum chamber 11 during the calibration process, there is no need to immerse it in liquid refrigerant, thus achieving dry calibration over a wide temperature range.

[0045] Reference Figures 1-3 In some embodiments, the low-temperature thermometer calibration device further includes a calibration cylinder 1, which includes a cylinder body 12 and a connecting flange 13 disposed on the cylinder body 12. A vacuum chamber 11 is formed inside the cylinder body 12. The pre-cooling mechanism 2 includes a refrigerator 22, which is located outside the vacuum chamber 11. The refrigerator 22 has an intermediate cold head 221 and a pre-cooling cold head 222. The end of the intermediate cold head 221 extends into the vacuum chamber 11 through the connecting flange 13. The pre-cooling cold head 222 is disposed at the end of the intermediate cold head 221 and is connected to the pre-cooling plate 21 through a first connecting member 23. The connecting flange 13 is disposed at the top of the cylinder body 12 to achieve a vacuum seal. The pre-cooling mechanism 2 includes a refrigerator 22, which is located outside the vacuum chamber 11, facilitating heat dissipation of the refrigerator 22 and effectively preventing the heat from the refrigerator 22 from directly radiating into the vacuum chamber 11. The intermediate cold head 221 is used to intercept a large amount of heat transferred from the room temperature environment. The pre-cooling cold head 222 is located at the end of the intermediate cold head 221 and is used to provide cooling at a lower temperature. The lower temperature is transferred to the pre-cooling plate 21 through the first connector 23.

[0046] Optionally, the refrigerator 22 can be a pulse tube refrigerator or a GM refrigerator, etc. In this embodiment, a 4K temperature zone pulse tube refrigerator is used, and the lowest temperature of the refrigerator 22 can reach about 4 Kelvin.

[0047] In some embodiments, the precooling mechanism 2 further includes an intermediate cold plate 24, a primary radiation tube 26, and a secondary radiation tube 27. The intermediate cold plate 24 is disposed within the vacuum chamber 11 and connected to the intermediate cold head 221 via a second connector 25; the primary radiation tube 26 is disposed on the intermediate cold plate 24, the precooling cold head 222 passes through the intermediate cold plate 24 and is located within the primary radiation tube 26, and the precooling cold plate 21 is disposed on the intermediate cold plate 24 and is located within the primary radiation tube 26; the secondary radiation tube 27 is disposed on the precooling cold plate 21, and the end cold head 321 and the calibration mechanism 4 are both located within the secondary radiation tube 27. Thus, a radiation shielding structure with a gradually decreasing temperature from the outside to the inside is formed within the vacuum chamber 11. By arranging the end cold head 321 and the calibration mechanism 4 inside the secondary radiation tube 27, radiative heat leakage from the higher-temperature area on the outside can be further reduced, ensuring a low-temperature environment and reducing the impact of ambient temperature.

[0048] The intermediate cold plate 24 is hung on the connecting flange 13 by the first support member 28, so that the intermediate cold plate 24 and the connecting flange 13 are spaced apart. This makes it easier for the intermediate cold head 221 to extend into the vacuum chamber 11 through the connecting flange 13 and connect with the intermediate cold plate 24. It can also reduce the heat conduction effect of the connecting flange 13 on the intermediate cold plate 24 and reduce the heat leakage to the intermediate cold plate 24 through the connecting flange 13.

[0049] The precooling plate 21 is hung on the intermediate plate 24 by the second support member 29, so that the precooling plate 21 is spaced apart from the intermediate plate 24, reducing the heat conduction effect of the intermediate plate 24 on the precooling plate 21 and reducing heat leakage from the intermediate plate 24 to the precooling plate 21.

[0050] The first support 28 and the second support 29 are both made of low thermal conductivity materials, such as Kevlar, epoxy glass fiber, epoxy glass fiber rod and thin-walled stainless steel.

