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Selected
papers from the latest issue:
Laser profilometer using a Fabry–Perot etalon and an objective
11 September 2013,
11:27:07
Publication date: 1 December
2013
Source:Sensors and Actuators A: Physical, Volume 203
Author(s): Shyh-Tsong Lin , Sheng-Lih Yeh , Yi-Chun Wang , Meng-Zhu Chen
This paper introduces an innovative laser profilometer using a Fabry–Perot etalon and an objective. Following the derivation of the measurement theory, an experimental setup constructed to realize the profilometer is demonstrated, and the experimental results from the uses of this setup are then presented. The experimental setup has a sensitivity, vertical resolution, and stability of 1.62/μm, 2.2nm, and 6.6nm, respectively, and the experimental results agree not only the validity but also the feasibility of the proposed profilometer.
Source:Sensors and Actuators A: Physical, Volume 203
Author(s): Shyh-Tsong Lin , Sheng-Lih Yeh , Yi-Chun Wang , Meng-Zhu Chen
This paper introduces an innovative laser profilometer using a Fabry–Perot etalon and an objective. Following the derivation of the measurement theory, an experimental setup constructed to realize the profilometer is demonstrated, and the experimental results from the uses of this setup are then presented. The experimental setup has a sensitivity, vertical resolution, and stability of 1.62/μm, 2.2nm, and 6.6nm, respectively, and the experimental results agree not only the validity but also the feasibility of the proposed profilometer.
Flexible PDMS electrode for one-point wearable wireless bio-potential acquisition
11 September 2013,
11:27:07
Publication date: 1 December
2013
Source:Sensors and Actuators A: Physical, Volume 203
Author(s): Chih-Yuan Chen , Chia-Lin Chang , Tsung-Fu Chien , Ching-Hsing Luo
This work presents a flexible poly-dimethylsiloxane (PDMS) electrode for a one-point, wearable, wireless bio-potential acquisition device. The proposed device measures electrocardiogram (ECG) signals and removes cumbersome wires from a general ECG monitoring system. A novel flexible PDMS dry electrode (FPDE) is constructed with Au as a contact layer in bio-compatible with skin and PDMS. However, PDMS has exhibited stability limit in Au deposition and patterning. This limitation is solved by the surface treatment of PDMS via CO2 laser to increase surface roughness from nm to μm scale. The laser treatment method can increase the adhesion ratio by up to 57% (max.), subsequently allowing for Au to be stably adhered on PDMS by physical deposition and patterning. This work also develops a simple technology to fabricate FPDEs by adopting polyimide film as the mask made with CO2 laser capable of reducing cost and reusable for metal patterning applications. Furthermore, a front-end acquisition circuit and a wireless ZigBee module are integrated and packaged by flexible and transparent PDMS cover with three-pad FPDEs into a novel one-point, wearable, wireless ECG acquisition device. Importantly, the proposed device can obtain ECG signals efficiently with comfortable skin touch.
Source:Sensors and Actuators A: Physical, Volume 203
Author(s): Chih-Yuan Chen , Chia-Lin Chang , Tsung-Fu Chien , Ching-Hsing Luo
This work presents a flexible poly-dimethylsiloxane (PDMS) electrode for a one-point, wearable, wireless bio-potential acquisition device. The proposed device measures electrocardiogram (ECG) signals and removes cumbersome wires from a general ECG monitoring system. A novel flexible PDMS dry electrode (FPDE) is constructed with Au as a contact layer in bio-compatible with skin and PDMS. However, PDMS has exhibited stability limit in Au deposition and patterning. This limitation is solved by the surface treatment of PDMS via CO2 laser to increase surface roughness from nm to μm scale. The laser treatment method can increase the adhesion ratio by up to 57% (max.), subsequently allowing for Au to be stably adhered on PDMS by physical deposition and patterning. This work also develops a simple technology to fabricate FPDEs by adopting polyimide film as the mask made with CO2 laser capable of reducing cost and reusable for metal patterning applications. Furthermore, a front-end acquisition circuit and a wireless ZigBee module are integrated and packaged by flexible and transparent PDMS cover with three-pad FPDEs into a novel one-point, wearable, wireless ECG acquisition device. Importantly, the proposed device can obtain ECG signals efficiently with comfortable skin touch.
