Liquid level measuring device

Abstract

To provide a liquid level measuring device that has simple structure and can easily measure a liquid surface position of liquid.SOLUTION: A liquid level measuring device 10 for measuring a liquid surface position of liquid includes: a porous body 20 formed of a porous body containing a thermoelectric material having an absolute value of a Seebeck coefficient of 3 μV / K or higher; a lower end electrode section 11 connected to a lower end side of the porous body 20 containing a thermosetting material; and upper end electrode section 12 connected to an upper end side of the porous body 20 containing a thermosetting material. Liquid is sucked up in a lower end side dipped into liquid and a temperature difference is generated by vaporization heat when sucked liquid volatilizes in an upper end side when a liquid surface is positioned between the lower end electrode section 11 and the upper end electrode section 12 connected to the porous body 20 containing a thermosetting material, and a liquid surface position is measured by detecting an electric signal changed by an electromotive voltage generated by the temperature difference.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] This invention relates to a liquid level measuring device for measuring the liquid level position of a liquid.

Background Art

[0002] Conventionally, in order to manage the water surface position in dams, reservoirs, paddy fields, etc., and the liquid level position of liquids in various liquid storage tanks, etc., a liquid level measuring device for measuring the liquid level position of a liquid has been used. For example, Patent Document 1 proposes a float type liquid level measuring device using a float floating on the stored liquid surface. Also, Patent Document 2 proposes a pressure type liquid level measuring device that inserts a differential pressure measurement pressure sensor equipped with a diaphragm into the liquid and obtains the liquid level position using the measured liquid pressure.

[0003] Furthermore, in Patent Document 3, an electrostatic capacitance type liquid level measuring device is proposed that obtains the water surface position by measuring the moisture content of the measurement object based on the change in the dielectric constant of the measurement object. Also, in Patent Document 4, a laser type liquid level measuring device using a laser beam is proposed.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0005] Incidentally, the float-type liquid level measuring device described in Patent Document 1 and the pressure-type liquid level measuring device described in Patent Document 2 are large in size of the equipment itself, and it is necessary to secure a place for installation. In addition, in the capacitance-type liquid level measuring device described in Patent Document 3 and the laser-type liquid surface position measuring device described in Patent Document 4, there are problems such as a large number of components, a complicated equipment configuration such as circuits and instruments, and high introduction costs and operation costs.

[0006] Recently, smart agriculture that utilizes robot technology and information and communication technology (ICT) to achieve labor saving, precision, and high-quality production has been tried, and sensing technology for managing the water level of paddy fields is required. Here, since the structures of paddy fields and the like differ depending on the terrain and the like, a liquid level measuring device that can be easily installed and stably measures the liquid surface position of water (liquid) is required.

[0007] This invention has been made in view of the above-described circumstances, and an object thereof is to provide a liquid level measuring device having a simple structure and capable of easily measuring the liquid surface position of a liquid.

Means for Solving the Problems

[0008] In order to solve the above problems, the liquid level measuring device according to Embodiment 1 of the present invention is a liquid level measuring device that measures the liquid surface position of a liquid, and includes a thermoelectric material-containing porous body made of a porous body containing a thermoelectric material having an absolute value of the Seebeck coefficient of 3 μV / K or more, a lower end electrode portion connected to the lower end side of the thermoelectric material-containing porous body, and an upper end electrode portion connected to the upper end side of the thermoelectric material-containing porous body. When the liquid surface is located between the lower end electrode portion and the upper end electrode portion connected to the thermoelectric material-containing porous body, the liquid is sucked up at the lower end side immersed in the liquid, and a temperature difference is generated by the heat of vaporization when the sucked-up liquid evaporates at the upper end side. The liquid surface position is measured by detecting an electric signal that changes due to the electromotive force generated by this temperature difference.

[0009] According to the liquid level measuring device of Embodiment 1 of the present invention, a thermoelectric material-containing porous body made of a porous body containing a thermoelectric material with an absolute value of the Seebeck coefficient of 3 μV / K or more, a lower end electrode portion connected to the lower end side of the thermoelectric material-containing porous body, and an upper end electrode portion connected to the upper end side of the thermoelectric material-containing porous body are provided. Therefore, when the liquid surface is located between the lower end electrode portion and the upper end electrode portion connected to the thermoelectric material-containing porous body, an electromotive force is generated due to the temperature difference caused by the heat of vaporization when the liquid sucked up on the lower end side of the thermoelectric material-containing porous body volatilizes on the upper end side of the thermoelectric material-containing porous body. By detecting the electrical signal that changes accordingly, it becomes possible to measure the liquid surface position of the liquid. Examples of the electrical signal that can be detected include voltage, current, electrical resistance, and the like. Further, since the liquid surface position is measured by detecting the electrical signal generated between the lower end electrode portion and the upper end electrode portion connected to the thermoelectric material-containing porous body, the equipment configuration is very simple, and the introduction cost and operation cost can be kept low.

