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papers from the latest issue:
Long-gage optical fiber extensometers for dynamic evaluation of structures
13 August 2012,
09:38:31
Publication year:
2012
Source:Sensors and Actuators A: Physical, Volume 184
G. Cumunel, S. Delepine-Lesoille, P. Argoul
This paper deals with the study of the capacity of continuously attached long-gage fiber optic sensors for a new use: dynamic evaluation of structures. The optical system is first presented, followed by the development of the precise formulation of the measurement data obtained by this sensor when applied to the dynamic analysis of beams, especially under bending oscillations. This sensor allows us to find the curvature mode shapes. Numerical simulations are then performed to estimate the dynamic characteristics of the beam by means of the continuous wavelet transform, using the data obtained with this sensor. Finally, the fiber optic sensors are bonded on a real cantilever beam and experimental data are collected from the optical measurement system, in the case of aftershock free oscillations of the instrumented beam. A similar modal identification procedure as that proposed for numerical simulations is used and the results are compared to those obtained with accelerometers and long strain gauges. This type of sensor, allowing us to find the curvature mode shapes, will be a good candidate for damage detection.
Source:Sensors and Actuators A: Physical, Volume 184
G. Cumunel, S. Delepine-Lesoille, P. Argoul
This paper deals with the study of the capacity of continuously attached long-gage fiber optic sensors for a new use: dynamic evaluation of structures. The optical system is first presented, followed by the development of the precise formulation of the measurement data obtained by this sensor when applied to the dynamic analysis of beams, especially under bending oscillations. This sensor allows us to find the curvature mode shapes. Numerical simulations are then performed to estimate the dynamic characteristics of the beam by means of the continuous wavelet transform, using the data obtained with this sensor. Finally, the fiber optic sensors are bonded on a real cantilever beam and experimental data are collected from the optical measurement system, in the case of aftershock free oscillations of the instrumented beam. A similar modal identification procedure as that proposed for numerical simulations is used and the results are compared to those obtained with accelerometers and long strain gauges. This type of sensor, allowing us to find the curvature mode shapes, will be a good candidate for damage detection.
Highlights
► Study of the capacities of the continuously attached long-gage fiber optic sensor. ► Proper formulation of the measurement performed by this new sensor. ► Use of the continuous wavelet transform for modal analysis of the transient responses. ► Obtainment of the curvature mode shapes. ► Comparison of results with those obtained by more classical sensors.A robust pressure sensor for harsh environmental applications
13 August 2012,
09:38:31
Publication year:
2012
Source:Sensors and Actuators A: Physical, Volume 184
S. Fricke, A. Friedberger, H. Seidel, U. Schmid
Due to economical and environmental requirements there is a strong need both to increase the efficiency and to monitor the actual status of gas turbines, rocket engines and deep drilling systems. For these applications a micromachined pressure sensor based on a sapphire body and a platinum thin film metallization is presented to withstand harsh environments such as high temperature levels, aggressive media and/or high pressure loads. For pre-evaluation purposes, a reusable packing is used enabling the device characterization in a very efficient way up to temperatures of 440°C and pressures of 30bar, respectively. As expected, the output signals of the Wheatstone bridge increase with higher pressures, but decrease with enhanced temperature levels. Furthermore, these characteristics show a sensitivity of about 10μV/(Vbar) in this temperature range and a negative drift in the offset when no pressure load is applied with increasing temperature. This effect is predominantly caused by the mismatch of the temperature coefficients of expansion associated with the device and the housing leading to a pre-stressed membrane.
