Use this section during the final days before an interview. Cover the answer with your hand, answer in one or two sentences, then compare your response with the concise reference answer.
1. What does NO mean on a schematic?
Normally open in the device’s defined normal state.
2. What does NC mean?
Normally closed in the device’s defined normal state.
3. What is an overload?
A sustained current/load condition above the intended operating level; motor overload protection is different from short-circuit protection.
4. What is a permissive?
A condition that must be satisfied before an action is allowed.
5. What is an interlock?
A control that prevents incompatible, unsafe, or undesired states.
6. What is a seal-in circuit?
A circuit that uses an auxiliary contact or logic to keep a command active after a momentary start signal is released.
7. What is a dry contact?
An isolated contact that does not inherently supply voltage; the external circuit provides the electrical potential.
8. What is a common wire in 24 V DC I/O?
The shared reference/return or supply connection used by a group of I/O points, depending on input/output design.
9. What is a relay used for?
Electrical isolation, logic, signal switching, or controlling a load with another circuit.
10. What is a solenoid?
An electromagnetic actuator that converts electrical energy into mechanical movement, often to shift a valve.
11. What is a limit switch?
A mechanically actuated position switch used to indicate or control movement limits.
12. What is a proximity sensor?
A non-contact sensor that detects a nearby target using an electrical or optical principle.
13. What is hysteresis in a sensor or control?
A difference between the switching point in one direction and the reset point in the opposite direction, used to prevent chatter.
14. What is debounce or input filtering?
A time or logic filter used to reject very brief signal changes or contact bounce.
15. What is a watchdog fault?
A fault indicating a controller/task/system did not complete required execution or communication within an expected time.
16. What is a fieldbus?
A digital industrial communication network used to connect controllers, I/O, drives, instruments, or other devices.
17. Why terminate certain communication networks?
To match the cable/network impedance and reduce signal reflections according to that network design.
18. What is an IP address?
A logical address used for communication on IP networks.
19. What is a duplicate IP address?
Two devices configured with the same address, which can cause communication conflicts.
20. What is a managed industrial Ethernet switch?
A switch that provides configurable features and diagnostics such as VLANs, redundancy, port statistics, or monitoring.
21. What is an encoder index pulse?
A reference pulse, often once per revolution, used for homing or position reference in some encoder systems.
22. What is a VFD DC bus?
The internal DC link between the rectifier/input stage and inverter/output stage.
23. What is regenerative energy?
Energy returned from a decelerating or overhauling motor/load toward the drive.
24. What is a braking resistor?
A resistor used by a compatible drive braking circuit to dissipate regenerative energy as heat.
25. What is a soft starter?
A device that controls voltage during motor starting/stopping to reduce electrical and mechanical stress; it does not normally provide continuous variable-speed control like a VFD.
26. What is a motor starter?
A combination of switching and protection components used to start, stop, and protect a motor.
27. What is inrush current?
The temporary high current that can occur when equipment is energized or motors start.
28. What is power factor?
The ratio of real power to apparent power in AC systems, influenced by phase relationship and waveform.
29. What is phase imbalance?
Unequal voltage or current among phases; it can overheat three-phase equipment.
30. What is a ground/earth conductor for?
A protective path and bonding system used to control touch voltage and support fault clearing according to the electrical system design.
31. What is a ferrule?
A crimped sleeve used on stranded wire ends for reliable termination in suitable terminals.
32. Why torque electrical terminals?
Correct torque helps achieve reliable contact pressure without damaging the conductor or terminal.
33. What is contact resistance?
Electrical resistance at a connection or contact interface; excessive resistance creates voltage drop and heat.
34. What is a thermal camera good at finding?
Abnormal heat patterns that may indicate high-resistance electrical connections, friction, overload, or insulation/process issues.
35. What is cavitation?
Formation and collapse of vapor bubbles due to low local pressure in a liquid system.
36. What is NPSH?
Net positive suction head; a pump application concept used to assess suction conditions and cavitation margin.