[0010] The liquid level measuring device of Embodiment 2 of the present invention is characterized in that, in the liquid level measuring device of Embodiment 1, a plurality of the thermoelectric material-containing porous bodies are arranged in the vertical direction. According to the liquid level measuring device of Embodiment 2 of the present invention, since a plurality of the thermoelectric material-containing porous bodies are arranged in the vertical direction, it becomes possible to measure the liquid surface position of the liquid in a wide range by specifying the thermoelectric material-containing porous body in which an electromotive force is generated due to the temperature difference caused by the heat of vaporization.

[0011] The liquid level measuring device of Embodiment 3 of the present invention is characterized in that, in the liquid level measuring device of Embodiment 2, the upper end electrode portion of the lower thermoelectric material-containing porous body adjacent in the vertical direction and the lower end electrode portion of the upper thermoelectric material-containing porous body are arranged to be separated from each other in the horizontal direction. According to the liquid level measuring device of Embodiment 3 of the present invention, since the upper end electrode portion of the lower thermoelectric material-containing porous body adjacent in the vertical direction and the lower end electrode portion of the upper thermoelectric material-containing porous body are arranged to be horizontally separated, it is possible to suppress interference between wirings connected to the thermoelectric material-containing porous bodies arranged in a plurality in the vertical direction, and furthermore, the structure becomes simpler, and the liquid level measuring device can be easily installed.

[0012] The liquid level measuring device of Embodiment 4 of the present invention is characterized in that, in any one of the liquid level measuring devices of Embodiments 1 to 3, one or more intermediate electrode portions are further provided between the lower end electrode portion and the upper end electrode portion connected to the thermoelectric material-containing porous body. According to the liquid level measuring device of Embodiment 4 of the present invention, since one or more intermediate electrode portions are provided between the lower end electrode portion and the upper end electrode portion connected to the thermoelectric material-containing porous body, it is possible to measure a finer liquid surface position by detecting an electrical signal between each electrode.

[0013] The liquid level measuring device of Embodiment 5 of the present invention is characterized in that, in any one of the liquid level measuring devices of Embodiments 1 to 4, the thermoelectric material is a carbon nanotube. According to the liquid level measuring device of Embodiment 5 of the present invention, since the thermoelectric material is a carbon nanotube, it is possible to form a thermoelectric material-containing porous body by making the carbon nanotube itself have a porous structure, or to form the thermoelectric material-containing porous body by containing carbon nanotubes in an insulating porous body. Also, the liquid can be surely sucked up from the lower end side of the thermoelectric material-containing porous body, and a temperature difference can be ensured between the lower end side and the upper end side of the thermoelectric material-containing porous body by the heat of vaporization of this liquid. Furthermore, after use, the thermoelectric material-containing porous body can be incinerated and discarded, and the environmental load can be reduced.

[0014] The liquid level measuring device according to aspect 6 of the present invention is the liquid level measuring device according to any one of aspects 1 to 4, characterized in that the thermoelectric material is an organic thermoelectric material. According to the liquid level measuring device of aspect 6 of the present invention, since the thermoelectric material is an organic thermoelectric material, it is possible to form a porous body containing a thermoelectric material by making the organic thermoelectric material itself have a porous structure, or by making an insulating porous body contain the organic thermoelectric material. In addition, the liquid can be reliably sucked up from the lower end side of the porous body containing the thermoelectric material, and a temperature difference can be ensured between the lower end side and the upper end side of the porous body containing the thermoelectric material by the heat of vaporization of this liquid.

[0015] The liquid level measuring device according to aspect 7 of the present invention is the liquid level measuring device according to any one of aspects 1 to 4, characterized in that the thermoelectric material is a nanotube or a nanowire made of a compound semiconductor or a silicon semiconductor. According to the liquid level measuring device of aspect 7 of the present invention, since the thermoelectric material is a nanotube or a nanowire made of a compound semiconductor or a silicon semiconductor, it is possible to form a porous body containing a thermoelectric material by making the nanotube or the nanowire itself have a porous structure, or by making an insulating porous body contain the nanotube or the nanowire. In addition, the liquid can be reliably sucked up from the lower end side of the porous body containing the thermoelectric material, and a temperature difference can be ensured between the lower end side and the upper end side of the porous body containing the thermoelectric material by the heat of vaporization of this liquid.

