WO2004003534A1

WO2004003534A1 - Method and device for measuring water content of powder

Info

Publication number: WO2004003534A1
Application number: PCT/JP2003/008178
Authority: WO
Inventors: Tadashi Nishida; Ryoji Kanayama; Hiroaki Tokita; Hisashi Harada
Original assignee: Sintokogio, Ltd.
Priority date: 2002-07-01
Filing date: 2003-06-27
Publication date: 2004-01-08
Also published as: AU2003246089A1; JP2005288443A; TW200401890A

Abstract

A measuring head (10) has prolonged metal conductive elements (12) arranged in 1 row x n columns and held on an insulative holding member (3). The measuring head (10) has an upper surface (1a) which is a contact surface to be brought into contact with a power to be measured. On this contact surface (1a), the conductive elements (12) arranged in 1 row x n columns are exposed. The n columns of the conductive elements (12) consist of conductive elements (12) of the odd number columns connected to one another by a first wire (4a) and conductive elements (12) of the even number columns connected to one another by a second wire (4b). Accordingly, the n-column conductive elements (12) constitute 2-electrode electrode terminals having one electrode consisting of the conductive elements (12) belonging to the odd-number columns and the other electrode consisting of the conductive elements (12) belonging to the even-number columns. The powder to be measured is placed on the contact surface (1a) of the measuring head (10) and the voltage generated between the two electrodes of the measuring head (10) is measured, thereby obtaining the water content in the powder.

Description

Description Method and apparatus for measuring moisture value of powder specimen

In general, the present invention relates to a method and an apparatus for measuring a moisture value contained in a powder specimen containing powder and water. Background art

In a conventional sand processing line for processing sand, the water content and temperature of the sand that is continuously conveyed on a belt conveyor are measured before the kneader (or sand cooler). The amount of water that is insufficient is calculated, and the amount of water that is insufficient is injected into a kneading machine to adjust the mixing of natural sand.

従来 As a conventional moisture value measuring device for measuring the moisture value contained in material sand, Japanese Patent No. 32405000 assigned to the applicant of the present application (Japanese Patent Application Laid-Open No. 7-19009) As disclosed in Japanese Unexamined Patent Publication No. 75 (1995) -1995, there is known a measurement head employing a pair of plate-like electrodes. In this conventional measurement head, when a pair of plate-shaped electrodes are inserted into the sand from above while facing each other at a predetermined interval, and electricity is passed between the electrodes through the sand, the sand of the crimson sand is formed. An electric resistance value corresponding to the moisture value can be obtained. Therefore, by measuring the electric resistance value, the moisture value of the sand can be measured. Further, by correcting the electric resistance value based on the measured temperature of natural sand, a more accurate moisture value can be obtained.

However, the plate electrodes of conventional measurement heads are wide, large and bulky, and need to be inserted into natural sand from above, requiring a relatively large space for installation. The selection of the installation position (ie, measurement position) is subject to spatial restrictions. Therefore, the installation position of the conventional measurement head is limited to an open place such as above a transport path (typically, a belt conveyor) for transporting natural sand. Depending on the design of the processing line, it may be necessary to provide a conveyor path or belt conveyor specifically for measuring the moisture content of natural sand in order to secure the installation position of the conventional measurement head.

In addition, when a conventional measuring head is installed above the belt conveyor, the plate-shaped electrodes are inserted into the sand transported on the belt conveyor, and the sand spills from the belt conveyor to the surroundings during the measurement. Easy and deteriorating working environment.

Conventional moisture measurement devices as described above are not limited to natural sand, Also used in the process. For example, in the powder processing of ceramic raw materials such as ceramic raw materials and refractory raw materials, waste recycling raw materials such as steelmaking dust, and fertilizer raw materials, conventional processes such as compression, extrusion, rolling, etc., prior to molding and granulation, By measuring the water content of the raw material using the water content measuring device of the above, the water content is adjusted by the kneader. In this case as well, problems similar to those in the processing line for natural sand occur, such as limitations on the installation space due to the configuration of the conventional measuring head (a pair of plate-like electrodes), and deterioration of the working environment due to the generation of dust.

