Moisture meter

Abstract

A technique is provided for reducing the influence of convection on a sample tray in a heat-dry type moisture meter equipped with a sample tray cover between a heating light source and a sample. [Solution] The moisture meter comprises a moisture meter main body 2 having a housing 20 that houses a mass detection unit that detects load inside, a pan holder 25 that is attached to the mass detection unit on the top surface of the housing 20, a sample pan 26 that is detachably attached to the top surface of the pan holder 25, a short cylindrical windbreak wall 29b that is provided around the sample pan, and a cover part 4 that is provided on the top of the housing so as to be able to be opened and closed, has a top surface 41 and peripheral walls 42, houses a heating light source inside, covers the sample pan 26 when closed, and defines a heating chamber, and the windbreak wall 29b has a surface thermal reflectivity of less than 50%.

Description

[Technical Field]

[0001] The present invention relates to a moisture meter, and more particularly to a heat-drying type moisture meter. [Background technology]

[0002] Heat-drying moisture meters are known as a type of device for measuring the moisture content of samples. For example, the heat-drying moisture meter disclosed in Patent Document 1 has a mass detector disposed inside a box-shaped housing, a pan holder attached to the upper end of the connecting shaft of the mass detector, a sample pan placed on the pan holder, and a windshield surrounding the sample pan. An openable cover member is disposed on the top of the housing, surrounding the sample pan from above. A heating light source is disposed inside the cover member. A sample pan cover is disposed between the heating light source and the sample pan. Components constituting the measuring unit, such as the sample pan, windshield, and pan holder, are generally made of glossy stainless steel for durability, chemical resistance, and aesthetic appeal. Glossy stainless steel generally has a high thermal reflectance of 60% or more. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-303571 [Patent Document 2] Japanese Patent Application Publication No. 9-257680 Summary of the Invention [Problem to be solved by the invention]

[0004] Heat-drying moisture meters have a problem in that air convection acting on the sample dish when the sample is heated reduces the accuracy of mass detection and reduces the accuracy of moisture percentage measurement. Patent Document 2 discloses that in a moisture meter using an infrared lamp, the upper end of a skirt that surrounds the lower part of the lamp projects into the outer cylinder that surrounds the lamp, leaving a gap between the skirt and the inner wall of the outer cylinder, thereby minimizing the effect of convection on the sample dish.

[0005] For this reason, similar to Patent Document 1, there has been a demand for reducing the influence of convection on the sample tray in moisture meters that include a sample tray cover that covers the sample tray.

[0006] After extensive research, the inventors discovered that in a moisture meter similar to that described in Patent Document 1, the effects of convection on the sample dish can be reduced by lowering the thermal reflectivity of the components that make up the measuring section.

[0007] The present invention was made in consideration of these circumstances, and aims to provide a technology for reducing the effect of convection on a sample dish in a heating and drying type moisture meter that has a sample dish cover between the heating light source and the sample dish. [Means for solving the problem]

[0008] In order to achieve the above object, a moisture meter according to one aspect of the present invention has the following configuration. 1. A moisture meter body having a housing that houses a mass detection unit that detects loads inside, a pan holder that is attached to the mass detection unit on the top surface of the housing, a sample pan that is detachably attached to the top surface of the pan holder, a short cylindrical windbreak wall that is arranged around the sample pan, and a cover part that is arranged above the housing and can be opened and closed, has a top surface and peripheral walls, houses a heating light source inside, covers the sample pan when closed, and defines a heating chamber, and the windbreak wall has a surface thermal reflectivity of less than 50%.

[0009] 2. In the first aspect, it is also preferable that the distance between the outer edge of the sample dish and the windbreak wall is set taking into account the speed of convection flowing upward along the outer edge of the sample dish, which is caused by air flowing between the outer edge of the sample dish and the windbreak wall.

[0010] 3. In the above aspects 1 and 2, it is also preferable that the distance between the outer edge of the sample tray and the windbreak wall is 9 mm or less.

