RRR value measuring device and measuring method

Abstract

The invention relates to the technical field of measuring devices, in particular to an RRR value measuring device and a measuring method.The RRR value measuring device is internally provided with a base assembly, a container assembly, a refrigeration assembly and a measuring assembly, the container assembly is fixedly installed on the base assembly and comprises a helium cavity, the refrigeration assembly is installed in the container assembly, and the helium cavity is communicated with the helium cavity. The refrigerating end of the refrigerating assembly is connected with the helium cavity, and the measuring assembly is used for placing a metal sample of which the RRR value is to be detected into the helium cavity; therefore, the metal sample is fixed in the helium cavity through the measuring assembly, and the temperature in the helium cavity is reduced through the refrigerating assembly, so that the temperature of helium in the helium cavity reaches a low temperature required for measuring the RRR value of the metal sample, and a low-temperature environment required for measuring the RRR value of the metal sample is manufactured; by replacing a liquid helium environment with a helium environment, the measurement cost of the RRR value can be effectively reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of measuring devices, and in particular to an RRR value measuring device and a measuring method. Background Art

[0002] With the development of modern science and technology, the demand for high-purity metals is increasing. The residual resistivity (RRR) of metal is a parameter that can reflect the purity of metal. By measuring the RRR of metal, the impurity content in the metal can be determined, and then the purity of the metal can be obtained. The definition of the residual resistivity of metal is the ratio of the two resistivities of the metal at room temperature and at absolute zero. The larger the RRR value, the higher the purity of the metal. In the actual RRR value measurement process, it is impossible to create an absolute zero test environment, and the temperature of the test environment can only be made as close to absolute zero as possible. Liquid helium is usually used to create the low-temperature environment required for measuring the RRR value; however, the existing RRR value measurement device has the disadvantages of poor sealing performance, inconvenient loading and unloading, poor stability and poor measurement accuracy when used.

[0003] In order to solve the above technical problems, the technical solution of the Chinese utility model patent announcement with patent application number CN201920122639.5 is a device for measuring the RRR value of a conductor, including a sample rod, a sample skeleton and a cryogenic container, the top of the cryogenic container is threadedly connected with a sealing flange, the middle of the sealing flange is penetrated and fixed with a longitudinally arranged sample rod, the bottom end of the sample rod is inserted into the interior of the cryogenic container, the bottom middle end of the sealing flange is connected with a threaded head, and the threaded head is threadedly connected to the cryogenic container. The sample can be stably fixed on the skeleton through a clamping mechanism, which can not only ensure reliable contact, but also facilitate disassembly without damaging the conductor sample. The sample skeleton is fixedly connected to the sample rod by threads, which is convenient for disassembly and replacement, simple for later maintenance, and low cost. And when measuring at low temperature, it is first pre-cooled in liquid nitrogen, and then placed in liquid helium for measurement, saving the use of liquid helium and reducing the cost of measurement.

[0004] However, the above-mentioned prior art has the following technical problems: when measuring the RRR value of a sample, the above-mentioned device for measuring the RRR value of a conductor needs to use liquid helium to create the low-temperature environment required for measuring the RRR value, but liquid helium is expensive, which increases the measurement cost of the RRR value. Summary of the invention

[0005] In view of this, it is necessary to provide a RRR value measuring device and a measuring method, which do not use liquid helium to create a low-temperature environment, thereby reducing the measurement cost of the RRR value.

[0006] In a first aspect, the present invention provides an RRR value measuring device, comprising a base assembly, a container assembly, a refrigeration assembly and a measuring assembly, wherein the container assembly is fixedly mounted on the base assembly, the container assembly comprises a helium cavity for storing helium, the refrigeration assembly is mounted in the container assembly, a refrigeration end of the refrigeration assembly is connected to the helium cavity to reduce the temperature of the helium cavity, and the measuring assembly is used to place a metal sample whose RRR value is to be detected into the helium cavity and measure the RRR value of the metal sample.

[0007] Preferably, the base assembly includes a fixing frame, at least three hoofs and at least three first fixing rods, each hoof is evenly fixed on the bottom surface of the fixing frame for supporting the fixing frame, one end of each first fixing rod is fixedly connected to the top surface of the fixing frame, and the other end is fixedly connected to the outer edge of the container assembly for fixing the container assembly.

