JP2006003333A - Powder measuring electrostatic capacity sensor - Google Patents
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本発明は粉体の流量を静電容量の変化として測定する粉体計測用静電容量計測装置に関し、特に、粉体を通過させる測定用静電容量センサーの静電容量値を可能な限り微小にすると同時に静電容量センサー内の電界強度分布が一様な強度分布を得る事が出来る構造及び交流発振器と増幅器との接続に関するものである。 The present invention relates to a capacitance measuring device for powder measurement that measures the flow rate of powder as a change in capacitance, and in particular, the capacitance value of a measuring capacitance sensor that allows powder to pass through is as small as possible. At the same time, the present invention relates to a structure in which the electric field intensity distribution in the capacitance sensor can obtain a uniform intensity distribution and the connection between the AC oscillator and the amplifier.
粉体の量に応じた静電容量測定する為、対向する電極の間に粉体を通過させ、その通過する間に静電容量の変化を測定する粉体計測用静電容量計測装置は、より微小な粉体量の場合は測定電極の静電容量の変化分も微小になり、より高感度な粉体計測用静電容量計測装置が望まれている。 In order to measure the capacitance according to the amount of powder, the capacitance measuring device for powder measurement that allows the powder to pass between the opposing electrodes and measures the change in capacitance during the passage, In the case of a finer amount of powder, the amount of change in the capacitance of the measurement electrode becomes minute, and a more sensitive capacitance measuring device for powder measurement is desired.
粉体量の測定に用いられる静電容量センサーの容量値は０．数ｐＦ〜約１ｐＦのものが多い。これは静電容量電極の構成及び製作方法から得られている値である。微小な粉体をより高感度に行うとすると、その容量値の変化分は前記、静電容量センサーの容量値の１万分の１ないし１０万分の１の容量値を検出する必要がある。このような値を検出する為には、粉体量を計測する環境においても、静電容量センサーの容量値の安定度が必要になる事を意味する。しかしながら、粉体量を計測する環境は必ずしも良くなく、特に粉体を搬送するには主に空気が用いられていて、また、温度の安定な環境とはいえない。静電容量センサーを回りの環境から遮蔽して温度調節は可能であるが、その分コストが上昇するし、また、粉体を搬送する空気を遮蔽する事は不可能である。静電容量センサーの容量値の不安定要素は温度による金属電極の熱膨張と空気の比誘電率の変動によるものが考えられる。 The capacitance value of the capacitance sensor used for measuring the amount of powder is 0. Many are from a few pF to about 1 pF. This is a value obtained from the configuration and manufacturing method of the capacitance electrode. If a fine powder is to be performed with higher sensitivity, it is necessary to detect a capacitance value that is 1 / 10,000 to 1 / 100,000 of the capacitance value of the capacitance sensor. In order to detect such a value, it means that the capacitance value of the capacitance sensor needs to be stable even in an environment where the amount of powder is measured. However, the environment for measuring the amount of powder is not always good. In particular, air is mainly used for conveying powder, and it cannot be said that the environment is stable in temperature. Although it is possible to control the temperature by shielding the capacitance sensor from the surrounding environment, the cost increases accordingly, and it is impossible to shield the air carrying the powder. The unstable element of the capacitance value of the capacitance sensor may be due to the thermal expansion of the metal electrode due to temperature and the fluctuation of the relative dielectric constant of air.
静電容量センサーの容量値を仮に１ｐＦとすると、その１万分の１ないし１０万分の１の容量値は０．１〜０．０１ｆＦの容量値となる。このような容量変化を検出する為に静電容量センサーの容量値を１０ｆＦ程度の値に製作すると、その変化分は百分の１〜千分の１になり、環境条件の変化に対して大幅に改善される事になる。 Assuming that the capacitance value of the capacitance sensor is 1 pF, the capacitance value from 1 / 10,000 to 1 / 100,000 is a capacitance value of 0.1 to 0.01 fF. If the capacitance value of the capacitance sensor is manufactured to a value of about 10 fF in order to detect such a change in capacitance, the change will be 1 to 1 / 1,000th, which is greatly affected by changes in environmental conditions. Will be improved.