Source:Sensors and Actuators A: Physical, Volume 184
S. Fricke, A. Friedberger, H. Seidel, U. Schmid
Due to economical and environmental requirements there is a strong need both to increase the efficiency and to monitor the actual status of gas turbines, rocket engines and deep drilling systems. For these applications a micromachined pressure sensor based on a sapphire body and a platinum thin film metallization is presented to withstand harsh environments such as high temperature levels, aggressive media and/or high pressure loads. For pre-evaluation purposes, a reusable packing is used enabling the device characterization in a very efficient way up to temperatures of 440°C and pressures of 30bar, respectively. As expected, the output signals of the Wheatstone bridge increase with higher pressures, but decrease with enhanced temperature levels. Furthermore, these characteristics show a sensitivity of about 10μV/(Vbar) in this temperature range and a negative drift in the offset when no pressure load is applied with increasing temperature. This effect is predominantly caused by the mismatch of the temperature coefficients of expansion associated with the device and the housing leading to a pre-stressed membrane.
Research on fiber optic temperature sensor using a novel high-birefringent fiber loop mirror with a reflection probe
13 August 2012,
09:38:31
Publication year:
2012
Source:Sensors and Actuators A: Physical, Volume 184
Yong Zhao, Ting-ting Song, Di Wu, Qi Wang
Based on the two structures of the high-birefringent fiber loop mirror (Hi-Bi FLM) with reflection probe, the relevant principles are carried out and experiments are performed to prove the principles. Temperature properties of one structure, known as the FLM with the Hi-Bi reflection probe, are experimentally studied. The temperature sensitivity is 1.698nm/°C with good linearity, thus the temperature resolution can reach the scale of 0.04°C in theory if the resolution of the optical spectrum analyzer (OSA) is 0.02nm. Besides, the temperature range can be tuned by different length or birefringence of the Hi-Bi fiber. Since the reflection probe is one output of the Hi-Bi FLM, the structure can be used for the high sensitivity remote temperature sensing.
Source:Sensors and Actuators A: Physical, Volume 184
Yong Zhao, Ting-ting Song, Di Wu, Qi Wang
Based on the two structures of the high-birefringent fiber loop mirror (Hi-Bi FLM) with reflection probe, the relevant principles are carried out and experiments are performed to prove the principles. Temperature properties of one structure, known as the FLM with the Hi-Bi reflection probe, are experimentally studied. The temperature sensitivity is 1.698nm/°C with good linearity, thus the temperature resolution can reach the scale of 0.04°C in theory if the resolution of the optical spectrum analyzer (OSA) is 0.02nm. Besides, the temperature range can be tuned by different length or birefringence of the Hi-Bi fiber. Since the reflection probe is one output of the Hi-Bi FLM, the structure can be used for the high sensitivity remote temperature sensing.
Highlights
► A new fiber sensor structure was proposed based on the high-birefringent fiber loop mirror with reflection probe. ► The relevant principles are carried out and experiments are performed to prove the principles of the new structure. ► This kind structure is useful for the high sensitivity remote temperature sensing. ► The temperature sensitivity is 1.698nm/°C with good linearity, thus the temperature resolution can reach the scale of 0.04°C in theory if the resolution of the optical spectrum analyzer (OSA) is 0.02nm. ► Besides, the temperature range can be tuned by different length or birefringence of the Hi-Bi fiber.Research on the lift-off effect of generating longitudinal guided waves in pipes based on magnetostrictive effect
13 August 2012,
09:38:31
Publication year:
2012
Source:Sensors and Actuators A: Physical, Volume 184
Jiang Xu, Zhiyuan Xu, Xinjun Wu
Non-contact and large lift-off are the advantages of the magnetostrictive guided waves. The lift-off of the excitation coil has direct effect on the generating waves and the receiving signals, because it reduces the alternating magnetic field strength on the pipe surface. The lift-off effect of generating longitudinal mode guided waves in pipes based on magnetostrictive effect is investigated in this paper. The formulation model of generating longitudinal guided waves in pipes based on magnetostrictive effect is obtained from the magnetostrictive theory and the electromagnetic theory. The relation between the alternating magnetic field strength and the lift-off distances of the excitation coil is obtained. And the model is verified by experiment. The results indicate that the detection sensitivity will be decreased with the excitation coil lift-off distance increasing. Furthermore, the model provides the theoretical basis to compensate the lift-off effect of the excitation coil.