[0011] 4. In aspects 1 to 3 above, the pan holder has a cylindrical portion connected to the mass detection unit and three branch portions extending horizontally and circumferentially at equal intervals around the central axis of the cylindrical portion, an annular portion with an outer shape that follows the inner circumference of the windshield wall, a handle extending outward from the annular portion, and a protrusion protruding from the annular portion toward the center, and further includes a pan support used to attach and detach the sample pan to the pan holder, the annular portion having a narrow portion cut out on the inner circumference that is narrower than the standard width, and a wide portion having the standard width, the narrow portion being positioned at a position corresponding to the branch portions when the sample pan is attached, the protrusion being formed contiguous with the wide portion, and the handle being provided on the wide portion.

[0012] 5. In the fourth aspect, it is also preferable that the protrusion is provided between the wide portion and the narrow portion, and that a notch is formed at the base end of the protrusion so that the wide portion side has the same width as the narrow portion side. [Effects of the Invention]

[0013] According to the above aspect, it is possible to provide a heat drying type moisture meter in which the influence of convection on the sample tray is reduced. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is an external perspective view of a moisture meter according to a first embodiment with a cover open. [Figure 2] FIG. 2 is an external perspective view of the moisture meter with the cover closed. [Figure 3] FIG. 2 is a schematic exploded perspective view illustrating the internal structure of a cover of the moisture meter. [Figure 4] FIG. 2 is an exploded perspective view illustrating the structure of a measuring section of the moisture meter. [Figure 5] Graph (A) is a graph showing a comparison of weight changes between windshields with and without surface treatment, and graph (B) is a graph showing a comparison of temperature changes between windshields with and without surface treatment. [Figure 6]1A and 1B are diagrams illustrating the effect of convection caused by surface treatment. [Figure 7] FIG. 10 is a diagram showing the results of a thermal fluid analysis during heating using a windshield with a surface treatment according to an embodiment. [Figure 8] FIG. 10 is a diagram showing the results of a thermal fluid analysis during heating using a surface-treated windshield according to a comparative example. [Figure 9] 10(A) and 10(B) are plan views of a measuring section of a moisture meter according to a second embodiment. [Figure 10] FIG. 10 is a diagram showing a comparison of weight changes during heating depending on the size of the gap between the windshield and the sample dish. [Figure 11] 10A and 10B are diagrams showing the results of a thermal fluid analysis of the moisture meter according to the embodiment of the present invention when heated. [Figure 12] 10A and 10B are diagrams showing the results of a thermal fluid analysis of the moisture meter according to the embodiment of the present invention when heated. [Figure 13] FIG. 10 is a diagram showing the results of a thermal fluid analysis performed when a moisture meter according to a comparative example is heated. DETAILED DESCRIPTION OF THE INVENTION

[0015] Preferred embodiments of the present invention will be described below with reference to the drawings, but the present invention is not limited to these.

[0016] (Embodiment) 1 and 2 are perspective views of a moisture meter 100 according to an embodiment. FIG. 1 shows the cover unit 4 in an open state, and FIG. 2 shows the cover unit 4 in a closed state. FIG. 3 is an exploded perspective view showing the internal structure of the cover unit 4. FIG. 4 is an exploded perspective view of the measuring unit 30 of the moisture meter 100. The moisture meter 100 comprises a moisture meter main body 2 and the cover unit 4.

[0017] The moisture meter main body 2 includes a substantially rectangular parallelepiped housing 20. A display / operation unit 21 configured as a touch panel display and operation buttons 22 are arranged in the front of the housing 20. An opening (not shown) is provided in approximately the center of the top surface 23 of the moisture meter main body 2, and a connecting shaft 27 is arranged through the opening (not shown) to connect to a mass sensor of a mass detection unit (not shown) housed inside the housing 20. The mass detection unit may be, for example, an electromagnetic balance type, a strain gauge type (load cell type), or a capacitance type electronic sensor. A pan holder 25 is attached to the upper end of the connecting shaft 27.

