JPH0996555A - Measuring device for storage level of storage container - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a storage level measuring device for accurately measuring storage level even in the atmosphere in a container where particles and steam are generated. SOLUTION: A main electrode 2 is hung down at a position where it directly comes into contact with a material in a storage container 1 and a correction electrode 3 is hung at a position where it does not come into direct contact with the material. Then, the electrodes are connected to a storage level operation device 4 and a capacitance detected by the main electrode 2 is corrected by the capacitance of atmosphere in the storage container 1 detected by the correction electrode 3 to calculate a true storage level.

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 a storage level in a container for storing aggregate, such as an aggregate storage bottle of an asphalt plant.

[0002]

2. Description of the Related Art For example, in a bone storage bin of an asphalt plant, the storage level is measured by using various multipoint level switches to measure the storage level of aggregate. It may be required to measure the storage level continuously.

Therefore, the principle of the capacitance type level meter will be briefly described. A substance has an inherent dielectric constant, and as shown in FIG. 2, for example, an aggregate of an asphalt mixture is formed between opposed electrodes. By interposing such a substance, the capacitance corresponding to the dielectric constant of the aggregate can be measured.

Furthermore, the fact that the permittivity of the aggregate is larger than the permittivity of the air surrounding the aggregate makes it possible to increase the effect of the permittivity of the aggregate as the storage amount of the aggregate increases. The inter-electrode dielectric constant increases, and conversely, when the aggregate storage amount decreases, the influence of the air dielectric constant increases and the inter-electrode permittivity decreases. The storage level of the aggregate can be measured by detecting the capacitance due to the change with the electrode.

Applying such a principle, a capacitance type level meter employed in an aggregate storage container or the like is composed of a single wire so as to contact the aggregate from the upper part to the lower part in the storage container. The electrode is hung down, and this electrode is used as the positive side electrode, while the inner wall of the storage container is used as the negative side electrode, and the change in the storage amount of the aggregate sandwiched between them is detected as a change in the capacitance to detect the bone. I try to measure the storage level of wood.

[0006]

However, in the above conventional storage level measuring device, as shown in FIG. 3, when a large amount of dust or water vapor is present in the storage container, the permittivity of the dust and water vapor becomes the permittivity of air. Since it is larger than air, it cannot be ignored like air, and these influences appear in the capacitance value detected by the electrode and it is added to the capacitance corresponding to the original amount of aggregate. Even if the storage level is calculated from the detected capacitance value, an error will occur.

Therefore, in a storage container for storing aggregate heated by a dryer which is a heating device of an asphalt plant, since a large amount of dust and water vapor is generated, even if a capacitance level meter is attached. The storage level cannot be accurately measured, and it is the current situation that it is rarely used.

In view of the above points, it is an object of the present invention to provide a storage level measuring device for a storage container capable of accurately measuring the storage level even in an atmosphere inside the storage container where dust or water vapor is generated. To do.

[0009]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention is a capacitance type storage level in which an electrode is inserted into a storage container to measure a storage level of a material from a change in capacitance. In the measuring device, the electrode is composed of two main electrodes and a correction electrode, the main electrode is in a position where it directly contacts the material from the upper part to the lower part of the storage container, and the correction electrode does not contact the material above the storage container. While arranging in the position,
It is characterized in that a storage level calculation device for calculating the storage level of the material is provided by correcting the capacitance detected by the main electrode with the capacitance detected by the correction electrode.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION When the storage level measuring device of the present invention is applied to, for example, an aggregate storage bin of an asphalt plant, a main electrode in direct contact with the aggregate causes an electrostatic charge according to the storage level as the aggregate increases or decreases. The capacitance is detected, and the change in capacitance in the storage container due to dust or water vapor is detected by the correction electrode that does not contact the aggregate. At this time, the capacitance value detected by the main electrode is not only the capacitance value according to the storage level of the aggregate but also the capacitance value affected by dust and water vapor in the storage container. Therefore, the storage level calculation device incorporates the capacitance detected by the main electrode and the capacitance detected by the correction electrode, and the capacitance due to dust or water vapor detected by the correction electrode is calculated from the capacitance detected by the main electrode. The true storage level of the aggregate is calculated by compensating for the offset.

