JPH0830709B2 - Flow velocity sensor - Google Patents
Flow velocity sensorInfo
- Publication number
- JPH0830709B2 JPH0830709B2 JP2268497A JP26849790A JPH0830709B2 JP H0830709 B2 JPH0830709 B2 JP H0830709B2 JP 2268497 A JP2268497 A JP 2268497A JP 26849790 A JP26849790 A JP 26849790A JP H0830709 B2 JPH0830709 B2 JP H0830709B2
- Authority
- JP
- Japan
- Prior art keywords
- flow velocity
- temperature
- velocity sensor
- temperature measuring
- measuring resistance
- 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 - Fee Related
Links
Landscapes
- Measuring Volume Flow (AREA)
Description
【発明の詳細な説明】 ［産業上の利用分野］ 本発明は、気体の流速を測定する流速センサに係わ
り、特にダイアフラム構造の流速センサに関するもので
ある。TECHNICAL FIELD The present invention relates to a flow velocity sensor for measuring the flow velocity of gas, and more particularly to a flow velocity sensor having a diaphragm structure.
［従来の技術］ 一般に気体の流速測定には、各種の構造の流速センサ
が提案されており、その１つとして例えば特開昭60-142
268号公報には、半導体製造技術を用いて制作された熱
式流速センサが提案されている。この熱式流速センサ
は、第５図に要部拡大平面図で示すように半導体基板１
にこの半導体基板１と熱的に絶縁する空隙部２を介して
薄膜状のブリッジ部３が形成されており、このブリッジ
部３上の表面中央部にはヒータエレメント４およびこの
ヒータエレメント４の両側に熱感知用の測温抵抗エレメ
ント5,6が形成されて構成されている。なお、７は空隙
部２に連通された開口である。[Prior Art] Generally, flow velocity sensors of various structures have been proposed for measuring the flow velocity of gas, and one of them is disclosed in, for example, Japanese Patent Laid-Open No. 60-142.
Japanese Patent No. 268 proposes a thermal type flow velocity sensor manufactured using semiconductor manufacturing technology. This thermal type flow velocity sensor is used in the semiconductor substrate 1 as shown in FIG.
A thin film-shaped bridge portion 3 is formed through a void portion 2 that is thermally insulated from the semiconductor substrate 1, and a heater element 4 and both sides of the heater element 4 are formed in the center portion of the surface on the bridge portion 3. The temperature-measuring resistance elements 5 and 6 for heat detection are formed in the structure. In addition, 7 is an opening communicating with the void 2.
このように構成される流速センサは、ヒータエレメン
ト４に電流を流して加熱し、気体の流れの中に置いたと
きに矢印方向８から気体が移動すると、上流側の測温抵
抗エレメント５は気体の流れよって冷却されて降温し、
一方、下流側の測温抵抗エレメント６は温度が上昇す
る。この結果、上流側の測温抵抗エレメント５と下流側
の測温抵抗エレメント６との間に温度差が生じ、抵抗値
が変化する。このため、上流側の測温抵抗エレメント５
と下流側の測温抵抗エレメント６とをホイートストンブ
リッジ回路に組み込み、その抵抗値の変化を電圧に変換
することにより、気体の流速に応じた電圧出力が得ら
れ、その結果、気体の流速を検出することができる。The flow velocity sensor configured in this way heats the heater element 4 by applying an electric current, and when the gas is moved from the direction of the arrow 8 when placed in the gas flow, the temperature measuring resistance element 5 on the upstream side is gas Is cooled by the flow of
On the other hand, the temperature of the temperature measuring resistance element 6 on the downstream side rises. As a result, a temperature difference occurs between the temperature measuring resistance element 5 on the upstream side and the temperature measuring resistance element 6 on the downstream side, and the resistance value changes. Therefore, the temperature measuring resistance element 5 on the upstream side
By incorporating the temperature measurement resistance element 6 on the downstream side into a Wheatstone bridge circuit and converting the change in the resistance value into a voltage, a voltage output corresponding to the gas flow velocity is obtained, and as a result, the gas flow velocity is detected. can do.