[0018] Pan holder 25 has a cylindrical portion 25a (FIG. 4) connected to the tip of connecting shaft 27, and three branches 25b extending horizontally from the upper end of cylindrical portion 25a at equal intervals around the central axis of cylindrical portion 25a. As indicated by arrow A, sample pan 26 is detachably attached to pan holder 25 using pan support 28 (described below). Sample pan 26 is circular, with a flat center and a slightly raised periphery. A windbreak 29 in the shape of a short cylinder with a bottom is provided to surround sample pan 26. Pan holder 25, sample pan 26, pan support 28, and windbreak 29 constitute measurement section 30 of moisture meter 100.

[0019] Although not shown, housing 20 houses an arithmetic processing unit that processes the detection results from the mass detection unit, a heat source driving unit that drives a heat source (described later), a display driving unit that drives display operation unit 21 based on the processing results, etc. Moisture meter 100 is configured to measure the mass and moisture percentage of a sample placed on a sample tray and display the results on display operation unit 21 through the operation of these units in response to the operation of display operation unit 21 and operation buttons 22.

[0020] Cover section 4 has a top surface 41 and a peripheral surface 42, and is shaped like a container that opens toward moisture meter main body 2. Cover section 4 is configured as a rectangular parallelepiped overall, with both corners of the front end rounded. Cover section 4 is connected to moisture meter main body 2 via a pivot 43 provided at the rear of moisture meter main body 2, allowing it to be opened and closed freely around pivot 43 as indicated by arrow B. In the closed state shown in Figure 2, cover section 4 is formed to cover the entire measuring section 30, thereby defining a heating chamber.

[0021] The cover 4 includes a heating unit 50 on the inside. An exhaust port 41a is formed on the top surface 41. When the cover 4 is closed, a gap 47 with a predetermined distance d1 is formed between the top surface 23 of the moisture meter body 2 and the lower end surface of the cover 4. This gap 47 and the exhaust port 41a form an air flow path, allowing various volatile components generated by heating the sample in the heating unit 50 to be quickly discharged to the outside.

[0022] Furthermore, windows 45 are formed in the lower parts of the front surface 42a and side surfaces 42b of the peripheral surface 42 of the cover part 4. The windows 45 are made of a plate material such as tempered glass or heat-resistant, translucent resin, and when closed, allow the state of the sample placed on the sample tray 26 to be observed. Handles 44 for opening and closing the cover part 4 are provided on both sides of the front end of the peripheral surface of the cover part 4 so as to protrude outward.

[0023] Here, the cover unit 4 will be described in detail with reference to Figures 1 and 3. As described above, the cover unit 4 has a rectangular parallelepiped shape with a rounded front end, but for ease of drawing, it is shown as a rectangular parallelepiped shape in Figure 3. Furthermore, for ease of explanation, directions such as up and down will be described based on the closed state unless otherwise specified. In Figure 3, the downward direction is the direction toward the measuring unit 30. The cover unit 4 is configured to cover the heating unit 50 with a heater cover 46 that forms the top surface 41 and the peripheral surface 42.

[0024] The heating unit 50 includes, from the top surface 41 side of the heater cover 46, a reflector 52 housed inside the heater cover 46, a tubular halogen lamp 54 serving as a heating light source attached to the reflector 52, and a sample dish cover 56. The heating light source is not limited to the halogen lamp 54, but may also be an infrared lamp, a ceramic heater, or the like.

[0025] The reflector 52 has a generally rectangular top plate 52a facing the measuring unit 30 and a peripheral wall 52b extending from the periphery of the top plate 52a toward the measuring unit 30. The reflector 52 is shaped like a container with a rectangular opening toward the measuring unit 30. The lower ends of the front and rear peripheral walls 52b1 are each formed with a flange 52c extending in the front-to-rear direction. The left and right peripheral walls 52b2 each protrude outward near the center in the front-to-rear direction. A halogen lamp 54 is attached to the inside of this protrusion 52d. A reflective surface is formed on the inner surface of the reflector 52, for example, by metal deposition or by attaching aluminum foil, to efficiently reflect the light from the halogen lamp 54 and uniformly irradiate the sample.

[0026] Sample dish cover 56 has an overall container shape with a rectangular opening facing measuring unit 30, and includes a roughly rectangular frame 57 disposed opposite measuring unit 30, and poles 58 disposed at the four corners of frame 57 and extending downward. Frame 57 has a rectangular opening 57a formed in its center, and a transparent plate 61 disposed in opening 57a.

