JPH07119726B2 - Method of measuring water content - Google Patents
Method of measuring water contentInfo
- Publication number
- JPH07119726B2 JPH07119726B2 JP2333058A JP33305890A JPH07119726B2 JP H07119726 B2 JPH07119726 B2 JP H07119726B2 JP 2333058 A JP2333058 A JP 2333058A JP 33305890 A JP33305890 A JP 33305890A JP H07119726 B2 JPH07119726 B2 JP H07119726B2
- Authority
- JP
- Japan
- Prior art keywords
- water content
- timber
- dielectric
- capacitor
- resonance frequency
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 title claims description 30
- 238000000034 method Methods 0.000 title claims description 12
- 239000003990 capacitor Substances 0.000 claims description 13
- 239000002184 metal Substances 0.000 description 28
- 238000005259 measurement Methods 0.000 description 13
- 239000004020 conductor Substances 0.000 description 5
- 238000010586 diagram Methods 0.000 description 5
- 238000001035 drying Methods 0.000 description 5
- 239000000463 material Substances 0.000 description 3
- 239000002023 wood Substances 0.000 description 3
- 239000003989 dielectric material Substances 0.000 description 2
- 238000000691 measurement method Methods 0.000 description 2
- 230000007423 decrease Effects 0.000 description 1
- 230000002500 effect on skin Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 239000000523 sample Substances 0.000 description 1
- 239000002344 surface layer Substances 0.000 description 1
Landscapes
- Investigating Or Analyzing Materials By The Use Of Electric Means (AREA)
Description
本発明は、含水率の測定方法に関する。 The present invention relates to a method for measuring water content.
材木、食品等の誘電体（以下材木等と称する）の含水率
を測定する場合、現在は、材木等に探針を２本差しその
間の導電率から測定する方法、あるいは材木等の一部を
材料片として切出しその重量と、乾燥器（オーブン）の
中に一昼夜入れ十分に乾燥させた重量との比により測定
する方法等が用いられている。 しかし、これらの方法は、材木等の中心部の含水率が測
定できない、材木等に傷をつける、時間がかかる、食品
のように不定形材料では測定しにくい等の問題がある。When measuring the water content of a dielectric such as timber or food (hereinafter referred to as timber), currently, a method of inserting two probes into the timber, etc. and measuring from the conductivity between them, or a part of the timber, etc. A method is used in which the weight is cut out as a piece of material and the weight of the piece is put into a drier (oven) for one day to be sufficiently dried and then measured. However, these methods have problems that the water content of the central part of timber and the like cannot be measured, the timber and the like are scratched, it takes time, and it is difficult to measure it with an amorphous material such as food.
このように、従来の含水率測定法は、材木等の中心部の
含水率が測定できない、材木等に傷をつける、時間がか
かる、食品のように不定形材料では測定しにくい等の問
題があった。 本発明は上記問題点に鑑みなされたもので、その目的と
するところは、短時間に、安定して所望の部材の所定部
の含水率の測定が可能な含水率の測定方法を提供するこ
とにある。As described above, the conventional water content measurement methods have problems that the water content of the central portion of timber and the like cannot be measured, the timber and the like are scratched, it takes time, and it is difficult to measure with amorphous materials such as food. there were. The present invention has been made in view of the above problems, and an object thereof is to provide a water content measuring method capable of stably measuring the water content of a predetermined portion of a desired member in a short time. It is in.
上記目的を達成するための本発明に係る含水率の測定方
法は、同軸ケーブルが接続された不平衡型コンデンサー
に直列に、シールドされたインダクタンスを接続して直
列共振回路を構成し、水を含んだ誘電体を前記コンデン
サの一対の電極間に挿入し、前記コンデンサーの一方の
電極で前記誘電体を包むシールド系を構成し、前記誘電
体に前記直列共振回路を介して電磁波を供給して電磁波
の直列共振周波数を求め、この直列共振周波数から前記
誘電体の含水率を求めることを特徴とする。The method for measuring the water content according to the present invention to achieve the above object is to provide a series resonance circuit by connecting a shielded inductance in series to an unbalanced capacitor to which a coaxial cable is connected, and to include water. A dielectric is inserted between a pair of electrodes of the capacitor, one electrode of the capacitor constitutes a shield system that wraps the dielectric, and an electromagnetic wave is supplied to the dielectric through the series resonant circuit to generate an electromagnetic wave. Is obtained, and the water content of the dielectric is obtained from the series resonance frequency.
