JPH0814986A - Liquid level detecting device - Google Patents
Liquid level detecting deviceInfo
- Publication number
- JPH0814986A JPH0814986A JP16580294A JP16580294A JPH0814986A JP H0814986 A JPH0814986 A JP H0814986A JP 16580294 A JP16580294 A JP 16580294A JP 16580294 A JP16580294 A JP 16580294A JP H0814986 A JPH0814986 A JP H0814986A
- Authority
- JP
- Japan
- Prior art keywords
- liquid
- liquid level
- electrode
- detecting device
- piezoelectric substrate
- 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.)
- Pending
Links
- 239000007788 liquid Substances 0.000 title claims abstract description 51
- 239000000758 substrate Substances 0.000 claims abstract description 21
- 238000010897 surface acoustic wave method Methods 0.000 claims description 13
- 238000001514 detection method Methods 0.000 claims description 11
- 230000001681 protective effect Effects 0.000 claims description 5
- 238000006073 displacement reaction Methods 0.000 description 9
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 4
- 239000010408 film Substances 0.000 description 4
- 229910052782 aluminium Inorganic materials 0.000 description 3
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 3
- 239000013078 crystal Substances 0.000 description 2
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 description 2
- 229910052737 gold Inorganic materials 0.000 description 2
- 239000010931 gold Substances 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 235000012239 silicon dioxide Nutrition 0.000 description 2
- 239000000377 silicon dioxide Substances 0.000 description 2
- 238000010586 diagram Methods 0.000 description 1
- 239000007772 electrode material Substances 0.000 description 1
- 239000012530 fluid Substances 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 238000000034 method Methods 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 230000005624 perturbation theories Effects 0.000 description 1
- 238000000206 photolithography Methods 0.000 description 1
- 230000001902 propagating effect Effects 0.000 description 1
- 238000004544 sputter deposition Methods 0.000 description 1
- 239000010409 thin film Substances 0.000 description 1
- 238000007738 vacuum evaporation Methods 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
Landscapes
- Measurement Of Levels Of Liquids Or Fluent Solid Materials (AREA)
Abstract
Description
【０００１】[0001]
【産業上の利用分野】この発明は液体レベルの検知装置
に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid level detecting device.
【０００２】[0002]
【従来の技術】従来、液体レベルの検知はフロートによ
り液面高さを検出し、それを抵抗変化やインダクタンス
変化により検出するものや、投げ込み式の水位計のよう
に圧力により液面レベルを検出するものなどがある。さ
らにまた、液体の誘電率を利用した静電容量による液面
検知などがある。2. Description of the Related Art Conventionally, a liquid level is detected by detecting a liquid level by a float and detecting the liquid level by a resistance change or an inductance change, or by detecting a liquid level by a pressure such as a throw-in type water level gauge. There are things to do. Furthermore, there is a liquid level detection by capacitance using the dielectric constant of liquid.
【０００３】[0003]
【発明が解決しようとする課題】従来のフロートによる
液面レベルの検知ではフロートがスムースに上下するた
めの機構が必要であり、液面レベルを高精度に検知する
ためにはフロートの上下による微少変位を精度良く測定
する必要がある。フロートの上下による変位を抵抗変化
で取り出す場合には、フロートの直線変位を直接、抵抗
変化に変換するだけでは充分な精度（分解能）が得られ
ず、精度を上げるためにはテコの原理による変位拡大機
構が必要となり、検出部の大きさが大きくなってしまう
という問題があった。また、差動トランスなどによりフ
ロートの微小変位の高精度検出が可能であるが、液面レ
ベルに対する出力信号の直線性が得られないという問題
があった。静電容量式においてはタンク壁面と検出電極
間の静電容量変化により液面レベルを検出するが、この
方式においても液面レベルと静電容量との関係は単純な
比例関係になく、事前の校正が必要であった。本発明の
目的は高精度で分解能が高く、直線性の良い液体レベル
検知装置を提供することにある。In the conventional detection of a liquid level by a float, a mechanism for smoothly moving the float up and down is required. It is necessary to measure displacement accurately. When the displacement due to the vertical movement of the float is taken out by the resistance change, it is not possible to obtain sufficient accuracy (resolution) simply by converting the linear displacement of the float directly into the resistance change. There is a problem that an enlargement mechanism is required, and the size of the detection unit becomes large. Further, although a minute displacement of the float can be detected with high accuracy by a differential transformer or the like, there is a problem that the linearity of the output signal with respect to the liquid level cannot be obtained. In the capacitance type, the liquid level is detected by a change in capacitance between the tank wall surface and the detection electrode.In this method, however, the relationship between the liquid level and the capacitance is not a simple proportional relation, and is determined in advance. Calibration was required. An object of the present invention is to provide a liquid level detecting device with high accuracy, high resolution, and good linearity.
