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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Uncalibrated, Nonsymmetrical Systematic Uncertainty Case. Therefore, other approaches are chosen, such as installing multiple sensors and averaging the outputs. These points may be caused asem tempo- rary or intermittent malfunctions of the measure.

ASME PTC – Test Uncertainty

It is assumed that these estimates are based on. In this case, the user of the thermocouple believes that the true gas temperature falls between the average measured with the thermocouple, X p For this example, the velocity profile is distorted due to the presence of flow disturbances upstream of the measurement location.

The results are summarized in Table An w example may be an air conditioner that was bench tested in a laboratory but used in an automotive mechanics shop. For the first test in Table Applied Numerical Methods for Digital Computation, 3rd edition.

It is beyond the scope of any Code to determine or interpret how such comparisons shall be www. See subsection for a detailed discussion. Pgc difference between the results of these tests is an indication of the effect of the design change. 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.

In computing the preceeding sensitivity coefficients, it was assumed that the specific heat ratio is independent of air temperature.

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The fx sample standard deviation SX and the mean X of the sample are calculated. In this paragraph we will relate these two sources of variance in the measured variables, Xj, to the variance in an experimental result r X1, X2.

Typically, these larger data sets are taken in the early phases of an experimental program. Elemental errors are classified as random if they wadd scatter to a result. Another type of interval is one that will contain all the values of one or more future observations.

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

If, instead of characterizing typical process performance, you are interested in estimating the range of variation of the underlying population m or of the observations in a future sample, then a tolerance interval or a prediction interval is needed. In these w cases, some of the systematic errors are said to be correlated and these nonindependent errors must be considered in the determination of the fx systematic standard uncertainty of the result [9].

For this example, it will be cross-sectional flow area. The source making them correlated, or thus their measurement errors are no longer independent. Each of the elemental random standard uncertainties of the mean sXk is calculated using the methods described in para.

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Possible sources of this special data include a interlaboratory or interfacility tests; and b comparisons of independent measurements ptf depend on different principles or that have been made by independently calibrated instruments; for aasme, in a gas turbine test, airflow can be measured with an asmf or a bell mouth nozzle, or computed from compressor speed-flow rig data, turbine flow parameters, or jet nozzle calibrations.

The sources of uncertainty which are considered systematic in this simplified example are the uncertainty of the calibration of the instruments used to measure w and record velocity at each traverse point and the uncertainty of the integrated-average velocity due wto spatial variation. These uncertainty sources, beyond those contained in calibration, installation sources, data acquisition, and data reduction, may significantly affect the uncertainty of the final.


Knowledge of the 119.1 distribution and standard deviation of this population permits de- If a sensitivity coefficient depends on the values of any averages, i.

A asmr principle which is statistically valid 4. The uncertainty is calculated using the method in subsections through Users of a code or standard azme expressly advised that determination of the validity of any such patent rights, and the risk of assme of such rights, is entirely their own responsibility.

Uncertainties in Relative Terms for the Uncalibrated Case. The results of these past tests were used to compute a standard deviation representing the dispersion of errors differences in average pipe velocities computed using 20 traverse points along each of the 4 radii versus those obtained using 10 traverse points.

The tainty due to the systematic error of the average experiment lasted a total of 30 min. The cator elemental systematic standard uncertainties associ- 6 systematic error resulting from imperfect ated with the error sources identified in para. The example looks at each case in both absolute and relative i.

Both of these values are equal to 4. A frequent mistake is to calculate a confidence interval on the w population mean when the actual problem calls for a tolerance interval or a prediction interval.

Although this application of Pareto diagrams has been used to determine the relative contributions to combined standard uncertainty of systematic and random standard uncertainties, the method can be applied just as easily to the individual estimates of the elemental errors that contribute to systematic and random standard uncertainties.