Correction calculation method

Abstract

The present invention aims to easily calculate a calibration formula for calibrating a liquid hydrogen level gauge using a superconductor at low cost without using expensive liquid hydrogen. [Solution] A calibration equation calculation method for calculating a calibration equation to calibrate a liquid hydrogen level gauge that uses a superconductor to detect the liquid hydrogen level in a container by voltage measurement, the method being characterized in that the calibration equation is calculated from the relationship between the voltage value of the liquid hydrogen level gauge and each liquid level height at at least three points with different liquid level heights while pouring liquid having a temperature higher than the critical temperature (Tc) of the superconductor used in the liquid hydrogen level gauge into the container in which the liquid hydrogen level gauge is installed vertically.

Description

[Technical field]

[0001] The present invention relates to a calibration equation calculation method for calculating a calibration equation for calibrating a liquid hydrogen level gauge using a superconductor. [Background technology]

[0002] In February 2023, the Cabinet decided on the "Basic Policy for the Realization of Green Transformation (GX)" in Japan, which calls for the promotion of hydrogen introduction. As a result, there is a demand for accurate measurement of the amount of liquid hydrogen during its transportation, storage, and consumption. In this context, efforts are underway to develop liquid hydrogen level gauges using superconductors such as MgB2.

[0003] To actually use a liquid hydrogen level gauge, it is necessary to calibrate the voltage measurement of the gauge with the actual liquid hydrogen level, but using liquid hydrogen for calibration is costly, and building a liquid hydrogen facility in-house is not realistic due to strict applicable laws such as the High Pressure Gas Safety Act, the Industrial Safety and Health Act (Explosion-Proof Construction Standards for Electrical Machinery and Equipment), and the Fire Service Act.On the other hand, there are very few testing facilities that can test liquid hydrogen, and it is difficult to easily obtain an environment in which to test and calibrate a liquid hydrogen level gauge.

[0004] Patent Document 1 describes the configuration of a level gauge for liquefied gas such as liquid nitrogen, in which a superconductor and a non-superconductor are arranged in parallel. [Prior art documents] [Patent documents]

[0005] Patent document 1: Japanese Patent Application Laid-Open No. 04-99923 Summary of the Invention [Problem to be solved by the invention]

[0006] However, Patent Document 1 does not describe how to calibrate the voltage measurement value in the level gauge to the actual liquid level of the liquefied gas. If the liquefied gas is liquid hydrogen, not only is the cost high as described above, but in-house calibration is difficult due to legal requirements.

[0007] An object of the present invention is to solve the above problems and to easily calculate, at low cost, a calibration equation for calibrating a liquid hydrogen level gauge using a superconductor. [Means for solving the problem]

[0008] In order to solve the above problems, the present invention provides a calibration equation calculation method for calculating a calibration equation for calibrating a liquid hydrogen level gauge that uses a superconductor to detect the liquid hydrogen level in a container by voltage measurement, characterized in that the calibration equation is calculated from the relationship between the voltage of the liquid hydrogen level gauge and each liquid level height at at least three points where the liquid level gauge is installed vertically while pouring liquid having a temperature higher than the critical temperature (Tc) of the superconductor used in the liquid hydrogen level gauge into the container in which the liquid hydrogen level gauge is installed vertically.

[0009] With this configuration, the calibration formula for calibrating a liquid hydrogen level gauge using a superconductor can be calculated easily and at low cost without using expensive liquid hydrogen. Also, the calibration test can be performed not visually but with other general types of level gauge.

[0010] In order to solve the above problems, the present invention provides a calibration equation calculation method for calculating a calibration equation for calibrating a liquid hydrogen level gauge using a superconductor that detects the liquid hydrogen level in a container by voltage measurement, comprising: While pouring liquid having a temperature higher than the critical temperature (Tc) of the superconductor used in the liquid hydrogen level gauge into the vessel in which the liquid hydrogen level gauge is vertically installed, measuring a third voltage of the liquid hydrogen level gauge when the liquid level is 0% and a first voltage of the liquid hydrogen level gauge when the liquid level is 100%, and measuring a second voltage of the liquid hydrogen level gauge at at least one liquid level between 0% and 100%; The present invention provides a calibration equation calculation method, which is characterized by calculating a calibration equation from the relationships between the values ​​of the first voltage, the second voltage, and the third voltage and the respective liquid level heights.