【０００４】[0004]
【課題を解決するための手段】本発明は前記課題を解決
すべくなされたもので、実施例に対応する図１で説明す
ると、本発明による液体レベル検知装置は、圧電基板１
上に所定の距離Ｌを隔てて配置された入力用電極２と出
力用電極３とを有する検出部１０と、その入力用電極２
と出力用電極３との間に被測定液体４を接触させ、ネッ
トワークアナライザ５などの弾性表面波の伝搬ロス計測
手段とにより液体のレベルを検出することを特徴とす
る。SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and will be described with reference to FIG. 1 corresponding to the embodiment.
A detection unit 10 having an input electrode 2 and an output electrode 3 arranged at a predetermined distance L above the input electrode 2
The liquid to be measured 4 is brought into contact between the electrode 4 and the output electrode 3, and the level of the liquid is detected by means of a surface acoustic wave propagation loss measuring means such as a network analyzer 5.
【０００５】[0005]
【作用】本発明による液体レベル検知装置では入力電極
２に高周波の交流電圧を印加すると圧電基板１上に弾性
表面波が発生する。圧電基板１の結晶方位を適当に選ぶ
と発生する弾性表面波の種類が変わり、ＳＨ（Shear Ho
rizontal）モードの表面波を励振することができる。代
表的なものとして３６°ＹＸ回転−ＬｉＴａＯ3基板の
Ｘ方向伝搬がある。このＳＨモードの表面波は圧電基板
表面の垂直方向（図１中のＸ2 方向）への振動変位が小
さく、水平方向（図１中のＸ3 方向）への振動変位が大
きいという特徴を有している。ＳＨモードの表面波の伝
搬路に液体を負荷すると、基板表面の垂直方向の振動変
位が小さいために弾性表面波エネルギーの液体中への散
逸が少ないが、一方で基板表面の水平方向の振動変位が
大きいために負荷された液体の粘性により弾性表面波エ
ネルギーが液体中に放出される。ＳＨモードの弾性表面
波の伝搬は液体の負荷による伝搬ロスの変化は摂動理論
より以下のように導かれる。圧電基板表面に粘性流体が
負荷された場合の単位長さ当たりの伝搬ロスＩＬ〔dB／
mm〕は次式のようになる。In the liquid level detecting device according to the present invention, when a high frequency AC voltage is applied to the input electrode 2, a surface acoustic wave is generated on the piezoelectric substrate 1. When the crystal orientation of the piezoelectric substrate 1 is appropriately selected, the type of surface acoustic wave generated changes, and the SH (Shear Ho
rizontal) mode surface waves can be excited. A typical example is a 36 ° YX rotation—propagation in the X direction of a LiTaO 3 substrate. The surface wave of SH modes small vibration displacement in the vertical direction of the piezoelectric substrate surface (X 2 direction in FIG. 1), have the characteristic that the vibration displacement in the horizontal direction (X 3 direction in FIG. 1) is greater doing. When a liquid is loaded on the propagation path of the surface acoustic wave in the SH mode, the surface vibration energy of the substrate surface is small because the vertical vibration displacement is small. , The surface acoustic wave energy is released into the liquid due to the viscosity of the loaded liquid. In the propagation of the SH mode surface acoustic wave, the change in the propagation loss due to the liquid load is derived as follows from the perturbation theory. Propagation loss per unit length IL [dB / dB] when a viscous fluid is loaded on the piezoelectric substrate surface
mm] is as follows.
