JPH10148561A - Method and device for measuring level of bulk material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the reliability in measurement values, by improving the workability at measurement, and specifying and defining measurement points at level surface of granule material. SOLUTION: A laser range finder 12 wherein, a level surface 18a of a granule material 18 irradiated with a visible light laser, a distance from the level surface is measured based on a phase-difference between the modulation signal of the irradiation light and the modulation signal of reflection light reflected on the level surface, is set at a specified position of an upper end opening 16a of a storage tank 16. The distance measured with the laser range finder 12 can be outputted to a distant output means 14.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for measuring the level of a granular material such as feed, grain, cement, sand, etc., stored in a storage tank. The present invention relates to a level surface measuring device.

[0002]

2. Description of the Related Art For example, so-called granular materials such as feed, grains, cement, sand, etc. are usually stored in a storage tank called a substantially funnel-shaped hopper or the like, and discharged from a small-diameter discharge passage provided at a lower end. Used as

Here, such a storage tank is usually
It is as high as 20-30m, and its material is made of opaque material such as iron plate, concrete, etc., so it is difficult to visually observe the volume of the granular material in the storage tank from outside. . Therefore, usually, the capacity of the granular material in the storage tank is recognized by measuring the height from the reference point to the level surface (surface) of the granular material using the upper end opening of the storage tank as a reference point. doing.

As a means for measuring the height of the level surface of a granular material, a tape measure having a weight attached to the tip is generally known. In such a tape measure, the tip of the tape measure is suspended from the upper end opening or the like of the storage tank together with the weight, and the scale of the tape measure stopped when the weight reaches the level surface of the granular material to read the scale of the tape measure. That is, the volume of the granular material in the storage tank can be recognized.

[0005]

However, the measurement of the height of the level surface of the granular material using the tape measure is not only inefficient, but also the work of hanging the tape measure from the upper end opening of the storage tank and the like, and The operator is required to read the scale and the like every time the measurement is performed, so that the burden on the operator increases. In particular, at a site having a plurality of storage tanks or at a site requiring frequent measurements, the workability is significantly reduced.

Here, the ultrasonic wave is transmitted from the upper end opening of the storage tank in the direction of the level surface of the granular material, and the ultrasonic wave reflected on the level surface of the granular material is received. A measuring device configured to measure and display the distance from the upper end opening or the like to the level surface by calculating time is disclosed in, for example, Japanese Patent Application Laid-Open No. 52-151051. In such a configuration, since the measuring device may be installed at the upper end opening of the storage tank or the like and operated when necessary to measure the height of the level surface of the granular material, the safety of the worker can be secured, The workability is improved.

By the way, the surface of the granular material accommodated in the storage tank is generally not flat, and becomes substantially mountain-shaped after being filled from the upper end opening, and substantially mortar-shaped after being discharged from the discharge passage. Therefore, when measuring the height of the level surface of the granular material in the storage tank, there is a great difference in the reliability of the measured value depending on which point is measured.

However, ultrasonic waves are invisible,
Since the transmission area has a relatively large width, it is difficult to specify and clarify the measurement points. And in the measuring device using an ultrasonic wave, since there is a possibility that the ultrasonic wave may be reflected on beams and ribs which reinforce the storage tank from the inside, the reliability of the measured value is likely to be lowered.

[0009] The present invention improves the workability in the measurement, specifies the measurement points on the level surface of the granular material,
It is an object of the present invention to provide a level surface measuring method and a level surface measuring device for a granular material which improve the reliability of measured values by clarification.

[0010]

In order to achieve this object, according to the method for measuring the level surface of a granular material according to the present invention, the level surface of the granular material is irradiated with a visible light laser as irradiation light,
A laser distance meter capable of measuring the distance to the level surface based on the time difference between the irradiation light and the reflected light reflected back on the level surface is provided at a predetermined position of the upper end opening of the storage tank. Then, the distance measured by the laser range finder can be displayed by an output means at a remote position.

