SACA Programmable Logic Controllers 5

Question 1

Which PLC scan phase occurs AFTER the program logic is executed?

Accepted Answer

Output image table update and write to outputs

Answer

After program logic execution, the PLC writes the output image table values to the physical output modules to update field devices.

Question 2

What is the function of a PLC's retentive coil (or latching coil)?

Accepted Answer

It maintains its state even when its enabling condition goes false

Answer

A retentive (latching) coil maintains its energized state even after the enabling rung condition goes false, until explicitly unlatched.

Question 3

In an Allen-Bradley ControlLogix PLC, what does the tag-based addressing system offer compared to traditional register-based addressing?

Accepted Answer

Descriptive named variables that improve program readability and maintainability

Answer

Tag-based addressing uses descriptive named variables instead of cryptic register numbers, greatly improving program readability and long-term maintainability.

Question 4

What is the purpose of the 'force' function available in most PLC programming software?

Accepted Answer

To override normal program logic and manually set an I/O point to a desired state for testing

Answer

The force function allows technicians to manually override I/O points to a specific state for troubleshooting, bypassing normal program logic.

Question 5

A CTD (Count Down) instruction in a PLC has a preset of 10 and an accumulated value of 3. How many more count pulses are needed to set the Done bit?

Accepted Answer

3

Answer

A CTD instruction counts down from the accumulated value; the Done bit sets when accumulated reaches zero, so 3 more pulses are needed.

SACA - Smart Automation Certification Alliance Practice Test

SACA - Smart Automation Certification Alliance Practice Test

SACA Programmable Logic Controllers 5