[0016] The liquid level measuring device according to aspect 8 of the present invention is the liquid level measuring device according to any one of aspects 1 to 7, characterized in that the porous body is any one of paper, thread, non-woven fabric, cloth, and lead stick. According to the liquid level measuring device of aspect 8 of the present invention, since the porous body is any one of paper, thread, non-woven fabric, cloth, and lead stick (wick), by incorporating a thermoelectric material into these paper, thread, non-woven fabric, cloth, and lead stick (wick), a porous body containing a thermoelectric material can be easily produced. Also, the liquid can be surely sucked up from the lower end side of the porous body containing the thermoelectric material, and a temperature difference can be ensured between the lower end side and the upper end side of the porous body containing the thermoelectric material by the heat of vaporization of this liquid.

[0017] The liquid level measuring device of aspect 9 of the present invention is characterized in that, in any one of the liquid level measuring devices of aspects 1 to 8, the liquid is a volatile liquid that can volatilize at normal temperature. According to the liquid level measuring device of aspect 9 of the present invention, since the liquid is a volatile liquid that can volatilize at normal temperature, the liquid can be vaporized at the upper end side of the porous body containing the thermoelectric material even when used at normal temperature, and an electromotive force can be surely generated by the temperature difference due to the heat of vaporization. By detecting the change in the electric signal that changes due to this electromotive force, it becomes possible to measure the liquid surface position.

Effect of the Invention

[0018] According to the present invention, it is possible to provide a liquid level measuring device with a simple structure that can easily measure the liquid surface position of a liquid.

Brief Description of the Drawings

[0019]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Mode for Carrying Out the Invention

[0020] Embodiments of the present invention will be described below with reference to the accompanying drawings. Each of the embodiments shown below is specifically described in order to better understand the gist of the invention, and does not limit the present invention unless otherwise specified. In addition, the drawings used in the following description may show, for the sake of convenience, the main parts enlarged in order to make the features of the present invention easier to understand, and the dimensional ratios of the respective components are not necessarily the same as the actual ones.

[0021] The liquid level measuring device 10 according to the present embodiment measures the liquid level position of the stored liquid in a dam, a storage pond, a paddy field, a storage tank for various liquids, etc. Here, the target liquid is preferably a volatile liquid that volatilizes at room temperature (20°C). Examples of the volatile liquid include water, various alcohols, organic solvents, volatile oils, etc. In addition, in the present embodiment, it is assumed that the water level in a paddy field or the like is measured.

[0022] As shown in FIG. 1, the liquid level measuring device 10 according to the present embodiment includes a porous body containing a thermoelectric material made of a thermoelectric material having an absolute value of the Seebeck coefficient of 3 μV / K or more, a lower end electrode portion 11 connected to the lower end side of the porous body containing the thermoelectric material 20, an upper end electrode portion 12 connected to the upper end side of the porous body containing the thermoelectric material 20, and a potentiometer 15 for measuring the potential between the lower end electrode portion 11 and the upper end electrode portion 12.

[0023] Here, in the present embodiment, as shown in FIG. 1, a plurality of porous bodies containing thermoelectric materials are arranged in the vertical direction. That is, in the present embodiment, the first thermoelectric material-containing porous body 20A (and the first lower end electrode portion 11A, the first upper end electrode portion 12A, and the first potentiometer 15A connected to the first thermoelectric material-containing porous body 20A), the second thermoelectric material-containing porous body 20B (and the second lower end electrode portion 11B, the second upper end electrode portion 12B, and the second potentiometer 15B connected to the second thermoelectric material-containing porous body 20B), and the third thermoelectric material-containing porous body 20C (and the third lower end electrode portion 11C, the third upper end electrode portion 12C, and the third potentiometer 15C) are arranged in the vertical direction. In the present embodiment, as shown in FIG. 1, a plurality of first thermoelectric material-containing porous bodies 20A (first lower end electrode portion 11A, first upper end electrode portion 12A), second thermoelectric material-containing porous bodies 20B (second lower end electrode portion 11B, second upper end electrode portion 12B), and third thermoelectric material-containing porous bodies 20C (third lower end electrode portion 11C, third upper end electrode portion 12C) arranged in the vertical direction are connected in parallel. In the present embodiment, in the thermoelectric material-containing porous bodies 20 adjacent in the vertical direction, it is preferable that the upper end electrode portion 12 of the thermoelectric material-containing porous body 20 located below and the lower end electrode portion 11 of the thermoelectric material-containing porous body 20 located above are arranged so that their positions in the vertical direction overlap.

