JPH08184554A - Method and apparatus for measuring moisture of powdery /granular material and moisture measuring cell - Google Patents

Abstract

PURPOSE: To obtain a method for measuring the moisture of powdery/granular material accurately using near infrared rays. CONSTITUTION: A branch pipe 34 is coupled vertically to the outside of a plane 33 for carrying powdery/granular material 31 and a moisture measuring cell 35 having a transparent glass window 48 for transmitting near infrared rays 53 is provided at the branch pipe 34. The detector 54 of an infrared moisture meter 36 is disposed oppositely to the glass window 48, on the outside thereof, while spaced apart therefrom by a predetermined distance and a part of powdery/granular material 31 being carried on the carrying plane 33 is dropped through the branch pipe 34 into the cell 35 thus filling the cell 35. The powdery/ granular material 31 in the cell 35 is irradiated with near infrared rays 53 having predetermined wavelengths from the detector 54 through the glass window 48 and the reflected light is received by the detector 54 thus measuring the moisture of the powdery/granular material 31 in the cell 35 based on the ratio of infrared rays 53 absorbed thereby. Finally, compressed air is fed into the cell 35 and the powdery/granular material 31 in the cell 35 is returned onto the carrying plane 33 through the branch pipe 34.

Description

Detailed Description of the Invention

The present invention relates to a method and an apparatus for measuring the water content of powders and granules using a near infrared ray moisture meter, and a cell for measuring water content. More specifically, the water content of powders and granules can be easily and accurately measured. The present invention relates to a method and an apparatus for doing so, and a cell for measuring moisture.

[0002]

2. Description of the Related Art Conventionally, this type of moisture measuring method has been used in various industries. For example, the device shown in FIG.
It is used to control the water content of powder or granules such as resin or milling.
Pipes 4 and 5 are connected to the upstream and downstream sides via a joint 3. In the lower part of the measurement chamber 2, a conveyor belt conveyor 6 is arranged, and a baffle plate 8 for adjusting the height of the granular material is erected at a constant gap A from the conveyor surface 7 of the conveyor belt 6. At the upper part of the measurement chamber 2, a detector 10 of a near-infrared moisture meter 9 is mounted above the transport surface 7 by a certain height H and on the downstream side of the baffle plate 8. In addition, the detector 10 surrounds the optical path of the near infrared rays 11 and surrounds the air purge hood 12.
Is mounted and the converter 13 is connected.

In the apparatus having the above structure, the powdery granules 1 conveyed from the upstream pipe 4 into the measuring chamber 2 have a predetermined height from the conveying surface 7 of the powdery granules due to the baffle plate 8. Is adjusted so as to be conveyed to the pipe 5 on the downstream side. Then, the cleaning air 14 is blown into the hood 12 to clean and remove dust and the like on the surface of the detector 10, while the detector 10 irradiates the granular material 1 with near-infrared rays 11 having a constant wavelength. Detector 10
Receives the reflected wave, detects the ratio of the near-infrared rays 11 absorbed by the water content of the granular material 1, and sends an electric signal of the detected value to the converter 13. The converter 13 converts the electric signal from the detector 10 into a moisture value of the powder and granules 1 and sends the electric signal of the moisture value to a moisture recorder, a moisture controller, etc. (not shown), and the powder and granules 1 Have them record and adjust the water content.

Further, the apparatus shown in FIG. 9 is used for controlling the water content of powder particles in a resin fluidized bed granulating apparatus. The fluidized bed granulator 15 is a vertical cylindrical container,
An air supply pipe 17 for the fluidized-bed air 16 is connected to the bottom portion, and an exhaust pipe 19 for the fluidized-bed air 16 provided with a blower 18 is connected to the top portion, and a humidification pipe provided with a control valve 20 inside thereof. A spray nozzle 22 of 21 is opened, and a moisture measuring hole 23 is opened below the body portion toward the inside of the fluidized bed granulator. The tip of the optical fiber 27 that extends from the detector 25 of the near infrared moisture meter 24 and transmits the near infrared 26 is seen through the moisture measuring hole 23.
5 to the control valve 2 of the humidifying pipe 21 via the converter 28.
0 is connected.

