JPS6064220A - Liquid-level detecting device for low temperature liquid - Google Patents

Abstract

PURPOSE:To reduce the amount of evaporation of a low temperature liquid utmost and to detect the liquid level accurately, by independently providing a current feeding wiring and a voltage wiring for each resistor element, and selectively switching each terminal to a power source and a voltage measuring device. CONSTITUTION:A plurality of, e.g., five, carbon resistor elements 1-5 are arranged in a low temperature liquid and over the surface of the liquid. A current feeding wiring 21 and a voltage measuring wiring 22 are independently provided for each element. In order to find the liquid level, switching devices 61 and 63 are operated, a current is fed to the resistor elements, 5 and 4 from a power source 60, and each voltage is measured by a voltage measuring device 62 at first. When voltages are equal, the current is fed to the resistor elements 4 and 3, and each voltage is measured. This procedure is sequentially repeated downward. When both voltages are different, the liquid surface is located between the resistor elements, e.g., 3 and 2. Since the current is not fed to the unnecessary resistor elements, useless evaporation of the low temperature liquid can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a device for detecting the level of a low-temperature liquid that easily evaporates even with slight heating.

[Technical background of the invention and its problems]

In cryogenic engineering, a cryogenic liquid is defined as a liquid with a temperature of -150'0 or less, but the present invention is not limited to this, and may include liquid helium, liquid oxygen, liquid nitrogen, liquid hydrogen, and other liquefied gases. C2 Liquids that easily evaporate with slight heating will be referred to as low-temperature liquids.

A low temperature liquid level detection device detects when the low temperature liquid stored in a container evaporates and gradually decreases in volume due to heat intrusion from the outside or heat generation inside, or when the low temperature liquid is replenished from the outside. This device determines the remaining amount of low-temperature liquid in the container by detecting the level of the low-temperature liquid when the amount increases.

FIG. 1 is a schematic vertical cross-sectional view of a low temperature liquid level detection device showing a portion common to the conventional device and an embodiment of the present invention.

A liquid helium tank (11J is a container for storing a low-temperature liquid (liquid helium in this case) is liquid helium 02
In order to reduce the amount of evaporation, the space between the outer container (2) and the outer container (2) is evacuated and surrounded by a vacuum insulation layer A4. It is surrounded by a radiation shield plate (1!9) which is cooled by winding a cooling pipe (not shown).

Oe is a liquid helium inlet (171 is a gas helium outlet).A support scoop made of electrical and thermal insulating pipes is attached to the upper lid of the liquid helium tank aD, and the liquid helium is injected into the liquid helium tank. Insert it to near the bottom of tank 011.The outer circumference of the support member (1'l is marked with numbers (1) to () from the bottom).
Carbon resistance elements α shown in 5) are arranged at intervals. QO indicates the liquid level.

Conventionally, as shown in Fig. 2, current supply wiring 01)
Connect each resistance element (1) to (5) in series, connect a power supply (not shown) to the terminal (to), and apply a predetermined current to each resistance element (11 to (5)). The voltage can be measured by connecting a voltage measuring device (not shown) between the terminals 60 and 6, between the voltage measurement wiring (lead at 24, and each terminal 60.6I), between 6 and 6, etc. Each of these wiring lines Qυ is led out through the pipe of the support member Ql.

The carbon resistance element Qdl has a different resistance value depending on the temperature when it comes out from the surface of liquid helium (13) and when it is immersed in the liquid, so when the same predetermined current is passed, the resistance The applied voltages of elements (1), (2) and (3) to (5) are different. Therefore, if these applied voltages are compared, it will be found that the second resistance element (2) and the third resistance element ( 3)
It can be seen that there is a liquid level between

By the way, in the conventional measurement wiring diagram shown in FIG. 2, when a current of, for example, 20 mA is passed between the terminals (to) and 431), the first . The second resistive elements (1) and (2) (2 are each applied with a voltage of 8 µm, and the 3rd to
It is assumed that a voltage of 5cm is applied to each of the fifth resistance elements (3) to (5). As a result, the liquid level position is changed between the second resistance element (2) and the third resistance element (2) as described above.
3), but in this case, it is the second and third resistance elements (2) that detect the liquid level.
), (3), and other resistive elements (1), (4
) and (5) are not directly involved in liquid level detection. However, since current is flowing, it generates heat and increases the evaporation loss of liquid helium (1,11), which is a serious drawback.When we calculate the power involved in this heat generation, we find that it is difficult to detect the liquid level. The second and third resistance elements directly involved (
The heat generation in 2) and (3) is 20 mA x 8 V =
0.160 Watt20 mA x 5 V = O
, ] QOOWatt, and the total is 0.260Watt
It is. Resistance element not directly involved in liquid level detection (1)
, (4), (5) power is 20 mA x 8 V =
0.160 Watt2
)=0.200Watt, and this total is 0.360
This is Watt. Due to the heat generated by this wasteful 0.360 Watt of electricity, liquid helium is heated at approximately 0.5 watts per hour.
04J will be evaporated in vain.