【０００６】 ＩＬ＝２０ log exp〔１／４Ｐ｛（ρωη／２）1/2 ・（ｖ1 2＋ｖ2 2）＋ηｖ s ( κ／（ρｖs 2 −κ））1/2 ・ｖ3 2｝〕 (1)IL = 20 log exp [logP 〔(ρωη / 2)1/2・ (V1 Two+ VTwo Two) + Ηv s (κ / (ρvs Two−κ))1/2・ VThree Two｝] (1)
【０００７】ここで Ｐ：単位長さ当たりのパワーフ
ロー密度 ρ：液体の密度 η：液体の粘度 ｖ1 、ｖ2 、ｖ3 ：粒子速度成分 ｖs : 表面波の伝搬速度 κ：液体の体積弾性率 ω：角速度 Ｐ、ｖ1 、ｖ2 、ｖ3 、ｖs は材料固有の値であり、κ
は液体中の音速ｖ1 からκ＝ｖ1 2・ρより求まるので、
負荷する液体の密度、粘度がわかれば、（１）式からＩ
Ｌが求められる。この伝搬ロスＩＬは表面波伝搬路の単
位長さ当たりの値であるので、伝搬路Ｌ中で液体を負荷
した距離ｌに比例した伝搬ロスを出力として取り出すこ
とができる。Here, P: power flow density per unit length ρ: density of liquid η: viscosity of liquid v 1 , v 2 , v 3 : particle velocity component v s : surface wave propagation velocity κ: liquid volume modulus omega: angular velocity P, v 1, v 2, v 3, v s is the material-specific values, kappa
Is obtained from the sound velocity v 1 in the liquid from κ = v 1 2 · ρ.
If the density and viscosity of the liquid to be loaded are known, from equation (1), I
L is required. Since this propagation loss IL is a value per unit length of the surface acoustic wave propagation path, a propagation loss proportional to the distance l of the propagation path L loaded with the liquid can be taken out as an output.
【０００８】[0008]
【実施例】以下、図面に示す実施例についてさらに詳細
に説明する。図１は本発明による液体レベル検出装置の
一実施例の説明図である。圧電基板１上に所定の距離Ｌ
を隔てて入力用電極２と出力用電極３とを設けた検出部
１０の入力用電極２と出力用電極３の間に被測定液体４
を接触させ、入力用電極２、出力用電極３それぞれを弾
性表面波の伝搬ロス計測手段であるネットワークアナラ
イザ５の入出力に接続する。図２と図３は検出部１０に
ついて詳細に説明したものである。圧電基板１には３６
°ＹＸ回転−ＬｉＴａＯ3 基板を用い、伝搬方向がＸ方
向になるように、また検知したい液体のレベルに合わせ
て所定の間隔Ｌを隔てて入力用電極２、出力用電極３を
配置する。入力用電極２、出力用電極３ともすだれ状電
極（Interdigital Transducer)と呼ばれる構造のもの
で、その電極対のピッチλにより圧電基板１上を伝搬す
る弾性表面波の共振周波数が決まる。DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments shown in the drawings will be described below in more detail. FIG. 1 is an explanatory diagram of one embodiment of a liquid level detecting device according to the present invention. A predetermined distance L on the piezoelectric substrate 1
The liquid 4 to be measured is provided between the input electrode 2 and the output electrode 3 of the detection unit 10 provided with the input electrode 2 and the output electrode 3
And the input electrode 2 and the output electrode 3 are connected to the input and output of a network analyzer 5 which is a means for measuring the propagation loss of the surface acoustic wave. 2 and 3 illustrate the detecting unit 10 in detail. 36 on the piezoelectric substrate 1
The input electrode 2 and the output electrode 3 are arranged at a predetermined interval L so that the propagation direction is in the X direction, and in accordance with the level of the liquid to be detected, using a YY rotation-LiTaO 3 substrate. Both the input electrode 2 and the output electrode 3 have a structure called an interdigital transducer (Interdigital Transducer), and the resonance frequency of the surface acoustic wave propagating on the piezoelectric substrate 1 is determined by the pitch λ of the electrode pair.
