外文翻译-基于塑料光纤的液位计

附录A:外文文献及翻译Liquid level gauge based in plastic optical ber 1.IntroductionThe accurate liquid level measurement in large indus- trial containers is a difcult task, especially for highly am- mable environments, where the use of electronic sensors can be problematical, or even banned by law, due to the risk of electric sparkle.Nowadays, the petroleum and other petrochemical industries have specic and tight requirements related with the production quantication. Such as the require- ment to quantify the production volume, by inferring the liquid level in the container (typically with some meters height). This requirement is not only an individual compa- ny requirement, to control the company production ef- ciency and gains, but also a legal imposition to estimate scal taxes 1. Usually, the liquid level in the container is measured by traditional technologies, such as differen-tial pressure level meters, radar, magnetostrictive, or mag- netic oat technologies 2,3. However, some limitation may apply, since such methods are electronic and the sens- ing system is often exposed to combustible liquids or accu- mulated ammable vaporous environments. Therefore, the liquid level measurement in the petroleum industry appears as a window of opportunity for the use of optical technology.Nowadays, the main technological characteristics used for liquid level measurement, are capacitive, ultrasonic or hydrostatic 4,5. Optical technologies are also gaining position among those sensors, mainly due to the immunity to electromagnetic interference, the inexistence of electri- cal signal at the sensor head, the possibility of remote sens- ing and the compactness. Recently, several solutions had being proposed for the measurement of liquid level, such as based on long period gratings 6, ber Bragg gratins 7,8 or LIDAR systems 9.Usually, the main disadvantage of all these sensing solutions is the high implementation cost, resulting from the requirement of the interrogation unit. To overcome this disadvantage, polymeric, or plastic optical bers (POF) are already being used in numerous types of sensors, such asphysical sensors (elongation, acceleration or pressure) 10,11, chemical biosensors or in specic applications, such as to monitor concrete curing process These sensors can be potentially less expensive than the conventional electronic sensors and more robust than the produced with silica optical bers Several level sensors based on polymeric optical ber have been proposed in the last few years. Lomer et al. demonstrate a U polished bended POF sensor head to measure the liquid level in a container . A discrete sen- sor was tested with bended polished POF sensing heads, the sensitivity was quantied through the optical signal atten- uation change in each bend, 0.26 dB, per sensing point immersed in water. The resolution can be tailored to each application, by changing the distance between each bend.Azimi et al. showed an arrangement to measure the optical signal coupled via the evanescent electromagnetic eld between two bers placed close to each other, impos- ing an intensity modulation on the signal in the acceptance ber when a liquid is to be found between the bers This modulation mechanism was related with the refrac- tive index of the surrounding medium. The sensor was tested as a liquid level sensor for different liquids and a sig- nal contrast of 4.5% was measured when the sensor head was moved from air to water.Montero and Vzquez demonstrated an intensity based POF sensor for liquid detection in volumetric asks, nor- mally used in chemistryIn the developed platform, light was launched from a ber illuminating the volumet- ric ask and received into a ber placed at the same longi- tudinal axes. The system presented diverse sensitivities due to the increasing reected light from uids surface when it rises. An optical power variation of 9.6 dB in the