The post AutoQuiz: What Is the Continuous Sequence of Steps Performed by a PLC Processor? first appeared on the ISA Interchange blog site.
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.
a) updating
b) polling
c) scanning
d) rectifying
e) none of the above
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.”
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Source: ISA News
