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Monitoring the evaporation of fluids from fiber-optic micro-cell cavities
Eyal Preter, Borut Preložnik, Vlada Artel, Chaim Sukenik, Denis Đonlagić, Avi Zadok, 2013, izvirni znanstveni članek

Opis: Fiber-optic sensors provide remote access, are readily embedded within structures, and can operate in harsh environments. Nevertheless, fiber-optic sensing of liquids has been largely restricted to measurements of refractive index and absorption spectroscopy. The temporal dynamics of fluid evaporation have potential applications in monitoring the quality of water, identificationof fuel dilutions, mobile point-of-care diagnostics, climatography and more. In this work, the fiber-optic monitoring of fluids evaporation is proposed and demonstrated. Sub-nano-liter volumes of a liquid are applied to inline fiber-optic micro-cavities. As the liquid evaporates, light is refracted out of the cavity at the receding index boundary between the fluid and the ambient surroundings. A sharp transient attenuation in the transmission of light through the cavity, by as much as 50 dB and on a sub-second time scale, is observed. Numerical models for the transmission dynamics in terms of ray-tracing and wavefront propagation are provided. Experiments show that the temporal transmission profile can distinguish between different liquids.
Ključne besede: fiber-optic sensors, opto-fluidics, evaporation monitoring, optical micro-cells, fiber cavities, droplet analysis
Objavljeno: 22.06.2017; Ogledov: 35; Prenosov: 4
.pdf Celotno besedilo (551,58 KB)

Major improvements of quartz crystal pulling sensitivity and linearity using series reactance
Vojko Matko, Riko Šafarič, 2009, izvirni znanstveni članek

Opis: This paper presents a new method of substantially improving frequency pullability and linearity using reactance in series with an AT fundamental crystal operated with a series load capacitance in the range of 3 to 50 pF andfrequencies in the range of 3.5 to 21 MHz. The research describes high quartz pullability and linearity by varying the load capacitance. The paper also gives impedance circuits for crystal unit (3.5 MHz) together with load capacitance and compensation reactance. The experimental results show that thenew approach using compensation method of quartz crystal connected in series reactance increases the frequency pulling range by *25 to *100 depending on the type of oscillator and compensation factor k in the temperature range of 10 to 40 °C.
Ključne besede: quartz crystal, pulling range, pulling linearity
Objavljeno: 22.06.2017; Ogledov: 40; Prenosov: 5
.pdf Celotno besedilo (256,09 KB)

High resolution switching mode inductance-to-frequency converter with temperature compensation
Vojko Matko, Miro Milanovič, 2014, izvirni znanstveni članek

Opis: This article proposes a novel method for the temperature-compensated inductance-to-frequency converter with a single quartz crystal oscillating in the switching oscillating circuit to achieve better temperature stability of the converter. The novelty of this method lies in the switching-mode converter, the use of additionally connected impedances in parallel to the shunt capacitances of the quartz crystal, and two inductances in series to the quartz crystal. This brings a considerable reduction of the temperature influence of AT-cut crystal frequency change in the temperature range between 10 and 40 °C. The oscillator switching method and the switching impedances connected to the quartz crystal do not only compensate for the crystalʼs natural temperature characteristics but also any other influences on the crystal such as ageing as well as from other oscillating circuit elements. In addition, the method also improves frequency sensitivity in inductance measurements. The experimental results show that through high temperature compensation improvement of the quartz crystal characteristics, this switching method theoretically enables a 2 pH resolution. It converts inductance to frequency in the range of 85-100 nH to 2-560 kHz.
Ključne besede: inductance-to-frequency, switching methods, dynamic temperature compensation of circuit elements, precision metrology
Objavljeno: 22.06.2017; Ogledov: 39; Prenosov: 6
.pdf Celotno besedilo (2,22 MB)

Greatly improved small inductance measurement using quartz crystal parasitic capacitance compensation
Vojko Matko, Karel Jezernik, 2010, izvirni znanstveni članek

