JPS60174930A - Densitometer - Google Patents

Abstract

PURPOSE:To make it possible to detect the concn. of a high concn. suspended substance, in the optical measurement of the concn. of the suspended substance contained in waste water, by allowing laser beam to be incident to the interface of a measuring liquid and detecting the size of the beam image generated to an interface by reflected and scattered beam of said laser beam. CONSTITUTION:Laser beam 4 of He or Ne is incident to the interface 8 of a liquid 1 containing a suspended substance and a glass plate 7 from a beam source 5, and reflected and scattered by the suspended substance to generate a circular beam image 6 at the interface 8. As the concn. of the suspended substance becomes high, the radius of the beam image 6 becomes small. Hereupon, an optical fiber 9 is arranged in the radius direction of the beam image to detect the size of the radius of the beam image and the concn. of the suspended substance is operated by an operation apparatus 13. Because measuring beam is projected to the interface to detect the beam image, this measuring mechanism is different from a method for measuring the attenuation of beam transmission by the suspended substance and even the high concn. suspended substance can be measured with high accuracy.

Description

[Detailed description of the invention] [Technical field to which the invention pertains] The present invention relates to a densitometer that optically measures the concentration of suspended matter contained in wastewater in industrial fields such as fermentation, food, pulp, etc. Measurements up to high concentrations can be carried out without clogging due to partially suspended particles, and the measurement results can be transmitted directly to waste water.
The present invention relates to a densitometer which can be prevented from being affected by dirt on the contact part.

[Prior art and its problems]

Conventionally, many optical methods have been adopted to measure the concentration of suspended matter in liquids, but these methods can be broadly classified into transmitted light methods and scattered light methods, and each conventional method is explained below. There is a problem like that.

In other words, the transmitted light method measures the attenuation of light transmitted through a liquid, but this method uses a light source with a high emission intensity because the amount of attenuation of transmitted light increases as the degree of suspension 7 increases. There are measures to be taken, such as using a high-sensitivity light-receiving element, or narrowing the flow path for the liquid sample in the detection part to shorten the optical path length of the light that traverses and passes through it. Since this flow path may be clogged with turbid matter, the upper limit concentration in this measurement method is usually set to be about 1 inch in terms of dry concentration. That is, the transmitted light method has a problem in that the upper limit of the measurable dry concentration is about 1%, and if the concentration is higher than this, the sample flow path may be clogged.

On the other hand, the scattered light method measures the light scattered by suspended objects in the light projected into the liquid. In this method, as in the case of transmitted light 2, as the concentration of suspended objects increases, the intensity of the scattered light decreases. (Therefore, there are problems such as having to increase the emission intensity of the light source or increasing the sensitivity of the light receiving element.If the scattered light intensity is weak (if the stray light other than the scattered light that enters the light receiving element cannot be ignored (because of this, a method called the scattered light comparison method is sometimes adopted in which scattered light from - number of light sources is detected at two locations and the results of both detections are compared, but measurement is possible even in this case. The upper limit concentration is approximately 1% at most in terms of dry concentration, and there is a problem in that suspended matter concentrations higher than this cannot be measured.

Although the above are problems specific to each of the measurement methods mentioned above, a problem common to both of these methods is that since both methods are optical measurement methods, the wall of the measurement cell that constitutes the detection section There is also the problem that when so-called contamination occurs due to the adhesion of suspended matter to the surface, the intensity of the transmitted light changes, resulting in a large measurement error.

[Purpose of the invention]

The present invention solves the problems with the densitometer that uses the conventional optical measurement method described above to measure the concentration of suspended matter in a liquid. It is an object of the present invention to provide a densitometer for measuring the concentration of suspended solids, which is free from the risk of occurrence of turbidity, and which also prevents measurement results from being affected by contamination of parts in contact with the liquid due to suspended solids. It is something.

[Key points of the invention]

In order to achieve the above-mentioned object, the present invention uses a light source device to generate a beam-like measurement light sound, such as a laser beam. At least a part of a circular or elliptical optical image generated at the interface by reflection and scattering of the beam-shaped measurement light incident on the liquid is transmitted to a location different from the interface by an optical transmission means. , detection section f
tK, the size of the light image is detected by receiving the light transmitted through the light transmission means, and in this case, the size of the light image is constant with the concentration of suspended matter in the liquid. In addition, since the light source device has the following relationship, a calculation device is provided which performs calculations on the output signal of the detection device according to the size of the light image and outputs a signal according to the suspended matter concentration, and such a light source device , a light transmission means, a detection device, and an arithmetic device constitute a concentration meter for measuring the concentration of suspended matter. By configuring the concentration meter in this way, it is possible to In this case, the part of the densitometer that comes into contact with the liquid is not blocked by suspended matter (and the light-receiving part constituting the detection device is directly opposed to the interface without having an optical transmission means). It is designed to be able to measure higher concentrations than a densitometer designed to do so, and it also allows measurement results to be obtained without being affected by contamination of the wetted parts due to suspended matter. This is what I did.