Effect of pressure on the emission characteristics of surface dielectric barrier discharge plasma
11 September 2013,
11:27:07
Publication date: 1 December
2013
Source:Sensors and Actuators A: Physical, Volume 203
Author(s): Yun Wu , Yinghong Li , Min Jia , Huimin Song , Hua Liang
This paper reports an experimental study of the emission characteristics of the surface dielectric barrier discharge plasma under different pressure. N2(C3II u ) rotational temperature, electron temperature and density were used to quantify the plasma characteristics. At atmospheric pressure, when the inner gap width increases from 0mm to 1mm, emission characteristics change dramatically since the discharge is much more filamentary. N2(C3II u ) rotational temperature, electron temperature and density are much higher with inner gap width of 1mm. Along with the pressure decreasing, discharge transitions from filamentary to glow mode around 45Torr. Variation laws of N2(C3II u ) rotational temperature and electron density with inner gap width of 0mm and 1mm are different. While the variation law of electron temperature is similar. When the pressure is less than 8Torr, plasma characteristics are very similar with inner gap width of 0mm and 1mm.
Source:Sensors and Actuators A: Physical, Volume 203
Author(s): Yun Wu , Yinghong Li , Min Jia , Huimin Song , Hua Liang
This paper reports an experimental study of the emission characteristics of the surface dielectric barrier discharge plasma under different pressure. N2(C3II u ) rotational temperature, electron temperature and density were used to quantify the plasma characteristics. At atmospheric pressure, when the inner gap width increases from 0mm to 1mm, emission characteristics change dramatically since the discharge is much more filamentary. N2(C3II u ) rotational temperature, electron temperature and density are much higher with inner gap width of 1mm. Along with the pressure decreasing, discharge transitions from filamentary to glow mode around 45Torr. Variation laws of N2(C3II u ) rotational temperature and electron density with inner gap width of 0mm and 1mm are different. While the variation law of electron temperature is similar. When the pressure is less than 8Torr, plasma characteristics are very similar with inner gap width of 0mm and 1mm.
MEMS piezoelectric artificial basilar membrane with passive frequency selectivity for short pulse width signal modulation
11 September 2013,
11:27:07
Publication date: 1 December
2013
Source:Sensors and Actuators A: Physical, Volume 203
Author(s): Jongmoon Jang , Sangwon Kim , David J. Sly , Stephen J. O’leary , Hongsoo Choi
We demonstrated a novel MEMS artificial basilar membrane composed of a piezoelectric beam array that mimics the passive frequency selectivity of the cochlea and exhibits acoustic-to-electrical energy conversion. Each beam was designed to have a unique resonance frequency. To determine the resonance frequencies of the beams, the displacement and piezoelectric voltage were measured by applying a periodic chirped signal with a sound pressure level of 109.7dB. The measured resonance frequencies were in the range 10–37kHz. The piezoelectric signal was used to modulate a finite pulse-width signal for electrical stimulation; the pulse widths were in the range 0.43–5.1ms with sound pressure levels in the range 84.9–112.4dB.
Source:Sensors and Actuators A: Physical, Volume 203
Author(s): Jongmoon Jang , Sangwon Kim , David J. Sly , Stephen J. O’leary , Hongsoo Choi
We demonstrated a novel MEMS artificial basilar membrane composed of a piezoelectric beam array that mimics the passive frequency selectivity of the cochlea and exhibits acoustic-to-electrical energy conversion. Each beam was designed to have a unique resonance frequency. To determine the resonance frequencies of the beams, the displacement and piezoelectric voltage were measured by applying a periodic chirped signal with a sound pressure level of 109.7dB. The measured resonance frequencies were in the range 10–37kHz. The piezoelectric signal was used to modulate a finite pulse-width signal for electrical stimulation; the pulse widths were in the range 0.43–5.1ms with sound pressure levels in the range 84.9–112.4dB.
