Uncertainty Of Measurement Result Research Articles

A tentative discussion on measurement uncertainty of electrical measuring instruments and device

This paper gives an elaboration on the source of uncertainty, general class and its difference with error, followed by detailed analysis and verification of a real case of measurement uncertainty. Taking a multi-function three-phase electrical measuring instrument calibration device as an example, the paper describes how to evaluate the uncertainty in measurement result of indication errors in mathematical model.

Uncertainty Propagation and Assessment of Five-Axis On-Machine Measurement Error

Abstract As an important technology of adaptive machining, on-machine measurement (OMM) is always used to measure the shape of the to-be-cut surface. Due to the multi-source errors in an OMM system, the confidence of the measurement accuracy becomes particularly important before planning the next cutting procedure. OMM is implemented by multi-components involving machine tools, fixture, and on-machine probe. Each component introduces uncertainty of error into the measurement result. The positioning error, alignment error, and eccentricity error are investigated in terms of the expectation, uncertainty, and probability density function. By the kinematics of the components participated in the measurement, these errors are accumulated to affect the measurement results. Thus, the uncertainty of the final measurement result is determined by the accumulation of uncertainty of error sources. In order to evaluate the uncertainty of measurement error, an uncertainty propagation model involving positioning error of five-axis machine tools, alignment error of workpiece, and eccentricity error of the stylus tip is established in terms of the kinematic chain of OMM. Then, the uncertainty of the measurement result in vector form is obtained. Finally, the simulation and the experiment about the impeller are employed to validate the effectiveness and repeatability of the uncertainty propagation model for five-axis OMM.

Development of a methodical approach for uncertainty quantification and meta-modeling of surface hardness in white layers of longitudinal turned AISI4140 surfaces

Abstract The formation of thermally and mechanically induced near-surface microstructures in the form of white layers leads to different hardness properties in these areas. Therefore, this paper conducts systematic surface hardness measurements and uncertainty quantification utilizing the Monte Carlo Method (MCM) in accordance with the Guide to the Expression of Uncertainty in Measurement (GUM). Furthermore, several meta-models describing the hardness course in relationship to the material depth are used to model this nonlinear relationship via machine learning. The evaluation and selection of the optimal model considers the trade-off between measurement uncertainty and prediction quality in terms of mean squared error (MSE). The resulting measurement uncertainty is to be used for the calibration of a non-destructive micromagnetic material sensor. This will then be implemented for in-process monitoring in the outer diameter longitudinal turning process. This should make it possible to detect white layers during machining and to avoid them accordingly by controlling the machine parameters. By means of a soft sensor, the corresponding target value is to be derived from the micromagnetic material sensor measurement.

A case study on electromagnetic field assessment and uncertainty evaluation

This paper presents a radiofrequency electromagnetic field exposure assessment carried out in an observatory open for general public, where there are multiple radio and television transmitters in the surrounding area. An uncertainty evaluation is presented, considering that the main broadcast stations reduced their transmitted power to comply with the regulatory limits throughout the observatory area. A discussion is done about uncertainty of measurement result and its use or not in both precautionary measure and sanctioning process applied by regulatory authority.

Toward a New Primary Standardization of Radionuclide Massic Activity Using Microcalorimetry and Quantitative Milligram-Scale Samples.

We present a new paradigm for the primary standardization of radionuclide activity per mass of solution (Bq/g). Two key enabling capabilities are 4π decay-energy spectrometry using chip-scale sub-Kelvin microcalorimeters and direct realization of mass by gravimetric inkjet dispensing using an electrostatic force balance. In contrast to traditional traceability, which typically relies on chemical separation of single-radionuclide samples, 4π integral counting, and additional spectrometry methods to verify purity, the system described here has both 4π counting efficiency and spectroscopic resolution sufficient to identify multiple radionuclides in the same sample at once. This enables primary standardization of activity concentrations of mixed-radionuclide samples. A major benefit of this capability, beyond metrology, is in assay of environmental and forensics samples, for which the quantification of multiplenuclide samples can be achieved where presently inhibited by interferences. This can be achieved without the need for chemical separations or efficiency tracers, thereby vastly reducing time, radioactive waste, and resulting measurement uncertainty.