[0008] Preferably, the container assembly further includes a vacuum cover and a cold shield, the outer side of the vacuum cover is fixedly connected to each first fixing rod, the cold shield is arranged in the vacuum cover, the helium cavity is arranged in the cold shield, and a vacuum state is maintained between the vacuum cover and the cold shield to prevent heat exchange between the cold shield and the outside world.

[0009] Preferably, the container assembly further comprises a first vacuum angle valve, an air supply valve, a pressure gauge and a safety valve, wherein the first vacuum angle valve, the air supply valve, the pressure gauge and the safety valve are all arranged at the top end of the helium chamber; the first vacuum angle valve is used to extract the air in the helium chamber, the air supply valve is used to replenish helium into the helium chamber, the pressure gauge is used to detect the air pressure in the helium chamber, and the safety valve is used to control the air pressure in the helium chamber and exhaust the air to the outside when the air pressure exceeds a predetermined pressure.

[0010] Preferably, the container assembly further comprises a second vacuum angle valve, and the second vacuum angle valve is arranged on the vacuum cover and is used for evacuating the vacuum cover.

[0011] Preferably, the refrigeration assembly includes a low-temperature refrigerator and a cold transfer chain, the low-temperature refrigerator extends into the vacuum cover from the top of the vacuum cover, the low-temperature refrigerator is provided with a first cold head and a second cold head, the first cold head is connected to the cold screen to reduce the temperature of the cold screen, one end of the cold transfer chain is connected to the second cold head, and the other end is connected to the helium cavity to reduce the temperature of the helium cavity.

[0012] Preferably, the measuring assembly includes a fixed seat, at least three second fixed rods, a wire seat, at least one thermal insulation member and a fixed plate, the bottom end of each second fixed rod is evenly installed on the top surface of the fixed seat, the top end of each second fixed rod is fixedly connected to the bottom end of the wire seat, and each thermal insulation plate is arranged on each second fixed rod at the same interval to separate the helium cavity to reduce the heat exchange between the bottom of the helium cavity and the outside world, the fixed plate is installed at the bottom end of the fixed seat to place the metal sample whose RRR value is to be tested, the fixed plate is electrically connected to the wire seat, and the wire seat is electrically connected to the voltage measuring device to detect the voltage value of each metal sample on the fixed plate whose RRR value is to be tested.

[0013] Preferably, the measuring assembly further comprises a plurality of fixing groups, each of which is evenly arranged on the fixing plate, and each of which comprises at least two symmetrically arranged fixing members for fixing the metal sample to be tested for RRR value onto the fixing plate.

[0014] Preferably, the RRR value measuring device also includes a temperature control component, which includes a temperature sensor, a heater and a temperature controller. The temperature sensor is installed on the fixed plate and is used to measure the temperature in the helium cavity. The heater is installed on the second cold head and is used to increase the temperature of the helium cavity. The temperature controller is electrically connected to the temperature sensor, the cryogenic refrigerator and the heater, and is used to adjust the power of the cryogenic refrigerator and the heater according to the temperature detected by the temperature sensor to control the temperature in the helium cavity.

[0015] In a second aspect, the present invention provides a measurement method based on the RRR value measurement device according to the first aspect, comprising the following steps:

[0016] S1, fix the metal sample to be tested for RRR value on a fixing plate;

[0017] S2, the voltage value of the metal sample measured at room temperature, recorded as U1;

[0018] S3, placing the measuring assembly into the helium chamber;

[0019] S4, extracting the air from the helium chamber;

[0020] S5, filling the helium chamber with helium;

[0021] S6, adjust the temperature in the helium chamber to make it close to absolute zero, and measure the voltage value of the metal sample at this time, which is recorded as U2;

[0022] S7, substitute U2 and U1 into the following formula:

[0023]

[0024] Here, RRR is the residual resistivity of the metal sample.

