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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Comparison of the previously reported test result with the more exact value determined by eq. A t value of 1.
If the function r X1, X2. 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. The uncertainty in power required to generate a constant heat flux will depend on the type of material being tested. The coverage factor is the value from the t distribution for the required confidence level corresponding to the effective degrees of freedom.
One measurement will not give the asmd average value directly. Statistical Theory and Methodology in Science and Engineering, 2nd edition. If instead previous information is used to obtain sXk, then the method in para.
In successive measurements of the parameter, the values of these elemental random error sources change resulting in the random scatter evident in the successive measurements. Measurements at each traverse point can be used to determine local fluid velocity.
This example is nearly identical to that presented H2O. This is due to incomplete estimated by evaluation of the variation in the sampling of a ptx which varies as a function radial averages. The standard deviation published from these past tests was assumed to be representative of the systematic standard uncertainty for the present test resulting from spatial variation in the radial direction.
At low Reynolds numbers, the flow is laminar and has a parabolic velocity profile.
Circumferential variations may also be present. 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 Engineering for Power.
It will vary as a function of sample size. Each of the elemental random standard uncertainties of the mean sXk is calculated using the methods described in para. The appa- ratus consists of a closed loop tube containing. ASME Performance Test Codes provide test procedures which yield results of the highest m level of accuracy consistent with the best engineering knowledge and practice currently available. Consider an example where the result R is determined from three parameters X1, X2, X3 that have correlated systematic errors.
However, this practice decreases the probability of rejecting bad data points. 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. The steps in the development of the table are as follows: It is identical to the median 50 percent point and mode most common value of the distribution.
There were no correlated systematic standard uncertainties common between these two transducers. The combined standard uncertainty of the measurement mean, which is the total uncertainty at the standard deviation level, is calculated as follows: Both of these values are equal to 4. Figliola, Clemson University H. This article describes three fx different types of statistical intervals and shows where each should be used.
The uncertainty interval for c may be calculated as follows: 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. The absolute systematic standard uncertainty for w the test result is [see eq. In this section, only a special case is considered for the systematic standard uncertainty. 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.
Usually these estimates are made us- o ing engineering judgment and are therefore ISO Type B estimates.
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The necessary values for pa- first step is to define the individual systematic rameter sensitivity, systematic standard uncertain- and random standard uncertainties of the mean ties, random standard uncertainties, and combined in terms of their relative individual percentage standard uncertainty are summarized in the follow- contributions to the combined standard 119.1 ing table.
ASME accepts responsibility for only those interpretations of this document issued in accordance with the established ASME procedures and policies, which preclude the issuance of interpretations by individuals.
The results are summarized in Table Since all of the systematic standard uncertainties for Xj and Xnew are correlated, the systematic standard errors are all the same. Typically, these larger data sets are taken in the early phases of an experimental program.
Case 3, where a partial overlap of the uncertainty intervals exists, is the most difficult wto analyze. By comparing known input values with their mea- is the testing of a gas turbine engine in an altitude sured results, estimates of the data acquisition facility.
ASME PTC 19.1-2005 试验不确定度 Test Uncertainty.pdf
The sensitivity of the result to each of the individual parameter uncertainties is calculated, either numerically or analytically, in accordance with subsection Final classification is dependent on the bcp calibration wsme initial systematic stan- Defined Measurement Process.
Because of the resulting effect of combining the elemental uncertainties in a root-sum-square manner, the larger or dominant ones will control. The point velocity values at individual traverse points are treated as measurements Section 6 ; the average velocities calculated from these point velocities are treated as results Section 7.
The difference between the results of these tests is an indication of the effect of the design change.
ASME PTC – Test Uncertainty
Mean X p 1. The Amer-  Steele, W. Using the uncertainty model and associated assumptions presented in subsectionexpressions for the w percentage contributions from elemental sources of 19.11 uncertainty were derived and are presented below.
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.