JPH08166367A - Concentration sensor - Google Patents

Abstract

PURPOSE: To obtain a concentration sensor which can achieve high accuracy without being influenced by a setting direction. CONSTITUTION: The concentration sensor is provided with an insulating cylindrical container 1 where a fluid to be measured by the sensor is supplied, and a plurality of electrodes 2a-4b arranged symmetrically to upper and lower faces and right and left faces including an axis of the container 1 and parallel to the axis. Pairs of electrodes are connected in series while the electrodes symmetric to the upper and lower faces of the container are paired. Accordingly, the static capacity to be measured can be formed by the series connection.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a concentration sensor applied to slurry concentration measurement in high-density heat transport devices and the like.

[0002]

2. Description of the Related Art Conventionally, capacitive concentration sensors have been manufactured, for example, measurement optics (III) (Ki Tomizawa, Morikita Shuppan).
Pp. 164, 1972) and is also marketed by Yamamoto Electric Instruments Co., Ltd.

FIG. 5 shows a sectional structure of the capacitance type concentration sensor. The concentration sensor 19 has a tubular shape and is connected by the flanges 18a and 18b at both ends. And it is used as a part of the pipe through which the fluid to be measured flows. An axial electrode 15 is arranged on the central axis of the tube, and the inner surface of the tube is covered with another cylindrical electrode 1
6 is set.

Then, a fluid is flown into the cylindrical electrode 16 to measure the capacitance between the electrodes 15 and 16. Since the composite permittivity of the substance forming the fluid has a one-to-one relationship with the measured capacity, if the permittivity of the substance forming the fluid is clear, the concentration of this substance can be obtained.

[0005]

In the above-mentioned conventional apparatus, there is a problem that the nonuniform concentration distribution of the fluid passing through the sensor causes a measurement error. Therefore, in a fluid composed of two or more kinds of substances having a large difference in specific gravity, the constituent substances are separated in the flow, and as shown in the use example of FIG.
When used for vertical flow, it has less effect, but for horizontal flow, it is unevenly distributed in the gravity direction,
There was an error.

An object of the present invention is to eliminate the above problems.

[0007]

The present invention employs the following means to solve the above-mentioned problems.

That is, a cylindrical measuring container made of an insulating material, through which a fluid to be measured by a concentration sensor is passed, and a plurality of symmetrically arranged upper and lower surfaces and a left and right surface including the axis of the measuring container and parallel to the axis. Of the above electrodes, and each pair is connected in series with the upper and lower surfaces of the plurality of electrodes as a pair of symmetrical electrodes.

[0009]

In the above invention, the measuring container has a cross section of, for example, a rectangular shape, and one side is parallel to the left and right surfaces. Further, it is assumed that the fluid to be measured is a mixture of dielectric constants A and B and flows as a layer of an interface parallel to the left and right surfaces. Assuming that each electrode has the same area S, the measured capacitance is determined by the following action. That is, since the interface is an equipotential surface, the electric field distribution does not change even if the virtual electrode is inserted here. Therefore, it may be considered that the pair of electrodes are connected in series with each other with the virtual electrode interposed therebetween. That is, the measured capacitance is formed by further connecting these in series.

On the other hand, let us consider a case where the interface is not parallel to the left and right surfaces but is flowing with a slight inclination. At this time, if the mixing ratio is the same as above, the position of the line of intersection between the interface and the upper and lower surfaces is the same as above. In addition, since the interface can be approximated by an equipotential surface within each pair of electrodes, it can be considered that the interfaces are connected in series with the virtual electrode sandwiched therebetween as described above. Further, the capacitance to be measured is, as described above, those connected in series.

Next, from a different point of view, consider a pair of left and right electrodes that are symmetrical with respect to the upper and lower surfaces. Considering a plane parallel to the upper and lower planes passing through the intersection line, this plane can also be approximated by an equipotential surface, so that it can be regarded as being connected in series with a virtual and an electrode. Therefore, even if the virtual electrode and the virtual electrode are exchanged on the left and right, only the connection order is changed and the measured capacitance does not change. That is, the exchange of the left and right is the same as in the case of the flow at the interface passing through the intersection line and parallel to the upper and lower surfaces, as in the above case.

With the above operation, fluids having different dielectric constants form an interface and flow, and even if the interface is parallel to the upper and lower surfaces or inclined, the same mixture ratio is obtained. The capacitance of is measured. Therefore, even if the axis is arranged in the left-right direction and the axis is slightly inclined, the concentration can be accurately measured. That is, accurate measurement can be performed without being significantly affected by the installation direction.