Source:Sensors and Actuators A: Physical, Volume 184
Jiang Xu, Zhiyuan Xu, Xinjun Wu
Non-contact and large lift-off are the advantages of the magnetostrictive guided waves. The lift-off of the excitation coil has direct effect on the generating waves and the receiving signals, because it reduces the alternating magnetic field strength on the pipe surface. The lift-off effect of generating longitudinal mode guided waves in pipes based on magnetostrictive effect is investigated in this paper. The formulation model of generating longitudinal guided waves in pipes based on magnetostrictive effect is obtained from the magnetostrictive theory and the electromagnetic theory. The relation between the alternating magnetic field strength and the lift-off distances of the excitation coil is obtained. And the model is verified by experiment. The results indicate that the detection sensitivity will be decreased with the excitation coil lift-off distance increasing. Furthermore, the model provides the theoretical basis to compensate the lift-off effect of the excitation coil.
Highlights
► We obtain the formulation model of generating longitudinal guided waves in pipes based on magnetostrictive effect. ► We obtain the lift-off effect of the transmitter. ► We verify the model by experiment. ► The model could be applied to compensate the lift-off effect of the transmitter.Surface acoustic wave ultraviolet detector based on zinc oxide nanowire sensing layer
13 August 2012,
09:38:31
Publication year:
2012
Source:Sensors and Actuators A: Physical, Volume 184
Wenbo Peng, Yongning He, Changbao Wen, Ke Ma
The surface acoustic wave (SAW) ultraviolet (UV) detector based on zinc oxide (ZnO) nanowire sensing layer was developed and fabricated in this paper. To improve the SAW device's response characteristics, inter-digital transducers (IDTs) apodized by Morlet wavelet function and multiple couplers (MSC) were applied. ZnO nanowire materials were synthesized by Zinc thermal evaporation method. The ZnO nanowire sensing layer was coated onto the propagating area of the SAW devices, namely the sensing area, by transfer method as well as the multi-crystal ZnO sensing layer was deposited onto another device by magnetron sputtering for comparison. It was found that ZnO nanowire layer itself shows enhanced UV photoelectric response characteristics compared to sputtered ZnO film layer, which is acquired by characterizing their optical and photoelectrical properties. Under illumination of a UV light source, central frequency shifts of the two UV detectors were measured. An average central frequency shift of over 65kHz of the UV detector based on ZnO nanowire layer was observed under 150μW/cm2 365nm illumination for several on–off cycles while the one of the other detector was only about 8kHz. Moreover, the results indicate that the ZnO nanowire layer based SAW UV detector has good stability and repeatability. This kind of SAW UV detector with high sensitivity presents the potential for practical UV detection applications.
Source:Sensors and Actuators A: Physical, Volume 184
Wenbo Peng, Yongning He, Changbao Wen, Ke Ma
The surface acoustic wave (SAW) ultraviolet (UV) detector based on zinc oxide (ZnO) nanowire sensing layer was developed and fabricated in this paper. To improve the SAW device's response characteristics, inter-digital transducers (IDTs) apodized by Morlet wavelet function and multiple couplers (MSC) were applied. ZnO nanowire materials were synthesized by Zinc thermal evaporation method. The ZnO nanowire sensing layer was coated onto the propagating area of the SAW devices, namely the sensing area, by transfer method as well as the multi-crystal ZnO sensing layer was deposited onto another device by magnetron sputtering for comparison. It was found that ZnO nanowire layer itself shows enhanced UV photoelectric response characteristics compared to sputtered ZnO film layer, which is acquired by characterizing their optical and photoelectrical properties. Under illumination of a UV light source, central frequency shifts of the two UV detectors were measured. An average central frequency shift of over 65kHz of the UV detector based on ZnO nanowire layer was observed under 150μW/cm2 365nm illumination for several on–off cycles while the one of the other detector was only about 8kHz. Moreover, the results indicate that the ZnO nanowire layer based SAW UV detector has good stability and repeatability. This kind of SAW UV detector with high sensitivity presents the potential for practical UV detection applications.