［発明が解決しようとする課題］ しかしながら、従来の流速センサにおいて、ヒータエ
レメント４の両側に配置された測温抵抗エレメント5,6
はその全体形状がヒータエレメント４とほぼ同等の矩形
状を有して形状されているので、矢印方向８からの例え
ば秒速2cm程度の低流速の気体の流れに対して発生した
ヒータエレメント４を中心とする円弧状の温度分布状態
の変化を効果的に検出できないという問題があった。[Problem to be Solved by the Invention] However, in the conventional flow velocity sensor, the temperature measuring resistance elements 5 and 6 arranged on both sides of the heater element 4 are provided.
Has a rectangular shape which is almost the same as that of the heater element 4, so that the heater element 4 which is generated in response to a low-velocity gas flow of, for example, about 2 cm / sec from the arrow direction 8 is centered. There is a problem that the change in the arc-shaped temperature distribution state cannot be effectively detected.
［課題を解決するための手段］ このような課題を解決するために本発明による流速セ
ンサは、発熱体部を構成する抵抗体パターンの長さ方向
端部の抵抗値を抵抗体パターン中央部よりも大きくした
ものである。[Means for Solving the Problem] In order to solve such a problem, in the flow velocity sensor according to the present invention, the resistance value at the end portion in the length direction of the resistor pattern forming the heating element is determined from the central portion of the resistor pattern. Is also enlarged.
また、本願発明による他の流速センサは、抵抗体パタ
ーンの長さ方向端部を測温抵抗体に近接配置したもので
ある。Further, in another flow velocity sensor according to the present invention, the end portion in the length direction of the resistor pattern is arranged close to the resistance temperature detector.
［作用］ 本発明による流速センサにおいては、ダイアフラム部
に形成された発熱体両側の温度分布状態が発熱パターン
の長さ方向にほぼ平行に形成される。[Operation] In the flow velocity sensor according to the present invention, the temperature distribution on both sides of the heating element formed in the diaphragm portion is formed substantially parallel to the lengthwise direction of the heating pattern.
［実施例］ 以下、図面を用いて本発明の実施例を詳細に説明す
る。Embodiments Embodiments of the present invention will be described in detail below with reference to the drawings.
第１図は本発明による流速センサの一実施例による概
略構成を説明する平面図であり、前述の図と同一または
相当部分には同一符号を付してその説明は省略する。同
図において、半導体基板１の表面中央部分には、この半
導体基板１に対して空隙部２を介して熱的に絶縁された
薄肉状のダイアフラム部3aが形成されており、このダイ
アフラム部3aの中央部分には、ヒータエレメント4aが形
成され、さらにこのヒータエレメント4aの両側にはそれ
ぞれ独立した測温抵抗エレメント5,6が形成されてい
る。また、この半導体基板１上の表面には、この半導体
基板１のエッチングのための多数のスリット11が開設さ
れ、ヒータエレメント4aおよび測温抵抗エレメント5,6
の周辺部を、その半導体基板１の表面に開設された多数
の細かいスリット11を介して例えば異方性エッチングを
行うことにより、内側に逆台形状の空気スペースを有す
る空隙部２が形成されている。これによってこの空隙部
２の上部には、半導体基板１からダイアフラム状に空間
的に隔離され、この半導体基板１からヒータエレメント
4aおよび両側の測温抵抗エレメント5,6が熱的に絶縁さ
れて支持されたダイアフラム部3aが形成される構造とな
っている。なお、111,112,113,114,115はダイアフラム
部3aにおいて、風上側から風下側に向かって各測温抵抗
エレメント5,ヒータエレメント4a,測温抵抗エレメント
６の配列前後に空隙部２と連通して連続的に開設された
スリット部である。そして、ダイアフラム部3aの上流側
測温抵抗エレメント５と下流側測温抵抗エレメント６と
の間に配置されたヒータエレメント4aは、第２図に要部
拡大平面図で示すようにその抵抗体パターンの中央部で
は直線状に形成され、長手方向端部では複数回折り返さ
れて形成されるパターン形状を有して形成されている。
また、このダイアフラム部3aに設けられた上流側測温抵
抗エレメント５および下流側測温抵抗エレメント６は、
気体の流れる矢印方向８と交差する長手方向の抵抗体パ
ターンが風上側から風下方向に向かってほぼ等間隔で配
置して形成されおり、全体の外形形状がいずれも矩形状
を有し、ヒータエレメント4aを中心として左右対称に配
置されている。FIG. 1 is a plan view for explaining a schematic configuration according to an embodiment of a flow velocity sensor according to the present invention. The same or corresponding parts as those in the above-mentioned drawings are designated by the same reference numerals and the description thereof will be omitted. In the figure, a thin-walled diaphragm portion 3a, which is thermally insulated from the semiconductor substrate 1 via a void portion 2, is formed in the central portion of the surface of the semiconductor substrate 1. A heater element 4a is formed in the central portion, and independent temperature measuring resistance elements 5 and 6 are formed on both sides of the heater element 4a. A large number of slits 11 for etching the semiconductor substrate 1 are formed on the surface of the semiconductor substrate 1, and the heater element 4a and the temperature measuring resistance elements 5 and 6 are formed.
