JPH0658324B2 - Fluid refractometer and fluid density meter using the same - Google Patents

Description

TECHNICAL FIELD The present invention relates to a fluid refractometer and a fluid densitometer using the same, and it is possible to sample a sample fluid by directly immersing a sensor probe in the sample fluid. Instead, it enables direct online measurement of the refractive index and density of the sample fluid.

[Prior Art and its Problems] Conventionally, as an apparatus for measuring the refractive index of a fluid such as a liquid or a gas, the Abbe method for measuring the refraction angle of light by a prism, the minimum deviation method, and the refractive index of a sample are used. There are many known refractometers based on the law of light refraction such as the Duc de Chorne method for measuring the focal length.

However, in any of the liquid refractometers described above, the sensor unit for detecting the refractive index of the sample is directly connected to another device, and it is difficult to separate only the sensor unit. Therefore, since the sample liquid has to be sampled each time at the time of measurement, it has been impossible to constantly measure the refractive index of the liquid online.

Further, when the density is directly measured from the sample liquid, it is more difficult to sample, and even if the fact that the density of the liquid is given by the refractive index is used, the refractive index of the liquid is always online as described above. Since it is impossible to measure, constant online measurement of density was also impossible.

The present invention has been made to solve the above problems,
An object of the present invention is to provide a fluid refractometer and a fluid densitometer using the same, in which only the sensor probe is directly immersed in the sample fluid to constantly measure the refractive index of the fluid online.

[Means for Solving the Problem] The present invention relates to a first light guide that guides measurement light from a light source in a sensor probe in which a measurement unit that contains a fluid is formed, and a first light guide that guides the light. An optical branching device that splits the measured light into test light and reference light, a second light guide that guides the test light, a third light guide that guides the reference light, and a second light guide. The test light guided by the third light guide and the reference light guided by the third light guide are superposed and interfered with each other, and the interference light produced by the superposition by the concentrator is moved by the moving order of the interference fringes. An image fiber that guides light to a detection unit that obtains a refractive index based on the above, and a compensating plate that is provided in the second light guide or the third light guide and adjusts the optical path length are accommodated to guide the test light The measurement unit was exposed in the middle of the second light guide. That was the solution.

In addition, the fluid densitometer of the present invention includes a first light guide that guides measurement light from a light source, and a measurement that is guided by the first light guide, in a sensor probe in which a measurement section that contains a fluid is formed. An optical branching device that splits light into a test light and a reference light,
A second light guide for guiding the test light, a third light guide for guiding the reference light, a test light guided by the second light guide, and a reference guided by the third light guide. A concentrator for superimposing and interfering light with each other; an image fiber for guiding the interference light generated by superimposing the concentrator to a detection unit for obtaining a refractive index based on the moving order of the interference fringes; Of the light guide or the third light guide for accommodating the compensating plate for adjusting the optical path length, the measurement unit is exposed in the middle of the second light guide that guides the test light. A means for solving the problem is to connect an arithmetic unit for arithmetically calculating the density of the sample fluid from the measured refractive index to the detection unit.

[Operation] A first light guide for guiding the measurement light and a measurement light guided by the first light guide are used as the test light and the reference light in a sensor probe having a measurement section containing a fluid. Optical splitter for splitting, second light guide for guiding test light, third light guide for guiding reference light, test light and third light guided by second light guide Since the concentrator that superimposes and interferes with the reference light guided by the guide is housed, only the sensor probe can be directly immersed in the sample fluid without sampling the fluid during measurement. The refractive index of the fluid can be measured with.

Furthermore, since the calculation unit is connected to the detection unit, the density of the fluid can be calculated from the measured refractive index of the fluid, and the density of the fluid can be constantly measured online.

[Examples] Hereinafter, the present invention will be described in detail.

FIG. 1 shows an embodiment in which the present invention is used to measure the refractive index of a liquid. In this liquid refractometer, when a measuring section for containing the sample liquid is exposed in the middle of the second light guide contained in the sensor probe, the refractive index of the sample liquid contained in the measuring section causes the refractive index of the second light guide to change. Since the optical path length changes, the interference fringes generated when the test light guided by the second light guide and the reference light guided by the third light guide are superposed is used to change the sample liquid. The refractive index of the transparent material is determined by using Jaman interference in the method of measuring the refractive index of a transparent material.

This liquid refractometer has a light source 1 at one end and an optical splitter 2 at the other end.
First light guide 3 to which the
The second light guide 4 and the third light guide 5 through which the measurement light split by the above is guided, and the image fiber 8 having the detection unit 6 attached to one end and the objective lens 7 attached to the other end.
And a sensor probe 10 having a measurement hole 9 formed on its side surface.
It is generally constructed by being housed inside.