receiver was noticed when the liquid completely blocks the acceptance area of the receiver ber, and most light is reected on the liquid surface.Bottacini et al. proposed a POF sensor for point mea- surement, working like a retro-reecting prism The sensor detects the presence of different liquids by measur- ing the intensity variation of a green-light signal, back-re- ected by special tip-shaped ber probes with 90 and 60 angled tips. The back-reected optical signal decreases when the tip is immersed in water (or in other high RI liquids).In the work here presented we proposed a novel level sensor based on POFs. This allows the combination of the optical technology advantages with the lower cost of the interrogation technique, providing a solution, for harsh or hazard environments. The proposed sensor is based on a periodic indentation on the polymeric ber core. Each groove disturbs the propagation of optical signal and induces an increase in the optical signal attenuation. The amount of optical radiation loss depends on the external environment surrounding the grooves and on its dimen- sion. Thus, any external disturbance to the surrounding environment produces a measurable effect on the signal optical power at the ber output. Comparing the proposed solution with other previously reported, such as in refer- ences , although the detection scheme could be similar, the sensor here proposed is simpler and cheaper to manufacture and its assembly in the measuring eldeasier, because it uses one stretched ber, without bending or sensing heads. Bended and polished bers, such in are also more susceptible to failure due to internal stresses in the curvature, furthermore each bending increases a xed term of attenuation that might considerably decrease the measuring range. A sensing head, such in may add alignment complexity to the sensor manufacturing and stability during operation. The sensor referenced incannot make level measurements with one ber, and also requires a more complex manufacturing process.This paper is organized as follows: after an introduction, reporting the relevance of such optical sensors, the devel- oped sensors are introduced in section 2, with the descrip- tion of the manufacturing process and its working principle. Section 3 deals with the sensors experimental characterization. Finally, the main conclusions are drawn in section 4.2. Sensor description and manufacturingAs already mentioned, the presence of a groove in the core of an optical ber disturbs the propagation of the opti- cal signal, resulting in an optical signal leakage to the exte- rior of the ber, thereby interacting with the surrounding environment. Considering that the refractive index (RI) of the surrounding medium is equal to the POF core RI, the ber and the surrounding environment can be considered as continuous medium. Therefore the optical signal leak- age is minimum and the transmitted optical power is max- imum. If the surrounding medium have an RI that differ the POF one, then the optical power leakage increase and the transmitted signal power decreases. Considering that the liquid refractive index does not change during the mea- surements and have an intermediate value ( 1.33) between the air RI ( 1.00) and the POF core RI ( 1.46), then, each time a groove is fullled, the transmitted optical power increase due to the reduction of the optical power leakage. The amount of radiation lost to the outside depends on the bers external environment, the dimen- sions of the grooves and its depth.Using the POF ber with the engraved grooves, placed perpendicularly to the liquid surface, when the liquid rises it will sequentially fulll each groove, and consequently increase the transmitted optical power. In is dis- played the optical signal leakage through the grooves engraved in a POF.To produce the grooves in the plastic optical ber a brass mold was manufactured (, which