[0011]

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

As shown in FIGS. 1 and 2, a powder level measuring apparatus 10 according to the present invention is measured by a laser distance meter 12 using a visible light laser as irradiation light and a laser distance meter. Output means 14 capable of outputting a distance at a remote location
And By installing the laser distance meter 12 at a predetermined position above the storage tank 16, the height of the level surface (surface) 18a of the granular material 18 accommodated in the storage tank can be measured, and the laser distance meter can be used. The level surface measuring device 10 is configured so that the measured distance can be recognized by the output means 14 at the remote position.

As can be seen from FIG. 2, a laser distance meter is provided.
12 is, for example, a level surface 18a of the granular material using a visible light laser whose amplitude is modulated by a signal of a constant frequency as irradiation light.
And a light receiving means 22 for receiving the reflected light returned by the reflection on the level surface 18a of the granular material.

The modulation signal of the irradiation light and the modulation signal of the reflected light are compared by a phase difference detecting means 24, and a phase difference signal corresponding to a phase difference between the two is output to a pulse counting means 26. This phase difference signal is generated by a clock pulse having a very fine signal width by a crystal oscillator or the like and a pulse counting means.
26, the number of pulses in the portion corresponding to the phase difference signal is counted, and the distance based on the number of pulses is calculated by the calculating means 28 as the distance to the level surface 18a of the granular material. , The laser distance meter 12 is configured.

The wavelength of the visible light laser oscillated by the visible light laser oscillating means 20 is, for example, 620 to 690 nm.
Can be exemplified. However, the wavelength of the visible light laser is
It is sufficient that the distance can be measured by measuring the time difference due to reflection, and the present invention is not limited to this. A visible light laser having another wavelength, for example, around 530 nm, may be oscillated from the visible light laser oscillating means 20. .

The basic principle of the distance measurement in the laser distance meter 12 and the basic structure of the laser distance meter are the same as those of a known lightwave distance meter or the like that uses light from a light emitting diode as irradiation light. For an outline of the principle, see "New Edition / Latest Survey Equipment Handbook"
Edition: March 31, 1994 --- Japan Surveying Instruments Manufacturers Association)
For the section “2. Principles” (middle section on page 132 to middle section on page 135) in “Chapter 5 Distance Measuring Equipment 5.5.1 Light Rangefinder” and its basic structure, see “5.5.1 Light Wave In the “Rangefinder” section, “3. Optical system” (page 135 middle section to page 137 lower section) and “4. Electrical section” (page 137 lower section to page 139 upper section) are described respectively. Therefore, the description is omitted here.

As shown in FIG. 1, the storage tank 16 is formed in a substantially funnel shape having a height of, for example, 20 to 30 m and a diameter of about 2 to 4 m. From the discharge path 16b. Here, the level surface 18a of the granular material accommodated in such a storage tank 16 is generally not flat, and after being filled, has a substantially mountain shape like a solid line, and after being discharged, a dashed line. In the case of measuring the height of the level surface of the granular material in such a storage tank, there is a large difference in the reliability of the measured value depending on which point is measured because it becomes a substantially mortar type as shown in FIG. Occurs.

Therefore, the laser range finder 12 sets a point where the fluctuation of the height is relatively small in the whole of the granular material level surface 18a, that is, a position which can be exemplified as an average height of the level surface as a specific point. The storage tank 16 is installed and fixed at a predetermined position of the upper end opening 16a so that a visible light laser can be irradiated.
The location (specific point) which can be exemplified as the average height of the level surface 18a of the granular material is specified by a so-called empirical rule of an operator engaged in measuring the level surface of the granular material. Is what is done.

In the present invention, since the laser rangefinder 12 using a visible light laser as the irradiation light is used, the irradiation position of the irradiation light on the level surface 18a of the granular material is clarified. The irradiation point (laser spot) of the visible light laser by this type of laser range finder 12 is, for example, about 6 mm in diameter at a measurement distance of 10 m, so that it is possible to sufficiently select a measurement point at a pinpoint, and the measurement point is small. Specialized and easily visible. Therefore, erroneous shots to the beams and ribs can be reliably prevented.

