JP3666703B2 - Liquid conductivity sensor and adapter for conductivity sensor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a conductivity measuring sensor used in an electromagnetic induction type conductivity meter for a liquid and an adapter for a conductivity measuring sensor used in this sensor.
[0002]
[Prior art]
As a conductivity meter for liquids, an electromagnetic wave that measures the conductivity of the liquid to be measured by applying an AC voltage to the excitation coil and detecting the current flowing through the current path including the liquid to be measured as a resistance by the detection coil. Inductive conductivity meters are known.
In this electromagnetic induction type conductivity meter, in order to increase the detection sensitivity in order to measure low conductivity like pure water or ultrapure water, the number of turns of the excitation coil or detection coil that increases the applied AC voltage is increased. A method such as adjusting the value can be considered.
[0003]
[Problems to be solved by the invention]
However, in the electromagnetic induction type conductivity meter, a slight change in magnetic flux due to a mechanical shock to the core and a change in permeability due to a change in ambient temperature appear as noise, which limits the detection accuracy of the conductivity.
For these reasons, it is generally difficult to increase the sensitivity of the electromagnetic induction type conductivity meter, and even if low conductivity is measured, the range of the measurement range is about 0 to 50 [μS / cm].
[0004]
On the other hand, a direct application type conductivity meter that directly applies an AC voltage between a plurality of electrodes and detects a current flowing through the liquid to be measured between the electrodes has no problem caused by a magnetic circuit such as an electromagnetic induction type. Therefore, measurement with relatively high sensitivity and low conductivity is possible.
However, this direct application type conductivity meter is not suitable for measurement of high conductivity because it is influenced by the polarization action of the test solution, unlike the electromagnetic induction type.
Therefore, when measuring a wide range of conductivity, two conductivity meters having different principles are required.
[0005]
Therefore, the present invention intends to provide an electromagnetic induction liquid conductivity measurement sensor that can be accurately measured by a single sensor even in a wide measurement range, and an adapter for the conductivity measurement sensor used in this sensor. Is.
[0006]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, the liquid conductivity measuring sensor according to claim 1 is an induced current flowing in a current path including a liquid to be measured as a resistance by an AC electric field generated by applying an AC voltage to an exciting coil. In a liquid conductivity meter that detects the conductivity of the liquid to be measured by detecting it with a detection coil,
A sensor main body having a cylindrical coil housing portion in which the excitation coil and the detection coil are coaxially incorporated;
A substantially bottomed cylindrical adapter body mounted on the sensor body and having an inner diameter larger than the outer diameter of the coil housing;
A lid plate attached together with the adapter main body so as to sandwich the coil storage portion;
With
The adapter body and the lid plate are made of a conductive material,
While forming a slit between the outer peripheral surface of the lid plate and the outer peripheral surface of the coil housing portion and the inner peripheral surface of the peripheral wall of the adapter body,
The adapter main body, the cover plate, and the liquid to be measured in the slit are present in the path of the induced current due to the AC electric field .
[0007]
The adapter for a conductivity measuring sensor according to claim 2 is attached to a sensor body having a cylindrical coil housing portion in which the excitation coil and the detection coil are coaxially incorporated, and from an outer diameter of the coil housing portion. A substantially bottomed cylindrical adapter body having a large inner diameter,
A lid plate attached together with the adapter main body so as to sandwich the coil storage portion;
With
The adapter body and the lid plate are made of a conductive material,
Forming a slit between the outer peripheral surface of the lid plate and the outer peripheral surface of the coil housing portion and the inner peripheral surface of the peripheral wall of the adapter body;
The adapter main body and the cover plate are present in the path of the induced current by the AC electric field together with the liquid to be measured in the slit .
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
First, FIG. 1 is an exploded perspective view showing an embodiment, and FIG. 2 is a longitudinal sectional view. In these drawings, reference numeral 50 denotes a sensor main body, and a cylindrical coil storage portion 52 having an exciting coil 54 and a detection coil 55 (see FIG. 2) built on the same axis, and lead lines of the coils 54 and 55 are shown. And a rod-like support portion 51 housed therein. Reference numeral 53 denotes a through hole.