本発明の方法は、材木等の誘電率εが水の含有率によっ
て変化することを利用している。誘電体を不平衡型シー
ルド系で構成された測定器内に設置して、材木等の内部
に浸透し、材木等を変質させない弱い電磁波を材木等に
供給すると特定の周波数で共振現象が生ずる。種々の材
木等の共振周波数と水の含有率との関係をあらかじめ求
めておくと、測定すべき材木等の共振周波数を求めれ
ば、その材木等の水の含水率を求めることができる。The method of the present invention utilizes the fact that the permittivity ε of timber or the like changes depending on the water content. A resonance phenomenon occurs at a specific frequency when a dielectric material is installed in a measuring instrument composed of an unbalanced type shield system and a weak electromagnetic wave that penetrates into the timber or the like and does not deteriorate the timber or the like is supplied to the timber or the like. If the relationship between the resonance frequency of various timbers and the water content is obtained in advance, the water content of the timber or the like can be obtained by obtaining the resonance frequency of the timber or the like to be measured.
以下、図面を参照しながら実施例を説明する。 図１に示す一対の平行金属平板10、12はコンデンサを構
成していて、そのキャパシタンスＣは式（１）により表
される。 Ｃ＝εA/s ［Ｆ］ ……（１） ここで、Ａは平行金属板の面積［m2］、ｓは平行金属板
間の間隔［ｍ］、εは平行金属板間の誘電率である。 平行金属板の間に材木等が挟まれた場合、含水率の違い
により誘電率εが変わるので、式（１）からキャパシタ
ンスＣの違いとして求めることができる。 一般に、図２に示すように平行金属板10,12の間に材木
等14を挟むことから、平行金属板10,12の面積Ａと平行
金属板10,12間の間隔ｓは挟まれる材木等14により制限
され、キャパシタンスＣの値は、結果的にあまり大きく
ならない。 しかも、この様な間隔が広く、解放された平衡型コンデ
ンサにおいては、外部の影響を受け安く、安定した測定
が困難となる。 図３は本発明の方法に使用できる不平衡型測定器を示し
ていて、金属枠16に同軸栓18が接続され、同軸栓18の外
部導体は金属枠16に接続されると共に、同軸栓18の内部
導体は導線20により金属枠16内の金属板22に接続された
構造となっている。このため、金属枠16と内部金属板22
との間が、外部から遮蔽された不平衡型コンデンサを構
成している。従って、この不平衡型コンデンサによりキ
ャパシタンスＣが定まり、しかも不平衡型のため外部の
影響を防止できる。 金属枠16と内部金属板22との間に木材等14を挿入する
と、その木材等14の誘電率εによりキャパシタンスＣの
値が変化する。 当然、挿入する木材等14の含水率が変われば、誘電率ε
が変わるため、キャパシタンスＣの値もそれに応じて変
わってくる。更に、同軸栓18と金属板22とを結ぶ導線20
は、インダクタンスＬとなるので、同軸栓18から見たこ
の測定器の電気的等価回路は、図４のようになる。即
ち、インダクタンスＬとキャパシタンスＣが直列に接続
された構成である。 この等価回路は以下の式（２）の関係を満たすとき直列
共振回路として機能する。 fr＝1/｛２π（LC）1/2｝ ［Hz］ ……（２） ここで、frは共振周波数［Hz］、Ｌは同軸栓18と内部金
属板22とを結ぶ導線のインダクタンス［Ｈ］、Ｃは金属
枠16と内部金属板22とで決まるキャパシタンス［Ｆ］で
ある。 即ち、式（２）を満たす周波数の電磁波を供給すると
き、この回路は最もインピーダンスが小さくなり、オー
ムの法則から最大の電流が流れることとなる。 しかも、測定器の構造が決まった場合、式（２）のイン
ダクタンスＬの値は一定で、キャパシタンスＣの値は式
（１）から分かるように原理的に平行金属板の挟まれた
材木等の誘電率εの違いで決まることから、共振周波数
は、誘電率εの違いで決まることとなる。即ち、材木等
に含まれる水分により誘電率が決まるから、材木等の水
分により共振周波数frが変わることとなる。 しかし、図３に示すように、金属板22の面積は大きくな
く、金属枠16と金属板22との間隙が広いことから、キャ
パシタンスＣの値は小さく、またインダクタンスＬの値
も導線20のみとすると、かなり小さな値になる。 以上のことから、共振周波数frの値は式（２）からかな
り高い周波数となる。高い周波数の場合、測定器も特殊
で、高価になると共に、表皮効果により材木等の内部の
電磁波が入り難くなる虞がある場合もある。 このような場合には、式（２）からインダクタンスＬか
キャパシタンスＣを大きくすると、共振周波数を低くで
きる。例えば、Ｌを大きくする場合には、式（３）及び
図４から、回路に直列にインダクタンス（コイル）を挿
入するか、図３の導線20をコイル状にすれば良い。例と
して図５にコイル24を付加した実施例を示す。図５にお
いて、その他の構成は図３の実施例と同じであるので、
同一箇所には同一符号を付してその詳細な説明は省略す
る。 図６は不平衡型である同軸ケーブルで各機器を接続して
構成した測定システムの一例を示している。この測定シ
ステムは、本発明の図３または図５に示された不平衡型
測定器26、ネットワーク・アナライザ28、及びパソコン
30を用いて構成されている。この測定システムで測定さ
れた一例として、含水率の違いにより共振点（共振周波
数f1,f2）が違ってくる状態を図７に示す。この測定結
果から得られた共振周波数と含水率の関係の一例は図８
のようになる。即ち、図８から明らかなように、含水率
が増加すると共振周波数が低くなる。このグラフを基準
にして、未知の含水率を有する材木等の共振周波数を測
定すると、その材木等の含水率を求めることができる。
なお、ここで含水率とは以下の式により定義される。 含水率（％） ＝［（乾燥前の重量（ｇ）−全乾燥時の重量（ｇ）） ／（前乾燥時の重量（ｇ））］×100 以上から、本発明は、シールド系で構成された測定器の