【０００９】入力用電極２、出力用電極３は圧電基板１
上に真空蒸着やスパッタリングによりアルミニウム、金
などの金属薄膜を形成し、フォトリソグラフィーにより
形成される。ネットワークアナライザ５より出力された
高周波信号は３６°ＹＸ回転−ＬｉＴａＯ3 基板のよう
な圧電基板１上に設けられた入力用電極２で高周波信号
はＳＨモードの弾性表面波振動に変換され、伝搬路をｘ
1 方向に向かって伝搬し、出力用電極３において再び高
周波信号に変換される。The input electrode 2 and the output electrode 3 are the piezoelectric substrate 1
A metal thin film of aluminum, gold, or the like is formed thereon by vacuum evaporation or sputtering, and is formed by photolithography. The high-frequency signal output from the network analyzer 5 is converted into SH-mode surface acoustic wave vibration by an input electrode 2 provided on a piezoelectric substrate 1 such as a 36 ° YX rotation-LiTaO 3 substrate, and the propagation path X
The light propagates in one direction, and is converted again into a high-frequency signal at the output electrode 3.
【００１０】ＳＨモードの表面波は圧電基板表面の垂直
方向（図３中のＸ2 方向）への振動変位が小さく、水平
方向（図２中のＸ3 方向）への振動変位が大きいため、
伝搬中に粘性を持った液体と接触すると表面波エネルギ
ーが液体中に失われる。この失われるエネルギーは弾性
表面波の伝搬路中で液体が接触している長さに比例する
ので図１で示したようにネットワークアナライザ５のよ
うな計測手段により高周波信号の伝搬ロスを計測するこ
とにより、表面波の伝搬路長Ｌ中において液体との接触
長さｌを検知することができる。[0010] surface waves SH mode vibration displacement in the vertical direction of the piezoelectric substrate surface (X 2 direction in FIG. 3) is small, since the vibration displacement in the horizontal direction (X 3 direction in FIG. 2) is large,
If it comes into contact with a viscous liquid during propagation, surface wave energy is lost in the liquid. Since this lost energy is proportional to the length of contact of the liquid in the surface acoustic wave propagation path, the propagation loss of the high-frequency signal must be measured by a measuring means such as the network analyzer 5 as shown in FIG. Accordingly, the contact length 1 with the liquid can be detected in the propagation path length L of the surface wave.
【００１１】図４は本発明による液体レベル検知装置の
液面レベルｌとネットワークアナライザ５により測定さ
れる伝搬ロスとの関係を示したものである。液面レベル
がゼロの時でもＩＬ0 の伝搬ロスがあるが、液面レベル
ｌと伝搬ロスＩＬは比例関係になる。FIG. 4 shows the relationship between the liquid level 1 of the liquid level detecting device according to the present invention and the propagation loss measured by the network analyzer 5. Although the liquid level there is a propagation loss of IL 0 even when the zero propagation loss IL with liquid level l is proportional.
【００１２】図５は検出部１０の表面を保護膜６で覆っ
たものについての説明図である。入力用電極２、出力用
電極３は通常、金やアルミニウムなどの材料を用いて形
成されるが、電極材料としてアルミニウムを用いた場合
には被測定液体により、腐食される場合もあるので、レ
ジストや二酸化シリコンなどによる保護膜６を薄く（１
ミクロン以下）形成しておくと良い。FIG. 5 is an explanatory view of the detection unit 10 whose surface is covered with a protective film 6. The input electrode 2 and the output electrode 3 are usually formed using a material such as gold or aluminum. However, if aluminum is used as the electrode material, the electrode 2 may be corroded by the liquid to be measured. Protective film 6 of silicon dioxide or silicon dioxide (1
Micron or less).
