JPH0449905B2 - - Google Patents
Info
- Publication number
- JPH0449905B2 JPH0449905B2 JP60146789A JP14678985A JPH0449905B2 JP H0449905 B2 JPH0449905 B2 JP H0449905B2 JP 60146789 A JP60146789 A JP 60146789A JP 14678985 A JP14678985 A JP 14678985A JP H0449905 B2 JPH0449905 B2 JP H0449905B2
- Authority
- JP
- Japan
- Prior art keywords
- optical fiber
- humidity
- gas
- light
- measured
- 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
- 239000013307 optical fiber Substances 0.000 claims description 62
- 238000000034 method Methods 0.000 claims description 14
- 238000005253 cladding Methods 0.000 claims description 6
- 230000002123 temporal effect Effects 0.000 claims 2
- 238000005259 measurement Methods 0.000 description 31
- 125000006850 spacer group Chemical group 0.000 description 9
- 230000003287 optical effect Effects 0.000 description 8
- 239000011347 resin Substances 0.000 description 8
- 229920005989 resin Polymers 0.000 description 8
- 238000010521 absorption reaction Methods 0.000 description 3
- 230000005540 biological transmission Effects 0.000 description 3
- 238000010586 diagram Methods 0.000 description 3
- 230000035945 sensitivity Effects 0.000 description 3
- 239000000919 ceramic Substances 0.000 description 2
- 239000000428 dust Substances 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 239000004033 plastic Substances 0.000 description 2
- 229920003023 plastic Polymers 0.000 description 2
- 230000032683 aging Effects 0.000 description 1
- 238000004891 communication Methods 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 239000000835 fiber Substances 0.000 description 1
- 239000011521 glass Substances 0.000 description 1
- 230000007774 longterm Effects 0.000 description 1
- 238000003754 machining Methods 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000000691 measurement method Methods 0.000 description 1
- 239000010453 quartz Substances 0.000 description 1
- 230000004044 response Effects 0.000 description 1
- 230000004043 responsiveness Effects 0.000 description 1
- 238000011896 sensitive detection Methods 0.000 description 1
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 1
- 239000013589 supplement Substances 0.000 description 1
- 230000008961 swelling Effects 0.000 description 1
- 230000008719 thickening Effects 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
- G01N21/41—Refractivity; Phase-affecting properties, e.g. optical path length
- G01N21/43—Refractivity; Phase-affecting properties, e.g. optical path length by measuring critical angle
- G01N21/431—Dip refractometers, e.g. using optical fibres
Landscapes
- Physics & Mathematics (AREA)
- Health & Medical Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Chemical & Material Sciences (AREA)
- Analytical Chemistry (AREA)
- Biochemistry (AREA)
- General Health & Medical Sciences (AREA)
- General Physics & Mathematics (AREA)
- Immunology (AREA)
- Pathology (AREA)
- Investigating Or Analysing Materials By Optical Means (AREA)
- Testing Of Optical Devices Or Fibers (AREA)
Description
【発明の詳細な説明】
［産業上の利用分野］
本発明は光フアイバ自体を湿度センサとして用
いた湿度の測定方法および光フアイバ形の湿度セ
ンサに関する。DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a humidity measuring method using an optical fiber itself as a humidity sensor and to an optical fiber type humidity sensor.
［従来の技術］
従来の湿度測定は、セラミツク・プラスチツク
等の素材の湿度に対する抵抗変化や容量変化を利
用し、これらを電気的に検出して湿度を求める方
式が大半を占めている。[Prior Art] Most conventional humidity measurements utilize resistance changes and capacitance changes in materials such as ceramics and plastics due to humidity, and detect these electrically to determine humidity.