内部に材木等を挿入し、共振周波数を測定することによ
り、外部からの雑音等に妨害されることなく含水率を短
時間に安定して求めることができる。 従来の導電率法は簡易に測定できるが、測定部が表層部
に限定され、不均一な厚い材木等の測定においては誤差
を生ずるし、従来の重量比による方法は時間がかかり過
ぎ、切り出した場所による変化があること等の問題があ
るが、本発明はこの様な問題を一挙に解決できる。 なお、本発明は上記実施例に限定されない。種々変形し
て実施できる。例えば、本発明の測定装置を乾燥器等の
中に組み込んでも測定可能である。このようにすると、
乾燥不足や、乾燥させ過ぎ等を防ぐことができ、結果的
に省エネルギーにも効果がある。Hereinafter, embodiments will be described with reference to the drawings. The pair of parallel metal flat plates 10 and 12 shown in FIG. 1 constitutes a capacitor, and the capacitance C thereof is expressed by the equation (1). C = εA / s [F] (1) where A is the area [m 2 ] of the parallel metal plates, s is the space [m] between the parallel metal plates, and ε is the dielectric constant between the parallel metal plates. is there. When timber or the like is sandwiched between the parallel metal plates, the dielectric constant ε changes due to the difference in water content, so that the difference in capacitance C can be obtained from equation (1). Generally, as shown in FIG. 2, since lumber or the like 14 is sandwiched between the parallel metal plates 10 and 12, the area A of the parallel metal plates 10 and 12 and the interval s between the parallel metal plates 10 and 12 are sandwiched between the lumber and the like. Limited by 14, the value of the capacitance C will not be too large as a result. Moreover, in such an open balanced capacitor having such a wide interval, it is less susceptible to external influences and stable measurement becomes difficult. FIG. 3 shows an unbalanced type measuring instrument that can be used in the method of the present invention. A coaxial plug 18 is connected to a metal frame 16, an outer conductor of the coaxial plug 18 is connected to the metal frame 16, and the coaxial plug 18 is connected. The internal conductor of is structured to be connected to the metal plate 22 in the metal frame 16 by the conductor wire 20. Therefore, the metal frame 16 and the inner metal plate 22
And between and form an unbalanced capacitor shielded from the outside. Therefore, the capacitance C is determined by this unbalanced type capacitor, and since it is an unbalanced type, external influence can be prevented. When wood 14 or the like is inserted between the metal frame 16 and the internal metal plate 22, the value of the capacitance C changes depending on the dielectric constant ε of the wood 14 or the like. Naturally, if the water content of the inserted wood 14 changes, the permittivity ε
Changes, the value of the capacitance C also changes accordingly. Further, a conductor 20 connecting the coaxial plug 18 and the metal plate 22.