[Embodiments of the invention]

Next, embodiments of the present invention will be described with reference to the drawings, but first, the operating principle of the densitometer according to the present invention will be explained. 1st
The figure is a basic diagram of the operating principle. In the figure, 1 is a liquid containing suspended matter to be measured, 2 is a gas such as air that is above liquid 1 and in contact with the liquid in parentheses, and 3 is a liquid l
and gas 2. The gas 2 may be a translucent solid such as glass. 5 is a narrow beam-like measurement light 4fI like a laser beam! : A light source device that emits light, and the light source device 5 is arranged so as to project the measurement light 4 from the gas 2 side almost perpendicularly to the interface 3.

In the figure, the measurement light 4 is spatially transmitted, but it may also be transmitted through an optical fiber. When a translucent solid is provided in this part instead of the gas 2K, the light source device 5 may be arranged so as to transmit the light 4 to the interface 3 after passing through this solid. The light 4 does not necessarily need to be projected perpendicularly to the interface 3. P is light 4 and interface 3
It is the intersection with

When the measuring light 4 is projected onto the liquid l as shown in Figure 1,
A part of this light is absorbed by the liquid 1, and the rest is reflected and scattered within the liquid 1. As a result, a circular light image 6 centered at the point P is generated at the interface 3, and the size of this light image 6 is varies depending on the concentration of the suspended matter in liquid 1. According to experiments conducted by the present inventor, when the liquid 1 is sewage containing sludge as a suspended matter and an ie-Ne laser (with an output of 1 mW) is used as the light source device 5, it was found that when the drying degree of the sludge was 5 degrees, the light 1#! 6 had a diameter of approximately 101 K, and when the sludge dry concentration was 0.5 cm, the diameter of the optical image was approximately 40 cm. Figure 2 is a schematic diagram of the observation results of the light intensity distribution in this light source 6. In the figure, R is the distance from point P, and ■ is the distance from point P to b. H, M, and L are the characteristic lines when the concentration of suspended matter in the liquid 1 is high, midsummer, and low, respectively. It is clear from the figure that the light image becomes smaller and the light intensity at the center becomes stronger when the turbidity concentration is high.

S is 1 = so that it intersects both the characteristic lines H9M and L.
The characteristic line set for I s, A, B, and C are the characteristic line S)
I in the characteristic line S at the intersection with each characteristic line i, M, L
s is point A, kl.

The distance ratio corresponding to C becomes shorter as the suspended solids concentration increases. Figure 3 shows points A, B, and C in Figure 2.
The relationship between the distance ratio value Rs corresponding to the point on the characteristic line S of This is even more obvious.

As is clear from Fig. 2, Rs represents the size of the light image 6 in Fig. 1, so Fig. 3 shows the relationship between the size of the light image 6 and the concentration of suspended matter. Since there is such a certain relationship between the two, it is possible to know the concentration by measuring Rs.

In the above explanation, the light beam 4 was projected perpendicularly to the interface 3. When the light beam 4 is obliquely projected onto the field thr3, the optical image 6 becomes an ellipse. ° However, in this case too the size of the ellipse changes depending on the ms- of the suspension. Therefore, in this case, the suspension skin can be determined, for example, by measuring the length of the long axis of the ellipsoidal light image. As described above, the densitometer of the present invention measures the concentration of suspended matter by measuring the size of the circular or elliptical light image generated at the interface when the beam light 4 is projected onto the interface 3. The measurement principle is to

FIG. 4 is a block diagram of an embodiment of a #meter according to the present invention which applies the above-mentioned operating principle. In the figure, 7 is a glass plate forming a part of the wall surrounding the liquid 1, and 8 is a glass plate 7
This is the interface between the liquid 1 and the liquid 1.

