JPH06258130A - Level meter - Google Patents

Abstract

PURPOSE:To exactly and stably measure the level of the content contained in a vessel such as a tank regardless of presence of any disturbance such as change of inside temperature and an air current with a simple and inexpensive constitution. CONSTITUTION:A light wave guide part 5 such as a optical fiber bundle 5A passively or actively bringing a light state change in accordance with change of the level of the content 2 and a light receiving part 6 such as a CCD which can catch its light state change as the change of the level are combined.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a level meter used for measuring the surface level of the contents of various substances such as liquids and powders contained in containers such as tanks and hoppers. .

[0002]

2. Description of the Related Art A conventionally known level meter of this type is one in which a metal rod is inserted into the contents in a vertical position and is contacted with the metal rod by utilizing a change in capacitance. The ultrasonic pulse is emitted from the capacitive level meter that measures the amount of the contents (surface level) or the ultrasonic pulse transmitter / receiver toward the surface of the contents. The distance d from the sensor to the surface of the content is determined by the time it takes for the object to be reflected on the surface of the content and be received by the transmitter / receiver again and the sound wave propagation velocity (sound velocity) c.
Is calculated by d = (t / 2) c, and then the level h of the content is calculated from the calculated distance value d, h = L−d, where L is an ultrasonic wave that is measured by a known value. There is an expression level meter.

[0003]

Among the conventional level meters as described above, in the case of the capacitance type, the level measurement range is limited, and if the measurement accuracy is increased, the configuration becomes complicated. , The device becomes larger. Further, in the case of the ultrasonic type, the sound velocity changes due to disturbances such as changes in temperature, humidity, atmospheric pressure, and air flow inside the container, and the change directly causes a measurement error, which makes it difficult in principle to constantly measure the level. In addition, in order to perform accurate level measurement, in order to correct the sound velocity due to the change in the conditions in the container as described above, the temperature is measured using a temperature sensitive element such as a thermistor, and the temperature of the sound velocity is corrected. However, in this case, the configuration becomes complicated. If the correction means is provided to cope with changes in conditions other than temperature, there is a problem that the configuration becomes more complicated and expensive.

The present invention has been made in view of the above-mentioned circumstances, and has a simple structure, but a predetermined level measurement can be performed irrespective of the presence or absence of disturbance such as a change in temperature or air flow in the container. The purpose is to provide a level meter that can be accurately measured.

[0005]

In order to achieve the above object, a level meter according to claim 1 of the present invention responds to a change in level of a illuminator for illuminating the inside of a container for storing contents. The optical waveguide part that passively or actively changes the light state, and the light receiving part that can capture the change in the light state by the optical waveguide part as a level change.

Further, in a level meter according to a second aspect of the present invention, a large number of optical fibers having different lengths are arranged such that one end thereof is linearly aligned and the other end thereof is located on a hypotenuse inclined with respect to the straight line. As described above, the optical fiber bundles that are densely arranged side by side in a plane are folded in multiple stages in the direction in which the optical fibers are arranged, and the folded optical fiber bundles are arranged in the container in a vertical posture with the hypotenuse side of the optical fiber bundle at the bottom. In addition, the light receiving unit is configured by a CCD having pixels in which the outputs of the respective optical fibers of the folding optical fiber bundle enter different positions.

[0007]

According to claim 1 of the present invention, not only the optical waveguide portion guides light but also the cross-sectional area of the light guided to the light receiving portion and the light intensity when the level of the contents in the container changes. , The cross-sectional shape, polarization direction, color, modulation, etc. will result in changes in the state of the light. In this way, the change in the state of the light introduced by the optical waveguide section is captured as the change in the level in the light receiving section. Therefore, the level of the contents can be accurately measured regardless of whether there is a disturbance such as a change in the temperature or the air flow inside the container by simply guiding the light with different incident light levels as the level of the contents in the container changes. It is possible to

Further, as described in claim 2, by combining and using the optical waveguide section made of the folded optical fiber bundle and the light receiving section made of CCD having the pixels where the outputs of the respective optical fibers enter the different positions, It is possible to improve the measurement accuracy of the bell, and it is possible to maintain the measurement accuracy sufficiently high even if the level measurement range is increased.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram showing an embodiment of the present invention. In FIG. 1, reference numeral 1 is a level meter, which is a container 3 such as a tank for accommodating contents 2 such as powder particles and liquids.
It is placed in a vertical position at a position closer to one side. Four
Is an illuminator that is attached to the upper wall of the container 3 at a position closer to the other side and illuminates the entire area of the container 2. The level meter 1 includes an optical waveguide section 5 and a light receiving section 6 arranged at the upper end of the optical waveguide section 5.