allows, in conjugation with a sharp blade, to engraving the groves with a high repeatability and accuracy. This mold was designed to produce grooves with a depth of one quarter or one half of the ber core diameter, with a minimum groove spacing of 1 cm.To demonstrate the feasibility of the proposed solution three illustrative sensors were implemented in a large dia- meter core (1 mm) plastic optical ber from Avago Tech- nologies (HFBR-RUS100Z), with the number of grooves, depth and dimensions outlined .Temperature inuence and LED stability have a prepon- derant effect on the measurements, however, those effectsFig. 1. Photograph showing a plastic optical ber with grooves depicting the optical signal leakage for a blue optical signal. (For interpretation of the references to colour in this gure legend, the reader is referred to the web version of this article.)Fig. 2. (a) Photograph of the brass mold used to create the grooves into the ber ) scheme of a plastic ber groove.3.CharacterizationFig. 3 shows the experimental setup schematics and the photography of the interrogation unit. The interroga- tion unit has 4 independent red LEDs (peaking at 660 nm, model IF-E96 from Industrial Fiber Optics Inc), and 4 pho- todiode (model FB120-ND from Industrial Fiber Optics Inc) followed by an electrical transimpedance amplication stage with controlled gain. The control module uses a 16-bit microcontroller (model PIC24FJ256DA206 from Microchip Technologies) with a 16-bit ADC, which operates in a range from 0 to 2.5 V, resulting in a resolution of38.15 lV. The amplier gain and the ADC input voltage range were optimized in order to maximize the overall resolution.The acquisition module can be controlled remotely via a wireless system (module MiWi P2P from Microchip Technologies), paired with a computer or through a USB cable connection, where the data acquisition and analysis is performed in real time using a Labview application. The system also comprises a battery for eld monitoring and the capability of record data to an SD card.For the sensor head preparation a plastic optical ber was connected to the optical source and to the receiver. Then the grooves were sliced on the ber and simultane- ously the optical power transmitted in the ber monitored in real time as a function of the number of grooves, shown in 4, where is observed a decrease in the optical signal power, due to the signal leakage, with the increase of the number of grooves.As expected, sensor 3, which present higher grooves depth imposes a higher optical signal loss per groove. For sensors 1 and 2, although the groves are produced at differ- ent spacing on the POF, they present a similar optical loss per groove, due to the similar depth and to the low propagation attenuation (0.2 dB/m).An average optical power loss of 3.4 0.2% is noticed on the transmitted signal, for each sliced groove, for sensors 1 and 2. For sensor 3 the average optical power loss was7.5 0.2% per groove .This optical power decrease of 3.4% (sensors 1 and 2) corresponds to an average of 1744 discrete levels of the used 16 bits ADC of the interrogation unit. Furthermore, the maximum number of grooves for which the signal to noise ratio is higher can be extended using several strate- gies, like increasing the power of the optical source, the ADC resolution or the electric amplier gain.The implemented sensors were tested by measuring the level in two containers lled with distilled water, as shown , with a maximum height of 50 cm for sen- sor 1 and 200 cm for sensors 2 and 3. The POF was xed to a PVC (Polyvinyl chloride) tube which remains xed and taut along the recipient.The experimental data collected by raising the level of water in the reservoir are shown in The normaliza- tion was attained considering as a reference the initial optical power measured without any liquidFig. 