1. What is a PLC and why is it used in industry?
Practice note: answer in 30–90 seconds. If the question is troubleshooting-based, begin with the expected behavior and the first evidence you would collect. If the question is safety-related, state the boundary clearly before describing technical checks.
2. Explain the PLC scan cycle.
Practice note: answer in 30–90 seconds. If the question is troubleshooting-based, begin with the expected behavior and the first evidence you would collect. If the question is safety-related, state the boundary clearly before describing technical checks.
3. What is the difference between a digital input and a digital output?
Practice note: answer in 30–90 seconds. If the question is troubleshooting-based, begin with the expected behavior and the first evidence you would collect. If the question is safety-related, state the boundary clearly before describing technical checks.
4. How would you troubleshoot a PLC input that does not turn on?
Practice note: answer in 30–90 seconds. If the question is troubleshooting-based, begin with the expected behavior and the first evidence you would collect. If the question is safety-related, state the boundary clearly before describing technical checks.
5. How would you troubleshoot a PLC output that is on in logic but the load is off?
Practice note: answer in 30–90 seconds. If the question is troubleshooting-based, begin with the expected behavior and the first evidence you would collect. If the question is safety-related, state the boundary clearly before describing technical checks.
6. What is a seal-in circuit?
Practice note: answer in 30–90 seconds. If the question is troubleshooting-based, begin with the expected behavior and the first evidence you would collect. If the question is safety-related, state the boundary clearly before describing technical checks.
7. What is the difference between a contactor and a relay?
Practice note: answer in 30–90 seconds. If the question is troubleshooting-based, begin with the expected behavior and the first evidence you would collect. If the question is safety-related, state the boundary clearly before describing technical checks.
8. What does an overload relay protect against?
Practice note: answer in 30–90 seconds. If the question is troubleshooting-based, begin with the expected behavior and the first evidence you would collect. If the question is safety-related, state the boundary clearly before describing technical checks.
9. Why can a motor overload trip even when no breaker trips?
Practice note: answer in 30–90 seconds. If the question is troubleshooting-based, begin with the expected behavior and the first evidence you would collect. If the question is safety-related, state the boundary clearly before describing technical checks.
10. What is the difference between command and feedback?
Practice note: answer in 30–90 seconds. If the question is troubleshooting-based, begin with the expected behavior and the first evidence you would collect. If the question is safety-related, state the boundary clearly before describing technical checks.
11. What are permissives and interlocks?
Practice note: answer in 30–90 seconds. If the question is troubleshooting-based, begin with the expected behavior and the first evidence you would collect. If the question is safety-related, state the boundary clearly before describing technical checks.
12. What is a one-shot and when would you use it?
Practice note: answer in 30–90 seconds. If the question is troubleshooting-based, begin with the expected behavior and the first evidence you would collect. If the question is safety-related, state the boundary clearly before describing technical checks.
13. How do you prevent a counter from incrementing every PLC scan?
Practice note: answer in 30–90 seconds. If the question is troubleshooting-based, begin with the expected behavior and the first evidence you would collect. If the question is safety-related, state the boundary clearly before describing technical checks.
14. What is the difference between retentive and non-retentive behavior?
Practice note: answer in 30–90 seconds. If the question is troubleshooting-based, begin with the expected behavior and the first evidence you would collect. If the question is safety-related, state the boundary clearly before describing technical checks.
15. How would you structure a simple machine sequence?
Practice note: answer in 30–90 seconds. If the question is troubleshooting-based, begin with the expected behavior and the first evidence you would collect. If the question is safety-related, state the boundary clearly before describing technical checks.
16. What is a state machine?
Practice note: answer in 30–90 seconds. If the question is troubleshooting-based, begin with the expected behavior and the first evidence you would collect. If the question is safety-related, state the boundary clearly before describing technical checks.
17. Why is 4–20 mA commonly used?
Practice note: answer in 30–90 seconds. If the question is troubleshooting-based, begin with the expected behavior and the first evidence you would collect. If the question is safety-related, state the boundary clearly before describing technical checks.