Accordingly, there is a need for a method and apparatus for measuring the moisture value of a powder which has been improved so as to be hardly affected by the installation space due to the configuration of the measuring head. Summary of the Invention

The present invention provides a moisture value measuring device for measuring a moisture value contained in a powder specimen containing powder and water, and a measuring head thereof. The measuring head has a contact surface to be brought into contact with the powder specimen, and i) a plurality of n conductive elements (where n is an integer of 3 or more) and ϋ) n conductive elements. Are arranged in a row Xn column at predetermined intervals and substantially parallel to each other along a row direction substantially orthogonal to the longitudinal direction thereof, and in the contact surface, the one row Xn column An insulating holding member for holding the conductive elements so as to be exposed, and iii) conductive elements belonging to odd-numbered rows of the n rows of conductive elements so that the n conductive elements form a two-electrode terminal. A first connection member electrically connecting the conductive elements to each other to form one pole, and a second connection electrically connecting the conductive elements belonging to the even rows to each other to form the other pole And a member.

The moisture value measuring device includes a measuring head as described above, means for supplying a constant current having a low-frequency rectangular wave to the two-pole terminal of the measurement head, and a constant-current powder between the two-pole terminal. Means for measuring the voltage generated between the two extremes when flowing through the subject, and for smoothing and outputting the measured value; the smoothed measured voltage value and the moisture contained in the powder subject Means for determining a moisture value contained in the powdery analyte based on a previously determined correlation with the value.

The moisture value measuring device includes: a temperature measuring means for measuring the temperature of the powder specimen; and, when determining the moisture value, the smoothed measurement voltage value is measured by the powder specimen measured by the temperature measuring means. And means for correcting based on the temperature of the powder sample, so that the determined moisture value reflects the temperature of the powder subject. In this case, a heating means provided on the insulating holding member for heating the conductive element may be further provided.

The present invention provides a powder coating containing powder and water using the measurement head as described above. Provided is a method for measuring a moisture value contained in a specimen based on an electric resistance value of a powder specimen. The method comprises the steps of supplying a constant current having a low-frequency square wave to the two-pole terminal of the measurement head;

Measuring a voltage generated between the two pole terminals when a constant current flows between the two pole terminals via the powder specimen, and smoothing and outputting the measured value; and Measuring, correcting the smoothed measured voltage value based on the temperature of the powder subject measured by the temperature measuring means, and including the corrected measured voltage value and the powder subject in the powder subject. Determining a moisture value contained in the powder analyte based on a predetermined correlation between the moisture value and the measured moisture value.

As used herein, the term “powder subject” refers to a subject containing powder and water. The term “powder” refers to a state in which a large number of particles are aggregated, and fine powder (0.1 to: Ιμπι), ordinary powder (1 to: ΙΟΟμππι), coarse powder (0.1 to: L mm ), A mixture of at least one of those roughly divided into granules (1 to 3 mm).

These powders include, but are not limited to, raw materials sand, ceramic raw materials, ceramic raw materials such as refractory raw materials, waste recycling raw materials such as steelmaking dust, and fertilizer raw materials.

In the present invention, as the sand, green sand, that is, bentonite as a binder is most suitable. The present invention can be easily applied to natural sand using a water-soluble binder such as starch and PVA as long as the binder uses other moisture. Natural sand is not limited to natural sand before use, but also includes recovered sand that is recovered and reused after use.

The moisture value of the powder test object is a moisture value contained in the powder test object, and is a percentage of the weight of water contained in the unit weight. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 shows a top view of the measurement head according to the first embodiment of the present invention.

FIG. 2 shows a longitudinal sectional view of the measuring head of FIG.

FIG. 3 shows a second embodiment of the present invention, and is a schematic block diagram of a moisture value measuring device using the measuring head of FIG.

FIG. 4 shows a third embodiment of the present invention, and is a schematic diagram in which the moisture value measuring device of FIG. 3 is applied to a sand treatment line.

FIG. 5 is a graph showing an example of the measurement of the moisture value of natural sand by the apparatus of FIG. Figure 6 is a graph showing the correlation between the water content of the sand and the impedance between the elements according to the number of conductive elements in the measurement head. FIG. 7 shows a longitudinal sectional view of a measurement head according to the fourth embodiment of the present invention.

FIG. 8 shows a fifth embodiment of the present invention, and is a schematic block diagram of an apparatus for measuring the moisture value of natural sand using the measurement head of FIG.

FIG. 9 is a graph showing a comparison of measured moisture values between the apparatus of FIG. 8 and a conventional apparatus.