As shown in FIG. 2, the optical waveguide section 5 is made of plastic or quartz glass having heat resistance and has a large number of optical fibers 5a having different lengths. The other ends are closely arranged in a plane so as to be positioned along the hypotenuse inclined with respect to the straight line, and they are sandwiched and held between the two non-translucent thin films 5b and 5b facing each other. The optical fiber bundle 5A is formed by folding the optical fibers 5a ...
Are arranged in the container 3 in a substantially vertical posture so that the hypotenuse side thereof is located in the lower part, so that the upper and lower zigzag light incident portions 7
Is being formed. In the optical waveguide section 5 including such a folded optical fiber bundle 5A, the cross-sectional area of light to the light-receiving section 6, the intensity of light, the shape of the cross-sectional area, and the like are determined according to the change in the level of the contents 2. , It will bring about a change of light state either passively or actively.

When a color filter or a polarization film is attached to each of the optical fibers 5a, it is possible to change the polarization direction, color, modulation, etc. to the light receiving section 6. Further, when the zigzag-shaped light incident portion 7 at each end of each of the optical fibers 5a in the optical fiber bundle 5A is flatly molded with a transparent resin having elasticity, the obstruction of the optical waveguide function due to adhesion of the glue is eliminated. be able to.

Further, as shown in FIG. 3, the light receiving portion 6 is a CCD having pixels, generally 768 × 493 pixels, in which the outputs of the respective optical fibers 5a ... In the optical fiber bundle 5A are incident on different positions. The image of the CCD 6 is as shown in FIG.
In FIG. 1, under the condition that the portion that always receives light is a and the portion that does not always receive light is b, the portion a of the image of the CCD 6 is bright and the portion b is dark.
The portions corresponding to the above-mentioned portions a and b are as shown in FIG.

Therefore, the output of the CCD 6 is represented as shown in FIG. Here, letting La be the amount of light incident on the portion a and Lb be the amount of light incident on the portion b, the threshold level Lth
Lth = (La + Lb) / 2 (1) When the amount of incident light is larger than the threshold level Lth obtained by the equation (1), there is incident light, and when the amount of incident light is smaller than the threshold level Lth, there is no incident light. In addition to such calibration, a histogram (corresponding to the x and y coordinates of the CCD) may be taken based on the amount of incident light corresponding to each optical fiber 5a, and the optimum level may be calculated by discriminant analysis. To be

The level calculation method will be briefly described below. The output of each optical fiber 5a in the optical fiber bundle 5A is input to different positions of the CCD 6. Here, the CCD is larger than the diameter of the optical fiber 5a.
When the number of pixels of 6 is small, the level measurement accuracy improves as the number of bundles of the optical fibers 5a increases.
For example, the general 768 × 493 pixel CCD described above
When 6 is used, assuming that the outer diameter of one optical fiber 5a is about 0.3 mm and the CCD 6 is (2/3) inch, the equation (2) is obtained, and 1600 level determination is possible.

[0015]

[Equation 1]

Further, the measurement range can be widened by increasing L in FIG. For example, using the CCD 6 described above, the level accuracy is 10 m / 1600 = 6.25 mm even if the measurement range is 10 m. This is practically sufficient. That is, the number of pixels corresponding to one optical fiber 5a is as shown in FIG.
The number of pixels is about 230 pixels or more, and the number of pixels is sufficient for conversion into the distance only by measuring the area.

FIG. 8 is a block diagram showing a configuration of a signal processing system circuit in the level meter 1 having the above-described configuration. In FIG. 8, reference numeral 8 is an A / D converter for the fiber light received by the CCD 6. The image c is converted into a digital image d based on the synchronizing signal a from the synchronizing circuit 9. 1
Reference numeral 0 is a threshold value generating circuit, 11 is a comparator, which outputs a threshold value e output from the threshold value generating circuit 10 and the A / D converter 8 based on the synchronization signal b from the synchronization circuit 9. The pixel value of the digital image d is compared. Reference numeral 12 is a pixel counter, which counts the output pixel value f from the comparator 11 and outputs the count value g via the output circuit 13.
Output as a predetermined level.