[0011]

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

FIG. 1 shows a storage level measuring device of the present invention installed in an aggregate storage bin of an asphalt plant, in which a main electrode 2 having a wire rope in an electrode portion is inserted into a storage container 1 from above. It hangs down to the bottom so that it directly contacts the aggregate. In addition, a correction electrode 3 of almost the same type as the main electrode 2 is inserted in the vicinity thereof from above, and the correction electrode 3 is formed with a short wire rope in the electrode portion so as not to directly contact the aggregate. And these main electrode 2 and correction electrode 3
Acts as a positive electrode, and the inner wall of the storage container 1 acts as a negative electrode.

Further, the main electrode 2 and the correction electrode 3 are connected to a storage level calculation device 4, and the storage level calculation device 4 converts the capacitance signal taken in from each electrode into a frequency signal C / The main electrode 2 is provided with the F conversion unit 5.
A correction calculation unit 6 for performing a correction calculation on the signal from the correction electrode 3 based on the signal from the correction electrode 3, and a level calculation unit 7 for calculating the aggregate level from the corrected signal and an output unit 8 for outputting the calculated storage level. I have it.

However, when the storage level is measured by the storage level measuring device, the capacitance in the storage container 1 detected by the main electrode 2 and the correction electrode 3 is taken into the storage level calculating device 4. The detection data is shown in the graph of FIG. 4, and the electrostatic capacitance detected by the main electrode 2 becomes a high level value as shown by the one-dot chain line in the presence of dust and water vapor. Transition to. Then, the capacitance detected by the correction electrode 3 changes at the level shown by the dotted line.

The capacitance of each electrode taken in at such a level is converted into a frequency signal by the C / F converter 5 to facilitate data processing and sent to the correction calculator 6.

In the correction calculation unit 6, a high capacitance value including the capacitance value of the atmosphere in the container detected by the main electrode 2 is calculated by the capacitance value of the atmosphere in the container detected by the auxiliary electrode 3. Corrected to offset. The correction coefficient used during correction is measured in advance while changing the amount of aggregate stored in the storage container, the aggregate temperature, etc.
Various correlations are examined from the measurement result, and the correlation is appropriately determined and stored. In the graph of FIG. 4, the solid line indicates the true storage level required.

Although the main electrode 2 and the correction electrode 3 have different wire rope lengths, they use the same type of electrode and therefore have substantially the same characteristics, and each electrode has a special interface. Does not need

As described above, since the electrostatic capacity detected by the main electrode is arithmetically corrected by the electrostatic capacity of the atmosphere in the container detected by the correction electrode to calculate the true storage level, it is possible to calculate the true storage level of the asphalt plant. It is very effective for measuring the storage level in a storage container, such as an aggregate storage bottle, which is easily affected by dust and residual moisture of heated aggregate.

[0019]

As described above, in the storage level measuring device of the present invention, the electrode of the capacitance type level meter is composed of the main electrode 2 and the correction electrode 3, and the main electrode is the material in the storage container. The correction electrode is arranged at a position where it does not come into contact with the material inside the container, and these electrodes are connected to the storage level calculation device 4 so that the correction electrode 3 detects the capacitance value of the atmosphere inside the container. However, since the capacitance of the storage level affected by the atmosphere in the container detected by the main electrode 2 is offset and corrected by the capacitance detected by the correction electrode 3, the atmosphere in the storage container 1 is corrected. Even when the capacitance is strongly affected by dust and water vapor, the storage level can be accurately measured.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment in which a storage container is equipped with a storage level measuring device of the present invention.

FIG. 2 is an explanatory diagram showing the principle of measuring capacitance.

FIG. 3 is an explanatory diagram showing a principle of measuring capacitance.

FIG. 4 is a graph showing a measurement result of capacitance.

[Explanation of symbols]

1 ... Storage container 2 ... Main electrode 3 ... Correction electrode 4 ... Storage level calculation device

Claims (1)

[Claims] 1. A storage level measuring device of a capacitance type, wherein an electrode is inserted into a storage container to measure a storage level of a material based on a change in capacitance, the two electrodes including a main electrode and a correction electrode. The main electrode is arranged at a position where it directly contacts the material from the upper part to the lower part of the storage container, the correction electrode is arranged at a position where it does not contact the material on the upper part of the storage container, and the capacitance detected by the main electrode is A storage level measuring device for a storage container, comprising: a storage level calculating device that calculates a storage level of a material by correcting it with a capacitance detected by a correction electrode.