The Expanded Lever Rule on the Phase Transformation Rate Curve for Phase Volume Fraction Calculation in Thermal Simulations

The expanded lever rule is more efficient for calculating phase volume fraction when two phases are partly overlapped. It can make up the deficiency of metallography analysis when phases are similar in morphology. In this study, the expanded lever rule on the phase transformation rate curve is introduced, the approximate symmetry principle in applying the expanded lever rule is modified, and the resulting measurement uncertainty is discussed. Results show that (i) the calculated volume fraction of pearlite by the expanded lever rule in an overlapped two-phase process of a high strength low alloy (HSLA) weld metal is in accordance with the result by metallography analysis, and (ii) the expanded lever rule has an advantage over metallography analysis as it can calculate upper bainite, lower bainite, and lath-like martensite volume fractions in a three-phase process with two overlaps of a HSLA steel. The expanded lever rule is applicable to overlapped two-phase processes of any material theoretically since each phase process can be described by Johnson–Mehl–Avrami–Kolmogorov equation.

A new implementation of EN1839 method T mixture preparation to prepare calibration gas mixtures for anesthetic gas monitors.

In this study different mixtures from anesthetic liquids vapours in air and O2-sevoflurane/air, sevoflurane/O2 and isoflurane/O2-were prepared according to EN1839 method T. The gases mixtures were used to calibrate anesthetic gas monitors. The targeted concentrations (TCs) from sevoflurane and isoflurane in air and O2 were 0 vol%, 0.15 vol%, 0.7 vol%, 1 vol%, 1.5 vol%, 2.5 vol%, 5 vol%, 6 vol% and 8 vol%. The values of liquids, air and O2 flow rates which are corresponding theoretically to the TCs were calculated. The results showed that the measured concentrations by anesthetic gas monitor are in good agreement with TCs. Full validation was performed to assure the suitability of the method for preparing gas mixtures to calibrate anesthetic gas monitors. Linearity, limit of detection (LOD), limit of quantification (LOQ), precision, method robustness and uncertainty of measurement results were evaluated in the validation study. The results indicated that the method is valid for the purpose of analysis.

Investigating the Additional Components of Uncertainty of Measurment Result of Unsteady Flow

The additional components of uncertainty of measurement result of unsteady flow by means of pressure differential flowmeter are investigated in the article. In particular, the authors considered in detail the technique for estimating the additional component of uncertainty, caused by the nonlinearity of the flowrate dependence on the pressure drop on the standard primary device, as well as the additional component, which is related to the absence of the inertial term in the root expression of the quasi-steady flow equation. On the example of four differential pressure signals that reproduce the pulsating and unsteady flow modes of the fluid, the estimating the named components is carried out and the dependence of these components of uncertainty on the basic characteristics of the differential pressure signal (root mean square amplitude of pulsations and the maximum relative deviation) is demonstrated. It is shown that the increase of these signal characteristics leads to an increase in the corresponding components of the uncertainty and, consequently, in the resulting additional uncertainty of the measured value of flowrate. Particularly, for the investigated pressure drop signals for which the root mean square amplitude does not exceed 20% of the mean pressure drop, the resulting additional uncertainty of the measured flowrate reaches 0.5%. Since the additional uncertainty caused by unsteady flow is systematic and has a positive sign, it is possible to determine the correction coefficient based on this additional uncertainty and to correct the measured value of the flowrate by considering the correction factor in the flow equation. However, the authors propose to correct the measured value of the flowrate only if it is impossible to identify the causes of unsteady flow and to eliminate their impact on the flowrate.