[0024] In the present embodiment, as shown in FIG. 1, the thermoelectric material-containing porous bodies 20 are arranged obliquely with respect to the vertical direction, and in the thermoelectric material-containing porous bodies 20 adjacent in the vertical direction, the upper end electrode portion 12 of the thermoelectric material-containing porous body 20 located below and the lower end electrode portion 11 of the thermoelectric material-containing porous body 20 located above are arranged to be separated in the horizontal direction. That is, the first upper end electrode portion 12A of the first thermoelectric material-containing porous body 20A and the second lower end electrode portion 11B of the second thermoelectric material-containing porous body 20B, and the second upper end electrode portion 12B of the second thermoelectric material-containing porous body 20B and the third lower end electrode portion 11C of the third thermoelectric material-containing porous body 20C are arranged to be separated in the horizontal direction, respectively.

[0025] As described above, the porous body 20 containing a thermoelectric material is composed of a porous body containing a thermoelectric material having an absolute value of the Seebeck coefficient of 3 μV / K or more. The thermoelectric material having an absolute value of the Seebeck coefficient of 3 μV / K or more has characteristics as a semiconductor and has characteristics as a p-type semiconductor or an n-type semiconductor. In the present embodiment, the porous body 20 containing a thermoelectric material may be either a p-type semiconductor or an n-type semiconductor.

[0026] Here, examples of the thermoelectric material having an absolute value of the Seebeck coefficient of 3 μV / K or more include (a) carbon nanotubes (CNT), (b) organic thermoelectric materials, (c) nanotubes and nanowires made of compound semiconductors or silicon semiconductors, (d) noble metal compounds, (e) carbon materials, (f) metals such as Bi, Co, Fe, and Ni, and the like. Note that the thermoelectric material contained in the porous body 20 containing a thermoelectric material preferably has an absolute value of the Seebeck coefficient of 40 μV / K or more. Also, the thermoelectric materials (a) to (f) may be used in a composite form.

[0027] Here, in the case of (a) carbon nanotubes, the porous body 20 containing a thermoelectric material can be formed by making the carbon nanotubes themselves have a porous structure (paper, thread, non-woven fabric, cloth, lead stick, etc.). Also, the porous body 20 containing a thermoelectric material can be formed by containing carbon nanotubes in another porous body. Note that the Seebeck coefficient of carbon nanotubes is about 5 to 170 μV / K.

[0028] Examples of the (b) organic thermoelectric materials include PEDOT-based (PEDOT:PSS, PEDOT:Tos, etc.), π-conjugated nickel complex-based (poly(nickel-ethylenetetrathiolate)), N-DMBI-based (N,N-dimethyl-2-phenyl-2,3-dihydro-1H-benzoimidazole), and the like. Note that the Seebeck coefficient of PEDOT:PSS is about 10 to 100 μV / K. Also, the Seebeck coefficient of PEDOT:Tos is about 40 to 210 μV / K. The Seebeck coefficient of the π-conjugated nickel complex system is about -16 to -140 μV / K. In the case of organic thermoelectric materials, the porous thermoelectric material-containing body 20 can be formed by making the organic thermoelectric material itself into a porous structure (paper, thread, non-woven fabric, cloth, lead stick, etc.). Further, the porous thermoelectric material-containing body 20 can be formed by including the organic thermoelectric material in another porous body.

[0029] (c) In the case of nanotubes or nanowires made of compound semiconductors or silicon semiconductors, boron nitride nanotubes, Si nanowires, Bi 2 Te 3 The porous thermoelectric material-containing body 20 can be formed by including one or more types of nanotubes or nanowires made of compound semiconductors or silicon semiconductors, such as nanotubes or nanowires made of compound semiconductors or silicon semiconductors.

[0030] (d) Examples of noble metal compounds include copper compounds, silver compounds, gold compounds, platinum compounds, etc. Specifically, it is preferably a compound of a noble metal element (Cu, Ag, Au, Pt) and S, Se, Te. In the present application, a metal having a higher positive electrode potential compared to the standard hydrogen electrode is defined as a noble metal. In the case of noble metal compounds, the porous thermoelectric material-containing body 20 can be formed by including the noble metal compound in another porous body.

