This automation industry quiz question comes from the ISA Certified Automation Professional (CAP) 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 more information about the CAP program.
A Markov model is used to determine successful system operation as a function of operating time interval. The resulting computation indicates system:
a) mission time
b) steady-state availability
d) probability of success
e) none of the above
Click Here to Reveal the Answer
Systems that exhibit a Markov property are ones in which the future does not depend on the past. Therefore, instantaneous availability will vary during the operating time interval, due to changes in failure probabilities and repair situations.
Availability is often calculated as an average over a long operating time interval. The result indicates that availability reaches a “steady state” after some period of time.
The correct answer is B, “steady-state availability.”
Reference: Nicholas Sands, P.E., CAP and Ian Verhappen, P.Eng., CAP., A Guide to the Automation Body of Knowledge. To read a brief Q&A with the authors, plus download a free 116-page excerpt from the book, click this link.