Detailed Description of the Preferred Embodiment

1 and 2 show a top view and a longitudinal sectional view of a measurement head 10 according to the first embodiment of the present invention. The measurement head 10 is a long, narrow metal sheet that is arranged and held on the insulating holding member 14 in 1 row X n columns (n is an integer of 3 or more, and n = l 1 in the illustrated example). It has a conductive element 12. The conductive element 12 is preferably a metal having excellent corrosion resistance. The longitudinal direction of the conductive elements 12 is defined as a column direction, and a direction substantially perpendicular to the longitudinal direction is defined as a row direction. In the row direction, the n conductive elements 12 are arranged at predetermined intervals from each other and substantially in parallel. The upper surface 10a of the measurement head 10 is a contact surface that comes into contact with a powder specimen containing powder and water. In this contact surface, the conductive element 12 of 1 row X n column is exposed. The end of each conductive element 12 has a fastening portion (not shown) for connecting wiring 1.6a or 16b (FIG. 2) described later. The insulating holding member 14 is made of alumina ceramics, for example, and can be formed by firing after molding.

As shown in FIG. 2, in the n columns of conductive elements 12, the conductive elements 12 belonging to the odd columns are connected to the conductive elements 12 belonging to the even columns by the first wiring 16 a. Each is electrically connected to each other by wiring 16b. Therefore, the n rows of conductive elements 12 constitute a two-electrode terminal in which the conductive elements 12 belonging to the odd rows are on one side and the conductive elements 12 belonging to the even rows are on the other side. ing. As the wirings 16a and 16b, for example, generally used wires for electric wiring can be used.

Since the thin measurement head 10 configured in a planar manner as described above does not need to be inserted into the powder subject, an open installation space is not required. In addition, since the measurement can be performed simply by placing the powder sample on the contact surface, the problem of environmental deterioration due to the generation of dust can be solved.

FIG. 3 shows a second embodiment of the present invention, and shows a moisture value measuring apparatus 20 for measuring the moisture value of a powder specimen of the present invention using the measuring head 10 of FIGS. 1 and 2. . The measuring device 20 supplies the above-described measuring head 10 and a constant current having a low-frequency rectangular wave (a rectangular wave of 1 kHz or less) to the two-electrode terminals of the measuring head 10. The voltage between the two electrodes generated by the current flowing between the two electrodes of the rectangular wave constant current source 22 and the measurement head 10 through the powder test object is measured. And a voltage smoothing measuring circuit 24 for smoothing the voltage and outputting the smoothed voltage value. The measuring device 20 further obtains the powder analyte from the output value of the measurement circuit 24 based on a predetermined correlation between the output value of the measurement circuit 24 and the moisture value of the powder analyte. And an arithmetic circuit 26 for calculating the moisture value of the water. The previously determined correlation between the output value of the measurement circuit 24 referred to by the arithmetic circuit 26 and the moisture value of the powder sample is stored in a memory 28 a in advance as a reference table or a keyboard. May be provided to the memory 28a via the input device 28b.

FIG. 4 shows a third embodiment of the present invention, and shows an example in which the moisture value measuring device 20 of FIG. 3 is applied to a sand storage facility 30 in a processing line for natural sand. The storage facility 30 includes a kneader patch hopper 32 and a belt conveyor 34 as a cutting device. On the inner surface of the hopper 32, the measuring head 10 of the moisture content measuring device 20 (FIG. 3) has its contact surface 10a (the conductive element 12 is exposed as shown in FIG. 2). Surface is exposed inside the hopper 32. In FIG. 4, the measurement head 10 is schematically shown for simplicity of illustration. Since the thin measuring head 10 does not require an open installation space, it can be attached to the inner surface of the hopper 32, and there is no need to provide a transport path or a belt conveyor dedicated to moisture value measurement.

After the material sand S whose moisture value is to be measured is put into the storage facility 30, the water level is lowered from the square wave constant current supply source 2 2 (FIG. 3) of the moisture value measuring device 20 to the measuring head 10. A constant frequency rectangular wave current is supplied, and a current is caused to flow between the conductive elements 12 of the measurement head 10 via the sand S. At this time, the voltage generated between the two poles of the measurement head 10 is measured by the voltage smoothing measurement circuit 24 (FIG. 3). From this measurement result, the moisture value is obtained by the arithmetic circuit 26 (FIG. 3). Figure 5 shows an example of the moisture value obtained in this way.

In FIG. 5, the voltage on the vertical axis is voltage data measured and output by the voltage smoothing measurement circuit 24. The two types of mineral sands A and B used in the measurement differ in properties such as the proportion of clay in the composition, but both A and B have a good correlation between the water content of the sand and the voltage. Is recognized. As a result, it was confirmed that the water content of the natural sand from 0.8% to 3% can be measured properly.