また、光フアイバを用いる方式としては、第７
図に示すように、送光用光フアイバ１の出射端と
受光用光フアイバ２の入射端とを空間３を隔てて
対抗させて配置し、空間３内の空気の湿度変化に
よるその赤外吸収強度変化を利用して、光源４か
らの光を送光用光フアイバ１、空間３および受光
用光フアイバ２を伝送させてその強度を受光器５
にて検出する方式がある。更に、この方式を改良
したものとして、送・受光用光フアイバ間に特定
波長の吸収係数が湿度によつて変化する感湿樹脂
を介装する方式も提案されている（特開昭56−
67738号）。 In addition, as a method using optical fiber, the seventh
As shown in the figure, the output end of the light transmitting optical fiber 1 and the input end of the light receiving optical fiber 2 are arranged to face each other across a space 3, and the infrared rays are absorbed by changes in the humidity of the air in the space 3. Using the intensity change, the light from the light source 4 is transmitted through the light transmitting optical fiber 1, the space 3, and the light receiving optical fiber 2, and the intensity is transmitted to the light receiver 5.
There is a method to detect this. Furthermore, as an improvement on this method, a method has been proposed in which a moisture-sensitive resin whose absorption coefficient of a specific wavelength changes depending on humidity is interposed between the optical fibers for transmitting and receiving light (Japanese Patent Application Laid-Open No. 1983-1999).
No. 67738).
［発明が解決しようとする問題点］
ところが、上記の湿度に対する抵抗変化等を電
気的に検出する方式では、高電圧環境下における
湿度検出には適用上、電気雑音など多くの問題が
ある。更に、この方式では、湿度により抵抗等が
変化するセンサが設置された極く限られた領域内
の湿度した検出できず、長区間に亙る湿度分布を
測定する場合には数多くのセンサを設置する必要
がある。[Problems to be Solved by the Invention] However, the above-mentioned method of electrically detecting changes in resistance due to humidity, etc. has many problems such as electrical noise due to its application in detecting humidity in a high voltage environment. Furthermore, with this method, it is not possible to detect humidity within a very limited area where sensors whose resistance changes depending on humidity are installed, and many sensors must be installed when measuring humidity distribution over a long area. There is a need.
また、第７図に示す光学方式では、高電圧下で
も適用可能であるが、湿度変化などによつて送光
用光フアイバ１と受光用光フアイバ２との光軸が
ずれたり、あるいは外気中のほこりの影響を受け
たりし易く安定した測定が困難であり、限定され
た環境下でしか使用できない。更に、光学レンズ
６や光ファイバ１，２を支持する治具等に高精度
加工が要求される。 The optical system shown in Fig. 7 can be applied even under high voltage, but the optical axis of the light transmitting optical fiber 1 and the light receiving optical fiber 2 may be misaligned due to changes in humidity, or when exposed to outside air. It is difficult to make stable measurements because it is easily affected by dust, and it can only be used in limited environments. Furthermore, high-precision machining is required for the jigs and the like that support the optical lens 6 and the optical fibers 1 and 2.
一方、送・受光用光フアイバ間に感湿樹脂を介
装する方式では、光学系の固定が容易となると共
に湿度以外のほこり等の影響を受けにくくなる。
しかし、感湿樹脂の吸湿膨潤によつて感湿樹脂と
光フアイバとの結合部にマイクロベンドが生じ、
これに伴い損失が増加し安定した測定が難しい。
また、感湿樹脂が経年劣化し十分な長期性能が得
られない。更に光伝送路に感湿樹脂を挿入する方
式である、感湿樹脂を厚くして湿度変化に対する
感度を上げようとすると、必然的に光の減衰が大
きくなり受光量が低下するという問題がある。ま
た、特定の波長の光のみを検出する方式であるた
め、装置が高価なものとなる。また、被測定気体
中に配設された光フアイバの透過光強度の変化か
ら湿度を測定する湿度センサが、例えば特開昭52
−3480号公報、特開昭58−190742号公報、特開昭
59−92332号公報並びに実開昭52−150275号明細
書及び図面として提案されている。この湿度セン
サは、第１図に示すように、光フアイバコア７が
空気等の被測定気体で満たされた測定域８に配設
されており、光フアイバコア７の一端には光源９
が、また他端には受光器１０が設けられている。
後述するように、測定域８内の湿度が変化する
と、被測定気体の屈折率も変化するため、光フア
イバコア７内の光の伝播モードが変化し、その結
果、受光器１０により検出される透過光強度が変
化する。従つて、受光器１０の透過光強度から被
測定気体の湿度を求めることができる。しかしな
がら、この第１図に示す湿度センサは、１つの測
定域の湿度だけしか測定できず、測定域が多数存
在する場合には、湿度センサをその数だけ準備し
なければならず、極めて不経済である。 On the other hand, in a method in which a moisture-sensitive resin is interposed between optical fibers for transmitting and receiving light, the optical system can be easily fixed and is less susceptible to influences other than humidity, such as dust.