Optimal design of a four-sensor probe system to measure the flow properties of the dispersed phase in bubbly air–water multiphase flows
11 September 2013,
11:27:07
Publication date: 15 October
2013
Source:Sensors and Actuators A: Physical, Volume 201
Author(s): S.R. Pradhan , R. Mishra , K. Ubbi , T. Asim
This paper presents a systematic investigation on the design and development of a four-sensor probe system to be used for air–water multiphase flow measurements. A mathematical model is presented which can be used to determine the optimum axial separation of the front sensor with respect to three rear sensors within a four sensor probe system. This system can be used to measure flow properties of the dispersed phase in bubbly air–water flows accurately. Paper also presents a sensitivity analysis to determine the minimum sampling frequency requirements in the data collection process, so that associated errors in various output parameters can be minimized, for the given values of sensors co-ordinates. A particularly novel feature of this paper is development of a unique digital signal processing scheme to enable the accurate computation of different flow characteristics. This paper also presents validation of four-sensor probe measurements from a flow visualization and measurement system which relies on using two high speed cameras mounted orthogonally. The results obtained from validation experiments show very high degree of similarity in measured flow variables from the two systems. This indicates that the four-sensor probe system developed in this study can be used with confidence to measure parameters of a dispersed multiphase flow. The flow characteristics obtained from the four-sensor probe system when used in a multiphase flow system are also presented. The results indicate a unique flow pattern corresponding to bubbles of different sizes in air–water flows.
Source:Sensors and Actuators A: Physical, Volume 201
Author(s): S.R. Pradhan , R. Mishra , K. Ubbi , T. Asim
This paper presents a systematic investigation on the design and development of a four-sensor probe system to be used for air–water multiphase flow measurements. A mathematical model is presented which can be used to determine the optimum axial separation of the front sensor with respect to three rear sensors within a four sensor probe system. This system can be used to measure flow properties of the dispersed phase in bubbly air–water flows accurately. Paper also presents a sensitivity analysis to determine the minimum sampling frequency requirements in the data collection process, so that associated errors in various output parameters can be minimized, for the given values of sensors co-ordinates. A particularly novel feature of this paper is development of a unique digital signal processing scheme to enable the accurate computation of different flow characteristics. This paper also presents validation of four-sensor probe measurements from a flow visualization and measurement system which relies on using two high speed cameras mounted orthogonally. The results obtained from validation experiments show very high degree of similarity in measured flow variables from the two systems. This indicates that the four-sensor probe system developed in this study can be used with confidence to measure parameters of a dispersed multiphase flow. The flow characteristics obtained from the four-sensor probe system when used in a multiphase flow system are also presented. The results indicate a unique flow pattern corresponding to bubbles of different sizes in air–water flows.
Non-contact crack detection of high-speed blades based on principal component analysis and Euclidian angles using optical-fiber sensors
11 September 2013,
11:27:07
Publication date: 15 October
2013
Source:Sensors and Actuators A: Physical, Volume 201
Author(s): Zhongsheng Chen , Yongmin Yang , Yong Xie , Bin Guo , Zheng Hu
High-speed rotating blades are key mechanical components in turbo-machinery. High cycle fatigues often induce blade cracks and ultimately the loss of blades. Effort has being made to measure on-line blade vibrations and promptly detect potential cracks. Traditional contacting methods are difficult to satisfy the needs of on-line testing, enduring extreme conditions and non-invasion. Nowadays non-contact vibration measurement at blade tips by optical sensing has become a promising approach. In this paper a blade tip-timing (BTT) method using four optical-fiber sensors is presented and all-blade vibration displacements are derived in detail. Blade vibration signals collected by the BTT method are typical sub-sampled signals, so a signal reconstruction method is proposed based on the Shannon sampling theorem. Next nine candidate vibration parameters are calculated to form the crack feature space and principal component analysis (PCA) is used to extract principal components from it. Then Euclidian angles of principal components are defined to detect cracks. In the end, an experimental set-up is built and a small crack is cut on a blade artificially. Collected data are analyzed to testify the proposed method and the experimental results demonstrate its effectiveness.
