July 2009
ISA Certified Automation Professional (CAP) program
Certified Automation Professionals (CAPs) are responsible for the direction, design, and deployment of systems and equipment for manufacturing and control systems.
The following question comes from the CAP study guide, Performance Domain IV, Development, Software development and coding
CAP question
The average person cannot respond to signals more frequent than one every:
A. 30 milliseconds
B. 80 milliseconds
C. 300 milliseconds
D. 800 milliseconds
CAP answer
The correct answer is C, 300 milliseconds.
The average person cannot process signals more frequent than one every 300 milliseconds, or about three signals per second. Therefore, for reliable regulation of events that are faster than three signals per second, a person should not act as the controller.
Reference: Donald A. Coggan, Fundamentals of Industrial Control: Practical Guides for Measurement and Control, 2nd edition; ISA Press, 2005
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What type of signal to use? Here are a couple simple rules:
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