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AutoQuiz: How Do You Compensate for Thermowell Lag Time?

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

Today's automation industry quiz question comes from the ISA Certified Automation Professional certification program. ISA CAP certification provides a non-biased, third-party, objective assessment and confirmation of an automation professional's skills. The CAP exam is focused on direction, definition, design, development/application, deployment, documentation, and support of systems, software, and equipment used in control systems, manufacturing information systems, systems integration, and operational consulting. Click this link for information about the CAP program. The following question comes from the CAP study guide, Performance Domain V, Deployment.

autoquiz-20161223-compensate-thermowell-lag-time

An increase in which setting can compensate for a thermowell lag time?

a) rate time
b) reset time
c) gain
d) filter time
e) none of the above

Thermowell and temperature processes have multiple interacting thermal lags. Rate time cancels a secondary thermal lag that can improve control in a slow temperature process without A/D chatter. Reset time adds another lag that further increases the apparent dead time from multiple lags. A large thermowell lag reduces the allowable gain. A process variable filter adds another lag that further increases the apparent dead time from multiple lags.

The correct answer is A, rate time.

Reference: Greg McMillan, Good Tuning: A Pocket Guide.

Joel Don
Joel Don
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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