Calibration uncertainties

For testing laboratories, the extent to which the requirements in establishing traceability should be followed depends on the relative contribution of the calibration uncertainty to the total uncertainty. If calibration is the dominant factor, the requirements should be strictly followed. 

Volume measurements include the use of pipettes, volumetric flasks, measuring cylinders, and burettes. Each has different calibration uncertainties that are detailed in the manufacturer s information supplied with the... 

The mathematics are even simpler when contributions to the uncertainty of a single quantity are combined. Here the sensitivity coefficient is 1, and the individual uncertainties are just squared and summed. For example, for the combination of the standard uncertainties of the effects on the volume delivered by a pipette discussed above, which are repeatability, calibration uncertainty, and the effect of temperature, the square of the combined uncertainty is simply the sum of the squares of each effect ... 

Precision in the measured diffusivities is limited by the reproducibility of the echo height measurements and by field gradient calibration. Under favorable circumstances, both of these can be kept below about 1 %, although for less time-consuming and routine measurements, 2-3 % random uncertainty is more typical. If comparisons among different samples are more important than comparisons with other work on similar samples, then calibration error is quasisystematic and secondary. In that case, perhaps 4% calibration uncertainty may be acceptable, requiring measurement of G or G0 to within 2% (see Eqs. 1, 2). 

Scattering intensity measured by the pulse height analyzer is related to particle size by calibration with monodisperse latex spheres or nearly mono-disperse NaCl particles. Calibration uncertainties have been studied and discussed (86-91). These studies show that the smallest particles that can be sensed by the ASASP probe are somewhat larger than the 0.12 xm stated by the manufacturer. Similarly, it is reported that detection of particles larger than about 2 xm is unreliable because of attenuation of the laser power. 

In reading various HO measurement reports [including Hard et al. (78)], we find too little attention given to clearly expressing how the uncertainty limits are derived. This negligence may be the result of assuming such uncertainties are trivial to calculate. However, future reports should state explicitly whether la, 2a, 90% confidence limits, and so forth employ Gaussian or Poisson statistics and whether the quoted uncertainties are internal to the ambient HO data or include calibration uncertainties. 

Due to the photometric measurement Starting from calibration uncertainty and run-to-run variation 0.018 0.060 0.010 0.025... 

Evaluation of the calibration uncertainty component is the most important component the uncertainty of results depends on the uncertainty value of the CRMs used for the calibration and the quantitative relationships between uncertainty and traceability, which are two fundamental concepts of metrology which are intimately linked. In this way the traceable instrument calibration is an important step in assuring the traceability of spectrochemical results. 

The linear calibration uncertainty is estimated by the interval that can be expected to encompass a large fraction of the distribution of values that could be reasonably attributed to the linear curve. This interval, indicated in Fig. 5, is due to the linear adjustement of the concentration values used to determine the regression line and obtained values of the absorbance. 

The evaluation of the linear calibration uncertainty sCm can be performed against the standard deviation of the linear calibration curve, s0 the slope of the curve, b the number N of CRMs used for calibration curve the... 

Some results of the calibration uncertainty evaluation, due to the linear calibration curve of copper determination cm by molecular absorption spectro (photo)-metry using a Cecil 2020 instrument are illustrated in Table 2. Note that at the end of the linear range (0-10) mg/1 the calibration uncertainty is bigger than in the middle of the linear range for a concentration of 0.987 mg/1 copper the uncertainty component due to the calibration is 3% and for a concentration of at 6.010 mg/1 copper the uncertainty component due to the calibration is 0.56%. 

In addition to the uncertainty due to the linear regression which was 0.034 for 6.010 mg/1 copper, the overall uncertainty of the instrument calibration includes the uncertainty due to the photometic measurement and the uncertainty due to the CRMs. The overall calibration uncertainty was 0.036 for 6.010 mg/1 copper. 

In this approach, calibration uncertainty is an important component of the traceability chain and uncertainty of results depends on the uncertainty of the certified values of RMs used for the calibration. Thus, the results are traceable to the standards used for the instrument calibration. The traceability of certified values of RMs is as important as that of spectrometric measurements. Therefore, it is necessary to use the spectrometric RMs that are characterized in a metrological manner. In this framework, the uncertainty and traceability, as two fundamental metrological concepts, are intimately linked. 

Keywords Traceability Carbon dioxide determination Calibration Uncertainty... 

Gamma-ray sources for efficiency measurements as standard sources are characterised in terms of photon emission flux in 4tc sr, expressed in s, for each specified gamma-ray. The activity of the source is indicated. When an activity standard is used to determine the efficiency of a y-ray spectrometer as a function of photon energy, certain decay scheme parameters are required (gamma branching ratio, internal conversion coefficient, etc.). In this case, the calibration uncertainty is the combination of the uncertainty on the activity of the standard and of the uncertainties on the parameters of the decay scheme. 

Figure 20.1 Ishikawa diagram of the parameters which lead to the area of an HPLC peak. Mass means the weighed sample or analyte. For its dilution n measuring flasks (MF) and m pipettes (Pip) are needed. MPE is the maximum permissible error of a volumetric operation, i.e. the combined effects of calibration uncertainty and repeatability. Other abbreviations z = wavelength acc.= accuracy rep. = repeatability S/N = signal-to-noise ratio.

Fig. 1.3. This figure shows a small section of the rotational spectrum of ethyleneoxide in the presence of a magnetic field of 25.672 kG. A Stark effect modulated microwave spectrometer operated with AM = 0 selection rule was used for this recording, which actually consists of two superimposed absorption spectra. One of these spectra is observed in the absence of the modulating Stark field (above the horizontal line) and the other is observed during the periods when the modulating field is switched on (below the horizontal line). In most investigations only the upper part (pure Zeeman effect) is used for the analysis, since calibration uncertainties and the inhomogoneity of the modulating Stark-field lead to a reduced accuracy of Zeeman data derived from the splittings observed in the simultaneous presence of both fields...

Calibration uncertainty should be evaluated and propagated. The causes of calibration uncertainty include uncertainties in the reported values of calibration standards, measurement uncertainty in the laboratory such as counting statistics, and in processing standards. 

The reality can well be approximated by keeping an unknown systematic error constant in each simulation, but vary it between simulations. Examples are probe diameters, temperatures and temperature gradients, calibration-uncertainties of material measures, etc. 

In addition, the uncertainty in temperature measurement has to be taken into account. From experience, one can say that the calibration uncertainty of DSCs amounts to approximately 1 K. A further 0.5 K uncertainty contribution is added here to account for thermal lag of the polymer sample and possible poor thermal contact. This applies to both the measurement on the test sample and the literature values. This uncertainty in temperature is converted to an uncertainty in enthalpy by using an average enthalpy/temperature coefficient of 1.6 Jg for all three contributing phases. 

Nevertheless, even taking into account the above explanations, Ellison accepted that r cannot be recommended as a unique goodness-of-fit criterion in all cases it can be applied to control calibration uncertainties and departures from linearity in typical applications with the only requirement that the reference concentrations are systematically dispersed across the calibration range. 

Calculations on this isotope also in 74LOV1. Systematic calibration uncertainty is 0.002 cm"... 

Calibration uncertainties, related to the application of quench curves. 

The calibration uncertainty associated with a specific quench curve is often neglected or under-estimated. For many users of LS measurements a quench curve is a black box given by the supplier of the instrument. These quench curves are the result of a curve fit which is quite difficult to reconstruct from the suppliers software. 

In this paper the calibration uncertainty associated with LS-coimting of H, C, Sr and... 

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