Source:Sensors and Actuators A: Physical, Volume 201
Author(s): Zhongsheng Chen , Yongmin Yang , Yong Xie , Bin Guo , Zheng Hu
High-speed rotating blades are key mechanical components in turbo-machinery. High cycle fatigues often induce blade cracks and ultimately the loss of blades. Effort has being made to measure on-line blade vibrations and promptly detect potential cracks. Traditional contacting methods are difficult to satisfy the needs of on-line testing, enduring extreme conditions and non-invasion. Nowadays non-contact vibration measurement at blade tips by optical sensing has become a promising approach. In this paper a blade tip-timing (BTT) method using four optical-fiber sensors is presented and all-blade vibration displacements are derived in detail. Blade vibration signals collected by the BTT method are typical sub-sampled signals, so a signal reconstruction method is proposed based on the Shannon sampling theorem. Next nine candidate vibration parameters are calculated to form the crack feature space and principal component analysis (PCA) is used to extract principal components from it. Then Euclidian angles of principal components are defined to detect cracks. In the end, an experimental set-up is built and a small crack is cut on a blade artificially. Collected data are analyzed to testify the proposed method and the experimental results demonstrate its effectiveness.
Theoretical modeling, simulation and experimental studies of fiber optic bundle displacement sensor
11 September 2013,
11:27:07
Publication date: 15 October
2013
Source:Sensors and Actuators A: Physical, Volume 201
Author(s): Supriya S. Patil , P.B. Buchade , A.D. Shaligram
This paper reports unified mathematical model of fiber optic bundle displacement sensor (FOBDS) based on ray tracing technique. The sensor response for concentric, random and hemispherical fiber bundle configurations is simulated using the developed model. The sensor performance parameters viz. sensitivity and linear operating range are calculated by differentiating the sensor response curve. It is observed that for a fiber bundle having two crowns of fibers with central illuminating fiber, sensitivity varies as 0.22, 0.42, 0.47 and linear operating range varies as 40mm, 22mm and 45mm for concentric, random and hemispherical configurations respectively. These results are validated by performing experiments with the developed sensor probe. Experimental results are almost matching the simulated results. After comparing the results for three configurations, it is concluded that the hemispherical configuration is best suitable configuration for sensor showing concurrent improvement in both the sensor performance parameters.
Source:Sensors and Actuators A: Physical, Volume 201
Author(s): Supriya S. Patil , P.B. Buchade , A.D. Shaligram
This paper reports unified mathematical model of fiber optic bundle displacement sensor (FOBDS) based on ray tracing technique. The sensor response for concentric, random and hemispherical fiber bundle configurations is simulated using the developed model. The sensor performance parameters viz. sensitivity and linear operating range are calculated by differentiating the sensor response curve. It is observed that for a fiber bundle having two crowns of fibers with central illuminating fiber, sensitivity varies as 0.22, 0.42, 0.47 and linear operating range varies as 40mm, 22mm and 45mm for concentric, random and hemispherical configurations respectively. These results are validated by performing experiments with the developed sensor probe. Experimental results are almost matching the simulated results. After comparing the results for three configurations, it is concluded that the hemispherical configuration is best suitable configuration for sensor showing concurrent improvement in both the sensor performance parameters.
Network modeling of multiple-port, multiple-vibration-mode transducers and resonators
11 September 2013,
11:27:07
Publication date: 15 October
2013
Source:Sensors and Actuators A: Physical, Volume 201
Author(s): Michael L. Kuntzman , Donghwan Kim , Nishshanka N. Hewa-Kasakarage , Karen D. Kirk , Neal A. Hall
A modeling procedure is presented for multiple-port, multiple-vibration-mode transducers. Unique features of the procedure include the use of modal coordinates to describe deformations of the mechanical structure, the use of a network analog for each vibration mode of the structure, and the selection of modal velocity, rather than a particular physical velocity on the structure, as the mechanical flow variable in each modal network. Finite element analysis is used only to compute a discrete set of salient circuit parameters, with all other analysis and design computations performed using the networks. The approach is computationally efficient and assists with providing insights into the design of actuators and micromechanical resonators, where the generation and suppression of particular vibration modes may be important. A micromachined, multiple-port piezoelectric microphone with in-plane directivity is presented as a case study to demonstrate application of the procedure. Model verification is performed by comparing simulated and measured port-to-port transfer functions over a frequency range spanning several vibration modes of the device. The modeling procedure can address multiple-port sensor response to distributed loadings, selective excitation and suppression of modes in actuator applications, and mixed sensing and actuator applications such as the demonstrated port-to-port measurements.