The distance measured by the laser distance meter 12 is transmitted to the output means 14 via a predetermined transmission path.
As the output means 14, for example, a liquid crystal display or an LED
A display having a display section 14a composed of a display element or the like can be exemplified, and the distance measured by the laser distance meter 12 can be recognized by the numbers and the like displayed on the display. The output unit 14 is arranged, for example, at a position where a measurement distance on the ground can be read.

Here, since the visible light laser has a reflection characteristic with respect to the surface to be irradiated, according to the laser distance meter 12 using the visible light laser as the irradiation light, the surface to be irradiated, that is, the level surface 18a of the granular material is used. It is possible to receive reflected light and measure the distance even under direct irradiation of a visible light laser to the light.
That is, in the laser distance meter 12 using visible light laser as irradiation light, it is not necessary to dispose a reflecting prism or the like on the surface to be irradiated as in a known lightwave distance meter.

As described above, in the method for measuring the level surface of a granular material according to the present invention, since the laser rangefinder 12 irradiating the visible light laser is used, the visible light laser is directly applied to the level surface of the granular material. Irradiation is sufficient. Then, since it is sufficient to recognize the distance measured by the laser range finder 12 under the output of the output means 14 at the remote position, the height of the level surface 18a of the granular material can be measured efficiently.

Further, since the distance measured by the laser range finder 12 can be output by the output means 14 located at a remote position, the laser range finder can be set at a predetermined position of the upper end opening 16a of the storage tank. That is, the worker only needs to recognize the distance on the ground under the output from the output means 14, so that the safety of the worker can be ensured,
Workability is improved.

Further, since the visible light laser is used as the irradiation light in the laser distance meter 12, the level surface 18 of the granular material is used.
The irradiation point for a is clarified. Therefore, it is easy to select a measurement point with respect to the level surface 18a of the granular material, and sufficiently reliable distance measurement is possible.

Further, since the visible light laser has high directivity and high straightness, if the irradiation is performed while avoiding the beams and ribs provided on the inner surface of the storage tank 16, the reflection by the beams and ribs is surely prevented. it can. Therefore, also in this respect, highly reliable distance measurement can be performed.

The level surface of the granular material to be irradiated is
Since there is no need to dispose a reflection prism or the like on 18a, complication of the measurement operation can be reliably prevented.

According to the granular surface level measuring apparatus 10 of the present invention, the above-described level surface measuring method can be appropriately performed, and the workability and workability when measuring the level surface 18a of the granular material can be improved. Certainty is easily improved.

In the embodiment of the present invention,
The visible light laser is amplitude-modulated by a signal of a certain frequency,
The laser distance meter 12 is embodied as a configuration for measuring a distance based on a phase difference between a modulation signal of irradiation light and a modulation signal of reflected light. However, the laser distance meter 12 irradiates a visible light laser onto the level surface 18a of the granular material as irradiation light, and uses an optical method of comparing the irradiation light with the reflected light reflected back to the level surface. Any configuration that can measure the distance to the level surface is sufficient, so it is not limited to the comparison of the phase difference between the irradiation light and the reflected light; for example, the distance can be measured by another optical method using a pulse or the like. A laser range finder having such a configuration may be used in the present invention.

By the way, the output means 14 is provided with the laser distance meter 12.
A series of switch means 30 for issuing a command signal to According to such a configuration, remote control of the laser range finder 12 is possible, and operation control of the laser range finder and recognition of the measurement distance can be performed at one place, thereby improving workability in this respect as well. Is done.

In the embodiment of the present invention, a display having a display section 14a composed of a liquid crystal display, an LED display element or the like is exemplified as the output means 14. It is sufficient that the output is performed in a state recognizable by the operator, and thus the output is not limited to the display. For example, a printer or the like may be used as the output unit. Further, the output unit 14 is not limited to either the display or the printer, and may be configured to include both of them.