[0051] Optionally, both the first connector 23 and the second connector 25 are flexible connectors. The first connector 23 connects the precooling cold head 222 to the precooling cold plate 21, and the second connector 25 connects the intermediate cold head 221 to the intermediate cold plate 24. The flexible connector can be made of materials such as copper braid, aluminum braid, flexible graphite tape, multi-strand fine copper wire braid, or other flexible heat-conducting components. When the refrigerator 22 vibrates during operation, the flexible connector can undergo elastic deformation to absorb the vibration, reduce the transmission of vibration to the comparison temperature block 41, and improve the temperature stability during the calibration process. In this embodiment, the first connector 23 is a copper braid, and the second connector 25 is a high-purity oxygen-free copper braid.

[0052] In some embodiments, a vibration damper 5 is provided between the refrigerator 22 and the connecting flange 13, and an intermediate cold head 221 passes through the vibration damper 5. The vibration damper 5 is located at the interface between the refrigerator 22 and the vacuum chamber 11, and the inner cavity of the vibration damper 5 is used for the intermediate cold head 221 and the pre-cooling cold head 222 located at its end to pass through. Vibrations generated by the compressor or rotary valve of the refrigerator 22 are transmitted to the vacuum chamber 11 through the connecting flange 13, thereby affecting the internal components of the vacuum chamber 11. The vibration damper 5 can reduce the transmission of vibration.

[0053] Alternatively, the vibration damper 5 can be made of materials such as a vibration damping bellows, a rubber vibration isolator, or a corrugated metal hose.

[0054] Reference Figures 1-4 In some embodiments, the comparison temperature block 41 is suspended on the precooling plate 21 by a suspension member 44. By suspending the comparison temperature block 41 on the precooling plate 21, heat conduction and mechanical vibration caused by the support path of the comparison temperature block 41 can be reduced, thereby further improving the temperature stability of the comparison temperature block 41.

[0055] Optionally, the suspension element 44 is one of Kevlar rope, epoxy fiberglass rod, or stainless steel tube. Specifically, the stainless steel tube is preferably a thin-walled stainless steel tube. Optionally, a thin-walled stainless steel tube refers to a tube with an outer diameter to wall thickness ratio greater than 20 to ensure that it has low thermal conductivity.

[0056] Reference Figures 1-4 In summary, the low-temperature thermometer calibration device provided in this embodiment, through the switching of the first thermal switch 42 and the second thermal switch 43, allows the comparison temperature block 41 to be connected to the cooling path corresponding to the pre-cooling cold plate 21 and the cooling path corresponding to the end cold head 321, respectively. The pre-cooling cold plate 21 is used to pre-cool the comparison temperature block 41, and the end cold head 321 is used to further cool the comparison temperature block 41 based on the pre-cooling. The standard thermometer and the thermometer to be tested can be calibrated on the same comparison temperature block 41, achieving wide-temperature-range calibration. The temperature of the comparison temperature block 41 is adjusted and controlled by setting up a heater and a temperature sensor. The flexible connector, vibration-damping bellows, and suspension member 44 reduce heat leakage and vibration interference, improving the temperature stability of the comparison temperature block 41. Furthermore, the first component 31 and the second component 32 further achieve lower-temperature cooling based on pre-cooling, thereby meeting the calibration requirements of low-temperature thermometers and realizing a fully dry low-temperature calibration device that does not require external liquid helium or external helium-3 replenishment. This reduces the need for manual replacement of the cold source and complex pre-cooling, replacement, and vacuuming operations in traditional calibration processes, simplifying the calibration process and improving calibration efficiency.

[0057] The following is combined with Figures 1 to 5The present invention also provides a cooling control method applied to the aforementioned low-temperature thermometer calibration device, the cooling control method comprising: S100: Turn on the first thermal switch 42 and turn off the second thermal switch 43, so that the comparison temperature block 41 is connected to the pre-cooling plate 21 through the first thermal switch 42 to pre-cool the comparison temperature block 41. S200: When the comparison temperature block 41 drops below the preset switching temperature, the first thermal switch 42 is disconnected and the second thermal switch 43 is turned on, so that the comparison temperature block 41 is connected to the end cold head 321 through the second thermal switch 43, so as to continue to cool down the comparison temperature block 41. S300: After the comparison temperature block 41 drops to the target low temperature, the temperature of the comparison temperature block 41 is adjusted by the heater and temperature sensor to stabilize it at the required calibration temperature point, so as to provide a stable temperature field for the standard thermometer and the thermometer under test.