Note that the voltage peaks at 10 V in FIG. 5 because the measurement circuit 24 sets the data of 10 V or more to 10 V. By changing this regulation, it is possible to measure more than 10 V, that is, more than 3% of sand moisture value. In Fig. 5, the voltage is 0 V when the water content of the sand is about 1% or less. By changing the level of the supply voltage from the square wave constant current supply source 22 to the measurement head 10, It is possible to measure less than 1% of water content of sand. As a basic test, multiple conductive elements 12 were arranged on a flat plate, and the impedance between the elements was measured with an LCZ meter. This test was performed by changing the shape of the element 12, the frequency applied to the element, the moisture of the green sand, and the temperature. Figure 6 shows the relationship between the moisture in the raw sand and the elements when the number of these elements is changed by arranging conductive elements 12 with a width of 10 mm × 20 mm and a length of 20 mm. The figure shows the results of a survey of impedance correlation. From Fig. 6, it can be seen that the correlation between moisture and impedance is low when three elements 12 are used, and a sufficient correlation cannot be obtained when five elements 12 are used. It was found that a higher correlation was obtained when the number of elements 12 was increased to 7, 9, and 11. When the number of elements 12 is further increased, the area of the measurement head 10 increases, and the installation space is restricted. As a result, it is possible to stably measure the moisture value of green sand with good accuracy by arranging about 7 to 11 elements 12 with a pitch of 20 mm and a length of 200 mm with a pitch of 20 mm. Was confirmed.

When higher measurement accuracy is required, it is necessary to prevent erroneous measurement due to adhesion of sand to the conductive element 12.

FIG. 7 shows a measuring head 40 according to a fourth embodiment of the present invention for this purpose. The measuring head 30 is obtained by providing a heating member 42 via an insulating holding member 14 to the measuring head 10 (FIGS. 1 and 2) of the first embodiment. Here, the heating member 42 is a sheet-like electric heater, and is supplied with power from a suitable power supply (not shown in FIG. 7) via a wiring 44, and the heating temperature is controlled. By heating the conductive element 12 by the heating member 42 via the insulating holding member 14, dew condensation on the conductive element 12 can be prevented, and thus, adhesion of sand to the conductive element 12 can be prevented. Can be prevented.

The smoothed voltage value output from the voltage smoothing measurement circuit 24 in FIG. 3 changes depending on the sand temperature even if the moisture value is the same. Therefore, in order to achieve higher measurement accuracy, it is necessary to consider the effect of sand temperature.

FIG. 8 shows a fifth embodiment of the present invention for this purpose, and shows a device 50 for measuring the moisture value of natural sand of the present invention using the measuring head 40 of FIG. In this device 50, a rectangular wave constant current supply source 22 and a voltage smoothing measurement circuit 24 are the same as those of the moisture value measurement device 20 (FIG. 3) of the second embodiment. The operation circuit 26 also has the same force S as that of the moisture value measuring device 20 and the input voltage data is different from that of the moisture value measuring device 20.

The device 50 further includes a power supply 52 for supplying power to the heating member 42, a temperature sensor 54 such as a thermocouple for measuring sand temperature, and a smoothed voltage value output from the voltage smoothing measurement circuit 24 for temperature. A correction circuit 56 for correcting based on the sand temperature measured by the sensor 54. Temperature correction of smoothed voltage value corrected based on sand temperature It is called a voltage value. The correction circuit 56 calculates the temperature correction voltage value according to the following relational expression.

Temperature correction voltage value = Smoothed voltage value + (first constant-sand temperature) x second Here, the first constant is the reference temperature of sand. The second constant is a voltage value that changes according to the amount of change in temperature, and is represented by VZ ° C.

The arithmetic circuit 26 calculates the output value of the correction circuit 56 from the output value of the correction circuit 56 based on a predetermined correlation between the temperature correction smoothing voltage value output from the correction circuit 56 and the moisture value of the material sand. Find the moisture value of the material sand. Therefore, the moisture value can be measured without being affected by the temperature of the sand. The correlation referred to by the arithmetic circuit 26 is determined by a force previously stored in the memory 28a as a reference table in the same manner as the moisture value measuring device 20 of the second embodiment, or an input device 2 such as a keyboard. It may be provided to the memory 28a via 8b.

