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Description / Abstract:
General
This Standard presents a working outline detailing and illustrating
the techniques for estimating
measurement uncertainty for fluid flow in closed conduits. The
statistical techniques and
analytical concepts applied herein are applicable in most measurement
processes. Section 2 provides
examples of the mathematical model applied to the measurement of fluid
flow. Each example includes
a discussion of the elemental errors and examples of the statistical
techniques.
An effort has been made to use simple prose with a minimum of jargon.
The notation and definitions
are given in Appendix A and are consistent with ISO 3534, Statistics -
Vocabulary and Symbols
(1977).
The Problem
All measurements have errors. The errors may be positive or negative
and may be of a variable
magnitude. Many errors vary with time. Some have very short periods
and some vary daily, weekly,
seasonally, or yearly. Those which can be observed to vary during the
test are called random
errors. Those which remain constant or apparently constant during the
test are called biases, or
systematic errors. The actual errors are rarely known; however,
uncertainty intervals can be
estimated or inferred as upper bounds on the errors. The problem is to
construct an uncertainty
interval which models these errors.