In the apparatus having the above structure, the fluidized-bed air 16 containing fine resin powder before granulation is blown into the bottom of the fluidized-bed granulator 15 from the air supply pipe 17, and the resin fine powder flows while rising. Form the layers. The granulating water 29 is sprayed from the spray nozzle 22 of the humidifying pipe 21 to the fluidized bed to humidify the fine powder in the fluidized bed to generate the granular material 30. The air 16 for the fluidized bed after granulation is exhausted by the blower 18 to the exhaust pipe 19
Is released into the atmosphere from On the other hand, the detector 25 of the near-infrared moisture meter 24 irradiates the near-infrared ray 26 having a constant wavelength through the moisture measuring hole 23 to the granular material 30 through the optical fiber 27, receives the reflected wave, and receives the moisture content of the granular material 30. The ratio of the near infrared rays 26 absorbed by the sensor is detected, and an electric signal of the detected value is sent to the converter 28. The converter 28 converts the electric signal from the detector 25 into a moisture value of the powder 30 and sends a control signal corresponding to the moisture value to the control valve 20 of the humidifying pipe 21 to supply the amount 29 of moisture for grain supply. Is adjusted to maintain the water content of the powder and granules 30 at an appropriate value.

Further, in Japanese Patent Laid-Open No. 61-138528, fluidization of powders and granules is performed to form a fluidized bed, and the water content of the powders and granules in the fluidized bed is measured by an infrared absorption moisture meter using quartz glass. A method of doing so is disclosed.

[0007]

However, in the water content measuring method using the apparatus shown in FIG. 8, the baffle plate 8 causes unevenness on the powder surface irradiated with the near-infrared rays 11 and the flatness cannot be maintained. The distance D between the container 10 and the powder surface is non-uniform. If the joint 3 has a poor sealing property, dust and water in the atmosphere enter the measuring chamber 2 through the joint 3 and adversely affect the measured powder surface. For these reasons, there is a problem that the measured water content varies and the measurement accuracy decreases.

In the moisture measuring method using the apparatus shown in FIG. 9, since the granular material 30 forms a fluidized bed, the distance from the tip of the optical fiber 27 to the granular material 30 is not uniform. In addition, the near infrared ray 26 is the optical fiber 2
There is a problem of attenuation in 7. For these reasons, there is a problem that the measured water content varies and the measurement accuracy is low. Further, each of the above methods has a problem that the device and operation are complicated and the cost is high.

Further, in the method described in JP-A-61-138528, since the powdery particles are in a fluid state,
As in the case of the device of FIG. 9, there is a problem that the distance between the moisture meter and the powder and granules becomes non-uniform, and as a result, the moisture measurement values vary, and highly accurate measurement cannot be performed. It is an object of the present invention to improve the conventional water content measuring method as described above and eliminate such a problem.

[0010]

In order to achieve the above object, the method for measuring the moisture content of a granular material according to the first aspect of the present invention is to connect a branch pipe vertically to the outside of a transportation surface for transporting the granular material. A moisture measuring cell provided with a transparent glass window capable of transmitting near-infrared rays in the branch pipe, and a near-infrared moisture meter of the near-infrared moisture meter so as to face the glass window outside the glass window by a certain distance. A detector is provided, and a part of the powder or granules conveyed on the conveying surface is dropped into the cell through the branch pipe so as to be filled, and the powder or granules in the cell is separated from the detector to the glass window. Irradiate a near-infrared ray of a certain wavelength through the, receives the reflected wave in the detector, the moisture content of the granular material in the cell from the ratio of the near-infrared radiation absorbed in the moisture content of the granular material in the cell After that, compressed air was supplied into the cell, and the powder or granular material in the cell was passed through the branch pipe. A method for returning onto the conveying surface. Then, it is preferable that the dropping and filling of the powdery particles into the cell, the measurement of the water content of the powdery particles, and the return of the powdery particles onto the conveying surface are performed periodically.

The powdery water content measuring device of the second invention is a device for carrying out the above method, wherein a branch pipe is vertically connected to the outside of a carrying surface for carrying the powdery material. The branch pipe is provided with a moisture measuring cell having a transparent glass window capable of transmitting near-infrared rays, and a plurality of compressed air nozzles are arranged in the cell for preventing the return and inflow of powder and granular material. An apparatus in which a detector of a near-infrared moisture meter is provided outside the glass window so as to face the glass window with a certain distance therebetween.

