ASME PTC 19.1 PDF

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PTC XX. TEST UNCERTAINTY. Proposed Revision of PTC “ Test Uncertainty”. Par Adjustment in response to comment. TENTATIVE. The edition of ASME PTC will be revised when the Society .. All Performance Test Codes must adhere to the requirements of ASME PTC 1, General. Most Sections in this revision of ASME PTC [1] are rewritten to both add to the available technology for uncertainty analysis and to make it easier for.

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The elemental random standard uncertainties associated with the error sources identified in para. Uncertainties in Absolute Terms Example This could, in turn, lead to expression of an uncertainty interval for a test result that does not encompass the true value.

Another situation where previous values of a variable would be useful is when a small sample size N is used to calculate the mean value X of a measurement. Theory and Design for Mechanical Measurements. See Nonmanda- z tory Appendix B. Iyer, Colorado State University J.

The statistics found by combining these duplicated data sets allow for a reasonable estimate of the variations possible in the result that might be due to the control of test operating aeme, or use of different test rigs, instrumentation, or test location.

The partial derivatives for eq. Cases are considered where Xnew has systematic w standard uncertainty which is correlated with that in Xj and where Xnew has systematic standard wuncertainty which is not correlated with that in Xj. Uncalibrated, Nonsymmetrical Systematic Uncertainty Case. The degrees of freedom associated with each Use of the 2 in the above equation is appropriate of the uncertainty estimates are assumed to be as it can be shown using eq. The total uncertainty of the result is then calculated 199.1 root-sum-squaring w the systematic and random contributions.

The list of test variation causes are many and may In some experimental situations, a set of parame- include the above plus environmental and test ters Xi is measured 91.1 a single result, R, is prc variations.

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If the sample standard deviation of the variable being measured is also expected to be representative of other possible random variations in the measurement, e. Sensitivities and uncertainties may also be readings to reduce sX. The 191. conclusion that can be drawn from this figure is the pump is operating consistently when compared since the uncertainty bands overlap.

The total random population of measurements that is normally dis- error pfc a measurement is usually the sum of the tributed. Experimentation Uncer- w tainty Analysis for Engineers, 2nd edition.

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The sample standard awme at each point is summarized in Table Journal of Thermophysics and Heat Transfer, 7: The results of this uncertainty analysis are presented in Tables and in which each symbol has the same description as in Table w Knowledge of the frequency distribution and standard deviation of this population permits de- This section provides an overview of how the measurement process should be defined.

Asje, there is some level of uncertainty associated with the estimate of BXk. Systematic uncer- z tainties can be estimated through manufacturer information, calibrations, and, in most cases, through qsme engineering judgment.

X curve is a mean value for the data set, the curve should be a good representation of the data if the simple linear fit is appropriate. There usually will be some elemental systematic standard uncertainties that will be dom- z inant. Tests are often conducted using. The coverage factor is pc value from the t distribution for the required confidence level corresponding to the effective degrees of freedom. This case would occur if the same instruments are used to measure Xnew as were used to measure Xj.

From a sample of more than 30 readings using the thermocouple, the user finds that X p The systematic values were evaluated and are listed in Table 2.

Therefore, other approaches are chosen, such as installing multiple sensors and averaging the outputs.

ASME PTC – Test Uncertainty

John Wiley and Sons; The conclusions that can be drawn from Fig. These values are also expressed tainty by the nominal value of the parameter. Elemental random errors may arise from uncontrolled test conditions and nonrepeatabilities in the measurement system, measurement methods, environmental conditions, data reduction techniques, etc. As elemental sources of standard uncertainty are m not combined as arithmetic sums but are instead combined as described in subsectionderivation of the percentage contribution of an elemental o source of standard uncertainty to the combined uncertainty is computed as the ratio of the square of the prc standard uncertainty that would.

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The term sc in eq. The sample stan- fx dard deviation sX and the random standard un- certainty of the mean sX are calculated from eqs. In some countries, a national standards laboratory xsme at the apex of these hierarchies, providing the ultimate reference for every standards laboratory. If the function r X1, X2.

The pretest analysis see subsection is used.

ASME PTC 19.1-2005 试验不确定度 Test Uncertainty.pdf

This Supplement bXkp an the estimate of the standard deviation kth elemental error source of Note that in eq. For small degrees of freedom see Nonmandatory Appendix B. As can be seen from this diagram, the combina- tion of bT1, bT2, and bT1T2 is the largest contributor to the combined standard uncertainty, uR, and sP2 p 7.

The estimation of the sample mean and standard deviation based on Ni measurements is calculated as described in para. A statistical technique called In this case, some of the parameters may be based analysis of variance ANOVA is useful for parti- on single measurements and others may be the tioning the total variance by source. However, for test measurements involving a single calibration i.

The most they w can do is obtain an estimate and construct an interval which, with a high probability, contains the quantity of interest.