Becomes the inductance L, so that the electrical equivalent circuit of this measuring instrument viewed from the coaxial plug 18 is as shown in FIG. That is, the inductance L and the capacitance C are connected in series. This equivalent circuit functions as a series resonance circuit when the relation of the following expression (2) is satisfied. fr = 1 / {2π (LC) 1/2 } [Hz] (2) where fr is the resonance frequency [Hz] and L is the inductance [H of the conductor connecting the coaxial plug 18 and the inner metal plate 22. ] And C are capacitances [F] determined by the metal frame 16 and the internal metal plate 22. That is, when an electromagnetic wave having a frequency satisfying the expression (2) is supplied, this circuit has the smallest impedance and the maximum current flows according to Ohm's law. Moreover, when the structure of the measuring device is determined, the value of the inductance L in the formula (2) is constant, and the value of the capacitance C is theoretically as shown in the formula (1). Since it is determined by the difference in permittivity ε, the resonance frequency is determined by the difference in permittivity ε. That is, since the dielectric constant is determined by the water content of the timber, the resonance frequency fr is changed by the water content of the timber. However, as shown in FIG. 3, since the area of the metal plate 22 is not large and the gap between the metal frame 16 and the metal plate 22 is wide, the value of the capacitance C is small and the value of the inductance L is only the conductive wire 20. Then, it becomes a very small value. From the above, the value of the resonance frequency fr becomes a considerably high frequency from the equation (2). When the frequency is high, the measuring device is also special and expensive, and there is a possibility that electromagnetic waves inside the timber or the like may be difficult to enter due to the skin effect. In such a case, the resonance frequency can be lowered by increasing the inductance L or the capacitance C from the equation (2). For example, in order to increase L, an inductance (coil) may be inserted in series with the circuit from Expression (3) and FIG. 4, or the conducting wire 20 in FIG. 3 may be coiled. As an example, FIG. 5 shows an embodiment in which the coil 24 is added. In FIG. 5, the other structure is the same as that of the embodiment of FIG.
The same parts are designated by the same reference numerals, and detailed description thereof will be omitted. FIG. 6 shows an example of a measurement system configured by connecting each device with an unbalanced coaxial cable. This measuring system comprises an unbalanced measuring device 26, a network analyzer 28, and a personal computer shown in FIG. 3 or 5 of the present invention.
It is constructed using 30. As an example measured by this measurement system, FIG. 7 shows a state in which the resonance points (resonance frequencies f1 and f2) differ due to the difference in water content. An example of the relationship between the resonance frequency and the water content obtained from this measurement result is shown in FIG.
become that way. That is, as is clear from FIG. 8, the resonance frequency decreases as the water content increases. When the resonance frequency of timber or the like having an unknown water content is measured based on this graph, the water content of the timber or the like can be obtained.