[0027] The frame 57 is made of, for example, an aluminum plate, and the transparent plate 61 is made of, for example, tempered glass or a heat-resistant, translucent resin. A protective plate 63 is attached to the surface of the transparent plate 61 facing the measuring unit 30 to prevent samples and the like from colliding with and damaging the transparent plate 61. The protective plate 63 has narrow bars 63a formed across the opening of the frame 57, which extend to intersect with the halogen lamps 54.

[0028] Pole 58 is configured to come into contact with upper surface 23 of moisture meter main body 2 when cover part 4 is tilted toward moisture meter main body 2 to close it, so that pole 58 functions as a stopper.

[0029] Furthermore, rectangular transparent plates 62 made of tempered glass or heat-resistant resin are placed between adjacent poles 58, forming the peripheral walls of sample dish cover 56. This allows the user to visually observe the sample through window 45 formed in heater cover 46.

[0030] The transparent plate 62 has a height shorter than that of the pole 58 so as to leave a gap above and below it when the cover 4 is closed. It is also positioned a predetermined distance away from the frame 57. This allows the moisture meter 100 to create an airflow inside the sample dish cover 56, which flows through the gap below the heater cover 46, passes through the gap below the transparent plate 62, and then passes through the gap above the transparent plate 62 and is exhausted through the exhaust port 41a of the heater cover 46. This creates an airflow inside the sample dish cover 56, allowing various components evaporated from the sample to be quickly exhausted. The halogen lamp 54, reflector 52, sample dish cover 56, opening 57a, and sample dish 26 are all positioned so that their central axes are aligned, allowing for efficient sample heating.

[0031] Next, the configuration of the measuring unit 30 will be described in detail. As shown in Figure 4, the pan support 28 includes an annular portion 28a and a handle 28b extending horizontally outward from the annular portion 28a by a predetermined distance. The annular portion 28a is annular in shape and is larger than the pan holder 25 and the sample pan 26 in plan view, but is slightly smaller than the inner diameter of the windshield 29.

[0032] The free end of handle 28b is bent upward, and handle cover 28c is attached to it. In the closed state shown in Fig. 2, handle cover 28c is positioned outside the space defined by cover part 4. This prevents handle cover 28c from heating up when heated.

[0033] Three protrusions 28d, rectangular in plan view, are formed on the annular portion 28a and extend horizontally a predetermined distance toward the center of the annular portion 28a. For example, the three protrusions 28d are arranged at equal intervals around the circumference. Each protrusion 28d bends downward at its base end by a length corresponding to the rising edge of the outer edge of the sample dish 26, and then extends horizontally inward. When attaching or detaching the sample dish 26 to or from the dish holder 25, the handle 28b is lifted, and the protrusions 28d support the bottom surface of the sample dish, while the inner edge of the annular portion 28a engages with the outer edge of the sample dish, allowing the sample dish 26 to be lifted in a stable manner.

[0034] The windshield 29 has a short cylindrical shape with a bottom, including a bottom surface 29a and a peripheral wall (hereinafter referred to as the windshield wall) 29b extending upward substantially perpendicular to the bottom surface 29a. The windshield wall 29b extends above the upper end of the sample dish 26 when the sample dish 26 is placed on the dish holder 25. Two notches 29c are formed in the upper end of the windshield wall 29b. The notches 29c are used to position the dish support 28. The windshield 29 does not necessarily have to have the bottom surface 29a, and may instead have a short cylindrical shape composed only of the windshield wall 29b.

[0035] Two triangular marks are provided on one of the three branches 25b of pan holder 25. Pan holder 25 is attached to the moisture meter body with the mark aligned with positioning hole 29d provided on bottom surface 29a of windshield 29, so that cylindrical portion 25a can be inserted into connecting shaft 27 with the correct orientation.

