JPH06103208B2 - Thermal flow sensor - Google Patents
Thermal flow sensorInfo
- Publication number
- JPH06103208B2 JPH06103208B2 JP63172414A JP17241488A JPH06103208B2 JP H06103208 B2 JPH06103208 B2 JP H06103208B2 JP 63172414 A JP63172414 A JP 63172414A JP 17241488 A JP17241488 A JP 17241488A JP H06103208 B2 JPH06103208 B2 JP H06103208B2
- Authority
- JP
- Japan
- Prior art keywords
- temperature
- sensor
- sensitive
- flow sensor
- resistance wire
- 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
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- Details Of Flowmeters (AREA)
- 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、ガス流量を精密に制御する際に使用されるマ
スフローコントローラの感熱型流量センサに関する。TECHNICAL FIELD The present invention relates to a heat-sensitive flow sensor of a mass flow controller used when precisely controlling a gas flow rate.
マスフローコントローラの感熱型流量センサとして細管
の外周に感温抵抗線を巻き線したセンサが広く用いられ
ているが、特開昭61−128123号にも述べられているよう
に周囲温度が変化するとセンサの出力電圧のゼロ点が変
動しやすく温度特性が悪いという欠点がある。この欠点
を解決するため定温度回路を設ける事が提案されている
が、（特開昭62−13120号や特開昭61−128123号）、回
路の製造原価が高くなるため広く実用化されるには至っ
ていないのが実状である。A sensor in which a temperature-sensitive resistance wire is wound around the outer periphery of a thin tube is widely used as a heat-sensitive flow rate sensor of a mass flow controller, but as described in JP-A-61-128123, the sensor is Has a drawback that the zero point of the output voltage is easily changed and the temperature characteristic is bad. To solve this drawback, it has been proposed to provide a constant temperature circuit (Japanese Patent Laid-Open No. 62-13120 and Japanese Patent Laid-Open No. 61-128123), but it is widely used because the manufacturing cost of the circuit becomes high. The reality is that it has not reached this point.
本発明は上述の点に鑑みてなされたもので、従来の感温
抵抗線を巻き線した方式のままで簡単な回路変更により
温度特性を向上させる事を目的とする。The present invention has been made in view of the above points, and it is an object of the present invention to improve temperature characteristics by a simple circuit change in the conventional method of winding a temperature-sensitive resistance wire.
一般に感温抵抗線を巻き線したセンサの温度特性は良く
ないと言われている。この原因は感熱型流量センサの原
理に依ると言われている。即ちセンサ管内を流れるガス
により生じる温度差をセンサの出力電圧として取り出す
ため、センサを構成している二つの感温抵抗線の周囲温
度に変化が生じると出力電圧のゼロ点が変化するため、
見掛け上流量が変化する。It is generally said that the temperature characteristics of a sensor in which a temperature sensitive resistance wire is wound are not good. It is said that this is due to the principle of the heat-sensitive flow sensor. That is, since the temperature difference caused by the gas flowing in the sensor tube is taken out as the output voltage of the sensor, the zero point of the output voltage changes when the ambient temperature of the two temperature-sensitive resistance wires forming the sensor changes.
The flow rate changes apparently.
従って温度特性を向上させる方法として、温度センサを
設け出力を補正すること等が考えられるが、これらの方
法では原価が高くなるにも関わらず効果は少ない。Therefore, as a method of improving the temperature characteristics, it is conceivable to provide a temperature sensor to correct the output, but these methods have little effect despite the high cost.
本発明は従来の感温抵抗線を巻き線した方式のままで簡
単な回路変更により温度特性を飛躍的に向上させる事を
目的とする。An object of the present invention is to dramatically improve the temperature characteristics by simply changing the circuit while keeping the conventional method of winding a temperature-sensitive resistance wire.