In this case, the light source device 5 is arranged so as to project the measurement light 4 substantially perpendicularly onto the interface 8 via the glass plate 7, and in this case also produces a circular light image 6 on the interface 8. Q is the intersection of the light 4 and the surface of the glass plate 7 on the light source device 5 side. Reference numeral 9 denotes an optical fiber bundle in which a large number of optical fibers are arranged and fixed on the same flexible substrate so that adjacent ones of the optical fibers are in contact with each other, and both end surfaces of this original fiber bundle 9 are Each of the optical fiber bundles 9 is formed so as to be on one plane, and one end face of the optical fiber bundle 9 is on a plane with a point Q on the glass plate 70 and on a half straight line radiating from the point Q. The other end surface of the optical fiber bundle 9 has a photoelectric conversion section 1 formed by arranging a plurality of photodiodes in a row.
It is still connected to 0 and is fixed. The optical fiber bundle 9 is placed as close as possible to the point Q (as far as K) so that jt,4 is projected onto the interface 8 on the surface of the glass plate 70 where the point Q is located, and the fibers are not obstructed. Since the bundle 9 is configured as described above, it transmits at least a part of the optical image 6 to the photoelectric conversion section 10, and the photoelectric conversion section 10 converts the light emitted from each optical fiber (from each optical fiber) constituting the optical fiber bundle 9. A plurality of electric signals corresponding to the intensity of
detects the number of signals in the signal 10a corresponding to a light intensity equal to or higher than the light intensity Is explained in FIG. 2, and outputs a signal 11a adjusted to the size of the optical image 6. That is, the optical fiber bundle 9 constitutes an optical transmission means that transmits at least a part of the optical image 6 generated by the interface 81C by the measurement ft, 4 to a place different from the interface 8, for example, the photoelectric conversion unit 10, and The conversion unit 10 and the signal processing unit 11 constitute a detection device 12 that receives light transmitted by an optical fiber bundle 9 as a light transmission means and outputs a signal 11a according to the size of the optical image 6. There is. 13 is the output signal 1 of the detection device 12
1a is input, it performs calculation according to the characteristic line in FIG. 3, and outputs a signal 13a according to the concentration of suspended matter in the liquid 1. 14 is the above-mentioned light source device 5 and optical fiber bundle. 9
This is an rIk meter consisting of a detection device 12 and an arithmetic device 13.

Since the densitometer 14 is constructed as described above and has a temperature of 0.degree. C., it is possible to measure the concentration of suspended matter in the liquid 1 by means of the output signal 13a. It does not measure the degree of attenuation of light (but rather measures the size of the light image 6), so it can easily measure up to high concentrations, and it can also be used to continuously measure suspended solids concentration. When liquid 1 is made to flow near point Q, even if the concentration of suspended matter becomes high, the flow path of liquid 1 does not need to be as narrow as in the conventional optical measurement method described above. It will not be blocked by suspended matter.In Figure 4, if the interface 8 is contaminated by suspended matter, the measurement results will be affected, but the beam light 4 is projected onto the interface 3 as shown in Figure 1. Then, the gas 2 near the point P
If the end face of the optical fiber bundle 9 is placed in such a way that it faces the optical image 6, the interface 3 will not be contaminated by suspended matter, which will cause an error in the measurement results.

In FIG. 4, even if the light-receiving surface of the photoelectric converter 10 is brought into direct contact with the glass plate 7 without using the optical fiber bundle 9, the signal 11a corresponding to the size of the optical image 6 is not transmitted from the signal processor 11. However, in this case, the distance X from point Q of the point closest to point Q that can be detected by photoelectric conversion section 10 is usually about several n or more because photoelectric conversion section 10 has a considerable size. However, in the densitometer 14, an optical fiber bundle 9 is provided, and this optical fiber bundle transmits a part of the optical image 6 to the photoelectric converter 1o. 9 can be brought considerably close to point Q, and the distance Xftft or less can be made smaller than the distance Xftft. As a result, such a densitometer 14
0''k It is possible to measure a higher concentration of suspended matter than with a concentration needle brought into direct contact with the glass plate 7.

In the embodiment shown in FIG. 4, the photoelectric conversion section 10 constituting the detection device 12 is composed of a plurality of photodiodes, but this photoelectric conversion section is composed of a plurality of phototransistors, Cd8, etc. In the embodiment shown in FIG. 4, one end of the optical fiber bundle 9 is brought into contact with the glass plate 7 and fixed. The bundle 9 may not be brought into contact with the glass plate 7, but may be fixed apart from the glass plate. In the above-mentioned embodiment, both the interfaces 3 and 8 were formed in a planar shape, but the interface onto which the measurement light 4 is projected is such that the liquid 1 is surrounded by a tubular glass wall and the liquid 1 and the glass are separated. It may be formed into a curved surface like the interface formed between the optical fiber bundle 9 and the glass wall. Contacted and fixed.