[0031] (e) Examples of carbon materials include carbon black, graphite, etc. In the case of carbon materials, the porous thermoelectric material-containing body 20 can be formed by including the carbon material in another porous body.

[0032] (f) In the case of metals such as Bi, Co, Fe, and Ni, the thermoelectric material-containing porous body 20 can be formed by incorporating metals such as Bi, Co, Fe, and Ni into other porous bodies. It is preferable to incorporate metals such as Bi, Co, Fe, and Ni into other porous bodies by means of plating.

[0033] In the present embodiment, the thermoelectric material-containing porous body 20 is a porous body impregnated with carbon nanotubes (CNT), has characteristics as a semiconductor, and has characteristics as a p-type semiconductor or an n-type semiconductor. In the present embodiment, the thermoelectric material-containing porous body 20 may be either a p-type semiconductor or an n-type semiconductor.

[0034] As the porous body, fibrous ones such as paper, thread, non-woven fabric, cloth, and lead sticks are preferable. In the present embodiment, the porous body is paper, and the thermoelectric material-containing porous body 20 is CNT-containing paper. Note that the fibers may be natural fibers or artificial fibers, and paper, thread, non-woven fabric, cloth, lead sticks, etc. combined with a plurality of fibers may also be used. Also, as the porous body, it is preferable that a structure in which capillary action occurs, and in addition to paper, thread, non-woven fabric, cloth, and lead sticks, plates, films, nets, hollow fibers, etc. can be used. Note that the porous body is preferably an insulating porous body. The porous body is preferably a hygroscopic heat-generating body, and it may have the effect of heat generation due to the hydration reaction on the material surface caused by wetting and heat generation due to the release of strain accompanying the swelling of the material.

[0035] Here, an example of the manufacturing method of the thermoelectric material-containing porous body 20 (CNT-containing paper) will be described with reference to FIG. 2.

[0036] As shown in FIG. 2(1), by putting pulp fibers into pure water and stirring sufficiently, a pulp suspension 51 in which the pulp fibers are dispersed is obtained. Further, as shown in Fig. 2(2), a carbon nanotube dispersion liquid 52 is obtained by adding single-walled carbon nanotubes to pure water and sufficiently stirring them. At this time, the single-walled carbon nanotubes are preferably in a proportion of 0.8 mass% or more and 8.0 mass% or less with respect to the weight of pulp fibers which are the paper raw material. Also, it is not necessary to add a dispersant. Further, when obtaining the carbon nanotube dispersion liquid 52, it is preferable to perform ultrasonic treatment for about 30 minutes.

[0037] Next, as shown in Fig. 2(3), a mixed liquid 53 is obtained by mixing and stirring the above-described pulp suspension 51 and carbon nanotube dispersion liquid 52. At this time, the carbon nanotubes adhere to the pulp fibers. Then, as shown in Fig. 2(4) and (5), a porous body 20 containing a thermoelectric material (CNT-containing paper) is obtained by papermaking and drying the above-described mixed liquid 53.

[0038] Next, with reference to Fig. 3, a method for measuring the liquid level position for detecting the voltage by the liquid level measuring device 10 according to the present embodiment will be described. As shown in Fig. 3(a), when the liquid level is lower than the first lower end electrode portion 11A connected to the first thermoelectric material-containing porous body 20A located at the lowermost position of the liquid level measuring device 10, the values of the first potentiometer 15A, the second potentiometer 15B, and the third potentiometer 15C do not change at all.

[0039] As shown in Fig. 3(b), when the liquid level is located between the first lower electrode portion 11A and the first upper electrode portion 12A connected to the first thermoelectric material-containing porous body 20A, the liquid is sucked up on the lower end side of the first thermoelectric material-containing porous body 20A immersed in the liquid, and the sucked-up liquid evaporates on the upper end side not immersed in the liquid. The heat of vaporization at this time causes a temperature difference between the upper end side and the lower end side of the first thermoelectric material-containing porous body 20A, and an electromotive force is generated between the first lower electrode portion 11A and the first upper electrode portion 12A due to this temperature difference. Therefore, the value of the first potentiometer 15A changes, and the values of the second potentiometer 15B and the third potentiometer 15C do not change. From this, it can be seen that the liquid level is located between the first lower electrode portion 11A and the first upper electrode portion 12A.