粉体量の測定に用いられる静電容量センサーは図４に示すような電極を螺旋状に形成されるものが多く用いられている。これは粉体がパイプの円筒軸の中心に対して偏って通過しても、螺旋電極の場合、粉体は必ず対向した電極の間を通過する事になり、粉体を必ず検出する。これは螺旋の周期が多いほど確実となる。また、一方の電極を半周期の間だけ螺旋を形成すると、もう一方の電極の螺旋を１８０度対向させると３６０度の範囲で必ず対向する電極を形成する事が出来る。しかしながら、このような構造では静電容量センサーの容量値を小さくする事が出来ない。また、螺旋の周期を小さくすれば、螺旋構造の意味がなくなるばかりでなく、電界強度を通過する粉体に対して一様にする事は極めて困難で不可能に近い。 As a capacitance sensor used for measuring the amount of powder, a sensor in which electrodes are spirally formed as shown in FIG. 4 is often used. This means that even if the powder passes with a deviation from the center of the cylindrical axis of the pipe, in the case of a spiral electrode, the powder always passes between the opposed electrodes, and the powder is always detected. This becomes more certain as the number of spiral cycles increases. Further, when one electrode is formed with a spiral only for a half period, the other electrode is made to face each other within a range of 360 degrees if the other electrode is turned 180 degrees. However, with such a structure, the capacitance value of the capacitance sensor cannot be reduced. Moreover, if the spiral period is reduced, not only does the meaning of the spiral structure disappear, but it is extremely difficult and impossible to make the powder uniform through the electric field strength.
静電容量センサーの電極構造を平行平面板コンデンサーの構造にして、静電容量センサー電極とガード電極に分離をする。これらの電極を粉体を通過させる円筒状パイプの筒方向の中心軸に対称に、また、円筒の中心点に対称に配置する構造とする。この電極の一方は静電容量センサー電極とガード電極は交流発振器に接続して、もう一方の電極は静電容量センサーの変化を電圧として検出する増幅機の入力に接続してガード電極は増幅機の出力に接続する。これにより、螺旋形状電極に比べて格段に小さい静電容量値に出来きる。さらに、曲線形状の螺旋形状電極に対して直線的な形状をしている為、その電極間の電界強度分布の相違を非常に小さく出来る構造が実現可能となる。 The capacitance sensor electrode structure is a parallel flat plate capacitor structure, and the capacitance sensor electrode and the guard electrode are separated. These electrodes are arranged symmetrically with respect to the central axis of the cylindrical pipe passing through the powder and symmetrically with respect to the central point of the cylinder. One of the electrodes is connected to an AC oscillator with the capacitance sensor electrode and the guard electrode, and the other electrode is connected to the input of an amplifier that detects the change of the capacitance sensor as a voltage. Connect to the output of. As a result, the capacitance value can be made much smaller than that of the spiral electrode. Further, since the shape is linear with respect to the curved spiral electrode, it is possible to realize a structure that can greatly reduce the difference in electric field intensity distribution between the electrodes.
この発明によれば、粉体量を計測する環境や粉体を搬送の空気の誘電率変化による影響を軽減する為、静電容量センサーの容量安定化のための温度調節器など新たに付加させる事がないので、その分のコストを上昇させる事なく、容量センサーの容量値の不安定原因である温度や湿度の環境変化の影響を受けないで粉体量を正確に測定できる。 According to the present invention, in order to reduce the influence of the environment for measuring the amount of powder and the change in dielectric constant of air for conveying the powder, a temperature controller for stabilizing the capacitance of the capacitance sensor is newly added. Since there is nothing, the amount of powder can be accurately measured without increasing the cost and without being affected by changes in the temperature and humidity environment that are the cause of instability of the capacitance value of the capacitance sensor.
