Showing papers in "Instrumentation viewpoint in 2013"

Water fraction measurement using a RF resonant cavity sensor

Abstract: Abstrac t We have tested the working principle of water fraction measurement using a Radio Frequency (RF) resonant cavity sensor. This technology allows us to determine the water fraction by the frequency shift of the first resonant peak in a non-intrusive way. The sensor operates with low power signals (1 mW) in the range of 100 through 400 MHz. Static measurements were done using a Scalar Network Analyzer (SNA) for water/oil and water/air static mixtures with fresh water and sea water. The measurement’s uncertainty and the characteristic curves of the sensor’s behavior were computed.

Defining frequency domain performance of Analog-to-Information Converters

Abstract: Lluís Ferrer-Arnau164, Xavier Roset165, Vicenç Parisi-Baradad165 The paper deals with the definition of dynamic performance of Analog-to-Information Converters (AICs). These components allow to overcome the sampling frequency limits of the Shannon theorem, by assuming that the observed signal has a sparse representation in a given domain. The paper aims to verify the behaviour of standard parameters currently defined for Analog-to-Digital Converters when applied to these new devices. To this aim, several simulations and experimental tests have been carried out to study the influence, in the frequency domain, of quantization noise and nonlinearity on the AIC dynamic parameters.

On compressed sensing and super-resolution in DFT-based spectral analysis

Abstract: Abstrac t -The paper discusses a novel frequency interpolation and super-resolution method for multitone waveform analysis, where a compressive sensing algorithm is employed to process data. Each signal acquisition involves a short data record, whose DFT coefficients are computed. A set of compressed measurements is obtained by taking records with different known starting instants, and employed to determine, by solving an orthogonal matching pursuit problem, the set of frequency components of the analysed waveform. Interpolation is presented as a compressed sensing problem and algorithm performances discussed.

PSD estimation in Cognitive Radio systems: a performance analysis

Abstract: Abstrac t -To meet the demanding expectations of the users, nowadays radio systems have to use the spectrum resource more intensely than in the past. Several studies have demonstrated that portions of radio spectrum are not in use for significant periods of time. Cognitive radios systems have been conceived to overcome this limit, enabling a flexible spectrum allocation, and making a more intensive and efficient spectrum use by the users sharing spectrum access. To meet this goal, cognitive radio terminals have to dynamically select the appropriate operating frequency based on the sensing of signals emitted by other transmitters. The paper focuses the attention on the performance analysis of a spectrum sensing based on the energy detection method. In particular, several power spectrum estimation methods are investigated in order to compare them mainly in terms of overall computational burden and algorithm performance.

Uncertainty factors in time-interval measurements in ballistocardiography

Abstract: There is a growing interest on measuring time intervals between the J peak of the ballistocardiogram (BCG) and several features of other cardiovascular signals such as the ECG in order to obtain cardiovascular function markers. Nevertheless, possible uncertainty factors involved in these measurements have not been identified and analyzed, which is a necessary step to advance towards standardization in this reemerging biomedical engineering field. In this paper we analyze the effect of the low-pass cutoff frequency and phase characteristic of filters, noise and power line interference on J-peak time measurement. We conclude that BCG acquisition systems require a minimum low-pass cutoff frequency of 25 Hz but the phase angle of filters at this frequency introduce more than 6 ms delay that increases with increasing filter order. Further, SNR and power line interference levels respectively below about 25 dB and 30 dB, commonly found in data acquisition systems in this area, may lead to uncertainties in the time position of the J peak of tens of milliseconds, which are comparable to measured time interval changes that may have diagnostic interest.

Near surface oceanographic measurements using the sailbuoy

Abstract: SailBuoy SB02, fitted with a Neil Brown conductivity-temperature sensor and an Aanderaa Instruments oxygen optode, was deployed off Grand Canaria, Spain, in 13 November 2012. The mission duration was 22 days and the extent of the track coverage was approximately 140 km zonally and 220 km meridionally.

