JP2012177590A - Dust meter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dust meter capable of preventing the reproducibility of equivalent film correction from deteriorating by a change in the position of a filter paper because a correction tool is not brought into contact with the filter paper when the correction tool is arranged between upper and lower blocks of a measurement cell manually during equivalent film correction.SOLUTION: In a dust meter including a measurement cell 100 having an upper block 102 and a lower block 104 being openable and closable with a gas passage 106 and a β-ray irradiation path formed inside to suck and collect dust in a gas phase caused to flow in the gas passage on a filter paper 108 held by the upper and lower blocks, a recessed part 118 whose depth is larger than the thickness of the filter paper is formed in an area including a portion where the filter paper on the top surface of the lower block of the measurement cell 100 is arranged so that the filter paper comes into contact with the bottom surface of the recessed part 118.

Description

  The present invention relates to a dust meter that measures the concentration of dust (microparticulate matter, suspended particulate matter, etc.) contained in a gas phase, and more particularly, to a dust meter that calibrates sensitivity using an equivalent film. .

  As a dust meter for measuring the dust concentration in the gas phase, the dust in the gas phase is sucked and collected on the filter paper, and the transmitted β-ray intensity of the filter paper before and after dust collection is measured. A dust meter based on a β-ray absorption method for obtaining the dust concentration therein is used (see, for example, Patent Document 1). The β-ray absorption method is a measurement method that utilizes the fact that when a substance is irradiated with low-energy β-rays, the amount of β-ray absorption increases in proportion to the mass of the substance.

  Conventionally, the dust meter shown in FIG. 4 is known as a dust meter based on the β-ray absorption method. 4, 2 is a component mounting plate, 4 is a measurement cell, 6 is an upper block of the measurement cell 4, 8 is a lower block of the measurement cell 4, 10 is a gas flow path provided in the measurement cell 4, 12 is a β-ray irradiation path provided in the measurement cell 4, 14 is a sampling pipe, 16 is a suction pipe, 18 is a pump, 20 is a discharge unit, 22 is a β-ray source container, 24 is a β-ray source, and 26 is β Line detector, 28 is a β-ray permeable thin film, 30 is a feeding reel, 32 is a tape filter paper, 34 is a take-up reel, 36 is a pinch roller, 38 is a capstan, 40 is an arithmetic control unit, 42 is a display unit Show.

The procedure for measuring, for example, the dust concentration in the atmosphere using the dust meter of FIG. 4 is as follows.
(1) The inflow end of the sampling pipe 14 is disposed at the air sampling location. On the other hand, the intensity of the β-ray emitted from the β-ray source 24 and passing through the filter paper 32 and reaching the β-ray detector 26 is measured, and this measured value I ₀ is stored in the arithmetic control unit 40.
(2) The pump 18 is operated for a predetermined time to suck a predetermined amount of air, and then the pump 18 is stopped. As a result, dust in the atmosphere is filtered out, and a dust deposit layer 44 is formed on the upper surface of the filter paper 32. In this state, the β ray intensity from the β ray source 24 that passes through the filter paper 32 and the dust deposition layer 44 and reaches the β ray detector 26 is measured. The resulting measured value I is sent to the arithmetic control unit 40, dust concentration is calculated using the measured values I ₀ stored in advance and the measured value I, is displayed on the display unit 42. The calculation of the dust concentration C is performed by the following formula.
C = [A / (μQt)] · ln (I ₀ / I)
C: Dust concentration (g / cm ² )
A: Collection area (cm ² )
μ: Mass absorption coefficient (cm ² / g)
Q: Gas phase passage flow rate (cm ³ / min)
t: Collection time (min)
I: β-ray intensity transmitted through filter paper and dust I ₀ : β-ray intensity transmitted through filter paper only (3) Then, blocks 6 and 8 are opened up and down and pinch roller 36 is driven to move filter paper 32 forward by a predetermined distance. Move to. As a result, the deposited layer 44 moves out of the gas flow path 10, and a new filter paper portion on which no dust is deposited is supplied into the gas flow path 10. In this state, the gap between the blocks 6 and 8 is closed. Return to the initial state. Thereafter, the same operation is repeated and the dust concentration is continuously measured, but all these operations are performed under the control of the arithmetic control unit 40.