[0040] As shown in Fig. 3(c), when the liquid level is located between the second lower electrode portion 11B and the second upper electrode portion 12B connected to the second thermoelectric material-containing porous body 20B, the liquid sucked up on the lower end side of the second thermoelectric material-containing porous body 20B evaporates on the upper end side not immersed in the liquid, and the heat of vaporization at this time causes a temperature difference between the upper end side and the lower end side of the second thermoelectric material-containing porous body 20B, and an electromotive force is generated between the second lower electrode portion 11B and the second upper electrode portion 12B due to this temperature difference. In the first thermoelectric material-containing porous body 20A immersed in the liquid, no temperature difference occurs and no electromotive force is generated. Therefore, the value of the second potentiometer 15B changes, and the values of the first potentiometer 15A and the third potentiometer 15C do not change. From this, it can be seen that the liquid level is located between the second lower electrode portion 11B and the second upper electrode portion 12B.

[0041] As shown in Fig. 3(d), when the liquid level is located between the third lower electrode portion 11C and the third upper electrode portion 12C connected to the third thermoelectric material-containing porous body 20C, the liquid sucked up on the lower end side of the third thermoelectric material-containing porous body 20C evaporates on the upper end side not immersed in the liquid. At this time, a temperature difference is generated between the upper end side and the lower end side of the third thermoelectric material-containing porous body 20C due to the heat of vaporization, and an electromotive force is generated between the third lower electrode portion 11C and the third upper electrode portion 12C due to this temperature difference. In addition, no temperature difference occurs in the first thermoelectric material-containing porous body 20A and the first thermoelectric material-containing porous body 20A immersed in the liquid, and no electromotive force is generated. Therefore, the value of the third potentiometer 15C changes, and the values of the first potentiometer 15A and the second potentiometer 15B do not change. From this, it can be seen that the liquid level is located between the third lower electrode portion 11C and the third upper electrode portion 12C.

[0042] As described above, by measuring an electrical signal that changes due to the electromotive force between the lower electrode portion 11 (the first lower electrode portion 11A, the second lower electrode portion 11B, the third lower electrode portion 11C) and the upper electrode portion 12 (the first upper electrode portion 12A, the second upper electrode portion 12B, the third upper electrode portion 12C) connected to the thermoelectric material-containing porous body 20 (the first thermoelectric material-containing porous body 20A, the second thermoelectric material-containing porous body 20B, the third thermoelectric material-containing porous body 20C) with a potentiometer 15 (the first potentiometer 15A, the second potentiometer 15B, the third potentiometer 15C), it becomes possible to measure the liquid level position.

[0043] According to the liquid level measuring device 10 of the present embodiment configured as described above, since it includes a thermoelectric material-containing porous body 20 made of a porous body containing a thermoelectric material having an absolute value of the Seebeck coefficient of 3 μV / K or more, a lower end electrode portion 11 connected to the lower end side of the thermoelectric material-containing porous body 20, and an upper end electrode portion 12 connected to the upper end side of the thermoelectric material-containing porous body 20, when a liquid surface is positioned between the lower end electrode portion 11 and the upper end electrode portion 12, an electromotive force is generated between the lower end electrode portion 11 and the upper end electrode portion 12 due to the temperature difference caused by the heat of vaporization when the liquid sucked up on the lower end side of the thermoelectric material-containing porous body 20 volatilizes on the upper end side of the thermoelectric material-containing porous body 20. Therefore, by detecting an electrical signal that changes due to the above-described electromotive force with a potentiometer 15 connected to the lower end electrode portion 11 and the upper end electrode portion 12, it becomes possible to measure the liquid surface position of the liquid. Also, since the liquid surface position is measured by measuring the electromotive force generated between the lower end electrode portion 11 and the upper end electrode portion 12 connected to the thermoelectric material-containing porous body 20, the equipment configuration is very simple, and the introduction cost and operation cost can be kept low. Although the measurement method by detecting the voltage that changes due to the electromotive force has been described, the liquid surface position may be measured by detecting the change in current or electrical resistance.

[0044] In the liquid level measuring device 10 of the present embodiment, as shown in FIG. 1, when a plurality of thermoelectric material-containing porous bodies 20 are arranged in the vertical direction, by specifying the thermoelectric material-containing porous bodies 20 (the first thermoelectric material-containing porous body 20A, the second thermoelectric material-containing porous body 20B, the third thermoelectric material-containing porous body 20C) in which an electromotive force is generated due to the temperature difference caused by the heat of vaporization, it becomes possible to measure the liquid surface position of the liquid in a wide range.

