The industry's most authoritative handbook on flow measurement provides a road map to the field of flow measurement. This best-seller discusses strategies for problem solving and puts the whole array of types of flowmeters at the reader's disposal. The text includes laminar flow elements, critical flowmeters, statistics for measurement, laboratory primary standards, and uncertainty in flow measurement. Emphasis is placed on the importance of accuracy in measurements and ways of ensuring accuracy and avoiding equipment damage through correct forecast of operating conditions, flowmeter selection, installation, calibration, and maintenance. Fundamental considerations such as mixed-phase flow, piping effects, and flow conditioning are examined at length. The problem of attaining a meaningful flow signal through linearization, compensation, and totalization is discussed. Join the thousands of engineers, technicians, managers, and salespeople that have found this reference text an invaluable resource.
TABLE OF CONTENTS Chapter 26 - Uncertainty in Flow Measurement
is performed, at best, it can only be an estimate of the true value being measured.
Perhaps no field of metrology demonstrates this more clearly than flow
measurement. At the same time, accuracy of measurement is often of the greatest
importance, whether to ensure fairness of trade in the custody transfer of highvalue
products or to optimize plant efficiency so as to minimize operating costs or
environmental impact. It is therefore important for the metrologist to be able to
place limits on the reliability of measurement and, in effect, to say:
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Most of Flow Measurement 2nd Edition is devoted to describing techniques for
defining the nominal flow rate y m3/h; this chapter describes how to estimate the
reliability of that value, that is, how to estimate the uncertainty bandwidth x m3/h.
There are many excellent texts dealing with the subject of uncertainty analysis,
and this chapter sets out only the basic principles. The definitive text is the ISO
Guide to the Expression of Uncertainty in Measurement (known colloquially as
"the GUM"). Those studying the subject for the first time will find the Beginner's
Guide to Uncertainty of Measurement by Stephanie Bell to be an excellent and
very readable introduction to the topic. A short bibliography is provided at the end
of this chapter.
The Calculation of Uncertainty
The basic procedure for calculating uncertainty is the same whether one is dealing
with a factory-calibrated meter being used in accordance with the manufacturer's
recommendations or with a more complex situation, where the uncertainty
of a national standard facility is being derived from considerations of all the associated
instrumentation and procedures.
