JP2001099780A - Device for measuring solution concentration using optical fiber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a device for measuring the solution concentration using an optical fiber capable of monitoring the concentration of a solution continuously in time with a simple structure. SOLUTION: This device for measuring solution concentration comprises an optical fiber 3 with a part of a clad part removed in a longitudinal direction, an LED light source 1 for entering a light signal to the optical fiber 3, a photodiode 2 for receiving the light signal emitted from the optical fiber 3, a container 5 for housing a clad eliminated part of the optical fiber 3 and a solution of which the concentration is measured. A core part of the optical fiber 3 is formed of thermosetting resin, and the clad part is formed of synthesized resin tube. The optical fiber is formed by forming the clad part of a synthesized resin, injecting precursor of the core part, and after a certain period of time, heating and hardening.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for measuring the concentration of a solution using an optical fiber.

[0002]

2. Description of the Related Art Conventionally, as a method for measuring the concentration of a solution, an aqueous solution in which a solvent is dissolved is taken in another container, and the pH (pH), conductivity, refractive index, specific gravity, light transmittance, It has been performed by measuring physical properties such as electric conductivity. The concentration was calculated from the change in the physical property value.

[0003]

The conventional method for measuring the concentration of a solution has the following problems.

When the concentration of a solution is continuously monitored over time, the measurement line must be provided in a separate system, which makes the whole solution concentration measuring apparatus complicated and impractical. That is, there is a problem that there is substantially no means for measuring the concentration of the solution continuously over time.

Accordingly, an object of the present invention is to solve the above-mentioned disadvantages of the prior art and to provide an apparatus for measuring the concentration of a solution using an optical fiber capable of monitoring the concentration of the solution continuously with a simple structure. Is to do.

[0006]

According to the present invention, there is provided an optical fiber having a clad portion partially removed in a longitudinal direction, a light source for inputting an optical signal to the optical fiber, and a light source. A light receiving device for receiving the optical signal emitted from the fiber, a water tank containing a solution for measuring the concentration and the cladding removal portion of the optical fiber, the core of the optical fiber is a thermosetting resin. In addition, it is assumed that the clad portion is a synthetic resin tube, and the precursor of the core portion is injected after forming the synthetic resin tube of the clad portion, and then obtained by heating and curing.

[0007] The light source may be an LED (light emitting diode).

[0008] The light receiver may be a photodiode.

[0009] The solution may be an aqueous solution in which a detergent for washing clothes is dissolved.

[0010] The water tank may be attached to a washing machine for washing clothes.

[0011]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a perspective view showing one embodiment of a solution concentration measuring apparatus using an optical fiber according to the present invention. 1 is an LED light source, 2 is a photodiode, 3 is an optical fiber,
Reference numeral 4 denotes a clad removing portion, and reference numeral 5 denotes a water tank. The apparatus for measuring the concentration of a solution using an optical fiber includes an LED light source 1, a photodiode 2, an optical fiber 3, and a water tank 5. The optical fiber 3 has a clad removal portion 4 in which a clad portion at a central portion in a longitudinal direction is removed. And
The optical fiber 3 is connected to the LED light source 1 and the photodiode 2, and the light output is constantly monitored. In the water tank 5, the solution whose concentration is to be measured is configured to completely cover the clad removing section 4.

FIG. 2 is an explanatory view of the principle of the solution concentration measuring apparatus using the optical fiber of FIG. 1, and is basically equivalent to the solution concentration measuring apparatus using the optical fiber of FIG. 6
Denotes a light source, 7 denotes a light receiver, 8 denotes an optical fiber, and 9 denotes a water tank. The optical fiber 8 is connected to the light source 6 and the light receiver 7, and the optical output is constantly monitored. FIG. 3 is a perspective view of the optical fiber 8 of FIG. 10 is a core part, 11 is a clad part,
Reference numeral 12 denotes a clad removing portion. This optical fiber 8 is shown in FIG.
Is exactly the same as the optical fiber 3 of FIG.

The optical fiber 8 (3 in FIG. 1) is
And the clad portion 11, the core portion 10 is a thermosetting resin, and the clad portion 11 is a synthetic resin tube.
In the method for manufacturing the optical fiber 8, after forming the synthetic resin tube of the clad portion 11, a precursor of a thermosetting resin, which is a material of the core portion 10, is injected and heated. By doing so, the core portion 10 is cured and polymerized, and the optical fiber 8 is completed.

The optical fiber 8 has a clad removing portion 12 at a central portion in the longitudinal direction.
2 is a part for measuring the concentration of the solution. By manufacturing the optical fiber 8 by the method described above, it is possible to easily peel off the clad portion 11 mechanically without using a solvent or the like. Also, the core part 1
Since 0 is a thermosetting resin, it has durability against surfactants such as detergents and chemicals.

Actually, an acrylic resin is used as a material of the core portion 10 and a tetrafluoroethylene / hexafluoroethylene copolymer is used as a material of the clad portion 11. When a tube of the clad portion 11 is formed, acrylic monomer is injected and heated.・ It has hardened. The diameter of the core 10 of the optical fiber 8 thus manufactured is 1.5 mm,
Has a diameter of 2.2 mm and an overall length of 2 m. The clad removing portion 12 is formed by setting the central portion of the optical fiber 8 to 35 cm.
The clad portion 11 was peeled off with a knife.