Upside down T-shape through-wafer interconnects for fully tileable photodiode matrix for medical CT imaging
13 August 2012,
09:38:31
Publication year:
2012
Source:Sensors and Actuators A: Physical, Volume 184
Mikko Juntunen, Fan Ji, Iiro Hietanen, Simo Eränen
This paper presents a technology of a fully tileable two-dimensional photodiode matrix for medical imaging, specifically X-ray Computed Tomography (CT). A key trend in the CT industry is to build imaging devices with ever larger area detectors to speed up the measurements and to avoid image blurring due to patient movement. If individual slices have been taken at different points of time, the patient may have moved. The reconstruction accuracy suffers, resulting into blurred or distorted images. This can be avoided by increasing the amount of slices recorded in single rotation, up to the length of the whole object to be imaged. In most of the current CT detector constructions the characteristic pitch of the photodiodes is ∼1mm with 16×16 to 16×32 photodiodes on one chip. A major limiting factor in providing more detector coverage is the need to read out the signals from the individual photodiode elements of the photodiode matrix through metal lines between the photodiode elements along the surface facing the radiation source, and wire bonds down to a substrate or to an electronics chip. With this method, there is a physical limitation on the size of a photodiode matrix that may be manufactured. A detector with the possibility of active area expansion is known as a ‘tileable’ detector. Various technologies have been proposed to realize a tileable detector, all having their specific limitations. An improved technology of integrating T-shaped through-wafer interconnects within traditional front illuminated photodiodes is introduced, overcoming most of the limitations of the other tileable technologies. Photocurrent signal can be read out from back side of the chip through these interconnects, giving possibility of constructing arbitrarily large area of photodiode matrix. Results of an actual CT detector photodiode manufactured with this technology are presented showing that the requirements of modern CT systems can be met.
Source:Sensors and Actuators A: Physical, Volume 184
Mikko Juntunen, Fan Ji, Iiro Hietanen, Simo Eränen
This paper presents a technology of a fully tileable two-dimensional photodiode matrix for medical imaging, specifically X-ray Computed Tomography (CT). A key trend in the CT industry is to build imaging devices with ever larger area detectors to speed up the measurements and to avoid image blurring due to patient movement. If individual slices have been taken at different points of time, the patient may have moved. The reconstruction accuracy suffers, resulting into blurred or distorted images. This can be avoided by increasing the amount of slices recorded in single rotation, up to the length of the whole object to be imaged. In most of the current CT detector constructions the characteristic pitch of the photodiodes is ∼1mm with 16×16 to 16×32 photodiodes on one chip. A major limiting factor in providing more detector coverage is the need to read out the signals from the individual photodiode elements of the photodiode matrix through metal lines between the photodiode elements along the surface facing the radiation source, and wire bonds down to a substrate or to an electronics chip. With this method, there is a physical limitation on the size of a photodiode matrix that may be manufactured. A detector with the possibility of active area expansion is known as a ‘tileable’ detector. Various technologies have been proposed to realize a tileable detector, all having their specific limitations. An improved technology of integrating T-shaped through-wafer interconnects within traditional front illuminated photodiodes is introduced, overcoming most of the limitations of the other tileable technologies. Photocurrent signal can be read out from back side of the chip through these interconnects, giving possibility of constructing arbitrarily large area of photodiode matrix. Results of an actual CT detector photodiode manufactured with this technology are presented showing that the requirements of modern CT systems can be met.
