Mixing fieldbuses

[dewey320]

Robin,

Thanks for the reply, I did not intend for my previous post to be inflammatory. I do still however stand behind what I said.

We, as systems vendors, need to be painfully aware of our customers objectives when they install systems. I might be going out on a limb here but having worked at end users companies in the past let me take a shot at it. My objective when installing a new control system would be to create a system that does what I need to operate the plant efficiently while coming in on budget and schedule. My objective is most certainly NOT to try to use one bus technology wherever possible. Bus technologies or any other technology for that matter are a means to an end. No more.

you said;

So my personal belief, is that based on current technologies and past history one should not aim to have a multiple bus system. In my opinion they can be beneficial in specific circumstances, but you should aim to have one primary bus technology and then where and when that technology does not deliver weigh up the benefits and disadvantages of implementing further buses on the same system.

But the fact remains that FF does not measure up for every single type of device in the plant. I have to agree with your statement, so long as you are willing to admit that if your plant has any motors, drives, or PLC's, then you may want to take a look at DeviceNet or Profibus DP.

I have to scratch my head though when you say;

But, yes we (smar) and many others have done it, our systems do support multiple bus technologies, seamlessly (as the sales men say). But that does not mean we recommend it, nor does it mean you get the full set of features and benefits offered by every bus, or even any of the buses in many cases!

Why bother building the "seamless" multiple bus capability in a system if you don't recommend using it? Surely that is an advantage you must have to offer customers that some of your competitors do not. No?

Finally;

My personal recommendation to anybody trying to make this assessment would be to seek advice from more than one supplier (even if you feel you are already committed to a supplier) and get as much end user feedback as possible.

I absolutely agree. It doesn't take a lot of research (hands on, not internet banter like we post here) to understand the differences between functionality offered in different systems.


rgds,

dewey