In addition, if the moving height range of the liquid helium level (A) in the container is large, it will be necessary to install a large number of carbon resistance elements (1ω) along this moving height range. Level detection C: The number of resistance elements that are directly involved remains two, but the number of resistance elements that are not directly involved increases accordingly, so the wasteful heat generated by the liquid level detection device increases significantly, and the amount of wasteful heat generated by the liquid helium increases. A significant drawback was that evaporation was also significantly increased.

In addition, such wasteful evaporation of liquid helium can be avoided even if the moving height range of the liquid level is not wide, and if you want to detect the liquid level with high accuracy, it is necessary to arrange a large number of carbon resistance elements (irjI) closely. As the need arises, there is also the same serious drawback of a significant increase.

In addition, a power supply (
The load on both sides also increases, which causes the current to flow to become unstable, making it difficult to pass the desired constant current, and the detection voltage also becoming unstable, resulting in unclear liquid level detection. there were.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a low-temperature liquid level detection device that can accurately detect the liquid level while minimizing the amount of evaporation of the low-temperature liquid.

[Summary of the invention]

In the present invention, a plurality of resistance elements are arranged in the low-temperature liquid and above the liquid surface, a predetermined current is passed through the resistance elements, and the voltage of each resistance element required to flow the current is measured. In a low-temperature liquid level detection device that detects the liquid level based on changes in the liquid level, each resistance element is independently provided with a current supply wiring and a voltage measurement wiring, and a node 11 of each current supply wiring and voltage measurement wiring is provided. It is characterized by having a power supply switching device and a measurement voltage switching device that selectively switch the power supply and voltage measurement device, respectively, and it is possible to use only two resistive elements sandwiching the liquid surface, or one at the top in the liquid. By passing current through only one resistive element and measuring the voltage, we can measure the voltage change due to the change in the voltage applied to two resistive elements or when the resistive element in the liquid is above the liquid surface (1). This makes it possible to detect the liquid level and not energize other resistance elements, thereby preventing unnecessary evaporation of the low-temperature liquid.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIGS. 3 and 4. The schematic vertical cross-sectional view of this device is as follows:
This is as shown in FIG. 1 described in the background art section, so please refer to this as well. FIG. 3 is a block diagram of this device, and FIG. 4 is a terminal layout diagram of the wiring shown in FIG.

In this example, five carbon resistance elements (1) to
(5) are each independently provided with a current supply wiring 0υ and a voltage measurement wiring (27J), each current supply wiring (21) is provided with a terminal (41-(4), and each voltage measurement wiring (22 are each provided with a terminal (50~axis).Terminal f4 (l-(49) of the current supply wiring is selectively connected to the power supply (60) and selectively connected to each resistance element (1)~(5). It is installed in the power supply switching device (61) that allows current to flow.The voltage measurement wiring (two terminals (A) to 6gl are selectively connected to the two voltage measurement devices (62) and (62). connection,
It is arranged in a measurement voltage switching device R (63) for selectively measuring the voltage of each resistance element (1) to (5). A switching interlocking device (64) is provided to interlock the power switching device (61) and the measurement voltage switching device (63).

Next, the effect will be explained.

The liquid level can be determined using the apparatus of this embodiment as follows. Each of the switching devices (61) and (63) is operated, and a predetermined current is initially passed through the fifth and fourth resistance elements (5) and (4) to measure their respective voltages. If both voltages are equal, then pass a predetermined current through $4 and the (3) resistance element (4), (5) and measure each voltage. If the voltages are different, it is detected that there is a liquid level (2) between the resistive elements, the third and second resistive elements (3) and (2) in Figure 1. The measurements may be made sequentially upward from the element.

