Logic solver fundamentals

SIF is defined as a collection of sensors, logic solver and final elements that protect against a particular hazard. There may be multiple sensors and final elements for each safety function as shown in Figure 3.8. The fundamental work process for SIL evaluation includes the following. 

From Chapter VII readers may form an idea about what a safe PLC is and why it is necessary. In this clause short discussions will be presented on the internals of a safe PLC. It is needless to mention that there may be quite different configurations of safe PLCs from different manufacturers. Naturally, it is impossible to cover all these configurations within the limited space. Therefore discussions will be based on one internationally popular PLC in a generalized maimer to understand the fundamentals only (so that further discussions on logic solvers in Chapter IX will be easier). For details of PLCs and intelligent control systems readers may refer to [1]. 

There are a few good books on different topics, but it is fact there is no single book to cover both hazard analysis methods as well as detailed SIS. The chapters this book covers including risk assignment fundamentals, hazard analysis methods, SIL calculations to develop SIS, and effects of SIS on various components staring from sensors, fieldbus, logic solver, and final elements are really worth praising. The book is well balanced to cover basic mathematics as well as sector-wise industrial applications. 

Another fundamental difference between microprocessor-based systems and other logic solvers is as follows. 

---

See also in sourсe #XX -- [ , ]

---