Analytic solutions for calculating the surface inclination of isotropic media and bare substrates by using reflection-based generalized ellipsometry

Using ellipsometry for curved-surface characterization requires the knowledge of the surface normal vector in order to determine material-related surface parameters like refractive index, layer thickness, or birefringence of the surface material at the incidence point, because the recorded signal depends on both the (unknown) surface normal vector n→ and material-related surface characteristics. It is convenient in ellipsometry to parametrize the surface normal vector by the angle of incidence θ and the azimuthal rotation angle ϕ. Depending on the design of the ellipsometer, there may be two angles, ϕ1 and ϕ2, necessary, which describe the azimuthal rotation before and after the light is reflected off the sample, respectively. The authors present analytic formulas to determine ϕ1 and ϕ2 for optically isotropic samples using generalized ellipsometry. The resulting measurement uncertainty is lower than that of previously known methods. Furthermore, the authors provide an analytic formula to calculate θ from the ellipsometric angles Ψ and Δ for bare substrates with known refractive index N1=n1−ik1. The formulas have been evaluated with experimental data acquired with a conventional and an imaging retroreflection-based return-path ellipsometer.

Particle image velocimetry in refractive index fields of combustion flows

Optical measurements inside reacting flows are often disturbed by refractive index fields, e.g., due to the strong density gradients in flames. Although occurring measurement errors due to light refraction are a known problem for certain particle image velocimetry (PIV) applications, only a qualitative analysis of the resulting measurement uncertainty inside flame flows has been carried out to date. As an important step forward, a measurement approach is proposed, which enables a quantification of the resulting measurement uncertainties due to light refraction. As an example, the measurement approach is applied to a premixed propane flame. The uncertainty analysis is based on the determination of occurring particle position errors due to light refraction inside the flame. For three different measurement planes, the velocity field is measured with PIV and the particle position errors are experimentally measured and verified by ray-tracing simulation based on the measured refractive index field, which is determined by the background-oriented Schlieren method. In the examined flow, maximal position errors amount up to 14 μm and yield significant systematic velocity errors of up to 4% and random velocity errors of up to 6%. In contrast to the systematic velocity error, the random velocity error varies significantly for the analyzed measurement planes inside the flame flow.Graphic abstract

STATE PRIMARY REFERENCE PROCEDURE FOR THE MEASUREMENT OF ASH MASS FRACTION IN FOOD, FOODSTUFF AND ALIMENTARY RAW MATERIALS

The lack of traceability of the results of ash content measurements to the state standards of measurement units is considered. The problems of ash mass fraction measurement in food industry are revealed: dependence of the measurement results on conditions of the analysis, incomplete information on the modes of measurements and metrological characteristics in standardized methods, the absence of reference materials. We present information about the measurement method and equipment for implementation of the State primary reference procedure (SPRP) for measuring the ash mass fraction in food and foodstuff (grain, grain products, starch, sugar, dairy products, low-lactose products, lactose-free products, compound feeds and feed components) and describe the procedure of determining the methodological parameters (temperature, duration of combustion, weight of sample) in the course of the SPRP development using a stereoscopic pancratic microscope and thermogravimetric analyzer with mass spectrometric detector (implementing TGA-MS methods) included in the State primary measurement standard of mass fraction and mass (molar) concentration of water in liquid and firm substances and materials GET 173 – 2017. The described algorithm for estimating the uncertainty of the ash mass fraction measurements using multifactor experiment, regression analysis and single-factor ANOVA provide information about the sources of the uncertainty and their contributions to the total uncertainty of measurement results. The metrological characteristics, scope and purpose of SPRP are presented. The results of interlaboratory comparisons confirming the equivalence of the developed SPRP to similar measurement procedures (methods) of foreign countries are presented. The applicability of the developed SPRP for determination of the certified values of the mass fraction of crude ash to testing reference standards of compound feed composition is demonstrated.

3D push-pull heterodyne interferometer for SPM metrology.