[0009]
Reference numeral 10 denotes a substantially bottomed cylindrical adapter body having an inner diameter larger than the outer diameter of the coil housing portion 52, and includes a circular bottom plate 11, a peripheral wall 12, and a boss provided upright at the center of the bottom plate 11. 14. A plurality of drain holes 13 are formed in the peripheral wall 12.
[0010]
Reference numeral 30 denotes a disc-shaped cover plate having an outer diameter substantially equal to that of the coil storage portion 52, and an O-ring receiver 31 is recessed around a through hole penetrating the center. Although not shown, an O-ring receiver is similarly recessed on the inner surface of the cover plate 30 (the surface on the coil housing portion 52 side) and the inner surface of the bottom plate 11 of the adapter body 10.
Here, the adapter main body 10 and the cover plate 30 are made of a conductive material such as metal or glassy carbon.
[0011]
In order to assemble them, the O-ring 21 is disposed on the O-ring receiver of the bottom plate 11 of the adapter main body 10 and the O-ring 22 is disposed on the O-ring receiver of the cover plate 30, and the coil storage portion 52 of the sensor main body 50 is viewed from the left and right. The adapter main body 10 and the cover plate 30 are attached so as to be sandwiched, and the set screw 40 is screwed into the boss 14 of the adapter main body 10 via the O-ring 23 so as to be integrally formed as a whole.
FIG. 2 shows the overall structure of the conductivity measuring sensor assembled in this manner. The gap between the outer peripheral surface of the cover plate 30 and the outer peripheral surface of the coil storage portion 52 and the inner peripheral surface of the peripheral wall 12 of the adapter main body 10 is appropriately selected. Slits 60 having a wide interval are formed.
The drain hole 13 is for improving the flow of the liquid W to be measured that has entered the slit 60 and preventing the retention of impurities and the like.
[0012]
FIG. 3 is an enlarged view of the main part of FIG. 2, and is a diagram for explaining the operation of the slit 60. In addition, the figure has shown the state which immersed the to-be-measured liquid W in the conductivity measuring sensor of the embodiment.
[0013]
Now, when an AC voltage is applied to the exciting coil 54, the slit 30 in the path D passing through the measured liquid W in the lid plate 30, the boss 14, the bottom plate 11, the peripheral wall 12, and the slit 60 made of a conductive material. An alternating electric field appears on both sides of 60, and an alternating current flows along the path D. Here, the path D exists innumerably over the entire circumference of the excitation coil 54 and the detection coil 55, but for convenience, one path D is planarly displayed in FIG. 3.
[0014]
Since this path D is linked to the detection coil 55, a voltage proportional to the alternating current is detected from both ends of the detection coil 55. Since this voltage has a value proportional to the conductivity of the liquid W to be measured existing in the slit 60, the conductivity of the liquid W to be measured can be obtained by measuring the voltage across the detection coil 55.
[0015]
Suppose that the conductivity measuring sensor adapter comprising the adapter main body 10 (the boss 14, the bottom plate 11, the peripheral wall 12) and the cover plate 30 is not used, and only the sensor main body 50 is directly immersed in the liquid W to be measured. The path D is entirely composed of the liquid W to be measured, and the AC electric field formed by the exciting coil 54 acts on the entire length of the path D.
That is, in the embodiment shown in FIG. 3, an AC electric field generated by electromagnetic induction is applied only to the interval d of the slit 60, and when only the sensor body 50 is used without using an adapter, the same electric field is applied to the entire length of the path D. To join.
[0016]
Therefore, when the measured liquid W is the same, the AC current flowing through the measured liquid W becomes larger when the adapter is attached to the sensor body 50 as shown in FIGS. AC voltage also increases.
In other words, since the sensitivity can be increased by increasing the output voltage of the detection coil 55 for the same conductivity of the liquid W to be measured, measurement is also performed for a low conductivity that could not be measured conventionally. It becomes possible.
[0017]
Since the output voltage ratio of the detection coil 55 by attaching the adapter follows the ratio of the distance between the path D and the distance d, the shorter the distance d between the slits 60, the higher the measurement sensitivity of the conductivity and the lower the conductivity. Can be measured.
At the same time, the greater the area of the opposing surfaces on both sides of the slit 60 (the surface indicated by hatching in FIG. 3), the higher the measurement sensitivity of the conductivity, and the measurement range moves to the lower conductivity side.