FIG. 9 shows the threshold value generation circuit 1 in FIG.
FIG. 11 is a block diagram showing a specific configuration of 0, in which the threshold value generation circuit 10 detects a maximum value (max) of a digital image d having a waveform as shown in FIG. A circuit 14, a second peak hold circuit 16 for detecting the maximum value (max1) of the digital image d inverted through the sign inversion circuit 15 as shown in FIG. 10B, and the second peak hold circuit. FIG. 10 in which the output from 16 is inverted through the sign inversion circuit 17.
The minimum value (min) as shown in (c) and the maximum value (m
ax) and an addition value (max +
min) divided by the division value α, that is, (max + min)
And a division circuit 19 for calculating / α,
The output from this division circuit 19 becomes the above-mentioned threshold value e. For example, when α = 2, the threshold value e becomes an intermediate value between the maximum value (max) and the minimum value (min), and coincides with the threshold level Lth obtained by the above equation (1).

In the above embodiment, as the light receiving section 6,
Although the case where the CCD is used has been described, the same effect as that of the above-described embodiment can be obtained by using the PSD (laser) or the like. Further, in the above-mentioned embodiment, the present invention is applied to the level measurement of the contents stored in the tank 2. However, even if it is applied to the level measurement of the contents stored in the hopper or any other container, Has the same effect.

[0020]

As described above, according to the first aspect of the present invention, not only the light is guided, but also when the level of the contents in the container changes, the cross-sectional area of the light guided to the light receiving portion, the light Strength, cross-sectional area shape, polarization direction, color, modulation, etc.,
By combining and using an optical waveguide section that causes a change in the state of light and a light receiving section that captures the change in the state of the light introduced by this optical waveguide as a change in level, the configuration is simple and inexpensive. However, the level of the contents can be accurately and stably measured regardless of the presence or absence of a disturbance such as a change in temperature or air flow inside the container. It

According to a second aspect of the present invention, by combining and using the optical waveguide section made of the folded optical fiber bundle and the light receiving section made of CCD having the pixels where the outputs of the respective optical fibers enter different positions, It is possible to improve the measurement accuracy of the bell, and it is possible to maintain the measurement accuracy sufficiently high even if the level measurement range is increased.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a level meter according to an embodiment of the present invention.

FIG. 2 is a perspective view showing a specific configuration of an optical waveguide section.

FIG. 3 is a perspective view of a main part for explaining a CCD that constitutes a light receiving part.

FIG. 4 is an explanatory diagram of a CCD image.

FIG. 5 is a diagram illustrating a portion of an optical fiber bundle corresponding to light and darkness of a CCD image.

FIG. 6 is an explanatory diagram schematically showing the output of a CCD.

FIG. 7 is an explanatory diagram of a relationship between the number of pixels corresponding to one optical fiber and level accuracy.

FIG. 8 is a block diagram showing a configuration of a signal processing system circuit in the level meter.

9 is a block diagram showing a specific configuration of a threshold value generation circuit in FIG.

FIG. 10 is an image waveform diagram showing the operation of FIG.

[Explanation of symbols]

 1 Level meter 2 Contents 3 Container 4 Lighting fixture 5 Optical waveguide part 5A Optical fiber bundle 5a Optical fiber 6 CCD (light receiving part)

[Procedure amendment]

[Submission date] October 20, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be amended] Claims

[Correction method] Change

[Correction content]

[Claims]

Claims (2)

[Claims] 1. A illuminator for illuminating the inside of a container for storing contents, an optical waveguide section for passively or actively changing the state of light in response to a change in the level of the contents, and the optical waveguide section. A level meter comprising: a light receiving section capable of capturing a change in light state as a change in level. 2. The optical waveguide portion is a flat surface in which a plurality of optical fibers having different lengths are linearly aligned at one end thereof and each other end is located on a hypotenuse inclined with respect to the straight line. The optical fiber bundles that are arranged closely in parallel with each other are folded in a plurality of stages in the direction in which the optical fibers are arranged, and the folded optical fiber bundles are arranged in a container in a vertical posture with the hypotenuse side of which is located at the bottom. The light receiving unit has a CC having pixels in which outputs of the respective optical fibers of the folding optical fiber bundle enter different positions.
The level meter of claim 1, wherein the level meter comprises D.