The water content here is defined by the following formula. Moisture content (%) = [(weight before drying (g) -weight after total drying (g)) / (weight before drying (g))] x 100 From the above, the present invention comprises a shield system. By inserting a timber or the like into the measured instrument and measuring the resonance frequency, the moisture content can be stably obtained in a short time without being disturbed by noise from the outside. Although the conventional conductivity method can be easily measured, the measurement part is limited to the surface layer part, and an error occurs in the measurement of non-uniform thick timber, etc. The present invention can solve such problems all at once, though there are problems such as changes depending on places. The present invention is not limited to the above embodiment. Various modifications can be implemented. For example, the measurement can be performed by incorporating the measuring device of the present invention into a dryer or the like. This way,
It is possible to prevent insufficient drying or excessive drying, and as a result, it is also effective in saving energy.
本発明の方法によれば、共振周波数を点周波数として測
定できるので、測定精度が向上すると共に、測定の自動
化が可能であり、かつ短時間に測定できる。 本発明では、共振回路として直列共振回路を用いてお
り、かつコンデンサーの中に被測定物としての誘電体を
挿入しているので、損失を考慮する必要がなく、全体を
シールドできるため、精度の良い、安定した測定ができ
る。 本発明では、不平衡型構成を採用しているので、外部か
らの雑音等に妨害されることなく含水率を短時間に安定
して求めることができる。According to the method of the present invention, since the resonance frequency can be measured as the point frequency, the measurement accuracy is improved, the measurement can be automated, and the measurement can be performed in a short time. In the present invention, since the series resonance circuit is used as the resonance circuit and the dielectric material as the DUT is inserted in the capacitor, it is not necessary to consider the loss, and the whole can be shielded. Good and stable measurement is possible. In the present invention, since the unbalanced structure is adopted, the water content can be stably obtained in a short time without being disturbed by noise or the like from the outside.
【図１】 平行金属平板コンデンサの概念図。FIG. 1 is a conceptual diagram of a parallel metal plate capacitor.
【図２】 平行金属平板コンデンサに材木等を挟ませた図。FIG. 2 is a diagram showing a parallel metal plate capacitor with lumber or the like sandwiched therein.
【図３】 本発明の第１実施例に係る不平衡型測定器の部分断面
図。FIG. 3 is a partial cross-sectional view of the unbalanced measuring device according to the first embodiment of the present invention.
【図４】 本発明の第１実施例に係る不平衡型測定器の等価回路
図。FIG. 4 is an equivalent circuit diagram of the unbalanced measuring instrument according to the first embodiment of the present invention.
【図５】 本発明の第２実施例に係る不平衡型測定器の部分断面図
であり、共振周波数を低くするためにコイルを装荷した
図。FIG. 5 is a partial cross-sectional view of the unbalanced measuring instrument according to the second embodiment of the present invention, in which a coil is loaded to lower the resonance frequency.
【図６】 本発明の測定方法を実行するための測定システムのブロ
ック図。FIG. 6 is a block diagram of a measurement system for executing the measurement method of the present invention.
【図７】 含水率の違いによる共振周波数の変化を示す図。FIG. 7 is a diagram showing a change in resonance frequency due to a difference in water content.
【図８】 本発明の不平衡型測定器を用いた測定結果から得られた
共振周波数と含水率との関係を示すグラフ。FIG. 8 is a graph showing the relationship between the resonance frequency and the water content obtained from the measurement results using the unbalanced measuring device of the present invention.