37. What is hydraulic pressure?
Force per unit area in the fluid; pressure develops in response to resistance/load in a closed hydraulic circuit.
38. What is hydraulic flow?
Volume of fluid moved per unit time; flow strongly influences actuator speed.
39. What determines cylinder force?
Pressure acting on effective piston area, minus losses and opposing forces.
40. What determines cylinder speed?
Primarily flow rate divided by effective piston area, subject to leakage and load effects.
41. What is a check valve?
A valve that allows flow primarily in one direction.
42. What is a flow-control valve?
A valve used to regulate fluid flow and therefore actuator speed or process flow.
43. What is a pressure-reducing valve?
A valve that maintains a lower controlled downstream pressure in an appropriate circuit.
44. What is a counterbalance valve?
A load-control valve used to prevent uncontrolled movement of an overrunning or gravity-loaded actuator in suitable hydraulic circuits.
45. What is an accumulator?
A hydraulic energy-storage device that stores pressurized fluid, often using a gas precharge; it is a stored-energy hazard.
46. What is a pneumatic regulator?
A device that maintains a selected downstream air pressure within its operating range.
47. What is a quick-exhaust valve?
A pneumatic valve that exhausts air near an actuator to increase speed in suitable applications.
48. What is a reed switch on a cylinder?
A magnetic position switch activated by a magnet in the piston.
49. What is backlash?
Clearance or lost motion between mating mechanical parts.
50. What is runout?
Variation of a rotating surface or axis from its ideal geometry, measured relative to a reference.
51. What is a dial indicator used for?
Precision measurement of small displacement, runout, alignment, or movement.
52. What is a torque wrench used for?
Applying a specified fastener torque rather than tightening by feel.
53. What is threadlocker?
An adhesive compound used on threaded fasteners to resist loosening and/or seal threads depending on product.
54. What is anti-seize?
A compound used on appropriate threaded or fitted surfaces to reduce galling/corrosion and aid later disassembly; torque values may need adjustment per procedure.
55. What is a keyway?
A slot in a shaft/hub used with a key to transmit torque and locate components.
56. What is a coupling?
A component that connects rotating shafts and may accommodate limited misalignment depending on design.
57. What is a mechanical seal?
A sealing arrangement used around a rotating shaft, commonly in pumps, to limit fluid leakage.
58. What is soft foot?
A mounting condition where one or more machine feet do not sit correctly on the base, causing frame distortion when tightened.
59. What is resonance?
Large vibration response when excitation is near a natural frequency of the system.
60. What is imbalance?
Uneven mass distribution around a rotating axis, creating centrifugal force and vibration.
61. What is misalignment?
Incorrect relative shaft or component geometry that creates extra loads and wear.
62. What is lubrication starvation?
Insufficient lubricant reaching the required contact surfaces.
63. What is overgreasing?
Applying excessive grease, which can cause churning, heat, and seal problems in some bearings.
64. What is contamination control?
Practices that prevent dirt, water, fibers, metal, and other contaminants from entering sensitive systems.
65. What is PM?
Preventive maintenance.
66. What is PdM?
Predictive or condition-based maintenance, depending on organizational terminology.
67. What is RCA?
Root cause analysis.
68. What is CMMS?
Computerized maintenance management system.
69. What is MTBF?
Mean time between failures, commonly used for repairable assets.
70. What is MTTR?
Mean time to repair or restore, depending on the organization’s definition.
71. What is OEE?
Overall equipment effectiveness, commonly combining availability, performance, and quality.
72. What is a critical spare?
A spare whose absence creates unacceptable operational or risk consequences if the associated component fails.
73. What is a temporary repair?
A controlled short-term measure that requires documentation, limits, ownership, and a permanent follow-up.
74. What is change control?
A process for reviewing, approving, documenting, testing, and communicating modifications to equipment or software.
75. What is verification after maintenance?
Testing that the repaired equipment, protections, interlocks, and intended function are correct before handover.