What is the difference between uncertainty and accuracy in flowmeters?

Béla Lipták says the there is no such thing as a perfect detector, therefore we never know what "true value" is.

CG1602 ATE Flow

Question What is the difference between uncertainty and accuracy in flowmeters? Why do custody transfer ultrasonic flowmeter manufacturers state uncertainty value instead of accuracy? A. Rahimia.rahimi@tam.co.ir Answer Accuracy (or more precisely, "inaccuracy" or error) can be defined as the closeness of the result of a measurement to the true value of the measurand. Unfortunately, we never know what that "true value" is, because there is no such thing as a perfect detector. Uncertainty should reflect this, by using the term uncertainty as the sum of the inaccuracies of the instrument and of the reference. Unfortunately, some vendors play "specmanship" with these terms,…

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Timeless Resources

2016 Readers' Choice Awards

CG1601 WebCoverFor more than 20 years, the Control Readers' Choice Awards have honored the best suppliers in the process automation industries.We're excited to name the Readers' Choice Awards Class of 2016. Find out which products and brands our readers rely on to get the best combination of performance, ease of use, reliability and reasonable cost to keep their plants running.

Today's top 50 process control and automation suppliers

CG1512 WebCoverThis report, written by Control's Executive Editor Jim Montague, ARC Advisory Group Allen Avery and Larry O’Brien, presents the current Top 50 automation companies. Today's leaders faced off old and new challenges, took risks and made changes to survive the on-going economic storm. Read more.

Voices: Ask The Experts

How PLCs of critical facilities are protected from cyber attacks

Engaged employees are the best protection. Employees are the weakest link in industrial security, so they need to be trained, tested and engaged to protect their systems.

Questions What is being done to protect the malware-vulnerable programmable memory of the PLCs of critical facilities? Anything? It is possible to program a PLC memory and then program a lockdown so the memory becomes write-once rather than write-always, and thus would be immune to malware attacks.

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  • How PLCs of critical facilities are protected from cyber attacks

    Questions What is being done to protect the malware-vulnerable programmable memory of the PLCs of critical facilities? Anything? It is possible to program a PLC memory and then program a lockdown so the memory becomes write-once rather than write-always, and thus would be immune to malware attacks.

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