The edition of ASME PTC will be revised when the Society approves the issuance of the next edition. There will be no Addenda issued to ASME PTC. ASME PTC Test Uncertainty [ASME] on *FREE* shipping on qualifying offers. The scope of this Code is to specify procedures for . (Revision of ASME PTC ). Test Uncertainty. Performance Test Codes. AN AMERICAN NATIONAL STANDARD. Two Park Avenue • New York, NY.
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For this program the test procedure requires that the pressure gage be calibrated just asmee to conducting the test. Steele, Vice Chair G. Statistical Theory With Engineering Applications. Either uncertainty intervals have been uncettainty underestimated, or the true value is not constant.
Journal of Engineering for Power. For a defined frequency distribution, the random standard uncertainty of the sample mean, sX, can be used to define the probable interval about the sample mean that is expected to contain the population mean with a defined level of confidence.
This article describes three fx different types of statistical intervals and shows where each should be used. This uncertainty can be estimated in a variety of ways, including a special tests which provide independent knowledge of the velocity profile; b special tests which compare the measurement technique to other techniques which yield the desired integrated-average; c published reports which document the uncertainty of similar measurement techniques in similar measurement situations; and d evaluation of the variation in test measurements as a function of spatial position.
The effect of outliers is to increase the standard deviation of the system. Elemental random errors may arise from uncontrolled test conditions and nonrepeatabilities yest the measurement system, measurement methods, environmental conditions, data reduction techniques, tpc.
ASME PTC 19.1-2005 试验不确定度 Test Uncertainty.pdf
Asmw tainty due to the systematic error of uncertzinty average experiment lasted a total of 30 min. The same short-term and long-term effects must be applied for other variables affecting gas mileage w temperature, altitude, humidity, road conditions, ww driver variations, etc. Unceftainty uncertainty in power required to generate a constant heat flux will depend on the type of material being tested.
The total random population of measurements that is normally dis- error in a measurement is usually the sum of the tributed. The uncertainty interval is composed of both the systematic and random uncertainty components. As noted in para. The latter describes the limits to which a systematic error may be expected to go with some confidence. The true value being measured is the integrated average of the velocity w over the cross-sectional flow area.
It will vary as a function of sample size. The fuel consumption of an automotive engine changes with altitude and speed. In this case, the random and systematic standard uncertainties of the calibration w process should be combined and carried forward as a systematic standard uncertainty.
The details of the uncertainty 4 systematic error resulting from imperfect analysis are discussed in paras. The table associated with the uncalibrated case is shown here first, as Table Difference between results from. 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.
The mean value for each measured parameter was calculated using eq. This is known as a prediction interval. This case would occur if the same instruments are used to measure Xnew as were same to measure Xj. Ni will be 1 for a single data point or w assigned value of a parameter. The posttest analysis ptf subsection validates the pretest fx analysis, provides data for validity checks, and provides a statistical basis for comparing test results.
This example outlines differences in the analysis for both the uncalibrated and uncertaihty cases. For example, taking multiple measurements as a function of time while holding all other conditions constant would identify the random variation associated uncertainy the measurement system and the unsteadiness of the test condition.
Careful consideration should be given testt designing the test series to average as many causes of variation as possible within cost constraints. Requirements of military and commercial contracts have led to the establishment of extensive hierarchies of standards laboratories.
ASME PTC – Test Uncertainty
The following comments are offered to serve as a guide to the engineer in this process. As can be seen by looking at the formulas shown. At higher Reynolds numbers, uncertaimty profile approaches uniformity and any measurement will yield a tfst estimate of the average velocity. In this case, the following procedure should be employed for constructing a nonsymmetric uncertainty interval for the unknown true value of the quantity being measured see Fig.
The value used is called the assigned value. Treatment of uncertainty intervals with alternate confidence unceetainty, error distributions, and alternate uncertainty equations is addressed in Nonmandatory Appendix B. Sensitivities and uncertainties may also be readings to reduce sX. For example, it can be stated with 95 percent confidence that the interval: The sample standard deviation at each point is summarized in Table It is beyond the scope of any Code to determine or interpret how such comparisons shall be www.
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 unceryainty 4 radii versus those obtained using 10 traverse points.
The relative lengths of the three intervals obtained in the preceding examples are compared in Fig. In this section, only a special case is considered for the systematic standard uncertainty. The first is a detailed report that displays all the information used in the calculation of the nominal value and uncertainty of the result. The effects of a time interval may also be important when considering the stability and control of a test process.
Then the dis- o tribution of Yncertainty will be approximately normal with N expectation. Similarly, a turbine engineer who is bidding on an order of three units based upon same past experience on five units of the same type, would use a prediction interval to unncertainty specification limits to contain the performance parameter for all three units with w a high probability.
For example, from a sample of size N, X is calculated by eq.