JPS63169545A - Terminal for measuring electrical conductivity - Google Patents

Abstract

PURPOSE:To exactly measure the electrical conductivity of an aq. soln. by disposing electrodes to a porous ceramic body having specific pore sizes and porosity and coating the surface thereof with a nonconductive coating layer. CONSTITUTION:A pair of the electrodes 2, 2 are disposed to a soln. absorptive body 1 consisting of the porous ceramic body of alumina, zirconia, etc. The pores size of the body 1 is specified to 0.1-1.0mu and the porosity to 35-55%. Conductive paste of platinum, etc., is baked onto the electrodes 2, 2 and an epoxy resin 4 which is a nonconductive material is coated thereon to constitute a terminal A for measuring electrical conductivity. The terminal A for measurement is then inserted into a medium for hydroponic culture so that the aq. soln. of the medium is penetrated into the soln. absorptive body 1, thereby measuring the electrical conductivity. Since the soln. absorptive body is provided, the infiltration of a woolly packing material such as rock wool into the absorptive body is prevented even if such material exists. The exact measurement of the electrical conductivity is thus permitted.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an electrical conductivity measuring terminal suitable for accurately measuring the electrical conductivity of a culture solution in a hydroponic culture medium.

(Prior art) In order to measure the electrical conductivity of an aqueous solution, it is necessary to
As shown in Japanese Patent No. 85073, a method in which a pair of electrodes is immersed in an aqueous solution and the electrical resistance between the electrodes is measured is widely used.

However, when a cotton-like packing material such as rock wool is impregnated with the culture solution, as in the case of a solid medium, these fixed inclusions get in the way, making it difficult to accurately measure the electrical resistance between the electrodes. However, there was a drawback that composition control was likely to become unstable.

(Problems to be Solved by the Invention) The present invention solves the above-mentioned conventional problems and accurately measures the electrical conductivity of an aqueous solution such as a culture solution even when a cotton-like filling is present. It was completed with the purpose of being a terminal for measuring electrical conductivity.

(Means for solving the problems) The present invention has a pore size of 0.1 to 1. O, #, Qi TL treasure 35~5
On the surface of a solution absorber made of 5% ceramic porous material,
It is characterized in that electrodes are formed at required intervals and a non-conductive coating layer is formed on the surface of the electrodes.

(Example) Next, the present invention will be explained in detail with reference to the illustrated example.
In the first embodiment shown in FIG. 1, (1) is a flat solution absorber made of porous ceramic material such as alumina or zirconia and has a thickness of about 0.5 to 1.0 fl; (2)
are a pair of electrodes formed at a required interval on one surface of the electrode. The ceramic porous body constituting the solution absorber (11) is selected to have a pore diameter of 0.1 to 1.0 μm and a porosity of 35 to 55%. If the pore diameter is less than 0.1 μm, the aqueous solution inside It becomes difficult to impregnate the aqueous solution, making it difficult to perform measurements quickly, and it takes time to replace the aqueous solution, which worsens the responsiveness to changes in electrical conductivity in the aqueous solution.On the other hand, if the pore size exceeds 1.0 μ, the aqueous solution The suspended solids inside the tube become clogged, making the measurement unstable.For this reason, the most preferable pore diameter is in the range of 0.2 to 0.8μ.The porosity is 35%.
If it is less than 55%, impregnation with the aqueous solution will be insufficient, so a larger one is preferable, but if it exceeds 55%, the strength of the ceramic porous body will be weakened. Therefore, the most preferable porosity range is 40 to 50%.

The electrodes (2), (2) are constructed by baking an electrically conductive paste containing platinum or the like as a main component onto the surface of the ceramic solution absorber (1) as described above.
In the illustrated embodiment, the mutual spacing is approximately 1 fi. Platinum-shaped lead wires (3), (3) are brazed to the surfaces of these electrodes (2), (2), and
), (2) A coating layer (4) made of a non-conductive substance such as epoxy resin is formed on the surface of the solution absorber (1), but the material of the electrode, lead wire, non-conductive substance, etc. is not limited to this example.

