JPH04301520A - Liquid level gauge - Google Patents

Abstract

PURPOSE:To provide a liquid level gauge which can obtain measuring results with few errors without requiring a complicate detecting device. CONSTITUTION:A sensor using a superconductive body has been impossible to measure the liquid level correctly because the temperature distribution in a liquefied gas container 1 is not uniform. When a pipe 3 is inserted into the container 1 and a sensor is inserted in this pipe 3, the temperature distribution in the periphery of the sensor becomes uniform. Therefore, a rod-like, a plate- like, or a linear sensor is inserted into the pipe and used as a liquid level gauge.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid level meter using a superconductor to detect the level of liquefied gas such as liquid nitrogen.

0002

[Prior Art] A liquid level meter that uses the electrical characteristics of a superconductor detects that the superconductor part in the liquid is in a superconducting state, while the part above the liquid surface is in a normal conducting state. The liquid level is determined from the length of the normal conduction state relative to the total length. Many proposals of this kind have already been made.

0003

Generally, the resistance value of an oxide superconductor used in a liquid level meter must decrease linearly as the temperature decreases, as shown in FIG. However, in reality, the temperature distribution within the liquid nitrogen container is not uniform, as shown in FIG. The vertical axis in FIG. 7 indicates temperature, and the horizontal axis indicates height from the bottom of the container. Reference numeral 71 indicates a case where the liquid level is 10 cm from the bottom of the container, and 72 indicates a case where the liquid level is 20 cm from the bottom of the container. The depth of the container in this case was 40 cm. Furthermore, the temperature distribution within the container also changes depending on the shape of the container, usage conditions, etc.

[0004] Therefore, when the liquid level position in a container is measured using a liquid level meter sensor made of an oxide superconductor in the form of a rod, a plate, or a film formed on a substrate, the output voltage is It changes in a complex manner depending on the height of the surface level. That is, the output voltage is not a value that is simply proportional to the height of the liquid level or a simple function value. Therefore, a complicated detection device is required, and measurement errors are likely to occur. The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a liquid level meter that can obtain measurement results with few errors using a simple device.

[0005]

[Means and operations for solving the problems] In order to achieve the above object, the present invention provides a liquid level meter that uses a superconductor to detect the liquid level position of liquefied gas. The sensor part for level detection was installed inside the tubular container. The tubular container may be made of metal, reinforced plastic, or other general materials, with an inner tube made of a material with high thermal conductivity and an outer tube made of a material with low thermal conductivity. Two types of composite tubes, two types of composite tubes in which the inner tube is made of copper or aluminum material and the outer tube is made of stainless steel or reinforced plastic material, and two or more types of composite tubes in which these are combined are used. This improved the temperature distribution around the sensor part and reduced measurement errors caused by temperature distribution above the liquid level in the liquefied gas container. Furthermore, the degree of improvement in temperature distribution is different when a reinforced plastic tube with relatively low thermal conductivity is used as the tubular container, and when a metal tube with relatively high thermal conductivity is used as the inner tube. The size increases in this order when two types of composite tubes are used, in which the outer tube is made of copper or aluminum material, which is a material with high thermal conductivity, and the outer tube is made of stainless steel or reinforced plastic material, which is a material with low thermal conductivity. The main reasons for this are as follows. When using a tube made of a material such as reinforced plastic, which has relatively low thermal conductivity, installing the sensor part for detecting the liquid level inside the tubular container will prevent the sensor part from being affected by the temperature distribution inside the liquefied gas container. The effects of heat inflow/outflow and gas convection within the container can be suppressed. In addition, when using a tube made of a material such as copper or aluminum that has a relatively high thermal conductivity, the tube itself has a high thermal conductivity, so the cooling effect of the liquefied gas existing in the liquefied gas container and the thermal conduction of the tube are affected. The effect works efficiently and the temperature distribution of the sensor part inside the pipe is improved. Furthermore, when two types of composite tubes or two or more types of composite tubes are used, the respective effects described above interact efficiently, and the temperature distribution in the sensor portion is extremely improved.