  Conventionally, calibration of the sensitivity of the dust meter by the β-ray absorption method shown in FIG. 4 has been performed using an equivalent membrane. The equivalent membrane is a synthetic resin membrane that has a specific mass per unit area and is used as a basis for the mass per unit area. The transmission β-ray intensity when only β-rays are irradiated to the filter paper and the filter paper Equivalent membranes are placed on the surface, and the transmitted β-ray intensity is measured when β-rays are irradiated to these, and span calibration is performed based on these values.

  Specifically, the calibration using the equivalent film is performed as shown in FIG. In FIG. 5, reference numeral 46 denotes a calibration tool. In this calibration tool 46, an equivalent film 52 is fixed to the lower surface of a metal support plate 50 having a through hole 48 so as to cover the through hole 48. When the calibration of the dust meter shown in FIG. 4 is performed using the calibration tool 46, first, only the filter paper 32 is sandwiched between the upper and lower blocks 6 and 8 of the measurement cell 4, and the transmitted β-ray intensity is measured. Next, after opening the upper and lower blocks 6 and 8, the calibration tool 46 is manually arranged between the upper and lower blocks 6 and 8. Thereafter, the upper and lower blocks 6 and 8 are closed, and the filter paper 32 and the equivalent membrane 52 are sandwiched by the upper and lower blocks 6 and 8 with the equivalent membrane 52 in close contact with the filter paper 32, and the transmitted β-ray intensity is measured. .

  Since the calibration tool 46 is manually attached to the measurement cell 4, the knob portion 54 and the two positioning recesses 56 and 58 are formed in the support plate 50, and these recesses 56 and 58 are formed. Is engaged with a guide bolt 60 (only one is shown) provided between the upper and lower blocks 6 and 8 of the measurement cell 4 to position the calibration tool 46 between the upper and lower blocks 6 and 8.

Japanese Patent No. 3330270

However, the conventional calibration means using the calibration tool shown in FIG. 5 has the following problems (A) and (B).
(A) When the calibration tool is manually arranged between the upper and lower blocks, the support plate or the equivalent membrane of the calibration tool may come into contact with the filter paper, and the position of the filter paper may change. Since the density and mass of the filter paper vary depending on the location, if the position of the filter paper changes as described above, the measured value is affected, and the reproducibility of the equivalent membrane calibration deteriorates.
(B) The above-mentioned measurement cell normally opens and closes the upper and lower blocks by moving the lower block up and down. However, if the upper and lower blocks are opened wide to make it easier to place the calibration tool between the upper and lower blocks, the measurement cell moves up and down. The position of the filter paper may change depending on the movement of the lower block. When the position of the filter paper changes in this way, the reproducibility of the equivalent membrane calibration deteriorates as in (A).

  The present invention has been made in view of the above-described circumstances, and when the calibration tool is manually placed between the upper and lower blocks of the measurement cell during equivalent membrane calibration, the support plate of the calibration tool and the equivalent membrane come into contact with the filter paper. Therefore, an object of the present invention is to provide a dust meter capable of preventing the position of the filter paper from changing and the reproducibility of the equivalent membrane calibration from being deteriorated.

In order to achieve the above object, the present invention
While having an openable and closable upper and lower block, a gas flow path and a β-ray irradiation path are formed inside, and sucking and collecting the dust in the gas phase flowing through the gas flow path on a filter paper sandwiched between the upper and lower blocks, and By irradiating the filter paper with β-rays through the β-ray irradiation path, equipped with a measurement cell that measures the transmitted β-ray intensity of the filter paper before and after dust collection,
After measuring the transmission β-ray intensity of only the filter paper before dust collection, with the upper and lower blocks open, a calibration tool that covers the through holes on the support plate having the through holes and attaches an equivalent membrane is placed between the upper and lower blocks. A dust meter that manually inserts and then calibrates the equivalent membrane by closing the upper and lower blocks and measuring the transmitted β-ray intensity transmitted through the filter paper and the equivalent membrane,
A dust meter is provided in which a recess having a depth larger than the thickness of the filter paper is formed in a region including a portion where the filter paper is disposed on the upper surface of the lower block, and the filter paper is in contact with the bottom surface of the recess. To do.