[0025] The RRR value measuring device is provided with a base assembly, a container assembly, a refrigeration assembly and a measuring assembly. The container assembly is fixedly mounted on the base assembly. The container assembly includes a helium cavity for storing helium. The refrigeration assembly is mounted in the container assembly. The refrigeration end of the refrigeration assembly is connected to the helium cavity to reduce the temperature of the helium cavity. The measuring assembly is used to place a metal sample whose RRR value is to be detected into the helium cavity and measure the RRR value of the metal sample. In this way, the metal sample is fixed to the helium cavity by the measuring assembly, and the temperature in the helium cavity is then reduced by the refrigeration assembly so that the temperature of the helium in the helium cavity reaches the low temperature required for measuring the RRR value of the metal sample, thereby creating a low-temperature environment required for measuring the RRR value of the metal sample. Since the price of helium is lower than that of liquid helium, the measurement cost of the RRR value can be effectively reduced by replacing the liquid helium environment with the helium environment. In terms of use, the temperature of liquid helium is extremely low. If it is not operated properly, it may cause frostbite to the operator. Helium can be stored at room temperature and will not cause harm to the operator due to the low temperature when used. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is an oblique bird's-eye view of the RRR value measuring device of the present application.

[0027] Figure 2 It is a cross-sectional view of the RRR value measuring device of the present application.

[0028] Figure 3 It is an oblique top-down view of the base assembly of the present application.

[0029] Figure 4 It is an oblique top view of the top area of ​​the vacuum hood of the present application.

[0030] Figure 5 It is an oblique top view of the measurement assembly of the present application.

[0031] Figure 6 This application Figure 5 A partial enlarged view of area A.

[0032] Figure 7 is a flow chart of the measurement method of the present application.

[0033] In the figure: RRR value measuring device 10, base assembly 20, fixing frame 21, hoof 22, first fixing rod 23, container assembly 30, helium chamber 31, vacuum cover 32, cold shield 33, first vacuum angle valve 34, air supply valve 35, pressure gauge 36, safety valve 37, second vacuum angle valve 38, refrigeration assembly 40, low-temperature refrigerator 41, cold chain 42, first cold head 43, second cold head 44, measuring assembly 50, fixing seat 51, second fixing rod 52, wire holder 53, thermal insulation 54, fixing plate 55, fixing group 56, fixing part 561, metal sample 60. DETAILED DESCRIPTION

[0034] The technical solutions and technical effects of the embodiments of the present invention are further described in detail below in conjunction with the accompanying drawings of the present invention.

[0035] Please refer to Figure 1 to Figure 2 In a first aspect, the present invention provides an RRR value measuring device 10, comprising a base assembly 20, a container assembly 30, a refrigeration assembly 40 and a measuring assembly 50. The container assembly 30 is fixedly mounted on the base assembly 20. The container assembly 30 comprises a helium cavity 31 for storing helium. The refrigeration assembly 40 is mounted in the container assembly 30. The refrigeration end of the refrigeration assembly 40 is connected to the helium cavity 31 to reduce the temperature of the helium cavity 31. The measuring assembly 50 is used to place a metal sample to be tested for RRR value into the helium cavity 31 and measure the RRR value of the metal sample. In this way, the metal sample is fixed to the helium cavity 31 by the measuring assembly 50, and the temperature in the helium cavity 31 is reduced by the refrigeration assembly 40, so that the temperature of the helium in the helium cavity 31 reaches the low temperature required for measuring the RRR value of the metal sample, thereby manufacturing a metal sample RRR measuring device. The low temperature environment required for the R value, since the price of helium is lower than that of liquid helium, the measurement cost of the RRR value can be effectively reduced by replacing the liquid helium environment with a helium environment. In terms of use, the temperature of liquid helium is extremely low. If it is not handled properly, it may cause frostbite to the operator. Helium can be stored at room temperature and will not cause harm to the operator due to the low temperature when used.

[0036] Please refer to Figure 3 Furthermore, the base assembly 20 includes a fixing frame 21, at least three hoofs 22 and at least three first fixing rods 23, each hoof 22 is evenly fixed on the bottom surface of the fixing frame 21, and is used to support the fixing frame 21 and maintain the stability of the fixing frame 21; one end of each first fixing rod 23 is fixedly connected to the top surface of the fixing frame 21, and the other end is fixedly connected to the outer edge of the container assembly 30, and is used to fix the container assembly 30, so as to stably install the container assembly 30 on the fixing frame 21.

