A new issue of this journal has just
been published. To see abstracts of the papers it contains (with links through
to the full papers) click here:
Selected
papers from the latest issue:
An improved sensitivity normalization technique of PGC demodulation with low minimum phase detection sensitivity using laser modulation to generate carrier signal
31 December 2012,
09:28:22
1 March 2013
Publication year: 2013
Source:Sensors and Actuators A: Physical, Volume 191
The phase carrier signal of the PGC demodulation in fiber optic interferometric sensors (FOIS) may be generated by using laser current modulation to achieve all-fiber structures in long-distance and outdoor applications. An optical intensity modulation with carrier frequency induced from the laser modulation will cause the instability and distortion in the PGC demodulation output. Additionally, since the optical intensity attenuation of the FOIS will degrade the PGC demodulation output, proper sensitivity compensation on the PGC demodulator is necessary for the field applications. In this paper, we propose an improved technique by using a balanced photoreceiver in the FOIS to attain significant improvements in the instability and distortion of the PGC demodulation output. Moreover, we choose a small phase scrambler signal amplitude of 1rad to achieve improved the minimum phase detection sensitivity (MPDS) as well as sensitivity normalization because the improvement of the MPDS is very important to the advanced FOIS. The experimental results show that the improved values of the best MPDS are 5.7dB (for DFB laser diode) and 4.3dB (for EP1550 laser diode), respectively, by using the improved technique. From the sensitivity normalization experiment results, the relative error is shown to be less than 0.5% when the optical intensity attentuation is no more than 15dB. It verifies the effectiveness of the sensitivity normalization technique proposed in our improved PGC demodulation system.
Publication year: 2013
Source:Sensors and Actuators A: Physical, Volume 191
The phase carrier signal of the PGC demodulation in fiber optic interferometric sensors (FOIS) may be generated by using laser current modulation to achieve all-fiber structures in long-distance and outdoor applications. An optical intensity modulation with carrier frequency induced from the laser modulation will cause the instability and distortion in the PGC demodulation output. Additionally, since the optical intensity attenuation of the FOIS will degrade the PGC demodulation output, proper sensitivity compensation on the PGC demodulator is necessary for the field applications. In this paper, we propose an improved technique by using a balanced photoreceiver in the FOIS to attain significant improvements in the instability and distortion of the PGC demodulation output. Moreover, we choose a small phase scrambler signal amplitude of 1rad to achieve improved the minimum phase detection sensitivity (MPDS) as well as sensitivity normalization because the improvement of the MPDS is very important to the advanced FOIS. The experimental results show that the improved values of the best MPDS are 5.7dB (for DFB laser diode) and 4.3dB (for EP1550 laser diode), respectively, by using the improved technique. From the sensitivity normalization experiment results, the relative error is shown to be less than 0.5% when the optical intensity attentuation is no more than 15dB. It verifies the effectiveness of the sensitivity normalization technique proposed in our improved PGC demodulation system.
Demonstration of an optically actuated ferrule-top device for pressure and humidity sensing
31 December 2012,
09:28:22
1 February 2013
Publication year: 2013
Source:Sensors and Actuators A: Physical, Volume 190
Ferrule-top micro mechanical sensors are an alternative platform for point measurements in critical environments, where standard micro-electro-mechanical systems are prone to failure. To fully benefit from the all-optical character of this design, it is important to demonstrate that the mechanical pieces fabricated on top of the ferruled fiber can be actuated with light. In this paper we propose a convenient, all-optical actuation scheme that can be applied without any additional modification of the sensor design. The scheme relies on the photo thermal effect, which is proven to be sufficient both for inducing significant static bending and for exciting the sensor to resonance. We also demonstrate that this mechanism can be successfully used to implement ferrule-top resonant sensors for humidity and pressure measurements.
Publication year: 2013
Source:Sensors and Actuators A: Physical, Volume 190
Ferrule-top micro mechanical sensors are an alternative platform for point measurements in critical environments, where standard micro-electro-mechanical systems are prone to failure. To fully benefit from the all-optical character of this design, it is important to demonstrate that the mechanical pieces fabricated on top of the ferruled fiber can be actuated with light. In this paper we propose a convenient, all-optical actuation scheme that can be applied without any additional modification of the sensor design. The scheme relies on the photo thermal effect, which is proven to be sufficient both for inducing significant static bending and for exciting the sensor to resonance. We also demonstrate that this mechanism can be successfully used to implement ferrule-top resonant sensors for humidity and pressure measurements.
