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 a PLC program, the continuous sequence of steps or “operating cycle” performed by a PLC processor is known as:
e) none of the above
Click Here to Reveal the Answer
Answer A is not the correct choice. Updating is a general term used for making updates to a software element value, program, or file.
Answer B, polling, is a method for sequentially observing each channel of a network or device in order to determine if it is ready to receive data or for requesting computer action..
Answer D, rectifying, refers to the conversion of alternating current to a relatively steady or pulsating direct current. There is most likely a rectifier circuit in the power supply that powers the PLC or PLC I/O.
The correct answer is C, scanning. The time it takes for the PLC to complete its scanning of all program steps in one “operating cycle” is called the “scan time.”