A field test was carried out to apply such a device 50 for measuring the moisture content of natural sand to a batcher kneading machine in a sand processing line, and to compare the moisture measurement status with the existing conventional device. . As a conventional device, a batch moisture controller (BMIC) manufactured and sold by Shinto Kogyo Co., Ltd., the assignee of the present application, was used. This BMIC uses the property that the electric resistance value decreases as the moisture value in the sand increases, and the BMIC regenerates the recovered sand (that is, the used sand used in the mold molding). The value is controlled with high precision. The BMIC measures the moisture value of the recovered sand cooled by the sand cooler, and reclaims the recovered sand by injecting the insufficient water with respect to the set moisture value into the recovered sand.

FIG. 9 shows the results of the field test, showing a comparison between the measured value of moisture by the device 50 and the measured value of BMIC. The moisture conversion value of the device 50 according to the present invention showed the same transition as the moisture of the BMIC, and did not fall outside the range of 2% of the moisture content of the 3BMIC. Also, no adhesion of sand to the conductive element 12 was observed. Furthermore, a temperature sensor 54 and a correction circuit 56 are provided in the measuring device 50, and the smoothed voltage value of the voltage smoothing measuring circuit 24 is temperature-corrected. As a result, the correlation between the moisture of the sand and the smoothed voltage value is obtained. Was further strengthened.

Since the reliability of kneading control can be enhanced by accurately measuring the moisture value of the sand, the sand optimal for the molding of the sand can be adjusted. Although the example in which the heads 10 and 40 are provided on the inner surface of the kneader / batch hopper of the sand processing line has been described, they may be provided on the inner surface of other equipment in the sand processing line as follows.

1) Sand storage means, such as sand bins and sand No ^ The sieve device on the sand processing line, the hopper attached to the sand cooler, the first hopper provided in the molding machine (the hopper that is placed in the molding machine and stores the material sand used for molding), the molding Inner surface of a second hopper (a hopper for supplying a predetermined amount of sand to the first hopper) provided directly above the machine.

2) Processing means for processing natural sand in a sand processing line, for example, a kneading machine that adjusts natural sand suitable for molding by adding a binder, water, etc. to natural sand, and pouring. The inner surface of a sand cooler that cools the sand, sometimes heated with molten metal, in the process of a sand treatment line.

3) A transfer means for transferring sand, which is installed in the sand transfer section, typically the inner surface of the shoot. Such a chute is provided, for example, between a natural sand conveying means such as a bucket conveyor, a belt conveyor, and an oscillating conveyor, and each device such as a storage in a sand processing line.

In any case, the inner surface includes an inner wall surface, an inner surface, and a bottom surface that define an open space or a closed space, and these surfaces include not only a vertical surface and a horizontal surface but also an inclined surface. The equipment in the sand processing lines 1) to 3) are not shown because they are known to those skilled in the art.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the purpose and spirit of the invention as defined in the appended claims. For example, the powder specimen is not limited to sand but may be other powder. In this case, the measurement heads 10 and 40 should be attached at the start and end points for pneumatic transportation of the powder by the inner surface of the storage means and water, etc., according to the intended use of the powder. The inner surface of the kneader to mix is conceivable. The definition of the inner surface is the same as that of the sand processing line.

The measurement head of the present invention may be attached to the inner surface of a hopper of a compression granulator such as a known briquetting machine or a pelletizer to measure the moisture value of the powder. By controlling the rotation speed and compression force according to the measured values, it is possible to adjust the powder that is optimal for molding, granulation, such as compression, extrusion, and rolling.

