1. Uncertainty of nitrate and sulphate measured by ion chromatography in wastewater samplesBrigita Tepuš, Marjana Simonič, 2007, original scientific article Abstract: This paper presents an evaluation of measurement uncertainty regarding the results of anion (nitrate and sulphate) concentrations in wastewater. Anions were determined by ion chromatography (EN ISO 10304-2, 1996). The major sources of uncertainty regarding the measurement results were identified as contributions to linear least-square or weighted regression lines, precision, trueness, storage conditions, and sampling. Determination of anions in wastewater is very important for the purification procedure, especially the amount of nitrate in waste and potable waters. The determined expanded uncertainty was 6% for nitrate anions and 8.3% for sulphate anions. The difference between measurement uncertainties determined by the two methods, the weighted and linear least-square methods is negligible.
Keywords: wastewater, nitrates, sulphates, measurements, measuring uncertainty
Published in DKUM: 01.06.2012; Views: 1902; Downloads: 357
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2. Calibration of electronic levels using a special sine barBojan Ačko, 2005, original scientific article Abstract: Electronic levels are designated for the precise measurement of inclination angles within the range of +- 3 mm/m. They are very often used for checking the straightness of machine tool guides as well as the flatness of different kindsof machine tool tables and surface plates. Typical resolution of such instruments is 1 m/m. Electronic levels are calibrated by using very precise angle generators. One such generator is a sine bar. Sine bars are cheap and enable fast and simple calibrations. Commercial sine bars however are not precise enough. We, therefore, decided to design a special sine bar, which would be able to generate angles within an uncertainty of 1 mžm. This sine barwas designed by the laboratory staff and manufactured in our workroom. We have also created a calibration procedure, which has already been accredited. Uncertainty analysis, including experimental measurements, shows that the planned uncertainty has been reached. The sine bar design, calibration procedure and uncertainty evaluation are presented in this article.
Keywords: production measurements, measuring uncertainty, calibration, inclination angles, flatness measurements, sine bar, electronic level
Published in DKUM: 01.06.2012; Views: 3099; Downloads: 117
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3. Measurement uncertainty in calibration of measurement surface plates flatnessAndrej 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 in DKUM: 31.05.2012; Views: 2317; Downloads: 41
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4. New approach to uncertainty evaluation in the calibration of gauge block comparatorsAndrej 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 in DKUM: 31.05.2012; Views: 2399; Downloads: 120
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