Opis: Generally, quartz crystal inductance frequency pulling in oscillators is very low and therefore is not often used in practice. The new method of improving frequencypullability uses inductance to compensate for quartz stray capacitances. To this end, a special AT fundamental quartz crystal working near the antiresonance frequency is selected. By modifying its equivalent circuit with load inductance and series tuning capacitance, the magnetic sensing of the circuit can be highly improved. The experimental results show that the new approach using the quartz crystal stray capacitance compensation method increases the frequency pulling range by x 300 depending on the type of oscillator, making possible the measurement of nano-magnetic changes.
Ključne besede: quartz crystal, magnetic pulling, parasitic capacitance compensation
Objavljeno: 22.06.2017; Ogledov: 51; Prenosov: 4
.pdf Celotno besedilo (145,07 KB)

Finite element modelling of a field-sensed magnetic suspended system for accurate proximity measurement based on a sensor fusion algorithm with Unscented Kalman Filter
Amor Chowdhury, Andrej Sarjaš, 2016, izvirni znanstveni članek

Opis: The presented paper describes accurate distance measurement for a field-sensed magnetic suspension system. The proximity measurement is based on a Hall effect sensor. The proximity sensor is installed directly on the lower surface of the electro-magnet, which means that it is very sensitive to external magnetic influences and disturbances. External disturbances interfere with the information signal and reduce the usability and reliability of the proximity measurements and, consequently, the whole application operation. A sensor fusion algorithm is deployed for the aforementioned reasons. The sensor fusion algorithm is based on the Unscented Kalman Filter, where a nonlinear dynamic model was derived with the Finite Element Modelling approach. The advantage of such modelling is a more accurate dynamic model parameter estimation, especially in the case when the real structure, materials and dimensions of the real-time application are known. The novelty of the paper is the design of a compact electro-magnetic actuator with a built-in low cost proximity sensor for accurate proximity measurement of the magnetic object. The paper successively presents a modelling procedure with the finite element method, design and parameter settings of a sensor fusion algorithm with Unscented Kalman Filter and, finally, the implementation procedure and results of real-time operation.
Ključne besede: accurate proximity measurement, sensor fusion algorithm, Unscented Kalman Filter, finite element modelling
Objavljeno: 22.06.2017; Ogledov: 81; Prenosov: 6
.pdf Celotno besedilo (9,23 MB)

Fiber-optic sensors for measurements of torsion, twist and rotation
Vedran Budinski, Denis Đonlagić, 2017, pregledni znanstveni članek

Opis: Optical measurement of mechanical parameters is gaining significant commercial interest in different industry sectors. Torsion, twist and rotation are among the very frequently measured mechanical parameters. Recently, twist/torsion/rotation sensors have become a topic of intense fiber-optic sensor research. Various sensing concepts have been reported. Many of those have different properties and performances, and many of them still need to be proven in out-of-the laboratory use. This paper provides an overview of basic approaches and a review of current state-of-the-art in fiber optic sensors for measurements of torsion, twist and/or rotation.
Ključne besede: fiber optic sensors, twist sensors, rotation sensors, circular birefringence, linear birefringence, FBG, polarization, optical fibers, Fiber Bragg Gratings
Objavljeno: 22.06.2017; Ogledov: 58; Prenosov: 8
.pdf Celotno besedilo (8,96 MB)

An EMI filter selection method based on spectrum of digital periodic signal
Marko Podberšič, Vojko Matko, Matjaž Šegula, 2006, izvirni znanstveni članek

Opis: This paper describes a new method for the selection of an appropriate signal lineElectromagnetic Interference (EMI) filter. To date, EMI filter selection has been based on the measurement of the radiation of the entire device. The new selection method based on the signal’s Fast Fourier Transform (FFT) measurement has proved to be efficient. The EMIfilter is optimized separately for each line. The method described in this paper involving aCentral Processor Unit (CPU) module demonstrates that the proposed FFT-based selection method is better than the radiation-based one. The radiation level in the frequency range 30MHz to 1 GHz is lower for approximate 2 – 6 dBμV/m.
Ključne besede: EMC, EMI filters, electrically long trace, typical frequency, sensor
Objavljeno: 22.06.2017; Ogledov: 45; Prenosov: 4
.pdf Celotno besedilo (189,00 KB)

