AutoQuiz: How to Measure and Compensate for Disturbances to Prevent Set Point Deviance

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 I, Feasibility Study: Identify scope and justify the automation project.

Which of the following control strategies works to measure disturbances and compensate for them before they cause the controlled variable to deviate from the set point?

a) feedforward
b) feedback
c) cascade
d) open loop
e) none of the above

   

Click Here to Reveal the Answer

The objective of feedforward control is to measure disturbances and compensate for them before the controlled variable deviates from set point.

Feedback control can compensate for a disturbance only after the control variable has deviated from set point.

Cascade is a form of feedback control.

Open loop is not a control strategy.

The best answer is A, feedforward.

Reference: Carlos A. Smith and Armando B. Corripio; Principles and Practices of Automatic Process Control.

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