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Special Issue "Instrumentation, Signal Treatment and Uncertainty Estimation in Sensors"

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A special issue of Sensors (ISSN 1424-8220). This special issue belongs to the section "Physical Sensors".

Deadline for manuscript submissions: closed (28 February 2010)

Special Issue Editors

Guest Editor
Prof. Dr. Wilmar Hernandez

Department of Computer Science and Electronics, Universidad Tecnica Particular de Loja-UTPL, Campus UTPL, Calle San Cayetano Alto s/n, PO Box: 1101608, Loja, Loja, Ecuador
Interests: intelligent sensors; mechanical sensors; electronics; instrumentation; optimal signal processing; robust and optimal control
Guest Editor
Prof. Dr. Jesus De Vicente

Universidad Politecnica de Madrid, ETSI Industriales, Calle Jose Gutierrez Abascal 2, 28006 Madrid, Spain
Interests: nanometrology; uncertainty estimation; confocal microscopy; laser interferometry; coordinate metrology at the nanoscale

Keywords

  • sensors
  • actuators
  • automotive sensors
  • intelligent sensors
  • intelligent materials
  • electronic instrumentation for sensors
  • robust and optimal control and signal processing applied to improve the performance of sensor systems
  • calibration
  • measurement uncertainty estimation
  • mathematical modelling of sensors

Published Papers (35 papers)

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Research

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Open AccessArticle Field Evaluation of Polymer Capacitive Humidity Sensors for Bowen Ratio Energy Balance Flux Measurements
Sensors 2010, 10(8), 7748-7771; doi:10.3390/s100807748
Received: 28 June 2010 / Revised: 20 July 2010 / Accepted: 5 August 2010 / Published: 20 August 2010
Cited by 11 | PDF Full-text (1470 KB) | HTML Full-text | XML Full-text
Abstract
The possibility of reliable, reasonably accurate and relatively inexpensive estimates of sensible heat and latent energy fluxes was investigated using a commercial combination thin-film polymer capacitive relative humidity and adjacent temperature sensor instrument. Long-term and unattended water vapour pressure profile difference measurements [...] Read more.
The possibility of reliable, reasonably accurate and relatively inexpensive estimates of sensible heat and latent energy fluxes was investigated using a commercial combination thin-film polymer capacitive relative humidity and adjacent temperature sensor instrument. Long-term and unattended water vapour pressure profile difference measurements using low-power combination instruments were compared with those from a cooled dewpoint mirror hygrometer, the latter often used with Bowen ratio energy balance (BREB) systems. An error analysis, based on instrument relative humidity and temperature errors, was applied for various capacitive humidity instrument models. The main disadvantage of a combination capacitive humidity instrument is that two measurements, relative humidity and temperature, are required for estimation of water vapour pressure as opposed to one for a dewpoint hygrometer. In a laboratory experiment using an automated procedure, water vapour pressure differences generated using a reference dewpoint generator were measured using a commercial model (Dew-10) dewpoint hygrometer and a combination capacitive humidity instrument. The laboratory measurement comparisons showed that, potentially, an inexpensive model combination capacitive humidity instrument (CS500 or HMP50), or for improved results a slightly more expensive model (HMP35C or HMP45C), could substitute for the more expensive dewpoint hygrometer. In a field study, in a mesic grassland, the water vapour pressure measurement noise for the combination capacitive humidity instruments was greater than that for the dewpoint hygrometer. The average water vapour pressure profile difference measured using a HMP45C was highly correlated with that from a dewpoint hygrometer with a slope less than unity. Water vapour pressure measurements using the capacitive humidity instruments were not as accurate, compared to those obtained using a dewpoint hygrometer, but the resolution magnitudes for the profile difference measurements were less than the minimum of 0.01 kPa required for BREB measurements when averaged over 20 min. Furthermore, the longer-term capacitive humidity measurements are more reliable and not dependent on a sensor bias adjustment as is the case for the dewpoint hygrometer. A field comparison of CS500 and HMP45C profile water vapour pressure differences yielded a slope of close to unity. However, the CS500 exhibited more variable water vapour pressure measurements mainly due to its increased variation in temperature measurements compared to the HMP45C. Comparisons between 20-min BREB sensible heat fluxes obtained using a HMP45C and a dewpoint hygrometer yielded a slope of almost unity. BREB sensible heat fluxes measured using a HMP45C were reasonably well correlated with those obtained using a surface-layer scintillometer and eddy covariance (slope of 0.9629 and 0.9198 respectively). This reasonable agreement showed that a combination capacitive humidity instrument, with similar relative humidity (RH) and temperature error magnitudes of at most 2% RH and 0.3 °C respectively, and similar measurement time response, would be an adequate and less expensive substitute for a dewpoint hygrometer. Furthermore, a combination capacitive humidity instrument requires no servicing compared to a dewpoint hygrometer which requires a bias adjustment and mirror cleaning each week. These findings make unattended BREB measurements of sensible heat flux and evaporation cheaper and more reliable with the system easier to assemble and service and with reduced instrument power. Full article
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Open AccessArticle Mobile Calibration Based on Laser Metrology and Approximation Networks
Sensors 2010, 10(8), 7681-7704; doi:10.3390/s100807681
Received: 30 June 2010 / Revised: 20 July 2010 / Accepted: 5 August 2010 / Published: 17 August 2010
Cited by 3 | PDF Full-text (640 KB) | HTML Full-text | XML Full-text
Abstract
A mobile calibration technique for three-dimensional vision is presented. In this method, vision parameters are computed automatically by approximation networks built based on the position of a camera and image processing of a laser line. The networks also perform three-dimensional visualization. In [...] Read more.
A mobile calibration technique for three-dimensional vision is presented. In this method, vision parameters are computed automatically by approximation networks built based on the position of a camera and image processing of a laser line. The networks also perform three-dimensional visualization. In the proposed system, the setup geometry can be modified online, whereby an online re-calibration is performed based on data provided by the network and the required modifications of extrinsic and intrinsic parameters are thus determined, overcoming any calibration limitations caused by the modification procedure. The mobile calibration also avoids procedures involving references, which are used in traditional online re-calibration methods. The proposed mobile calibration thus improves the accuracy and performance of the three-dimensional vision because online data of calibrated references are not passed on to the vision system. This work represents a contribution to the field of online re-calibration, as verified by a comparison with the results based on lighting methods, which are calibrated and re-calibrated via perspective projection. Processing time is also studied. Full article
Open AccessArticle Performance Evaluation of Triangulation Based Range Sensors
Sensors 2010, 10(8), 7192-7215; doi:10.3390/s100807192
Received: 5 July 2010 / Revised: 23 July 2010 / Accepted: 27 July 2010 / Published: 29 July 2010
Cited by 14 | PDF Full-text (1874 KB) | HTML Full-text | XML Full-text
Abstract
The performance of 2D digital imaging systems depends on several factors related with both optical and electronic processing. These concepts have originated standards, which have been conceived for photographic equipment and bi-dimensional scanning systems, and which have been aimed at estimating different [...] Read more.