A three-coordinate heterodyne laser interferometer has been developed to measure the displacement of the probe microscope scanner with a subnanometer resolution that provides traceability of measurements to the standard of meter through the wavelength of a stabilized He-Ne laser. Main sources of errors are investigated, and their influence is minimized so that the resulting measurement uncertainty of the system does not exceed 0.2nm, and the resolution is 0.01nm. The investigation of metrological characteristics of the three-coordinate interferometer was carried out with a scanning probe microscopy (SPM) NanoScan-3D using TGZ-type calibration gratings. The values measured with SPM fell within the 95% confidence interval given by Physikalisch-Technische Bundesanstalt (PTB) (Germany). SPM equipped with a laser interferometer was used to measure the characteristics of dynamic etalons of geometric dimensions.

The Combined Relative Uncertainty of Measurement Results by Prototype Semi-Automated Calorimetric Chamber

Abstract The paper presents an evaluation of the combined relative uncertainty of the result of direct step temperature measurements aimed at evaluation of the indirect measurements of the specific thermal capacity of the heat insulating concrete by means of a pair of resistive cable thermometers fitted with Pt100 temperature sensors and integrated into a computer-controlled calorimetric chamber. In particular, it is a proposal of evaluation of the overall relative uncertainty of the measurement of partial temperatures measured in equidistant time steps, in a relatively wider time interval. In practice, the uncertainty of the result of step temperature measurements is most often declared only by the instrument uncertainty specified by the manufacturer. The exact evaluation of the result of the measurements of thermal and temperature material parameters measured by the calorimetric comparison method is required by the fact that the investigated samples are made of newly designed non-tabulated building materials and that the measurements are made by a prototype device.

Experimental design and measurement uncertainty in ligand binding studies by affinity capillary electrophoresis.

In all life sciences ligand binding assays (LBAs) play a crucial role. Unfortunately these are very error prone. One part of this uncertainty results from the unavoidable random measurement uncertainty, another part can be attributed to the experimental design. To investigate the latter, uncertainty propagation was evaluated as a function of the given experimental design. A design space including the normalized maximum response range (nMRR), the data point position (DPP), the data point range (DPR) and the number of data points (NoDP) was defined. Based on ten measured ms ACE source data sets 20 specific parameter sets were selected by Design of Experiments. Monte Carlo simulations using 100 000 repeats for every parameter set were employed. The resulting measurement uncertainty propagation factors (measurement uncertainty multiplier: MUM) were used to describe the whole design space by polynomial regression. The resulting 5-dimensional response surface was investigated to evaluate the design parameter's influence and to find the minimal uncertainty propagation. It could be shown, that the nMRR is of highest importance, followed by DPP and DPR. Interestingly, the NoDP is less relevant. However, the interactions of the four parameters need to be carefully considered during design optimization. Using at least five data points which cover over 40% of the upper part of the binding hyperbola (DPP > 0.57) the MUM will be minimized (MUM approximately 1.5) when the nMRR is appropriate. It is possible to reduce the measurement uncertainty propagation more than one order of magnitude.

Ultraprecision Diameter Measurement of Small Holes with Large Depth-To-Diameter Ratios Based on Spherical Scattering Electrical-Field Probing

In order to solve the difficulty of precision measurement of small hole diameters with large depth-to-diameter ratios, a new measurement method based on spherical scattering electrical-field probing (SSEP) was developed. A spherical scattering electrical field with identical sensing characteristics in arbitrary spatial directions was formed to convert the micro gap between the probing-ball and the part being measured into an electrical signal. 3D non-contact probing, nanometer resolution, and approximate point probing—which are key properties for high measurement precision and large measurable depth-to-diameter ratios—were achieved. A specially designed hole diameter measuring machine (HDMM) was developed, and key techniques, including laser interferometry for macro displacement measurement of the probe, multi-degree-of-freedom adjustment of hole attitude, and measurement process planning, are described. Experiments were carried out using the HDMM and a probing sensor with a ϕ3-mm probing ball and a 150-mm-long stylus to verify the performance of the probing sensor and the measuring machine. The experimental results indicate that the resolution of the probing sensor was as small as 1 nm, and the expanded uncertainty of measurement result was 0.2 μm (k = 2) when a ϕ20-mm ring gauge standard was measured.