The sensor probe 10 guides the measuring light from the light source 1, and generates an interference fringe in the measuring light divided by the one end of the first light guide 3 to which the optical branching device 2 is connected and the optical branching device 2. A second light guide 4 and a third light guide 5, and a concentrator 14 for superposing the test light and the reference light guided in the second light guide 4 and the third light guide 5. The first light guide 3 and the image fiber 8 are tube bodies for accommodating one end portion of the image fiber 8 to which the objective lens 7 for converging the interference light generated by being superimposed by the concentrator 14 is attached. Is stored in a tubular protective member made of stainless steel or the like in order to protect it from extremely low temperatures such as liquefied gas and external stress.

Further, on the side portion of the sensor probe 10, there is formed a measuring portion 9 composed of a concave portion whose long side extends in the axial direction of the sensor probe 10 and whose short side extends in the circumferential direction.
An emitting lens 11 and a light receiving lens 12 are attached to the wall surfaces of the two short sides facing each other of the measuring unit 9 so as to face each other. The second light guide 4 is connected so as to pass through 9.

In addition, the first light guide 3, the second light guide 4,
A low-loss optical fiber is used for the third light guide 5, and a large number of core / clad optical fibers suitable for transmitting an image are bundled and aligned in phase as the image fiber 8. .

Further, the first light guide 3 and the image fiber 8 housed in the sensor probe 10 are guided through a protective tube 13 formed by extending a protective member of the sensor probe 10,
The light source 1 is connected to the first light guide 3, and the detection unit 6 is connected to the image fiber 8.

The light source 1 is composed of a lamp and a monochromatic filter, and in order to obtain monochromatic light having a long coherence length, light having a wavelength of 5461Å emitted from a mercury lamp is bright and easily used, but is preferably used. In addition to this, monochromatic light emitted from a cadmium lamp, an atomic beam, an LED, a laser, or the like is preferably used.

The measuring light emitted from such a lamp is separated into monochromatic light by a monochromatic filter, and then the first light guide 3
Is guided to the sensor probe 10. The measurement light guided in the sensor probe 10 is split into a test light and a reference light by the optical branching device 2 connected to one end of the first light guide 3, and the measurement light and the second light guide 4 are separated. It is guided in the light guide 5 of 3.

Further, the ends of the second light guide 4 and the third light guide 5 are brought close to each other by the concentrator 14 so that the emitted test light and reference light are superposed on the objective lens 7 to generate interference fringes. Are focused.

The objective lens 7 is attached to one end of the image fiber 8 and is provided with a gap having a focal length of interference fringes generated by the test light and the reference light, and the second light guide 4 is provided.
The third light guide 5 and the third light guide 5 are arranged so as to face the concentrator 14 in which the third light guide 5 and the third light guide 5 are converged.

Further, the second light guide 4 is provided with a compensating plate 15 for adjusting the optical path length. The compensating plate 15 is for eliminating the optical path difference between the second light guide 4 and the third light guide 5 so that interference fringes are generated by the two measurement lights superimposed on the objective lens 7. Parallel plane glass plate,
Alternatively, it is arranged so as to be inclined with respect to the optical path. The compensator 15 may be provided on the third light guide 5.

In addition, the detection unit 6 connected to the other end of the image fiber 8
Has a built-in image monitor, an image recognition system device, and the like. After receiving and detecting the interference fringes image-transmitted by the image fiber 8, the refractive index of the sample liquid and the refractive index of the sample liquid are determined by the moving fringe order of the detected interference fringes. Density is calculated.

In order to measure the refractive index of a liquid such as a liquefied gas at an extremely low temperature using the liquid refractometer of the present invention having such a configuration, the angle of the compensating plate 12 is set in the atmosphere so that interference fringes are generated on the objective lens 7. After the adjustment, the sensor probe 10 is immersed in a sample liquid such as liquefied gas.

Next, after the lamp in the light source 1 is made to emit light and the wavelength is selected by the monochromatic filter, the light is guided into the sensor probe 10 by the first light guide 3 to be the measurement light. The measurement light is split into a test light and a reference light by the optical branching device 2, guided through the second light guide 4 and the third light guide 5, and then focused by the focusing device 14. The test light and the reference light emitted from the concentrator 14 are superimposed so as to generate interference fringes on the objective lens 7, but when the sensor probe 10 is immersed in the sample liquid, the test light is transmitted through the sample liquid. Therefore, the optical path length of the second light guide 4 becomes different from the optical path length when the compensator 15 is adjusted in the atmosphere, and interference fringes of different orders from those when the compensator 15 is adjusted are generated. Occurs.

The interference fringes having an order different from that of the compensation plate 15 at this time are condensed by the objective lens 7 connected to one end of the image fiber 8 and then transmitted to the detecting portion 6 in the image fiber 8. To be done. In the detector 6, the moving fringe order of the transmitted interference fringes is measured and calculated using the following formula (1) to obtain the refractive index n of the sample liquid.

n = (λ / l) N + 1 (1) where λ is the wavelength of the measurement light, l is the length of the long side of the measuring unit 9, and N is the moving fringe order of the interference fringes.