The performance of 2D digital imaging systems depends on several factors related with both optical and electronic processing. These concepts have originated standards, which have been conceived for photographic equipment and bi-dimensional scanning systems, and which have been aimed at estimating different parameters such as resolution, noise or dynamic range. Conversely, no standard test protocols currently exist for evaluating the corresponding performances of 3D imaging systems such as laser scanners or pattern projection range cameras. This paper is focused on investigating experimental processes for evaluating some critical parameters of 3D equipment, by extending the concepts defined by the ISO standards to the 3D domain. The experimental part of this work concerns the characterization of different range sensors through the extraction of their resolution, accuracy and uncertainty from sets of 3D data acquisitions of specifically designed test objects whose geometrical characteristics are known in advance. The major objective of this contribution is to suggest an easy characterization process for generating a reliable comparison between the performances of different range sensors and to check if a specific piece of equipment is compliant with the expected characteristics. Full article
Open AccessArticle Comparison of Several Methods for Determining the Internal Resistance of Lithium Ion Cells
Sensors 2010, 10(6), 5604-5625; doi:10.3390/s100605604
Received: 28 January 2010 / Revised: 25 March 2010 / Accepted: 18 May 2010 / Published: 3 June 2010
Cited by 30 | PDF Full-text (742 KB) | HTML Full-text | XML Full-text
Abstract
The internal resistance is the key parameter for determining power, energy efficiency and lost heat of a lithium ion cell. Precise knowledge of this value is vital for designing battery systems for automotive applications. Internal resistance of a cell was determined by [...] Read more.
The internal resistance is the key parameter for determining power, energy efficiency and lost heat of a lithium ion cell. Precise knowledge of this value is vital for designing battery systems for automotive applications. Internal resistance of a cell was determined by current step methods, AC (alternating current) methods, electrochemical impedance spectroscopy and thermal loss methods. The outcomes of these measurements have been compared with each other. If charge or discharge of the cell is limited, current step methods provide the same results as energy loss methods. Full article
Open AccessArticle Integration of a Multi-Camera Vision System and Strapdown Inertial Navigation System (SDINS) with a Modified Kalman Filter
Sensors 2010, 10(6), 5378-5394; doi:10.3390/s100605378
Received: 1 April 2010 / Revised: 20 April 2010 / Accepted: 10 May 2010 / Published: 28 May 2010
Cited by 9 | PDF Full-text (1145 KB) | HTML Full-text | XML Full-text
Abstract
This paper describes the development of a modified Kalman filter to integrate a multi-camera vision system and strapdown inertial navigation system (SDINS) for tracking a hand-held moving device for slow or nearly static applications over extended periods of time. In this algorithm, [...] Read more.
This paper describes the development of a modified Kalman filter to integrate a multi-camera vision system and strapdown inertial navigation system (SDINS) for tracking a hand-held moving device for slow or nearly static applications over extended periods of time. In this algorithm, the magnitude of the changes in position and velocity are estimated and then added to the previous estimation of the position and velocity, respectively. The experimental results of the hybrid vision/SDINS design show that the position error of the tool tip in all directions is about one millimeter RMS. The proposed Kalman filter removes the effect of the gravitational force in the state-space model. As a result, the resulting error is eliminated and the resulting position is smoother and ripple-free. Full article
Open AccessArticle Detecting Nano-Scale Vibrations in Rotating Devices by Using Advanced Computational Methods
Sensors 2010, 10(5), 4983-4995; doi:10.3390/s100504983
Received: 3 March 2010 / Revised: 27 April 2010 / Accepted: 6 May 2010 / Published: 18 May 2010
Cited by 1 | PDF Full-text (730 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents a computational method for detecting vibrations related to eccentricity in ultra precision rotation devices used for nano-scale manufacturing. The vibration is indirectly measured via a frequency domain analysis of the signal from a piezoelectric sensor attached to the stationary [...] Read more.
This paper presents a computational method for detecting vibrations related to eccentricity in ultra precision rotation devices used for nano-scale manufacturing. The vibration is indirectly measured via a frequency domain analysis of the signal from a piezoelectric sensor attached to the stationary component of the rotating device. The algorithm searches for particular harmonic sequences associated with the eccentricity of the device rotation axis. The detected sequence is quantified and serves as input to a regression model that estimates the eccentricity. A case study presents the application of the computational algorithm during precision manufacturing processes. Full article
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Open AccessArticle A Power-Efficient Bio-Potential Acquisition Device with DS-MDE Sensors for Long-Term Healthcare Monitoring Applications
Sensors 2010, 10(5), 4777-4793; doi:10.3390/s100504777
Received: 2 March 2010 / Revised: 21 April 2010 / Accepted: 27 April 2010 / Published: 11 May 2010
Cited by 11 | PDF Full-text (522 KB) | HTML Full-text | XML Full-text
Abstract
This work describes a power-efficient bio-potential acquisition device for long-term healthcare applications that is implemented using novel microelectromechanical dry electrodes (MDE) and a low power bio-potential processing chip. Using micromachining technology, an attempt is also made to enhance the sensing reliability and [...] Read more.
This work describes a power-efficient bio-potential acquisition device for long-term healthcare applications that is implemented using novel microelectromechanical dry electrodes (MDE) and a low power bio-potential processing chip. Using micromachining technology, an attempt is also made to enhance the sensing reliability and stability by fabricating a diamond-shaped MDE (DS-MDE) that has a satisfactory self-stability capability and superior electric conductivity when attached onto skin without any extra skin tissue injury technology. To acquire differential bio-potentials such as ECG signals, the proposed processing chip fabricated in a standard CMOS process has a high common mode rejection ratio (C.M.R.R.) differential amplifier and a 12-bit analog-to-digital converter (ADC). Use of the proposed system and integrate simple peripheral commercial devices can obtain the ECG signal efficiently without additional skin tissue injury and ensure continuous monitoring more than 70 hours with a 400 mAh battery. Full article
Open AccessArticle A Multi-D-Shaped Optical Fiber for Refractive Index Sensing
Sensors 2010, 10(5), 4794-4804; doi:10.3390/s100504794
Received: 10 March 2010 / Revised: 29 March 2010 / Accepted: 14 April 2010 / Published: 11 May 2010
Cited by 30 | PDF Full-text (630 KB) | HTML Full-text | XML Full-text
Abstract
A novel class of multi-D-shaped optical fiber suited for refractive index measurements is presented. The multi-D-shaped optical fiber was constructed by forming several D-sections in a multimode optical fiber at localized regions with femtosecond laser pulses. The total number of D-shaped zones [...] Read more.