However, due to moisture absorption and swelling of the moisture-sensitive resin, microbends occur at the joint between the moisture-sensitive resin and the optical fiber.
This increases loss and makes stable measurement difficult.
Moreover, the moisture-sensitive resin deteriorates over time, making it impossible to obtain sufficient long-term performance. Furthermore, if you try to increase the sensitivity to changes in humidity by thickening the moisture-sensitive resin, which is a method of inserting a moisture-sensitive resin into the optical transmission path, there is a problem that the attenuation of light will inevitably increase and the amount of light received will decrease. . Furthermore, since the method detects only light of a specific wavelength, the device becomes expensive. In addition, a humidity sensor that measures humidity from changes in the intensity of transmitted light through an optical fiber disposed in a gas to be measured has been developed, for example, in Japanese Patent Laid-Open No. 52
-3480 Publication, JP-A-58-190742, JP-A-Sho
It has been proposed in Japanese Patent No. 59-92332 and Japanese Utility Model Application No. 52-150275, as well as the specification and drawings. In this humidity sensor, as shown in FIG.
However, a light receiver 10 is provided at the other end.
As will be described later, when the humidity in the measurement area 8 changes, the refractive index of the gas to be measured also changes, so the propagation mode of light in the optical fiber core 7 changes, and as a result, the transmission detected by the light receiver 10 changes. Light intensity changes. Therefore, the humidity of the gas to be measured can be determined from the transmitted light intensity of the light receiver 10. However, the humidity sensor shown in Figure 1 can only measure the humidity in one measurement area, and if there are many measurement areas, it is necessary to prepare the same number of humidity sensors, which is extremely uneconomical. It is.
［発明の目的］
本発明は以上の従来技術の問題点を解消すべく
創案されたものであり、本発明の目的は、高安
定、高精度でしかも適用範囲の広い湿度測定を安
価に実施できると共に、長距離にわたつて湿度の
分布を測定することができる湿度の測定方法およ
びこれに使用する湿度センサを提供することにあ
る。[Object of the Invention] The present invention has been devised to solve the problems of the prior art described above, and an object of the present invention is to provide a highly stable, highly accurate, and widely applicable humidity measurement method at low cost. Another object of the present invention is to provide a humidity measuring method capable of measuring humidity distribution over a long distance, and a humidity sensor used therein.
［発明の概要］
上記の目的を達成するために、本発明は、その
湿度を測定しようとする被測定気体が光フアイバ
コアに直接接触するようにし、被測定気体の湿度
によりその屈折率が変化することによつて光フア
イバコアで後方散乱光が発生すること及びその後
方散乱光が発生する位置によつて光を入射してか
ら後方散乱光が光源側に戻つてくるまでの時間に
差があることを利用して湿度及びその分布を検出
するようにしたものである。[Summary of the Invention] In order to achieve the above object, the present invention allows the gas to be measured, the humidity of which is to be measured, to directly contact the optical fiber core, and the refractive index of the gas to be measured changes depending on the humidity of the gas to be measured. In some cases, backscattered light is generated in the optical fiber core, and depending on the position where the backscattered light is generated, there is a difference in the time from when the light is incident until the backscattered light returns to the light source side. The humidity and its distribution are detected by using the humidity.
［実施例］
以下に本発明の実施例を添付図面に従つて詳述
する。[Examples] Examples of the present invention will be described in detail below with reference to the accompanying drawings.