図２に示す平面電極は静電容量センサー電極は横方向すなわち粉体が通過する円筒状パイプの直径方向と同じ程度の長さにして、縦方向すなわちパイプの長さ方向は出来る限り短い長さにする。本実施例では約１ｍｍである。平面電極は静電容量センサー電極の周囲をガード電極が形成されていて、パイプの横方向の端はある角度を持って対向する電極の方向に前記パイプ直径の２〜３割程度の長さを有している。これらの電極は通常電子回路に使用されているプリント基板で作成されている。図では電極のみを示しているがパイプの長さ方向には機械寸法的には余裕があり、ガード電極のパターンが無いところで対向する２枚の電極を固定する。図１に示すように、対向する電極の一方の静電容量センサー電極とガード電極は交流電源に接続して、もう一方の静電容量センサー電極は静電容量センサーに流れる電流を電圧に変換するインピーダンスＺ及び増幅器の入力に接続され、ガード電極は増幅器の出力に接続にされる。これらの静電容量センサー電極とガード電極はさらにシールドされていて、回路のアース電位に接続されている。この接続における等価回路を図５及び図６に示す。図６に示すＣ０が静電容量センサーの容量値となリガード電極の容量値は粉体が通過しても容量値変化に寄与しない。この関係を図６を参照して以下の計算式に示す。
から、上式を整理すると
となり、計算を簡単にする為、非反転増幅器の利得を１、オフセット電圧・電流を零と仮定して、ｅｏ＝ｅｉとすると上式は
となる。Ｃ２は増幅器の正帰還ループに組み込まれて、利得が１の為、電流が流れないのでインピーダンスが無い事と等価になる。この時の静電容量センサーの容量値Ｃ０は以下の定数を用いて、
ε０：真空の誘電率で約８．８５×１０−１２
εｒ：空気の比誘電率で約１。
ｄ ：横方向の電極の長さ（単位ｍｍ）
ｔ ：縦方向の電極の長さ（単位ｍｍ）
となり、約９ｆＦとなる。The planar electrode shown in FIG. 2 has the same length as that of the cylindrical pipe through which the capacitance sensor electrode passes in the horizontal direction, that is, the powder, and the vertical direction, that is, the length direction of the pipe is as short as possible. To. In this embodiment, it is about 1 mm. The planar electrode is formed with a guard electrode around the capacitance sensor electrode, and the lateral end of the pipe has a certain angle and is about 20-30% of the pipe diameter in the direction of the opposing electrode. Have. These electrodes are usually made of a printed circuit board used in an electronic circuit. Although only the electrodes are shown in the figure, there is a mechanical dimension in the length direction of the pipe, and two opposing electrodes are fixed where there is no guard electrode pattern. As shown in FIG. 1, one capacitance sensor electrode and the guard electrode of the opposing electrodes are connected to an AC power source, and the other capacitance sensor electrode converts a current flowing through the capacitance sensor into a voltage. Connected to the impedance Z and the input of the amplifier, the guard electrode is connected to the output of the amplifier. These capacitance sensor electrode and guard electrode are further shielded and connected to the ground potential of the circuit. An equivalent circuit in this connection is shown in FIGS. Capacitance values of the such Regard electrode of C 0 is the electrostatic capacitance sensor shown in FIG. 6 does not contribute to the capacitance value change with passage of the powder. This relationship is shown in the following calculation formula with reference to FIG.
From the above formula,
In order to simplify the calculation, assuming that the gain of the non-inverting amplifier is 1 and the offset voltage / current is zero, and e o = e i ,
It becomes. Since C 2 is incorporated in the positive feedback loop of the amplifier and the gain is 1, no current flows, which is equivalent to no impedance. The capacitance value C 0 of the capacitance sensor at this time is calculated using the following constants:
ε 0 : Dielectric constant of vacuum is about 8.85 × 10 −12
ε r : The relative dielectric constant of air is about 1.
d: Length of electrode in horizontal direction (unit: mm)
t: length of electrode in vertical direction (unit: mm)
And about 9 fF.
次にこれらの電極内部の電界強度分布を説明する。図７、図８は図２の静電容量センサーを横方向から見た場合の電界強度を示す。
図７の升目で最外周から５升目のところはアース電位にしており遮蔽されている事を前提に計算された図である。なお、電極に印加した電圧は＋１Ｖと−１Ｖである。
図８は電極部分の電界強度を拡大したものを示す。図中に電界強度の歪が見られるのは静電容量センサー電極とガード電極を分離したところであり、分離間隔は少ない方が電界強度の歪が少なく出来る事を示す。
しかしながら、円筒の長さ方向にガード電極を配置した効果で電極間の電位は相当に均一化される。図１１に電極間の電位分布の数値表示を示す。＋１Ｖの電極から−１Ｖの電極に架けて、電位が直線的に変化している事が分かる。
図９、図１０は上から下へと見た場合の電界強度を示す。この場合も上記同様に図９は升目で最外周から５升目のところはアース電位にしており遮蔽されている。
図１０は電極部分の電界強度を拡大したものを示す。
上から見た場合、ガード電極はある角度を持って対向する電極の方向に前記パイプ直径の２〜３割程度の長さを有している、いわゆるコの字状の形状をして、この形状により、電極内部の電界強度分布を相当に均一化される事が分かる。図１２に電極間の電位分布の数値表示を示す。Next, the electric field intensity distribution inside these electrodes will be described. 7 and 8 show the electric field strength when the capacitance sensor of FIG. 2 is viewed from the lateral direction.