3. (a) Experimental setup block diagram and photographs of the interrogation unit: (b) front view, (c) inside view and (d) back viewAs the water column rises, the grooves are successively lled and the transmitted signal optical power increases. The sensitivity of sensor 1, in this case by linear t to the data of , is an increase of 0.74 0.01%/cm (1.44%/groove) of its initial value.The sensitivities of the implemented sensors are pre- sented on through the tting to the experimental data represented on The sensitivities value corre-photodetector, the length of the POF (due to the optical attenuation) and the number and depth of the grooves. The resolution is related with the distance between the produced grooves and can be improved by decreasing this distance, which may require the compensation for the reduction of optical power if a larger measurement range is required. This compensation may be accomplished by increasing the power of the optical source or by reducing the depth of the grooves. In any case, the properties of the sensor may be tailored to the application requirements.Monitoring liquids level in medium to large containers on highly ammable environments, wherever the use ofelectronic sensors can be problematical, is where the pro- posed sensor main advantages are fully used. Among many of such applications are: oil pipelines monitoring, oil dril- ling or fuel tanks. Nevertheless, because the proposed scheme is a low cost solution, it can also be used cost-ef- fectively with non-ammable liquids, on the monitoring of groundwater or water reservoirs level, among numerous other simpler applications. Although the sensor was not tested for higher refractive index liquids, as long as the liq- uid refractive index differs from the POF core one, it will be observed a change on optical power leakage from the groove to the exterior.Usually, the level sensors can be classied into two groups, continuous and discrete. The sensor here proposed can be classied as discrete. However, since is a low cost solution it can be deployed as a quasi-continuous solution, which can be employed with multiplexing techniques, such as the one presented by Hopenfeld using a low cost digital camera and an image processing software . Nev- ertheless, POF based sensors can only be operated in the proximity of the interrogation system, due to the high opti- cal signal attenuation on the POF itself. For long-distance remote monitoring, with sensors positioned up to 50 km away from the acquisition system, silica ber Bragg grating based sensors are appropriated, using remote interrogation techniques, such the one presented by Fernandez-Vallejo et al. .4.ConclusionA polymeric optical ber intensity based level sensor was presented, being an appropriated solution to be usedinto highly ammable liquids reservoirs without risk, such in oil piping or fuel tanks. A suitable sensitivity for the test- ed versions was obtained; the number of grooves and the distance between them dene the sensing resolution. Still, the sensor sensitivity and resolution can be tailored for several applications. Although several electronic or/and optical sensors had been already reported previously with higher resolution on the level monitoring, comparing to the reported solution, this POF based sensor present quite a few advantages on medium to large containers level monitoring, such on the simplicity, production and interro- gation cost.Three sensor versions were implemented and experimentally characterized, with different groove depths and spacing, demonstrating the sensor adaptability to the container dimensions. For these versions, a sensitivity based on the variation relatively to the initial transmitted optical power of 1.48%, 2.20% and 2.60% was detected per each liquid fullled groove.We have implemented a level sensor, based on the pro- cedure described, with possible application in, among many, the monitoring of groundwater tablet