By performing anisotropic etching, for example, on the peripheral portion of the semiconductor substrate 1 through a large number of fine slits 11 formed on the surface of the semiconductor substrate 1, a void portion 2 having an inverted trapezoidal air space is formed inside. There is. As a result, the upper portion of the void 2 is spatially separated from the semiconductor substrate 1 in a diaphragm shape, and the semiconductor element 1 is separated from the heater element.
4a and the temperature measuring resistance elements 5 and 6 on both sides are thermally insulated and supported to form a diaphragm portion 3a. In addition, 11 1 , 11 2 , 11, 3 , 11, 4 and 11 5 are arranged in the diaphragm part 3a from the windward side to the leeward side before and after the arrangement of each of the temperature measuring resistance element 5, the heater element 4a, and the temperature measuring resistance element 6. It is a slit portion which is communicated with the void portion 2 and is continuously opened. The heater element 4a disposed between the upstream side temperature measuring resistance element 5 and the downstream side temperature measuring resistance element 6 of the diaphragm portion 3a has its resistor pattern as shown in FIG. Is formed in a straight line at the central portion and has a pattern shape formed by being folded back a plurality of times at the end portion in the longitudinal direction.
Further, the upstream side temperature measuring resistance element 5 and the downstream side temperature measuring resistance element 6 provided in the diaphragm portion 3a are
Resistor patterns in the longitudinal direction intersecting with the direction 8 in which the gas flows are formed at substantially equal intervals from the windward side to the leeward direction, and the entire outer shape has a rectangular shape. They are arranged symmetrically around 4a.
このような構成によると、上流側の測温抵抗エレメン
ト５および下流側の測温抵抗エレメント６がそれぞれ全
体形状が矩形状に形成され、各上流側測温抵抗エレメン
ト５と下流側測温抵抗エレメント６との間に、長手方向
両端部が複数回折り返して形成されたＩ字状のヒータエ
レメント4aを配置したことにより、ヒータエレメント4a
の両端側で中央部よりも抵抗値が大きくなることによっ
て発熱量が増大し、第３図（ａ）に示すようにヒータエ
レメント4aの抵抗体パターンに平行となる矩形状の温度
分布P1が得られる。つまり従来のヒータエレメント４で
は、その形状が第３図（ｂ）に示すようにほぼ直線状を
有していたので、その両端側の発熱量の一部が半導体基
板１の厚肉部に近接していることから、吸熱され易くな
り、第３図（ｂ）に示すような湾曲状の温度分布P2とな
る。したがって第３図（ａ）に示すようなうにヒータエ
レメント4aの抵抗体パターン長とほぼ平行となる矩形状
の温度分布P1が得られることにより、矢印方向８からの
気体の流れに対して両側の測温抵抗エレメント5,6に温
度が高い部分と低い部分との差が少なくなり、ダイアフ
ラム部3a上において均一な温度分布が形成されることに
なる。したがって温度変化の小さい低流速域において温
度変化を効率良く検出できるため、検出感度を向上させ
ることができる。また、温度の高い部分における測温抵
抗エレメント5,6の初期温度が低く抑えられ、ダストの
付着による検出誤差および測温抵抗エレメント5,6間のT
CRミスマッチドリフトによる出力誤差の発生などがなく
なる。また、ヒータエレメント4aのダイアフラム部3a上
に形成される温度分布が均一となるので、測温抵抗エレ
メント5,6の全体形状を温度分布に対応した半円状もし
くは台形状に形成する必要がなくなり、所定の抵抗値が
得られ易い、つまり抵抗値の設定が容易でかつシンプル
な矩形状で高感度の流速検出が可能となる。さらに第１
図に示すようにヒータエレメント4aと周囲測温抵抗エレ
メント９のコモンとを半導体基板１上で共通接続し、１
個の電極端子として構成することにより、流速センサか
ら取り出される配線リードを１本減らすことができる。
また、第１図に示すヒータエレメント4aの中央部にスリ
ット部113を設けたり、もしくは間隔を広げたりするこ
とにより、ヒータエレメント4aを上流側と下流側とに均
等に２分割することによって気体の流れによるヒータエ
レメント4aの上流部分と下流部分とで温度差が大きくな
り、これに伴って上流側測温抵抗エレメント５と下流側
測温抵抗エレメント６との温度差が大きくなり、流速検
出の感度向上効果が得られる。また、ヒータエレメント
4aの温度を低くしてもノーマルヒータとほぼ同等の感度
が得られるので、ヒータエレメント4aの寿命を長くする
ことができる。According to such a configuration, the upstream temperature measuring resistance element 5 and the downstream temperature measuring resistance element 6 are each formed in a rectangular shape as a whole, and the upstream temperature measuring resistance element 5 and the downstream temperature measuring resistance element 5 are formed. By disposing an I-shaped heater element 4a formed by bending back both ends in the longitudinal direction between the heater element 4 and 6,
