To Network or Not to Network? That is the Question

look like as if its selling some product.

no news in it.

I can't see the advantage with making networked the legacy systems, one would have to buy lots of converters/interfaces and additional software overhead.

It would be more cost effective, re-projecting the whole system with brand new instruments while thinking of system reliability together.

A minor problem with your question. While we all know that the various bus sytems now available are rapid, aren't they all technically still a serial system (i.e. all data flows on one set of conductors). Of the majors I have used, Ethernet, Foundation Fieldbus, Profibus, DeviceNet, Remote I/O, all are 2 wire systems save the DeviceNet which has 4, but 2 are for power not communication. None are a parallel system.

If I understand the concept you are presenting in "hybrid systems", this hybrid approach is being used even on many new systems in the pharmaceutical industry for remote mounted process skids. A network connects the skid processor to the plant distributed control system, but the skid itself is automated more typical of a 1980's era automated system. Few networks end up on these. A few majors have gone to FF through the heirarchy down to the instruments on the local process skid level, but as stated earlier, many end the network at the skid level and connect the skid instrumentation to a local processor with individual cables from each of the instruments to the processor - no network routing with local drop offs. It makes for much easier check out of the process skid at the skid manufacturer, since no network connection is required to operate it. Just fire up the processor and put the instruments through their required testing. Conversly, the system with the network through to the skid level instruments makes for easier quicker construction at the skid manufacturer, as a local processor is usually omitted from the skid package and becomes a plant mounted item serving many local skids, leaving only a "glorified junction box" to build for the skid.