Rapid and robust on-site evaluation of articulated arm coordinate measuring machine performance

This paper proposes a quick and efficient methodology of uncertainty estimation on measurement results provided by an articulated arm coordinate measuring machine (AACMM). The methodology is highly adapted to industrial applications—a frequent use of these devices—but can also be performed in laboratories. The study stems from an actual need among coordinate measuring arm users to estimate the uncertainty associated with their equipment in specific conditions on the shop floor. It is important to mention that no simple and quick test exists currently to estimate the measurement uncertainty of results obtained with an AACMM in the conditions of the measurement site. In fact, the guidelines and studies addressing measuring machines propose protocols to verify performance or to evaluate uncertainties associated with measurement results, but these protocols are laboratory-type tests (carried out after purchase, re-calibration, etc) and usually take hours to complete.

National features of calibration

The article deals with the current issues of calibration of test equipment and measuring instruments. These issues arise in laboratory activity in accordance with the requirements of DSTU ISO/IEC 17025:2006. Sources of inaccuracies and different interpretations of the term “calibration” and the formulation of its results are given, the ways of solving problems connected with practical calibration are substantiated and proposed. Unsubstantiated application of requirements for calibration of laboratory supplementary equipment (thermostats, refrigerators, etc.) are shown as examples. The principal difference between calculating uncertainty of measurement in calibration and uncertainty of measurement result by measuring instrument to be calibrated is shown. The considerations on the optimal choice of ratio for the accuracy characteristics of the measurement standards and the measuring instruments to be calibrated are given. It is shown that it is necessary to develop documents that would clarify and eliminate the existing differences in interpretation of the concept, process and reporting of the results of calibration.

The influence of instrumental factors at uncertainty evaluation of scintillators technical light output measurements

This article complements the cycle of previous works that were devoted to the evaluation of uncertainty of measurement results of cylindrical scintillators on the base of NaI(Tl), CsI(Tl), CWO, BGO, p-terphenyl, anthracene, stilbene and long length strips based on polystyrene (PS strip) technical light output in photons/MeV (ph/MeV). The comparison method with the working sample was used. The investigated scintillators were manufactured at the Institute for Scintillation Materials of the National Academy of Sciences of Ukraine (ISMA NASU). Technical light output of the scintillators was in the range from 38 ph/MeV for strips to 55000 ph/MeV for CsI(Tl).In this work, we compared the estimates of instrumental uncertainty of type B of the measurement results of the technical light output of scintillators using pulse and current measurement modes. Factors influencing the magnitude of instrumental measurement uncertainty are determined. The contributions of these factors to the instrumental uncertainty for specified measurement modes are evaluated. It is established that the value of instrumental measurement uncertainty is related to the limited sensitivity of the scale of analyzing instrument and depends on the number of divisions of the used scale and the location of the measured parameter on this scale. The calculated values of contributions’ estimates to the uncertainty of the measurement results of the technical light output of scintillators are in the range from 0.05 to 0.18 % for CsI(Tl) and from 0.95 to 2.45 % for strip No. 1.Based on the results of the instrumental uncertainty estimates received in this work and taking into account the results of previous studies, the measurement uncertainty budgets for the technical light output of scintillators based on CsI(Tl) (pulse mode) and strip No. 3 (current mode) are compiled.

Validation of Test Methods, Human Errors and Measurement Uncertainty of Results

Validation of Test Methods, Human Errors and Measurement Uncertainty of Results

Validation of Test Methods, Human Errors and Measurement Uncertainty of Results

Validation of Test Methods, Human Errors and Measurement Uncertainty of Results