Highlights
► We demonstrate an all-optical actuation scheme for ferrule-top sensors. ► The new approach does not require any modification of sensors design. ► The method is sufficient for static and dynamic excitation. ► We present an all-optical gravimetric humidity and pressure sensor.Novel optical fiber humidity sensor based on a no-core fiber structure
31 December 2012,
09:28:22
1 February 2013
Publication year: 2013
Source:Sensors and Actuators A: Physical, Volume 190
A novel and simple optical fiber structure with a section of no-core fiber for measuring relative humidity (RH) is presented. Moisture-sensitive materials HEC/PVDF are used to form the hydrogel coating on the no-core fiber by dip impregnation method. Under different humidity conditions, the humidity induced refractive index changes on the outside coating of no-core fiber will lead to the variations of the optical output power. The different lengths of no-core fiber are tested at the two wavelengths of 1310nm and 1550nm, respectively. The results show that the structure with 2cm no-core fiber has a higher RH sensitivity of 0.196dB/%RH at 1310nm and a better linearly response when the RH is lower than 75%. Furthermore, the optical output powers are measured with the rise and drop of RH, and the four times repetition are also recorded, which all demonstrate the good stability and repeatability of our proposed structure.
Publication year: 2013
Source:Sensors and Actuators A: Physical, Volume 190
A novel and simple optical fiber structure with a section of no-core fiber for measuring relative humidity (RH) is presented. Moisture-sensitive materials HEC/PVDF are used to form the hydrogel coating on the no-core fiber by dip impregnation method. Under different humidity conditions, the humidity induced refractive index changes on the outside coating of no-core fiber will lead to the variations of the optical output power. The different lengths of no-core fiber are tested at the two wavelengths of 1310nm and 1550nm, respectively. The results show that the structure with 2cm no-core fiber has a higher RH sensitivity of 0.196dB/%RH at 1310nm and a better linearly response when the RH is lower than 75%. Furthermore, the optical output powers are measured with the rise and drop of RH, and the four times repetition are also recorded, which all demonstrate the good stability and repeatability of our proposed structure.
Resonance frequency of locally heated cantilever beams
31 December 2012,
09:28:22
1 February 2013
Publication year: 2013
Source:Sensors and Actuators A: Physical, Volume 190
This paper investigates the temperature dependence of the resonance frequency for locally heated cantilever beams and proposes a solution to minimize it. In the first part of the paper a theoretical study, supported by simulations, is carried out in order to determine the temperature distribution on locally heated cantilever beams. The theoretical results are supported by measurements performed with an IR camera. Knowing the temperature distribution on the cantilever beams, the frequency shifts due to the temperature gradient on the beams is calculated. A comparison between three locally heated cantilever beams made of Si, SiO2 and SiN shows that SiN is the best choice in order to minimize the temperature dependence of the resonance frequency. Measurements on a SiN cantilever paddle show that its resonance frequency is constant with heater temperature for temperature up to 590 K. The device exhibits a temperature dependence of the resonance frequency of about 20ppm/K, for heater temperature from 590K to 920K.
Publication year: 2013
Source:Sensors and Actuators A: Physical, Volume 190
This paper investigates the temperature dependence of the resonance frequency for locally heated cantilever beams and proposes a solution to minimize it. In the first part of the paper a theoretical study, supported by simulations, is carried out in order to determine the temperature distribution on locally heated cantilever beams. The theoretical results are supported by measurements performed with an IR camera. Knowing the temperature distribution on the cantilever beams, the frequency shifts due to the temperature gradient on the beams is calculated. A comparison between three locally heated cantilever beams made of Si, SiO2 and SiN shows that SiN is the best choice in order to minimize the temperature dependence of the resonance frequency. Measurements on a SiN cantilever paddle show that its resonance frequency is constant with heater temperature for temperature up to 590 K. The device exhibits a temperature dependence of the resonance frequency of about 20ppm/K, for heater temperature from 590K to 920K.