第２図には本発明の湿度測定方法を実施するた
めの装置を示す。同図において、７は石英、多成
分ガラス、プラスチツク等からなる光フアイバコ
アであり、光フアイバコア７は空気等の被測定気
体で満たされた測定域８に配設されている。光フ
アイバ７は被測定気体によつて取り囲まれてお
り、光フアイバコア７の外周は被測定気体のクラ
ツデイングとなつている。また、被測定気体の湿
度が増加するとのその屈折率も増加し、第３図に
示す如く、光フアイバコア７の屈折率ncに対し被
測定気体の屈折率ngはその湿度変化により変動す
る。このため、被測定気体の湿度変化に応じてそ
の屈折率が変化すると、光フアイバコア７とその
外周の被測定気体との屈折率差nc−ngにより決定
される光フアイバコア７内の光の伝播モードが変
化する。そのため、この被測定気体の屈折率変化
による光の伝播モードの変化によつて、光フアイ
バコア７内には後方散乱光が発生し、それを検出
することで湿度及びその分布を測定することがで
きる。即ち、パルス発生器１１により光源９を変
調してパルス光を発生させ、これを光フアイバコ
ア７に入射する。光フアイバコア７の軸方向には
適宜間隔にて被測定気体が包囲する測定域８…が
あり、光フアイバコア７に入射されたパルス光は
各測定域８の被測定気体の湿度変化による屈折率
変化に応じた散乱を受け、その後方散乱光の強度
はハーフミラー１２を介して受光器１０により検
出される。パルス発生器１１のパルス発生時間は
タイミング発生器１３で監視し、このパルス発生
時間と受光器１０が検出した後方散乱光のパルス
検出時間および強度とから信号処理回路１４で各
測定域８の湿度を算出し、デイスプレイ装置１５
に表示する。上記の透過光強度による湿度測定は
１点測定ないし測定域８の平均湿度の測定であつ
たが、この湿度測定は測定域８…の多点測定とな
つている。なお、連続的な湿度分布測定も可能で
ある。 FIG. 2 shows an apparatus for carrying out the humidity measuring method of the present invention. In the figure, reference numeral 7 denotes an optical fiber core made of quartz, multicomponent glass, plastic, etc., and the optical fiber core 7 is disposed in a measurement region 8 filled with a gas to be measured such as air. The optical fiber 7 is surrounded by the gas to be measured, and the outer periphery of the optical fiber core 7 forms a cladding of the gas to be measured. Furthermore, as the humidity of the gas to be measured increases, its refractive index also increases, and as shown in FIG. . Therefore, when the refractive index of the gas to be measured changes depending on the humidity change, the light inside the optical fiber core 7 is determined by the refractive index difference n c - n g between the optical fiber core 7 and the gas to be measured around its outer periphery. The propagation mode changes. Therefore, due to the change in the light propagation mode due to the change in the refractive index of the gas to be measured, backscattered light is generated within the optical fiber core 7, and by detecting it, the humidity and its distribution can be measured. . That is, the light source 9 is modulated by the pulse generator 11 to generate pulsed light, which is input into the optical fiber core 7. In the axial direction of the optical fiber core 7, there are measurement regions 8 surrounded by the gas to be measured at appropriate intervals, and the pulsed light incident on the optical fiber core 7 changes the refractive index due to changes in the humidity of the gas to be measured in each measurement region 8. The intensity of the backscattered light is detected by the light receiver 10 via the half mirror 12. The pulse generation time of the pulse generator 11 is monitored by the timing generator 13, and the humidity of each measurement area 8 is determined by the signal processing circuit 14 from this pulse generation time and the pulse detection time and intensity of the backscattered light detected by the light receiver 10. is calculated, and the display device 15
to be displayed. The humidity measurement using the transmitted light intensity was a single point measurement or a measurement of the average humidity of the measurement area 8, but this humidity measurement is a multi-point measurement of the measurement area 8. Note that continuous humidity distribution measurement is also possible.
次に、上記光フアイバコア７の機械的強度を補
い且つ被測定気体を流通させつつ被測定気体で光
フアイバコア７を包む気体クラツデイング構造を
有する本発明の湿度センサについて述べる。 Next, a humidity sensor of the present invention having a gas cladding structure that supplements the mechanical strength of the optical fiber core 7 and wraps the optical fiber core 7 with the gas to be measured while allowing the gas to be measured to flow will be described.
