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An optical low-coherent interferometric technology for fiber Bragg grating (FBG) sensor array is described. A series of identical FBGs with low reflectivity form a sensor array. The first FBG of the array works as the reference FBG and the others work as sensing FBGs. Each sensing FBG and the reference FBG can form an in-fiber Fabry–Perot (F–P) interferometer with a specific cavity length. By scanning a home-made optical low-coherence reflectometry, the interference signals corresponding to different sensing FBGs (F–P interferometers) can be obtained and well distinguished. The mismatch in wavelength between the reference FBG and a sensing FBG induced by the measurand around this sensing FBG will cause the decrease of the intensity of the corresponding interference signal. A measurement of temperature is demonstrated and good performance is achieved. Factors limiting the total number of sensing FBGs are also discussed. 相似文献
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Fiber Bragg grating(FBG)is the most widely used optical fiber sensor due to its compact size,high sensitivity,and easiness for multiplexing.Conventional FBGs fa... 相似文献
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通过对光纤传感器进行设计,提出了一种基于变宽度悬臂梁的光纤(Bragg)光栅(FBG)流速传感器.传感部分由不锈钢材质的悬臂梁和粘贴在其特定位置上的FBG构成,悬臂梁采用等腰梯形和矩形相结合的外形结构设计,传感头两部分之间的衔接不需要用销子固定,整个传感头浑然一体,无额外附加重量,制作方法简易,且实验设置参考光栅,实验结果不受温度变化的影响.实验表明:传感器的Bragg波长漂移量与流速变化有很好的线性关系,传感器的灵敏度为0.025 m/s.可测流速范围为0~2 m/s,传感器不仅实现了对温度的补偿,而且提高了测量精度、灵敏度. 相似文献
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Brian P. CahillAuthor Vitae Raul LandAuthor Vitae Thomas NackeAuthor VitaeMart MinAuthor Vitae Dieter BeckmannAuthor Vitae 《Sensors and actuators. B, Chemical》2011,159(1):286-293
We present an electrode arrangement for the inline measurement of the conductivity of droplets in segmented flow by impedance spectroscopy. We use a thin-walled glass capillary with electrodes contacting the outer surface, so that the contactless measurement of conductivity of the liquid within the capillary is possible. The surface of the glass capillary is silanized resulting in a single hydrophobic surface across which droplets can freely move. We model the impedance of such insulated electrodes and use the model to optimize the electrode system. Measurement of solutions with various salt concentrations allows the performance of the electrode structure to be characterized. Subsequently, the measurement of the impedance response of the aqueous segments in two-phase flow was demonstrated. Measurements were firstly performed with an impedance analyzer and subsequently with a multi-sine measurement setup that is better suited to high-speed measurement of droplets. Previous electrical measurements of segmented flow sensed the difference in dielectric constant between the aqueous phase and the carrier fluid through measurement of capacitance. This work describes an electrical measurement of the conductivity of droplets in segmented flow, that is, the sensor senses a variable property of the droplet itself. 相似文献
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Generation of uniform-size droplets by multistep hydrodynamic droplet division in microfluidic circuits 总被引:1,自引:1,他引:0
A microfluidic system is presented to generate multiple daughter droplets from a mother droplet, by the multistep hydrodynamic
division of the mother droplet at multiple branch points in a microchannel. A microchannel network designed based on the resistive
circuit model enables us to control the distribution ratio of the flow rate, which dominates the division ratios of the mother
droplets. We successfully generated up to 15 daughter droplets from a mother droplet with a variation in diameter of less
than 2%. In addition, we examined factors affecting the division ratio, including the average fluid velocity, interfacial
tension, fluid viscosity, and the distribution ratio of volumetric flow rates at a branch point. Additionally, we actively
controlled the volume of the mother droplets and examined its influence on the size of the daughter droplets, demonstrating