[0006]

[Embodiment] An embodiment will be described below with reference to the drawings. Figure 1
1 is a configuration diagram of an embodiment of a liquid level meter according to the present invention. In the figure, 1 is a container, and this container is filled with a liquefied gas 2 such as liquid nitrogen. Inside the liquefied gas, a double structure is installed in which an inner tube 4 is inserted into an outer tube 3, and a sensor portion 5 for detecting the liquid level is further provided inside the inner tube. The sensor part 5 includes a heating element and a superconductor film (not shown in FIG. 1), and a heating element power source 6 is connected to the heating element, and a liquid level measurement power source 7 is connected to the superconducting film. is connected. Note that an ammeter 9 is connected to the power source 7 for measuring the liquid level, and a voltmeter 8 is connected to the superconductor film.

FIG. 2 is an exploded configuration example of the sensor part for detecting the liquid level, and the ceramic substrate 21 has a thickness of 1 m.
It is an yttria-stabilized zirconia substrate with a width of 10 mm and a length of 160 mm, and a platinum heating element doped with zirconia as a heating element 22 is placed on the upper surface of this substrate with a thickness of 30 μm and a width of 1 m.
A zirconia-based film is placed on top of it as an insulator film 23, with a width of 6 mm at the output terminal of the heating element, and a width of 10 mm at other parts, a length of 160 mm, and a thickness of 5 mm.
It was formed to have a thickness of 0 μm. Furthermore, a Y-based oxide superconductor film 24 with a width of 3 mm and a length of 160 mm is formed as a superconductor film on the upper surface.
It was formed to have a thickness of 30 μm and a thickness of 30 μm. FIG. 3 is an enlarged view of the connection diagram, and the current and voltage at the superconductor part were measured using the four-terminal method, with a distance of 1 cm between the current introduction terminal and the voltage output terminal, and a distance of 30 cm at the liquid level detection part. In addition,
Each connection was made using conductive paste and ultrasonic solder.

FIG. 4 shows the results of measuring the relationship between the liquid level position in the liquid nitrogen container and the output voltage using the sensor of the liquid level meter constructed as described above. In Figure 4,
The vertical axis is the normalized output voltage, and the horizontal axis is the height of the liquid level from the bottom of the container. In the figure, 41 is when the sensor is used as it is, 42 is when the sensor is installed in a stainless steel pipe with an inner diameter of 10 mm, an outer diameter of 11 mm, and a length of 40 cm, and 43 is a case where the sensor is installed in a stainless steel tube with an inner diameter of 10 mm and an outer diameter of 1 mm.
Put it in a copper tube with a length of 1 mm and a length of 35 cm, and the outer tube has an inner diameter of 1 mm.
It shows the relationship between the liquid level position and the output voltage when installed in a double composite pipe made of stainless steel pipes with a diameter of 9 mm, an outer diameter of 20 mm, and a length of 40 cm.

[0009]The power input to the heating element is 5 to 10W,
The current input to the superconductor was 100 mA. From the above, when the sensor is used as it is (41), there is no simple linear relationship between the liquid level position and the output voltage, but when a double composite tube is used (43), there is an almost simple linear relationship (linear relationship). function relationship), and its characteristics have been significantly improved. or,
When a stainless steel tube was used (42), the characteristics were also improved to some extent.