10,12……平行金属平板、14……材木等、16……金属
枠、18……同軸栓、20……導線、22……金属板、24……
コイル、26……本発明の不平衡型測定器、28……ネット
ワーク・アナライザ、30……パソコン10,12 …… Parallel metal flat plate, 14 …… Timber, 16 …… Metal frame, 18 …… Coaxial plug, 20 …… Conducting wire, 22 …… Metal plate, 24 ……
Coil, 26 ... Unbalanced measuring instrument of the present invention, 28 ... Network analyzer, 30 ... Personal computer
Claims (1)
ンサーに直列に、シールドされたインダクタンスを接続
して直列共振回路を構成し、水を含んだ誘電体を前記コ
ンデンサの一対の電極間に挿入し、前記コンデンサーの
一方の電極で前記誘電体を包むシールド系を構成し、前
記誘電体に前記直列共振回路を介して電磁波を供給して
電磁波の直列共振周波数を求め、この直列共振周波数か
ら前記誘電体の含水率を求めることを特徴とする含水率
の測定方法。1. A series resonance circuit is constructed by connecting a shielded inductance in series to an unbalanced capacitor to which a coaxial cable is connected, and a dielectric containing water is inserted between a pair of electrodes of the capacitor. Then, one electrode of the capacitor constitutes a shield system that wraps the dielectric, and an electromagnetic wave is supplied to the dielectric through the series resonance circuit to obtain a series resonance frequency of the electromagnetic wave. A method for measuring water content, which comprises determining the water content of a dielectric.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2333058A JPH07119726B2 (en) | 1990-11-29 | 1990-11-29 | Method of measuring water content |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2333058A JPH07119726B2 (en) | 1990-11-29 | 1990-11-29 | Method of measuring water content |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH04198847A JPH04198847A (en) | 1992-07-20 |
| JPH07119726B2 true JPH07119726B2 (en) | 1995-12-20 |
Family
ID=18261799
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP2333058A Expired - Lifetime JPH07119726B2 (en) | 1990-11-29 | 1990-11-29 | Method of measuring water content |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH07119726B2 (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104977329A (en) * | 2015-06-10 | 2015-10-14 | 常州大学 | Capacitance method for measuring volumetric water content of soil |
| CN104977330A (en) * | 2015-06-24 | 2015-10-14 | 常州大学 | Soil volumetric water content measuring method based on one-chip microcomputer |
Families Citing this family (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2750498B2 (en) * | 1993-12-27 | 1998-05-13 | 鹿児島県 | Wood moisture content measuring device |
| WO1996032634A1 (en) * | 1995-04-13 | 1996-10-17 | Sumitomo Forestry Co., Ltd. | Moisture sensor for wooden material and automatic moisture content measuring device |
| JP3900410B2 (en) * | 2002-01-16 | 2007-04-04 | 株式会社エンゼルハウス | Capacitive moisture meter |
| JP4652788B2 (en) * | 2004-11-30 | 2011-03-16 | 株式会社ケット科学研究所 | Moisture measuring equipment for concrete, mortar, wood, etc. |
| JP4827239B2 (en) * | 2006-01-17 | 2011-11-30 | 株式会社ケット科学研究所 | Defect detection / filling degree measuring apparatus for concrete during placing and method for detecting and filling the defect |
| JP6652944B2 (en) * | 2016-04-07 | 2020-02-26 | 国立大学法人東京農工大学 | Food inspection device and food inspection method |
| CN112683965B (en) * | 2020-12-03 | 2021-11-09 | 华北电力大学 | Composite material dielectric constant calculation method and system |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS62261054A (en) * | 1986-05-07 | 1987-11-13 | Masao Yanami | Measuring apparatus for moisture contained in soil, ready-mixed concrete and the like |
| JPH01244343A (en) * | 1988-03-25 | 1989-09-28 | Iwatsu Electric Co Ltd | Wideband measurement cell |
| JPH0255944A (en) * | 1988-08-22 | 1990-02-26 | Mitsubishi Heavy Ind Ltd | Water content measuring instrument |
-
1990
- 1990-11-29 JP JP2333058A patent/JPH07119726B2/en not_active Expired - Lifetime
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104977329A (en) * | 2015-06-10 | 2015-10-14 | 常州大学 | Capacitance method for measuring volumetric water content of soil |
| CN104977330A (en) * | 2015-06-24 | 2015-10-14 | 常州大学 | Soil volumetric water content measuring method based on one-chip microcomputer |
Also Published As
| Publication number | Publication date |
|---|---|
| JPH04198847A (en) | 1992-07-20 |
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