第４図または第５図に示す如く、光フアイバコ
ア７の外周にはその軸方向に沿つて波形管状体と
してのバロン形スペーサ１６が設けられている。
バロン形スペーサ１６は、光フアイバコア７に嵌
合し光フアイバコア７を固定支持する小径部１６
ａと光フアイバコア７の外周に被測定気体の気体
層１７を形成させるための大径部１６ｂとからな
る。大径部１６ｂには、被測定気体を流通させる
ための流通孔１８が多数形成されており、大径部
１６ｂは多孔質状となつている。バロン形スペー
サ１６の外周には湿度センサに耐張力性を与える
ための繊維構造のテンシヨンメンバ１９…が設け
られている。光フアイバコア７の軸方向に沿うテ
ンシヨンメンバ１９はバロン形スペーサ１６の周
方向に適宜間隔にバロン形スペーサ１６を取り囲
むように設けられている。更に、これらテンシヨ
ンメンバ１９の外周には多数の通孔２０を有する
多孔質シース２１が被覆されている。 As shown in FIG. 4 or 5, a ballon-shaped spacer 16 as a corrugated tubular body is provided on the outer periphery of the optical fiber core 7 along its axial direction.
The ballon-shaped spacer 16 is a small diameter portion 16 that fits into the optical fiber core 7 and fixedly supports the optical fiber core 7.
a, and a large diameter portion 16b for forming a gas layer 17 of the gas to be measured around the outer periphery of the optical fiber core 7. The large diameter portion 16b has a large number of flow holes 18 formed therein to allow the gas to be measured to flow therethrough, and the large diameter portion 16b is porous. On the outer periphery of the ballon-shaped spacer 16, tension members 19 of a fiber structure are provided to provide tension resistance to the humidity sensor. Tension members 19 extending along the axial direction of the optical fiber core 7 are provided so as to surround the ballon-shaped spacer 16 at appropriate intervals in the circumferential direction of the ballon-shaped spacer 16. Furthermore, the outer periphery of these tension members 19 is covered with a porous sheath 21 having a large number of through holes 20.
このように多孔質シース２１外側とバロン形ス
ペーサ１６内側に気体層１７とが通孔２０および
流通孔１８を介して連通されているので、多孔質
シース２１外側の被測定気体は気体層１７に流入
し、逆に気体層１７内の気体は外部へと流出し、
光フアイバコア７は常に新たな被測定気体によつ
て取り囲まれることになる。従つて、この湿度セ
ンサにおいても、入射光が光フアイバコア７とバ
ロン形スペーサ１６内側の気体層１７の被測定気
体との界面で反射を繰り返しながら伝播する第３
図に示すステツプインデツス型の光伝送路となつ
ており、被測定気体と湿度変化（含有水分量変
化）は屈折率変化として検出される。この湿度セ
ンサを用いて空気の相対湿度を20〜80％の範囲で
変化させて１つの測定域８へ発生した後方散乱光
の強度変化を測定したところ、第６図に示すよう
に3dB以上の強度変化があり、良好な感度および
高速応答性を有することが確かめられた。 In this way, the gas layer 17 is communicated between the outside of the porous sheath 21 and the inside of the ballon-shaped spacer 16 via the through hole 20 and the circulation hole 18, so that the gas to be measured outside the porous sheath 21 is transferred to the gas layer 17. The gas in the gas layer 17 flows out, and conversely, the gas in the gas layer 17 flows out.
The optical fiber core 7 is always surrounded by new gas to be measured. Therefore, in this humidity sensor as well, the incident light propagates while being repeatedly reflected at the interface between the optical fiber core 7 and the gas to be measured in the gas layer 17 inside the ballon-shaped spacer 16.
It is a step index type optical transmission path as shown in the figure, and changes in the measured gas and humidity (changes in the amount of water contained) are detected as changes in the refractive index. Using this humidity sensor, we measured the intensity change of backscattered light generated in one measurement area 8 while changing the relative humidity of the air in the range of 20 to 80%. It was confirmed that there was a change in intensity, and that it had good sensitivity and high-speed response.
また、光フアイバコア７がバロン形スペーサ１
６、テンシヨンメンバ１９、多孔質シース２１に
よつて被われているので、実際に使用する十分な
機械的性能を有し、耐久性・信頼性が高い。 In addition, the optical fiber core 7 is connected to the ballon-shaped spacer 1.
