Not sure if this helps but if mixed with 200 series FBM's, total number of
FBM's is important and will cause issues, think it depends more on CP
loading than number. We've also experienced a similar issue where a 200
series HDLC cable distance between base plates was causing A&B fieldbus
errors with both the 100 and 200 series FBM's. We eliminated the long
HDLC cable and the problem went away. Another trick was to add an
FCM100et in an open 200 series baseplate. In our case it helped but did
not solve the issues. It apparently has some sort of filter that helps
balance the A&B buses comm.
Brian
-----Original Message-----
From: foxboro-bounce@xxxxxxxxxxxxx [mailto:foxboro-bounce@xxxxxxxxxxxxx]
On Behalf Of John Pilman
Sent: Friday, September 30, 2016 12:10 PM
To: foxboro@xxxxxxxxxxxxx
Subject: [foxboro] Odd Fieldbus behavior
We recently found a Fieldbus which quits communicating for about 25
seconds each minute without generating a fieldbus error. Now we wonder if
this is normal behavior, or if there is some other explanation. We will be
trying to reproduce this behavior in the shop, but it may take some time
to set up that test. Have any of you seen this before?
We went to a customer's site to troubleshoot the fieldbus because there
are occasional fieldbus errors reported on the system monitor. This site
has a fault tolerant FCP270 pair and a number of Series 100 FBMs. They are
experiencing errors which appear on the system monitor as fieldbus B
failures approximately once per day. During the investigation, using an
oscilloscope, we observed that the activity on fieldbus A was stopping
approximately 25 seconds each minute. Fieldbus A does show some errors,
but far fewer than bus B.
Here is a still image of the oscilloscope trend of the voltage on both
busses (file size 225 KB).
https://drive.google.com/file/d/0B4-fZtD9qOhIQWVmYmlUalhjaEU/view?usp=shar
ing
This image clearly shows that one bus ceases activity. The time that the
red trace was idle was approximately 24 seconds.
Note: The Y scales (voltage) appear to have different ranges. That is
strictly an anomaly of the scope settings and the different probe
impedances at the time these measurements were taken. Please don't let
that interfere with your interpretation of the bus activity.
Here is a video of the oscilloscope with probes on both busses (97.3 MB).
https://drive.google.com/open?id=0B4-fZtD9qOhIMG9MdThXZUw4bW8
The scope's time stamp can be seen in the upper right hand corner. The
blue trace shows normal activity on bus B throughout the video. The red
trace, bus A, activity stops at 13:22:38 and resumes at 13:23:04.
Here is a video of the oscilloscope with a probe on A bus only (117 MB).
https://drive.google.com/open?id=0B4-fZtD9qOhIdW1Qc2pJNVllWWM
The bus activity is consistent until 11:01:01, when it stops. It then
resumes at 11:01:26.
Thanks
...John
_________________________________________________________________________
This mailing list is neither sponsored nor endorsed by Schneider Electric
(formerly The Foxboro Company). Use the info you obtain here at your own
risks. See the disclaimer at www.thecassandraproject.org/disclaimer.html
foxboro mailing list: //www.freelists.org/list/foxboro
to subscribe: mailto:foxboro-request@xxxxxxxxxxxxx?subject=join
to unsubscribe: mailto:foxboro-request@xxxxxxxxxxxxx?subject=leave
_________________________________________________________________________
This mailing list is neither sponsored nor endorsed by Schneider Electric
(formerly The Foxboro Company). Use the info you obtain here at your own
risks. See the disclaimer at www.thecassandraproject.org/disclaimer.html
foxboro mailing list: //www.freelists.org/list/foxboro
to subscribe: mailto:foxboro-request@xxxxxxxxxxxxx?subject=join
to unsubscribe: mailto:foxboro-request@xxxxxxxxxxxxx?subject=leave
