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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: 284; Prenosov: 245
.pdf Celotno besedilo (4,21 MB)
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4.
Power line magnetic field deviations for three different definitions of current unbalance
Danka Antic, Anamarija Juhas, Miodrag Milutinov, 2019, strokovni članek

Opis: An estimation procedure of the public's exposure to the low-frequency magnetic field generated by overhead power lines, according to the international standards, implies measurement and an extrapolation. It is necessary to measure both the magnetic field around the lines and the current in the lines simultaneously. The extrapolation procedure implies the calculation of the maximum magnetic field that will occur when the line current achieves its maximum. The calculation relies on a proportion between the current in the power line and the magnetic field around the power line, which is valid only when the currents are balanced. Unfortunately, the standards do not cover the unbalanced cases. The relation between the current unbalance and magnetic field could improve the estimation procedure. In the literature, several different definitions of the current unbalance could be found. In this paper, a comparison of three different definitions of current unbalance and their relation to the deviation of a magnetic field are considered. The magnetic field is calculated in the vicinity of the bus bar. The same procedure could also be applied around overhead power lines. The definitions for the current unbalance used in this paper are derived from the existing definitions of the voltage unbalance. Only one of these three definitions considers phase unbalance. The relationships between current unbalance and the maximum deviation of the magnetic field are found to be proportional.
Ključne besede: magnetic field, power delivery, measurement, public exposure assessment
Objavljeno v DKUM: 22.12.2023; Ogledov: 442; Prenosov: 3
.pdf Celotno besedilo (1,86 MB)
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5.
Measurement System for Testing of Electric Drives in Electric Vehicles
Iztok Brinovar, Gregor Srpčič, Sebastijan Seme, Bojan Štumberger, Miralem Hadžiselimović, 2019, objavljeni znanstveni prispevek na konferenci

Opis: This paper deals with the implementation of a measurement system, capable of performing real-time data acquisition and control, and allows the performance analysis of electric drives used for electric vehicle propulsion. For applying the mechanical load on the shaft of the tested motor three different test bench configurations with different power and speed ranges can be used. The main objective of the measurement system is to perform routine performance tests and road simulation tests (in terms of driving cycles) of an electric drive. It provides a research environment for analysis, investigation and study of electric drives and control strategies.
Ključne besede: measurement system, test bench, electric machines, electric vehicles, permanent magnet synchronous motor
Objavljeno v DKUM: 04.12.2023; Ogledov: 300; Prenosov: 15
.pdf Celotno besedilo (18,06 MB)
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6.
Method for Determining Battery Health
Slavko Brečko, Dalibor Igrec, Aleš Breznik, Amor Chowdhury, Miran Rodič, 2019, objavljeni znanstveni prispevek na konferenci

Opis: This paper presents a method for automatic state of health estimation for lithium ion batteries. A pulse method for determining battery characteristics using a specially developed electronic measuring device is presented. Measurement results show characteristics of several measured batteries exhibiting different states of health with estimation possible even with a protection circuit present on the battery.
Ključne besede: Li-ion, state of health, battery testing, measurement circuit, estimation method
Objavljeno v DKUM: 04.12.2023; Ogledov: 276; Prenosov: 12
.pdf Celotno besedilo (18,06 MB)
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7.
Measurement device for testing printed circuit board assemblies coming off the production line
Nejc Friškovec, Manja Obreza, Sebastijan Seme, Klemen Sredenšek, 2022, izvirni znanstveni članek