Further, the present invention is not limited to a configuration in which the distance measured by the laser range finder 12 is simply output by a display, a printer, or the like. The output means 14 may be used.

As shown in FIG. 3, in such a configuration, the laser distance meter 12 is connected to, for example, a serial transmission device 32 having a serial interface and a wired transmission path 34 wired to a site such as a factory. The distance measured by the laser range finder can be transmitted to the output means (output means) 14 of the computer via the serial receiving device 36 connected via this.

In such a configuration, the laser distance meter
The number of pulses counted by the twelve pulse counting means 26 is converted into a digital signal by the arithmetic means 28 to become distance data, and is transmitted by the serial transmission device 32 via the wired transmission path 34 and the serial reception device 36. The distance data is sent to a control device of a computer or the like. The storage and output of the distance measured by the laser distance meter 12 can be appropriately performed by conversion, calculation, and the like of the distance data in a computer control device and the like.

As described above, if the output means forming a part of the computer is the output means 14 of the laser range finder 12, the storage distance can be stored in the storage tank 16 by appropriately storing and processing the measured distance by the computer. It is easy to manage the height of the level surface 18a of the powder, that is, the capacity of the powder. Therefore, also from this point, workability is improved.

Note that the computer referred to here is a host computer, and this host computer has output means
If each of the 14 terminals can be connected, the measurement distance can be taken out for each terminal. Accordingly, the measurement distance can be recognized at a plurality of places without being limited to one place.

In the configuration shown in FIG. 3, an example is shown in which the laser rangefinder 12 and the output means of the computer are connected via a wired transmission path 34, but the present invention is not limited to this. A configuration in which distance data from the laser range finder can be transmitted to the output means 14 of the computer may be adopted.

As shown in FIG. 4, in such a configuration, the laser range finder 12 is connected to, for example, a radio transmitter 40, and the digital distance signal is transmitted from the radio transmitter to the radio receiver 42. And transmits the distance data from the wireless receiving device to the output means 14 of the computer.
, The management and output of the measurement distance by the laser range finder can be performed by the computer.

Here, as shown in FIG. 4, if distance data can be transmitted wirelessly, wiring of a wired transmission path at a site such as a factory becomes unnecessary. Therefore, no complicated construction is required when introducing the level surface measuring device 10,
The level surface measuring device can be easily and inexpensively introduced.

The output means of the computer serving as the output means 14 is sufficient if it can output and manage the distance measured by the laser range finder 12. Therefore, it is not necessary to provide the output means for each laser range finder. The total may be output and managed by the output means of one computer.

For example, a laser distance meter 12 is installed for each of a plurality of storage tanks installed at a site such as a factory. Then, as shown in FIG. 5, the plurality of laser rangefinders 12 for each storage tank are connected to, for example, selector means 44 for connecting any one of the plurality of input paths to the output path. Like the serial transmission device 3
2. Connected to the output means 14 of the computer via a wired transmission path 34 and a serial receiving device 36.

As described above, the laser distance meter 12 is provided for each of the plurality of storage tanks, and the distance measured by the desired laser distance meter can be output and managed by the output means 14 of the computer via the selector means 44. Since the capacity of the plurality of laser rangefinders 12, that is, the capacity of the storage tank 16, can be collectively managed by one computer, the workability is also improved from this point.

Here, a configuration in which data from the laser rangefinder 12 is transmitted by wire is shown as an example. However, the present invention is not limited to this, and the serial transmission device 32 and the serial reception device 36 shown in FIG. It goes without saying that data can be transmitted wirelessly in the same manner as in FIG. 4 by replacing the device with a wireless receiving device.

Further, in this embodiment, before the data is transmitted from the plurality of laser rangefinders 12, the selector means 44 is used.
Although a configuration in which a desired laser range finder can be selected is illustrated by way of example, the present invention is not limited to this. As a configuration in which the distance data to be output to the output unit 14 is selected by the selector unit after transmission of the data. Is also good.