Development of a mirror mounted fiber optic inclinometer
13 August 2012,
09:38:31
Publication year:
2012
Source:Sensors and Actuators A: Physical, Volume 184
Yeon-Gwan Lee, Hong-Kyu Jang, Dae-Hyun Kim, Chun-Gon Kim
A fiber optic inclinometer enables long distance transmission in hazardous environments without signal loss. This paper presents a wide measurement range fiber optic inclinometer for a stable sensing principle and simple sensor structure, which were realized using a single transmissive grating panel, reflective mirror, and optical fibers as transceivers. In comparison with the conventional transmission type fiber optic inclinometer design, the proposed scheme's cable design was simplified by 50%. The variation curve of the gravity-referenced static acceleration, measured using the proposed fiber optic inclinometer, was sinusoidal and it was compared with actual gravitational acceleration. The developed inclinometer featured nonlinear sensitivities of 1.97°/rad (90–75°), 2.19°/rad (75–60°), 2.49°/rad (60–45°), 3.23°/rad (45–30°), 5.84°/rad (30–15°), and 10.42°/rad (15–0°) according to the measurement range. The maximum absolute error, which was analyzed at 5° intervals, was 0.96° in the full scale measurement range (−90° to 90°). In the full scale range, the R-square value was 0.9999 between the measured and actual tilt angles based on linear regression analysis, and it demonstrated good agreement.
Source:Sensors and Actuators A: Physical, Volume 184
Yeon-Gwan Lee, Hong-Kyu Jang, Dae-Hyun Kim, Chun-Gon Kim
A fiber optic inclinometer enables long distance transmission in hazardous environments without signal loss. This paper presents a wide measurement range fiber optic inclinometer for a stable sensing principle and simple sensor structure, which were realized using a single transmissive grating panel, reflective mirror, and optical fibers as transceivers. In comparison with the conventional transmission type fiber optic inclinometer design, the proposed scheme's cable design was simplified by 50%. The variation curve of the gravity-referenced static acceleration, measured using the proposed fiber optic inclinometer, was sinusoidal and it was compared with actual gravitational acceleration. The developed inclinometer featured nonlinear sensitivities of 1.97°/rad (90–75°), 2.19°/rad (75–60°), 2.49°/rad (60–45°), 3.23°/rad (45–30°), 5.84°/rad (30–15°), and 10.42°/rad (15–0°) according to the measurement range. The maximum absolute error, which was analyzed at 5° intervals, was 0.96° in the full scale measurement range (−90° to 90°). In the full scale range, the R-square value was 0.9999 between the measured and actual tilt angles based on linear regression analysis, and it demonstrated good agreement.
Experimental research of optical fiber sensor for salinity measurement
13 August 2012,
09:38:31
Publication year:
2012
Source:Sensors and Actuators A: Physical, Volume 184
Jiyuan Wang, Baoxue Chen
Plastic optic fiber sensor is proposed and experimentally investigated for salinity measurement based on light power determination in different concentration of sodium chloride (NaCl) solution. U-shaped and spiral-shaped plastic optical fibers were used as sensor heads and light transmitting elements. As the NaCl concentration varies from 0% to 35%, the output transmitted light power of the sensor is proportional to salinity concentration. The sensitivities of the U-shaped sensor head and the spiral-shaped sensor head reach 0.42mV/% and 0.13mV/%, respectively. The experimental results indicate that the POF sensor has characteristics of feasibility, reversibility and stability.
Source:Sensors and Actuators A: Physical, Volume 184
Jiyuan Wang, Baoxue Chen
Plastic optic fiber sensor is proposed and experimentally investigated for salinity measurement based on light power determination in different concentration of sodium chloride (NaCl) solution. U-shaped and spiral-shaped plastic optical fibers were used as sensor heads and light transmitting elements. As the NaCl concentration varies from 0% to 35%, the output transmitted light power of the sensor is proportional to salinity concentration. The sensitivities of the U-shaped sensor head and the spiral-shaped sensor head reach 0.42mV/% and 0.13mV/%, respectively. The experimental results indicate that the POF sensor has characteristics of feasibility, reversibility and stability.