Opis: The paper presents an efficient way to evaluate and determine the quality of an assembled printed circuit board coming off the production line. A printed circuit board assembly consists of electronic devices soldered to the printed circuit board, which provides the electrical connections. After assembling the printed circuit board, a function test needs to be performed to guarantee the quality of the product. Usually, the assembly lines are equipped with cameras that detect inaccuracies such as missing components. This level of quality assurance is sometimes not enough, and we need to add another degree of precaution. In addition to camera inspections, electronic measurements must be conducted. The process needs to be automated to provide repeatability and speed. The paper evaluates such a device and presents its advantages, disadvantages, and complexity. The device includes an electrical part that performs the measurements, a mechanical part that consists of a housing and a mounting nest, and a program that supervises the process.
Ključne besede: electrical measurement, printed circuit board, testing device, automation, intelligent measuring system
Objavljeno v DKUM: 30.10.2023; Ogledov: 289; Prenosov: 5
.pdf Celotno besedilo (2,26 MB)
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8.
Miniature magneto-optic angular position sensor
Vedran Budinski, Simon Pevec, Stanislav Čampelj, Alenka Mertelj, Darja Lisjak, Denis Đonlagić, 2022, izvirni znanstveni članek

Opis: This Letter describes a miniature Fabry–Perot, contactless, magneto-optic sensor for angular position measurement. The sensor utilizes a magneto-optic fluid comprising barium hexaferrite nanoplatelets that become birefringent in the presence of an external magnetic field and a compact fiber-optic sensor system for tracking the liquid’s optical axis direction. An efficient temperature compensation system is provided which allows the use of otherwise highly temperature-sensitive magneto-optic liquids. An unambiguous measurement range of 90° and a resolution of better than 0.05° are demonstrated experimentally.
Ključne besede: Fiber optic sensor, magneto-optic sensor, angular position measurement
Objavljeno v DKUM: 12.05.2023; Ogledov: 528; Prenosov: 63
.pdf Celotno besedilo (3,76 MB)
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9.
A geostress measurement method based on an integrated drilling and optical microscopic imaging system
Jinchao Wang, Chunying Wang, Zengqiang Han, Yiteng Wang, Xinjian Tang, 2018, izvirni znanstveni članek

Opis: Conventional geostress measurement methods are limited by deficiencies including the measurable depth, the complexity, and the long duration of operation. To address these problems and achieve the measurement of geostress in deep wells under conditions of complex high pressures and high temperatures, we propose a new measurement method for geostress based on an integrated drilling and optical microscopy system. Its innovative integrated structure eliminates the problems associated with complex procedures and depth limits, and avoids rock creep caused by long delays, significantly improving the accuracy and range of the measurements. It works by using microscopic imaging and direct contact probes to capture the changes of a borehole’s cross-sectional outlines before and after stress relief. The resulting images are analyzed with search circles to obtain the positions of probe apices, which can be fitted into ellipses that describe the outlines, and calculate the state of the stress. The validity and accuracy of the method was verified by in-door tests and field applications in the ZK1 borehole. The results show that: (1) the integrated system can be used to measure micrometer-grade deformations; (2) the searchcircle approach can accurately obtain the positions of probe apices; and (3) the stress measurement method based on the system is accurate and feasible.
Ključne besede: geostress, probe, optical microscopy, measurement while drilling, search circle
Objavljeno v DKUM: 11.10.2018; Ogledov: 1516; Prenosov: 568
.pdf Celotno besedilo (1,26 MB)
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10.
3D response of an excavation adjacent to buildings supported by inclined struts
Zahra Sabzi, Ali Fakher, 2017, izvirni znanstveni članek

Opis: The presented study focuses on field observations and a 3D numerical analysis of open-cut excavations adjacent to a building supported by inclined struts. The performance of the struts in carrying the building loads and decreasing the deflections is investigated. Struts reduce the amount of deformations and also create a corner effect similar to the diaphragm walls corner. The influence of the distance between the struts is studied and the optimum struts interval is proposed. The most effective configuration of struts installation in reducing the deflections and building damage is proposed. A displacement-based design guideline is also presented based on the results of numerical studies.
Ključne besede: measurement, 3D finite-element analysis, displacement-based design
Objavljeno v DKUM: 18.06.2018; Ogledov: 1113; Prenosov: 178
.pdf Celotno besedilo (2,85 MB)
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