Further, since the selector means 44 only needs to be able to select any one of the plurality of laser rangefinders 12 as an input path of the distance data, any of hardware and software can be used as the selector means. Good. In addition,
In the configuration in which the distance data input path is selected by the selector means 44 after the transmission of the distance data, the selection of the distance data by software can be used particularly effectively.

By the way, in the vicinity of the storage tank 16 having the granular material 18 as a volume, dust composed of fine particles of the granular material is scattered. Therefore, the laser distance meter 12 is set at the upper end opening 16a of the storage tank. In such a configuration, there is a possibility that dust adheres to a transmission window of the visible light laser of the laser range finder and the like, thereby obstructing transmission of the visible light laser.

Therefore, as shown in FIG. 6, in the present invention, the laser range finder 12 is housed in a closed container 46 to isolate the laser range finder from dust. The closed container 46 is provided with a window 46 in which a light transmitting plate capable of transmitting light is disposed.
a, and the laser range finder 12 is arranged in a closed container so as to be able to irradiate and receive a visible light laser through the window.

The upper end opening 16a of the storage tank is closed by a lid 48, and the laser distance meter 12 is placed at the upper end opening of a tube 50 which is erected and fixed in communication with the insertion hole 48a of the lid.
Are placed and fixed in close contact with each other. An air blowing means 54 such as a compressor is provided at the end of the discharge flow path so that compressed air can flow into the pipe from a discharge flow path 52 provided on the side surface of the intermediate portion of the pipe 50.

The compressed air discharge flow path 52 is
For example, it is arranged near the laser distance meter.

In such a configuration, the laser distance meter
Since the sealed container 46 in which the twelve containers are housed is arranged and fixed in close contact with the upper end opening of the tube 50, there is no escape area for air at the upper end side, that is, at the side of the laser rangefinder. Flow of compressed air in the direction of the laser distance meter is blocked even if compressed air flows into the laser rangefinder. That is, the compressed air from the blowing means 54 descends from the discharge channel 52 through the inside of the tube 50 as shown by the arrow, and flows out into the storage tank 16 through the insertion hole 48a of the lid.

As described above, if compressed air is sent from the blowing means 54 to the storage tank through the inside of the pipe 50, the dust of the particulates can be prevented from entering the pipe from the storage tank 16, so that the window The adhesion of dust to the portion 46a is prevented, and the reliability of the irradiation and reception of the visible light laser by the laser range finder 12 is improved.

In the storage tank 16, usually, a lid
Since manhole holes are provided at 48 and the like, even if the upper end opening of the storage tank is closed with a lid, the flow of air in the storage tank can be secured to some extent. In other words, even if the upper end opening 16a of the storage tank is closed with the lid 48, the flow of air in the storage tank is obtained, so that the particles 18 from the discharge path 16b are not adversely affected by the blockage with the lid. Discharge can be performed smoothly and easily, and the flow of compressed air into the storage tank can be sufficiently ensured.

The lid 48 is inserted into the upper end opening 16a of the storage tank.
A laser distance meter is provided at the top opening of the tube 50 standing on the lid.
As long as it is sufficient to dispose and fix the 12 and allow compressed air to flow into the pipe via the discharge flow channel 52, the distance measurement by the laser distance meter 12 hinders dust, despite the simple configuration. Can be ensured smoothly and easily.

The embodiments of the present invention described above are intended to explain the present invention, and do not limit the present invention in any way, and may be modified or modified within the technical scope of the present invention. It goes without saying that all are included in the present invention.

[0054]

As described above, according to the method for measuring the level of a granular material according to the present invention, it is sufficient to irradiate the visible light laser from the laser distance meter to a specific point on the level surface of the granular material. The distance to the level surface can be measured efficiently.

Then, it is sufficient if the distance measured by the laser range finder is recognized by the output means at the remote position.
Data can be collected smoothly and easily.