Once the liquid level is detected, a current is continuously applied only to the resistance elements (2) and (3) that sandwich the liquid level e1, and the voltage continues to be measured. Then, if both voltages become equal on the lower side, both resistance elements (2) and (3) are connected to the liquid level (2) (3).
) and stop the voltage measurement of the second and first resistance elements (2
), (1) to conduct energization and voltage measurement.
The liquid level can be monitored by switching gi (61) and (63).

Conversely, if the voltages on both sides become equal on the higher side, this indicates that liquid helium has been replenished into the container and the liquid level has risen, and both resistance elements (2) and (3) have entered the liquid. Therefore, contrary to the above, each switching device (61), (6
3) to detect the liquid level.

In this way, the number of resistive elements that continuously conduct electricity for 9 m is reduced to two that sandwich the liquid surface, and the other resistive elements are not energized, thereby preventing evaporation of liquid helium due to wasteful heat generation. Further, the load on the power supply (6o) is reduced, and a stable current with high accuracy can be obtained.

Another embodiment shown in FIG. 5 is the same as the embodiment shown in FIG. 3 except that the switching interlock device (64) of the embodiment shown in FIG. 3 is omitted.

This is because the double cutting wedge devices (61) and (63) can not necessarily be interlocked. Other functions and effects are similar to those of the embodiment shown in Figure $3.

In each of the above embodiments, the selective continuous energization of the carbon resistance elements was carried out in two (a pair) sandwiching the liquid surface, but in order to ensure the reliability of detection, three or four carbon resistance elements were , the number may be increased, or if it is predicted in advance that the liquid helium level (21) in the container will change only in the downward direction, select only the resistive element located at the top of the liquid helium below the liquid level. There is no deviation from the intent of the present invention even if the current is applied to the target and the change in the liquid level is detected by waiting for the change in voltage.Then, a carbon thin paper element is used as the resistance element. Although it has been explained above, it is of course possible to use a carbon glass resistance element, a germanium resistance element, etc. Also, the support member a1 may be rod-shaped.

〔Effect of the invention〕

As explained above, according to the present invention, current is not passed through the resistance elements that are not related to liquid level detection for the time being, so accuracy is high and unnecessary evaporation of low-temperature liquid is eliminated, making it economical. Accordingly, it is possible to provide a low-temperature liquid level detection device.

[Brief explanation of the drawing]

Fig. 1 is a schematic vertical cross-sectional view of a low temperature liquid level detection device showing parts common to the conventional method and an embodiment of the present invention, and Fig. 2 is a terminal arrangement diagram of the wiring in the conventional case of Fig. 1. , FIG. 3 is a block diagram showing the wiring system in one embodiment of the present invention shown in FIG. 1, FIG. 4 is a terminal arrangement diagram of the wiring in FIG. 3, and FIG. 5 is a wiring system in another embodiment. FIG. 1-5... Resistance element number, 1o... Resistance element 11
...Liquid helium tank 1, which is a container for storing low-temperature liquid
2... Liquid helium which is a low temperature liquid 18... Container lid 19... Support member 20... Liquid level 21... Current supply wiring 22... Voltage measurement wiring 40-59...
Terminal number 60...Power supply 61...Power switching device 6
2...Voltage measurement device 63...Measurement voltage switching device 6
4...Switching motion device agent Patent attorney Mr. Inoue Figure 1 Figure 2 Figure 3 Figure 4

Claims (3)

[Claims] (1) Arranging a plurality of resistance elements in the low-temperature liquid and above the liquid surface, passing a predetermined current through the resistance elements, and measuring the voltage of each resistance element required to flow the current,
In a low-temperature liquid level detection device that detects the liquid level based on a change in voltage, each resistance element C2 is independently provided with a current supply wiring and a voltage measurement wiring, and a terminal of each current supply wiring and voltage measurement wiring is provided. A liquid level detection device for a low-temperature liquid, characterized in that it is provided with a power supply switching device and a measurement voltage switching device for switching between a power source and an electrical measuring device, respectively. (2) The low temperature liquid level detection device according to claim 1, further comprising a switching interlock device that interlocks the power supply switching device and the measurement voltage switching device. (3) The resistive element and each wiring connected thereto are attached to two support parts in the form of a rod or a vibrator made of electrical and thermal insulators supported by a container storing a low-temperature liquid. A liquid level detection device for a low temperature liquid according to item 1 or 2.