  Since the measurement cell of the dust meter according to the present invention has a recess having a depth larger than the thickness of the filter paper in a region including a portion where the filter paper is arranged on the upper surface of the lower block, the filter paper is in contact with the bottom surface of the recess. When the calibration tool is manually arranged between the upper and lower blocks, the support plate and equivalent membrane of the calibration tool are in contact with the uppermost surface of the lower block, but are not in contact with the filter paper. Therefore, in the dust meter of the present invention, the position of the filter paper does not change when the calibration tool is disposed between the upper and lower blocks, and the position of the filter paper is prevented from changing and the reproducibility of the equivalent membrane calibration is deteriorated. be able to.

  Moreover, since the calibration tool does not contact the filter paper as described above, the calibration tool can be inserted between the upper and lower blocks by sliding the upper surface of the lower block, and the calibration tool can be easily arranged between the upper and lower blocks. Therefore, it is not necessary to open the upper and lower blocks greatly. Therefore, in the dust meter of the present invention, the position of the filter paper does not change due to the movement of the lower block that moves up and down, and also in this respect, the position of the filter paper changes and the reproducibility of the equivalent membrane calibration is prevented from being deteriorated. be able to.

  In the present invention, it is preferable that the front upper end portion of the inlet portion into which the calibration tool for the lower block is inserted protrude forward from the front lower end portion of the same portion of the upper block. In this way, when the calibration tool is manually placed between the upper and lower blocks, the end of the calibration tool is brought into contact with the upper surface of the front upper end of the entrance portion of the lower block, and the calibration tool is slid on the upper surface of the lower block. It is possible to insert the calibration tool between the upper and lower blocks.

  In the present invention, a convex portion is formed around the gas flow path on the lower surface of the upper block, and the convex portion presses the filter paper against the lower block when measuring the transmitted β-ray intensity transmitted only through the filter paper. At the same time, it is preferable that the convex portion presses the equivalent membrane against the filter paper and the lower block when measuring the transmitted β-ray intensity transmitted through the filter paper and the equivalent membrane. In this way, the transmission β-ray intensity of only the filter paper can be measured in a state where the filter paper and the lower block are in close contact, and the transmission β-ray intensity of the filter paper and the equivalent membrane in a state where the equivalent membrane, the filter paper and the lower block are in close contact with each other. Can be measured, and the reproducibility of the equivalent membrane calibration can be improved.

  In the dust meter of the present invention, when the calibration tool is manually arranged between the upper and lower blocks of the measurement cell at the time of equivalent membrane calibration, the support plate of the calibration tool and the equivalent membrane do not come into contact with the filter paper. It is possible to prevent the reproducibility of the equivalent membrane calibration from deteriorating due to the change of the.

It is a typical partial omission sectional view showing an example of the measurement cell of the dust meter concerning the present invention. It is a schematic plan view which shows the lower block of the same measurement cell. It is a typical side view which shows the measurement cell. It is a schematic partially omitted cross-sectional view showing an example of a conventional dust meter. It is a schematic perspective view which shows the state which performs equivalent film | membrane calibration of the dust meter.

  1 is a schematic partially omitted sectional view showing an example of a measurement cell of a dust meter according to the present invention, and FIG. 2 is a schematic plan view showing a lower block of the measurement cell. In this measurement cell 100, 102 indicates an upper block, 104 indicates a lower block, and 106 indicates a gas flow path. In FIG. 1, 108 is a tape-shaped filter paper, 110 is a calibration tool, 112 is a metal support plate of the calibration tool 110, 114 is a through hole of the metal support plate 112, and 116 is an equivalent membrane of the calibration tool 110.