6. Since it is covered by the tension member 19 and the porous sheath 21, it has sufficient mechanical performance for actual use and is highly durable and reliable.
なお、バロン形スペーサ１６等からなる上記の
気体クラツデイング構造を、光フアイバコア７の
全長に施しても、あるいは複数の測定点に対応し
て光フアイバコア７の軸方向に適宜間隔を隔てて
形成するようにしてもよい。また、上記の気体ク
ラツデイング構造に代え、光フアイバコア７を、
光フアイバコア７の外径よりも大きな内径を有し
且つ多数の流通光を有するチユーブ内に収納した
ものとしてもよい。 The above-mentioned gas cladding structure consisting of the ballon-shaped spacer 16 etc. may be applied to the entire length of the optical fiber core 7, or may be formed at appropriate intervals in the axial direction of the optical fiber core 7 corresponding to a plurality of measurement points. You may also do so. Moreover, instead of the above-mentioned gas cladding structure, the optical fiber core 7 is
It may be housed in a tube having an inner diameter larger than the outer diameter of the optical fiber core 7 and having a large number of circulating lights.
次に、具体的な実験結果について説明する。第
８図に示すように、長さ200ｍ以上の光フアイバ
の100ｍと200ｍの地点にそれぞれ測定域８１，８
２を設け、測定域８１には湿度80％の空気を存在
させ、測定域８２には湿度50％の空気を存在させ
て測定した。その結果、同図に示すように、測定
域の位置と後方散乱光の強度変化の位置が一致し
ており、本発明によつて湿度の分布を正確に測定
できることが確認された。更に、測定域８１では
4dB、また測定域８２では2dBの強度変化が認め
られ、これは第６図に示した湿度と後方散乱光の
強度変化と一致するものであり、本発明によつて
湿度を正確に測定できることが確認された。 Next, specific experimental results will be explained. As shown in Figure 8, measurement areas 81 and 8 are located at 100 m and 200 m points of an optical fiber with a length of 200 m or more, respectively.
2, air with a humidity of 80% was present in the measurement area 81, and air with a humidity of 50% was present in the measurement area 82, and measurements were taken. As a result, as shown in the figure, the position of the measurement area and the position of the intensity change of the backscattered light coincided, confirming that the present invention can accurately measure the humidity distribution. Furthermore, in the measurement area 81
A change in intensity of 4 dB and 2 dB in measurement area 82 was observed, which coincides with the change in intensity of humidity and backscattered light shown in FIG. 6, indicating that the present invention can accurately measure humidity. confirmed.
［発明の効果］
以上要するに本発明によれば、次のような優れ
た効果を発揮する。[Effects of the Invention] In summary, according to the present invention, the following excellent effects are achieved.
(1) 光フアイバコア自体が湿度センサであり、光
フアイバコア以外の光学的素子を全く必要とせ
ず、また赤外線等の特定波長で測定する必要も
ない。このため、測定系の簡素化が図れ、取扱
も容易であると共にコストを低減できる。(1) The optical fiber core itself is a humidity sensor, and there is no need for any optical elements other than the optical fiber core, and there is no need to measure at specific wavelengths such as infrared rays. Therefore, the measurement system can be simplified, handling is easy, and costs can be reduced.
(2) 更に、光フアイバ自体を湿度センサとしてい
るので、経年劣化や光学レンズ等の介在による
損失の発生要因がなく、長期に亙つて安定した
測定ができる。(2) Furthermore, since the optical fiber itself is used as a humidity sensor, there is no cause of loss due to aging or intervening optical lenses, and stable measurement can be performed over a long period of time.
(3) １点のみでなく、光フアイバコアの長手方向
に沿つた湿度・水分量の分布、あるいは平均湿
度など長距離センジングが可能である。(3) Long-distance sensing is possible, not just at one point, but also on the distribution of humidity and moisture content along the length of the optical fiber core, or the average humidity.