A novel class of multi-D-shaped optical fiber suited for refractive index measurements is presented. The multi-D-shaped optical fiber was constructed by forming several D-sections in a multimode optical fiber at localized regions with femtosecond laser pulses. The total number of D-shaped zones fabricated could range from three to seven. Each D-shaped zone covered a sensor volume of 100 μm depth, 250 μm width, and 1 mm length. The mean roughness of the core surface obtained by the AFM images was 231.7 nm, which is relatively smooth. Results of the tensile test indicated that the fibers have sufficient mechanical strength to resist damage from further processing. The multi-D-shaped optical fiber as a high sensitive refractive-index sensor to detect changes in the surrounding refractive index was studied. The results for different concentrations of sucrose solution show that a resolution of 1.27 × 103–3.13 × 10−4 RIU is achieved for refractive indices in the range of 1.333 to 1.403, suggesting that the multi-D-shaped fibers are attractive for chemical, biological, and biochemical sensing with aqueous solutions. Full article
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Open AccessArticle GPCA vs. PCA in Recognition and 3-D Localization of Ultrasound Reflectors
Sensors 2010, 10(5), 4825-4837; doi:10.3390/s100504825
Received: 25 February 2010 / Revised: 20 April 2010 / Accepted: 7 May 2010 / Published: 11 May 2010
Cited by 2 | PDF Full-text (341 KB) | HTML Full-text | XML Full-text
Abstract
In this paper, a new method of classification and localization of reflectors, using the time-of-flight (TOF) data obtained from ultrasonic transducers, is presented. The method of classification and localization is based on Generalized Principal Component Analysis (GPCA) applied to the TOF values [...] Read more.
In this paper, a new method of classification and localization of reflectors, using the time-of-flight (TOF) data obtained from ultrasonic transducers, is presented. The method of classification and localization is based on Generalized Principal Component Analysis (GPCA) applied to the TOF values obtained from a sensor that contains four ultrasound emitters and 16 receivers. Since PCA works with vectorized representations of TOF, it does not take into account the spatial locality of receivers. The GPCA works with two-dimensional representations of TOF, taking into account information on the spatial position of the receivers. This report includes a detailed description of the method of classification and localization and the results of achieved tests with three types of reflectors in 3-D environments: planes, edges, and corners. The results in terms of processing time, classification and localization were very satisfactory for the reflectors located in the range of 50–350 cm. Full article
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Open AccessArticle Signal Existence Verification (SEV) for GPS Low Received Power Signal Detection Using the Time-Frequency Approach
Sensors 2010, 10(5), 4717-4738; doi:10.3390/s100504717
Received: 29 March 2010 / Revised: 30 April 2010 / Accepted: 4 May 2010 / Published: 10 May 2010
Cited by 2 | PDF Full-text (1451 KB) | HTML Full-text | XML Full-text
Abstract
The detection of low received power of global positioning system (GPS) signals in the signal acquisition process is an important issue for GPS applications. Improving the miss-detection problem of low received power signal is crucial, especially for urban or indoor environments. This [...] Read more.
The detection of low received power of global positioning system (GPS) signals in the signal acquisition process is an important issue for GPS applications. Improving the miss-detection problem of low received power signal is crucial, especially for urban or indoor environments. This paper proposes a signal existence verification (SEV) process to detect and subsequently verify low received power GPS signals. The SEV process is based on the time-frequency representation of GPS signal, and it can capture the characteristic of GPS signal in the time-frequency plane to enhance the GPS signal acquisition performance. Several simulations and experiments are conducted to show the effectiveness of the proposed method for low received power signal detection. The contribution of this work is that the SEV process is an additional scheme to assist the GPS signal acquisition process in low received power signal detection, without changing the original signal acquisition or tracking algorithms. Full article
Open AccessCommunication Intelligent Gearbox Diagnosis Methods Based on SVM, Wavelet Lifting and RBR
Sensors 2010, 10(5), 4602-4621; doi:10.3390/s100504602
Received: 22 March 2010 / Revised: 19 April 2010 / Accepted: 27 April 2010 / Published: 4 May 2010
Cited by 12 | PDF Full-text (674 KB) | HTML Full-text | XML Full-text
Abstract
Given the problems in intelligent gearbox diagnosis methods, it is difficult to obtain the desired information and a large enough sample size to study; therefore, we propose the application of various methods for gearbox fault diagnosis, including wavelet lifting, a support vector [...] Read more.
Given the problems in intelligent gearbox diagnosis methods, it is difficult to obtain the desired information and a large enough sample size to study; therefore, we propose the application of various methods for gearbox fault diagnosis, including wavelet lifting, a support vector machine (SVM) and rule-based reasoning (RBR). In a complex field environment, it is less likely for machines to have the same fault; moreover, the fault features can also vary. Therefore, a SVM could be used for the initial diagnosis. First, gearbox vibration signals were processed with wavelet packet decomposition, and the signal energy coefficients of each frequency band were extracted and used as input feature vectors in SVM for normal and faulty pattern recognition. Second, precision analysis using wavelet lifting could successfully filter out the noisy signals while maintaining the impulse characteristics of the fault; thus effectively extracting the fault frequency of the machine. Lastly, the knowledge base was built based on the field rules summarized by experts to identify the detailed fault type. Results have shown that SVM is a powerful tool to accomplish gearbox fault pattern recognition when the sample size is small, whereas the wavelet lifting scheme can effectively extract fault features, and rule-based reasoning can be used to identify the detailed fault type. Therefore, a method that combines SVM, wavelet lifting and rule-based reasoning ensures effective gearbox fault diagnosis. Full article
Open AccessArticle Time Delay for Aerial Ammonia Concentration Measurements in Livestock Buildings
Sensors 2010, 10(5), 4634-4642; doi:10.3390/s100504634
Received: 1 March 2010 / Revised: 29 March 2010 / Accepted: 15 April 2010 / Published: 4 May 2010
Cited by 12 | PDF Full-text (171 KB) | HTML Full-text | XML Full-text
Abstract
Correct measurements of ammonia concentration in air still present considerable challenges. The high water solubility and polarity can cause it to adsorb on surfaces in the entire sampling system, including sampling lines, filters, valves, pumps and instruments, causing substantial measuring errors and [...] Read more.