As the resistance value becomes larger on both end sides than the central part, the amount of heat generation increases, and as shown in FIG. 3 (a), a rectangular temperature distribution P 1 parallel to the resistor pattern of the heater element 4a can get. That is, since the heater element 4 of the related art has a substantially linear shape as shown in FIG. 3 (b), a part of the heat generation amount on both ends of the heater element 4 is close to the thick portion of the semiconductor substrate 1. As a result, heat is easily absorbed, and a curved temperature distribution P 2 as shown in FIG. 3B is obtained. Therefore, as shown in FIG. 3 (a), a rectangular temperature distribution P 1 that is substantially parallel to the resistor pattern length of the heater element 4a is obtained. The difference between the high temperature portion and the low temperature portion of the temperature measuring resistance elements 5 and 6 is reduced, and a uniform temperature distribution is formed on the diaphragm portion 3a. Therefore, since the temperature change can be detected efficiently in the low flow velocity region where the temperature change is small, the detection sensitivity can be improved. In addition, the initial temperature of the resistance temperature detector elements 5 and 6 in the high temperature part is kept low, and the detection error due to dust adhesion and the T
Output error will not occur due to CR mismatch drift. Further, since the temperature distribution formed on the diaphragm portion 3a of the heater element 4a becomes uniform, it is not necessary to form the entire temperature measuring resistance element 5, 6 into a semicircular shape or a trapezoidal shape corresponding to the temperature distribution. The predetermined resistance value can be easily obtained, that is, the resistance value can be easily set and the flow rate can be detected with a simple rectangular shape and high sensitivity. First
As shown in the figure, the heater element 4a and the common of the ambient temperature measuring resistance element 9 are commonly connected on the semiconductor substrate 1 and
By configuring as one electrode terminal, one wiring lead taken out from the flow velocity sensor can be reduced.
Also, or a slit portion 11 3 at the center portion of the heater element 4a shown in FIG. 1, or by widen the gap, the gas by equally divided into two heater elements 4a on the upstream side and the downstream side The temperature difference between the upstream part and the downstream part of the heater element 4a due to the flow becomes larger, and accordingly the temperature difference between the upstream side temperature measuring resistance element 5 and the downstream side temperature measuring resistance element 6 becomes larger. A sensitivity improving effect can be obtained. Also, heater element
Even if the temperature of the heater 4a is lowered, the same sensitivity as that of the normal heater can be obtained, so that the life of the heater element 4a can be extended.
また、第４図に示すようなパターン形状にヒータエレ
メント4bを構成しても前述と全く同様の効果が得られ
る。Further, even if the heater element 4b is configured in a pattern shape as shown in FIG. 4, the same effect as described above can be obtained.