Acoustic emission detection of macro-cracks on engraving tool steel inserts during the injection molding cycle using PZT sensors
Rajko Svečko, Dragan Kusić, Tomaž Kek, Andrej Sarjaš, Aleš Hančič, Janez Grum, 2013, izvirni znanstveni članek

Opis: This paper presents an improved monitoring system for the failure detection ofen graving tool steel inserts during the injection molding cycle. This system uses acoustic emission PZT sensors mounted through acoustic waveguides on the engraving insert. We were thus able to clearly distinguish the defect through measured AE signals. Two engraving tool steel inserts were tested during the production of standard test specimens, each under the same processing conditions. By closely comparing the captured AE signals on both engraving inserts during the filling and packing stages, we were able to detect the presence of macro-cracks on one engraving insert. Gabor wavelet analysis was used for closer examination of the captured AE signalsć peak amplitudes during the filling and packing stages. The obtained results revealed that such a system could be used successfully as an improved tool for monitoring the integrity of an injection molding process.
Ključne besede: injection molding, process monitoring, acoustic emission, PZT sensors, piezoelectric effect
Objavljeno: 22.06.2017; Ogledov: 155; Prenosov: 5
.pdf Celotno besedilo (854,94 KB)

A flexible microcontroller-based data acquisition device
Darko Hercog, Bojan Gergič, 2014, izvirni znanstveni članek

Opis: This paper presents a low-cost microcontroller-based data acquisition device. The key component of the presented solution is a configurable microcontroller-based device with an integrated USB transceiver and a 12-bit analogue-to-digital converter (ADC). The presented embedded DAQ device contains a preloaded program (firmware) that enables easy acquisition and generation of analogue and digital signals and data transfer between the device and the application running on a PC via USB bus. This device has been developed as a USB human interface device (HID). This USB class is natively supported by most of the operating systems and therefore any installation of additional USB drivers is unnecessary. The input/output peripheral of the presented device is not static but rather flexible, and could be easily configured to customised needs without changing the firmware. When using the developed configuration utility, a majority of chip pins can be configured as analogue input, digital input/output, PWM output or one of the SPI lines. In addition, LabVIEW drivers have been developed for this device. When using the developed drivers, data acquisition and signal processing algorithms as well as graphical user interface (GUI), can easily be developed using a well-known, industry proven, block oriented LabVIEW programming environment.
Ključne besede: data acquisition, DAQ, microcontroller, analogue-to-digital converter, ADC, USB, HID, LabVIEW, GUI, data logging
Objavljeno: 22.06.2017; Ogledov: 54; Prenosov: 4
.pdf Celotno besedilo (1,98 MB)

A comparison of frequency pullability in oscillators using a single AT-cut quartz crystal and those using two single AT-cut crystals connected in parallel with a series load capacitance or series load capacitance or series load inductance
Vojko Matko, 2006, izvirni znanstveni članek

Opis: This paper presents a comparison of frequency pullability in oscillators using asingle AT-cut crystal and those using two single AT-cut crystals connected in paralleloperated with a series load capacitance or series load inductance at fundamental frequenciesof 4, 10 and 19 MHz. Pullability describes how the operating frequency may be changed byvarying the load capacitance. The paper also gives impedance circuits for both single- anddual-crystal units. The experiment results show that the new approach using two singlequartz crystals connected in parallel increases the frequency pulling range by 30-200% pending on the type of oscillator. Also given is the crystal frequency stability at thesethree frequencies.
Ključne besede: quartz, AT cut, pulling range, two single-crystal unit oscillator
Objavljeno: 22.06.2017; Ogledov: 70; Prenosov: 6
.pdf Celotno besedilo (155,12 KB)

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