Correct measurements of ammonia concentration in air still present considerable challenges. The high water solubility and polarity can cause it to adsorb on surfaces in the entire sampling system, including sampling lines, filters, valves, pumps and instruments, causing substantial measuring errors and time delays. To estimate time delay characteristics of a Photo Acoustic Multi Gas Monitor 1312 and a Multi Point Sampler continuous measurement of aerial ammonia concentrations at different levels was performed. In order to obtain reproducible data, a wind tunnel was used to generate selected concentrations inside and a background concentration representing the air inlet of the tunnel. Four different concentration levels (0.8 ppm, 6.2 ppm, 9.7 ppm and 13.7 ppm) were used in the experiments, with an additional outdoor concentration level as background. The results indicated a substantial time delay when switching between the measuring positions with high and low concentration and vice versa. These properties may course serious errors for estimation of e.g. gas emissions whenever more than one measuring channel is applied. To reduce the measurement errors, some suggestions regarding design of the measurement setup and measuring strategies were presented. Full article
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Open AccessArticle Alternative Sensor System and MLP Neural Network for Vehicle Pedal Activity Estimation
Sensors 2010, 10(4), 3798-3814; doi:10.3390/s100403798
Received: 19 January 2010 / Revised: 21 February 2010 / Accepted: 22 March 2010 / Published: 14 April 2010
Cited by 6 | PDF Full-text (562 KB) | HTML Full-text | XML Full-text
Abstract
It is accepted that the activity of the vehicle pedals (i.e., throttle, brake, clutch) reflects the driver’s behavior, which is at least partially related to the fuel consumption and vehicle pollutant emissions. This paper presents a solution to estimate the driver activity [...] Read more.
It is accepted that the activity of the vehicle pedals (i.e., throttle, brake, clutch) reflects the driver’s behavior, which is at least partially related to the fuel consumption and vehicle pollutant emissions. This paper presents a solution to estimate the driver activity regardless of the type, model, and year of fabrication of the vehicle. The solution is based on an alternative sensor system (regime engine, vehicle speed, frontal inclination and linear acceleration) that reflects the activity of the pedals in an indirect way, to estimate that activity by means of a multilayer perceptron neural network with a single hidden layer. Full article
Open AccessArticle Error Analysis in a Stereo Vision-Based Pedestrian Detection Sensor for Collision Avoidance Applications
Sensors 2010, 10(4), 3741-3758; doi:10.3390/s100403741
Received: 25 January 2010 / Revised: 18 March 2010 / Accepted: 23 March 2010 / Published: 13 April 2010
Cited by 16 | PDF Full-text (910 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents an analytical study of the depth estimation error of a stereo vision-based pedestrian detection sensor for automotive applications such as pedestrian collision avoidance and/or mitigation. The sensor comprises two synchronized and calibrated low-cost cameras. Pedestrians are detected by combining [...] Read more.
This paper presents an analytical study of the depth estimation error of a stereo vision-based pedestrian detection sensor for automotive applications such as pedestrian collision avoidance and/or mitigation. The sensor comprises two synchronized and calibrated low-cost cameras. Pedestrians are detected by combining a 3D clustering method with Support Vector Machine-based (SVM) classification. The influence of the sensor parameters in the stereo quantization errors is analyzed in detail providing a point of reference for choosing the sensor setup according to the application requirements. The sensor is then validated in real experiments. Collision avoidance maneuvers by steering are carried out by manual driving. A real time kinematic differential global positioning system (RTK-DGPS) is used to provide ground truth data corresponding to both the pedestrian and the host vehicle locations. The performed field test provided encouraging results and proved the validity of the proposed sensor for being used in the automotive sector towards applications such as autonomous pedestrian collision avoidance. Full article
Open AccessArticle Optimal Filters with Multiple Packet Losses and its Application in Wireless Sensor Networks
Sensors 2010, 10(4), 3330-3350; doi:10.3390/s100403330
Received: 28 January 2010 / Revised: 16 March 2010 / Accepted: 25 March 2010 / Published: 6 April 2010
Cited by 6 | PDF Full-text (343 KB) | HTML Full-text | XML Full-text
Abstract
This paper is concerned with the filtering problem for both discrete-time stochastic linear (DTSL) systems and discrete-time stochastic nonlinear (DTSN) systems. In DTSL systems, an linear optimal filter with multiple packet losses is designed based on the orthogonal principle analysis approach over [...] Read more.
This paper is concerned with the filtering problem for both discrete-time stochastic linear (DTSL) systems and discrete-time stochastic nonlinear (DTSN) systems. In DTSL systems, an linear optimal filter with multiple packet losses is designed based on the orthogonal principle analysis approach over unreliable wireless sensor networks (WSNs), and the experience result verifies feasibility and effectiveness of the proposed linear filter; in DTSN systems, an extended minimum variance filter with multiple packet losses is derived, and the filter is extended to the nonlinear case by the first order Taylor series approximation, which is successfully applied to unreliable WSNs. An application example is given and the corresponding simulation results show that, compared with extended Kalman filter (EKF), the proposed extended minimum variance filter is feasible and effective in WSNs. Full article
Open AccessArticle A FDR Sensor for Measuring Complex Soil Dielectric Permittivity in the 10–500 MHz Frequency Range
Sensors 2010, 10(4), 3314-3329; doi:10.3390/s100403314
Received: 3 February 2010 / Revised: 5 March 2010 / Accepted: 19 March 2010 / Published: 5 April 2010
Cited by 30 | PDF Full-text (1704 KB) | HTML Full-text | XML Full-text
Abstract
Mechanical details as well as electrical models of FDR (frequency domain reflectometry) sensors for the measurement of the complex dielectric permittivity of porous materials are presented. The sensors are formed from two stainless steel parallel waveguides of various lengths. Using the data [...] Read more.
Mechanical details as well as electrical models of FDR (frequency domain reflectometry) sensors for the measurement of the complex dielectric permittivity of porous materials are presented. The sensors are formed from two stainless steel parallel waveguides of various lengths. Using the data from VNA (vector network analyzer) with the connected FDR sensor and selected models of the applied sensor it was possible obtain the frequency spectrum of dielectric permittivity from 10 to 500 MHz of reference liquids and soil samples of various moisture and salinity. The performance of the analyzed sensors were compared with TDR (time domain reflectometry) ones of similar mechanical construction. Full article
Open AccessArticle A New Myohaptic Instrument to Assess Wrist Motion Dynamically
Sensors 2010, 10(4), 3180-3194; doi:10.3390/s100403180
Received: 19 January 2010 / Revised: 11 February 2010 / Accepted: 24 March 2010 / Published: 1 April 2010
Cited by 4 | PDF Full-text (534 KB) | HTML Full-text | XML Full-text
Abstract
The pathophysiological assessment of joint properties and voluntary motion in neurological patients remains a challenge. This is typically the case in cerebellar patients, who exhibit dysmetric movements due to the dysfunction of cerebellar circuitry. Several tools have been developed, but so far [...] Read more.
