[foxboro] FBM214 incorrect input readings

Hi list,

Forgive me if this sounds like a rant, but I'm supposed to be on vacation, 
and I find out today that I potentially have 1/4 of the plant's analog 
inputs reading erroneously...


We were troubleshooting a problem with redundant level transmitters today 
where one was reading about 20% higher than the other.  Both the inputs 
are on separate FBM214s, the points are in current mode (PV=CURRENT, 
DVOPTS on the ECB=NOFAIL).  I called TAC and they responded that there had 
been some reports of this behavior, that two CARs have been filed (more on 
that later), that the problem is hardware- and software-related, that they 
have been working on a fix for 3-4 weeks and that "they hoped" it would be 
out in another 1-2 weeks.  They informed me that in the the instances 
reported, they think the problem was initiated by either a mix 
non-FBM-powered input, or an input driving very high (close to 30 mA).  I 
don't believe either happened in my case; I can vouch for the fact that 
all inputs are FBM-powered, but as for the driving high part, all I have 
to go on are the transmitter specs.


Anyway, they tell me that in the cases reported, the result was that *all* 
the channels on the FBM exhibited some kind of offset, though not the same 
on each channel.  The only known workaround at this time is to reboot the 
FBM.  And now, to get an idea of the scope of the problem here, I have to 
get into IFDC or build a block that reads the HART PV, and compare that 
value with the current.  Just exactly what I had in mind for my vacation.


So I have a couple questions:


1) Has anyone else seen this, and if so, what have you done about it?


2) Why, oh why, am I having to find this out for myself?  The CAR numbers 
the TAC guy referenced aren't even in the database.  And what level of 
system malfunction does it take for Invensys to give its customers a 
heads-up?  I ask this in all seriousness, as I have asked our local reps 
before and have not gotten an answer.  In my opinion, an undetectable bias 
error in all channels on an input card meets the "hmm, err, umm, I guess 
we better tell them" criterion.


Off to file another CAR,
Corey Clingo
BASF Corp.


P.S. Merry Christmas and Happy Holidays.

 
 
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