[0011] With this configuration, the calibration formula for calibrating a liquid hydrogen level gauge using a superconductor can be calculated easily and at low cost without using expensive liquid hydrogen. Also, the calibration test can be performed not visually but with other general types of level gauge.

[0012] In the calibration formula calculation method, the liquid hydrogen level gauge may include a superconducting wire and a non-superconducting wire of the same length, the first voltage is the voltage of the non-superconducting wire at a 100% liquid level, and the second voltage is a voltage obtained by subtracting the voltage of the superconducting wire at a 100% liquid level and at any liquid level between 100% and 0% from the voltage of the non-superconducting wire at a 100% liquid level.

[0013] This configuration makes it possible to prevent measurement errors caused by temperature changes in the gas phase.

[0014] In the calibration equation calculation method, the liquid injected into the container may be liquid nitrogen.

[0015] With this configuration, it is possible to calculate a calibration equation for calibrating a liquid hydrogen level gauge using a superconductor easily and at low cost using liquid nitrogen, which is readily available, easy to handle, and low cost.

[0016] In the calibration equation calculation method, the second voltage may be a voltage of the liquid hydrogen level gauge when the liquid level is 50%.

[0017] With this configuration, the liquid level at which the second voltage is measured is halfway between the 100% liquid level and the 0% liquid level, making it possible to calculate a more accurate calibration equation. Effect of the Invention

[0018] The calibration equation calculation method of the present invention makes it possible to easily calculate a calibration equation for calibrating a liquid hydrogen level gauge using a superconductor at low cost. Although it is difficult to measure liquid hydrogen with other general level gauges, the use of easy-to-handle liquid nitrogen makes it possible to carry out a comparative test with the liquid level measured with other level gauges. [Brief description of the drawings]

[0019] [Figure 1] FIG. 2 is a diagram for explaining an installation state of a liquid hydrogen level gauge in the first embodiment of the present invention. [Diagram 2] FIG. 2 is a diagram illustrating a state in which 50% of a liquid is poured into a container in the first embodiment of the present invention. [Diagram 3] FIG. 2 is a diagram illustrating a state in which 100% of liquid is poured into a container in the first embodiment of the present invention. [Figure 4] FIG. 11 is a diagram for explaining an installation state of a liquid hydrogen level gauge in the second embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS EXAMPLES

[0020] A first embodiment of the present invention will be described with reference to Figs. 1 to 3. Fig. 1 is a diagram for explaining an installation state of a liquid hydrogen level gauge in the first embodiment of the present invention. Fig. 2 is a diagram for explaining a state when 50% of the liquid is poured into a container in the first embodiment of the present invention. Fig. 3 is a diagram for explaining a state when 100% of the liquid is poured into a container in the first embodiment of the present invention.

[0021] (Liquid hydrogen level gauge) First, the liquid hydrogen level gauge 10 in the first embodiment will be described. The liquid hydrogen level gauge 10 has a superconducting wire 11 and a non-superconducting wire 12 arranged in parallel with each other and of the same length. A current is passed through each end of the wires to measure the voltage, and the liquid level is detected from the measured voltage by utilizing the fact that the liquid becomes superconducting below the liquid surface and the resistance becomes zero. The superconducting wire 11 and the non-superconducting wire 12 are both long core wires with a length of about 1 m and a diameter of about 0.3 mm, and are covered with a metal coating. The superconductor contained in the superconductor 11 is a mixture of magnesium (Mg) of 325 mesh (manufactured by alfa Aesar, particle size about 44 μm) and boron (B) of an average particle size of 14 μm in a molar ratio of 1 part (mixing process), which is drawn in a wire drawing process, and then sintered to form a superconductor of MgB2. In the wire drawing process, the powdered mixture of Mg and B obtained in the mixing process was placed in a single tube and drawn into a long shape. The critical temperature (Tc) of the superconductor manufactured in this way is about 32K to about 34K.

[0022] In the first embodiment, a long core wire having a length of about 1 m and a diameter of about 0.3 mm is formed, but this is not necessarily limited to this and can be changed as appropriate. For example, the length may be about 5 m or 0.5 m, and it may be created according to the depth of the liquid hydrogen in the container. In the first embodiment, the diameter is about 0.3 mm, but this is not necessarily limited to this and can be changed as appropriate. For example, it may be 0.5 mm or 0.2 mm, and the diameter may be selected in consideration of the critical temperature (Tc).