Measurement of thermal elongation induced strain of a composite material using a polarization maintaining photonic crystal fiber sensor
31 December 2012,
09:28:22
1 February 2013
Publication year: 2013
Source:Sensors and Actuators A: Physical, Volume 190
A measurement scheme to measure a composite material's thermal elongation induced strain using a buffer stripped Polarization Maintaining Photonic Crystal Fiber (PM-PCF) sensor is investigated in this paper. A composite material sample with an embedded PM-PCF based polarimetric fiber sensor is fabricated and characterized. It is found that the buffer stripped PM-PCF polarimetric sensor which is temperature insensitive in free space, shows significant phase change when embedded in the composite material due the thermal elongation of the composite material. The temperature induced phase change of buffer stripped PM-PCF polarimetric sensors embedded in carbon-epoxy, E glass-epoxy, E glass-unsaturated polyester resin composite material samples is measured and the results are used to determine the thermal elongation induced strain over a temperature range from 0°C to 65°C. The experimentally measured thermal elongation induced strain of the same samples are found to be 3.648×10−5 ɛ/°C, 1.52×10−5 ɛ/°C, and 2.42×10−5 ɛ/°C. The Coefficient of Thermal Expansion (CTE) estimated theoretically using composite laminate theory shows good agreement with that derived using the PM-PCF sensor. The present investigation offers a simple non destructive method to determine thermal elongation induced strain in composite structures. It is shown that the method allows the measurement of thermal expansion for those composite materials having negligible residual strain and moisture expansion.
Publication year: 2013
Source:Sensors and Actuators A: Physical, Volume 190
A measurement scheme to measure a composite material's thermal elongation induced strain using a buffer stripped Polarization Maintaining Photonic Crystal Fiber (PM-PCF) sensor is investigated in this paper. A composite material sample with an embedded PM-PCF based polarimetric fiber sensor is fabricated and characterized. It is found that the buffer stripped PM-PCF polarimetric sensor which is temperature insensitive in free space, shows significant phase change when embedded in the composite material due the thermal elongation of the composite material. The temperature induced phase change of buffer stripped PM-PCF polarimetric sensors embedded in carbon-epoxy, E glass-epoxy, E glass-unsaturated polyester resin composite material samples is measured and the results are used to determine the thermal elongation induced strain over a temperature range from 0°C to 65°C. The experimentally measured thermal elongation induced strain of the same samples are found to be 3.648×10−5 ɛ/°C, 1.52×10−5 ɛ/°C, and 2.42×10−5 ɛ/°C. The Coefficient of Thermal Expansion (CTE) estimated theoretically using composite laminate theory shows good agreement with that derived using the PM-PCF sensor. The present investigation offers a simple non destructive method to determine thermal elongation induced strain in composite structures. It is shown that the method allows the measurement of thermal expansion for those composite materials having negligible residual strain and moisture expansion.
A review of nanometer resolution position sensors: Operation and performance
31 December 2012,
09:28:22
1 February 2013
Publication year: 2013
Source:Sensors and Actuators A: Physical, Volume 190
Position sensors with nanometer resolution are a key component of many precision imaging and fabrication machines. Since the sensor characteristics can define the linearity, resolution and speed of the machine, the sensor performance is a foremost consideration. The first goal of this article is to define concise performance metrics and to provide exact and approximate expressions for error sources including non-linearity, drift and noise. The second goal is to review current position sensor technologies and to compare their performance. The sensors considered include: resistive, piezoelectric and piezoresistive strain sensors; capacitive sensors; electrothermal sensors; eddy current sensors; linear variable displacement transformers; interferometers; and linear encoders.
Publication year: 2013
Source:Sensors and Actuators A: Physical, Volume 190
Position sensors with nanometer resolution are a key component of many precision imaging and fabrication machines. Since the sensor characteristics can define the linearity, resolution and speed of the machine, the sensor performance is a foremost consideration. The first goal of this article is to define concise performance metrics and to provide exact and approximate expressions for error sources including non-linearity, drift and noise. The second goal is to review current position sensor technologies and to compare their performance. The sensors considered include: resistive, piezoelectric and piezoresistive strain sensors; capacitive sensors; electrothermal sensors; eddy current sensors; linear variable displacement transformers; interferometers; and linear encoders.