  In the measurement cell 100 of this example, the depth is larger than the thickness of the filter paper 108 (usually 0.1 mm or less) in the region including the portion (passing portion) where the tape-like filter paper 108 is disposed on the upper surface of the lower block 104. A large recess is formed. More specifically, a band-shaped first concave portion 118 is formed in a region including a portion where the filter paper 108 is disposed on the upper surface of the lower block 104, and further, the depth of the first concave portion 118 around the gas flow path 106. The second concave portion 120 having a deep square shape is formed. The width of the first recess 118 is larger than the width of the filter paper 108. The depth of the bottom surface of the first recess 118 with respect to the uppermost surface 122 of the lower block is 0.3 mm, and the depth of the bottom surface of the second recess 120 with respect to the bottom surface of the first recess 118 is 0.2 mm. In the present invention, there is no limitation on the shape and structure of the recess, and the shape and structure are formed in a region including the portion where the filter paper is arranged on the upper surface of the lower block, and can prevent the calibration tool from contacting the filter paper. That's fine. For example, in this example, the concave portion is a two-stage type including the first concave portion 118 and the second concave portion 120, but may be a single-stage type including only the first concave portion 118.

  Further, as shown in FIG. 3, in the measurement cell 100 of this example, the front upper end portion 126 of the entrance portion for inserting the calibration tool 110 of the lower block 104 is forward of the front lower end portion 128 of the same portion of the upper block 102. Protruding. In this example, the entire front side of the entrance portion of the lower block 104 is protruded forward from the entire front side of the same portion of the upper block 102, but at least the front upper end portion of the entrance portion of the lower block 104 is What is necessary is just to protrude ahead rather than the front side lower end part of the same part of the upper block 102.

  Further, as shown in FIG. 1, the measurement cell 100 of this example has a convex shape having a bottom shape smaller than the planar shape of the second concave portion 120 of the lower block 104 around the gas flow path 106 on the lower surface of the upper block 102. When the portion 124 is formed and the transmitted β-ray intensity transmitted only through the filter paper 108 is measured, the projection 124 presses the filter paper 108 against the lower block 104 and transmits through the filter paper 108 and the equivalent membrane 116. When the β-ray intensity is measured, the convex portion 124 presses the equivalent membrane 116 against the filter paper 108 and the lower block 104.

  The dust meter of this example has the same configuration as the dust meter of FIG. 4 except for the point related to the measurement cell 100 described above. Further, the procedure for performing the equivalent film calibration of the dust meter of this example is as described with reference to FIG. In this case, the dust meter of this example has the following advantages in the equivalent membrane calibration.

  (1) When calibrating the dust meter of this example, first, only the filter paper 108 is sandwiched between the upper and lower blocks 102 and 104 of the measurement cell 100 and the transmitted β-ray intensity is measured, and then the lower block 104 is lowered. After the upper and lower blocks 102 and 104 are opened, the calibration tool 100 is manually placed between the upper and lower blocks 102 and 104. In this case, in the dust meter of this example, the first recess 118 having a depth larger than the thickness of the filter paper is formed in the region including the portion where the filter paper 108 is disposed on the upper surface of the lower block 104. While the calibration tool 110 is manually placed between the upper and lower blocks 102 and 104, the support plate 112 and the equivalent film 116 of the calibration tool 110 are in contact with the uppermost surface 122 of the lower block 104 while contacting the bottom surface of the recess 118. However, it does not contact the filter paper 108. Therefore, in the dust meter of this example, the position of the filter paper 108 does not change when the calibration tool 110 is placed between the upper and lower blocks 102 and 104, and the position of the filter paper 108 changes and the reproducibility of the equivalent membrane calibration is improved. It can be prevented from becoming worse. Further, since the calibration tool 110 does not contact the filter paper 108 as described above, the calibration tool 100 can be inserted between the upper and lower blocks 102, 104 by sliding the upper surface of the lower block 104, It is not necessary to open the upper and lower blocks 102 and 104 to make it easier to place the calibration tool 110 between 104. For this reason, in the dust meter of this example, the position of the filter paper 108 does not change due to the movement of the lower block 104 that moves up and down, and the position of the filter paper 108 also changes at this point and the reproducibility of the equivalent membrane calibration deteriorates. Can be prevented.