[0037] Please refer to Figure 2Furthermore, the container assembly 30 also includes a vacuum cover 32 and a cold shield 33. The outer side of the vacuum cover 32 is fixedly connected to each first fixing rod 23 to fix the vacuum cover 32 to the fixing frame 21. The cold shield 33 is arranged in the vacuum cover 32, and the helium cavity 31 is arranged in the cold shield 33. There is a vacuum state between the vacuum cover 32 and the cold shield 33 to prevent the cold shield 33 from exchanging heat with the outside world, thereby maintaining the temperature stability of the cold shield 33.

[0038] In this embodiment, the helium cavity 31 is wrapped with a cold shield 33 so that the high temperature section of the helium cavity 31 is at the temperature of the cold shield 33 instead of the room temperature, thereby greatly reducing the radiation heat leakage of the helium cavity 31.

[0039] In this embodiment, the vacuum cover 32 is made of stainless steel, and the inner surface is completely polished. At the same time, all sealing structures are metal sealing structures, and all flanges are connected by knife-edge flange surfaces to effectively ensure the leakage rate of the vacuum cover 32 and the ultra-high vacuum working conditions in the vacuum cover 32.

[0040] Please refer to Figure 4 Furthermore, the container assembly 30 also includes a first vacuum angle valve 34, an air supply valve 35, a pressure gauge 36 and a safety valve 37. The first vacuum angle valve 34, the air supply valve 35, the pressure gauge 36 and the safety valve 37 are all arranged at the top of the helium chamber 31; the first vacuum angle valve 34 is used to extract the air in the helium chamber 31, the air supply valve 35 is used to replenish helium into the helium chamber 31, the pressure gauge 36 is used to detect the air pressure in the helium chamber 31, and the safety valve 37 is used to control the air pressure in the helium chamber 31 and exhaust the air to the outside when the air pressure exceeds the predetermined air pressure. Specifically, the predetermined air pressure is 0.15MPa.

[0041] Please refer to Figure 4 Furthermore, the container assembly 30 also includes a second vacuum angle valve 38 , which is disposed on the vacuum cover 32 and is used to evacuate the vacuum cover 32 .

[0042] Please refer to Figure 2 Furthermore, the refrigeration assembly 40 includes a low-temperature refrigerator 41 and a cold chain 42. The low-temperature refrigerator 41 extends into the vacuum cover 32 from the top of the vacuum cover 32. The low-temperature refrigerator 41 is provided with a first cold head 43 and a second cold head 44. The first cold head 43 is connected to the cold screen 33 to reduce the temperature of the cold screen 33. One end of the cold chain 42 is connected to the second cold head 44, and the other end is connected to the helium cavity 31 to reduce the temperature of the helium cavity 31.

[0043] In this embodiment, the cooling component 40 is made of oxygen-free copper and is gold-plated on the surface to reduce gas adsorption on the surface of the cooling component 40 and reduce the surface emissivity, thereby reducing radiation heat leakage.

[0044] Please refer to Figures 5 and 6 Further, the measuring assembly 50 includes a fixing seat 51, at least three second fixing rods 52, a wire seat 53, at least one heat insulating member 54 and a fixing plate 55. The bottom ends of the second fixing rods 52 are evenly mounted on the top surface of the fixing seat 51, and the top ends of the second fixing rods 52 are fixedly connected to the bottom ends of the wire seats 53. The heat insulating plates are arranged on the second fixing rods 52 at the same intervals, and are used to separate the helium cavity 31 to reduce the heat exchange between the bottom of the helium cavity 31 and the outside. Specifically, the inside of the helium cavity 31 is divided into a plurality of cold zones by the heat insulating plates, thereby preventing the outside temperature at the top of the helium cavity from affecting the bottom temperature of the helium cavity 31. , so that the temperature at the bottom of the helium chamber 31 is the lowest and most stable. The fixing plate 55 is installed at the bottom of the fixing base 51, and is used to place the metal sample whose RRR value is to be detected. The fixing plate 55 is electrically connected to the wire holder 53, and the wire holder 53 is electrically connected to the voltage measuring device to detect the voltage value of each metal sample whose RRR value is to be detected on the fixing plate 55. Specifically, the fixing plate 55 is connected to the wire holder 53 through a low-temperature and low-loss wire, and then electrically connected to the voltage measuring device through the wire holder 53 to form a closed-loop circuit, so as to obtain the voltage value of each metal sample whose RRR value is to be detected on the fixing plate 55 through the voltage measuring device.

