SIS VOTING LOGIC EXPLAINED: 1oo1 vs 1oo2 vs 2oo3 Selecting the right voting architecture is one of the most important decisions in Safety Instrumented Systems (SIS). Understanding the difference between: 1oo1 (One Out of One) 1oo2 (One Out of Two) 2oo3 (Two Out of Three) can significantly impact: Safety Integrity Level (SIL) performance Process availability Spurious trip frequency Proof test requirements Lifecycle maintenance costs Overall plant reliability There is no universal “best” voting logic. The correct selection depends on your process risk, availability requirements, maintenance strategy, and safety objectives. Remember: Don’t copy-paste voting logic. Engineer it. Save this infographic for future reference and share it with your colleagues working in Process Safety, Instrumentation, DCS, ESD, and Functional Safety. Which voting architecture is most commonly used in your plant? Let us know in the comments. Post navigation PLC Programming Challenge! CASCADE LOOP CONTROL
