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AutoQuiz: Plotting Control Valve Characteristics

AutoQuiz is edited by Joel Don, ISA's social media community manager.

This automation industry quiz question comes from the ISA Certified Control Systems Technician (CCST) program. Certified Control System Technicians calibrate, document, troubleshoot, and repair/replace instrumentation for systems that measure and control level, temperature, pressure, flow, and other process variables. Click this link for more information about the CCST program.

In the plot of inherent control valve characteristics shown in the post image, what characteristic does curve C represent?

a) equal percentage
b) leak tight shutoff
c) linear
d) quick opening
e) none of the above

Leak-tight shutoff is not represented on this chart. Curve B represents the linear valve characteristic, where each increment of valve movement provides the same incremental increase in flow. Curve A represents the quick opening valve characteristic, where the flow increases rapidly with valve movement.

The correct answer is A, equal percentage. Curve C represents the equal percentage valve characteristic, where each increment of valve movement provides the same percentage increase in flow.

Reference: Hans D. Baumann, Control Valve Primer: A User's Guide, Fourth Edition.

About the Editor
Joel Don is the community manager for ISA and is an independent content marketing, social media and public relations consultant. Prior to his work in marketing and PR, Joel served as an editor for regional newspapers and national magazines throughout the U.S. He earned a master's degree from the Medill School at Northwestern University with a focus on science, engineering and biomedical marketing communications, and a bachelor of science degree from UC San Diego.

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Joel Don
Joel Don
Joel Don is an independent content marketing, social media and public relations consultant. Prior to his work in marketing and PR, Joel served as an editor for regional newspapers and national magazines throughout the U.S. He earned a master's degree from the Medill School at Northwestern University with a focus on science, engineering and biomedical marketing communications, and a bachelor of science degree from UC San Diego.

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