[0045] Please refer to Figure 6 Furthermore, the measuring assembly 50 also includes a plurality of fixing groups 56, each fixing group 56 is evenly arranged on the fixing plate 55, and each fixing group 56 includes at least two symmetrically arranged fixing members 561, which are used to fix the metal sample to be tested for RRR value to the fixing plate 55; specifically, a protrusion is provided in the middle of each fixing member 561, and both ends of each fixing member 561 are fixed to the fixing plate 55 by bolts, so that each metal sample to be tested for RRR value can be fixed to the fixing plate 55 by clamping through the protrusion in the middle of each fixing member 561.

[0046] Furthermore, the RRR value measuring device 10 also includes a temperature control component, which includes a temperature sensor, a heater and a temperature controller. The temperature sensor is installed on the fixed plate 55 and is used to measure the temperature in the helium cavity 31. The heater is installed on the second cold head 44 and is used to increase the temperature of the helium cavity 31. The temperature controller is electrically connected to the temperature sensor, the low-temperature refrigerator 41 and the heater, and is used to adjust the power of the low-temperature refrigerator 41 and the heater according to the temperature detected by the temperature sensor to control the temperature in the helium cavity 31, thereby achieving precise control of the temperature of the helium cavity 31, which is convenient for measuring the RRR value of the metal sample.

[0047] In this embodiment, the temperature controller is a product of Lakeshore, Model 335, which has 4-way temperature measurement and 2-way temperature control functions; the heater is an ultra-high vacuum compatible product with a resistance of 25Ω and a heating power of 100W.

[0048] In this embodiment, the control software developed based on LabVIEW is used for control. The software can realize the functions of real-time detection of temperature and heating, data storage, historical data viewing, etc., and also has the function of automatic temperature adjustment control. In addition, it also has a remote interface for remote data viewing, etc. The operation and interface are simple, and it can be further developed according to user requirements.

[0049] Please refer to Figure 7 In a second aspect, the present invention provides a measurement method of the RRR value measurement device 10 based on the first aspect, comprising the following steps:

[0050] S1, fixing the metal sample to be tested for RRR value on the fixing plate 55;

[0051] S2, the voltage value of the metal sample measured at room temperature, recorded as U1;

[0052] S3, placing the measuring assembly 50 into the helium chamber 31;

[0053] S4, extracting the air in the helium chamber 31;

[0054] S5, filling helium into the helium chamber 31;

[0055] S6, adjusting the temperature in the helium chamber 31 to make it close to absolute zero, and measuring the voltage value of the metal sample at this time, which is recorded as U2;

[0056] S7, substitute U2 and U1 into the following formula:

[0057]

[0058] Here, RRR is the residual resistivity of the metal sample.

[0059] Example 1, use of the RRR value measuring device 10

[0060] 1. Fix the two ends of the metal sample to be tested for RRR value to the fixing members 561 of a fixing group 56;

[0061] 2. Connect the wire holder 53 to the voltage measuring device and measure the voltage of the metal sample on the fixing plate 55;

[0062] 3. Place the measuring assembly 50 into the helium chamber 31 from the top of the helium chamber 31;

[0063] 4. Use a vacuum extractor to draw vacuum from the first vacuum angle valve 34 and the second vacuum angle valve 38 respectively;

[0064] 5. Use a helium compressor to fill helium from the gas supply valve 35 into the helium chamber 31;

[0065] 6. The temperature of the helium chamber 31 is lowered by the cryogenic refrigerator 41 so that the temperature inside the helium chamber 31 approaches absolute zero, and the voltage of the metal sample on the fixing plate 55 is measured at this time;

[0066] 7. Substitute the two measured voltages into the formula to calculate the RRR value of the metal sample.

[0067] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A RRR value measuring device, characterized in that: The invention comprises a base assembly, a container assembly, a refrigeration assembly and a measuring assembly. The container assembly is fixedly mounted on the base assembly. The container assembly comprises a helium cavity for storing helium. The refrigeration assembly is mounted in the container assembly. The refrigeration end of the refrigeration assembly is connected to the helium cavity to reduce the temperature of the helium cavity. The measuring assembly is used to place a metal sample to be tested for RRR value into the helium cavity and measure the RRR value of the metal sample.