[0023] The coating metal may be any metal having high conductivity. Although a CuNi alloy was used in the first embodiment, other metals such as stainless steel may also be used.

[0024] The non-superconducting wire 12 is made of a non-superconducting metal having the same length and thickness as the above-mentioned superconducting wire, and is covered with a metal coating of a CuNi alloy. The non-superconducting metal in the first embodiment can be any normal conductor.

[0025] When the container 20 is filled with 50% liquid hydrogen as shown in FIG. 2, the portion of the superconducting wire 11 that is immersed in the liquid hydrogen becomes superconducting, so the voltage V between the AC AC When the voltage V between A and B is measured, the voltage V AB However, since the resistance value changes with the temperature change of the non-superconducting gas phase, the voltage V AB Therefore, the voltage V of the superconducting wire 11 changes from the voltage V of the non-superconducting wire 12. AC By subtracting this, the voltage V of the superconducting wire 11, whose gas phase has the same temperature distribution, is AB and the voltage at the same liquid level in non-superconducting wire 12 are cancelled out, leaving only voltage Vbc in non-superconducting wire 12. Since the temperature in the liquid is constant, the liquid level can be detected by calculating voltage Vbc.

[0026] (Calibration of liquid hydrogen level gauge using liquid hydrogen) To accurately measure the liquid level using liquid hydrogen level gauge 10, it is necessary to obtain a calibration equation for calibrating the difference between the voltage Vbc of non-superconducting wire 12 (output voltage of liquid hydrogen level gauge 10) and the actual liquid level. For this reason, liquid hydrogen level gauge 10 is usually placed in a container that can be seen from the outside, and after liquid hydrogen (Tc = 20 to 30 K) is poured into the container, the liquid level is visually confirmed on the scale as the liquid evaporates and the liquid level drops, and a calibration equation is calculated for calibrating the visual liquid level and the output voltage of liquid hydrogen level gauge 10.

[0027] Calibrating the liquid hydrogen level gauge 10 using liquid hydrogen has the following problems. Liquid hydrogen is very expensive. There are very few test sites nationwide that can perform tests with liquid hydrogen. Constructing liquid hydrogen equipment on one's own is difficult in terms of time and cost due to strict applicable laws and regulations such as the High Pressure Gas Safety Act, the Industrial Safety and Health Act (Explosion-Proof Construction Standards for Electrical Machinery and Equipment), and the Fire Service Act.

[0028] Therefore, the applicant has found a method for calculating a calibration equation for calibrating the liquid hydrogen level gauge 10 using a liquid other than liquid hydrogen, which is low cost and has few applicable laws and regulations. Next, a calibration equation calculation method for calculating the calibration equation for calibrating the liquid hydrogen level gauge in the first embodiment of the present invention will be described.

[0029] (Calibration formula calculation method without using liquid hydrogen) First, as shown in Fig. 1, a liquid hydrogen level gauge 10 is installed vertically in a container 20. At this time, the length of the liquid hydrogen level gauge 10 is set so that the liquid level height can be measured even if the container 20 is filled with 100% liquid.

[0030] Next, when no liquid is poured in (liquid level is 0%), a voltage is applied to both ends of the superconducting wire 11, and the voltage V between points A and C is measured. AC At this time, the voltage when the superconducting wire 11 is not superconducting is measured. Then, the voltage V of the superconducting wire 11 is measured. AC Subtracting the voltage Vac of the non-superconducting wire from this results in zero, and the measured voltage at 0% liquid level is zero.

[0031] Next, liquid 30 having a temperature higher than the critical temperature (Tc) of the superconductor used in liquid hydrogen level gauge 10 is poured into the container to a height of 50% (point B in FIG. 2). The critical temperature (Tc) of the superconductor in Example 1 is about 32 K to about 34 K, and the liquid poured into container 20 in Example 1 is liquid nitrogen (boiling point at 1 atmosphere=77 K).

