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Influence of small solar power plants on power quality
Sebastijan Seme, Jurček Voh, Jože Voršič, 2012, published scientific conference contribution

Abstract: The solar power plants are usually connected to the distribution network in node with transformer. Small, mini and micro solar power plants are connected as real dispersed production in the middle or at the end of line as consumers.This paper describes measurements, according to standard SIST EN 50160, at 274 m long line, fed at one side from 20/0,4 kV transformer and at the other side from small solar power plant and in between are 15 users (houses).
Keywords: dispersed production, small solar power plants, SIST EN 50160, measurements
Published: 01.06.2012; Views: 1835; Downloads: 0

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: 1467; Downloads: 79
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Analysis of noise sources produced by faulty small gear units
Aleš Belšak, Jurij Prezelj, 2007, original scientific article

Abstract: Noise source vizualization represents an important tool in the field of technical acoustics. There are many different techniques of noise source visualization. Most of them, however, are intended for a specific noise source in a specific type of acoustic environment. Consequently, a certain visualization method can be used only for certain types of noise sources in a specific acoustic environment and in a restricted frequency area. This paper presents a new visualization method of complex noise sources on the basis of the use of an acoustic camera. A new algorithm has been used, which makes it possible to visualize all types of different complex noise sources. Monopole, dipole or quadropole noise sources can be observed simultaneously. It is possible to track a moving noise source by means of an acoustic camera. In addition to that it is possible to observe various transient acoustical phenomena. Through the use in diagnostics, it is possible to define, by means of noise, the condition of mechanical systems at an advance level.
Keywords: gears, failure, noise sources, visualization of noise sources, sound, acoustic analysis, acoustic camera, signal analysis, acoustic image, measurements
Published: 31.05.2012; Views: 1242; Downloads: 30
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Improved method for shot particle velocity measurement within a shotblasting chamber
Aleš Hribernik, Gorazd Bombek, 2006, original scientific article

Abstract: This paper presents the application of two axially-spaced impact detecting sensors for correlation-based shot velocity measurement. The sensors were placed directly into the flow of shot particles for sensing the particles' impact. The implementation of cross-correlation for phase shift determination, however, was not an easy task. Several extensive improvements were necessary, before the original measurement system, already presented in this journal in December 2003, was capable of reliable velocity measurements. This paper presents the development of the system and optimisation of its components. The construction of a sensor built from a small microphone encapsulated in a metal housing and placed under a protective shield was optimised for a high ratio of frontal to side impact signal alteration. High vibration damping was also necessary. It was achieved by the combination of a well-weighted design for supporting elements and by a careful selection of used materials. These measures improved the similarity of the signals generated by the particlesć impact, significantly, and allowed the use of cross-correlation. The accuracy of the obtained results increased drastically by the application of cross-correlation, signal filtering was unnecessary and the signal processing was much faster.
Keywords: velocity measurements, shotblasting
Published: 30.05.2012; Views: 1425; Downloads: 86
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Non-destructive method for inward leakage detection of a plate evaporator
Aleš Hribernik, 2007, original scientific article

Abstract: A new non-destructive method was developed for the detection of refrigerant leakage at an evaporator`s inflow. Nitrogen and oxygen gas were successively blown through the evaporator. A gas analyser was applied at the outflow of the evaporator and the oxygen concentration measured. It was possible to detect any leakage by investigating the oxygen concentration-time history diagram.
Keywords: refrigeration, refrigerant leakage, plate evaporator, measurements, non-destructive method
Published: 31.05.2012; Views: 1210; Downloads: 67
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New approach to uncertainty evaluation in the calibration of gauge block comparators
Andrej Godina, Bojan Ačko, Marjan Družovec, 2007, original scientific article

Abstract: Gauge blocks (GBs) are being calibrated by two methods: interferometric calibration and calibration by mechanical comparison to reference GB. While interferometric method represents primary level, comparison is more suitable for calibrating industrial GBs because of lower costs and shorter calibration time. Although no significant changes in equipment happened in last decade, improvements in mechanical comparison are on-going. In addition to the uncertainty of the reference GB calibration, uncertainty of the GB comparator is the most important contribution to total uncertainty of the mechanical calibration. The article introduces a new approach for evaluating the uncertainty of GB comparator calibration. The uncertainty budget and results of analytical and experimental evaluation of all contributions are presented. This approach results in lower end-effect uncertainty and a slightly higher length dependent uncertainty, in comparison with the uncertainty evaluation procedure as described in EA document EA-10/02.
Keywords: measurements, calibration, measuring uncertainty, gauge block, comparator, CMC, mechanical comparison
Published: 31.05.2012; Views: 1680; Downloads: 91
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Modern deformation measurement techniques and their comparison
Boštjan Kovačič, Rok Kamnik, Miroslav Premrov, Nenad Gubeljak, Jožef Predan, Zdravko Tišma, 2008, review article