[0036] The pan holder 25, pan support 28, and windshield 29 that make up the measuring unit 30 are made of stainless steel. The sample pan 26 is made of, but not limited to, aluminum, for example. The windshield 29 has been treated to reduce its surface thermal reflectance. Examples of treatment methods include barrel polishing, sandblasting, and black chrome plating. Barrel polishing reduces the surface thermal reflectance to 50% or less, sandblasting reduces it to 40% or less, and black chrome plating reduces it to 3% or less. The thermal reflectance range is preferably 50% or less, more preferably 40% or less, and particularly advantageously 3% or less.

[0037] (experiment) Fig. 5(A) shows the difference in the change in the weighing value depending on whether or not the windshield was surface-treated. In Example 1, moisture meter 100 was used in which the surface of windshield 29 was black chrome-plated (thermal reflectivity 3%), and in Example 2, moisture meter 100 was used in which the surface of windshield 29 was barrel-polished (thermal reflectivity 50%). In Comparative Example 1, moisture meter 900 (see Fig. 6(B)) had the same mechanical configuration as moisture meter 100, but the windshield 929 was made of stainless steel with a glossy surface (thermal reflectivity 70%). The changes in the weighing value were compared when the moisture meters of Examples 1 and 2 and Comparative Example 1 were heated at 160°C for 8 minutes without placing a sample thereon. As can be seen from Figure 5(A), in Comparative Example 1, the weighing value became significantly negative within one minute after the start of heating, whereas in Examples 1 and 2, the change in the weighing value that occurred within one minute after the start of heating was smaller, and it was found that by applying a surface treatment to the windshield 29 that reduces the thermal reflectivity, the change in the weighing value in the negative direction was reduced.

[0038] Next, to investigate the factors that reduce the change in the measured value, we compared the difference in windshield surface temperature between those with and without a surface treatment to reduce thermal reflectivity. Figure 5(B) is a graph showing the measured change in windshield temperature over time depending on whether the windshield was surface-treated. Here, Example 3 used a moisture meter 100 according to the above-described embodiment, in which the surface of the windshield 29 was sandblasted (thermal reflectivity: 40%). Comparative Example 1, on the other hand, was the same as that shown in Figure 5(A). As can be seen from Figure 5(B), when the surface treatment to reduce thermal reflectivity was applied, the temperature rise was faster and the steady-state temperature was higher compared to that without the surface treatment. This suggests that the presence or absence of the surface treatment is a factor in the difference in the influence of convection.

[0039] Based on the above assumption, the effect of reducing the influence of convection by surface treatment will be described with reference to Fig. 6. Fig. 6(A) is a longitudinal cross-sectional view along the front-rear direction near the measuring unit 30 and the cover unit 4 of the moisture meter 100 according to Example 1. This figure also applies to Examples 2 and 3. Fig. 6(B) is a longitudinal cross-sectional view corresponding to Fig. 6(A) of a moisture meter 900 according to Comparative Example 1.

[0040] In Comparative Example 1, the temperature of windshield 929 is relatively low. Therefore, when heating begins with moisture meter 900, high-temperature air heated by halogen lamp 54 accumulates above sample dish 26, as shown in FIG. 6(B). Air flowing in from the lower end of transparent plate 62 rises along windshield wall 929b from the gap between windshield 29 and transparent plate 62, and at its upper end flows into the gap between windshield wall 929b and sample dish 26. The high-temperature air above the sample dish also expands and flows into the gap between windshield wall 929b and sample dish 26. As a result, convection currents are generated in the gap between sample dish 26 and windshield wall 929b, particularly along the outer edge of sample dish 26, pushing upward from the bottom.

[0041] As a result, the measured value becomes smaller than the actual value. In Example 1, as shown in FIG. 6(A), in addition to the high-temperature air accumulating above sample dish 26, the air in the gap between windbreak wall 29b and the outer edge of sample dish 26 is also heated by the temperature rise of windbreak 29, becoming high-temperature air. Therefore, air flowing in from the outside and the high-temperature air above the sample dish are repelled by the high-temperature air between windbreak wall 29b and sample dish 26. In other words, air is less likely to flow into the gap between sample dish 26 and windbreak wall 29b. Therefore, convection currents that push up from the bottom along the outer edge of sample dish 26 are less likely to occur, suppressing fluctuations in the measured value.