Transparent force sensing arrays with low power consumption using liquid crystal arrays
31 December 2012,
09:28:22
1 February 2013
Publication year: 2013
Source:Sensors and Actuators A: Physical, Volume 190
A transparent force sensing array with low power consumption is developed from a 3×3 liquid crystal (LC) array. As force is applied to the LC array, the force-dependent capacitance curve of a sensor pixel under a higher voltage will shift to larger capacitance. Accordingly, the force range of the LC array can be divided into many sub-ranges at one of the capacitance values. The number of the input voltage is equal to that of the output capacitance in each of the sub-ranges, and the voltage-to-capacitance number is small (large) in the high (low)-force sub-range. The sensing array measures force in terms of the voltage-to-capacitance number. The transparent force sensing array shows potential as a touch panel, while it is immune to the need of rectifying the nonlinear relation between the applied force and the output capacitance using complex algorithm via high-end microcontrollers.
Publication year: 2013
Source:Sensors and Actuators A: Physical, Volume 190
A transparent force sensing array with low power consumption is developed from a 3×3 liquid crystal (LC) array. As force is applied to the LC array, the force-dependent capacitance curve of a sensor pixel under a higher voltage will shift to larger capacitance. Accordingly, the force range of the LC array can be divided into many sub-ranges at one of the capacitance values. The number of the input voltage is equal to that of the output capacitance in each of the sub-ranges, and the voltage-to-capacitance number is small (large) in the high (low)-force sub-range. The sensing array measures force in terms of the voltage-to-capacitance number. The transparent force sensing array shows potential as a touch panel, while it is immune to the need of rectifying the nonlinear relation between the applied force and the output capacitance using complex algorithm via high-end microcontrollers.
Preparation of semiconductor ZnO powders by sol–gel method: Humidity sensors
31 December 2012,
09:28:22
1 February 2013
Publication year: 2013
Source:Sensors and Actuators A: Physical, Volume 190
Undoped and Sn-doped ZnO nanopowder samples were prepared by the sol–gel method. The crystalline structure and surface morphology of the samples were analyzed by X-ray diffraction and atomic force microscopy. X-ray diffraction results indicate that the samples exhibit a hexagonal crystal structure. Electrical properties of the samples were measured by two probe method. The activation energies of the ZnO samples for low and high temperatures regions were determined. The optical band gaps of the samples were determined by optical absorption method. It was found that the samples have a direct transition optical band gap and the optical band gap values of the ZnO samples were changed with Sn doping. Quartz crystalline microbalance (QCM) technique was employed to investigate sensor features of the ZnO samples. The humidity sensor properties of undoped and Sn-doped ZnO samples based on quartz crystalline microbalance sensors were investigated. The obtained results indicate that the undoped and Sn-doped ZnO nanopowder samples can be used for humidity sensor applications.
Publication year: 2013
Source:Sensors and Actuators A: Physical, Volume 190
Undoped and Sn-doped ZnO nanopowder samples were prepared by the sol–gel method. The crystalline structure and surface morphology of the samples were analyzed by X-ray diffraction and atomic force microscopy. X-ray diffraction results indicate that the samples exhibit a hexagonal crystal structure. Electrical properties of the samples were measured by two probe method. The activation energies of the ZnO samples for low and high temperatures regions were determined. The optical band gaps of the samples were determined by optical absorption method. It was found that the samples have a direct transition optical band gap and the optical band gap values of the ZnO samples were changed with Sn doping. Quartz crystalline microbalance (QCM) technique was employed to investigate sensor features of the ZnO samples. The humidity sensor properties of undoped and Sn-doped ZnO samples based on quartz crystalline microbalance sensors were investigated. The obtained results indicate that the undoped and Sn-doped ZnO nanopowder samples can be used for humidity sensor applications.
