Quiz Corner: Accuracy and repeatability

Which of the following statements are true? 

A.  The repeatability of a flowmeter is important.

B.  An accurate flowmeter is better than a repeatable flowmeter.

C.  A flowmeter cannot be accurate unless it is repeatable.

D.  An accurate flowmeter costs about the same as a repeatable flowmeter.

Answer A, Answer B and Answer C are true statements. Repeatability is important but it is limited to describing how consistently the flowmeter measures under the same operating conditions. Note that a repeatable flowmeter may exhibit error, but the error will be the same every time it is operated at the same conditions. An accurate flowmeter has to be repeatable because it consistently measures correctly. An accurate flowmeter is more desirable than a repeatable flowmeter. 

Additional complicating factors

Answer D can be true depending upon the technology and manufacture of the flowmeter. Oftentimes, the price of a particular flowmeter is not based on its performance but rather its competitiveness with other flowmeters of the same technology. In addition, the good reputation of the manufacturer can allow the manufacturer to command a higher price.

It would be prudent to compare flowmeter specifications to select the best flowmeter for your application. In doing so, you may find that the most expensive flowmeter is not necessarily the best flowmeter.

David W. Spitzer is a principal at Spitzer and Boyes, LLC, which offers engineering, focused market research, writing/editing white papers, strategic marketing consulting, distribution consulting, seminars and expert witness services for manufacturing and automation companies. Spitzer has written more than 400 technical articles and 10 books about flow measurement, instrumentation and process control. He can be reached at 845-623-1830 or via spitzerandboyes.com.