[0042] (thermal fluid analysis) This is also verified by thermal fluid analysis. Fig. 7 shows the results of thermal fluid analysis of moisture meter 100 according to Example 1 at a preset heating temperature of 200°C from the start of heating until the steady state begins, and Fig. 8 shows the results of thermal fluid analysis of moisture meter 900 according to Comparative Example 1 at a preset heating temperature of 200°C from the start of heating until the steady state begins.

[0043] From Figures 7 and 8, it can be seen that the upward convection on the outer edge side of the sample pan in the gap between the windshield wall 29b, 929b and the sample pan 26, 26 is significantly reduced to approximately 25 mm / s in Example 1, compared to approximately 50 mm / s in Comparative Example 1, making it possible to reduce the accompanying change in the measurement value.

[0044] Thus, according to this embodiment, by making the components of the weighing section 30, particularly the surface of the windshield 29, low reflectivity, it is possible to reduce the effects of convection and improve the accuracy of moisture content measurement.

[0045] In addition to windshield 29, it is also advantageous to reduce the thermal reflectivity of the surfaces of pan holder 25, sample pan 26, and pan support 28. This is because the temperature rises rapidly throughout measuring section 30 after heating begins, and the steady-state temperature also increases. This makes it possible to maintain a high temperature near windshield wall 29b, improving the convection suppression effect. Note that pan support 28 is not essential for this embodiment of the moisture meter 100. This is because sample pan 26 can be placed on and removed from pan holder 25 using tools such as tweezers, for example.

[0046] (Second embodiment) Meanwhile, through further investigations, the inventors have found that it is preferable to make the gap between sample dish 26 and windbreak wall 29b as small as possible in order to reduce the effects of upward convection that occurs in the gap between sample dish 26 and windbreak wall 29b. Therefore, moisture meter 200 according to the second embodiment is configured such that dish support 28 in moisture meter 100 has been modified to have a structure suitable for making the gap between sample dish 26 and windbreak wall 29b as small as possible.

[0047] 9(A) and 9(B) are plan views of measuring unit 230 of moisture meter 200 according to the second embodiment, with (A) showing the state without sample pan 226 and (B) showing the state with sample pan 226 placed thereon. Measuring unit 230 has roughly the same configuration as measuring unit 30 of moisture meter 100, but differs in the dimensions of sample pan 226 and the shape of pan support 228. Specifically, measuring unit 230 includes windshield 29, pan receptacle 225, pan support 228, and sample pan 226. The shape of sample pan 226 is the same as sample pan 26, but differs in its dimensions in that the distance d2 between the inner wall of windshield wall 29b and the outer edge of sample pan 226, i.e., the gap between the outer edge of sample pan 226 and windshield wall 29b, is configured to be 9 mm or less. It is preferable to set this gap as small as possible, because as will be described below, a gap of 9 mm or less reduces the speed of convection and therefore reduces the effect on the measurement value. Note that the diameter l2 of sample pan 226 is set according to the model and purpose of the moisture meter, but in the illustrated example, the diameter l2 of sample pan 226 is 95 mm, and the diameter l1 of the inner periphery of windbreak wall 29b is 112 mm.

[0048] As shown in FIG. 9B, the sample dish 226 may not be a perfect circle but may have a bulging portion 226a that bulges outward. In this case, the diameter l2 of the sample dish 226 refers to the diameter of a circle that does not include the bulging portion 226a. Similarly to the sample dish 26, the sample dish 226 has a slightly raised periphery that expands slightly outward. Therefore, the diameter of the sample dish 226 is slightly different between the bottom and the outer edge. Unless otherwise specified, the diameter l2 of the sample dish 226 in this specification refers to the diameter of the outer edge of the sample dish 226. For convenience, the sample dish 226 is designated by a display size; a sample dish 226 with a diameter l2 of 95 mm has a display size of φ90 mm.

[0049] The radial dimension of the branch portion 225b of the pan holder 225 corresponds to the dimension of the sample pan 226. Similar to the pan support 28, the pan support 228 includes a ring-shaped portion 228a and a handle 228b extending horizontally outward from the ring-shaped portion 228a by a predetermined distance. The ring-shaped portion 228a is also formed with three protrusions 228d that are rectangular in plan view and extend horizontally by a predetermined distance toward the center of the ring-shaped portion 228a.