The pathophysiological assessment of joint properties and voluntary motion in neurological patients remains a challenge. This is typically the case in cerebellar patients, who exhibit dysmetric movements due to the dysfunction of cerebellar circuitry. Several tools have been developed, but so far most of these tools have remained confined to laboratories, with a lack of standardization. We report on a new device which combines the use of electromyographic (EMG) sensors with haptic technology for the dynamic investigation of wrist properties. The instrument is composed of a drivetrain, a haptic controller and a signal acquisition unit. Angular accuracy is 0.00611 rad, nominal torque is 6 N·m, maximal rotation velocity is 34.907 rad/sec, with a range of motion of –1.0472 to +1.0472 rad. The inertia of the motor and handgrip is 0.004 kg·m². This is the first standardized myohaptic instrument allowing the dynamic characterization of wrist properties, including under the condition of artificial damping. We show that cerebellar patients are unable to adapt EMG activities when faced with an increase in damping while performing fast reversal movements. The instrument allows the extraction of an electrophysiological signature of a cerebellar deficit. Full article
Open AccessArticle Evaluation of Performance and Uncertainty of Infrared Tympanic Thermometers
Sensors 2010, 10(4), 3073-3089; doi:10.3390/s100403073
Received: 21 February 2010 / Revised: 13 March 2010 / Accepted: 23 March 2010 / Published: 31 March 2010
Cited by 6 | PDF Full-text (260 KB) | HTML Full-text | XML Full-text
Abstract
Infrared tympanic thermometers (ITTs) are easy to use and have a quick response time. They are widely used for temperature measurement of the human body. The accuracy and uncertainty of measurement is the importance performance indicator for these meters. The performance of [...] Read more.
Infrared tympanic thermometers (ITTs) are easy to use and have a quick response time. They are widely used for temperature measurement of the human body. The accuracy and uncertainty of measurement is the importance performance indicator for these meters. The performance of two infrared tympanic thermometers, Braun THT-3020 and OMRON MC-510, were evaluated in this study. The cell of a temperature calibrator was modified to serve as the standard temperature of the blackbody. The errors of measurement for the two meters were reduced by the calibration equation. The predictive values could meet the requirements of the ASTM standard. The sources of uncertainty include the standard deviations of replication at fixed temperature or the predicted values of calibration equation, reference standard values and resolution. The uncertainty analysis shows that the uncertainty of calibration equation is the main source for combined uncertainty. Ambient temperature did not have the significant effects on the measured performance. The calibration equations could improve the accuracy of ITTs. However, these equations did not improve the uncertainty of ITTs. Full article
Open AccessArticle Efficiency of Event-Based Sampling According to Error Energy Criterion
Sensors 2010, 10(3), 2242-2261; doi:10.3390/s100302242
Received: 23 December 2009 / Revised: 5 February 2010 / Accepted: 24 February 2010 / Published: 18 March 2010
Cited by 14 | PDF Full-text (231 KB) | HTML Full-text | XML Full-text
Abstract
The paper belongs to the studies that deal with the effectiveness of the particular event-based sampling scheme compared to the conventional periodic sampling as a reference. In the present study, the event-based sampling according to a constant energy of sampling error is [...] Read more.
The paper belongs to the studies that deal with the effectiveness of the particular event-based sampling scheme compared to the conventional periodic sampling as a reference. In the present study, the event-based sampling according to a constant energy of sampling error is analyzed. This criterion is suitable for applications where the energy of sampling error should be bounded (i.e., in building automation, or in greenhouse climate monitoring and control). Compared to the integral sampling criteria, the error energy criterion gives more weight to extreme sampling error values. The proposed sampling principle extends a range of event-based sampling schemes and makes the choice of particular sampling criterion more flexible to application requirements. In the paper, it is proved analytically that the proposed event-based sampling criterion is more effective than the periodic sampling by a factor defined by the ratio of the maximum to the mean of the cubic root of the signal time-derivative square in the analyzed time interval. Furthermore, it is shown that the sampling according to energy criterion is less effective than the send-on-delta scheme but more effective than the sampling according to integral criterion. On the other hand, it is indicated that higher effectiveness in sampling according to the selected event-based criterion is obtained at the cost of increasing the total sampling error defined as the sum of errors for all the samples taken. Full article
Open AccessArticle Automatic Chessboard Detection for Intrinsic and Extrinsic Camera Parameter Calibration
Sensors 2010, 10(3), 2027-2044; doi:10.3390/s100302027
Received: 6 January 2010 / Revised: 29 January 2010 / Accepted: 2 February 2010 / Published: 15 March 2010
Cited by 38 | PDF Full-text (2539 KB) | HTML Full-text | XML Full-text
Abstract
There are increasing applications that require precise calibration of cameras to perform accurate measurements on objects located within images, and an automatic algorithm would reduce this time consuming calibration procedure. The method proposed in this article uses a pattern similar to that [...] Read more.
There are increasing applications that require precise calibration of cameras to perform accurate measurements on objects located within images, and an automatic algorithm would reduce this time consuming calibration procedure. The method proposed in this article uses a pattern similar to that of a chess board, which is found automatically in each image, when no information regarding the number of rows or columns is supplied to aid its detection. This is carried out by means of a combined analysis of two Hough transforms, image corners and invariant properties of the perspective transformation. Comparative analysis with more commonly used algorithms demonstrate the viability of the algorithm proposed, as a valuable tool for camera calibration. Full article
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Open AccessArticle Wide Dynamic Range CMOS Potentiostat for Amperometric Chemical Sensor
Sensors 2010, 10(3), 1782-1797; doi:10.3390/s100301782
Received: 1 December 2009 / Revised: 1 February 2010 / Accepted: 2 February 2010 / Published: 4 March 2010
Cited by 12 | PDF Full-text (603 KB) | HTML Full-text | XML Full-text
Abstract
Presented is a single-ended potentiostat topology with a new interface connection between sensor electrodes and potentiostat circuit to avoid deviation of cell voltage and linearly convert the cell current into voltage signal. Additionally, due to the increased harmonic distortion quantity when detecting [...] Read more.