Abstract: Deformation measurement experiment has been undertaken where a concrete structure was subject to controlled loading. Concrete plate was loaded with hydraulic cylinder PZ 100 up to 42 kN. Nikon total station ser. 720 and camera Fuji Pro S3 have been used to make measurements at critical points during each additional load. A hydraulic computer operated cylinder was used for load increase. The use of total stations for deformation measurements is quite often, but the combination with digital photography is rather new and very suitable technique. It offers the capability of simultaneous monitoring of a large number of signalized or non-signalized points with very low root mean square error of 0.16 mm in geodetic method 0.7 mm in photogrammetry, respectively. The concrete plate was modeled and the comparison with the geodetic, photogrammetric and hydraulic method was made.
Keywords: deformation measurements, geodesy, digital photogrammetry
Published: 31.05.2012; Views: 1858; Downloads: 40
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Measurement uncertainty in calibration of measurement surface plates flatness
Andrej Gusel, Bojan Ačko, Vedran Mudronja, 2009, original scientific article

Abstract: Ravno merilno površino, kot je to na primer merilna plošča, lahko smatramo kot izhodišče za izvajanje večine meritev oblike in lege merjenih objektov. Da bi merilne plošče v ta namen zadovoljivo uporabljali, moramo najprej zagotoviti, da so res ravne in primerne za meritve. Ravnost merilne ploskve ugotavljamo posredno, tako da najprej določimo premost posameznih linij, ki so sestavni del merilne mreže. Te linije so še dodatno razdeljene na merilne korake, ki so prirejeni meram merilne opreme. Premost merilne linije izračunamo z merjenjem nagiba posameznega merilnega položaja za vsako linijo posebej, neravnost celotne površine pa tako, da rezultate po linijah povežemo v celoto. Osnove, postopki in merilne naprave za izvajanje meritev so torej znani, neznanka pa ostaja negotovost tovrstne kalibracije merilne površine. Meritev brez ustrezno izražene negotovosti ne pomeni ničesar, zato moramo zagotoviti, da bomo lahko negotovost določili. Pričujoči članek predstavlja nov pristop določanja merilne negotovosti pri merjenju ravnosti, ki temelji na uporabi metode Monte Carlo. Pri tem celoten merilni sistem razstavimo na posamezne komponente ter ocenimo njihovo veličino in vplive le teh, meritve pa simuliramo. Zanima nas tudi vpliv parametrov merilne mreže na meritev.
Keywords: production measurements, length measurements, measuring uncertainty, calibration, uncertainty measurement, flatness measurement
Published: 31.05.2012; Views: 1369; Downloads: 29
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Thread gauge calibration for industrial applications
Tadeja Primožič Merkač, Bojan Ačko, 2010, original scientific article

Abstract: There are two most commonly used methods for calibration of thread rings, with different measuring uncertainty. The method of mechanical sensing with two balls is mostly used on one-axial measuring machines and on coordinate measuring machines. However, the method of calculating the core diameter of the thread ring combined with the technique of adaptation (in accordance with the method of the smallest squares) is used on the profile scanner. The required tolerances, which are very narrow for adjustable and laboratory thread ring, so the measuring uncertainty may be too high when using the method of mechanical sensing with two balls, and the low quality of some control rings, are the decisive factors for choosing an appropriate method in the industry. This also depends on the laboratoryćs capability of executing a specific method. The measurements of the core diameter of thread rings, which are the main topic of this article, were included into an international inter-comparison in which the main subject was the same thread ring as the one mentioned in this article.
Keywords: thread ring gauge, calibration, pitch diameter, measurement uncertainty, dimensional measurements
Published: 31.05.2012; Views: 1438; Downloads: 23
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Volumetric properties of ethanol-water mixtures under high temperatures and pressures
Darja Pečar, Valter Doleček, 2005, original scientific article

Abstract: The densities of ethanol and ethanol-water mixtures were measured with a vibrating tube densimeter at 25.0, 50.0 and 75.0°C in the pressure range from 0.10 to 40.00 MPa. Densities were correlated using an empirical model. Partial molar volumes, excess molar volumes, isothermal compressibilities, cubic expansion coefficients and internal pressures were calculated from obtained densities. This study reports the dependence of densities, partial molar volumes, excess molar volumes, isothermal compressibilities, cubic expansion coefficients and internal pressures on composition, temperature and pressure.
Keywords: ethanol, ethanol-water mixtures, density measurements, vibrating U tube densimeter, partial molar volumes, isothermal compressibility, isobaric expansibility, cubic expansion coefficient, internal pressure
Published: 01.06.2012; Views: 1717; Downloads: 71
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