(4) 被測定気体の湿度による顕著な屈折率変化を
利用しているため、広い湿度領域で高感度の検
出ができる。また、透過光強度の湿度依存性を
高めるべく光フアイバコアの長さを増しても、
光の減衰は少なく容易に高感度化が図れる。(4) Since it utilizes the remarkable change in refractive index due to the humidity of the measured gas, highly sensitive detection is possible over a wide humidity range. Furthermore, even if the length of the optical fiber core is increased to increase the humidity dependence of transmitted light intensity,
Light attenuation is small and high sensitivity can be easily achieved.
(5) セラミツク・感湿樹脂等の感湿素子の吸湿に
よる特性変化を利用して湿度を検出するのでは
なく、光フアイバコアの外周に被測定気体を直
接接触させて検出するようにしているため、応
答性がよく湿度変化に迅速に検出できる。(5) Humidity is detected by bringing the gas to be measured into direct contact with the outer periphery of the optical fiber core, rather than detecting humidity by using the change in characteristics due to moisture absorption of a moisture-sensitive element such as ceramic or moisture-sensitive resin. , has good responsiveness and can quickly detect humidity changes.
第１図は従来例を示す概略構成図、第２図は本
発明に係る湿度の測定方法を実施するための装置
を示す概略構成図、第３図はこれら装置の光フア
イバコア周囲の屈折率分布を示す図、第４図は本
発明に係る湿度センサの一実施例を示す横断面
図、第５図は同湿度センサの縦断面図、第６図は
第４図の湿度センサの後方散乱光強度−湿度依存
性の測定結果を示すグラフ、第７図は従来の湿度
測定装置を示す概略構成図、第８図は本発明の実
験結果を示すグラフである。
図中、７は光フアイバコア、８は測定域、９は
光源、１０は受光器、１１はパルス発生器、１２
はハーフミラー、１３はタイミング発生器、１４
は信号処理回路、１５はデイスプレイ装置、１６
はバロン形スペーサ、１６ａは小径部、１６ｂは
大径部、１７は気体層、１８は流通孔、１９はテ
ンシヨンメンバ、２０は通孔、２１は多孔質シー
スである。
FIG. 1 is a schematic configuration diagram showing a conventional example, FIG. 2 is a schematic configuration diagram showing an apparatus for implementing the humidity measuring method according to the present invention, and FIG. 3 is a refractive index distribution around the optical fiber core of these devices. FIG. 4 is a cross-sectional view showing an embodiment of the humidity sensor according to the present invention, FIG. 5 is a vertical cross-sectional view of the same humidity sensor, and FIG. 6 is a backscattered light of the humidity sensor of FIG. 4. FIG. 7 is a graph showing the measurement results of intensity-humidity dependence, FIG. 7 is a schematic configuration diagram showing a conventional humidity measuring device, and FIG. 8 is a graph showing experimental results of the present invention. In the figure, 7 is an optical fiber core, 8 is a measurement area, 9 is a light source, 10 is a light receiver, 11 is a pulse generator, 12
is a half mirror, 13 is a timing generator, 14
is a signal processing circuit, 15 is a display device, 16
16a is a small diameter portion, 16b is a large diameter portion, 17 is a gas layer, 18 is a communication hole, 19 is a tension member, 20 is a through hole, and 21 is a porous sheath.