[0013]

【Example】

(1) A first embodiment of the invention will be described with reference to FIGS.

In FIG. 1, rectangular electrodes 2a, 2b, 3a, 3 parallel to the axis a are formed on the upper and lower outer surfaces of a measuring container 1 made of an insulator (eg, PVC, glass, etc.) having a rectangular cross section.
b, 4a, 4b are arranged. These are symmetrical with respect to the upper and lower surfaces H-H 'and the left and right surfaces V-V' including the axis a. The electrodes 2a, 2b and 3a, 3 symmetrical with respect to the upper and lower surfaces H-H '
Each pair is connected in series with b and 4a, 4b as a pair. In the figure, 5a and 5b are lead wires, and 6a and 6b are terminals.

In the above, the fluid to be measured is caused to flow in the axial direction, and the capacitance is measured between the terminals 6a and 6b. At this time, the concentration distribution of the fluid flowing in the measurement container 1 becomes non-uniform, and for example, as shown in FIG.
Suppose that Then, assuming that the dielectric constant of the upper fluid 9 is ε _A and the dielectric constant of the lower fluid 10 is ε _B , the measured capacitance C _S is given by the equation (1).

[0016]

[Equation 1]

However, d: distance between a pair of electrodes αd: thickness of ε _A (distance to intersection of vv ′ and h−h ′) (1-α) d: thickness of ε _B S : Area of each electrode Next, the fluids 9 and 10 have the same mixing ratio (concentration) as described above, and as shown in FIG.
Consider the case where it is inclined with respect to H '. In this case, each electrode pair (2a, 2b and 3a, 3b and 4a, 4b)
Inside, the interface can be approximated to be parallel to the left and right surfaces as shown in the figure.

Therefore, the measured capacitance C _S ′ is given by the equations (1) to (5).

[0019]

[Equation 2]

[0020] However, C _2ab: electrode pair 2a, 2b of the capacitance C _3ab: electrode pair 3a, 3b of the electrostatic capacitance C _4ab: electrode pair 4a, the electrostatic capacitance of 4b thus C _S '= C _S, and the The same result is obtained when the concentration is the same.

For reference, in the case of the conventional device, that is, in the case of parallel connection (see FIG. 4), the formula (6) is obtained, which is different from the form of the formula (1). Therefore, a mistake occurs.

[0022] In the _{C P = C 2ab + C 3ab} + C 4ab ............ (6) above, the axis a is disposed on the left and right, precisely concentration be slightly inclined about axis a can be measured.

(2) A second embodiment of the present invention will be described with reference to FIG.

Almost the same as the above, but the electrodes 2a, 2b, 3a, 3b, 4a, 4b are formed on the upper and lower surfaces of the inner surface of the measuring container 1.
Is placed and the front surface is covered with the insulating layers 20a and 20b. Since the thickness of the insulating layers 20a and 20b can be made thinner than the thickness of the measurement container 1, this influence is reduced and the measurement accuracy is improved.

In the above (1) and (2), the number of electrode pairs is three, but the number of electrodes may be increased, and two kinds of fluids to be measured were considered. To work.

[0026]

According to the present invention as described above,
It is possible to perform highly reliable measurement with little error regardless of the installation direction.

[Brief description of drawings]

FIG. 1 is a configuration perspective view of a first embodiment of the present invention.

FIG. 2 is an explanatory view of the operation of the same embodiment.

FIG. 3 is an explanatory view of the operation of the embodiment.

FIG. 4 is an explanatory view of the operation of the embodiment.

FIG. 5 is a configuration perspective view of a second embodiment of the present invention.

FIG. 6 is a configuration cross-sectional view of a conventional example.

FIG. 7 is an operation explanatory view of the conventional example.

[Explanation of reference numerals] 1 measuring vessels 2a, 2b, 3a, 3b, 4a, 4b electrodes 5a, 5b lead wires 6a, 6b terminals

Claims (1)

[Claims] 1. A cylindrical measuring container made of an insulating material, through which a fluid to be measured passes, and a plurality of electrodes arranged symmetrically on the upper and lower surfaces and the left and right surfaces including the axis of the measuring container and parallel to the axis. A concentration sensor comprising: a pair of symmetrical electrodes on the upper and lower surfaces of the plurality of electrodes, each pair being connected in series.