that the size of the daughter droplets was not significantly influenced by the volume of the mother droplet when the distribution
ratio was properly controlled. The presented system for controlling droplet division would be available as an innovative means
for preparing monodisperse emulsions from polydisperse emulsions, as well as a technique for making a microfluidic dispenser
for digital microfluidics to analyze the droplet compositions. 相似文献
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Caglar ElbukenAuthor VitaeTomasz GlawdelAuthor Vitae Danny ChanAuthor VitaeCarolyn L. RenAuthor Vitae 《Sensors and actuators. A, Physical》2011,171(2):55-62
Detection of the presence, size and speed of microdroplets in microfluidic devices is presented using commercially available capacitive sensors which make the droplet based microfluidic systems scalable and inexpensive. Cross-contamination between the droplets is eliminated by introducing a passivation layer between the sensing electrodes and droplets. A simple T-junction generator is used to generate droplets in microchannels. Coplanar electrodes are used to form a capacitance through the microfluidic channel. The change in capacitance due to the presence of a droplet in the sensing area is detected and used to determine the size and speed of the droplet. The design of a single pair of electrodes is used to detect the presence of a droplet and the interdigital finger design is used to detect the size and speed of the droplet. An analytical model is developed to predict the detection signal and guide the experimental optimization of the sensor geometry. The measured droplet information is displayed through a Labview interface in real-time. The use of capacitance sensors to monitor droplet sorting at a T-junction is also presented. The discussions in this paper can be generalized to any droplet detection application and can serve as a guideline in sensor selection. 相似文献
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文章基于光纤布拉格光栅对温度、湿度等敏感的基础上,分析了以聚酰亚胺(PI)薄膜为湿敏涂层,当湿度变化时,由于涂层的膨胀,导致光纤布拉格光栅产生应变,从而对湿度传感。理论分析与实验证明,光纤布拉格光栅湿度传感器是一种性能良好的湿度传感器。 相似文献
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为了快速、准确地对气固两相流速度进行测量,介绍一种利用形态滤波和空间滤波处理气固两相流信号的基本方法,首先研究电容传感器的空间滤波效应,并找出固体速度和电容传感器带宽之间的关系.然后通过对一维形态滤波算法理论进行分析,推导出可用于实时运算的形态滤波方法,此方法具有处理速度快,滤波效果好,适用性广的特点,可应用于多种信号的实时处理中.然后利用形态滤波确定传感器的带宽,进而求出固体速度.最后给出仿真实验结果,仿真实验结果表明:该方法可以满足气固两相流速度的测量要求. 相似文献
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基于FBG的电力杆塔倾角传感器研究 总被引:2,自引:0,他引:2
电力杆塔监测对保证输电线路运行安全具有重要意义。对基于光纤Bragg光栅(FBG)的电力杆塔倾角传感器进行研究,底端固定于传感器外壳上的等强度悬臂梁自由端挂有重物,且在等强度悬臂梁两侧对称中心线上各粘贴一个FBG。电力杆塔发生倾斜时,重物带动等强度悬臂梁自由端产生挠度,使FBG产生中心波长移位,对中心波长进行监测即可实现杆塔倾斜角度测量。实验表明:测量小角度(小于15°)时,重复性误差为l%Fs,非线性误差为0.4%FS,滞后误差为0.8%FS;测量大角度(15°-45°)时,重复性误差为1.5%FS,非线性误差为0.77%FS,滞后误差为1.1%FS。 相似文献
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The characteristics of transmission spectra for the all fiber, multi-cavity Fabry- Perot (FP) configuration based on fiber Bragg gratings (FBG) are theoretically analyzed and modeled. The general transmission matrix function for the structure with any number of cavities is derived, and explicit expression of the power trans- mission coefficient for symmetrical two-cavity FP is presented. The general condi- tions for flat-top single resonant peak at the central wavelength in FBG stop band are derived and verified in the numerical simulation section. The transmission peaks of single-cavity and two-cavity FP structures are compared and discussed, and results show that compared to the single-cavity FP, flatness of the top and steepness at the edge of transmission peak can be improved by introducing one more cavity. The resonant transmission peak properties of two-cavity structure are investigated in detail for various values of cavity length and FBGs with different reflection characteristics, and the design guidelines for transmission-type filters are presented. The results show that the steepness of peak slope can be improved by increase of FBG reflectivities, and these kinds of filters can be used as nar- row-band single-channel selectors and multi-channel wavelength de-multiplexing by properly choosing the length of cavities and reflectivities of FBGs. 相似文献