[0018]
In general, in an electromagnetic induction type conductivity meter, a value proportional to the ratio (L / S) between the axial length L of the through hole 53 of the sensor body 50 and the sectional area S of the through hole 53 is defined as a cell constant. In many cases, the detection sensitivity of the sensor is represented by a constant (the smaller the cell constant, the higher the detection sensitivity).
In this embodiment, the cell constant can be obtained from the ratio between the gap d of the slit 60 described above and the area of the opposite surface to which hatching is applied. For example, the conventional conductivity measuring sensor including only the sensor main body 50 is used. In comparison, the cell constant can be reduced to about 1/100.
For this reason, according to the present embodiment example, it is possible to measure the conductivity of pure water, ultrapure water or the like having a conductivity of 1 [μS / cm] or less, which has conventionally been impossible with the electromagnetic induction method. .
[0019]
In this embodiment, the cell constant can be changed by changing the distance d between the slits 60 and the area of the facing surface.
Therefore, by changing the shape and size of the adapter body 10 and the cover plate 30 or when only the adapter body 10 is mounted without using the cover plate 30, both the cover plate 30 and the adapter body 10 are mounted. Depending on the case of mounting, the detection sensitivity can be changed by changing the cell constant stepwise.
[0020]
【The invention's effect】
As described above, if the conductivity measuring sensor according to claim 1 is used, a wide range of conductivity can be measured by the combination of the sensor main body and the adapter, and low conductivity measurement can be performed even with an electromagnetic induction type. Can do.
Further, according to the adapter for a conductivity measuring sensor according to claim 2, it is possible to improve the measurement sensitivity and change the measurement range by mounting the sensor on the sensor (sensor main body) that is already on the market.
Furthermore, since both the sensor main body and the adapter have an extremely simple structure, there is an advantage that it can be provided at a low cost.
[Brief description of the drawings]
FIG. 1 is an exploded perspective view showing an embodiment of the invention described in claims 1 and 2;
FIG. 2 is a longitudinal sectional view showing an embodiment of the invention described in claims 1 and 2;
FIG. 3 is an enlarged view of a main part of FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Adapter main body 11 Bottom plate 12 Perimeter wall 13 Drain hole 14 Boss 21,22,23 O ring 30 Cover plate 31 O ring receiver 40 Set screw 50 Sensor main body 51 Support part 52 Coil accommodating part 53 Through hole 54 Excitation coil 55 For detection Coil 60 Slit W Measured liquid D Path d Distance

Claims (2)

Liquid conductivity is measured by detecting the induced current flowing in the current path including the liquid to be measured as a resistance by the AC electric field generated by applying an AC voltage to the exciting coil and measuring the conductivity of the liquid to be measured. In the rate meter,
A sensor main body having a cylindrical coil housing portion in which the excitation coil and the detection coil are coaxially incorporated;
A substantially bottomed cylindrical adapter body mounted on the sensor body and having an inner diameter larger than the outer diameter of the coil housing;
A lid plate attached together with the adapter main body so as to sandwich the coil storage portion;
With
The adapter body and the lid plate are made of a conductive material,
While forming a slit between the outer peripheral surface of the lid plate and the outer peripheral surface of the coil housing portion and the inner peripheral surface of the peripheral wall of the adapter body,
A liquid conductivity measurement sensor , wherein the adapter main body, the cover plate, and the liquid to be measured in the slit are present in a path of an induced current due to the AC electric field . Liquid conductivity is measured by detecting the induced current flowing in the current path including the liquid to be measured as a resistance by the AC electric field generated by applying an AC voltage to the exciting coil and measuring the conductivity of the liquid to be measured. In the rate meter,
A substantially bottomed cylindrical adapter body that is mounted on a sensor body having a cylindrical coil housing portion in which the excitation coil and the detection coil are coaxially incorporated and has an inner diameter larger than the outer diameter of the coil housing portion. When,
A lid plate attached together with the adapter main body so as to sandwich the coil storage portion;
With
The adapter body and the lid plate are made of a conductive material,
Forming a slit between the outer peripheral surface of the lid plate and the outer peripheral surface of the coil housing portion and the inner peripheral surface of the peripheral wall of the adapter body;
The adapter for a liquid conductivity measurement sensor according to claim 1, wherein the adapter main body and the cover plate are present in a path of an induced current by the AC electric field together with the liquid to be measured in the slit .

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