[0058] The control mechanism controls the first thermal switch 42 to be in the conducting state and the second thermal switch 43 to be in the open state, thermally connecting the comparison temperature block 41 to the pre-cooling plate 21 and thermally insulatingly connecting the comparison temperature block 41 to the end cold head 321. The pre-cooling mechanism 2 is activated, causing the temperature of the pre-cooling plate 21 to drop. Cooling is then transferred to the comparison temperature block 41 through heat conduction, thus cooling the comparison temperature block 41.

[0059] The control mechanism monitors the temperature of the comparison temperature block 41 in real time. When the temperature sensor detects that the temperature has dropped below the preset switching temperature, it transmits a signal to the control mechanism. The preset switching temperature can be set based on the optimal operating temperature range of the cryogenic refrigeration mechanism 3 and the lowest temperature limit of the pre-cooling mechanism 2. For example, when the pre-cooling mechanism 2 uses a 4K refrigerator 22 and the cryogenic refrigeration mechanism 3 uses a helium-3 adsorption refrigerator 22, the preset switching temperature can be set between 3 Kelvin and 5 Kelvin, preferably around 4 Kelvin. Upon receiving the signal, the control mechanism first controls the first thermal switch 42 to open, cutting off the thermal connection between the comparison temperature block 41 and the pre-cooling plate 21, preventing the relatively high temperature of the pre-cooling plate 21 from becoming a heat load on the comparison temperature block 41. Then, it controls the second thermal switch 43 to open, thermally connecting the comparison temperature block 41 to the end cold head 321. The cryogenic refrigeration mechanism 3 is then activated, further cooling the comparison temperature block 41 to the target low temperature, such as 0.3 Kelvin, thereby ensuring a smooth switching of the cold source and avoiding the effects of temperature rise or thermal shock.

[0060] Once the temperature of the comparison temperature block 41 drops to the target low temperature, the temperature sensor collects the temperature data of the comparison temperature block 41 in real time and feeds it back to the control mechanism. The control mechanism controls the power output of the heater based on the difference between the set temperature and the actual temperature. By adjusting the dynamic balance between the heating power and the cooling capacity of the refrigerator 22, the comparison temperature block 41 is maintained at any set temperature point. During the calibration process, the operator can set multiple temperature calibration points within a wide temperature range of 0.3 Kelvin to 120 Kelvin. After the temperature stabilizes, the readings of the standard thermometer and the thermometer under test are recorded, thus completing the calibration of the thermometer under test.

[0061] In some embodiments, when the temperature of the comparison temperature block 41 is within the range of the target low temperature and the preset switching temperature, the second thermal switch 43 remains on and the first thermal switch 42 remains off; when the temperature of the comparison temperature block 41 is higher than the preset switching temperature, both the second thermal switch 43 and the first thermal switch 42 are controlled to open. During calibration, when the temperature is between 0.3 Kelvin and 4 Kelvin, the control mechanism controls the second thermal switch 43 to open and the first thermal switch 42 to open. When the temperature is higher than 4 Kelvin, the control mechanism controls both the second thermal switch 43 and the first thermal switch 42 to open, and the comparison temperature block 41 is adjusted to the required target temperature by the heater.

[0062] It should be noted that the temperature value in this embodiment is a temperature range value. In actual use, it is sufficient to reach the temperature range defined in this embodiment. For example, 4 Kelvin in the above embodiment refers to a temperature of approximately 4 Kelvin. In addition, the parts not mentioned in this embodiment are the same as the connection method and calibration method of the calibration device in the prior art, and will not be described in detail in this embodiment.

[0063] It should be noted that relational terms such as "first" and "second" mentioned in this application are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or specific order or sequence between these entities or operations. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented, for example, in orders other than those illustrated or described herein.

[0064] Furthermore, the terms "comprising," "including," and "having," as well as any 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 process, method, article, or apparatus. For example, a process, method, system, product, or apparatus that comprises a list of steps or units is not necessarily limited to those steps or units expressly listed, but may include other steps or units not expressly listed or inherent to such process, method, product, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes the element.