Further, a third aspect of the present invention is a cell used in the above method and apparatus, wherein a moisture measuring glass window is provided in a central portion of a cell body having a hollow portion inside,
A branch pipe connecting portion is provided on one side or both sides, a glass window cleaning air hole is provided on the opposite surface of the moisture measurement glass window, and a powder or granular material returning air hole is provided on one side or both sides of the glass window cleaning air hole. The moisture measuring cell is characterized in that an L-shaped compressed air nozzle is provided in the powder / granule returning air hole toward the branch pipe connecting portion.

In order to implement a method of periodically dropping and filling the powdery or granular material into the cell, measuring the water content of the powdery or granular material, and returning the powdery or granular material onto the conveying surface. Has
A solenoid valve may be connected to each of the plurality of compressed air nozzles arranged in the cell, and a computer may be provided to automatically control the excitation and demagnetization of the solenoids of these solenoid valves.

[0014]

In the moisture measuring method having the above-mentioned structure, a part of the powdery particles on the conveying surface is dropped into the cell through the branch pipe to fill the cell, so that the powdery particle in the cell remains stationary in the glass window. Touching,
It keeps its thickness constant. Therefore, the distance from the detector to the measured powder surface is always kept uniform. Further, since the inside of the cell is sealed by the powder particles, there is no possibility that external dust, water and the like will reach the measurement powder surface and adversely affect the water measurement. Therefore, the state of the measured powder surface is always kept constant. Therefore, the measured water content does not vary and the measurement accuracy is high.

It should be noted that dropping and filling of the granular material into the cell,
If the moisture measurement of the powder and granules and the return of the powder and granules to the transport surface can be performed periodically, the moisture measurement and humidity control of the powder and granules can be automated easily.

[0016]

EXAMPLES Examples of the present invention will be described below with reference to FIGS. 1 to 7, but it goes without saying that the present invention is not limited to these examples.

Example 1 This example relates to a method for measuring the water content of a powder or granular material put into a hopper. An apparatus for carrying out this method is shown in FIG.
Shown in As shown in FIG. 1, this apparatus connects both ends of a branch pipe 34 in the vertical direction to the outside of a slanted transport surface 33 of a hopper 32 into which the granular material 31 is charged, and measures the water content in the middle of the branch pipe 34. The cell 35 is provided, and a near infrared moisture meter 36, a solenoid valve device 37, and a computer 38 are further arranged.

The cell 35, as shown in FIGS. 2 and 3,
A front cover 42 and a back cover 43 are fixedly provided on both front and back surfaces of a cell body 40 having a hollow portion 39 inside with packings 41, and branch pipe connecting portions on both end faces have branch pipes 34 through O-rings 44. It is connected to the. An air hole 45 for cleaning a glass window and air holes 46 for returning powders and granules are provided on both sides of the tube seat portion of the front cover 42, and the air hole 46 has an L-shaped nozzle for compressed air. 47 is connected outward. A circular glass window 48 for moisture measurement is provided in the center of the back cover 43. In the glass window 48, a transparent glass 49 capable of transmitting near infrared rays, for example, sapphire glass is packed 50 and O. It is fitted through the ring 51,
It is fixed by a presser 52. Sapphire glass has a low near-infrared transmission attenuation rate of about 2%, and has a high hardness, so that it has an advantage of being less likely to be scratched.

The near-infrared moisture meter 36 irradiates the granular material 31 in the cell 35 with the near-infrared ray 53, and a detector 54 for detecting the ratio of the near-infrared ray 53 absorbed by the moisture of the granular material 31. ,
It is composed of a converter 55 for converting the detection value of the detector 54 into the moisture value of the powder or granular material 31. The detector 54 is a glass window 4
8 are arranged outside the glass window 48 so as to face each other with a certain distance therebetween, and the optical axis of the near-infrared ray 53 is relative to the axis of the glass window 48 in view of the reflectance of the radiated near-infrared ray 53. And is inclined (angle α = about 15 degrees).

The solenoid valve device 37 comprises five solenoid valves 56, 5
7, 58, 59, 60, and clean compressed air 63, which is supplied from an instrumentation air source in the factory through valves 61, 62, is inserted into the lower part of the branch pipe 34 for returning the powdery or granular material. A nozzle 64 for compressed air, an air hole 45 for cleaning a glass window and an air hole 46 for returning powder and granules provided in the cell 35, and an air purging nozzle 6 provided between the glass window 48 and the detector 54.
It is piped so that it can be distributed to The compressed air 63 is supplied to the inside of the detector 54 via the valve 66 and is also used for cleaning the inside thereof.