Presented is a single-ended potentiostat topology with a new interface connection between sensor electrodes and potentiostat circuit to avoid deviation of cell voltage and linearly convert the cell current into voltage signal. Additionally, due to the increased harmonic distortion quantity when detecting low-level sensor current, the performance of potentiostat linearity which causes the detectable current and dynamic range to be limited is relatively decreased. Thus, to alleviate these irregularities, a fully-differential potentiostat is designed with a wide output voltage swing compared to single-ended potentiostat. Two proposed potentiostats were implemented using TSMC 0.18-μm CMOS process for biomedical application. Measurement results show that the fully differential potentiostat performs relatively better in terms of linearity when measuring current from 500 ºpA to 10 uA. Besides, the dynamic range value can reach a value of 86 dB. Full article
Open AccessArticle Machine Learning Methods for Classifying Human Physical Activity from On-Body Accelerometers
Sensors 2010, 10(2), 1154-1175; doi:10.3390/s100201154
Received: 31 December 2009 / Revised: 26 January 2010 / Accepted: 26 January 2010 / Published: 1 February 2010
Cited by 122 | PDF Full-text (836 KB) | HTML Full-text | XML Full-text
Abstract
The use of on-body wearable sensors is widespread in several academic and industrial domains. Of great interest are their applications in ambulatory monitoring and pervasive computing systems; here, some quantitative analysis of human motion and its automatic classification are the main computational [...] Read more.
The use of on-body wearable sensors is widespread in several academic and industrial domains. Of great interest are their applications in ambulatory monitoring and pervasive computing systems; here, some quantitative analysis of human motion and its automatic classification are the main computational tasks to be pursued. In this paper, we discuss how human physical activity can be classified using on-body accelerometers, with a major emphasis devoted to the computational algorithms employed for this purpose. In particular, we motivate our current interest for classifiers based on Hidden Markov Models (HMMs). An example is illustrated and discussed by analysing a dataset of accelerometer time series. Full article
Open AccessArticle Cooperative Anchor-Free Position Estimation for Hierarchical Wireless Sensor Networks
Sensors 2010, 10(2), 1176-1215; doi:10.3390/s100201176
Received: 30 December 2009 / Revised: 27 January 2010 / Accepted: 27 January 2010 / Published: 1 February 2010
Cited by 5 | PDF Full-text (719 KB) | HTML Full-text | XML Full-text
Abstract
This paper proposes a distributed algorithm for establishing connectivity and location estimation in cluster-based wireless sensor networks. The algorithm exploits the information flow while coping with distributed signal processing and the requirements of network scalability. Once the estimation procedure and communication protocol [...] Read more.
This paper proposes a distributed algorithm for establishing connectivity and location estimation in cluster-based wireless sensor networks. The algorithm exploits the information flow while coping with distributed signal processing and the requirements of network scalability. Once the estimation procedure and communication protocol are performed, sensor clusters can be merged to establish a single global coordinate system without GPS sensors using only distance information. In order to adjust the sensor positions, the refinement schemes and cooperative fusion approaches are applied to reduce the estimation error and improve the measurement accuracy. This paper outlines the technical foundations of the localization techniques and presents the tradeoffs in algorithm design. The feasibility of the proposed schemes is shown to be effective under certain assumptions and the analysis is supported by simulation and numerical studies. Full article
Open AccessArticle Using Fuzzy Logic to Enhance Stereo Matching in Multiresolution Images
Sensors 2010, 10(2), 1093-1118; doi:10.3390/100201093
Received: 10 December 2009 / Revised: 14 January 2010 / Accepted: 18 January 2010 / Published: 29 January 2010
Cited by 1 | PDF Full-text (1148 KB) | HTML Full-text | XML Full-text
Abstract
Stereo matching is an open problem in Computer Vision, for which local features are extracted to identify corresponding points in pairs of images. The results are heavily dependent on the initial steps. We apply image decomposition in multiresolution levels, for reducing the [...] Read more.
Stereo matching is an open problem in Computer Vision, for which local features are extracted to identify corresponding points in pairs of images. The results are heavily dependent on the initial steps. We apply image decomposition in multiresolution levels, for reducing the search space, computational time, and errors. We propose a solution to the problem of how deep (coarse) should the stereo measures start, trading between error minimization and time consumption, by starting stereo calculation at varying resolution levels, for each pixel, according to fuzzy decisions. Our heuristic enhances the overall execution time since it only employs deeper resolution levels when strictly necessary. It also reduces errors because it measures similarity between windows with enough details. We also compare our algorithm with a very fast multi-resolution approach, and one based on fuzzy logic. Our algorithm performs faster and/or better than all those approaches, becoming, thus, a good candidate for robotic vision applications. We also discuss the system architecture that efficiently implements our solution. Full article
Open AccessArticle Improving the Response of Accelerometers for Automotive Applications by Using LMS Adaptive Filters: Part II
Sensors 2010, 10(1), 952-962; doi:10.3390/s100100952
Received: 22 December 2009 / Revised: 15 January 2010 / Accepted: 25 January 2010 / Published: 26 January 2010
Cited by 3 | PDF Full-text (1381 KB) | HTML Full-text | XML Full-text
Abstract
In this paper, the fast least-mean-squares (LMS) algorithm was used to both eliminate noise corrupting the important information coming from a piezoresisitive accelerometer for automotive applications, and improve the convergence rate of the filtering process based on the conventional LMS algorithm. The [...] Read more.
In this paper, the fast least-mean-squares (LMS) algorithm was used to both eliminate noise corrupting the important information coming from a piezoresisitive accelerometer for automotive applications, and improve the convergence rate of the filtering process based on the conventional LMS algorithm. The response of the accelerometer under test was corrupted by process and measurement noise, and the signal processing stage was carried out by using both conventional filtering, which was already shown in a previous paper, and optimal adaptive filtering. The adaptive filtering process relied on the LMS adaptive filtering family, which has shown to have very good convergence and robustness properties, and here a comparative analysis between the results of the application of the conventional LMS algorithm and the fast LMS algorithm to solve a real-life filtering problem was carried out. In short, in this paper the piezoresistive accelerometer was tested for a multi-frequency acceleration excitation. Due to the kind of test conducted in this paper, the use of conventional filtering was discarded and the choice of one adaptive filter over the other was based on the signal-to-noise ratio improvement and the convergence rate. Full article
Open AccessArticle Intelligent Sensors Security
Sensors 2010, 10(1), 822-859; doi:10.3390/s100100822
Received: 16 December 2009 / Revised: 19 January 2010 / Accepted: 19 January 2010 / Published: 22 January 2010
Cited by 6 | PDF Full-text (778 KB) | HTML Full-text | XML Full-text
Abstract
The paper is focused on the security issues of sensors provided with processors and software and used for high-risk applications. Common IT related threats may cause serious consequences for sensor system users. To improve their robustness, sensor systems should be developed in [...] Read more.
