Re: [foxboro] CP-60 Fieldbus Communication Errors
- From: "Corey R Clingo" <clingoc@xxxxxxxxxxxxx>
- To: foxboro@xxxxxxxxxxxxx
- Date: Wed, 23 Mar 2005 13:47:30 -0600
>>Has the installation of this kit and Rev M. CP60's completely
>>resolved the issue for those of you that have already implemented it, or
do
>>you just see reduced number of fieldbus communication errors?
The number of PIO error events and the number of FBMs involved in each
have both been reduced dramatically. We now see PIO errors on one or two
FBMs every couple weeks or so over 4 CP60s. I'm waiting to see if the
last two changes we made will eliminate these entirely,
>>I can imagine that the tenuous
>>elevator connections on the top of the CP-60's are also serious
contributors
>>to noise induction onto the fieldbus and dictate the use of the three
chokes
>>on the small white coax cables coming from the top of the CP-60's. Now
I
>>understand why the ZCP270's use direct fiber connections for their
fieldbus.
<snip>
>>This seems to be a clear case of poor initial design considerations
>>for the CP-60 fieldbus that now needs to be rectified by an external,
and
>>might I say, clumsy retrofit kit that many people, including many
Foxboro
>>field service reps aren't aware of or are not talking about.
I suspect it's more than just your imagination. The reason I thought all
this was hogwash is that I have dealt with Ethernet systems based on
thinnet cable in the past, as well as other coaxial-cable-based networks
(early Ethernet, brand H LCN, GE Mark V ARCnet). They were undoubtedly
sensitive to physical cable problems, but noise was never an issue in my
experience. I too suspect that the migration to direct fiber connections
in the xCP270s is a tacit admission of problems with the coaxial fieldbus.
While the retrofit kit is an inelegant fix, it does largely solve the
problem. And I don't expect the CP60 to be redesigned at this point, so
I'll take the kit over nothing. Too bad there aren't kits for making the
legacy nodebus redundant _and_ isolated, using Unix time as it was
intended, etc. (sorry, but like Duc, I couldn't resist :).
Corey Clingo
BASF Corp.
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