[0065] For ease of description, spatial relative terms such as "above," "on top of," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation beyond the orientation of the device as described in the figures. For example, if the device in the figures were inverted, a device described as "above" or "on top of" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein will be interpreted accordingly.

[0066] The above are merely specific embodiments of this application, enabling those skilled in the art to understand or implement this application. Various modifications and variations to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application. Therefore, this application is not limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A low-temperature thermometer calibration device, characterized in that, include: Vacuum cavity; A precooling mechanism having a precooling tray, the precooling tray being disposed within the vacuum chamber; A low-temperature refrigeration mechanism is disposed on the pre-cooling cold plate, and the low-temperature refrigeration mechanism has a terminal cold head; The calibration mechanism includes a comparison temperature block, a first thermal switch, and a second thermal switch. The comparison temperature block is disposed on the pre-cooling plate and is used to install a standard thermometer and a thermometer to be tested. The first thermal switch connects the comparison temperature block to the pre-cooling plate, and the second thermal switch connects the comparison temperature block to the end cold head. A control mechanism, connected to both the first thermal switch and the second thermal switch, is used to selectively connect the comparison temperature block to either the precooled cold plate or the end cold head.

2. The low-temperature thermometer calibration device according to claim 1, characterized in that, The comparison temperature block is equipped with a heater and a temperature sensor, both of which are connected to the control mechanism.

3. The low-temperature thermometer calibration device according to claim 1, characterized in that, The cryogenic refrigeration mechanism includes a first component and a second component, the second component having the terminal cold head, and the first component being used to pre-cool and liquefy the working fluid in the second component.

4. The low-temperature thermometer calibration device according to claim 1, characterized in that, It also includes a calibration cylinder, which includes a cylinder body and a connecting flange disposed on the cylinder body, and the vacuum chamber is formed inside the cylinder body; The precooling mechanism includes a refrigerator located outside the vacuum chamber. The refrigerator has an intermediate cold head and a precooling cold head. The end of the intermediate cold head extends into the vacuum chamber through the connecting flange. The precooling cold head is located at the end of the intermediate cold head and is connected to the precooling plate through a first connector.

5. The low-temperature thermometer calibration device according to claim 4, characterized in that, The precooling mechanism also includes: An intermediate cold plate is disposed within the vacuum cavity and connected to the intermediate cold head via a second connector. A primary radiant tube is disposed on the intermediate cold plate, and the precooling cold head passes through the intermediate cold plate and is located inside the primary radiant tube. The precooling cold plate is disposed on the intermediate cold plate and is located inside the primary radiant tube. A secondary radiation tube is disposed on the precooling plate, and the end cold head and the calibration mechanism are both located inside the secondary radiation tube.

6. The low-temperature thermometer calibration device according to claim 5, characterized in that, Both the first connector and the second connector are flexible connectors.

7. The low-temperature thermometer calibration device according to claim 4, characterized in that, A vibration damper is provided between the refrigeration unit and the connecting flange, and the intermediate cold head is inserted into the vibration damper.

8. The low-temperature thermometer calibration device according to any one of claims 1-7, characterized in that, The comparison temperature block is suspended on the precooling plate by a suspension component.

9. The low-temperature thermometer calibration device according to claim 8, characterized in that, The suspension component is one of Kevlar rope, epoxy fiberglass rod, or stainless steel tube.

10. A cooling control method, characterized in that, The cooling control method, applied to the low-temperature thermometer calibration device as described in any one of claims 1-9, comprises: Turn on the first thermal switch and turn off the second thermal switch, so that the comparison temperature block is connected to the pre-cooling plate through the first thermal switch to pre-cool the comparison temperature block; When the comparison temperature block drops below the preset switching temperature, the first thermal switch is disconnected and the second thermal switch is turned on, so that the comparison temperature block is connected to the end cold head through the second thermal switch to continue cooling the comparison temperature block; After the comparison temperature block is cooled to the target low temperature, the temperature of the comparison temperature block is adjusted by a heater and a temperature sensor to calibrate the standard thermometer and the thermometer to be tested.

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