FIG. 5 is a characteristic diagram illustrating the relationship between the liquid level position and temperature in each of the following cases in a liquid nitrogen container where the liquid level position is 10 cm from the bottom of the container. In the figure, 51 is the temperature distribution of the container as it is, and 52 is the inner diameter of 10 m.
m, temperature distribution inside a reinforced plastic pipe with an outer diameter of 14 mm and a length of 40 cm, 53 has an inner diameter of 10 mm and an outer diameter of 11 m.
m, temperature distribution in a stainless steel pipe with a length of 40 cm,
54 is an aluminum pipe with an inner diameter of 10 mm, an outer diameter of 12 mm, and a length of 35 cm, and an inner diameter of 10 mm, an outer diameter of 11 mm,
Temperature distribution in a copper pipe with a length of 35 cm, 55 is a copper pipe with an inner diameter of 10 mm, an outer diameter of 11 mm, and a length of 35 cm, and an outer pipe has an inner diameter of 19 mm, an outer diameter of 20 mm, and a length of 40 cm.
This figure shows the temperature distribution within a double composite pipe made of stainless steel material of 300 m. The length of the copper pipe and the aluminum pipe was 35 cm in order to suppress the inflow of heat from outside the container into the container through the pipe.

[0011] As is clear from the above explanation, temperature distribution can be improved by installing the sensor part of the liquid level meter inside the pipe, and the degree of this improvement is greater for reinforced plastic pipes, stainless steel pipes, and pipes made of stainless steel. Improvements were made in the order of aluminum and copper materials. In addition, in the case of a double-layered composite tube in which the inner tube is made of copper and the outer tube is made of stainless steel, the characteristics have been improved to almost satisfactory levels, and the temperature distribution within the tube is almost constant within the range where measurement errors can be ignored. I found out that it will happen.

0012

As explained above, according to the present invention, the sensor portion for detecting the liquid level formed using a superconductor is installed in a tubular container, so that the following effects can be achieved. ■ Temperature distribution is improved and the output voltage from the sensor is
Since it is approximately linearly proportional to the liquid level position, the processing device etc. for making the output voltage correspond to the liquid level position can be simplified. ■ It is possible to reduce measurement errors caused by changes in temperature distribution due to the shape of the liquefied gas container such as liquid nitrogen or the position of the liquid level, and changes in the resistance value of the superconductor due to temperature changes. ■ It also serves as a sensor protection tube for the tube where the sensor is installed.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of an embodiment of a liquid level meter according to the present invention.

FIG. 2 is an exploded configuration example diagram of a sensor portion for detecting liquid level.

FIG. 3 is an enlarged diagram showing the connection relationship of the liquid level meter.

FIG. 4 is a diagram showing the relationship between the liquid level position in the liquid nitrogen container and the output voltage.

FIG. 5 is a diagram showing how the surrounding temperature changes depending on the liquid level position in a liquid nitrogen container.

FIG. 6 is a diagram showing how the resistance value of an oxide superconductor changes as the temperature decreases.

FIG. 7 is a diagram showing the temperature distribution inside the liquid nitrogen container.

[Explanation of symbols]

1 Container 2 Liquefied gas 3 Outer tube 4 Inner pipe 5　Sensor part 6 Power supply for heating element 7 Power supply for liquid level measurement 8 Voltmeter 9 Ammeter

Claims (6)

[Claims] Claim 1: A liquid level meter that detects the liquid level position of liquefied gas using a superconductor, characterized in that a sensor part for detecting the liquid level formed using the superconductor is installed in a tubular container. Liquid level meter. 2. The liquid level meter according to claim 1, wherein the sensor portion for detecting the liquid level is installed inside a metal pipe. 3. The liquid level meter according to claim 1, wherein the sensor portion for detecting the liquid level is installed inside a pipe made of reinforced plastic. [Claim 4] A claim characterized in that the sensor part for detecting the liquid level is installed in a double composite pipe in which the inner pipe is made of a material with high thermal conductivity and the outer pipe is made of a material with low thermal conductivity. The liquid level meter described in item 1. 5. The liquid level meter according to claim 4, wherein the inner tube is made of copper or aluminum material, and the outer tube is made of stainless steel or reinforced plastic material. 6. The liquid level meter according to claim 1, wherein the sensor portion for detecting the liquid level is installed in a double or more composite pipe.