Highlights
► This paper reports a simple plastic multimode optical fiber sensor for salinity measurement. ► Optical probes with a U-shaped sensor head and a spiral-shaped sensor head are experimentally demonstrated and discussed, respectively. ► The sensitivities of the U-shaped sensor head and the spiral-shaped sensor head reach 0.42mV/% and 0.13mV/%, respectively. ► The experimental results indicate that this sensor has characteristics of feasibility, reversibility and stability.Fabric pressure sensor array fabricated with die-coating and weaving techniques
13 August 2012,
09:38:31
Publication year:
2012
Source:Sensors and Actuators A: Physical, Volume 184
Seiichi Takamatsu, Takeshi Kobayashi, Norihisa Shibayama, Koji Miyake, Toshihiro Itoh
We report on the fabrication and characterization of a large area (handkerchief-size, i.e., >16cm×16cm) of pressure sensor fabric. The sensor is constructed by weaving the fibers, which are coated with the organic conductive polymer poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) and a dielectric film of perfluoropolymer (Cytop), and the capacitances at the points of the crossed fibers vary with the applied force. The functional films are continuously coated with die-coating system with the thickness ranging from hundreds nm to several μm. The resultant fibers are loomed, forming the sensor fabric with an area of 16cm×16cm. Its sensitivity ranged from 0.98 to 9.8N/cm2, which is within the range of human touch. Therefore, our fabric touch sensors could lead to applications from wearable keyboards to sensors embedded in beds for health care purposes.
Source:Sensors and Actuators A: Physical, Volume 184
Seiichi Takamatsu, Takeshi Kobayashi, Norihisa Shibayama, Koji Miyake, Toshihiro Itoh
We report on the fabrication and characterization of a large area (handkerchief-size, i.e., >16cm×16cm) of pressure sensor fabric. The sensor is constructed by weaving the fibers, which are coated with the organic conductive polymer poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) and a dielectric film of perfluoropolymer (Cytop), and the capacitances at the points of the crossed fibers vary with the applied force. The functional films are continuously coated with die-coating system with the thickness ranging from hundreds nm to several μm. The resultant fibers are loomed, forming the sensor fabric with an area of 16cm×16cm. Its sensitivity ranged from 0.98 to 9.8N/cm2, which is within the range of human touch. Therefore, our fabric touch sensors could lead to applications from wearable keyboards to sensors embedded in beds for health care purposes.
Finite element modeling of conical acoustic emission sensors and corresponding experiments
13 August 2012,
09:38:31
Publication year:
2012
Source:Sensors and Actuators A: Physical, Volume 184
Markus G.R. Sause, Marvin A. Hamstad, Siegfried Horn
Mass-backed piezoelectric conical sensor elements are investigated by modeling and corresponding experiments for their response to pencil lead breaks on an aluminum plate. For the experiment and modeling investigation, the plate is chosen large enough to avoid interference of the detected signal by edge reflections within a time frame of 150μs. Signals from conical elements with varying cone angle are investigated. For simulation of the sensor signals an approach using multi-scale finite element modeling with coupled partial differential equations is presented. The simulation approach takes into account the signal excitation by pencil lead fracture, formation of Lamb waves, signal propagation and the details of the detection process. This process includes piezoelectric conversion and the influences of the complex impedance of the attached cables and circuitry. Experimental signals and simulated signals are compared as a function of the tip diameter of conical sensor elements. Using the presented method the absolute sensor response can be predicted for arbitrary propagation media and geometries like plates or rods, as well as for alternate sensor geometries.
Source:Sensors and Actuators A: Physical, Volume 184
Markus G.R. Sause, Marvin A. Hamstad, Siegfried Horn
Mass-backed piezoelectric conical sensor elements are investigated by modeling and corresponding experiments for their response to pencil lead breaks on an aluminum plate. For the experiment and modeling investigation, the plate is chosen large enough to avoid interference of the detected signal by edge reflections within a time frame of 150μs. Signals from conical elements with varying cone angle are investigated. For simulation of the sensor signals an approach using multi-scale finite element modeling with coupled partial differential equations is presented. The simulation approach takes into account the signal excitation by pencil lead fracture, formation of Lamb waves, signal propagation and the details of the detection process. This process includes piezoelectric conversion and the influences of the complex impedance of the attached cables and circuitry. Experimental signals and simulated signals are compared as a function of the tip diameter of conical sensor elements. Using the presented method the absolute sensor response can be predicted for arbitrary propagation media and geometries like plates or rods, as well as for alternate sensor geometries.
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