PLC Cheat Sheet 2026

The 30 highest-yield PLC facts, distilled from real exam questions. Print it, save it as a PDF, or study it here — free, no sign-up.

1. A Safety PLC operating at SIL 2 typically requires which architecture to meet hardware fault tolerance requirements? → 1oo2 (one-out-of-two) redundancy
2. Which IEC standard covers functional safety of electrical, electronic, and programmable electronic safety-related systems? → IEC 61508
3. In a PLC-controlled application, why is a 'dynamic braking resistor' added to a VFD system? → To dissipate regenerative energy as heat when decelerating large inertial loads
4. What is the primary function of a PLC's CPU module? → Executing control programs and processing data
5. What is the first step in PLC troubleshooting? → Check power and status LEDs
6. A PLC sends a 4-20mA analog signal to a VFD for speed reference. What does 4mA typically represent? → Minimum speed (0% or stop)
7. In Programmable Logic Controller, which data management & integration approach is MOST effective for achieving long-term goals? → Strategic planning with measurable objectives and regular progress reviews
8. What is the MOST important skill for effective project planning & deployment in Programmable Logic Controller? → Clear communication and the ability to align team efforts with objectives
9. What does the RLO (Result of Logic Operation) represent in PLC logic? → The evaluated logic result
10. What is the primary function of an encoder in a servo motor system? → To provide real-time position and velocity feedback to the servo controller
11. What is the primary purpose of a Safety Instrumented Function (SIF)? → To bring a process to a safe state when a hazardous condition is detected
12. What is the typical voltage range for PLC digital input modules? → 24VDC (10-30V range)
13. Which communication protocol is commonly used for digital control between a PLC and a VFD in modern industrial systems? → EtherNet/IP or PROFIBUS
14. In Programmable Logic Controller, how does implementation & configuration contribute to professional credibility? → By demonstrating competence, maintaining standards, and delivering consistent results
15. What does 'electronic gearing' accomplish in a multi-axis PLC motion control system? → It synchronizes a slave axis to a master axis position or velocity at a programmable ratio
16. Which documentation & best practices practice is MOST critical for maintaining data integrity in Programmable Logic Controller? → Standardized input procedures with validation checks and regular audits
17. What does SIL stand for in the context of safety PLCs? → Safety Integrity Level
18. Which device helps isolate the PLC from high-voltage field equipment? → Isolator
19. Which device converts physical phenomena into electrical signals? → Sensor
20. What is the MOST effective way to stay current with developments in security & access control for Programmable Logic Controller? → Participating in professional development, industry events, and peer collaboration
21. What is the PRIMARY objective of implementation & configuration within the Programmable Logic Controller profession? → To ensure quality outcomes through standardized practices and continuous improvement
22. What does VFD stand for in the context of industrial motor control? → Variable Frequency Drive
23. What determines a PLC's scan time? → Program size and system configuration
24. In Programmable Logic Controller, which system architecture & design practice BEST ensures system reliability? → Implementing redundancy, regular testing, and documented recovery procedures
25. When troubleshooting system architecture & design issues in Programmable Logic Controller, what is the BEST approach? → Systematic diagnosis starting with the most likely causes and documenting steps
26. In functional safety terminology, what is a 'proof test'? → A periodic test of a safety function to detect dangerous undetected failures
27. What is the MOST important consideration when implementing system architecture & design solutions in Programmable Logic Controller? → Alignment with organizational needs and scalability requirements
28. What is a benefit of routine maintenance on PLC systems? → Prevents unexpected failures
29. Which communication standard is often used for PLC I/O expansion? → Ethernet/IP
30. In Programmable Logic Controller, which project planning & deployment approach is MOST effective for achieving long-term goals? → Strategic planning with measurable objectives and regular progress reviews