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All-fiber quasi-distributed polarimetric temperature sensor
Denis Đonlagić, Miran Lešič, 2006, original scientific article

Abstract: This paper presents an all-fiber design of a quasi-distributed polarimetric temperature sensor array that utilizes commercially available single polarization and high birefringence fibers. The modulation depth of temperature induced loss and the operational temperature range of individual sensors in the network are set by the rotational alignment of fibers before fusion splicing and through fine adjustment of the sensing fiber lengths. A practical sensor network was built with sensors that operated in the temperature range from 0 to 100 C. Individual sensors in the network generatedtemperature dependent loss that changed proportionally from 0.9 to 1.8 dB. With current standard telecommunication OTDRs, more than 20 prototype sensors could be interrogated.
Keywords: fiber optics, sensors, temperature measurements, polarization, alignement, birefringence, polarization maintaining
Published: 31.05.2012; Views: 1038; Downloads: 5
URL Full text (0,00 KB)

Software and equipment for remote testing of sensors
Barbara Brezovec, Vojko Matko, 2007, original scientific article

Abstract: An improved approach for remote testing of elements and systems is presented in this article. To ensure high reliability of products, tests must be done in the production phase to detect possible errors in working mode. Because environmental testing involves long-term processes the possibility of remote observation and remote controlling of tests is very useful solution. The concept is to connect the testing chamber with a personal computer, create a reliable driver and control it remotely over the local network or Internet from other client. It is designed for performing tests on wide area of sensors and sensor based systems.
Keywords: sensors reliability, testing methods, remote control, virtual instruments
Published: 31.05.2012; Views: 819; Downloads: 9
.pdf Full text (243,72 KB)

Quasi-distributed long-gauge fiber optic sensor system
Matjaž Linec, Denis Đonlagić, 2009, original scientific article

Abstract: This paper presents a quasi-distributed, long-gauge, sensor system for measurement optical path length variation. This system can be directly applied to long gauge strain and/or temperature sensing. The proposed sensor system is comprised of sensing fiber, which is divided into the sensorćs segments separated by semi reflective mirrors made out of standard optical connectors. Short duration radio-frequency modulated optical bursts are launched into the sensing fiber and phase differences among individual reflected bursts are measured to determine the optical path-length variations among neighboring mirrors. Twenty sensing fiber segments were successfully addressed by a single-signal processor, while relying on standard telecommunication PIN diode, and a Fabry Perot laser diode. The resolution of a fiber-length variation better than 5 ìm was demonstrated in practice. Since the long sections of fiber can be employed for constructing individual sensors within the sensor's array, a microstrain resolution can be achieved in practice. The drift of the sensorćs system can be predominantly attributed to the temperature sensitivity of the electronic components, which proved to be below 20 um/°C. The entire system relies on simple and widely-used components that are low-cost.
Keywords: fiber optic systems, fiber optics sensors, sensing fiber, long-gauge, strain sensing, temperature sensing, optoelectronics
Published: 31.05.2012; Views: 959; Downloads: 8
URL Full text (0,00 KB)

Optical chemical sensors : design and applications
Aleksandra Lobnik, Matejka Turel, Špela Korent Urek, 2012, independent scientific component part or a chapter in a monograph

Keywords: optical chemical sensors, opt(r)odes, chemical sensors
Published: 01.06.2012; Views: 812; Downloads: 5
URL Full text (0,00 KB)

Sol-gel-based optical sensor for the detection of aqueous amines
Špela Korent Urek, Aleksandra Lobnik, Gerhard J. Mohr, 2007, original scientific article

Abstract: We present an optical sensor for the detection of aqueous amines obtained by incorporating chromoionophore XV (ETHT 4001) into sol-gel thin films. Acid- and base-catalyzed sol-gel processes were studied to prepare stable ormosil layers using various amounts of organically modified sol-gel precursor such asmethyltriethoxysilane (MTriEOS). The sensor layers were coated with a protective layer of microporous white polytetrafluoroethylene (PTFE) in order to prevent interference from ions and ambient light. The measurements were carried out in a flow-through cell in the reflection mode. Acid-catalyzed ormosil layers (pH 1) based on the copolymerization of tetraethoxysilane (TEOS) and MTriEOS did not show any change in signal upon exposure to aqueous amine solutions, while base-catalyzed sensor layers (pH 3 and 13) showed significant changes in signal. The response time (t100) for the base-catalyzedsensor layer L3 (pH 13) upon exposure to different solutions containing 0-608 mmol L-1 aqueous propylamine was 20-30 s, the regeneration time was 70 s and the detection limit was 0.1 mmol L-1. The sensor response was reproducible and reversible. The porous ormosil layers permit dry sensor storage conditions.
Keywords: analytical chemistry, optical sensors, sol-gel technology, determination of amines, fluorimetry
Published: 01.06.2012; Views: 1212; Downloads: 4
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Characterisation of an optical sensor membrane based on the metal ion indication Pyrocatechol Violet
Ivana Murković Steinberg, Aleksandra Lobnik, Otto S. Wolfbeis, 2003, original scientific article