Next, an example of using the present invention to measure the density of a liquid will be described.

In this liquid densitometer, the calculation unit 16 connected to the detection unit 6
Then, the density is calculated from the refractive index of the sample liquid measured by the above liquid refractometer. This calculation unit 1
Reference numeral 6 is installed outside the sensor probe 10 of the liquid refractometer, always receives online the refractive index of the sample liquid measured by the liquid refractometer, and calculates the density of the sample liquid from the refractive index data. It is a thing.

In the liquid densitometer having such a configuration, first, the refractive index of the sample liquid is measured by the detecting unit 6 of the liquid refractometer described above, and then the data of the refractive index of the sample liquid is connected to the calculating unit 16 connected to the detecting unit 6. Then, the density ρ of the sample liquid can be obtained by using the following equation (2).

ρ = (n ² −1) / r (n ² +2) (2) where ρ is the density of the sample liquid, and n is the refractive index of the sample liquid.

 r: relative refractive index difference of sample liquid.

As described above, in the examples, the case of measuring the liquid has been described, but the same can be applied to the measurement of the refractive index and the density of the gas.

[Effects of the Invention] As described above, the fluid refractometer of the present invention includes the first light guide for guiding the measurement light from the light source and the first light guide in the sensor probe in which the measurement section for containing the fluid is formed. An optical branching device that splits the measurement light guided by the light guide into test light and reference light, a second light guide that guides the test light, and a third light guide that guides the reference light. A concentrator for superimposing and interfering the test light guided by the second light guide and the reference light guided by the third light guide,
The interference light generated by being superposed by this concentrator is provided on the image fiber for guiding the interference light to the detection unit for obtaining the refractive index based on the movement order of the interference fringes, and the second light guide or the third light guide. Since the compensator for adjusting the optical path length is accommodated and the measuring section is faced in the middle of the second light guide for guiding the test light, only the sensor probe having the measuring section is directly connected. It becomes possible to immerse in the sample fluid.

Therefore, without sampling the fluid during measurement,
Since the sensor probe can be directly immersed in the sample fluid, the refractive index measurement of cryogenic liquid such as liquefied gas, which cannot be normally sampled, can be always performed online.

Further, in the fluid densitometer of the present invention, since the operation unit for calculating the density from the measured refractive index of the sample fluid is connected to the detection unit of the fluid refractometer, the density can always be measured online. Since it is possible, it is particularly useful for production of liquefied gas and the like and quality control.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an example of a liquid refractometer of the present invention and a liquid density meter using the same. 2 ... Optical splitter, 3 ... First light guide, 4 ... Second light guide, 5 ... Third light guide, 6 ... Detection unit, 8 ... Image fiber, 9 ... Measurement Part, 10 ... Sensor probe, 14 ... Concentrator, 16 ... Calculation part.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazuo Sanada 1440 Rokuzaki, Sakura-shi, Chiba Fujikura Electric Cable Co., Ltd.Sakura factory (72) Inventor Kazumi Oni 20 (72) Inventor, 4273 Fujisawa, Kanagawa Kenji Nakamura 1-15-10 Honkitakata, Ichikawa-shi, Chiba (56) References JP 62-285027 (JP, A) JP 60-201238 (JP, A)

Claims (2)

[Claims] 1. A first light guide for guiding a measuring light from a light source, and a measuring light guided by the first light guide as a test light in a sensor probe formed with a measuring section for containing a fluid. An optical branching device that splits the reference light, a second light guide that guides the test light, a third light guide that guides the reference light, and a test light that is guided by the second light guide. A concentrator that superimposes and interferes with the reference light guided by the third light guide, an image fiber that guides the interference light that is generated by being superposed by the concentrator to the detection unit, and a second light. A compensating plate for adjusting the optical path length, which is provided in either one of the guide and the third light guide, is accommodated, and the measurement unit is exposed in the middle of the second light guide that guides the test light, and the detection is performed. Part, measuring the interference fringe movement order of the interference light,
A fluid refractometer characterized by calculating the refractive index of a fluid from this. 2. A first light guide for guiding the measuring light from a light source, and a measuring light guided by the first light guide as a test light in a sensor probe formed with a measuring section for containing a fluid. An optical branching device that splits the reference light, a second light guide that guides the test light, a third light guide that guides the reference light, and a test light that is guided by the second light guide. A concentrator that superimposes and interferes with the reference light guided by the third light guide, an image fiber that guides the interference light that is generated by being superposed by the concentrator to the detection unit, and a second light. A compensating plate for adjusting the optical path length, which is provided in either one of the guide and the third light guide, is accommodated, and the measurement unit is exposed in the middle of the second light guide that guides the test light, and the detection is performed. Part, measuring the interference fringe movement order of the interference light,
A fluid densitometer characterized in that a calculation unit for calculating the refractive index of the fluid from this and calculating the density of the fluid from the refractive index obtained by the detection unit is connected to the detection unit.