[0045] In the liquid level measuring device 10 according to the present embodiment, as shown in FIG. 1, the thermoelectric material-containing porous body 20 is arranged obliquely with respect to the vertical direction. In the thermoelectric material-containing porous bodies 20 adjacent in the vertical direction, when the upper end electrode portion 12 of the thermoelectric material-containing porous body 20 located below and the lower end electrode portion 11 of the thermoelectric material-containing porous body 20 located above are arranged horizontally apart from each other, it is possible to suppress interference between the wirings connected to the lower end electrode portions 11 and the upper end electrode portions 12 of the plurality of thermoelectric material-containing porous bodies 20 arranged in the vertical direction, and the equipment can be configured more easily.

[0046] In the liquid level measuring device 10 according to the present embodiment, when the thermoelectric material constituting the thermoelectric material-containing porous body 20 is a carbon nanotube, the liquid can be surely sucked up from the lower end side of the thermoelectric material-containing porous body 20, and a temperature difference can be ensured between the lower end side and the upper end side of the thermoelectric material-containing porous body 20 by the heat of vaporization of this liquid. Furthermore, after use, the thermoelectric material-containing porous body 20 can be incinerated and discarded, and the environmental load can be reduced. Also, it is possible to configure the thermoelectric material-containing porous body 20 by making the carbon nanotube itself have a porous structure, or it is also possible to configure the thermoelectric material-containing porous body 20 by containing carbon nanotubes in an insulating porous body.

[0047] In the liquid level measuring device 10 according to the present embodiment, when the thermoelectric material constituting the thermoelectric material-containing porous body 20 is an organic thermoelectric material, the liquid can be surely sucked up from the lower end side of the thermoelectric material-containing porous body 20, and a temperature difference can be ensured between the lower end side and the upper end side of the thermoelectric material-containing porous body 20 by the heat of vaporization of this liquid. Also, it is possible to configure the thermoelectric material-containing porous body 20 by making the organic thermoelectric material itself have a porous structure, or it is also possible to configure the thermoelectric material-containing porous body 20 by containing an organic thermoelectric material in an insulating porous body.

[0048] In the liquid level measuring device 10 according to the present embodiment, when the thermoelectric material constituting the porous body 20 containing the thermoelectric material is a nanotube or a nanowire made of a compound semiconductor or a silicon semiconductor, the liquid can be surely sucked up from the lower end side of the porous body 20 containing the thermoelectric material, and a temperature difference can be ensured between the lower end side and the upper end side of the porous body 20 containing the thermoelectric material by the heat of vaporization of this liquid. Also, it is possible to form the porous body 20 containing the thermoelectric material by making the nanotube or the nanowire itself have a porous structure, or to form the porous body 20 containing the thermoelectric material by making the insulating porous body contain the nanotube or the nanowire.

[0049] In the liquid level measuring device 10 according to the present embodiment, when the porous body is any one of paper, thread, non-woven fabric, cloth, and lead stick, the porous body 20 containing the thermoelectric material can be easily produced by making these paper, thread, non-woven fabric, cloth, and lead stick (wick) contain the thermoelectric material. Also, the liquid can be surely sucked up from the lower end side of the porous body 20 containing the thermoelectric material, and a temperature difference can be ensured between the lower end side and the upper end side of the porous body 20 containing the thermoelectric material by the heat of vaporization of this liquid.

[0050] In the liquid level measuring device 10 according to the present embodiment, when the liquid is a volatile liquid that can be volatilized at normal temperature, the liquid can be vaporized at the upper end side of the porous body 20 containing the thermoelectric material even when used at normal temperature, and an electromotive force can be surely generated by the temperature difference due to the heat of vaporization. By detecting an electric signal that changes due to this electromotive force, it becomes possible to measure the liquid level position.

[0051] As described above, one embodiment of the present invention has been described, but the present invention is not limited thereto, and can be appropriately changed without departing from the technical idea of the invention. For example, in this embodiment, although it has been described as arranging a plurality (three) of the porous bodies containing the thermoelectric material in the vertical direction, it is not limited thereto. As shown in FIG. 4, it may be constituted by only one porous body containing the thermoelectric material. Also, two may be used, or four or more may be used.

[0052] Further, in this embodiment, as shown in FIG. 1, although it has been described as providing the lower end electrode portion 11 and the upper end electrode portion 12 to the porous body 20 containing the thermoelectric material, it is not limited thereto. As shown in FIG. 5, an intermediate electrode portion 13 may be formed between the lower end electrode portion 11 and the upper end electrode portion 12. In this case, by the potentiometer 151 disposed between the lower end electrode portion 11 and the intermediate electrode portion 13 and the potentiometer 152 disposed between the intermediate electrode portion 13 and the upper end electrode portion 12, it becomes possible to measure a finer liquid level position by detecting the electrical signal between each electrode.