  (2) Further, in the dust meter of this example, the front upper end 126 of the entrance portion for inserting the calibration tool 110 of the lower block 104 projects forward from the front lower end 128 of the same portion of the upper block 102. When the calibration tool 110 is manually arranged between the upper and lower blocks 102 and 104, the end of the calibration tool 100 is applied to the upper surface of the front upper end 126 of the inlet portion of the lower block 104, and the calibration tool 110 is placed on the lower block. The upper surface of 104 can be slid and inserted between the upper and lower blocks 102 and 104, and the calibration tool can be easily inserted between the upper and lower blocks 102 and 104.

  (3) Further, in the dust meter of the present example, after the calibration tool 110 is arranged between the upper and lower blocks 102 and 104 as shown in (1), the lower block 104 is raised to close the upper and lower blocks 102 and 104, and the filter paper 108. And the transmitted β-ray intensity transmitted through the equivalent film 116 is measured. In this case, in the dust meter of this example, a convex portion 124 having a bottom surface shape smaller than the planar shape of the second concave portion 120 of the lower block 104 is formed around the gas flow path 106 on the lower surface of the upper block 102, and filter paper When measuring the transmitted β-ray intensity transmitted through only 108, the convex portion 124 presses the filter paper 108 against the lower block 104 and measures the transmitted β-ray intensity transmitted through the filter paper 108 and the equivalent membrane 116. In addition, since the convex portion 124 presses the equivalent membrane 116 against the filter paper 108 and the lower block 104, the transmitted β-ray intensity of only the filter paper 108 is measured in a state where the filter paper 108 and the lower block are in close contact with each other. In addition, the transmission β-ray intensity of the filter paper 108 and the equivalent membrane 116 can be measured in a state where the equivalent membrane 116, the filter paper 108 and the lower block are in close contact with each other. Can be, it is possible to improve the reproducibility of the equivalent layer calibration.

100 Measurement cell 102 Upper block 104 Lower block 106 Gas flow path 108 Tape-shaped filter paper 110 Calibration tool 112 Metal support plate 114 Through hole 116 Equivalent film 118 First recess 120 Second recess 124 Projection

Claims (3)

While having an openable and closable upper and lower block, a gas flow path and a β-ray irradiation path are formed inside, and sucking and collecting the dust in the gas phase flowing through the gas flow path on a filter paper sandwiched between the upper and lower blocks, and By irradiating the filter paper with β-rays through the β-ray irradiation path, equipped with a measurement cell that measures the transmitted β-ray intensity of the filter paper before and after dust collection,
After measuring the transmission β-ray intensity of only the filter paper before dust collection, with the upper and lower blocks open, a calibration tool that covers the through holes on the support plate having the through holes and attaches an equivalent membrane is placed between the upper and lower blocks. A dust meter that manually inserts and then calibrates the equivalent membrane by closing the upper and lower blocks and measuring the transmitted β-ray intensity transmitted through the filter paper and the equivalent membrane,
A dust meter, wherein a recess having a depth larger than the thickness of the filter paper is formed in a region including a portion where the filter paper is disposed on the upper surface of the lower block, and the filter paper is in contact with the bottom surface of the recess.   2. The dust meter according to claim 1, wherein a front upper end portion of an inlet portion into which a calibration tool for the lower block is inserted protrudes forward from a front lower end portion of the same portion of the upper block.   A convex part is formed around the gas flow path on the lower surface of the upper block, and when measuring the transmitted β-ray intensity transmitted only through the filter paper, the convex part presses the filter paper against the lower block, and the filter paper and equivalent 3. The dust meter according to claim 1, wherein when the transmitted β-ray intensity transmitted through the membrane is measured, the convex portion presses the equivalent membrane against the filter paper and the lower block.

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