Source:Sensors and Actuators A: Physical, Volume 201
Author(s): Michael L. Kuntzman , Donghwan Kim , Nishshanka N. Hewa-Kasakarage , Karen D. Kirk , Neal A. Hall
A modeling procedure is presented for multiple-port, multiple-vibration-mode transducers. Unique features of the procedure include the use of modal coordinates to describe deformations of the mechanical structure, the use of a network analog for each vibration mode of the structure, and the selection of modal velocity, rather than a particular physical velocity on the structure, as the mechanical flow variable in each modal network. Finite element analysis is used only to compute a discrete set of salient circuit parameters, with all other analysis and design computations performed using the networks. The approach is computationally efficient and assists with providing insights into the design of actuators and micromechanical resonators, where the generation and suppression of particular vibration modes may be important. A micromachined, multiple-port piezoelectric microphone with in-plane directivity is presented as a case study to demonstrate application of the procedure. Model verification is performed by comparing simulated and measured port-to-port transfer functions over a frequency range spanning several vibration modes of the device. The modeling procedure can address multiple-port sensor response to distributed loadings, selective excitation and suppression of modes in actuator applications, and mixed sensing and actuator applications such as the demonstrated port-to-port measurements.
SAW-RFID enabled temperature sensor
11 September 2013,
11:27:07
Publication date: 15 October
2013
Source:Sensors and Actuators A: Physical, Volume 201
Author(s): Along Kang , Chenrui Zhang , Xiaojun Ji , Tao Han , Ruisheng Li , Xianwei Li
Wireless sensors based on surface acoustic wave (SAW) technology has its own advantages over its counterparts. In this paper, a novel SAW radio frequency identification (RFID) enabled temperature sensor is proposed for industrial applications, in which short measurement range but high accuracy is usually required. The encoding scheme for the sensor using pulse positions combined with phase information is adopted, and then the relationship between the length of a time slot and the decoding errors is deduced to ensure the sensor can be accurately identified, even though ambient temperature fluctuates. In order to solve the phase ambiguity problem involved in temperature measurements more efficiently and reduce the cost of obtaining the unwrapping temperature characteristic curves in the calibration process, an analytical procedure for calculating the variation of phase delay differences with respect to temperature has been proposed. A self-developed burst transceiver supporting online data analysis is also presented. The experimental results demonstrate the effectiveness and practicality of the proposed SAW-RFID enabled temperature sensing scheme, and the prototype sensor within a temperature-controlled oven 2m away from the center of the transceiver antenna in a horizontal orientation achieves an accuracy of ±0.3°C in the temperature range 0–40°C.
Source:Sensors and Actuators A: Physical, Volume 201
Author(s): Along Kang , Chenrui Zhang , Xiaojun Ji , Tao Han , Ruisheng Li , Xianwei Li
Wireless sensors based on surface acoustic wave (SAW) technology has its own advantages over its counterparts. In this paper, a novel SAW radio frequency identification (RFID) enabled temperature sensor is proposed for industrial applications, in which short measurement range but high accuracy is usually required. The encoding scheme for the sensor using pulse positions combined with phase information is adopted, and then the relationship between the length of a time slot and the decoding errors is deduced to ensure the sensor can be accurately identified, even though ambient temperature fluctuates. In order to solve the phase ambiguity problem involved in temperature measurements more efficiently and reduce the cost of obtaining the unwrapping temperature characteristic curves in the calibration process, an analytical procedure for calculating the variation of phase delay differences with respect to temperature has been proposed. A self-developed burst transceiver supporting online data analysis is also presented. The experimental results demonstrate the effectiveness and practicality of the proposed SAW-RFID enabled temperature sensing scheme, and the prototype sensor within a temperature-controlled oven 2m away from the center of the transceiver antenna in a horizontal orientation achieves an accuracy of ±0.3°C in the temperature range 0–40°C.