Furthermore, in order to use a laser distance meter that uses a visible light laser as irradiation light,
It is possible to specify measurement points on the level surface of the granular material. Therefore, high reliability is obtained for the measurement distance.

According to the apparatus for measuring the level surface of a granular material according to the present invention, the above-described method for measuring the level surface can be appropriately performed, and the workability and the reliability of the operation when measuring the level surface of the granular material can be achieved. Is easily improved.

If the output means of the computer is used as the output means, not only the output of the measured distance but also the management of various data can be easily performed. Therefore, capacity management in the storage tank can be performed smoothly and easily.

If the distance data is transmitted from the laser range finder by wire, the distance data can be reliably transmitted. If the distance data is transmitted from the laser range finder by radio, the wiring work of the transmission path is performed. And the like can be omitted, so that the level surface measuring device can be quickly and inexpensively introduced.

Further, the upper end opening of the storage tank is closed with a lid, and a laser range finder is arranged at the upper end opening of the tube erected on the lid. If compressed air is sent in, the air flows in the tube toward the storage tank, preventing dust from entering the laser range finder. This prevents dust from adhering to the window and prevents the laser range finder , The reliability of the irradiation and reception of the visible light laser is improved.

A lid is provided at the upper end opening of the storage tank, and a laser range finder is arranged and fixed at the upper end opening of the pipe standing upright on the lid, and compressed air can flow into the pipe via the discharge flow path. Therefore, the measurement of the distance by the laser distance meter can be smoothly and easily secured without being hindered by dust, despite the simple configuration.

[Brief description of the drawings]

FIG. 1 is a schematic layout diagram of a granular surface level measuring apparatus according to the present invention, showing a layout state with respect to a storage tank.

FIG. 2 is a schematic block diagram of an apparatus for measuring a level surface of a granular material, centering on the inside of a laser distance meter.

FIG. 3 is an overall schematic block diagram of a granular surface level measuring apparatus according to a modification of the embodiment.

FIG. 4 is an overall schematic block diagram of a granular surface level measuring apparatus according to another modification of the embodiment.

FIG. 5 is an overall schematic block diagram of a granular surface level measuring apparatus according to still another modification of this embodiment.

FIG. 6 is a schematic layout diagram of a granular surface level measuring apparatus according to another embodiment of the present invention.

[Explanation of symbols]

 10 Particle level measuring device 12 Laser rangefinder 14 Output means 16 Storage tank 16a Upper end opening of storage tank 18 Powder 18a Level surface of powder 20 Visible laser oscillation means 22 Light receiving means 24 Phase difference detecting means 26 Pulse counting stage 28 Arithmetic means 44 Selector means 46 Closed vessel 46a Window 48 Lid 48a Insertion hole 50 Tube 52 Discharge channel 54 Blowing means

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Koji Ogura 2-22-10 Higashino, Urayasu-shi, Chiba Pref. Inventor Tadashi Kishimoto 1-31-8 Shinkawa, Chuo-ku, Tokyo Inside Kyosho Engineering Co., Ltd. (72) Inventor Hirohiko Okiyama 2-8-8 Sarugakucho, Chiyoda-ku, Tokyo Inside Rika Corporation (72) Inventor Shozo Koide 4-4-4 Ginza, Chuo-ku, Tokyo Tamaya Measurement System Co., Ltd.

Claims (10)