The computer 38 is provided with an input section 67, an output section 68 and a communication board section 69, through which a converter 55, each solenoid of the solenoid valve device 37 and a host device such as a moisture recorder and a moisture controller. Connected to 70.

As shown in the timing chart of the solenoid valve solenoid in FIG. 4, moisture measurement by the moisture measuring device having the above-described structure is performed periodically and automatically under the control of the computer 38, with 60 seconds as one cycle. One cycle consists of seven steps, and the operation in one cycle will be described below in the order of steps. In addition, in FIG. 4, the shaded portion indicates the excited state of the solenoid valve solenoid, and the blank portion indicates the demagnetized state of the solenoid valve solenoid.

In step I, the solenoid of the solenoid valve 56 is excited. The compressed air 63 is supplied from the electromagnetic valve 56 to the lower portion of the branch pipe 34 via the compressed air nozzle 64, and returns the powder particles 31 retained therein to the transport surface 33.

In step II, the solenoids of the solenoid valves 56 and 58 are excited. The compressed air 63 is supplied from the electromagnetic valve 56 to the lower portion of the branch pipe 34 via the nozzle 64, and from the electromagnetic valve 58 to the lower portion of the cell 35 via the nozzle 47 provided in the air hole 46 on the lower side of the cell 35. Of the measured powder and granules 3 which are supplied downward to the cell and remain in the lower part of the cell 35.
1 is returned to the transport surface 33 via the lower portion of the branch pipe 34.

In the third step, the solenoid of the solenoid valve 56 is demagnetized, but the compressed air 63 is continuously supplied from the solenoid valve 58 and remains in the lower portion of the cell 35.
Continue to return 1.

In step IV, the solenoid of the solenoid valve 58 is demagnetized and the solenoids of the solenoid valves 57 and 59 are excited. The compressed air 63 flows from the solenoid valve 57 to the cell 35.
Is supplied to the central portion of the cell 35 through the air hole 45 of the cell 35, and is also supplied upward from the solenoid valve 59 to the upper portion of the cell 35 through the nozzle 47 provided in the air hole 46 on the upper side of the cell 35. While returning the measured powder and granules 31 staying in the central part and the upper part of the branch pipe 34 and the powder and granules 31 staying in the upper part of the branch pipe 34 to the conveying surface 33 via the upper part of the branch pipe 34. , The inner surface of the glass window 48 is cleaned.

In step V, the solenoid valves 56, 57, 59,
Sixty solenoids are energized. Compressed air 63 is IV
The granular material 31 dropped from the cell 35 to the lower portion of the branch pipe 34 in the step is returned to the transport surface 33 in the same manner as in the first step, and is retained in the upper portion of the cell 35 and the branch tube 34 in the fourth step. The returning of the powder particles 31 and the cleaning of the inner surface of the glass window 48 are continued, and the outer surface of the glass window 48 is cleaned by being supplied to the nozzle 65 from the electromagnetic valve 60.

In step VI, the solenoids of the solenoid valves 56 and 60 are demagnetized. The compressed air 63 is supplied from the electromagnetic valve 57 to the central portion of the cell 35 in the same manner as in the VI step, and is also supplied upward from the electromagnetic valve 59 to the upper portion of the cell 35, while continuously cleaning the inner surface of the glass window 48. , Transport surface 3
3 to prevent the powder particles 31 from falling into the cell 35.

In step VII, all solenoid valves 56, 5 are
The solenoids 7, 58, 59, 60 are demagnetized, and the supply of compressed air 63 from the solenoid valve is cut off. Therefore, a part of the new powder particles 31 on the transport surface 33 falls into the cell 35 via the upper portion of the branch pipe 34 and is filled therein. Subsequently, the detector 54 has a certain wavelength (for example, 1.
Near infrared rays 53 (94 μm, 3.0 μm, etc.)
The near-infrared rays 53 which are radiated to the granular material 31 in the cell 35 through 8 and are reflected by the reflected wave to be absorbed by the moisture of the granular material 31.
Is detected and an electric signal of the detected value is sent to the converter 55. The converter 55 converts the electric signal from the detector 54 into the moisture value of the powder 31 and sends the electric signal of the moisture value to the input unit 67 of the computer 38. This water content measurement is performed three times at one second intervals in one cycle (see line a in FIG. 4).
The computer 38 sends the average moisture value of the three measured values from the communication board section 69 to a higher-level device 70 such as a moisture recorder or a moisture controller to record and adjust the moisture. When one cycle is completed in this way, the next cycle is started.