A real-time compensation method for MV voltage transducer for power quality analysis

Abstract: The growing need of power quality analysis in medium voltage grids leads to the employment of transducers with wider and wider bandwidth. This requirement is in contrast with the need of adopting a low cost hardware for capillary monitoring. Therefore, in this paper a technique for the extension of the frequency bandwidth of a MV voltage divider is presented. The performance of the compensated divider is comparable with that of dividers of better accuracy class, but the cost is kept low.

Low-frequency noise measurements in silicon power MOSFETs as a tool to experimentally investigate the defectiveness of the gate oxide

Abstract: July 18th and 19th 2013 Barcelona 47 In this work, we implemented a low-noise laboratory set-up and related numerical processing techniques that allow to perform accurate LF noise measurements in power MOSFETs The experimental results confirmed the suitability of this measurement technique to analyse the gate oxide quality in silicon trench power MOSFETs Moreover, from a general standpoint, this kind of empirical investigation allows to select the most suitable physical model for the compact description of 1/f-like fluctuations of the drain current In particular in this paper, by measuring the LF noise spectra as a function of the gate voltage bias level, we proved that the so-called McWorther number fluctuation model is appropriate for the device technology considered Thus, this model was adopted, in association with the experimental data, in order to estimate the trap density in the gate oxide Schematic of the LF noise measurement system for power MOSFETs Low-Frequency Noise Measurements in Silicon Power MOSFETs as a Tool to Experimentally Investigate the Defectiveness of the Gate Oxide Paolo Magnone114, Pier Andrea Traverso115, Giacomo Barletta116, Claudio Fiegna114,115 14AS060

Double squirrel cage induction motors : a new approach to detect rotor bar failures

Abstract: July 18th and 19th 2013 Barcelona 43 At every time, all FlexRIO cards are adjusting its internal clocks trying to put in phase with the PXI-6682 timing card, by a hardware mechanisim. This method makes easy to obtain static measurement errors in the drift. Avoiding the use of software elements makes the system an accurate solution to distribute the IEEE1588 Clock to every DAQ in the system. The maximum absolute value of drift obtained between PTP timing card and every RIO/FlexRIO devices is less than 200 ns. The value for the sampling rate can be up to 2.5MS/s without Time-Stamp overlaping.

On the setup of an operational autonomous underwater glider facility

Abstract: We present the evolution, from its conception until today, of an established and internationally recognized Glider Facility. During 8 years of glider activity, new infrastructures and methodologies have been developed increasing glider missions, data, quality and availability. From 2005 to 2010, IMEDEA operated 4 Slocum G1 gliders following a research project approach. Since 2011, SOCIB, with in kind contribution from IMEDEA, is in charge of gliders’ operation and maintenance, increasing the glider fleet with 4 new vehicles (2 Slocum G2 gliders and 2 iRobot Seagliders). SOCIB has established one permanent endurance line in the Balearic Islands and provides open access glider time to third parties. We describe the progress of the Glider Facility, the results obtained and the objectives and actions foreseen in the near future.

Cloud nowcasting: motion analysis of all-sky images using velocity fields

Abstract: July 18th and 19th 2013 Barcelona 61 Cloud monitoring and prediction is crucial to air traffic and weather forecast. Clouds play a key role in solar radiation balance. These issues have prompted Sieltec Canarias S.L. and AEMET to develop an automatic system of cloud observation (SONA). This system provides cloud cover percentage using all-sky images and data from a multichannel photometer, which are processed by neural networks. Once the system has detected and recorded cloud images, a cloud motion technique makes possible to obtain several “velocity fields”, corresponding to different layers of clouds. The evolution in time of these velocity fields is a powerful tool to provide very short term forecasting (less than 1 hour) of cloudiness (known as cloud nowcasting). In the future, this information, combined with Radiative Transfer Models, may be used to predict solar radiation (Global Horizontal Irradiance –GHIand Direct Normal Irradiance –DNI-) (A) Original image. (B) Image analysed by the neural network with cloud pixels marked as green. (C) Image with two clustered velocity fields marked as green and yellow, respectively. Cloud Nowcasting: Motion Analysis of All-sky images using velocity Fields Yezer Gonzalez148, Cesar Lopez148, Emilio Cuevas149 17VS053