[Claims] 1. A method for measuring the level of a granular material contained in a storage tank, wherein the height of the level of the granular material is measured as a distance from a predetermined position above the storage tank to the level surface. Is applied to the level surface of the granular material as irradiation light, and a laser distance that enables the distance to the level surface to be measured by an optical method of comparing the irradiation light with the reflected light reflected back to the level surface A level measuring method for a granular material, wherein a meter is installed at a predetermined position of an upper end opening of a storage tank, and a distance measured by the laser distance meter can be output by an output means at a remote position. 2. A method for measuring a level surface of a granular material stored in a storage tank, wherein the height of the level surface of the granular material is measured as a distance from a predetermined position above the storage tank to the level surface. The visible light laser amplitude-modulated by the signal was irradiated from a predetermined position of the upper end opening of the storage tank to a specific point on the level surface of the granular material as irradiation light, and was reflected back to the level surface of the granular material. The reflected light is received, and the modulation signal of the irradiation light and the modulation signal of the reflected light are compared to detect a phase difference therebetween, and a corresponding phase difference signal generated for a time corresponding to the phase difference is detected. By comparing with a predetermined clock pulse, the pulse of the part corresponding to the phase difference is counted, and by calculation from the number of pulses,
Measuring the distance to the level surface of the granular material, and enabling the measured distance to be output by an output means located at a position remote from the irradiation position and the light receiving position of the visible light laser; Measuring method. 3. The number of pulses corresponding to the phase difference between the phase difference signal and a predetermined clock pulse is converted into a digital signal to be distance data, and the distance data can be transmitted to output means forming part of a computer. The method for measuring a level surface of a granular material according to claim 2. 4. A visible light laser oscillating means for irradiating a visible light laser whose amplitude is modulated by a signal of a constant frequency to a specific point on a level surface of a granular material accommodated in a storage tank as irradiation light, A light receiving means for receiving the reflected light returned by the reflection on the level surface of the light, and comparing the modulation signal of the irradiation light with the modulation signal of the reflected light, detecting a phase difference therebetween, and detecting a corresponding phase difference. A phase difference detecting means for generating a signal; comparing the phase difference signal with a predetermined clock pulse;
Pulse counting means for counting the number of pulses in a portion corresponding to the phase difference signal; and calculating means for calculating a distance from the number of pulses counted by the pulse counting means to the level surface of the granular material. A laser level meter is installed at a predetermined position of an upper end opening of a storage tank, and a distance measured by the laser distance meter can be output by an output means arranged at a remote position. 5. The number of pulses counted by the pulse counting means is converted into a digital signal to obtain distance data, and the distance data can be transmitted to an output means forming a part of a computer via a predetermined transmission path. The level surface measuring apparatus for a granular material according to claim 4. 6. A laser range finder is arranged for each of a plurality of storage tanks, and any one of the plurality of laser range finder can be arbitrarily selected by a selector means. The number is converted into a digital signal to obtain distance data, and the distance data from the laser distance meter selected by the selector means can be transmitted to an output means forming a part of a computer via a predetermined transmission path. An apparatus for measuring a level of a granular material according to the above. 7. A laser distance meter is arranged for each of a plurality of storage tanks, and the number of pulses counted by the pulse counting means is converted into a digital signal to be distance data, and the distance data for each laser distance meter is output. And transmitting the distance data transmitted from the plurality of laser rangefinders to the computer having the means. The distance data selected by the selector means can be arbitrarily selected by the selector means. The level measuring apparatus for a granular material according to claim 4, wherein the data can be output by the output means. 8. The level measuring apparatus for a granular material according to claim 5, wherein the distance data from the laser distance meter to the output means of the computer is transmitted by wire. 9. The level measuring apparatus for a granular material according to claim 5, wherein the distance data is transmitted wirelessly from the laser range finder to the output means of the computer. 10. An upper end opening of a storage tank is closed by a lid, and a sealed container containing a laser distance meter is connected to an insertion hole of the lid, and is provided with a pipe at an upper end opening of the vertically fixed pipe body. It is arranged and fixed in close contact with visible light laser irradiation and light reception that has passed through the body, and blows air so that compressed air can flow into the pipe from the discharge channel provided on the side of the middle part of the pipe. Means is disposed at the end of the discharge flow path, and compressed air from the air blowing means is sent from the pipe toward the storage tank, thereby preventing intrusion of dust particles into the pipe, thereby providing a laser distance meter. The level surface measuring device for granular materials according to any one of claims 4 to 9, wherein the dust can be prevented from adhering to the surface.