FIG. 5 shows the results of measuring the water content of the powder and granules continuously measured for 800 minutes as described above. In this figure, in part b, the powder and granules are electrostatically attached due to overdrying, and in part c, the powder and granules are agglomerated because they are not dried. In either case, it is a factor that causes troubles in the production line of powder and granules, so it is understood that the humidity control of the powder and granules is necessary in advance.

Example 2 In this example, when there is no place to pipe the lower part of the branch pipe 34 in the first embodiment, all the measured powder and granules 31 in the cell 35 are placed above the branch pipe 34. To transport surface 33
In case of returning to above. As shown in FIG. 6, the apparatus in this case has the branch pipe 3 outside the transport surface 33 of the hopper 32.
4, the upper end of 4 is connected in the vertical direction, the cell 35 is connected to the lower end of the branch pipe 34, and the near-infrared moisture meter 3 is used as in the first embodiment.
6, an electromagnetic valve device 37 and a computer 38 are arranged.

In the cell 35, the lower nozzle 47 of the two nozzles 47 provided in the cell 35 of the first embodiment is omitted, and instead, a blind lid 71 provided on the lower end surface is provided for compressed air. The nozzle 72 is connected upward.

The solenoid valve device 37 comprises four solenoid valves 56, 57, 58 and 59. The solenoid valve 56 is a nozzle 72, the solenoid valve 57 is an air hole 45, and the solenoid valve 58 is a nozzle 47. Further, the solenoid valves 59 are connected to the nozzles 65, respectively.

The other structure of the apparatus is the same as that of the apparatus of the first embodiment. As shown in the timing chart of the solenoid valve solenoid in FIG. 7, moisture measurement by the device having the above-described configuration is performed periodically and automatically under the control of the computer 38 with 60 seconds as one cycle. One cycle consists of six steps, and the operation in one cycle will be described below in the order of steps. In addition, in FIG. 7, the shaded portion shows the excited state of the solenoid valve solenoid, and the blank portion shows the demagnetized state of the solenoid valve solenoid.

In step I, the solenoid of the solenoid valve 56 is excited. The compressed air 63 is supplied from the solenoid valve 56 to the lower portion of the cell 35 through the compressed air nozzle 72, and pushes up the measured powdery or granular material 31 accumulated therein into the branch pipe 34.

In step II, the solenoids of the solenoid valves 56, 57 and 58 are excited. The compressed air 63 is supplied to the solenoid valve 56.
Is supplied to the lower part of the cell 35 through the nozzle 72 from the solenoid valve 57 and continues to be pushed up in the first step, and is supplied to the central part of the cell 35 through the air hole 45 of the cell 35. Clean the inner surface of the glass window 48, and further, the cell 35 from the solenoid valve 58 through the nozzle 47.
Of the measured powder or granular material 31 that is supplied upward to the upper part of the cell 35 and remains in the upper part of the cell 35 and the branch pipe 34.
It returns to the conveyance surface 33 via 4.

In step III, the solenoid of the solenoid valve 56 is demagnetized. The compressed air 63 is supplied from the electromagnetic valve 57 to the central portion of the cell 35 in the same manner as in the second step, and is also supplied upward from the electromagnetic valve 58 to the upper portion of the cell 35 to continue cleaning the inner surface of the glass window 48. While carrying surface 3
3 to prevent the powder particles 31 from falling from the branch pipe 34 into the cell 35.

In step IV, the solenoids of the solenoid valves 57, 58 and 59 are excited. The compressed air 63 is used for cleaning the inner surface of the glass window 48 and the cells 3 of the powder and granules 31 in the third step.
5 is continuously prevented from falling into the interior of the glass window 5, and is further supplied from the electromagnetic valve 59 to the nozzle 65 to clean the outer surface of the glass window 48.

In step V, the solenoids of the solenoid valves 57 and 59 are demagnetized. The compressed air 63 continues to prevent the powder or granular material 31 from falling into the cell 35 in the IV step.