The paper is focused on the security issues of sensors provided with processors and software and used for high-risk applications. Common IT related threats may cause serious consequences for sensor system users. To improve their robustness, sensor systems should be developed in a restricted way that would provide them with assurance. One assurance creation methodology is Common Criteria (ISO/IEC 15408) used for IT products and systems. The paper begins with a primer on the Common Criteria, and then a general security model of the intelligent sensor as an IT product is discussed. The paper presents how the security problem of the intelligent sensor is defined and solved. The contribution of the paper is to provide Common Criteria (CC) related security design patterns and to improve the effectiveness of the sensor development process. Full article
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Open AccessArticle Vision-Based Traffic Data Collection Sensor for Automotive Applications
Sensors 2010, 10(1), 860-875; doi:10.3390/s100100860
Received: 1 December 2009 / Revised: 19 January 2010 / Accepted: 20 January 2010 / Published: 22 January 2010
Cited by 10 | PDF Full-text (1260 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents a complete vision sensor onboard a moving vehicle which collects the traffic data in its local area in daytime conditions. The sensor comprises a rear looking and a forward looking camera. Thus, a representative description of the traffic conditions [...] Read more.
This paper presents a complete vision sensor onboard a moving vehicle which collects the traffic data in its local area in daytime conditions. The sensor comprises a rear looking and a forward looking camera. Thus, a representative description of the traffic conditions in the local area of the host vehicle can be computed. The proposed sensor detects the number of vehicles (traffic load), their relative positions and their relative velocities in a four-stage process: lane detection, candidates selection, vehicles classification and tracking. Absolute velocities (average road speed) and global positioning are obtained after combining the outputs provided by the vision sensor with the data supplied by the CAN Bus and a GPS sensor. The presented experiments are promising in terms of detection performance and accuracy in order to be validated for applications in the context of the automotive industry. Full article
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Open AccessArticle The Non-linear Relationship between Muscle Voluntary Activation Level and Voluntary Force Measured by the Interpolated Twitch Technique
Sensors 2010, 10(1), 796-807; doi:10.3390/s100100796
Received: 4 December 2009 / Revised: 8 January 2010 / Accepted: 15 January 2010 / Published: 21 January 2010
Cited by 5 | PDF Full-text (258 KB) | HTML Full-text | XML Full-text
Abstract
Interpolated twitch technique (ITT) is a non-invasive method for assessing the completeness of muscle activation in clinical settings. Voluntary activation level (VA), measured by ITT and estimated by a conventional linear model, was reported to have a non-linear relationship with true voluntary [...] Read more.
Interpolated twitch technique (ITT) is a non-invasive method for assessing the completeness of muscle activation in clinical settings. Voluntary activation level (VA), measured by ITT and estimated by a conventional linear model, was reported to have a non-linear relationship with true voluntary contraction force at higher activation levels. The relationship needs to be further clarified for the correct use by clinicians and researchers. This study was to established a modified voluntary activation (modified VA) and define a valid range by fitting a non-linear logistic growth model. Eight healthy male adults participated in this study. Each subject performed three sets of voluntary isometric ankle plantar flexions at 20, 40, 60, 80 and 100% maximal voluntary contraction (MVC) with real-time feedback on a computer screen. A supramaximal electrical stimulation was applied on tibia nerve at rest and during contractions. The estimated VA was calculated for each contraction. The relationship between the estimated VA and the actual voluntary contraction force was fitted by a logistic growth model. The result showed that according to the upper and lower limit points of the logistic curve, the valid range was between the 95.16% and 10.55% MVC. The modified VA estimated by this logistic growth model demonstrated less error than the conventional model. This study provided a transfer function for the voluntary activation level and defined the valid range which would provide useful information in clinical applications. Full article
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Open AccessArticle Improving the Response of Accelerometers for Automotive Applications by Using LMS Adaptive Filters
Sensors 2010, 10(1), 313-329; doi:10.3390/s100100313
Received: 9 December 2009 / Revised: 29 December 2009 / Accepted: 30 December 2009 / Published: 31 December 2009
Cited by 9 | PDF Full-text (941 KB) | HTML Full-text | XML Full-text
Abstract
In this paper, the least-mean-squares (LMS) algorithm was used to eliminate noise corrupting the important information coming from a piezoresisitive accelerometer for automotive applications. This kind of accelerometer is designed to be easily mounted in hard to reach places on vehicles under [...] Read more.
In this paper, the least-mean-squares (LMS) algorithm was used to eliminate noise corrupting the important information coming from a piezoresisitive accelerometer for automotive applications. This kind of accelerometer is designed to be easily mounted in hard to reach places on vehicles under test, and they usually feature ranges from 50 to 2,000 g (where is the gravitational acceleration, 9.81 m/s2) and frequency responses to 3,000 Hz or higher, with DC response, durable cables, reliable performance and relatively low cost. However, here we show that the response of the sensor under test had a lot of noise and we carried out the signal processing stage by using both conventional and optimal adaptive filtering. Usually, designers have to build their specific analog and digital signal processing circuits, and this fact increases considerably the cost of the entire sensor system and the results are not always satisfactory, because the relevant signal is sometimes buried in a broad-band noise background where the unwanted information and the relevant signal sometimes share a very similar frequency band. Thus, in order to deal with this problem, here we used the LMS adaptive filtering algorithm and compare it with others based on the kind of filters that are typically used for automotive applications. The experimental results are satisfactory. Full article
Open AccessArticle Algorithmic Error Correction of Impedance Measuring Sensors
Sensors 2009, 9(12), 10341-10355; doi:10.3390/s91210341
Received: 3 November 2009 / Revised: 14 December 2009 / Accepted: 16 December 2009 / Published: 21 December 2009
Cited by 1 | PDF Full-text (896 KB) | HTML Full-text | XML Full-text
Abstract
This paper describes novel design concepts and some advanced techniques proposed for increasing the accuracy of low cost impedance measuring devices without reduction of operational speed. The proposed structural method for algorithmic error correction and iterating correction method provide linearization of transfer [...] Read more.