Claims (1)
被測定気体によつて包囲されるように上記光フア
イバコアを上記被測定気体中に入れ、上記光フア
イバコアに光を入射し、上記光フアイバコア内で
発生して光入射側へ戻つてくる後方散乱光の強度
から上記被測定気体の湿度を求めると共に、上記
後方散乱光の光入射側へ到達する時間的変化から
光フアイバコアの軸方向に沿う上記被測定気体の
湿度の分布を求めるようにしたことを特徴とする
湿度の測定方法。 ２ 露出された光フアイバコアが断続的に湿度を
測定する被測定気体と接触するようになした気体
クラツデイング構造の光フアイバと、上記光フア
イバコアに光を入射する光源と、上記光フアイバ
コア内で発生して上記光源側へ戻つてくる後方散
乱光を受光するための受光器と、該受光器へ上記
後方散乱光を導くために上記光源と上記光フアイ
バとの間に設けられた光分岐手段と、上記受光器
で検出した上記後方散乱光の強度から上記被測定
気体の湿度を求めると共に、上記後方散乱光の光
入射側へ到達する時間的変化から光フアイバコア
の軸方向に沿う上記被測定気体の湿度の分布を求
める信号処理回路とを備えたことを特徴とする湿
度センサ。 ３ 上記気体クラツデイング構造が上記光フアイ
バコアに嵌合される小径部と上記被測定気体を流
通させる流通孔を有し且つ上記光フアイバコアの
外周に上記被測定気体の気体層を形成させるため
の大径部とからなる波形管状体により構成されて
いることを特徴とする特許請求の範囲第２項に記
載の湿度センサ。[Scope of Claims] 1. The optical fiber core is placed in the gas to be measured so that the outer periphery of the optical fiber core is surrounded by the gas to be measured, the humidity of which is to be measured, and light is incident on the optical fiber core, The humidity of the gas to be measured is determined from the intensity of the backscattered light generated within the optical fiber core and returned to the light incidence side, and the axial direction of the optical fiber core is determined from the temporal change in the backscattered light reaching the light incidence side. A method for measuring humidity, characterized in that the humidity distribution of the gas to be measured is determined along the following lines. 2. An optical fiber with a gas cladding structure in which the exposed optical fiber core is intermittently in contact with the gas to be measured whose humidity is to be measured; a light source that enters light into the optical fiber core; a light receiver for receiving the backscattered light returning to the light source; and a light branching means provided between the light source and the optical fiber for guiding the backscattered light to the light receiver; The humidity of the gas to be measured is determined from the intensity of the backscattered light detected by the light receiver, and the humidity of the gas to be measured along the axial direction of the optical fiber core is determined from the temporal change in the backscattered light reaching the light incident side. A humidity sensor comprising a signal processing circuit for determining humidity distribution. 3. The gas cladding structure has a small diameter portion that is fitted into the optical fiber core and a flow hole that allows the gas to be measured to flow, and a large diameter for forming a gas layer of the gas to be measured around the outer periphery of the optical fiber core. 3. The humidity sensor according to claim 2, wherein the humidity sensor is constituted by a corrugated tubular body comprising:
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP14678985A JPS629255A (en) | 1985-07-05 | 1985-07-05 | Measuring method for humidity and humidity sensor used for measuring method |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP14678985A JPS629255A (en) | 1985-07-05 | 1985-07-05 | Measuring method for humidity and humidity sensor used for measuring method |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS629255A JPS629255A (en) | 1987-01-17 |
| JPH0449905B2 true JPH0449905B2 (en) | 1992-08-12 |
Family
ID=15415572
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP14678985A Granted JPS629255A (en) | 1985-07-05 | 1985-07-05 | Measuring method for humidity and humidity sensor used for measuring method |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS629255A (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2716057B2 (en) * | 1989-03-24 | 1998-02-18 | 住友電気工業株式会社 | Optical fiber |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS523480A (en) * | 1975-06-27 | 1977-01-11 | Nippon Denso Co Ltd | Vapour and frost detecting device |
| JPS58190742A (en) * | 1982-04-30 | 1983-11-07 | Matsushita Electric Works Ltd | System for detecting humidity |
| JPS5992332A (en) * | 1982-11-17 | 1984-05-28 | アイ・テイ・テイ・インダストリ−ズ・インコ−ポレ−テツド | Moisture detector |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5476785U (en) * | 1977-11-09 | 1979-05-31 |
-
1985
- 1985-07-05 JP JP14678985A patent/JPS629255A/en active Granted
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS523480A (en) * | 1975-06-27 | 1977-01-11 | Nippon Denso Co Ltd | Vapour and frost detecting device |
| JPS58190742A (en) * | 1982-04-30 | 1983-11-07 | Matsushita Electric Works Ltd | System for detecting humidity |
| JPS5992332A (en) * | 1982-11-17 | 1984-05-28 | アイ・テイ・テイ・インダストリ−ズ・インコ−ポレ−テツド | Moisture detector |
Also Published As
| Publication number | Publication date |
|---|---|
| JPS629255A (en) | 1987-01-17 |
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