Heated atomic force microscope cantilever with high resistivity for improved temperature sensitivity
11 September 2013,
11:27:07
Publication date: 15 October
2013
Source:Sensors and Actuators A: Physical, Volume 201
Author(s): Joseph O. Liu , Suhas Somnath , William P. King
We report a heated atomic force microscope cantilever with a heater region engineered to have high temperature sensitivity. The high resistivity (HR) heater region is phosphorous-doped silicon with a doping concentration of 1×1016 cm−3 and a resistivity of 0.53Ω-cm. The heater has a temperature coefficient of resistance of 102ΩC−1 over the temperature range 100–300°C, which is more than one order magnitude higher compared to heated cantilevers from previous publications. When used for thermal sensing of substrate nanotopography, the HR cantilever has a sensitivity of 0.37mV/nm at 300°C. Because the HR cantilever has high sensitivity at relatively low temperatures, it can be used to measure substrates that cannot withstand high temperatures, demonstrated here as a polymer film grating of thickness 110nm.
Source:Sensors and Actuators A: Physical, Volume 201
Author(s): Joseph O. Liu , Suhas Somnath , William P. King
We report a heated atomic force microscope cantilever with a heater region engineered to have high temperature sensitivity. The high resistivity (HR) heater region is phosphorous-doped silicon with a doping concentration of 1×1016 cm−3 and a resistivity of 0.53Ω-cm. The heater has a temperature coefficient of resistance of 102ΩC−1 over the temperature range 100–300°C, which is more than one order magnitude higher compared to heated cantilevers from previous publications. When used for thermal sensing of substrate nanotopography, the HR cantilever has a sensitivity of 0.37mV/nm at 300°C. Because the HR cantilever has high sensitivity at relatively low temperatures, it can be used to measure substrates that cannot withstand high temperatures, demonstrated here as a polymer film grating of thickness 110nm.
Characterization and modeling of a piezoresistive three-axial force micro sensor
11 September 2013,
11:27:07
Publication date: 15 October
2013
Source:Sensors and Actuators A: Physical, Volume 201
Author(s): N. Alcheikh , C. Coutier , S. Giroud , C. Poulain , P. Rey
To mimic human mechanoreceptors and give sense of touch to robots highly integrated and highly sensitive three-axial force micro sensors are required. In this paper, we present the fabrication and electro-mechanical characterization of silicon based 3D force micro sensors with piezoresistive gauges with a footprint less than 1.5mm2. The measurements have been validated with a Finite Element Modeling (FEM). The sensor sensitivities to normal and tangential loads are about 1.03mV/V/mN and 1.6mV/V/mN, respectively. For such high integrated 3D force sensors these values are among the highest sensitivities reported in the literature. High linearity and low hysteresis under normal forces have also been demonstrated.
Source:Sensors and Actuators A: Physical, Volume 201
Author(s): N. Alcheikh , C. Coutier , S. Giroud , C. Poulain , P. Rey
To mimic human mechanoreceptors and give sense of touch to robots highly integrated and highly sensitive three-axial force micro sensors are required. In this paper, we present the fabrication and electro-mechanical characterization of silicon based 3D force micro sensors with piezoresistive gauges with a footprint less than 1.5mm2. The measurements have been validated with a Finite Element Modeling (FEM). The sensor sensitivities to normal and tangential loads are about 1.03mV/V/mN and 1.6mV/V/mN, respectively. For such high integrated 3D force sensors these values are among the highest sensitivities reported in the literature. High linearity and low hysteresis under normal forces have also been demonstrated.
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