ZnO nanowires–polyimide nanocomposite piezoresistive strain sensor
31 December 2012,
09:28:22
1 February 2013
Publication year: 2013
Source:Sensors and Actuators A: Physical, Volume 190
In this paper, we report a significant piezoresistive effect found in ZnO nanowires–polyimide nanocomposite. ZnO nanowires were synthesized through a simple hydrothermal route and subsequently mixed with polyimide matrix to form ZnO nanowires–polyimide nanocomposite. Electrical properties of the nanocomposite films, such as electrical conductivity, relative dielectric permittivity, impedance spectrum and electrical I–V curve, change with weight ratio of ZnO nanowires were characterized. Electrical measurement results indicated that the percolation threshold of the nanocomposite is about 15% weight ratio of ZnO nanowires. Piezoresistive effect of the nanocomposite was investigated and large gauge factor was observed for this nanocomposite. Strain sensors based on the nanocomposite thin films using interdigital electrodes were fabricated and used to measure the static and dynamic strain in a cantilever beam and the results were validated by theoretical calculation and measurements by other technique. With excellent flexibility, simple fabrication process, and large piezoresistive gauge factor, this novel ZnO nanocomposite can be used for strain sensors in many mechanical, civil, aerospace, and medical applications.
Publication year: 2013
Source:Sensors and Actuators A: Physical, Volume 190
In this paper, we report a significant piezoresistive effect found in ZnO nanowires–polyimide nanocomposite. ZnO nanowires were synthesized through a simple hydrothermal route and subsequently mixed with polyimide matrix to form ZnO nanowires–polyimide nanocomposite. Electrical properties of the nanocomposite films, such as electrical conductivity, relative dielectric permittivity, impedance spectrum and electrical I–V curve, change with weight ratio of ZnO nanowires were characterized. Electrical measurement results indicated that the percolation threshold of the nanocomposite is about 15% weight ratio of ZnO nanowires. Piezoresistive effect of the nanocomposite was investigated and large gauge factor was observed for this nanocomposite. Strain sensors based on the nanocomposite thin films using interdigital electrodes were fabricated and used to measure the static and dynamic strain in a cantilever beam and the results were validated by theoretical calculation and measurements by other technique. With excellent flexibility, simple fabrication process, and large piezoresistive gauge factor, this novel ZnO nanocomposite can be used for strain sensors in many mechanical, civil, aerospace, and medical applications.
Worm like zinc oxide nanostructures as efficient LPG sensors
31 December 2012,
09:28:22
1 February 2013
Publication year: 2013
Source:Sensors and Actuators A: Physical, Volume 190
Multi-layered films of zinc oxide (ZnO), prepared using sol–gel spin-coating method, were used to study the response on exposure to liquefied petroleum gas (LPG). The X-ray diffraction (XRD) pattern of the thin films showed preferred orientation of the crystallites along the c-axis. Surface morphology studies using scanning electron microscopy (SEM) reveal a wrinkled surface with a worm like appearance for the film thickness varying from 85nm to 419nm. The films of different thickness were exposed to LPG and sensing characteristics were recorded using electrical methods. The ZnO thin films showed good sensitivity toward LPG at optimum temperature of 200°C with sensitivity strongly depending on the number of layers deposited. The sensing characteristics were further correlated with the microstructure of the thin films investigated using atomic force microscopy (AFM).
Publication year: 2013
Source:Sensors and Actuators A: Physical, Volume 190
Multi-layered films of zinc oxide (ZnO), prepared using sol–gel spin-coating method, were used to study the response on exposure to liquefied petroleum gas (LPG). The X-ray diffraction (XRD) pattern of the thin films showed preferred orientation of the crystallites along the c-axis. Surface morphology studies using scanning electron microscopy (SEM) reveal a wrinkled surface with a worm like appearance for the film thickness varying from 85nm to 419nm. The films of different thickness were exposed to LPG and sensing characteristics were recorded using electrical methods. The ZnO thin films showed good sensitivity toward LPG at optimum temperature of 200°C with sensitivity strongly depending on the number of layers deposited. The sensing characteristics were further correlated with the microstructure of the thin films investigated using atomic force microscopy (AFM).
No comments:
Post a Comment