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为定量分析压力传感器的测量量程及其过载能力,提出一种微型光纤光栅土压力传感器并构建其气压标定系统。对微型光纤光栅土压力传感器进行理论分析得其灵敏度为7.5 nm/MPa,测量量程可达1.06 MPa。而分析光纤光栅土压力传感器性能测试数据得:该传感器压力灵敏度为5.9 nm/MP,线性度为99.93%,可测量实际量程为225 kPa,过载能力上限值为300 kPa。研究结果可用于指导设计规定量程的光纤光栅土压力传感器,具备一定应用价值。 相似文献
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提出一种基于FBG(Fiber Bragg Grating)光纤光栅传感器实现皮革弹性测量中温度、因温度变化引起的皮革纤维受力变形长度变化量和拉伸力引起的皮革纤维受力变形长度变化量三个参数被测量。采用用宽夹子把皮革样品两端固定好,并把一个FBG1传感器固定在夹子上,并在沿皮革样品发生形变方向放置FBG2传感器来解决皮革弹性变形和温度相互交叉感染问题;同时采用镀层FBG来提高FBG传感器的灵敏度。实验表明,三个参数能被精确和同时测量;并且FBG传感器灵敏度也被提高了8~13倍。 相似文献
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为实现光纤光栅传感器胶接固定于桥梁缆索钢丝以监测缆索索力,利用胶接结构的剪切测试、钢丝疲劳测试和循环加卸载测试分别对光纤光栅传感器支座与钢丝间胶接结构的剪切性能、疲劳可靠性以及胶接光纤光栅传感器的测试性能进行评估.试验发现:光纤光栅传感器支座与桥梁缆索钢丝间的胶接结构具有较大的剪切载荷,且200万次疲劳载荷对其胶接结性能影响较小;胶接固定于钢丝上的光纤光栅传感器可测出钢丝加卸载的滞回效应,并每个循环加、卸载的波长和钢丝承载载荷关系呈线性且分别重合.结果表明:内置光纤光栅传感器的胶接固定结构具有良好的剪切力学性能和疲劳可靠性,可保证其光纤光栅传感器的测试具有良好的准确、稳定、可靠性. 相似文献
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Huei-Wen Wu Yen-Chang Huang Chao-Liang Wu Gwo-Bin Lee 《Microfluidics and nanofluidics》2009,7(1):45-56
This study presents a new microfluidic chip that generates micro-scale emulsion droplets for gene delivery applications. Compared
with conventional methods of droplet formation, the proposed chip can create uniform droplets (size variation <7.1%) and hence
enhance the efficiency of the subsequent gene delivery. A new microfluidic chip was developed in this study, which used a
new design with a pneumatic membrane chamber integrated into a T-junction microchannel. Traditionally, the size of droplets
was controlled by the flow rate ratio of the continuous and disperse phase flows, which can be controlled by syringe pumps.
In this study, a pneumatic chamber near the intersection of the T-junction channel was designed to locally change the flow
velocity and the shear force. When the upper air chamber was filled with compressed air, the membrane was deflected and then
the droplet size could be fine-tuned accordingly. Experimental data showed that using the new design, the higher the air pressure
applied to the active tunable membrane, the smaller the droplet size. Finally, droplets were used as carriers for DNA to be
transfected into the Cos-7 cells. It was also experimentally found that the size of the emulsion droplets plays an important
role on the efficiency of the gene delivery.
The preliminary results of this paper have been presented at the 2007 IEEE International Conference of Nano/Molecular Medicine
and Engineering (IEEE NANOMED 2007), Macau, China, 6–9 August, 2007. 相似文献
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Study of flow behaviors of droplet merging and splitting in microchannels using Micro-PIV measurement 总被引:1,自引:0,他引:1
Droplet merging and splitting are important droplet manipulations in droplet-based microfluidics. However, the fundamental flow behaviors of droplets were not systematically studied. Hence, we designed two different microstructures to achieve droplet merging and splitting respectively, and quantitatively compared different flow dynamics in different microstructures for droplet merging and splitting via micro-particle image velocimetry (micro-PIV) experiments. Some flow phenomena of droplets different from previous studies were observed during merging and splitting using a high-speed microscope. It was also found the obtained instantaneous velocity vector fields of droplets have significant influence on the droplets merging and splitting. For droplet merging, the probability of droplets coalescence (η) in a microgroove is higher (50% < η < 92%) than that in a T-junction microchannel (15% < η < 50%), and the highest coalescence efficiency (η = 92%) comes at the two-phase flow ratio e of 0.42 in the microgroove. Moreover, compared with a cylinder obstacle, Y-junction bifurcation can split droplets more effectively and the droplet flow during splitting is steadier. The results can provide better understanding of droplet behaviors and are useful for the design and applications of droplet-based microfluidics. 相似文献