The principle of measuring the concentration of a solution is described in Jpn.
The method described in J. of Appl. Phys. Vol. 37 pp. L85-L87 (1998) is used. That is, while the optical signal propagates while being totally reflected at the boundary between the core portion 10 and the clad portion 11, the solute molecules adhere to the core surface in the clad removing portion 12, and as a result, the transmission characteristics of the optical signal change and the optical signal is transmitted. The amount changes. Therefore, by calibrating the light output and the concentration of the solute molecules in advance, the concentration of the solute molecules can be quickly known when the light output is monitored.

The light source 6 preferably has a simple structure, and an LED (light emitting diode) or an LD (laser diode) is suitable. Although an LED is desirable in terms of cost, an LD is desirable in terms of light output. In any case, it can be selected according to the type of the solution to be measured and the place to which the present concentration measuring device is applied. In the example shown in FIG. 1, a red LED of 660 nm was used.

The light receiver 7 may be any light receiver that can receive the optical output of the optical signal emitted from the light source 6 and propagated through the optical fiber 8. A photodiode is desirable in terms of cost and simplicity.

FIG. 4 is a graph showing the relationship between the concentration and the light output by the solution concentration measuring device using the optical fiber of FIG. The horizontal axis is the concentration of the solution (wt%), and the vertical axis is the light output (%). The light output when the concentration is 0 wt% is used as a reference. The solution used herein was Kao Corporation's laundry detergent, Attack (trade name). Along with the detergent concentration,
The light output greatly changed, and by monitoring the light output using this figure, the concentration of the detergent could be quickly known.

FIG. 5 is a perspective view when the apparatus for measuring the concentration of a solution using the optical fiber of FIG. 1 is installed in a washing machine. 1
Reference numeral 3 denotes a washing machine, 14 denotes a water tub of the washing machine, 15 denotes a rotating tub of the washing machine, 16 denotes an apparatus for measuring the concentration of a solution using an optical fiber, 1
7 is a water supply hose and 18 is a drain hose. The water supplied from the water supply hose 17 and the detergent supplied to the washing machine 13 are mixed, and an aqueous solution having an appropriate concentration fills the water tub 14 of the washing machine. A solution concentration measuring device 16 using an optical fiber is provided so as to be completely immersed in the aqueous solution. That is, the water tank of the solution concentration measuring device 16 using an optical fiber is attached to the water tank 14 of the washing machine. By installing the solution concentration measuring device 16 using an optical fiber in the washing machine 13 in this manner, it is possible to appropriately control the amount of detergent used.

In this embodiment, the measurement of the concentration of the detergent, which is a surfactant, as a solution has been described, but other solvents and solutes can be applied. In this case, attention must be paid to deterioration such as crazing and cracking of the optical fiber due to the solvent or solute.

[0023]

According to the apparatus for measuring the concentration of a solution using an optical fiber according to the present invention, it is possible to monitor the concentration of the solution continuously with a simple structure. Because of the simple structure, the cost of the entire apparatus can be reduced.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an embodiment of a solution concentration measuring device using an optical fiber according to the present invention.

FIG. 2 is a diagram illustrating the principle of a device for measuring the concentration of a solution using the optical fiber of FIG. 1;

FIG. 3 is a perspective view of the optical fiber of FIG. 2;

FIG. 4 is a graph showing a relationship between a concentration and a light output by a concentration measuring device for a solution using the optical fiber of FIG. 1;

FIG. 5 is a perspective view when the apparatus for measuring the concentration of a solution using the optical fiber of FIG. 1 is installed in a washing machine.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 LED light source 2 Photodiode 3 Optical fiber 4 Cladding removal part 5 Water tank 6 Light source 7 Receiver 8 Optical fiber 9 Water tank 10 Core part 11 Cladding part 12 Cladding removal part 13 Washing machine 14 Washing machine water tank 15 Washing machine rotating tank 16 Solution concentration measuring device using optical fiber 17 Water supply hose 18 Drainage hose

Claims (5)

[Claims] An optical fiber having a clad portion partially removed in a longitudinal direction; a light source for inputting an optical signal to the optical fiber; a light receiving device for receiving the optical signal emitted from the optical fiber; The optical fiber comprises a clad removing portion and a water tank containing a solution for measuring the concentration, wherein the optical fiber has a core portion made of a thermosetting resin, and the clad portion made of a synthetic resin tube. A solution concentration measuring apparatus using an optical fiber, wherein the precursor of the core portion is injected after forming the synthetic resin tube of the cladding portion, and then obtained by heating and curing. . 2. The apparatus according to claim 1, wherein the light source is an LED (Light Emitting Diode). 3. The apparatus according to claim 1, wherein the light receiver is a photodiode. 4. The apparatus according to claim 1, wherein the solution is an aqueous solution in which a detergent for washing clothes is dissolved. 5. The apparatus according to claim 1, wherein the water tank is attached to a washing machine for washing clothes.