AutoQuiz is edited by Joel Don, ISA’s community manager.

Today’s 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 information about the CCST program. This question is from the Level III study guide, Domain 2, Loop checking. Level III represents a professional who has a 13-year total of education, training, and/or experience.


The continuous sequence of steps or “operating cycle” performed by a PLC processor is known as:

a) updating
b) scanning
c) polling
d) rectifying
e) none of the above


Click Here to Reveal the Answer

While the PLC may in fact update values, poll devices, and rectify aspects of the process in response to data it encounters during its routine, the best term for this continuous sequence is scanning.

The correct answers is B, scanning.

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