ASME PTC 19.1:2018 pdf free download

ASME PTC 19.1:2018 pdf free download.Test Uncertainty.
The assumptions inherent in test uncertainty analysis include the following:
(a) the test objectives are specified
(b) the test process, including the measurement process and the data reduction process, is defined
(c) the test process, with respect to the conditions of the item under test and the measurement system employed for the test, is controlled for the duration of the test
(d) the measurement system is calibrated and all appropriate calibration corrections are applied to the resulting test data
(e) all appropriate engineering corrections are applied to the test data as part of the data reduction and/or results analysis process
In this Standard, there is a careful distinction between the terms “errors and uncertainty.” Error, discussed in subsection 3-2, is the difference between a particular quantity that is being measured or estimated, called the “measurand,” and its corresponding true value. The actual error of a measurement cannot be known but its effect may be estimated. This estimate is called the uncertainty. Uncertainty is an interval around a measurement in which the true value of the measurand is expected to lie.
Uncertainty is not the error of the measurement but an expression of the expected limits for the measurement error at a chosen level of confidence. For expanded uncertainty, 95% level of confidence has been used throughout this document in accordance with accepted practice. Other confidence levels may be used, if required (see Nonmandatory Appendix B).
3-2 MEASUREMENT ERROR
Every measurement has error, which results in a difference between the measured value, X, and the true value. As Figure 3-2-1 illustrates, the difference between the measured value and the true value is the total error, & Since the true value is unknown, total error cannot be known and therefore only its expected limits can he estimated. Total error consists of two components: random error and systematic error (see Figure 3-2-1). Reducing measurement error requires reducing random and/or systematic errors.The effect of controlling these errorcomponents is highlighted in Figure 3-2-2.