[0050] The annular portion 228a is annular, but the length between its outer and inner circumferences (the width of the annulus) is not constant. Specifically, it has a wide portion 228f having the standard width of the annular portion 228a and a narrow portion 228e whose width is reduced by cutting out the inner periphery. The narrow portions 228e are formed in three locations, equidistantly spaced around the circumference and of the same dimensions, at positions corresponding to the positions of the branch portions 225b of the dish holder 225 when the dish support 228 is placed inside the windshield 29. As a result, the tips of the branch portions 225b do not interfere with the dish support 228.

[0051] Each narrow portion 228e extends circumferentially from the base end of the protruding portion 228d to the middle between the protruding portions 228d adjacent to it. As a result, the wide portion 228f is located on one circumferential side (the left side in the illustrated example) of each protruding portion 228d, and the narrow portion 228e is located on the other circumferential side (the right side in the illustrated example). That is, the dish support 228 has the narrow portion 228e formed in the portion facing the branch portion 225b of the dish holder 225, and the protruding portion 228d to which the load is applied is configured to be continuous with the wide portion 228f. However, at the base end of the protruding portion 228d, a notch is formed on the wide portion 228f side so that the width is the same as that of the narrow portion 228e. In addition, the handle 28b is provided on the wide portion 228f.

[0052] (Effect of the dish support structure) With the above configuration, the pan support 228 can support a larger sample pan 226 while maintaining strength, even if it has the same outer diameter as the pan support 28. In conventional configurations, the width of the annular portion 228a is narrowed when attempting to support a larger sample pan 226 with the same outer diameter. As a result, the gap between the windshield wall 29b and the outer edge of the sample pan 226 can be reduced. Furthermore, the protruding portion 228d, which receives the load, is positioned adjacent to the wide portion 228f, ensuring the necessary strength. Furthermore, the base end of the protruding portion 228d on the wide portion 228f side is notched to have the same width as the narrow portion 228e. This prevents uneven stress on the left and right sides of the base end of the protruding portion 228d, contributing to improved strength.

[0053] (Effect of gap size) (experiment) FIG. 10 is a graph showing the difference in the change in weight when the size of the gap between the sample pan and the inner periphery of the windshield is changed. In Example 4, a moisture meter with the same configuration as moisture meter 200 was used. The sample pan had a diameter l2 of 95 mm (display size φ90 mm) and was not surface-treated. The inner diameter of windshield 29 was 112 mm. The gap in Example 4 was measured as 8.5 mm. In Comparative Example 2, a moisture meter 950 with the same mechanical configuration as moisture meter 200 was used. The sample pan 926 had a diameter l2 of 87 mm (display size φ85 mm). The windshield 29 had the same inner diameter of 112 mm as in Example 4. The gap in Comparative Example 2 was measured as 12.5 mm. In the experiment, moisture meters 200 and 950 were heated at 160°C for 10 minutes without a sample, stopped heating for 2 minutes, and then heated for a further 38 minutes, and the change in weight was measured. The heating was stopped for 2 minutes during the experiment to check the effect of heating drift.

[0054] 10, it can be seen that in Example 4, where the gap was narrowed, the negative change in the weighing value due to the influence of convection was clearly reduced. Furthermore, in terms of the thermal drift after heating was stopped, Example 4 reduced the thermal drift to 0.01 mg compared to 1.7 mg in Comparative Example 1. The inventors conducted similar experiments multiple times and found that the influence of convection was clearly reduced if the gap size was designed to be at least 9 mm or smaller.

[0055] (thermal fluid analysis) Figures 11, 12, and 13 show the results of thermal fluid analysis performed on moisture meters using a windshield 29 with the same size as in Example 4 (i.e., an inner diameter of 112 mm) and sample pans 226 of different sizes, at a set heating temperature of 200°C, from the start of heating to a steady state. Figure 11 shows the results for Example 5, where a sample pan 226 with a diameter l2 of 95 mm (display size φ90 mm) was used. Figure 12 shows the results for Example 6, where a sample pan 226 with a diameter l2 of 104 mm (display size φ100 mm) was used. Figure 13 shows the results for Comparative Example 2, the same as in the above experiment, where a sample pan 26 with a diameter l2 of 87 mm (display size φ85 mm) was used. The gaps between the sample pan 26 and windshield wall 29b are 8.5 mm, 4 mm, and 12.5 mm, respectively.

