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1.
Measurements of Small Frequency Differences by Dual Mode 4 MHz Quartz Sensors
Vojko Matko, 2023, izvirni znanstveni članek

Opis: We proposed a method for measuring frequency differences of the order of a few Hz with an experimental error lower than 0.0001% by using two 4 MHz quartz oscillators, the frequencies of which are very close (a few 10 Hz difference) due to the dual mode operation (differential mode with two temperature-compensated signal frequencies or a mode with one signal and one reference frequency). We compared the existing methods for measuring frequency differences with the new method which is based on counting the number of transitions through zero within one beat period of the signal. The measuring procedure requires equal experimental conditions (temperature, pressure, humidity, parasitic impedances etc.) for both quartz oscillators. To ensure equal resonant conditions for oscillation two quartz crystals are needed, which form a temperature pair. The frequencies and resonant conditions of both oscillators must be almost equal, which is achieved by an external inductance or capacitance. In such a way, we minimized all the external effects and ensured highly stable oscillations and high sensitivity of the differential sensors. The counter detects one beat period by an external gate signal former. By using the method of counting transitions through zero within one beat period, we reduced the measuring error by three orders of magnitude, compared to the existing methods.
Ključne besede: small frequency difference measurement, temperature-compensated quartz sensors, differential sensors, quartz oscillators, transitions-through-zero method
Objavljeno v DKUM: 26.03.2024; Ogledov: 74; Prenosov: 2
.pdf Celotno besedilo (4,21 MB)
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2.
The development of an electropolymerized, molecularly imprinted polymer (MIP) sensor for insulin determination using single-drop analysis
Tanja Zidarič, David Majer, Tina Maver, Matjaž Finšgar, Uroš Maver, 2023, izvirni znanstveni članek

Opis: An electrochemical sensor for the detection of insulin in a single drop (50 μL) was developed based on the concept of molecularly imprinted polymers (MIP). The synthetic MIP receptors were assembled on a screen-printed carbon electrode (SPCE) by the electropolymerization of pyrrole (Py) in the presence of insulin (the protein template) using cyclic voltammetry. After electropolymerization, insulin was removed from the formed polypyrrole (Ppy) matrix to create imprinting cavities for the subsequent analysis of the insulin analyte in test samples. The surface characterization, before and after each electrosynthesis step of the MIP sensors, was performed using atomic force microscopy, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The performance of the developed MIP–SPCE sensor was evaluated using a single drop of solution containing K3Fe(CN)6 and the square-wave voltammetry technique. The MIP–SPCE showed a linear concentration range of 20.0–70.0 pM (R2 = 0.9991), a limit of detection of 1.9 pM, and a limit of quantification of 6.2 pM. The rapid response time to the protein target and the portability of the developed sensor, which is considered a disposable MIP-based system, make this MIP–SPCE sensor a promising candidate for point-of-care applications. In addition, the MIP–SPCE sensor was successfully used to detect insulin in a pharmaceutical sample. The sensor was deemed to be accurate (the average recovery was 108.46%) and precise (the relative standard deviation was 7.23%).
Ključne besede: electrochemical sensors, electropolymerisation, electron microscopy
Objavljeno v DKUM: 14.03.2024; Ogledov: 139; Prenosov: 7
.pdf Celotno besedilo (2,91 MB)
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3.
High-Order Fiber Bragg Grating Corrosion Sensor Based on the Detection of a Local Surface Expansion
Vedran Budinski, Matej Njegovec, Simon Pevec, Boris Macuh, Denis Đonlagić, 2023, izvirni znanstveni članek

Opis: This paper presents a fiber optic sensor for the detection of corrosion processes that occur on metal surfaces. In the proposed sensor design, a sensing fiber with an inscribed high-order Bragg grating is attached to the observed metal surface. A broadening of high-order Bragg grating spectral characteristics is observed and used to detect small and highly localized longitudinal strain variations that occur along the fiber as a result of corrosive rust flakes' formations beneath the sensing fiber. The proposed approach provides a straightforward fabrication method, the possibility for unobtrusive mounting, including mounting of the sensor beneath the corrosion-protective layers, and consistent corrosion detection yields.
Ključne besede: optical fiber sensors, corrosion, impact of corrosion, optic sensors
Objavljeno v DKUM: 09.02.2024; Ogledov: 151; Prenosov: 8
.pdf Celotno besedilo (1,58 MB)
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4.
An All-Fiber Fabry–Pérot Sensor for Emulsion Concentration Measurements
Simon Pevec, Janez Kunaver, Vedran Budinski, Matej Njegovec, Denis Đonlagić, 2023, izvirni znanstveni članek

Opis: This paper describes a Fabry-Perot sensor-based measuring system for measuring fluid composition in demanding industrial applications. The design of the sensor is based on a two-parametric sensor, which enables the simultaneous measurement of temperature and refractive index (RI). The system was tested under real industrial conditions, and enables temperature-compensated online measurement of emulsion concentration with a high resolution of 0.03 Brix. The measuring system was equipped with filtering of the emulsion and automatic cleaning of the sensor, which proved to be essential for successful implementation of a fiber optic RI sensor in machining emulsion monitoring applications.
Ključne besede: optical fiber sensors, Fabry–Pérot interferometer, refractive index, temperature, emulsion concentration
Objavljeno v DKUM: 06.02.2024; Ogledov: 132; Prenosov: 7
.pdf Celotno besedilo (4,44 MB)
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5.
Accuracy of Rotational Speed and Torque Sensors for Determining the Mechanical Power of Rotating Electrical Machines
Gregor Srpčič, Iztok Brinovar, Bojan Štumberger, Sebastijan Seme, Miralem Hadžiselimović, 2019, objavljeni znanstveni prispevek na konferenci