[0032] At this time, since the liquid is liquid nitrogen (boiling point at 1 atmosphere = 77 K), the superconducting wire 11 in the liquid phase is not superconducting, and the voltage V AC When the voltage V of the superconducting wire 11 between points B and C is measured, BC is not zero and the voltage in the non-superconducting state is measured, but V BC If we intentionally set to zero, we get the same V as in the superconducting state. AC That is, the voltage V between points a and c of the non-superconducting wire 12 and the voltage V between points A and B of the superconducting wire 11 can be measured. AB By subtracting this, the voltage Vbc of the non-superconducting wire 12 is obtained, which is the same as when the liquid surface (liquid phase portion) of the superconducting wire 11 is in a superconducting state.

[0033] Next, liquid with a temperature higher than the critical temperature (Tc) of the superconductor used in the liquid hydrogen level gauge 10 is poured into the container up to a height of 100% (point A in FIG. 3), and the voltage Vac between points a and c of the non-superconducting wire 12 is measured.

[0034] Finally, a calibration equation, which is an approximation equation, is calculated by the least squares method or the like from the relationship between the three points of zero voltage (third voltage) when the liquid level is 0%, voltage Vbc (second voltage) of non-superconducting wire 12 when the liquid level is 50%, and voltage Vac (first voltage) of non-superconducting wire 12 when the liquid level is 100% and each of the liquid level heights. The liquid level height can be obtained by measuring with a separate liquid level gauge.

[0035] In the first embodiment, point B shown in Fig. 2 is set to a height of 50% of the liquid level, but it is not necessarily limited to this and can be changed as appropriate. For example, it may be a height of 30% of the liquid level, a height of 70% of the liquid level, or any height between a height of 0% of the liquid level and a height of 100% of the liquid level. Also, point B does not have to be one point, and multiple points B can be set between a height of 0% of the liquid level and a height of 100% of the liquid level to calculate the calibration formula.

[0036] Furthermore, in the first embodiment, the calibration formula is calculated from the voltage at 0% liquid level, 100% liquid level, and 50% liquid level, but this is not necessarily limited to this and can be changed as appropriate. For example, the calibration formula may be calculated as an approximation formula from the relationship between the voltage values ​​at three arbitrary points with different liquid level heights between 0% liquid level and 100% liquid level and each liquid level height.

[0037] In addition, in the first embodiment, the liquid 30 injected into the container 20 is liquid nitrogen, but this is not necessarily limited to this and can be changed as appropriate. For example, it may be a liquefied gas such as liquefied carbon dioxide, or it may be water as long as the water temperature is stable, or any liquid having a temperature higher than the critical temperature (Tc) of the superconductor used in the liquid hydrogen level gauge 10.

[0038] Thus, in the first embodiment, a calibration equation calculation method for calculating a calibration equation for calibrating a liquid hydrogen level gauge using a superconductor that detects the liquid hydrogen level in a container by voltage measurement is provided, which includes the steps of: While pouring liquid having a temperature higher than the critical temperature (Tc) of the superconductor used in the liquid hydrogen level gauge into the vessel in which the liquid hydrogen level gauge is vertically installed, The calibration equation calculation method, which is characterized by calculating the calibration equation from the relationship between the voltage value of the liquid hydrogen level gauge at at least three points with different liquid level heights and each liquid level height, makes it possible to easily calculate the calibration equation for calibrating a liquid hydrogen level gauge using a superconductor at low cost without using expensive liquid hydrogen. Also, although it is difficult to measure liquid hydrogen with other general types of level gauges, using easy-to-handle liquid nitrogen makes it possible to perform comparative tests with the liquid level height measured with other types of level gauges.

[0039] Also, there is provided a calibration equation calculation method for calculating a calibration equation for calibrating a liquid hydrogen level gauge using a superconductor that detects the liquid hydrogen level in a container by voltage measurement, comprising the steps of: While pouring liquid having a temperature higher than the critical temperature (Tc) of the superconductor used in the liquid hydrogen level gauge into the vessel in which the liquid hydrogen level gauge is vertically installed, measuring a third voltage of the liquid hydrogen level gauge when the liquid level height is 0% and a first voltage of the liquid hydrogen level gauge when the liquid level height is 100%, and also measuring a second voltage of the liquid hydrogen level gauge at at least one liquid level height between 0% and 100%; By using the calibration equation calculation method, which is characterized by calculating the calibration equation from the relationship between the values ​​of the first voltage, the second voltage, and the third voltage and the respective liquid level heights, the calibration equation for calibrating a liquid hydrogen level gauge using a superconductor can be calculated easily and at low cost without using expensive liquid hydrogen. In addition, although it is difficult to measure liquid hydrogen with a general level gauge of other types, by using liquid nitrogen, which is easy to handle, a comparative test with the liquid level measured with a level gauge of other types is possible. EXAMPLES

[0040] A liquid hydrogen level gauge 110 in the second embodiment of the present invention differs from the first embodiment in that it does not have a non-superconducting wire and is composed only of a superconducting wire. The second embodiment will be described with reference to Fig. 4. Fig. 4 is a diagram for explaining the installation state of the liquid hydrogen level gauge in the second embodiment of the present invention.