[0056] In Figure 13, the speed of the upward convection flow along the outer edge of the sample dish is 60 mm / s, while in Figure 11 it is 25 mm / s, clearly reducing the effects of convection. Furthermore, in Figure 12, it is 20 mm / s, demonstrating further reduction. Thus, it can be seen that the narrower the gap between the inner periphery of windshield wall 29b and the outer edge of sample dish 226, the more the effects of convection are reduced. Furthermore, by further performing similar thermal fluid analysis, it was found that a gap of 9 mm or less between the inner periphery of windshield wall 29b and the outer edge of sample dish 226 is effective in reducing the effects of convection.

[0057] As with moisture meter 100, it is not essential that moisture meter 200 include pan support 228, and the effects of convection can be reduced by narrowing the gap between sample pan 226 and windbreak wall 29b as described above. However, providing pan support 228 having the above configuration is advantageous because it can reduce the effects of convection without compromising convenience during measurement.

[0058] The effect of reducing the influence of convection by reducing the gap between the inner periphery of windshield wall 29b and the outer edge of sample dish 226 can be achieved without reducing the reflectance of windshield 29 by surface treatment. However, by simultaneously reducing the reflectance of windshield 29 and reducing the gap, the effect of reducing the influence of convection can be further enhanced.

[0059] The above describes preferred embodiments of the present invention, but the above embodiments are merely examples of the present invention, and these can be combined based on the knowledge of those skilled in the art, and such forms are also included in the scope of the present invention. [Explanation of symbols]

[0060] 2: Moisture meter body 4: Cover part 20: Housing 23:Top surface 25: Plate holder 25a: Cylindrical part 25b: Branch 26: Sample dish 28:Plate support 28a: Annular section 28b: Toride 28d:Protrusion 29: Windshield 29b: Windbreak wall 29c: Notch 41: Top 52d:Protrusion 100: Moisture meter 200: Moisture meter 225: Plate holder 225b: Branch 226: Sample dish 228:Plate support 228a: Annular section 228b: Toride 228d:Protrusion 228e: Narrow part 228f: Wide section

Claims

1. a moisture meter body having a housing that houses a mass detection unit that detects a load; a pan holder attached to the mass detection unit on the upper surface of the housing; a sample tray detachably attached to the top surface of the tray holder; a short cylindrical windbreak wall provided around the sample dish; a cover portion that is provided above the housing in an openable and closable manner, has a top surface and a peripheral wall, houses a heating light source therein, and covers the sample dish when closed to define a heating chamber; A moisture meter characterized in that the distance between the outer edge of the sample tray and the windbreak wall is 9 mm or less.

2. A moisture meter as described in Claim 1, characterized in that the windbreak has a surface thermal reflectivity of 50% or less.

3. the dish holder has a cylindrical portion connected to the mass detection portion, and three branch portions extending horizontally and equidistantly around a circumferential direction with the central axis of the cylindrical portion as a center, a dish support tool having an annular portion having an outer shape that follows the inner periphery of the windbreak wall, a handle extending outward from the annular portion, and a protrusion protruding from the annular portion toward the center, the dish support tool being used to attach and detach the sample dish to and from the dish holder; the annular portion includes a wide portion having a reference width and a narrow portion having a width narrower than that of the wide portion by being cut out on an inner circumferential side, the narrow portion is disposed at a position corresponding to the branch portion when the sample dish is attached; the protrusion is formed continuously with the wide portion, The handle is provided on the wide portion.

3. The moisture meter according to claim 1 or 2.

4. The protruding portion is provided between the wide portion and the narrow portion, 4. The moisture meter according to claim 3, wherein a notch is formed at the base end of the protrusion so that the wide portion has the same width as the narrow portion.

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