Precision timing in TDMA-based Wireless Sensor Network through IEEE 1588 standard

Abstract: Abstrac t This paper proposes an energy-efficient time synchronization scheme for Wireless Sensor Networks (WSNs) based on the IEEE 1588 standard. Although a number of methods have been studied for time synchronization of WSNs, some applications require high precision time synchronization with very low power consumption. This paper presents a reduced implementation of IEEE 1588 precision time protocol (PTP) for WSNs. Within the proposed synchronization approach, a sensor node is synchronized using the timing message generated by a master node synchronized with GPS. This paper also presents experiments to evaluate the performance of the precision time synchronization of a slave-master pair of sensor nodes.

On the use of complex excitation sequences for eddy current testing

Abstract: Eddy Current Testing (ECT) are widely used in many industrial application fields where is very important to detect the presence of thin defects (cracks) in conductive materials and to characterize their geometrical characteristics. The analysis of these characteristics allows the user accepting or discarding realized components and improving the production chain. In the measurement process the choice of signal type, frequency and amplitude to be adopted in the excitation stage is a critical issue to be accomplished for. In different application fields, the actual research on ECT is considering excitation signals different to the sinusoidal ones. In this paper the authors propose an experimental comparison of different excitation signal designed to improve the quality of experimental data when difficult cases are experienced (such as sub-superficial deep cracks) and consequently to obtain a more reliable extraction of defects geometrical features.

A novel capacitance-to-digital converter for capacitive sensors with AC excitation

Abstract: Several planar coil designs have been investigated for application in accurate AC conductivity measurements in the wide frequency range. The measurement method is based on the eddy-current probe-coils solutions proposed by Dodd and Deeds [1]. Coils parameters related to the theoretical model and measurement equipment used have been considered. The coil parameters affecting the performance of the model and the measurement instrument in the specified frequency range have been investigated. Different designs were investigated including coils on a printed circuit board (PCB), coils on flexible substrate and on site manufactured coils winded from a copper wire with different diameters. The goal was to reach the inductance of the different coils to match the best-accuracy of the measuring instrument. Amongst the others, the important factor was to achieve the diameter of the coils small enough for practical applications. Measured resistance (a) and inductance (b) deviations from 30 kHz value. Calculated conductivity deviations (c) from 30 kHz value. 15ST017

Electrical Impedance Spectroscopy cell monitoring in a miniaturized bioreactor

Abstract: Electrical impedance spectroscopy measurement of biologic materials provides information about viable cell density as well as cell size and shape homogeneity. Several experimental and even commercial biomass density probes have been developed both for cell suspensions and monolayer cell cultures in the last twenty years. This communication describes the development of a set of electrodes and circuits designed to add viable biomass density measurement capability to a set of single-use miniaturized bioreactors. Two applications: adherent animal cultures and generic cell suspension cultures drive to the need of providing two electrode sets and two measurement systems with different frequency ranges.

Measurement of landslide displacement and orientation using strain gauges based on amorphous magnetic microwires

Abstract: In this paper, we present the performance of a landslide transducer based on magnetic strain gauges and the interpretation of experimental results. Analysis of landslide data indicates that the land displacements measured with our transducer are correlated to the movements measured at the ground surface. Evaluating the landslide data, we have established a relationship between the system readings and the landslide movement. Measurements regarding landslide displacement and orientation ware done using strain gauges based on amorphous magnetic microwires (MAW). In order to evaluate a larger area, our system uses a grid of measurement points containing multiple measurement nodes. Each measurement node acquires displacement and orientation information reporting the data through RS485 to the central unit coordinator. Measurement information from central unit coordinators across the grid is transmitted wirelessly to a server for storage and alerting actions.

