ISA CAP Advanced Techniques & Methods 3

Question 1

In multivariable control, the Relative Gain Array (RGA) is used to:

Accepted Answer

Assess loop interaction and select input-output pairings

Answer

The RGA quantifies steady-state interaction between manipulated and controlled variables, guiding optimal pairing to minimize loop coupling.

Question 2

A decoupler in a multivariable control system is designed to:

Accepted Answer

Cancel the cross-coupling effects between interacting loops

Answer

A decoupler adds compensating signals so that a change in one manipulated variable does not affect the other controlled variables.

Question 3

What does the concept of 'inferential control' (soft sensing) involve?

Accepted Answer

Estimating an unmeasured controlled variable from related measured variables

Answer

Inferential control estimates a key quality variable (e.g., composition) that cannot be measured directly or in real time, using a mathematical model and available sensor readings.

Question 4

In statistical process control (SPC), a Western Electric Rule violation occurs when:

Accepted Answer

A specific non-random pattern is detected on a control chart

Answer

Western Electric Rules define patterns—such as runs, trends, or clusters near control limits—that indicate a non-random (assignable) cause is present.

Question 5

Process capability index Cpk differs from Cp in that Cpk:

Accepted Answer

Accounts for the centering of the process relative to specifications

Answer

Cpk incorporates the process mean's distance from the nearest specification limit, penalizing processes that are not centered within the spec window.

(ISA CAP) ISA Certified Automation Professional Practice Test

(ISA CAP) ISA Certified Automation Professional Practice Test

ISA CAP Advanced Techniques & Methods 3