2. The RRR value measuring device according to claim 1, characterized in that: The base assembly includes a fixing frame, at least three hoofs and at least three first fixing rods, each hoof is evenly fixed on the bottom surface of the fixing frame for supporting the fixing frame, one end of each first fixing rod is fixedly connected to the top surface of the fixing frame, and the other end is fixedly connected to the outer edge of the container assembly for fixing the container assembly.

3. The RRR value measuring device according to claim 2, characterized in that: The container assembly also includes a vacuum cover and a cold shield. The outer side of the vacuum cover is fixedly connected to each first fixing rod. The cold shield is arranged in the vacuum cover. The helium cavity is arranged in the cold shield. A vacuum state is formed between the vacuum cover and the cold shield to prevent the cold shield from exchanging heat with the outside world.

4. The RRR value measuring device according to claim 3, characterized in that: The container assembly also includes a first vacuum angle valve, an air supply valve, a pressure gauge and a safety valve, wherein the first vacuum angle valve, the air supply valve, the pressure gauge and the safety valve are all arranged at the top of the helium chamber; the first vacuum angle valve is used to extract the air in the helium chamber, the air supply valve is used to replenish helium into the helium chamber, the pressure gauge is used to detect the air pressure in the helium chamber, and the safety valve is used to control the air pressure in the helium chamber and exhaust the air to the outside when the air pressure exceeds a predetermined pressure.

5. The RRR value measuring device according to claim 4, characterized in that: The container assembly further comprises a second vacuum angle valve, which is arranged on the vacuum cover and is used for evacuating the vacuum cover.

6. The RRR value measuring device according to claim 5, characterized in that: The refrigeration assembly includes a low-temperature refrigerator and a cold transfer chain. The low-temperature refrigerator extends into the vacuum cover from the top of the vacuum cover. The low-temperature refrigerator is provided with a first cold head and a second cold head. The first cold head is connected to the cold screen to reduce the temperature of the cold screen. One end of the cold transfer chain is connected to the second cold head, and the other end is connected to the helium cavity to reduce the temperature of the helium cavity.

7. The RRR value measuring device according to claim 6, characterized in that: The measuring assembly includes a fixing seat, at least three second fixing rods, a wire seat, at least one heat insulating member and a fixing plate. The bottom end of each second fixing rod is evenly installed on the top surface of the fixing seat, and the top end of each second fixing rod is fixedly connected to the bottom end of the wire seat. The heat insulating plates are arranged on each second fixing rod at the same intervals to separate the helium cavity so as to reduce the heat exchange between the bottom of the helium cavity and the outside world. The fixing plate is installed at the bottom end of the fixing seat and is used to place the metal sample to be tested for RRR value. The fixing plate is electrically connected to the wire seat, and the wire seat is electrically connected to the voltage measuring device to detect the voltage value of each metal sample on the fixing plate whose RRR value is to be tested.

8. The RRR value measuring device according to claim 7, characterized in that: The measuring assembly further comprises a plurality of fixing groups, each of which is evenly arranged on the fixing plate, and each of which comprises at least two symmetrically arranged fixing members for fixing the metal sample to be tested for RRR value onto the fixing plate.

9. The RRR value measuring device according to claim 6, characterized in that: The RRR value measuring device also includes a temperature control component, which includes a temperature sensor, a heater and a temperature controller. The temperature sensor is installed on the fixed plate and is used to measure the temperature in the helium cavity. The heater is installed on the second cold head and is used to increase the temperature of the helium cavity. The temperature controller is electrically connected to the temperature sensor, the cryogenic refrigerator and the heater, and is used to adjust the power of the cryogenic refrigerator and the heater according to the temperature detected by the temperature sensor to control the temperature in the helium cavity.

10. A measurement method based on the RRR value measurement device according to any one of claims 1 to 9, characterized in that: The following steps are involved: S1, fix the metal sample to be tested for RRR value on a fixing plate; S2, the voltage value of the metal sample measured at room temperature, recorded as U1; S3, placing the measuring assembly into the helium chamber; S4, extracting the air from the helium chamber; S5, filling the helium chamber with helium; S6, adjust the temperature in the helium chamber to make it close to absolute zero, and measure the voltage value of the metal sample at this time, which is recorded as U2; S7, substitute U2 and U1 into the following formula: Here, RRR is the residual resistivity of the metal sample.

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