Evaluation of a laser based structured light system for 3D reconstruction of underwater environments

Abstract: Structure from motion or stereoscopy are used to obtain 3D from a sequence of still images. However if there is no texture or features in the images, no 3D can be obtained. Featureless environments are difficult to reconstruct in 3D using only cameras. Projected light patterns can be used to measure the shape or an object. However, scattering is the main problem in light based underwater sensors such as projectors and cameras. Collimated light such as laser minimizes this problems by focusing the light in fewer points. Ranged gated cameras can also be used with pulsed lasers to reduce even more the scattering. In this paper a new structured light laser system is evaluated to solve the scattering and featureless problems above mentioned and to perform a 3D underwater reconstruction. This system is formed by a laser projector and a camera. By means of pattern identification and triangulation, 3D can be reconstructed from a live video sequence of a featureless environment.

Advanced parameter measurement of energy storage systems for smart grids application

Abstract: July 18th and 19th 2013 Barcelona 59 The smart grid approach is envisioned to take advantage of all available modern technologies in transforming the current power system to provide benefits to all stakeholders first of all in the fields of efficient energy utilization and of wide integration of renewable sources. Energy storage systems, especially those based on batteries, could help to solve some issues that stem from the use of renewable energy, in terms of stabilizing the intermittent energy production, power quality and power peak mitigation. With the integration of energy storage systems into the smart grids, their accurate modelling becomes a necessity, in order to gain a robust real-time control on the network. In this framework, this paper proposes a procedure for a better identification of the battery model parameters in order to best fit experimental data. The proposed method is based on a hybrid optimization technique, which makes a combined use of a stochastic and a deterministic algorithm, and it has a low computational burden, therefore it can be repeated over the time in order to account parameter variations due to the battery age and usage Block scheme of the Measurement System. Advanced Parameter Measurement of Energy Storage Systems for Smart Grids application Daniele Gallo85, Carmine Landi85, Mario Luiso85 16IC104

Politolana, a new low cost towed vehicle designed for the characterization of the deep-sea floor

Abstract: The Politolana sled, designed by the Santander IEO in collaboration with the Marine Robotics Company, is a robust submarine towed vehicle to study the deep-sea floor (Figure 1). The vehicle operates hung of a simple coaxial cable, available on every oceanographic ships with hydrographic purposes, because of that are not necessary expensive operations of installation for special winches (with fiber optics cables, etc.) and deployment devices (LARS, frames, etc). The bidirectional telemetry to control the different submerged instruments is carried out using a cable modem NEXUS MKE from MacArtney that connect the Politolana sled to an industrial microcontroller that carries out the following functions: RS232 serial ports Multiplexing data from the different scientific instruments connected (altimeter, CTD probe, compass, video and still cameras control, rs232, etc.) and sends the data to surface correctly synchronized in real time. Also receives the surface orders to switch ON/OFF all the different peripherals connected to it (focuses, laser pointers, video camera and pictures, etc.). Besides, it integrate the necessary power supplies to feed the different instruments connected to it, and allows to carry out a real time supervision of tensions, current consumptions, state of fuses, alarms, etc. In the surface unit, the cable modem is connected to a 19” rack format computer, that executes an application which display all the telemetry data received from the bottom unit to a sled operator screen (Figure 2). The software save in a text file all the received data from the vehicle instruments for later study it in the laboratory, and finally send orders on real time to the submerged vehicle. This vehicle allows us to obtain simultaneously still pictures and video, georeferenced and synchronized with environmental variables. For this purpose, it uses a FullHD video camera, installed with an angle of 45° with respect to the bottom, and two LED last generation light (12600 lumens / 5800° Kelvin). This camera records in solid-state memory and MTS video format all the visual transect and incorporates 2 pointers of green laser (532 nm wave length) to facilitate the scaling of images. The signal provided by the video camera is visible in real time in the control unit located in surface (Figure 2), which facilitates the control of transect flight in structurally complex areas, such as the cold-water coral reefs. It also has a system of photogrammetry based on a Nikon D90 camera and 4 laser pointers located in zenithal position. It includes a powerful electronic Subtronic strobe with iTTL system, a Seabird 37 CTD probe to characterize each image according to the oceanographic features (pressure, temperature and salinity) and a sensor of vehicle heading, pitch and roll. The location of the vehicle on the bottom is obtained through a USBL (Ultra Short Base Line) transponder based on HiPAP 500 Kongsberg system. The vehicle can be operated up to a maximum of 2000 m depth and the transects were carried out with the vehicle navigating to 1 knot of speed at a altitude between 2 and 4 m over the sea floor. As the vehicle is powered from the surface using the coaxial cable, the visual transects duration is not limited by the batteries depletion. This system generates direct visual information in structurally complex deepsea areas, not accessible to the classic samplers (dredges, trawls, etc.), that are characterized by the presence of vulnerable biological communities. The high resolution of digital pictures allows us a better classification of the species that the video. Besides, the scaling of the image is more accurate, allowing to estimate the abundance and the percentage of coating of the different marine habitats. In addition it provides information about the complexity of habitats, the impact of fishing gear and complete listings of faunal species not accessible to the extractive sampling systems. One of the major utilities of this vehicle is to obtain high-resolution maps which are necessary in the management plans of Marine Protected Areas. Their operating costs and the needs of qualified technical personnel are much lower than those of the ROVs. On the other hand, allow us to access in a relatively safe way to environmental conditions, that are very difficult (rocky highs, strong currents, etc.) and dangerous (lost fishing gears, shipwreck, etc. ) and then inaccessible to AUVs.