This paper describes novel design concepts and some advanced techniques proposed for increasing the accuracy of low cost impedance measuring devices without reduction of operational speed. The proposed structural method for algorithmic error correction and iterating correction method provide linearization of transfer functions of the measuring sensor and signal conditioning converter, which contribute the principal additive and relative measurement errors. Some measuring systems have been implemented in order to estimate in practice the performance of the proposed methods. Particularly, a measuring system for analysis of C-V, G-V characteristics has been designed and constructed. It has been tested during technological process control of charge-coupled device CCD manufacturing. The obtained results are discussed in order to define a reasonable range of applied methods, their utility, and performance. Full article
Open AccessArticle Registration Combining Wide and Narrow Baseline Feature Tracking Techniques for Markerless AR Systems
Sensors 2009, 9(12), 10097-10116; doi:10.3390/s91210097
Received: 19 October 2009 / Revised: 11 December 2009 / Accepted: 2 December 2009 / Published: 11 December 2009
Cited by 7 | PDF Full-text (937 KB) | HTML Full-text | XML Full-text
Abstract
Augmented reality (AR) is a field of computer research which deals with the combination of real world and computer generated data. Registration is one of the most difficult problems currently limiting the usability of AR systems. In this paper, we propose a [...] Read more.
Augmented reality (AR) is a field of computer research which deals with the combination of real world and computer generated data. Registration is one of the most difficult problems currently limiting the usability of AR systems. In this paper, we propose a novel natural feature tracking based registration method for AR applications. The proposed method has following advantages: (1) it is simple and efficient, as no man-made markers are needed for both indoor and outdoor AR applications; moreover, it can work with arbitrary geometric shapes including planar, near planar and non planar structures which really enhance the usability of AR systems. (2) Thanks to the reduced SIFT based augmented optical flow tracker, the virtual scene can still be augmented on the specified areas even under the circumstances of occlusion and large changes in viewpoint during the entire process. (3) It is easy to use, because the adaptive classification tree based matching strategy can give us fast and accurate initialization, even when the initial camera is different from the reference image to a large degree. Experimental evaluations validate the performance of the proposed method for online pose tracking and augmentation. Full article
Open AccessArticle Vehicle Lateral State Estimation Based on Measured Tyre Forces
Sensors 2009, 9(11), 8761-8775; doi:10.3390/s91108761
Received: 16 September 2009 / Revised: 14 October 2009 / Accepted: 21 October 2009 / Published: 30 October 2009
Cited by 13 | PDF Full-text (800 KB) | HTML Full-text | XML Full-text
Abstract
Future active safety systems need more accurate information about the state of vehicles. This article proposes a method to evaluate the lateral state of a vehicle based on measured tyre forces. The tyre forces of two tyres are estimated from optically measured [...] Read more.
Future active safety systems need more accurate information about the state of vehicles. This article proposes a method to evaluate the lateral state of a vehicle based on measured tyre forces. The tyre forces of two tyres are estimated from optically measured tyre carcass deflections and transmitted wirelessly to the vehicle body. The two remaining tyres are so-called virtual tyre sensors, the forces of which are calculated from the real tyre sensor estimates. The Kalman filter estimator for lateral vehicle state based on measured tyre forces is presented, together with a simple method to define adaptive measurement error covariance depending on the driving condition of the vehicle. The estimated yaw rate and lateral velocity are compared with the validation sensor measurements. Full article

Review

Jump to: Research

Open AccessReview Measurement Uncertainty Estimation in Amperometric Sensors: A Tutorial Review
Sensors 2010, 10(5), 4430-4455; doi:10.3390/s100504430
Received: 26 February 2010 / Revised: 29 March 2010 / Accepted: 10 April 2010 / Published: 30 April 2010
Cited by 12 | PDF Full-text (295 KB) | HTML Full-text | XML Full-text
Abstract
This tutorial focuses on measurement uncertainty estimation in amperometric sensors (both for liquid and gas-phase measurements). The main uncertainty sources are reviewed and their contributions are discussed with relation to the principles of operation of the sensors, measurement conditions and properties of [...] Read more.
This tutorial focuses on measurement uncertainty estimation in amperometric sensors (both for liquid and gas-phase measurements). The main uncertainty sources are reviewed and their contributions are discussed with relation to the principles of operation of the sensors, measurement conditions and properties of the measured samples. The discussion is illustrated by case studies based on the two major approaches for uncertainty evaluation–the ISO GUM modeling approach and the Nordtest approach. This tutorial is expected to be of interest to workers in different fields of science who use measurements with amperometric sensors and need to evaluate the uncertainty of the obtained results but are new to the concept of measurement uncertainty. The tutorial is also expected to be educative in order to make measurement results more accurate. Full article
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Open AccessReview Optoelectronic Capillary Sensors in Microfluidic and Point-of-Care Instrumentation
Sensors 2010, 10(4), 3771-3797; doi:10.3390/s100403771
Received: 15 February 2010 / Revised: 10 March 2010 / Accepted: 30 March 2010 / Published: 14 April 2010
Cited by 18 | PDF Full-text (489 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents a review, based on the published literature and on the authors’ own research, of the current state of the art of fiber-optic capillary sensors and related instrumentation as well as their applications, with special emphasis on point-of-care chemical and [...] Read more.
This paper presents a review, based on the published literature and on the authors’ own research, of the current state of the art of fiber-optic capillary sensors and related instrumentation as well as their applications, with special emphasis on point-of-care chemical and biochemical sensors, systematizing the various types of sensors from the point of view of the principles of their construction and operation. Unlike classical fiber-optic sensors which rely on changes in light propagation inside the fiber as affected by outside conditions, optical capillary sensors rely on changes of light transmission in capillaries filled with the analyzed liquid, which opens the possibility of interesting new applications, while raising specific issues relating to the construction, materials and instrumentation of those sensors. Full article
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Open AccessReview Neurological Tremor: Sensors, Signal Processing and Emerging Applications
Sensors 2010, 10(2), 1399-1422; doi:10.3390/s100201399
Received: 23 December 2009 / Revised: 22 January 2010 / Accepted: 20 February 2010 / Published: 24 February 2010
Cited by 18 | PDF Full-text (1254 KB) | HTML Full-text | XML Full-text
Abstract
Neurological tremor is the most common movement disorder, affecting more than 4% of elderly people. Tremor is a non linear and non stationary phenomenon, which is increasingly recognized. The issue of selection of sensors is central in the characterization of tremor. This [...] Read more.
Neurological tremor is the most common movement disorder, affecting more than 4% of elderly people. Tremor is a non linear and non stationary phenomenon, which is increasingly recognized. The issue of selection of sensors is central in the characterization of tremor. This paper reviews the state-of-the-art instrumentation and methods of signal processing for tremor occurring in humans. We describe the advantages and disadvantages of the most commonly used sensors, as well as the emerging wearable sensors being developed to assess tremor instantaneously. We discuss the current limitations and the future applications such as the integration of tremor sensors in BCIs (brain-computer interfaces) and the need for sensor fusion approaches for wearable solutions. Full article
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