In the grid of FIG. 7, the fifth grid from the outermost periphery is a ground potential and is calculated on the assumption that it is shielded. The voltages applied to the electrodes are + 1V and -1V.
FIG. 8 shows an enlarged electric field strength at the electrode portion. In the figure, the distortion of the electric field strength is seen when the capacitance sensor electrode and the guard electrode are separated, and the smaller the separation interval, the smaller the distortion of the electric field strength.
However, the potential between the electrodes is considerably uniformed by the effect of arranging the guard electrodes in the length direction of the cylinder. FIG. 11 shows a numerical display of the potential distribution between the electrodes. It can be seen that the potential changes linearly from the + 1V electrode to the -1V electrode.
9 and 10 show the electric field strength when viewed from the top to the bottom. Also in this case, as in the above case, FIG. 9 is a grid, and the fifth grid from the outermost periphery is grounded and shielded.
FIG. 10 shows an enlarged electric field strength of the electrode portion.
When viewed from above, the guard electrode has a so-called U-shaped shape having a length of about 20 to 30% of the pipe diameter in the direction of the electrode facing at an angle. It can be seen that the electric field strength distribution inside the electrode is made fairly uniform depending on the shape. FIG. 12 shows a numerical display of the potential distribution between the electrodes.
参考として、ガード電極と遮蔽が無く、周囲を無限空間とした場合の電界強度分布を図１３〜図１６に示す。
図１３は正方形の形状で２枚の電極を対向させた場合の電位分布を示す。図１４は電極間の電位を拡大したものである。電界強度の歪の程度が分かる。
図１５は、電極間距離は図１３と同じだが、電極の長さを３割程度の長さにした形状の場合の電位分布を示す。図１６は電極間の電位を拡大したものである。図１３に比べて、さらに、電界強度の歪が大きくなる事が分かる。For reference, FIG. 13 to FIG. 16 show electric field intensity distributions when there is no guard electrode and shielding and the surrounding is an infinite space.
FIG. 13 shows a potential distribution when two electrodes are opposed to each other in a square shape. FIG. 14 is an enlarged view of the potential between the electrodes. The degree of distortion of the electric field strength can be understood.
FIG. 15 shows the potential distribution in the case where the distance between the electrodes is the same as that in FIG. 13 but the electrode length is about 30%. FIG. 16 is an enlarged view of the potential between the electrodes. Compared to FIG. 13, it can be seen that the distortion of the electric field strength further increases.
１ ：第１平面板
２ ：第２平面板
３ａ、３ｂ ：静電容量センサー電極
４ａ、４ｂ ：ガード電極
５ａ、５ｂ ：Ｌ字状電極
６ａ、６ｂ ：Ｌ字状電極
１１ａ、１１ｂ ：円筒状パイプを通す穴
１２ ：円筒状パイプ
２０ ：交流電源
２１ ：増幅器1: 1st plane plate 2: 2nd plane plates 3a and 3b: Capacitance sensor electrodes 4a and 4b: Guard electrodes 5a and 5b: L-shaped electrodes 6a and 6b: L-shaped electrodes 11a and 11b: Cylindrical pipes Hole 12 for passing through: Cylindrical pipe 20: AC power supply 21: Amplifier
Claims (4)
静電容量センサー電極とガード電極を有する第１平面形状板及び静電容量センサー電極とガード電極を有する第２平面形状板からなり、前記第１平面形状板と第２平面形状板とが、各々、前記円筒状パイプの筒方向の中心軸に対称に配置された構成の粉体計測用静電容量センサー。In the capacitance sensor for powder measurement that measures the amount of powder by changing the capacitance between the electrodes by passing the powder of the measured object through the cylindrical pipe between the facing electrodes,
A first planar plate having a capacitance sensor electrode and a guard electrode, and a second planar plate having a capacitance sensor electrode and a guard electrode, wherein the first planar plate and the second planar plate are respectively The electrostatic capacity sensor for powder measurement of the composition arranged symmetrically about the central axis of the cylindrical direction of the cylindrical pipe.
