Which of the following forms describe how the accuracy of a magnetic flowmeter would typically be expressed?
A. Percent of rate
B. Percent of full scale
C. Percent of measured value
D. Percent of calibrated span
E. Percent of span
The accuracy of magnetic flowmeters is typically expressed as a percentage of rate, (Answer A) which is the same as a percentage of measured value (Answer C). However, the additional accuracy associated with the accuracy of the analog output is typically expressed as a percentage of full scale (Answer B) that is the same as a percentage of span (Answer E).
Additional complicating factors
The measurement accuracy of the analog output is the magnetic flowmeter accuracy plus the analog output accuracy expressed as a percentage of rate. In addition, accuracy is degraded at low flow rates.
David W. Spitzer is a regular contributor to Flow Control magazine and a principal in Spitzer and Boyes LLC, which offers engineering, seminars, strategic, marketing consulting, distribution consulting and expert witness services for manufacturing and automation companies. Spitzer and Boyes is also the publisher of the Industrial Automation INSIDER. He has more than 40 years of experience and has written more than 10 books and 350 articles about flow measurement, instrumentation and process control.
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