Throughout the industrial process control industries Safety Instrument System to be high profile. Some companies receive a performance-based standards such as ANSI / ISA 84.01, IEC 61508 and IEC 61 511 is here to stay and appropriateness are not optional. More and more instrumentation manufacturers have recognized that interest continued to increase this market has shown in bringing their plans into line with standards. They have responded by introducing a variety of products that "fit for use" in Safety Instrumentation System (SIS). Some products are sensors, transmitters, valves and valve positioners and various logic solvers.
Most users have little concern about being able to choose the sensor transmitter, directly or valve positioned, but when it comes to choosing from a wide range of logic solvers, they often do not know how to make the right decision. The problem is obvious when you consider the various options for Logic Solvers that range from relatively simple travel alarm architecture up through a variety of safety PLCs offered by about twenty different manufacturers. This PLC architecture includes a simple scale of one-out-of-one architecture up through triple and quadruple redundant systems with different degrees of self-diagnosis.