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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Suppose the user of the asm couple in the example in para. As noted in para. Most instru- calibration process, the systematic standard uncer- mentation, however, yields a point measurement of tainty of the test meter is replaced by that of the master meter. Journal of Fluids En- Engineering Education, As the difference between the two measurements increases, the overlap region shrinks. The example looks at each case in both absolute and relative i.

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. Design and Analysis of Industrial Experiments. This is true since the systematic uncertainty component of a parameter BXi is assumed to equal two times the standard deviation square root of the variance of the possible distri- bution of systematic uncertainty.

ASME PTC – Test Uncertainty

In addition, the objective of the test may affect the categorization as discussed in para. The results of this analysis are summarized in Table Therefore, it is important to select the power setting such that measurements are at least at the midscale of the power supply range.

Friedman, Vice Chair S. As discussed in para. The random standard uncertainty for the curve- fx fit will be determined using standard least squares analysis [9, 14, 16], where the assumption is made that there is no random standard uncertainty in the X values and the random standard uncertainty z in the Y values is constant over the range of the curve-fit.

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Prior to using the weighting techniques described in this section, the means and their associated uncertainty intervals from each of the independent methods should.

It is beyond the scope of any Code to determine or interpret how such comparisons shall be www.

An example of an averaged output is an averaging pressure probe often used to measure average velocity at a cross section of pipe. This of the is combined with average measure- ment. Additionally, a pretest uncertainty analysis facilitates communication between all parties to the test about the expected quality of the test.

Prc uncertainty intervals have been grossly underestimated, or the true value is not constant. In the second program, the same pressure transducer was used for both tests; there- w fore, the systematic standard uncertainty was the same and was correlated for the two test measurements.

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

The analysis shows that random errors in the volumetric flow rate measurement and systematic errors in the pressure drop measurement are the largest contributors to the overall uncertainty in loss coefficient. The starting point for the analysis could begin. This is important and useful because it provides insight into whether a particular test or methodology is fx feasible based on the acceptable order of magnitude in uncertainty. Special tests had previously been conducted to determine if taking additional traverse points 20 along each of the 4 radii would result in a significant change in the measurement of the overall average velocity in the pipe, as computed using eq.

For example, different Defined Measure- w ment Processes for the same test will result in different estimates of measurement uncertainty. Consequently, one can be 95 percent confident that the interval From a sample of more than 30 readings using the thermocouple, the user finds that X p Here is an explanation of when to use confidence, tolerance, and prediction intervals. For example, calibration corrections, which are assumed fixed over the life of the calibration interval, can be considered variable if the process consists of a time interval encompassing several different calibrations.

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If the function r X1, X2. As part of this effort the effect of measurement uncertainty must be considered. The difference between the two test results was compared to the previously reported uncertainty to illustrate the importance of applying all known engineering corrections and using appropriate engineering relationships as part of the results analysis process.

Variability in independent test results obtained under different test conditions, varying experimental setups, or configuration changes allow for additional between-test random errors.

The approach will be to relate the deviations w in r X1, X2. Typically, these larger data sets are taken in the early phases of an experimental program. Flowmeters 1, 2, 3, and 4 Calibrated Against the Same Standard. Repeated Tests When more than one test is conducted with the same instrument package i.

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Once the slope and intercept are calculated from eqs. The proposed code or standard was made available for public review and comment that provides an opportunity for additional public input from industry, academia, z regulatory agencies, and the public-at-large. From the definition of mass flow rate, the velocity can be replaced with the volumetric flowrate Q through the expression Q p AV, where A is the cross-sectional area of the tube. Tests are often conducted using.

The uncertainty is calculated using the method in subsections through This is due to incomplete estimated by evaluation of the variation in the sampling of a profile which varies as a function radial averages. The term sc in eq.

This avoids the need to develop weighting factors fx for each sample area.