Abstract: A non-specific photometric metal ion indicator Pyrocatechol Violet (PV) was tested for its potential use in a metal-sensitive optrode membrane. The water soluble indicator was lipophilised in the form of an ion pair with tetraoctylammonium cation (TOA), and subsequently immobilised in a plasticised PVC membrane. The spectral response of the membrane in the presence of various transition metal ions was studied. It was found that the ability of PV to form complexes with metal ions significantly reduced following immobilisation, with the exception of Cu(II). A number of factors responsible for the improved selectivity and high sensitivity of immobilised PV towards Cu(II) were identified. Amongst those, the most important is the presence of quaternary ammonium salt in the membrane which induced a significant bathochromic shift of the PV-Cu(II) chelate absorption maximum, as well as the intensification of the chelate absorption band. The membrane responds to Cu(II) irreversibly by changing colour from yellow to green (absorption maximum at 740 nm), and typically, an exposure time of 10 min enables the determination of Cu(II) in the 1-100 M range. A comparison of selectivity and sensitivity characteristics between the water soluble form of the indicator and the immobilised form was performed, and the effects of pH and lipophilic surfactant additives on the response mechanism are discussed.
Keywords: optical sensors, sensor membrane, PVC membrane, photometric metal ion indicators, metal-sensitive optrode membrane, lipophilic ion pairs
Published: 01.06.2012; Views: 707; Downloads: 4
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Bluetooth platform for wireless measurements using industrial sensors
Kristian Les, Tadej Tašner, Darko Lovrec, 2013, original scientific article

Abstract: The past decade has seen significant advancement in the field of mobile devices. Various smart devices such as cellular phones, tablets and PDAs have become universal tools in our everyday lives. Their versatility is based on their computing power, portability and their integration with other devices and services such as the World Wide Web. However, these smart devices have an even wider usability spectrum. They can also be used for wireless industrial measurements using existing sensors. The wireless connectivity of existing industrial sensors is achieved by equipping them with a Bluetooth module, which digitizes the data and passes it to any Bluetooth capable smart device for further processing, evaluation and logging. This paper describes the specially designed Bluetooth platform for wireless measurements all the way from the basic concept, through hardware, firmware and software implementation, to the sample tests and measurements.
Keywords: sensors, wireless, bluetooth, data acquisition, condition monitoring
Published: 10.07.2015; Views: 187; Downloads: 5
.pdf Full text (1,02 MB)

Spin-coating for optical-oxigen-sensor preparation
Polona Brglez, Andrej Holobar, Aleksandra Pivec, Mitja Kolar, 2014, original scientific article

Abstract: Thin-film oxygen sensors were prepared using the spin-coating technique, where a tris (4,7-diphenyl-1,10-phenanthroline) ruthenium(II) dichloride complex (RuDPP) in various solvents and silicones deposited on different substrates was used for the sensor production. By changing the spin-coating set-up parameters, homogeneous sensor coatings and the optimum sensor response to oxygen were studied – the sensors were exposed to various concentrations of oxygen within the range from 0% to 100 %. During the presented study, the optimum results were obtained when a 150 µL of sensor solution was applied to a Dataline foil using silicone E4 and a chloroform solvent. A spin coater with the following three rotation stages was used: 750/700 r/min for 3 s, 300 r/min for 3 s and 150 r/min for 4 s. The spin-coating technique has several benefits: it is fast, easy to use and appropriate for low-volume operations. It allows modifications and preparations of several sensor series using the minimum reagent consumption. However, the disadvantage of this technique also has to be mentioned, namely, an uneven film thickness in the radial direction. The film thickness mainly depends on the experimental set-up (volume, rotation time and speed, solvent viscosity and evaporation). Spin coating as an alternative and very flexible technique for an oxygen-sensor preparation is suggested for the laboratory-scale work, where the majority of experimental data could be used when other new coating methods are also researched and implemented.
Keywords: optical sensors, spin coating, oxigen
Published: 21.12.2015; Views: 409; Downloads: 1
.pdf Full text (254,63 KB)

Membrane potential and calcium dynamics in beta cells from mouse pancreas tissue slices
Marjan Rupnik, Andraž Stožer, Jurij Dolenšek, Borut Žalik, Maša Skelin, Marko Gosak, Denis Špelič, 2015, review article

Abstract: Beta cells in the pancreatic islets of Langerhans are precise biological sensors for glucose and play a central role in balancing the organism between catabolic and anabolic needs. A hallmark of the beta cell response to glucose are oscillatory changes of membrane potential that are tightly coupled with oscillatory changes in intracellular calcium concentration which, in turn, elicit oscillations of insulin secretion. Both membrane potential and calcium changes spread from one beta cell to the other in a wave-like manner. In order to assess the properties of the abovementioned responses to physiological and pathological stimuli, the main challenge remains how to effectively measure membrane potential and calcium changes at the same time with high spatial and temporal resolution, and also in as many cells as possible. To date, the most wide-spread approach has employed the electrophysiological patch-clamp method to monitor membrane potential changes. Inherently, this technique has many advantages, such as a direct contact with the cell and a high temporal resolution. However, it allows one to assess information from a single cell only. In some instances, this technique has been used in conjunction with CCD camera-based imaging, offering the opportunity to simultaneously monitor membrane potential and calcium changes, but not in the same cells and not with a reliable cellular or subcellular spatial resolution. Recently, a novel family of highly-sensitive membrane potential reporter dyes in combination with high temporal and spatial confocal calcium imaging allows for simultaneously detecting membrane potential and calcium changes in many cells at a time. Since the signals yielded from both types of reporter dyes are inherently noisy, we have developed complex methods of data denoising that permit for visualization and pixel-wise analysis of signals. Combining the experimental approach of high-resolution imaging with the advanced analysis of noisy data enables novel physiological insights and reassessment of current concepts in unprecedented detail.
Keywords: calcium sensors, membrane potential sensors, calcium imaging, membrane potential imaging, beta cell, pancreas, denoising, patch-clamp
Published: 22.06.2017; Views: 127; Downloads: 6
.pdf Full text (4,17 MB)

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