Certified Automation Professional (CAP) program

• CAP

Summary

CAP question

The function of PID parameters is best described as

A. placing the system in a safe condition during process upsets.
B. optimizing a control loop.
C. ensuring that specified components are properly calibrated.
D. ensuring that specified components are properly installed.
 

CAP answer

The answer is B, “optimizing a control loop.” The parameters of a proportional, integral, derivative (PID) loop are typically called the “tuning parameters,” which include the gain, integral time, and derivative time. The purpose of these parameters is to provide a fast, robust response to swings in the process as well as to maintain a consistent response to normal process sensor noise. These parameters are adjusted through the tuning process and “good control” response, such as quarter-wave dampening, to provide optimal control.
 
The parameters of a PID control loop do not factor into the physical installation or calibration of the loop. These are handled via other processes and procedures. The PID loop does not evaluate or drive a process to a safe state upon a process upset, but can be directed by other programming to change mode, set point, or output.
 
Reference: Sands, Nicholas P. & Verhappen, Ian, A Guide to the Automation Body of Knowledge, Third Edition, ISA Press, 2019.
 

 

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