levels, soil moisture monitoring in agriculture and liquid level in tanks of ammable substances.AcknowledgementsThis work was nanced in the scope of UID/EEA/50008/ 2013, by FCT/MEC through national funds and FEDER PT2020 partnership agreement. Paulo Antunes acknowl- edge Fundao para a Cincia e Tecnologia (FCT) for the Postdoctoral fellowship SFRH/BPD/76735/2011. EsequielMesquita acknowledge CAPES through the fellowship number 10023/13-5, Fundao CAPES, Ministrio da Educao do Brasil.Reference D.W. Spitzer, S.B. LLC, Lasers come to level measurement, (2006, July 11, 2013) . K. Peters, Polymer optical fibre sensors a review, Smart Mater. Struct. 20 (1) (2011).P.F.C. Antunes, H. Varum, P.S. Andre, Intensity-encoded polymer optical fiber accelerometer, Sens. J., IEEE 13 (2013) 17161720. J. Zubia, J. Arrue, Plastic optical fibers: an introduction to their technological processes and applications, Opt. Fiber Technol. 7 (2001) 101140. R.J. Bartlett, R. Philip-Chandy, P. Eldridge, D.F. Merchant, R. Morgan, P.J. Scully, Plastic optical fibre sensors and devices, Trans. Inst. Meas. Control 22 (2000) 431457. A. Varriale, A. Pennacchio, M. Staiano, D. Massarotti, L. Zeni, S. DAuria, An innovative plastic optical fiber-based biosensor for new bio/applications. The case of celiac disease, Sens. Actuators, B: Chem. 176 (2013) p. 7. P.S. Andr, H. Varum, P. Antunes, L. Ferreira, M.G. Sousa, Monitoring of the concrete curing process using plastic optical fibers, Measurement 45 (2012) 556560. P. Antunes, H. Lima, J. Monteiro, P.S. Andr, Elastic constant measurement for standard and photosensitive single mode optical fibres, Microwave Opt. Technol. Lett. 50 (2008) 24672469.M. Lomer, J. Arrue, C. Jauregui, P. Aiestaran, J. Zubia, J.M. LpezHiguera, Lateral polishing of bends in plastic optical fibres applied to a multipoint liquid-level measurement sensor, Sens. Actuators, A 137 (2007) 6873. P. Azimi, Design and performance of a plastic optical fiber leakage sensor, Opt. Laser Technol. 39 (2007) p. 5. D.S. Montero, C. Vzquez, Polymer optical fiber intensity-based sensor for liquid-level measurements in volumetric flasks for industrial 基于塑料光纤的液位计摘要 本文介绍了一种低成本塑料光纤液位传感器的研制与试验。在高度易燃或其他危险环境中，如油管或油箱。该传感器包括一个垂直的刻度槽，当液体上升时，刻痕凹槽将连续地充满，从而增加了透射光功率。每个测量点获得透射光功率强度的2.60%的变化。此外，传感器的灵敏度和分辨率可以根据应用来定制。1、引言 在大型工业容器中，准确的液位测量是一项艰巨的任务，特别是对于高度敏感的环境，由于电火花的危险，电子传感器的使用可能是有问题的，甚至被法律所禁止。 目前，石油和其他石油化工行业对生产数量有着特殊的要求和严格的要求。如要求量化生产量，通过推断容器内的液位（通常有几米高度）。这一要求不仅是一个单独的综合要求，是控制公司生产效率和收益，而且是一个法定的征收增值税（1）。通常，容器中的液位是用传统的技术来测量的，例如：TiAl压力水平计、雷达、磁致伸缩或MAG - NoTi-OAT技术2,3。然而，一些限制可能适用，因为这样的方法是电子的，传感系统经常暴露于可燃液体或复杂的易燃的蒸气环境中。因此，石油工业中的液位测量作为使用光学技术的机会窗口。目前，液位测量的主要技术特点是电容式、超声波式或静压式4，5。光学技术也在这些传感器中占有重要地位，主要是由于对电磁干扰的免疫力、传感器头上不存在电信号、远程传感的可能性和紧凑性。最近，已经提出了几种解决液位测量的方法，如基于长周期光栅（6）、布拉格Balger-Galin 7、8或LiDAR系统9 。 通常，所有这些检测方案的主要缺点是高的实施成本，这是由于询问单元的要求。为了克服这一缺点，聚合物或塑料光学纤维（POF）已经在许多类型的传感器中被使用，例如物理传感器（伸长，加速或压力）10，11，化学12，13，生物传感器14或在特殊用途中，例如监测混凝土固化过程15。这些传感器可能比传统的电子传感器便宜，并且比用二氧化硅光学材料11，16生产的更可靠。近年来，人们提出了基于聚合物光纤的几种传感器。洛默等。演示一种“U”抛光弯曲的POF传感器头来测量容器中的液位17。用弯曲抛光POF传感头对离散传感器进行测试，通过光信号在每个弯曲处的变化，0.26分贝，浸入水中的每个传感点对灵敏度进行定量。可以通过改变每个弯曲之间的距离来为每个应用定制分辨率。阿齐米等人。示出了一种测量光学信号的装置，所述光学信号通过两个彼此靠近的两个BER之间的倏逝电磁场耦合，从而在在BER（18）之间找到液体时接受信号中的信号强度调制。这种调制机制与周围介质折射率有关。该传感器被测试为不同液体的液位传感器，当传感器头从空气移动到水时测量4.5%的对比度。蒙特罗和Vaz ZQuz演示了一种基于容量的POF传感器，用于体积检测中的液体检测，也不用于化学（19）。在所研制的平台中，光从一个光照器发射，并照射到同一个长轴上。该系统在UID表面上升时，由于光线的增加而呈现出不同的灵敏度。当液体完全阻断接收器BER的接收面积时，注意到接收器中的光功率变化为9.6分贝，并且大部分光被重新照射在液体表面上。BATACI等。提出了一种点阵式传感器，其工作原理类似于复式棱镜（20）。该传感器通过测量绿光信号的强度变化来检测不同液体的存在，用90和60角尖端的特殊尖端形状的BER探头重新检测。当端部浸入水中（或在其它高RI液体中）时，背向光信号减小。在本文的工作中，我们提出了一种基于PoF的新型液位传感器。这使得光学技术的优点与询问技术的低成本相结合，为恶劣或危险的环境提供了解决方案。所提出的传感器基于聚合物BER芯上的周期压痕。每个凹槽干扰光信号的传播，并引起光信号衰减的增加。光辐射损失量取决于沟槽周围的外部环境及其变化。因此，对周围环境的任何外部干扰对信号输出的信号光功率产生了可测量的影响。将所提出的解决方案与先前报道的其他方案进行比较，如参考文献1720，虽然检测方案可以类似，但是这里提出的传感器更简单、更便宜，并且在测量领域中的组装。更容易，因为它使用一个拉伸弯曲，没有弯曲或传感头。弯曲和抛光的BER，如在17 中，由于曲率中的内应力也更容易受到破坏，而且每一弯曲都增加了一个固定的衰减项，这可能大大降低测量范围。感测头，如在18.19中，可以增加传感器制造过程中的对准