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  are rewritten to both add to the available technology for uncertainty analysis and to make it easier for.
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When a data set of interest from the test m meter involves multiple calibrations, the calibration process random standard uncertainty will cause scatter in the individual test meter data samples and thus should remain adme as calibration o random standard uncertainty in the uncertainty analysis.
ASME PTC 19.1-2005 试验不确定度 Test Uncertainty.pdf
The American Society of Mechanical Engi. Using the uncertainty model and associated assumptions presented in subsectionexpressions for the w percentage contributions from elemental sources of standard uncertainty were derived and are presented below. Suppose variable X presents the special case where f X p X, i. Furthermore, it may be used to evaluate the need amse calibration. All of the bYj uncertainties are assumed to be completely correlated with each other, and all of the bXj uncertainties are assumed to be com- w pletely correlated with each other.
Other confidence levels may be used, if required. For example, if experience indicates that timeto-time and test apparatus-to-apparatus ase are significant, a test design that averages amse test results aske one rig or for only one day may produce optimistic random uncertainty estimates ptd to testing several rigs, each monitored several times over a period of several days.
Consequently, one can be 95 percent confident that the interval Knowledge of the frequency distribution and standard deviation of this population permits de- The new nomenclature is expected to render PTC There are many situa- tions where systematic errors for some of the parameters in a result are not independent.
As a result of the of individual parameters is required. For some elemental systematic error sources, published infor- wmation from calibration reports, instrument specifi- interval divided by a statistic that is appropriate for the frequency distribution of the error population.
The assumptions required for using this equation are presented in xsme Circumferential variations may also be present. Transactions of the ASME: Furthermore, assume 199.1 the higher ptd terms in the Taylor series expansion for r are negligible compared to the first order terms.
If there is not valid engineering justifica- tion to remove the suspected outliers and if removal of the outliers will significantly change the test result and its associated uncertainty, the validity of the test should be questioned. The sensitivity of the result to each of the individual parameter uncertainties is calculated, either numerically or analytically, in accordance with subsection Calibrations are also used to provide traceability to known reference standards or physical constants, or both.
Otherwise, these elemental systematic standard uncertainties are combined per subsection This interval accounts for systematic errors only. The term sc in eq.
Typically, these larger data sets are taken in the early phases of an experimental program. A-2 may be used to obtain a w better estimate of the true value than either of the individual measurements.
ASME PTC – Test Uncertainty
For two measurement methods with the means X1 and X2, eq. If in each of the N measurements of the variable X the output of an elemental component is averaged Nk times to w obtain Xk, then the method in para. A quick and easy way to numerically calculate the sensitivity coefficients of the independent m parameters is to develop a table using a spread- sheet program on the personal computer.
The random standard uncertainty of the sample mean is related to the sample standard deviation as follows: These new values can be inserted into the tables spreadsheets used for the uncalibrated case.
In addition, careful attention was paid to discriminating be. A weighting principle which is statistically valid 4.
The published degrees of freedom for this value is Thus, an engineer who is concerned with the performance of a mass-produced item, such as 199.1 transistor or a lamp, would generally be interested in a tolerance interval to enclose a high proportion of the sampled population.
The traverse points are located at the centroid of equal areas so that the integrated-average velocity in the pipe is approximated by the average of the velocities determined at the traverse points.
The statistics from repeated tests allow for quantifying the expected variation in a parameter or in a result derived from parameters. Similarly, a turbine engineer who is bidding on an order of three units based upon his past experience on five units of the same type, would use a prediction interval to obtain specification limits to contain the performance parameter for all three units with w a high probability.
If the published information is presented as a multiple of a standard deviation, then the elemental systematic standard uncertainty is estimated as the multiple of the standard deviation divided by the multiplier. The Pitot tube, digital pressure transmitter, and DAS are calibrated together as a system.
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xsme The overall reported result will usually be combined to provide the mean of the multiple results, R. The user does not have enough information to properly correct the thermocouple reading for these effects, but wishes to account for them in an uncertainty analysis.
Elemental errors are classified as random if they wadd scatter to a result. For random standard uncertainty in the Xj or X values, the general approach in  should be used.
Example adapted from : The uncertainty interval is composed of both the systematic and random uncertainty components. For small samples, bad data points are hard to identify. For small degrees of freedom, see Nonmandatory Appendix B.