18. How would you scale a 4–20 mA signal to engineering units?
Practice note: answer in 30–90 seconds. If the question is troubleshooting-based, begin with the expected behavior and the first evidence you would collect. If the question is safety-related, state the boundary clearly before describing technical checks.
19. What would you check if an analog input reads zero?
Practice note: answer in 30–90 seconds. If the question is troubleshooting-based, begin with the expected behavior and the first evidence you would collect. If the question is safety-related, state the boundary clearly before describing technical checks.
20. What is the difference between inductive and photoelectric sensing?
Practice note: answer in 30–90 seconds. If the question is troubleshooting-based, begin with the expected behavior and the first evidence you would collect. If the question is safety-related, state the boundary clearly before describing technical checks.
21. What causes an intermittent sensor fault?
Practice note: answer in 30–90 seconds. If the question is troubleshooting-based, begin with the expected behavior and the first evidence you would collect. If the question is safety-related, state the boundary clearly before describing technical checks.
22. How do you trace a signal on an electrical schematic?
Practice note: answer in 30–90 seconds. If the question is troubleshooting-based, begin with the expected behavior and the first evidence you would collect. If the question is safety-related, state the boundary clearly before describing technical checks.
23. What do you do when the schematic does not match the machine?
Practice note: answer in 30–90 seconds. If the question is troubleshooting-based, begin with the expected behavior and the first evidence you would collect. If the question is safety-related, state the boundary clearly before describing technical checks.
24. What information do you need from a motor nameplate?
Practice note: answer in 30–90 seconds. If the question is troubleshooting-based, begin with the expected behavior and the first evidence you would collect. If the question is safety-related, state the boundary clearly before describing technical checks.
25. What is a VFD?
Practice note: answer in 30–90 seconds. If the question is troubleshooting-based, begin with the expected behavior and the first evidence you would collect. If the question is safety-related, state the boundary clearly before describing technical checks.
26. What could prevent a VFD-controlled motor from starting even when the PLC run command is true?
Practice note: answer in 30–90 seconds. If the question is troubleshooting-based, begin with the expected behavior and the first evidence you would collect. If the question is safety-related, state the boundary clearly before describing technical checks.
27. What information do you collect before resetting a repeated drive fault?
Practice note: answer in 30–90 seconds. If the question is troubleshooting-based, begin with the expected behavior and the first evidence you would collect. If the question is safety-related, state the boundary clearly before describing technical checks.
28. What is local versus remote drive control?
Practice note: answer in 30–90 seconds. If the question is troubleshooting-based, begin with the expected behavior and the first evidence you would collect. If the question is safety-related, state the boundary clearly before describing technical checks.
29. How would you troubleshoot an HMI button that does nothing?
Practice note: answer in 30–90 seconds. If the question is troubleshooting-based, begin with the expected behavior and the first evidence you would collect. If the question is safety-related, state the boundary clearly before describing technical checks.
30. What makes a good alarm message?
Practice note: answer in 30–90 seconds. If the question is troubleshooting-based, begin with the expected behavior and the first evidence you would collect. If the question is safety-related, state the boundary clearly before describing technical checks.
31. What is an IP address?
Practice note: answer in 30–90 seconds. If the question is troubleshooting-based, begin with the expected behavior and the first evidence you would collect. If the question is safety-related, state the boundary clearly before describing technical checks.
32. What does a subnet mask do?
Practice note: answer in 30–90 seconds. If the question is troubleshooting-based, begin with the expected behavior and the first evidence you would collect. If the question is safety-related, state the boundary clearly before describing technical checks.
33. How would you troubleshoot a remote I/O device that is offline?
Practice note: answer in 30–90 seconds. If the question is troubleshooting-based, begin with the expected behavior and the first evidence you would collect. If the question is safety-related, state the boundary clearly before describing technical checks.