本発明者らはセンサの特性について詳しい解析を行なっ
た結果、センサの出力電圧は感温抵抗線に流れる電流の
３乗に比例し、感温抵抗線の抵抗値に比例する事が解っ
た。すなわち従来方式のセンサは周囲温度の変化に伴
い、感温抵抗線の抵抗値が変化するため出力電圧が変化
し温度特性が変化するという欠点を有している事が明ら
かになった。As a result of detailed analysis of the characteristics of the sensor, the present inventors have found that the output voltage of the sensor is proportional to the cube of the current flowing through the temperature-sensitive resistance wire and is proportional to the resistance value of the temperature-sensitive resistance wire. That is, it has been clarified that the conventional sensor has a defect that the resistance value of the temperature-sensitive resistance wire changes with the change of the ambient temperature, so that the output voltage changes and the temperature characteristic changes.
センサの出力電圧が感温抵抗線に流れる電流の３乗に比
例する事を考慮して、周囲温度の変化に伴い出力電圧が
変化する事を抑制するために本発明者らは次のような方
法を考案した。ある周囲温度でセンサが使用されている
状態での感温抵抗線の抵抗値をR0、感温抵抗線に流れる
電流をi0とする。周囲温度が変化した時の抵抗値が Ｒ＝R0（１＋δ）（但しδ≪１） （１） に変化したとする。この抵抗値の変化に対応して感温抵
抗線に流れる電流が に変化したとする。In view of the fact that the output voltage of the sensor is proportional to the cube of the current flowing in the temperature-sensitive resistance wire, the present inventors have the following in order to suppress the change of the output voltage due to the change of ambient temperature. Devised a method. Let R 0 be the resistance value of the temperature-sensitive resistance wire and i 0 be the current flowing through the temperature-sensitive resistance wire when the sensor is used at a certain ambient temperature. It is assumed that the resistance value when the ambient temperature changes changes to R = R 0 (1 + δ) (where δ << 1) (1). In response to this change in resistance, the current flowing through the temperature-sensitive resistance wire It has changed to.
センサ出力をV0とするとセンサの出力電圧は感温抵抗線
に流れる電流の３乗に比例し、感温抵抗線の抵抗値に比
例するので抵抗値の変化δが小さい場合 となりＶはδに依存しない。すなわち周囲温度が変化し
て抵抗値が変化しても感温抵抗線に流れる電流が（２）
式に従って変化するようにブリッジ回路を構成すればセ
ンサ出力が変動せずセンサの温度ドリフトを無くす事が
出来温度特性が向上する。If the sensor output is V 0 , the output voltage of the sensor is proportional to the cube of the current flowing in the temperature-sensitive resistance wire and proportional to the resistance value of the temperature-sensitive resistance wire. And V does not depend on δ. That is, even if the ambient temperature changes and the resistance value changes, the current flowing through the temperature-sensitive resistance wire is (2)
If the bridge circuit is configured so as to change according to the formula, the sensor output does not fluctuate and the temperature drift of the sensor can be eliminated, and the temperature characteristics are improved.
