CAP question

In building automation systems, which of the following is not considered to be an example of a unit-level controller?
A. fan coil unit
B. unitary zone control
C. pulse width modulation output
D. hotel room controller
CAP answer  
The answer is C, “ pulse width modulation output.” Fan coil units, unitary zone controllers, and hotel room controllers all fit the definition of a unit-level controller, or application-specific controller. Typically, an application-specific controller has a built-in, “canned” program that is designed to control a specific piece of equipment.

Pulse width modulation is a method for controlling the output to a final control element and represents an I/O strategy, not a unit-level controller.
Reference: Sands, Nicholas P. & Verhappen, Ian, A Guide to the Automation Body of Knowledge, Third Edition, ISA Press, 2019.


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