[0053] Also, in this embodiment, as shown in FIG. 1, the first porous body 20A containing the thermoelectric material (the first lower end electrode portion 11A, the first upper end electrode portion 12A), the second porous body 20B containing the thermoelectric material (the second lower end electrode portion 11B, the second upper end electrode portion 12B), and the third porous body 20C containing the thermoelectric material (the third lower end electrode portion 11C, the third upper end electrode portion 12C) arranged in a plurality in the vertical direction have been described as being connected in parallel. However, as shown in FIG. 6, they may be connected in series.

[0054] Furthermore, in this embodiment, although it has been described as using a porous body made of paper as the porous body containing the thermoelectric material (thermoelectric material-containing paper), it is not limited thereto. It may be a porous body containing the thermoelectric material (thermoelectric material-containing thread) with the porous body being a thread, or a porous body containing the thermoelectric material (thermoelectric material-containing cloth) with the porous body being a cloth, or a porous body containing the thermoelectric material (thermoelectric material-containing lead stick) with the porous body being a lead stick. Note that a thermoelectric material-containing thread (CNT-containing thread) impregnated with carbon nanotubes as the thermoelectric material can be manufactured by the method shown below.

[0055] The method of incorporating carbon nanotubes into a thread is basically the same as techniques such as hand-dyeing. The base thread is immersed in a carbon nanotube dispersion, and in this state, the dispersion is heated to a temperature just below boiling (around 60 °C) to evaporate the moisture, so that the concentrated carbon nanotubes coat the thread. Such an impregnation method can be employed, by which more carbon nanotubes can be impregnated into the thread.

[0056] Note that as the base thread (substrate) required for producing the CNT-containing thread, natural-origin threads such as commonly used cotton threads, hemp threads, wool, silk, etc. or synthetic fiber threads such as polyester and nylon derived from chemical synthesis can be used, and a mixed thread of these may also be used. Here, for a thread of a type where dyes do not penetrate, such as a synthetic fiber, a CNT-containing thread may be produced by applying a carbon nanotube dispersion to its surface and drying it.

Explanation of Reference Signs

[0057] 10 Liquid level measuring device 11 Lower electrode part 12 Upper electrode part 13 Intermediate electrode part 20 Thermoelectric material-containing porous body

Claims

1. A liquid level measuring device for measuring the liquid level position of a liquid, comprising: a porous body containing a thermoelectric material made of a thermoelectric material having an absolute value of the Seebeck coefficient of 3 μV / K or more; a lower end electrode portion connected to the lower end side of the porous body containing the thermoelectric material; and an upper end electrode portion connected to the upper end side of the porous body containing the thermoelectric material. When the liquid surface is positioned between the lower end electrode portion and the upper end electrode portion connected to the porous body containing the thermoelectric material, the liquid is sucked up at the lower end side immersed in the liquid, and a temperature difference is generated by the heat of vaporization when the sucked-up liquid evaporates at the upper end side. The liquid level position is measured by detecting an electric signal that changes due to the electromotive force generated by this temperature difference. A liquid level measuring device characterized by this.

2. The liquid level measuring device according to claim 1, wherein a plurality of the porous bodies containing the thermoelectric material are arranged in the vertical direction.

3. The liquid level measuring device according to claim 2, wherein in the porous bodies containing the thermoelectric material adjacent to each other in the vertical direction, the upper end electrode portion of the lower porous body containing the thermoelectric material and the lower end electrode portion of the upper porous body containing the thermoelectric material are arranged to be separated from each other in the horizontal direction.

4. The liquid level measuring device according to claim 1 or claim 2, further comprising one or more intermediate electrode portions between the lower end electrode portion and the upper end electrode portion connected to the porous body containing the thermoelectric material.

5. The liquid level measuring device according to claim 1 or claim 2, wherein the thermoelectric material is a carbon nanotube.

6. The liquid level measuring device according to claim 1 or claim 2, wherein the thermoelectric material is an organic thermoelectric material.

7. The liquid level measuring device according to claim 1 or claim 2, wherein the thermoelectric material is a nanotube or a nanowire made of a compound semiconductor or a silicon semiconductor.

8. The liquid level measuring device according to claim 1 or claim 2, wherein the porous body is any one of paper, thread, non-woven fabric, and cloth.

9. The liquid level measuring device according to claim 1 or claim 2, wherein the liquid is a volatile liquid that can evaporate at room temperature.

Images