本発明者らは具体的に感温抵抗線に流れる電流を制御す
るため定電流回路で駆動されるブリッジ回路の片側が感
温抵抗線で構成され、他方が温度に依らない標準抵抗で
ある第１図の構成の回路を製作し、ブリッジ回路の抵抗
値を変化させて実験を繰り返した。その結果感温抵抗体
に流れる電流を定電流電源の電流の0.5倍から0.8倍にな
るようにブリッジ回路の抵抗値を設定すると周囲温度の
変化による出力電圧の変化が無視できるほど小さい事を
見い出した。即ち、第１図の構成において、定電流源の
出力をＩとすると、感熱抵抗線に流れる電流は、標準抵
抗２と感熱抵抗線１の抵抗比により分流され、 となる。The present inventors have specifically constructed a bridge circuit driven by a constant current circuit to control the current flowing through the temperature-sensitive resistance wire, in which one side is a temperature-sensitive resistance wire and the other is a standard resistance independent of temperature. The circuit having the configuration shown in FIG. 1 was manufactured, and the experiment was repeated while changing the resistance value of the bridge circuit. As a result, we found that if the resistance value of the bridge circuit is set so that the current flowing through the temperature sensitive resistor is 0.5 to 0.8 times the current of the constant current power supply, the change in output voltage due to the change in ambient temperature is negligible. It was That is, in the configuration of FIG. 1, assuming that the output of the constant current source is I, the current flowing through the thermal resistance wire is shunted by the resistance ratio of the standard resistance 2 and the thermal resistance wire 1, Becomes
ここで（１）式を代入すると、 （５）式と（２）式を比較すれば したがって、ｒ＝2Rと選べば（２）式を満足し、最も温
度ドリフトが減少し、その時の感熱抵抗線を流れる電流
値は、定電流源出力の2/3（0.67）となる。Substituting equation (1) here, Comparing equation (5) and equation (2) Therefore, if r = 2R is selected, the equation (2) is satisfied, the temperature drift is reduced most, and the current value flowing through the thermosensitive resistance wire at that time is 2/3 (0.67) of the constant current source output.
従って本特許の請求範囲は、測定時の温度の影響，抵抗
値の誤差，選定の範囲を考えて0.5〜0.8倍とした。Therefore, the scope of the claims of this patent is set to 0.5 to 0.8 times in consideration of the influence of the temperature at the time of measurement, the error of the resistance value, and the selection range.
以下、本発明を実施例に基づき、より詳細に説明する。 Hereinafter, the present invention will be described in more detail based on examples.
（実施例１） 外径0.6mm,肉厚30μｍのステンレスパイプを使用して第
２図に示すような構成で感熱型流量センサを作成した。
発熱抵抗線を10mmの幅に渡って巻き付けた。１つの発熱
体の抵抗値は50Ωであった。抵抗体に定電流制御方式で
電流を0.05A流しセンサを加熱した。加熱時の抵抗値は
周囲温度が25℃の時75Ωであった。図３に本センサの流
量特性を示す。(Example 1) A heat-sensitive flow rate sensor was prepared by using a stainless pipe having an outer diameter of 0.6 mm and a wall thickness of 30 µm and having a configuration as shown in Fig. 2.
A heating resistance wire was wound over a width of 10 mm. The resistance value of one heating element was 50Ω. The sensor was heated by applying a constant current of 0.05 A to the resistor using the constant current control method. The resistance value during heating was 75Ω when the ambient temperature was 25 ° C. FIG. 3 shows the flow rate characteristics of this sensor.
ｒ＝75Ωの時は定電力的に感熱抵抗体を駆動している
が、周囲温度が上昇すると感温抵抗体の抵抗値が増加し
流れる電流が減少するため出力電圧が低下し、出力電圧
の温度特性は負である。またｒ＝400Ωと大きくする
と、周囲温度が上昇したとき感熱抵抗体に流れる電流の
減少に比べて抵抗の増加が大きいため、出力電圧が増加
し温度特性は正となる。しかしｒ＝150Ωに選べば周囲
温度が変化しても出力電圧が変化せず温度特性が向上し
ている。この時感熱抵抗体に流れる電流は定電流電源の
電流の0.7倍であった。When r = 75Ω, the thermal resistor is driven with constant power, but when the ambient temperature rises, the resistance value of the thermal resistor increases and the flowing current decreases, so the output voltage decreases and the output voltage The temperature characteristic is negative. Further, if r = 400Ω is set to be large, the increase in resistance is larger than the decrease in the current flowing through the thermosensitive resistor when the ambient temperature rises, so that the output voltage increases and the temperature characteristic becomes positive. However, if r = 150Ω is selected, the output voltage does not change even if the ambient temperature changes, and the temperature characteristics are improved. At this time, the current flowing through the thermal resistor was 0.7 times the current of the constant current power supply.
