• Title/Summary/Keyword: Uncertainty of measurement

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Evaluation of Flow Measurement Uncertainty of Sonic Nozzle (소닉노즐의 유량측정 불확도 평가)

  • Choe, Hae-Man;Park, Gyeong-Am;Choe, Yong-Mun
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.25 no.12
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    • pp.1898-1904
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    • 2001
  • Measurement uncertainty should be evaluated according to ISO/IEC 17025. In Flow measurement area, uncertainty evaluation scheme was applied to the reference flow meter, sonic nozzle. Uncertainty was calculated by evaluating various uncertainty factors affected in flow measurement. The expanded uncertainty(U) of the sonic nozzle was 2.1$\times$ 10$^{-3}$ (confidence level of 95 %). This evaluation example will be useful in flow measurement uncertainty determination of other flow meters.

Measurement Uncertainty Assessment of Altitude Performance Test for a Turboshaft Engine (터보샤프트 엔진 고공성능시험의 측정 불확도 평가)

  • Yang, In-Young;Lee, Bo-Hwa
    • Journal of the Korean Society of Propulsion Engineers
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    • v.14 no.4
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    • pp.59-64
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    • 2010
  • Measurement uncertainty assessment was performed for altitude performance test for a turboshaft engine. Mathematical models of measurement were suggested for major performance parameters such as shaft horse power, fuel flow, specific fuel consumption, and airflow. The procedure was compared with the test of turbojet or turbofan engines. Uncertainty involved with the test condition measurement was assessed. Influence of the test condition measurement uncertainty on the corrected performance data was discussed. Uncertainty assessment result was provided for a example test case using a real altitude test facility. For major performance parameters, measurement uncertainties were assessed as 0.65~1.09% including the test condition measurement uncertainty, 0.36~0.94% not including it.

Cost-effective Investigation on Contaminated Land and Assessment of Measurement Uncertainty (오염토양의 효율적 조사기법과 측정불확도의 평가방법)

  • 이종천
    • Economic and Environmental Geology
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    • v.37 no.1
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    • pp.49-59
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    • 2004
  • The concectration and distribution of contaminants obtained from a contaminated land investigation or an environmental geochemistry survey constitutes the basis of a decision-making process on environmental policies or of scientific researches. As the quality of data determines the reliability of the result, the investigation plan should be adjusted according to the purpose of the investigation. In general, the effort to improve the data quality had been focused mainly on the QA/QC procedures in laboratories. The rapid progress of analytical instrument has also contributed toward improving the analytical precision to a sacrificable degree. Nevertheless, in many cases, it is not the analytical precision that needs improvement for the better precision of overall measurement process: it is rather during the sampling process in the field that is responsible for the poor precision. To assess the data quality on a measured value, ISO recommends to provide information on "measurement uncertainty" along with the measured value. The measurement uncertainty in an environmental measurement context can be explained as the statistical number that expresses the degree of the uncertainty stemming from the sampling and analytical procedures. There is a cost involved in order to improve the precision of sampling and analytical methods so as to decrease the degree of measurement uncertainty. The economical point of compromise in an investigation planning can be achieved when the allowable degree of uncertainty has been set before-hand. The investigation can then be planned accordingly not to exceed the uncertainty limit. Furthermore, if the measurement uncertainty estimated from the preliminary investigation can be separated into sampling and analytical uncertainties, it can be used as a criterion where the resources for the investigation should be allotted cost-effectively to reinforce the weakest link of the whole investigation process. This paper aims to present a method of estimating the level of measurement uncertainty of a measured contamination concentration at a site used as an example and to show how the estimated uncertainty can be applied to serve the particular purpose of an investigation.

Application of the uncertainty for insertion loss measurement of silencers (소음기 감음 성능 불확도 산출 방법 연구)

  • Yu, Seung-Guk;Kim, Dae-Hyeon;Kim, Yeong-Chan;Kim, Du-Hun
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2000.06a
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    • pp.1675-1680
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    • 2000
  • Recently the uncertainty has been made rapid progress in various fields of industry but the uncertainty measurement method of acoustical test (i.e. Insertion loss, Absorption ratio, Transmission loss etc,) hasn't been established. In this study, the uncertainty of measurement method for ducted silencers is carried out according to ISO 7235. The standard uncertainty factors are composed of sound pressure level, microphone sensitivity and pistonphone calibration in this measurement. Sound pressure level is type A evaluation of uncertainty, microphone sensitivity and pistonphone calibration are type B evaluation of uncertainty. The combined standard uncertainty is calculated by two type evaluation. The expanded uncertainty is expressed by the combined standard uncertainty multiply k value which is yield the effective degree of freedom.

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Measurement Uncertainty of Nicotine in Environmental Tobacco Smoke (ETS)

  • Lee, Jeong-Il;Lee, Cheol Min;Shim, In-Keun;Kim, Seong-Mi;Lee, Woo-Seok;Kim, Yoon-Shin
    • Bulletin of the Korean Chemical Society
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    • v.34 no.8
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    • pp.2394-2398
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    • 2013
  • Nicotine is the main component of environmental tobacco smoke, and its presence in indoor air is widely used as a secondhand-smoke indicator. Environmental tobacco smoke is a major source of indoor air pollution, but sufficient investigation of the uncertainty of its measurement, which mirrors the reliability of nicotine measurement, has not been performed. We calculated the uncertainty of measurement of indoor air nicotine concentration at low, medium, and high concentrations of 11.3798, 10.1977, $98.3768{\mu}g/m^3$, respectively, and we employed the Guide to the Expression of Uncertainty in Measurements (GUM), proposed by the International Organization for Standardization (ISO). The factors considered in determining the uncertainty were uncertainty of the calibration curve (calibration curve and repeated measurements), desorption efficiency, extraction volume, and sampling airflow (accuracy and acceptable limits of flowmeter). The measurement uncertainty was highest at low concentrations; the expanded measurement uncertainty is $0.9435{\mu}g/m^3$ and is represented as a relative uncertainty of 63.38%. At medium and high (concentrations, the relative uncertainty was 13.1% and 9.1%, respectively. The uncertainty of the calibration curve was largest for low indoor nicotine concentrations. To increase reliability of measurement in assessing the effect of secondhand smoke, measures such as increasing the sample injection rate ($1{\mu}L$ or more), increasing sampling volume to increase collected nicotine, and using gas chromatography-mass spectrometry (GC/MS) or GC/MS/MS, which has a lower quantitation threshold, rather than gas chromatography with nitrogen phosphorous detector, should be considered.