Impedance simulator for automatic calibration of LCR meters : proof-of-principle experiment

Abstract: Abstrac t -The calibration of LCR meters is a time consuming task that requires the availability of many high accurate impedance standards. The use of an impedance simulator will greatly simplify this task and will permit the calibration of the LCR meter over the whole complex plan. The principle of such a new impedance simulator based on a sampling system is described. The first measurements carried out at 1 kHz using the impedance simulator are in good agreement with the results of the conventional calibration procedure using impedance standards. The unique feature of the impedance simulator to change independently the resistance and the phase of the simulated impedance will be a useful tool for testing and improving the performances of LCR meters.

Ultrasonic time of flight estimation for wind speed measurement based on time-frequency domain using STFT

Abstract: Abstrac t This paper presents a procedure for wind speed measurement using ultrasonic transducers based on short-time Fourier transform (STFT). The measurement of wind speed was performed by estimating the ultrasonic transit-time (ToF). For this purpose the estimated ToF was used the technique of digital signal processing, based on the STFT. The ultrasonic signal detection was performed by setting a threshold level equivalently half the maximum power for the operating frequency of the ultrasonic transducers. Simulation results are presented considering the influence of the additive noise Gaussian, and estimation of ToF considering the evaluation of STFT windows using Hamming, Hanning and Bartlett.

Identification of wire network topology using impedance spectroscopy

Abstract: Abstrac t -A new technique is proposed to locate wire faults and identify wire network topology using impedance spectroscopy (IS). The propagation along the cables is analytical, modelled with flexible multi section cascading features utilizing frequency dependent scattering parameters. Therefore, it doesn’t have the common numerical method problems. The transmission line model has the same spectrum as the measured reflection coefficient (ρ) of wire under test (WUT) so that same practical effects such as skin and proximity effects, signal loss, dispersion and frequency dependent signal propagation can be exactly incorporated. For determination of model parameters an inverse problem should be resolved and differential evolution (DE) approach is proposed. The novel method allows locating hard (short and open circuit) and soft (frays and junctions) faults and also for characterization of defects in the branches of network. Results are presented to validate and illustrate the performance of this proposed method.