（実施例２） 実施例１と同じ構成のセンサでブリッジ抵抗はｒ＝400
Ωと大きくしておき、第４図に示すようにブリッジ抵抗
に並列に抵抗を追加し、追加した。抵抗値を変化させて
温度特性を調べたところ、合成抵抗が310Ωの時温度変
動が最も小さくなった。この時感熱抵抗体に流れる電流
は定電流電源の電流の0.6倍であった。Example 2 A sensor having the same configuration as in Example 1 has a bridge resistance of r = 400.
Ω was made large, and a resistor was added in parallel with the bridge resistor as shown in FIG. When the temperature characteristics were investigated by changing the resistance value, the temperature fluctuation was the smallest when the combined resistance was 310Ω. At this time, the current flowing through the thermosensitive resistor was 0.6 times the current of the constant current power supply.
以上詳述したように、本発明は従来の感温抵抗線を巻き
線した方式のままでブリッジ回路の外部抵抗の選択法を
明確にするだけで温度特性を飛躍的に向上させる事が可
能となり工業上極めて有効である。As described above in detail, according to the present invention, it is possible to dramatically improve the temperature characteristics only by clarifying the selection method of the external resistance of the bridge circuit with the conventional method of winding the temperature sensitive resistance wire. It is extremely effective in industry.
第１図は本発明の実施例のセンサの構成を示す。第２図
は本発明の実施例のセンサの構成を示す。第３図は本発
明の実施例のセンサの温度特性を示す。第４図は本発明
の実施例のセンサの構成を示す。FIG. 1 shows the structure of a sensor according to an embodiment of the present invention. FIG. 2 shows the structure of the sensor according to the embodiment of the present invention. FIG. 3 shows the temperature characteristics of the sensor of the embodiment of the present invention. FIG. 4 shows the structure of the sensor according to the embodiment of the present invention.
Claims (1)
差によって電気抵抗が変化する事を利用して、流れるガ
スの質量流量に対応した電圧を出力する少なくとも二つ
の感温抵抗体をセンサ管の外周に設けた流量センサであ
って、前記感温抵抗体と他の二つの標準抵抗からなるブ
リッジ回路を定電流電源で駆動する流量センサにおい
て、流量センサを使用時に感温抵抗体に流れる電流を定
電流電源の電流の0.5倍から0.8倍になるようにブリッジ
回路の抵抗値を設定した事を特徴とする感熱型流量セン
サ。1. At least two temperature-sensitive resistors that output a voltage corresponding to the mass flow rate of flowing gas are provided at the outer circumference of the sensor tube by utilizing the fact that the electric resistance changes due to the temperature difference caused by the gas flowing in the sensor tube. A flow sensor provided with a constant current source for driving a bridge circuit consisting of the temperature sensitive resistor and two other standard resistors with a constant current power supply, the current flowing through the temperature sensitive resistor is fixed when the flow sensor is used. A heat-sensitive flow sensor characterized by setting the resistance value of the bridge circuit so that it becomes 0.5 times to 0.8 times the current of the current source.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP63172414A JPH06103208B2 (en) | 1988-07-11 | 1988-07-11 | Thermal flow sensor |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP63172414A JPH06103208B2 (en) | 1988-07-11 | 1988-07-11 | Thermal flow sensor |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH0222515A JPH0222515A (en) | 1990-01-25 |
| JPH06103208B2 true JPH06103208B2 (en) | 1994-12-14 |
Family
ID=15941518
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP63172414A Expired - Lifetime JPH06103208B2 (en) | 1988-07-11 | 1988-07-11 | Thermal flow sensor |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH06103208B2 (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2501734B (en) * | 2012-05-02 | 2015-02-04 | Lateral Design Ltd | Improvements in and relating to vehicle access apparatus and a method thereof |
-
1988
- 1988-07-11 JP JP63172414A patent/JPH06103208B2/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| JPH0222515A (en) | 1990-01-25 |
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