34. Why can a network fault appear intermittent?
Practice note: answer in 30–90 seconds. If the question is troubleshooting-based, begin with the expected behavior and the first evidence you would collect. If the question is safety-related, state the boundary clearly before describing technical checks.
35. What is the purpose of an industrial Ethernet switch?
Practice note: answer in 30–90 seconds. If the question is troubleshooting-based, begin with the expected behavior and the first evidence you would collect. If the question is safety-related, state the boundary clearly before describing technical checks.
36. What is the difference between a standard PLC and a safety PLC?
Practice note: answer in 30–90 seconds. If the question is troubleshooting-based, begin with the expected behavior and the first evidence you would collect. If the question is safety-related, state the boundary clearly before describing technical checks.
37. What would you do if someone asks you to bypass a guard switch?
Practice note: answer in 30–90 seconds. If the question is troubleshooting-based, begin with the expected behavior and the first evidence you would collect. If the question is safety-related, state the boundary clearly before describing technical checks.
38. What steps do you take before making an online edit?
Practice note: answer in 30–90 seconds. If the question is troubleshooting-based, begin with the expected behavior and the first evidence you would collect. If the question is safety-related, state the boundary clearly before describing technical checks.
39. Why are PLC forces risky?
Practice note: answer in 30–90 seconds. If the question is troubleshooting-based, begin with the expected behavior and the first evidence you would collect. If the question is safety-related, state the boundary clearly before describing technical checks.
40. How do you make sure you are not downloading an old program over a newer one?
Practice note: answer in 30–90 seconds. If the question is troubleshooting-based, begin with the expected behavior and the first evidence you would collect. If the question is safety-related, state the boundary clearly before describing technical checks.
41. What is your troubleshooting process when a machine will not start?
Practice note: answer in 30–90 seconds. If the question is troubleshooting-based, begin with the expected behavior and the first evidence you would collect. If the question is safety-related, state the boundary clearly before describing technical checks.
42. How do you determine whether a problem is electrical, mechanical, or software?
Practice note: answer in 30–90 seconds. If the question is troubleshooting-based, begin with the expected behavior and the first evidence you would collect. If the question is safety-related, state the boundary clearly before describing technical checks.
43. What is the first missing condition method?
Practice note: answer in 30–90 seconds. If the question is troubleshooting-based, begin with the expected behavior and the first evidence you would collect. If the question is safety-related, state the boundary clearly before describing technical checks.
44. How do you verify that a repair is complete?
Practice note: answer in 30–90 seconds. If the question is troubleshooting-based, begin with the expected behavior and the first evidence you would collect. If the question is safety-related, state the boundary clearly before describing technical checks.
45. How do you document a PLC change?
Practice note: answer in 30–90 seconds. If the question is troubleshooting-based, begin with the expected behavior and the first evidence you would collect. If the question is safety-related, state the boundary clearly before describing technical checks.
46. What should be in a PLC backup set?
Practice note: answer in 30–90 seconds. If the question is troubleshooting-based, begin with the expected behavior and the first evidence you would collect. If the question is safety-related, state the boundary clearly before describing technical checks.
47. What is the difference between simulation and real hardware training?
Practice note: answer in 30–90 seconds. If the question is troubleshooting-based, begin with the expected behavior and the first evidence you would collect. If the question is safety-related, state the boundary clearly before describing technical checks.
48. Explain one PLC project you built from start to finish.
Practice note: answer in 30–90 seconds. If the question is troubleshooting-based, begin with the expected behavior and the first evidence you would collect. If the question is safety-related, state the boundary clearly before describing technical checks.
49. What was one fault you intentionally created in a training project and how did you diagnose it?
Practice note: answer in 30–90 seconds. If the question is troubleshooting-based, begin with the expected behavior and the first evidence you would collect. If the question is safety-related, state the boundary clearly before describing technical checks.
50. Which controls topic are you currently improving and why?
Practice note: answer in 30–90 seconds. If the question is troubleshooting-based, begin with the expected behavior and the first evidence you would collect. If the question is safety-related, state the boundary clearly before describing technical checks.