なお、前述した実施例においては、半導体基板の一部
に空隙部を設けて形成した薄膜部構造を、ダイアフラム
構造とした場合について説明したが、本発明はこれに限
定されるものではなく、マイクロブリッジ構造に適用し
ても前述とほぼ同等の効果が得られることは言うまでも
ない。In addition, in the above-described embodiment, the thin film portion structure formed by providing the void portion in a part of the semiconductor substrate is described as the diaphragm structure, but the present invention is not limited to this, and the micro structure is not limited thereto. Needless to say, the same effect as described above can be obtained even when applied to the bridge structure.
また、前述した実施例においては、基台として半導体
基板を用いた場合について説明したが、本発明はこれに
限定されるものではなく、例えばアルミニウム，ステン
レスなどの金属基板を用い、ダイアフラム部をSiO2,Si3
N4などの絶縁膜で形成しても上述と同様に効果が得られ
ることは言うまでもない。Further, in the above-described embodiments, the case where the semiconductor substrate is used as the base has been described, but the present invention is not limited to this, and for example, a metal substrate such as aluminum or stainless steel is used, and the diaphragm portion is made of SiO 2. 2 , Si 3
Needless to say, the same effect as described above can be obtained by forming the insulating film such as N 4 .
さらに前述した実施例において、薄膜部構造は、エッ
チングにより形成した場合について説明したが、本発明
は、これに限られるものではなく、エンドミルレーザな
どによる加工形成した構造でも良く、また、基板とダイ
アフラム部とを別々に製作し、両者を張り合わせて形成
した構成でも同様な効果が得られることはことは言うま
でもない。Further, in the above-described embodiments, the thin film portion structure has been described as being formed by etching, but the present invention is not limited to this, and a structure formed by processing with an end mill laser or the like may also be used. It goes without saying that the same effect can be obtained by a structure in which the part and the part are manufactured separately and the parts are bonded together.
［発明の効果］ 以上、説明したように本発明による流速センサによれ
ば、測温抵抗体間に配置される発熱体の抵抗体パターン
の長さ方向端部の抵抗値を中央部よりも大きくしたこと
により、薄膜部に形成される温度分布が発熱体の抵抗パ
ターン長とほぼ平行に形成されるので、両側の測温抵抗
体の全体形状がほぼ矩形状に形成でき、これによって抵
抗値の設定が容易となるので、高感度の流速検出が可能
となる。また、測温抵抗体の長手方向の温度分布が均一
となるので、測温抵抗体が矩形状であってもその全ての
部分において気体の流れによる温度変化が起こるため、
低流速域における検出感度を大幅に向上させることがで
きる。さらに測温抵抗部のヒータに近い部分の極端な温
度上昇が防止できるため、ダストの付着による影響およ
び測温抵抗体間の温度係数（TCR）ミスマッチドリフト
などの影響を受けにくくなり、検出感度をさらに向上さ
せることができるなどの極めて優れた効果が得られる。[Advantages of the Invention] As described above, according to the flow velocity sensor of the present invention, the resistance value at the end portion in the length direction of the resistor pattern of the heating element arranged between the resistance temperature detectors is made larger than that at the central portion. By doing so, the temperature distribution formed in the thin film portion is formed substantially parallel to the resistance pattern length of the heating element, so that the entire shape of the resistance temperature detector on both sides can be formed in a substantially rectangular shape, which allows the resistance value Since setting is easy, highly sensitive flow velocity detection is possible. Further, since the temperature distribution in the longitudinal direction of the resistance temperature detector is uniform, even if the resistance temperature detector has a rectangular shape, a temperature change due to the flow of gas occurs in all parts thereof,
It is possible to significantly improve the detection sensitivity in the low flow velocity region. In addition, it is possible to prevent an extreme temperature rise in the part of the resistance temperature detector near the heater, so it is less susceptible to the effects of dust adhesion and the temperature coefficient (TCR) mismatch drift between resistance temperature detectors, thus improving the detection sensitivity. An extremely excellent effect such as further improvement can be obtained.