前記第１平面形状板と第２平面形状板とが前記円筒状のパイプの軸方向にＬ字状の形状を有する構成からなる粉体計測用静電容量センサー。The electrostatic capacity sensor for powder measurement according to claim 1,
A capacitance measuring sensor for powder measurement, wherein the first planar plate and the second planar plate have an L-shape in the axial direction of the cylindrical pipe.
対向する一方の電極側はガード電極と静電容量センサー電極と共に交流発振器に接続し、もう一方の電極側の静電容量センサー電極は前記増幅器の入力に接続して、ガード電極は増幅器の出力に接続される構成の粉体計測用静電容量センサー。The electrostatic capacity sensor for powder measurement according to claim 1 or 2,
The opposite electrode side is connected to the AC oscillator together with the guard electrode and the capacitance sensor electrode, the capacitance sensor electrode on the other electrode side is connected to the input of the amplifier, and the guard electrode is connected to the output of the amplifier. Capacitance sensor for powder measurement configured to be connected.
前記第１平面形状板と第２平面形状板間に有する粉体を通過させる前記円筒状のパイプを除き、その全体をシールド電極で覆われて、アース電位に接続される構成の粉体計測用静電容量センサーIn the capacitance sensor for powder measurement that measures the amount of powder by changing the capacitance between the electrodes by passing the powder of the measured object through the cylindrical pipe between the facing electrodes,
For powder measurement having a configuration in which the cylindrical pipe that passes the powder between the first planar plate and the second planar plate is passed, except that the whole is covered with a shield electrode and connected to the ground potential. Capacitance sensor
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| JP2009068959A (en) * | 2007-09-12 | 2009-04-02 | Sinto Brator Co Ltd | Instrument for measuring mass flow rate of powder |
| JP2016138793A (en) * | 2015-01-27 | 2016-08-04 | 学校法人立命館 | Capacitance measurement system and sensor unit |
| JP2018047452A (en) * | 2016-09-19 | 2018-03-29 | パロ・アルト・リサーチ・センター・インコーポレーテッドＰａｌｏ Ａｌｔｏ Ｒｅｓｅａｒｃｈ Ｃｅｎｔｅｒ Ｉｎｃｏｒｐｏｒａｔｅｄ | System and method scalable real time micro object position control with the aid of digital computer |
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| JP2009068959A (en) * | 2007-09-12 | 2009-04-02 | Sinto Brator Co Ltd | Instrument for measuring mass flow rate of powder |
| JP4614997B2 (en) * | 2007-09-12 | 2011-01-19 | 新東工業株式会社 | Powder flow rate measuring device and measuring method thereof |
| US8061217B2 (en) | 2007-09-12 | 2011-11-22 | Sintokogio, Ltd. | Apparatus for measuring a flow rate of a powder |
| JP2016138793A (en) * | 2015-01-27 | 2016-08-04 | 学校法人立命館 | Capacitance measurement system and sensor unit |
| JP2018047452A (en) * | 2016-09-19 | 2018-03-29 | パロ・アルト・リサーチ・センター・インコーポレーテッドＰａｌｏ Ａｌｔｏ Ｒｅｓｅａｒｃｈ Ｃｅｎｔｅｒ Ｉｎｃｏｒｐｏｒａｔｅｄ | System and method scalable real time micro object position control with the aid of digital computer |
| JP7048027B2 (en) | 2016-09-19 | 2022-04-05 | パロ・アルト・リサーチ・センター・インコーポレーテッド | Systems and methods for scalable real-time micro-object position control with the assistance of digital computers |
| CN110057430A (en) * | 2018-01-18 | 2019-07-26 | 德国翰辉包装机械有限责任公司 | The monitoring sensor of amount of powder for dosage |
| CN110057430B (en) * | 2018-01-18 | 2021-11-16 | 德国翰辉包装机械有限责任公司 | Monitoring sensor for metered powder quantity |
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