Definition:
A Programmable Electronic System (PES) refers to any programmable device, such as a PLC or DCS, used to perform safety or control functions. This is opposite of something that is hardwired or “dumb” like a very basic pressure switch or a relay (or even complex relay logic).
Note that relay logic, in the most basic sense, is NOT a PES. It is a number of “dumb” relays setup to create logic. However, relay logic is less favorable over time, so a SIS will most likely have a PES as part of it.
Note that a SIL 1 SIF with no PES (meaning basic instruments, valves, and relay logic) is perfectly fine. But it would be harder to implement a SIL 3 SIF without a PES with all the other requirements imposed.
Key Points:
- Includes safety PLCs for SIL-rated applications.
- Must meet applicable functional safety standards for SIS use.
- An ASIC (application specific integrated circuit) would not be a PES. A FPGA (field programmable gate array) most likely would be.
Example:
The Schneider Electric Tricon (formerly Triconex) safety PLC is a PES certified for SIL 3 applications.
See Also: logic solver, relay logic, E/E/PE
Cited Source:
- IEC 61508-4:2010
- IEC 61511-1:2016, Clause 3.2.54