また、本願発明による他の流速センサによれば、抵抗
体パターンの長さ方向端部を測温抵抗体に近接配置した
ことにより、測温抵抗体部分の温度分布が発熱体の抵抗
体パターンの長手方向とほぼ平行になり、ダイアフラム
部上において均一な温度分布が得られ、高感度の流速検
出が可能となるなどの極めて優れた効果が得られる。Further, according to another flow velocity sensor according to the present invention, since the end portion in the length direction of the resistor pattern is arranged close to the resistance temperature detector, the temperature distribution of the resistance temperature detector portion is equal to the resistance pattern of the heating element. It becomes substantially parallel to the longitudinal direction, a uniform temperature distribution is obtained on the diaphragm portion, and extremely excellent effects such as high-sensitivity flow velocity detection can be obtained.
第１図は本発明による流速センサの一実施例による構成
を示す概略平面図、第２図は第１図の要部拡大平面図、
第３図は従来および本発明による流速センサの効果を説
明する平面図、第４図は本発明による流速センサの他の
実施例による構成を示すダイアフラム部分の拡大平面
図、第５図は従来の流速センサの構成を示す要部平面図
である。 １……半導体基板、２……空隙部、3a……ダイアフラム
部、4a,4b……ヒータエレメント、５……上流側測温抵
抗エレメント、６……下流側測温抵抗エレメント、８…
…矢印方向、９……周囲測温抵抗エレメント、11……ス
リット、111,112,113,114,115……スリット部。FIG. 1 is a schematic plan view showing a configuration of an embodiment of a flow velocity sensor according to the present invention, and FIG. 2 is an enlarged plan view of a main part of FIG.
FIG. 3 is a plan view for explaining the effect of the flow velocity sensor according to the related art and the present invention, FIG. 4 is an enlarged plan view of a diaphragm portion showing a configuration according to another embodiment of the flow velocity sensor according to the present invention, and FIG. It is a principal part top view which shows the structure of a flow velocity sensor. 1 ... Semiconductor substrate, 2 ... Air gap, 3a ... Diaphragm, 4a, 4b ... Heater element, 5 ... Upstream temperature measuring resistance element, 6 ... Downstream temperature measuring resistance element, 8 ...
… Arrow direction, 9 …… Ambient temperature measuring resistance element, 11 …… Slit, 11 1 , 11 2 , 11 3 , 11 4 , 11 5 …… Slit part.
Claims (2)
肉状に形成されたダイアフラム部と、前記ダイアフラム
部に気体の流れる方向と交差して形成された発熱体と、
前記発熱体の両側にそれぞれ形成された測温抵抗体とを
備え、前記発熱体部を構成する抵抗体パターンの長さ方
向端部の抵抗値を中央部よりも大きくしたことを特徴と
する流速センサ。1. A base, a diaphragm portion formed in a thin shape with a space provided in a part of the base, and a heating element formed in the diaphragm portion so as to intersect with a gas flow direction.
A flow velocity characterized by comprising resistance temperature detectors formed on both sides of the heating element, and a resistance value at a lengthwise end portion of a resistor pattern forming the heating element portion is made larger than at a central portion. Sensor.
長さ方向端部を前記測温抵抗体に近接配置したことを特
徴とする流速センサ。2. The flow velocity sensor according to claim 1, wherein an end portion in the length direction of the resistor pattern is arranged close to the resistance temperature detector.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2268497A JPH0830709B2 (en) | 1990-10-08 | 1990-10-08 | Flow velocity sensor |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2268497A JPH0830709B2 (en) | 1990-10-08 | 1990-10-08 | Flow velocity sensor |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH04145372A JPH04145372A (en) | 1992-05-19 |
| JPH0830709B2 true JPH0830709B2 (en) | 1996-03-27 |
Family
ID=17459322
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP2268497A Expired - Fee Related JPH0830709B2 (en) | 1990-10-08 | 1990-10-08 | Flow velocity sensor |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH0830709B2 (en) |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS63298120A (en) * | 1987-05-29 | 1988-12-05 | Sharp Corp | Flow sensor |
-
1990
- 1990-10-08 JP JP2268497A patent/JPH0830709B2/en not_active Expired - Fee Related
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS63298120A (en) * | 1987-05-29 | 1988-12-05 | Sharp Corp | Flow sensor |
Also Published As
| Publication number | Publication date |
|---|---|
| JPH04145372A (en) | 1992-05-19 |
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