Opis: This paper deals with determining the accuracy of measuring systems for determining the characteristics of rotating electrical machines. Efficiency classes and experimental methods for determining efficiency, are given in a standard, which has to be strictly respected. For determining the efficiency of an electrical machine, it is necessary to have a modern and accurate measurement system with sensors of high accuracy classes, which enables the user to carry out precise measurements and consequently, to determine all the characteristics of the electrical machine. This paper will be focused on torque and speed measurements.
Ključne besede: efficiency, measuring system, electric machines, torque and rotational sensors, accuracy
Objavljeno v DKUM: 04.12.2023; Ogledov: 286; Prenosov: 12
.pdf Celotno besedilo (18,06 MB)
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6.
The use of a novel smartphone testing platform for the development of colorimetric sensor receptors for food spoilage
Tinkara Mastnak, Gerhard J. Mohr, Matjaž Finšgar, 2023, izvirni znanstveni članek

Opis: This work presents a novel smartphone testing platform for the validation of colorimetric sensor receptors (CSRs) in the form of layers that enables reliable and straightforward determination of their color change in a closed system using a commercially available color sensor. The food-compatible model CSR used for the method development was made of black carrot extract and ethyl cellulose. The colorimetric responses were studied in detail for NH3, dimethylamine (DMA), and trimethylamine (TMA) by analyzing changes in the value of the total color difference (ΔE) with the increasing logarithm of the mass concentration (log γ) of the analytes. The method was partially validated for the detection limit (LOD), the limit of quantification, sensitivity, and linear γ range. The fastest reaction times were obtained for the NH3 analyte, while the calculated LOD values were quite similar (1.48 mg L−1 for NH3, 1.55 mg L−1 for DMA, and 1.58 mg L−1 for TMA). The applicability of CSRs was shown for different types of muscle food. Frozen (boneless and skinless) hake fillets were used for additional experimental work in which the color changes of the CSRs were correlated with the values of the total volatile basic nitrogen (TVB-N) and the total counts of aerobic and anaerobic microorganisms. The developed testing platform shows great promise for the development of CSRs that define the quality of a broad variety of muscle food.
Ključne besede: sensors receptors, CSRs, colorimetric
Objavljeno v DKUM: 01.08.2023; Ogledov: 570; Prenosov: 20
.pdf Celotno besedilo (1,64 MB)
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7.
8.
Signal processor for optical fiber sensors based on MEMS Fabry-Perot interferometer : master's thesis
Nikola Uremović, 2020, magistrsko delo

Opis: In the master thesis, we have created an interrogation system for measuring the change of the optical path in the Fabry-Perot interferometer caused by the strain of the surface at which it was attached to. The change of strain can be calculated via a change in optical path length which is visible as a shift in phase angle. The system will be used as a system for measuring strain, although it can be used for measuring various physical parameters that can cause a change in optical path length, such as pressure, force, temperature, etc. Initially, the theoretical background of the system and project components are represented and explained, following the building process of the electronic and optical part of the project. Lastly, the working principle and programming algorithms of a system are presented and explained. Measurement results are shown at the end, as well as the conclusion that is drawn from the thesis.
Ključne besede: optical fibers, sensors, interferometer, signal processing
Objavljeno v DKUM: 04.11.2020; Ogledov: 1025; Prenosov: 107
.pdf Celotno besedilo (5,11 MB)

9.
Upgrading the Management of Electronic Systems in a Passenger Car : magistrsko delo
Josip Sučec, 2019, magistrsko delo

Opis: The master's thesis introduces the process of modernizing an older model of a passenger car. The mechanical, electrical and programming solutions were required to upgrade the existing car. Upgrades have been made to improve safety, comfort and performance. The safety upgrades contain the development and implementation of the brake temperature and the tire pressure monitoring system, respectively. The comfort upgrades include the car’s light system and accessory improvements, such as “follow me home” function and automatic window closing. The performance upgrades include installation of racing coilovers and the development of remote damping ratio adjustment system. For the central logic unit, a vehicle specific Android device was installed. It controls the local electronic control units made for each specific task and displays tire pressures and brake temperatures. The Android device communicates with the electromechanical car systems by using several serial buses. The communication protocols and their messages in the original car had to be reverse engineered to establish proper communication among the systems in the upgraded car.
Ključne besede: passenger car, serial buses, reverse engineering, adjustable suspension, sensors
Objavljeno v DKUM: 02.08.2019; Ogledov: 1052; Prenosov: 135
.pdf Celotno besedilo (6,95 MB)

10.
Challenges of on-line condition monitoring of hydraulic oils
Vito Tič, Darko Lovrec, objavljeni znanstveni prispevek na konferenci

Opis: Ensuring adequate quality of hydraulic oil and planning its change is crucial for a stable and smooth operation of many industrial machines. The best reliability can certainly be provided by using continuous monitoring of hydraulic oils, which is usually carried out remotely by means of modern online sensors. Nevertheless, the development and implementation of such a system represents a unique challenge, since the measurement of the oil condition is much more complicated than measuring usual operating parameters, such as pressure or temperature.
Ključne besede: hydraulic oil, quality, on-line monitoring, oil change, modern sensors
Objavljeno v DKUM: 10.10.2017; Ogledov: 999; Prenosov: 417
.pdf Celotno besedilo (370,30 KB)

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