When the electrical conductivity measuring terminal of the first embodiment configured as described above is inserted into a hydroponic cultivation medium, only the aqueous solution in the medium permeates into the interior of the solution absorber 11) made of a porous ceramic body. and electrodes (
2), electrical conductivity is measured by (2). At this time, the cotton-like filling such as rock wool is used as a solution absorber (1
8i (21,
(2) Only the aqueous solution and the ceramic porous body exist in between, so if Cali-Pray silane is applied to each terminal, the influence of the ceramic porous body can be removed, and the electrical conductivity can be determined with extremely high precision. Measurement becomes possible.

In addition, the surfaces of the electrodes (2), (2) are covered with a non-conductive coating N (4
), so the side that is not in contact with the solution absorber (1) will not be affected by the aqueous solution. Note that in Figure 1, the electrodes (2) and (2) are long and flat plates. It is also possible to increase the effective area and improve the measurement accuracy by making the electrodes (2), (2) have a comb-like shape that is intertwined with each other.

Next, in the second embodiment shown in FIG. 2, the solution absorber (1)
A compensation electrode (5) is formed on the back side of the substrate, that is, the opposite side to that on which the electrode (2) is formed. The compensation electrode (5) is also formed by baking a conductive paste and its surface is covered with a non-conductive coating layer (4).
3) is not connected.By providing this compensation electrode (5), a conductive path is provided in the thickness direction of the solution absorber (1), and the potential distribution is relaxed, which improves measurement accuracy. It is possible to improve it further. In addition to the concentric rectangular shape shown in the figure, the shape of the compensation electrode (5) can be various variations such as a cross-shaped shape, a comb-like shape, a dot shape, a striped shape, and the like.

Furthermore, in the third embodiment shown in FIG.
, (2) are formed on both the front and back surfaces of the solution absorber (1), and in this case as well, the electrical conductivity of the aqueous solution that has penetrated into the inside of the porous solution absorber (11) is measured in the thickness direction. Ru.

In addition, in the first to third embodiments described above, a flat solution absorber (1) was used, but its shape is not necessarily limited to a flat plate, and its surface may be shaped like a rod, cylinder, etc. An electrode may also be formed.

The thickness of the solution absorber (1) is 0.5 fl, 1 fl, 2 fl, and 3
When the electrical conductivity of the culture solution in an actual hydroponic culture medium was measured using the terminal of the type according to the first embodiment of the present invention, the results showed that only the water content was taken out from the culture medium into a separate container. In addition to obtaining values equivalent to the measured values over a wide range of measurement boxes and enclosures, they also responded well to changes over time. The terminals showed excellent response. In this way, the terminal of the present invention corresponds well to the value that is considered to be the correct value measured by extracting only the water content from the solid medium, and it is possible to obtain accurate electricity even in the presence of cotton-like fillings such as rock wool. It turned out that conductivity can be measured.

(Effects of the Invention) As is clear from the above description, the present invention can accurately measure the electrical conductivity of an aqueous solution without being affected by cotton-like fillers, etc. It will greatly contribute to the industry as a suitable device for measuring the electrical conductivity of culture fluids.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway perspective view showing a first embodiment of the present invention;
FIG. 2 is a partially cutaway perspective view showing the second embodiment, and FIG. 3 is a partially cutaway perspective view showing the third embodiment. (1): solution absorber, (2): electrode, (4) = coating layer,
(5); Compensation electrode. Patent applicant: Nippon Insulator Co., Ltd. Representative name: Akira Shima Buma
Watanuki Tatsu separation
Written by Yamamoto, Figure 1 (: Figure 2)

Claims (1)

[Claims] 1. Electrodes (2), ( 2) and a non-conductive coating layer (4) formed on the surface thereof. 2. The terminal for measuring electrical conductivity according to claim 1, wherein the electrodes (2), (2) are formed on the same surface of the solution absorber (1). 3. A terminal for measuring electrical conductivity according to claim 2, wherein a compensating electrode (5) is formed on the opposite surface of the solution absorber (1) to the surface on which the electrodes (2), (2) are formed. . 4. The terminal for measuring electrical conductivity according to claim 1, wherein the electrodes (2), (2) are formed on both the front and back surfaces of the solution absorber (1).