[0041] The liquid hydrogen level gauge 110 in the second embodiment does not include a non-superconducting wire, but has a superconducting wire 111. The superconducting wire 111 has the same configuration as in the first embodiment, and detects the liquid hydrogen level by measuring the voltage. Since the liquid hydrogen level gauge 110 does not include a non-superconducting wire, there is a risk of errors occurring due to temperature changes in the gas phase. For this reason, it is mainly used in environments where the temperature of the gas phase can be kept constant.

[0042] A method for calculating the calibration formula will be described below. First, as shown in Fig. 4, a liquid hydrogen level gauge 110 is installed vertically in the container 20. At this time, the length of the liquid hydrogen level gauge 110 is set so that the liquid level height can be measured even if the container 20 is filled with 100% liquid.

[0043] Next, the voltage V across the superconducting wire 111 when no liquid is poured in (liquid level 0%) AC is not measured and is set to zero.

[0044] Next, a liquid having a temperature higher than the critical temperature (Tc) of the superconductor used in the liquid hydrogen level gauge 110 is poured into the container up to a height of 50% (point B). The critical temperature (Tc) of the superconductor in the second embodiment is about 32K to about 34K. The liquid poured into the container 20 is liquid nitrogen (77K), but is not limited to this and can be changed as appropriate. For example, it may be a liquefied gas such as liquefied carbon dioxide gas, or water as long as the water temperature is stable. Any liquid having a temperature higher than the critical temperature (Tc) of the superconductor used in the liquid hydrogen level gauge 110 may be used.

[0045] At this time, since the liquid is liquid nitrogen, the superconducting wire 111 in the liquid phase is not superconducting, and the voltage V between points A and C AC When the voltage V of the superconducting wire 111 between points B and C is measured,BC is not zero and the voltage in the non-superconducting state is measured, but V BC If we intentionally set to zero, we get the same V as in the superconducting state. AC That is, the voltage V of the superconducting wire 111 at the liquid level B can be measured. AB Measure.

[0046] Next, liquid having a temperature higher than the critical temperature (Tc) of the superconductor used in the liquid hydrogen level gauge 110 is poured into the container up to a height of 100% (point A). Then, the voltage V between points A and C of the superconducting wire 111 is AC When measuring the voltage, it is advisable to connect an appropriate current source.

[0047] Finally, the voltage V between points A and B of the superconducting wire 111 at 0% liquid level and 50% liquid level (point B) is zero. AB , the voltage V between points A and C of the superconducting wire 111 when the liquid level is 100% (point A) AC The calibration formula for calibration is calculated by approximating the relationship between the voltage values ​​at the three points and the respective liquid level heights using the least squares method or the like.

[0048] In the second embodiment, point B shown in FIG. 4 is set to a height of 50% of the liquid level, but this is not necessarily limited to this and can be changed as appropriate. For example, it may be set to a height of 30% of the liquid level, or a height of 70% of the liquid level, or any height between a height of 0% of the liquid level and a height of 100% of the liquid level. Also, point B does not have to be one point, and multiple points B can be set between a height of 0% of the liquid level and a height of 100% of the liquid level to calculate the calibration formula.

[0049] Furthermore, in the second embodiment, the calibration formula is calculated from the voltage at 0% liquid level, 100% liquid level, and 50% liquid level, but this is not necessarily limited to this and can be changed as appropriate. For example, the calibration formula may be calculated from the relationship between the voltage values ​​at three arbitrary points with different liquid level heights between 0% liquid level and 100% liquid level and each liquid level height.