FIG. 5 shows the components of a second embodiment of the densitometer according to the present invention, in which 15 is a right angle prism, 15a and 15b
is the first part of the prism 15 that sandwiches the slope 15C of the prism 15.
and a second bottom surface. The prism 15 has a first bottom surface 15a.
is fixed in the gas 2 by means not shown so as to face the optical image 6 1, and a plurality of photodiodes are arranged in a line in a direction parallel to the direction of the measurement light 4 on the second bottom surface 15b. The photoelectric conversion unit 10 is abutted and fixed with its light receiving surface facing the slope 14c. In this case prism 15
The first edge 15d between the first bottom surface 15a and the slope 15c is on the side of the measurement light 4, and is placed as close as possible to the measurement light in the parentheses, so that a part of the light image 6 is on the slope 1
5c and is transmitted to the second bottom surface 15b, and this transmission is reliably performed even if the concentration of suspended matter in the liquid 1 increases and the size of the optical image 6 becomes small. On the second bottom surface 15b, the light reflected on the slope 15c is converted into an electric signal 10a by the photoelectric converter 1o, and as a result, the arithmetic unit 13 transmits the information about the concentration of suspended matter in the liquid 1 as in the case of FIG. A corresponding signal 13a is output. That is, in this case, the prism 15
constitutes a light transmission means that transmits a part of the optical image 6 to the second bottom surface 15b as described above, and 16 includes the light source device 5, the prism 15 as the light transmission means, the detection device 12, and the calculation device 13. Then, replace the prism 15 with the slope 15c.
A reflecting mirror may be placed at the position.

Since the configuration of the densitometer 16 in FIG. 5 is as described above, it is possible to measure the concentration of suspended matter using the output signal 13a. In this case, like the densitometer 14 in FIG. It is possible to measure a higher concentration of suspended matter than a concentration meter using a conventional method, and there is no need to narrow the liquid flow path when trying to continuously measure high concentrations. Don't get stuck because of it. Furthermore, since the first bottom surface 15a is far from the interface 3 and is not contaminated by suspended matter, such contamination will not cause measurement errors in this densitometer (furthermore, in this densitometer, Since the edge i5d of the prism can be brought closer to the measurement light 4 as described above, it is possible to measure a higher density than when the photoelectric conversion section 10 is disposed at the position of the first bottom surface 15a.

〔Effect of the invention〕

As described above, the present invention includes a light source device that projects a beam-shaped measurement light onto the interface between a liquid containing a suspended substance and a gas or a solid such as a transparent glass from the gas side or the solid side. , an optical transmission means composed of an original fiber, a prism, etc., which transmits a small part of the optical image generated at the interface by this measurement light to a place different from this interface, and A detection device that receives light and detects the size of the light image, and an arithmetic device that receives the output signal of this detection device, performs calculations, and outputs a signal corresponding to the concentration of the suspended matter. Since the densitometer is configured as a densitometer for turbid substances, such a densitometer does not measure the degree of attenuation of the projected light like a densitometer using a conventional optical measurement method. It has the effect of being able to measure the concentration of suspended matter, and even if the concentration of suspended matter becomes low, there is no need to narrow the liquid flow path as in a concentration meter using a conventional optical measurement method. Another advantage is that this flow path is not blocked by suspended matter.Furthermore, in the densitometer of the present invention, a beam-shaped measurement light is used to generate an optical image on the surface of the liquid containing suspended matter. In this case, the light-receiving surface of the light transmission means facing the optical image can be constructed so as not to be contaminated by suspended matter, so that in such cases the concentration measurement results will not include errors due to contamination by suspended matter. Furthermore, in the densitometer of the present invention, without providing a light transmission means, the light receiving part of the detection device 9 is provided to directly face the light image to detect the size of the light image. Compared to the #f!meter, which measures the concentration using K, it is possible to detect the thickness of the light image immediately near the intersection of the measurement light and the interface because it is equipped with a light transmission means, and as a result, it is possible to detect the thickness of the light image immediately near the intersection of the measurement light and the interface. It has the effect of being able to measure higher concentrations than a densitometer that does not have a ton of water.

[Brief Description of the Drawings] Fig. 1 is a basic diagram of the operating principle of the densitometer according to the present invention, Fig. 2 is a diagram of the intensity distribution of light in the optical image of Fig. 1, and Fig. 3 is a diagram of the intensity distribution of light in the optical image of Fig. 2. Figure 4 is a block diagram of the first embodiment of the densitometer according to the present invention, and Figure 5 is a diagram showing the second embodiment of the densitometer according to the present invention. FIG. 1...Liquid, 2...Gas, 3.8...Interface, 4...Measurement light, 5
...Light source device, 6...Light image, 7...
... glass plate as a solid, 9 ... optical fiber bundle as a light transmission means, 12 ... detection device,
13...Arithmetic device, 14.16...Densitometer, 15...Right angle prism as a light transmission means. Figure 1 Rattan 2tiA Figure 13

Claims (1)

[Claims] a light source device that projects a beam-shaped measurement light from the gas side or the solid side onto an interface between a liquid containing a suspended substance and a gas or a translucent solid; and light generated at the interface by the measurement light. a light transmission means for transmitting at least a part of the image to a location different from the interface; a detection device for detecting the size of the optical image by receiving the light transmitted by the light transmission means; It is characterized by comprising a calculation device that performs a predetermined calculation on an output signal and outputs a signal corresponding to the concentration of the suspended matter, and that the concentration of the suspended matter is measured by the output signal of the calculation device. Densitometer.