Uncertainty in the Course of Calibration of RF Multimeter using TVC (열전압변환기를 이용한 고주파전압계의 교정과 측정불확도)

  • 박정규;박석주;이환상;장경승;박명선
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.13 no.1
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    • pp.47-52
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    • 2002
  • It was virtually declared that measurement science must abandon the error analysis of measurement when ISO had published "Guide to Expression of uncertainty in Measurement" International inclination of measurement field in order to guarantee the traceability and confidence of measurement results discards the error concept and instead analyzes the measurement uncertainty. In this paper we establish a mathematical model of measurement and analyze all uncertainty factors as possible as for yielding the measurement uncertainty in the course of the calibration of RF multimeter using Transfer Standard, Thermal Voltage Converter We produce the expanded uncertainty by analyzing cable effects, correlation of thermocoupler and DC meter, DC source, RF source, attenuator, reflection coefficients and DUT.s and DUT.

Uncertainty assessment for a towed underwater stereo PIV system by uniform flow measurement

  • Han, Bum Woo;Seo, Jeonghwa;Lee, Seung Jae;Seol, Dong Myung;Rhee, Shin Hyung
    • International Journal of Naval Architecture and Ocean Engineering
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    • v.10 no.5
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    • pp.596-608
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    • 2018
  • The present study aims to assess test uncertainty assessment method of nominal wake field measurement by a Stereoscopic Particle Image Velocimetry (SPIV) system in a towing tank. The systematic uncertainty of the SPIV system was estimated from repeated uniform flow measurements. In the uniform flow measurement case, time interval between image frames and uniform flow speed were varied to examine the effects of particle displacement and flow around the SPIV system on the systematic standard uncertainty. The random standard uncertainty was assessed by repeating nominal wake field measurements and the estimated random standard uncertainty was compared with that of laser Doppler velocimetry. The test uncertainty assessment method was applied to nominal wake measurement tests of a very large crude oil carrier model ship. The nominal wake measurement results were compared with existing experimental database by other measurement methods, with its assessed uncertainty.

Uncertainty Analysis and Compensation of the Cell for Permittivity Measurement of Solid Materials (고체재료의 유전율 측정용 Cell의 불확도 분석과 보상)

  • Kim, Han-Jun;Yu, Kwang-Min;Kang, Jeon-Hong;Han, Sang-Ok
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.21 no.1
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    • pp.53-56
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    • 2008
  • The commercial parallel plate electrodes system with guard-ring electrode have been widely used for measurement of dielectric constants of solid materials. And the specification of the electrodes system is about 1 % of measurement uncertainty. This measurement uncertainty is only estimated the error come from mechanical measurements such as the area of the electrodes and the gap between the electrodes except the error come from the air gap between the electrodes and dielectric specimen. Because it is impossible to measure the air gap. This study analyze the total measurement uncertainties of the commercial dielectric constant test cell using 3 kinds of Standard Reference Materials. As a results, the total measurement uncertainty is much bigger than 1 % and the most of the uncertainty can be reduced by compensation of the error values evaluated in this study.

Comparison of measurement uncertainty calculation methods on example of indirect tensile strength measurement

  • Tutmez, Bulent
    • Geomechanics and Engineering
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    • v.12 no.6
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    • pp.871-882
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    • 2017
  • Indirect measure of the tensile strength of laboratory samples is an important topic in rock engineering. One of the most important tests, the Brazilian strength test is performed to obtain the tensile strength of rock, concrete and other quasi brittle materials. Because the measurements are provided indirectly and the inspected rock materials may have heterogeneous properties, uncertainty quantification is required for a reliable test evaluation. In addition to the conventional measurement evaluation uncertainty methods recommended by the Guide to the Expression of Uncertainty in Measurement (GUM), such as Taylor's and Monte Carlo Methods, a fuzzy set-based approach is also proposed and resulting uncertainties are discussed. The results showed that when a tensile strength measurement is measured by a laboratory test, its uncertainty can also be expressed by one of the methods presented.

An Experimental Study on the Performance of Heat Pump Unit Using Geothermal Heat for New Renewable Energy (신재생에너지 지열을 이용한 열펌프유닛의 성능에 관한 실험적 연구)

  • JEONG, SOON YOUNG
    • Journal of Hydrogen and New Energy
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    • v.31 no.6
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    • pp.630-636
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    • 2020
  • This paper presents a experimental study on the performance of the heat pump. Uncertainty of measurement means the degree of uncertainty in the measurement. Therefore, it estimates a section where expected value of the measurement might be within a certain confidence level and suggests a range where measured representative value might be incorrect. Uncertainty of measurement is a parameter that shows characteristics of dispersion of measured value that was reasonably estimated from measured quantity. Measurement result of performance experiment is not a true value but estimated value that was estimated reasonably. Therefore, uncertainty of measurement needs to be calculated and presented with the result of measurement.