[0050] In this way, in the second embodiment, a calibration equation calculation method for calculating a calibration equation for calibrating a liquid hydrogen level gauge using a superconductor that detects the liquid hydrogen level in a container by voltage measurement is also provided, While pouring liquid having a temperature higher than the critical temperature (Tc) of the superconductor used in the liquid hydrogen level gauge into the vessel in which the liquid hydrogen level gauge is vertically installed, The calibration equation calculation method, which is characterized by calculating the calibration equation from the relationship between the voltage value of the liquid hydrogen level gauge at at least three points with different liquid level heights and each liquid level height, makes it possible to easily calculate the calibration equation for calibrating a liquid hydrogen level gauge using a superconductor at low cost without using expensive liquid hydrogen. Also, although it is difficult to measure liquid hydrogen with other general types of level gauges, using easy-to-handle liquid nitrogen makes it possible to perform comparative tests with the liquid level height measured with other types of level gauges.

[0051] Also, there is provided a calibration equation calculation method for calculating a calibration equation for calibrating a liquid hydrogen level gauge using a superconductor that detects the liquid hydrogen level in a container by voltage measurement, comprising the steps of: While pouring liquid having a temperature higher than the critical temperature (Tc) of the superconductor used in the liquid hydrogen level gauge into the vessel in which the liquid hydrogen level gauge is vertically installed, measuring a third voltage of the liquid hydrogen level gauge when the liquid level is 0% and a first voltage of the liquid hydrogen level gauge when the liquid level is 100%, and measuring a second voltage of the liquid hydrogen level gauge at at least one liquid level point between 0% and 100%; By using the calibration equation calculation method, which is characterized by calculating the calibration equation from the relationship between the values ​​of the first voltage, the second voltage, and the third voltage and the respective liquid level heights, the calibration equation for calibrating a liquid hydrogen level gauge using a superconductor can be calculated easily and at low cost without using expensive liquid hydrogen. In addition, although it is difficult to measure liquid hydrogen with a general level gauge of other types, by using liquid nitrogen, which is easy to handle, a comparative test with the liquid level measured with a level gauge of other types is possible. [Industrial Applicability]

[0052] The calibration equation calculation method of the present invention can be widely applied to the field of liquid hydrogen level gauges. [Explanation of symbols]

[0053] 10: Liquid hydrogen level gauge 11:Superconducting wire 12: Non-superconducting wire 20: Container 30:Liquid 110: Liquid hydrogen level gauge 111:Superconducting wire

Claims

1. A calibration equation calculation method for calculating a calibration equation for calibrating a liquid hydrogen level gauge using a superconductor that detects the liquid hydrogen level in a container by voltage measurement, comprising: While pouring liquid having a temperature higher than the critical temperature (Tc) of a superconductor used in the liquid hydrogen level gauge into the vessel in which the liquid hydrogen level gauge is vertically installed, A calibration equation calculation method, comprising the steps of: calculating a calibration equation from the relationship between the voltage values ​​of the liquid hydrogen level gauge at at least three points each having a different liquid level height and each of the liquid level heights.

2. A calibration equation calculation method for calculating a calibration equation for calibrating a liquid hydrogen level gauge using a superconductor that detects the liquid hydrogen level in a container by voltage measurement, comprising: While pouring liquid having a temperature higher than the critical temperature (Tc) of a superconductor used in the liquid hydrogen level gauge into the vessel in which the liquid hydrogen level gauge is vertically installed, measuring a third voltage of the liquid hydrogen level gauge when the liquid level is 0% and a first voltage of the liquid hydrogen level gauge at a liquid level when the liquid level is 100%, and also measuring a second voltage of the liquid hydrogen level gauge at at least one liquid level between 0% and 100%; A calibration equation calculation method, comprising: calculating a calibration equation from the relationship between the values ​​of the first voltage, the second voltage, and the third voltage and each of the liquid level heights.

3. 3. The calibration equation calculation method according to claim 2, wherein the liquid hydrogen level gauge includes a superconducting wire and a non-superconducting wire of the same length, the first voltage is a voltage at a 100% liquid level of the non-superconducting wire, and the second voltage is a voltage obtained by subtracting a voltage of the superconducting wire at an arbitrary liquid level between 100% and 0% of the liquid level of the superconducting wire from a voltage at a 100% liquid level of the non-superconducting wire.

4. 4. The calibration equation calculation method according to claim 1, wherein the liquid injected into the container is liquid nitrogen.

5. 4. The calibration equation calculation method according to claim 2, wherein the second voltage is a voltage of the liquid hydrogen level gauge when the liquid level is 50%.

Images