Claims

Claims: An apparatus for measuring a moisture value contained in a powder specimen containing powder and water, the apparatus comprising a measurement head having a contact surface to be brought into contact with the powder specimen. The measurement head includes: i) a plurality of n (n is an integer of 3 or more) elongated conductive elements; and ϋ) the η conductive elements in a row direction substantially orthogonal to a longitudinal direction thereof. A predetermined distance from each other and arranged substantially in parallel in one row X η column, and an insulating property for holding the conductive element in the one row X η column exposed at the contact surface. Iii) electrically connect the conductive elements belonging to the odd-numbered rows among the n-number of conductive elements so that the n-number of conductive elements constitute a two-electrode terminal. The first connection member forming one of the poles and the conductive elements belonging to the even-numbered rows are electrically connected to each other to form the other pole. And a second connection member forming a constant current having a low-frequency rectangular wave to the two-pole terminal of the measurement head; and Means for measuring the voltage generated between the two-pole terminals when flowing through the powdery subject between the two-pole terminals and smoothing and outputting the measured value; and the smoothed measured voltage value Means for determining a moisture value contained in the powder analyte based on a predetermined correlation between the water content and the moisture content contained in the powder analyte. The apparatus according to claim 1, wherein a temperature measuring means for measuring a temperature of the powder specimen; and, in determining the moisture value, the smoothed measured voltage value is measured by the powder measuring means measured by the temperature measuring means. Means for correcting based on the temperature of the specimen, whereby the determined moisture value is corrected based on the temperature of the powder specimen. 3. The device according to claim 2, further comprising a heating means provided on the insulating holding member, for heating the conductive element. An apparatus for measuring the moisture content of sand in a sand processing line, comprising a measuring head having a contact surface to be brought into contact with the sand, the measuring head comprising: i) a plurality of n heads ( Wherein n is an integer of 3 or more), and ϋ) the η conductive elements are spaced apart from each other at a predetermined distance from each other along a row direction substantially orthogonal to the longitudinal direction. An insulative holding member that is arranged in parallel in 1 row X η column and that holds the conductive element on the contact surface so that the conductive element in the 1 row X η column is exposed; iii) the n conductive elements The first connection in which the conductive elements belonging to the odd-numbered rows among the n rows are electrically connected to each other to form one pole so that the elements form a two-pole electrode terminal. A second connection in which the member and the conductive elements belonging to the even rows are electrically connected to each other to form the other pole Means for supplying a constant current having a low-frequency rectangular wave to the two-pole terminal of the measurement head, wherein the constant current is provided with sand between the two-pole terminal. Means for measuring a voltage generated between the two poles when flowing, and smoothing and outputting the measured value; a temperature measuring means for measuring the temperature of sand; and measuring the smoothed measured voltage value. Means for correcting based on the temperature of the sand measured by the temperature measuring means, based on a predetermined correlation between the corrected measured voltage value and a moisture value contained in the sand, Means for determining a moisture value contained in the sand. 5. The device according to claim 4, further comprising a heating means provided on the insulating holding member, for heating the conductive element. The apparatus according to claim 4, wherein the sand is natural sand before or after use. The apparatus according to claim 6, wherein the processing line includes storage means for storing sand, and processing means for processing sand. And a transfer means for transferring the sand. The apparatus according to claim 7, wherein the position of the measurement head is an inner surface of at least one of the storage means, the processing means, and the transfer means. A contact that is used in a moisture measurement device that measures the moisture content of a powder specimen containing powder and water based on the electrical resistance value of the powder specimen, and that should make contact with the powder specimen. A measurement head having a plurality of n (where n is an integer of 3 or more) elongated conductive elements, and the n conductive elements are arranged in a row direction substantially orthogonal to a longitudinal direction thereof. Along a predetermined distance and substantially parallel to each other, they are arranged in one row and Xn columns, and the conductive elements of one row and Xn columns are held at the contact surface so as to be exposed. Among the conductive elements in the η rows, conductive elements belonging to an odd-numbered row are electrically connected to each other so that an insulating holding member and the n conductive elements constitute a two-electrode terminal. The first connection member forming one of the poles and the conductive elements belonging to the even-numbered rows are electrically connected to each other. A measuring head comprising a second connecting member forming the other pole. 0. The measuring head according to claim 9, wherein the powder subject is natural sand before or after use.

1.A method for measuring a moisture value contained in a powder specimen containing powder and water based on an electric resistance value of the powder specimen,

a) providing a measurement head having a contact surface to be brought into contact with the powder specimen,

i) a plurality of n (where n is an integer of 3 or more) elongate conductive elements; and ϋ) the η conductive elements are mutually fixed along a row direction substantially orthogonal to the longitudinal direction thereof. An insulating holding member that is arranged at intervals and substantially parallel to one row X η column, and that holds the conductive element of the one row X η column exposed at the contact surface;

iii) One of the n columns of conductive elements is electrically connected to an odd row of the n rows of conductive elements such that the n pieces of conductive elements form a two-pole electrode terminal. And a second connecting member that electrically connects the conductive elements belonging to the even rows to each other to form the other pole,

The method further comprises:

b) supplying a constant current having a low-frequency square wave to the two-pole terminal of the measurement head;

c) measuring the voltage generated between the two pole terminals when the constant current flows through the powder subject between the two pole terminals, and smoothing and outputting the measured value; ,

d) measuring the temperature of the powder analyte;

e) measuring the smoothed measured voltage value by the temperature measuring means; Correcting based on the corrected temperature of the powder analyte, and f) based on a predetermined correlation between the corrected measured voltage value and the moisture value contained in the powder analyte. Determining the level of moisture contained in the powder analyte.

2. The method according to claim 11, wherein the powdery subject is natural sand before or after use.