【００１３】本発明の実施例では圧電基板に３６°ＹＸ
回転−ＬｉＴａＯ3 基板を用いた場合について説明した
が、ＳＨモードの弾性表面波を発生するものとして、Ｓ
Ｔカット水晶、３６°あるいは４１°ＹＸ回転−ＬｉＮ
ｂＯ3 などが使用可能である。In the embodiment of the present invention, the piezoelectric substrate is 36 ° YX
The case where the rotation-LiTaO 3 substrate is used has been described, but it is assumed that an SH mode surface acoustic wave is generated.
T-cut crystal, 36 ° or 41 ° YX rotation-LiN
bO 3 or the like can be used.
【００１４】[0014]
【発明の効果】本発明による液体レベル検知装置ではフ
ロート式と比較して可動部が無いため、信頼性が高い。
さらに液面レベルに対する出力変化が線形であるため直
線性が良く、静電容量式のような面倒な校正が不要であ
る。また表面に薄い保護膜を形成することにより電極を
保護することにより、腐食性液体のレベル検知も可能で
ある。As described above, the liquid level detecting device according to the present invention has high reliability because it has no movable parts as compared with the float type.
Further, since the output change with respect to the liquid level is linear, the linearity is good, and troublesome calibration such as a capacitance type is unnecessary. Further, by protecting the electrodes by forming a thin protective film on the surface, it is possible to detect the level of the corrosive liquid.
【図１】本発明による実施例を示す斜視図である。FIG. 1 is a perspective view showing an embodiment according to the present invention.
【図２】本発明による実施例の検知部の平面図である。FIG. 2 is a plan view of a detection unit according to the embodiment of the present invention.
【図３】本発明による実施例の検知部の断面図である。FIG. 3 is a sectional view of a detection unit according to the embodiment of the present invention.
【図４】本発明による実施例による出力特性のグラフ図
である。FIG. 4 is a graph showing output characteristics according to an embodiment of the present invention.
【図５】本発明による実施例の検知部の断面図である。FIG. 5 is a cross-sectional view of a detection unit according to an embodiment of the present invention.
１ 圧電基板 ２ 入力用電極 ３ 出力用電極 ４ 被測定液体 ５ ネットワークアナライザ ６ 保護膜 １０ 検出部 DESCRIPTION OF SYMBOLS 1 Piezoelectric substrate 2 Input electrode 3 Output electrode 4 Liquid to be measured 5 Network analyzer 6 Protective film 10 Detector
Claims (2)
れた入力用電極と出力用電極とを有し、その入力用電極
と出力用電極との間に被測定液体を接触させる検出部
と、弾性表面波の伝搬ロス計測手段とにより液体のレベ
ルを検出することを特徴とする装置。1. A detection unit having an input electrode and an output electrode arranged at a predetermined distance on a piezoelectric substrate, and bringing a liquid to be measured into contact between the input electrode and the output electrode. And an apparatus for detecting the level of the liquid by means of a surface acoustic wave propagation loss measuring means.
とする請求項１に記載の液体レベル検出装置。2. The liquid level detecting device according to claim 1, wherein a surface of the detecting section is covered with a protective film.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP16580294A JPH0814986A (en) | 1994-06-27 | 1994-06-27 | Liquid level detecting device |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP16580294A JPH0814986A (en) | 1994-06-27 | 1994-06-27 | Liquid level detecting device |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH0814986A true JPH0814986A (en) | 1996-01-19 |
Family
ID=15819277
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP16580294A Pending JPH0814986A (en) | 1994-06-27 | 1994-06-27 | Liquid level detecting device |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH0814986A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2007292626A (en) * | 2006-04-26 | 2007-11-08 | Epson Toyocom Corp | Liquid level detector |
| WO2025219473A1 (en) * | 2024-04-18 | 2025-10-23 | Leibniz-Institut Für Festkörper- Und Werkstoffforschung Dresden E.V. | Sensor for container interiors |
-
1994
- 1994-06-27 JP JP16580294A patent/JPH0814986A/en active Pending
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2007292626A (en) * | 2006-04-26 | 2007-11-08 | Epson Toyocom Corp | Liquid level detector |
| WO2025219473A1 (en) * | 2024-04-18 | 2025-10-23 | Leibniz-Institut Für Festkörper- Und Werkstoffforschung Dresden E.V. | Sensor for container interiors |
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