In step VI, all solenoid valves 56, 5
The solenoids 7, 58, 59 are demagnetized, the supply of compressed air 63 from the solenoid valve is cut off, and the powder particles 31 are newly dropped and filled in the cell 35. The operation thereafter is exactly the same as the operation in the step VII of the first embodiment.

[0041]

As described above, according to the present invention, since the powder particles on the conveying surface are dropped from the branch pipe into the cell and filled, the powder particles in the cell are in a stationary state and contact the glass window, Be sure to keep its thickness constant. Therefore, the distance from the detector to the measured powder surface is always uniform.

Further, since the particles are filled in the cell, there is no possibility that foreign matter such as dust or water will reach the measured particle surface. Therefore, the state of the measured powder surface is always kept constant. As a result, the measured water content does not vary and the measurement accuracy is high.

Further, dropping and filling of the granular material into the cell,
The productivity of a granular material production line is significantly improved by enabling the computer to periodically and automatically measure the moisture content of the granular material and return the measured granular material to the transportation surface. Can be made.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram showing a moisture measuring apparatus according to a first embodiment of the present invention.

FIG. 2 is a bottom view of the moisture measuring cell used in Example 1 of the present invention.

3 is a cross-sectional view taken along line XX of FIG.

FIG. 4 is a timing chart of the solenoid valve solenoid according to the first embodiment of the present invention.

FIG. 5 is a graph showing the moisture content of powder and granules obtained by the moisture measurement method of the present invention.

FIG. 6 is an overall configuration diagram showing a moisture measuring apparatus according to a second embodiment of the present invention.

FIG. 7 is a timing chart of the solenoid valve solenoid according to the second embodiment of the present invention.

FIG. 8 is a main part configuration diagram of an apparatus for performing a conventional water content measuring method.

FIG. 9 is a main part configuration diagram of an apparatus for performing another conventional moisture measuring method.

[Explanation of symbols]

31 powder and granules 33 transport surface 34 branch pipe 35 moisture measuring cell 36 near infrared moisture meter 38 computer 47 nozzle for compressed air 48 glass window 53 near infrared 54 detector 56, 58, 59, 60 solenoid valve 63 compressed air 64 Nozzle for compressed air 72 Nozzle for compressed air

Claims (5)

[Claims] 1. A moisture measuring cell having a transparent glass window through which a near infrared ray can be transmitted, the branch pipe being vertically connected to the outside of a conveying surface for conveying the powder or granular material, A detector of a near-infrared moisture meter is provided outside the glass window so as to face each other with a certain distance from the glass window, and a part of the granular material conveyed on the conveying surface is passed through the branch pipe. Drop in the cell, let it be filled, irradiate the near-infrared rays of a certain wavelength through the glass window from the detector to the granular material in this cell, receive the reflected wave to the detector, in the cell The moisture content of the powder in the cell is measured from the ratio of the near-infrared rays absorbed in the moisture content of the powder, and then compressed air is supplied into the cell, and the powder in the cell is A method for measuring water content of a powder or granular material, which comprises returning the powder onto the transport surface via a branch pipe. 2. The granular material according to claim 1, wherein dropping and filling of the granular material into the cell, measurement of water content of the granular material, and returning of the granular material to the conveying surface are periodically performed. Method for measuring water content. 3. A moisture measuring cell provided with a transparent glass window through which near-infrared rays can be transmitted by connecting a branch pipe in a vertical direction to the outside of a conveying surface for conveying the powder and granules, A plurality of compressed air nozzles are arranged in the cell to prevent the powder particles from being returned and flowed in, and a near infrared moisture meter is provided outside the glass window so as to face each other with a certain distance from the glass window. A moisture measuring device for powdery or granular material, comprising a detector. 4. The computer according to claim 3, wherein a solenoid valve is connected to each of the plurality of compressed air nozzles arranged in the cell, and a computer for automatically controlling excitation and demagnetization of solenoids of these solenoid valves is provided. Water content measuring device for powder and granules. 5. A moisture measuring glass window is provided in the center of a cell body having a hollow portion inside, and a branch pipe connecting portion is provided on one side or both sides, and the glass window is provided on the opposite surface of the moisture measuring glass window. The air holes for cleaning and the air holes for cleaning the glass window are provided with air holes for returning the granular material on one side or both sides, and an L-shaped compressed air nozzle is provided in the branch pipe connecting portion in the air hole for returning the granular materials. A moisture measurement cell, which is provided for the cell.