MKV <C> Arcnet Baud rate

G

Thread Starter

Greg Ponto

We are currently having an intermittant momentary loss of communications on one of our HMI servers (Cimplicity ver. 5.5). The comms are lost to all 4 MKVs on the Arcnet, but not to any of the 4 PLCs that use the Ethernet. The Diagnostic Couters / StageLink reconfiguration counters do not increase when this happens (approx. 3 times every 24 Hrs), so this kind of rules out a hardware issue.

My main question is, if the MKV <C> has a configurable baud rate and how do I find out what it is set for. The Cimplicity Workbench Equiptment / Ports / MKV / Baud rate is configurable and I am speculating that these should be matched. Also we did replace the PCI Arcnet card in the server in question although I am not a fan of random board swapping as a troubleshooting technique.

The network in question is 4 MKVs in TMR w/ 2 servers, 2 viewers and 1 PI Historian. The other server has rock solid comms. The difference between the 2 servers is their location on the network. The server w/ comms probs. is ~ 3/4 miles away from the other server connected by fiber via Modhubs. The network topology is similar to the example in the MKV Application manual (GEH-6195F) page 9-8.

Thanks for the help.

Greg Ponto
Lead Combustion Turbine Specialist
Elwood Operations
(815) 423-9883 x2232
Email: [email protected]
 
This author is unaware of a configurable ARCnet communication rate. This one of the problems with the CIMPLICITY application on a GE Mark V HMI--CIMPLICITY doesn't communicate with the ARCnet card. It has to communicate with the Mk V through CIMBRIDGE and TCI. And there are slew of configurations which don't apply to CIMPLICITY used on a GE Mark V HMI.

Since you have a MODHUB at each end of the fiber optic link, and this is the only difference between the two GE Mark V HMI Servers, this author's money would be on a problem with the fiber optic link or the MODHUBs.

The MODHUBs have at least one LED on them, and if memory serves correctly it flashes when there are reconfigurations. This author has seen LOTS of problems with fiber optic cables--especially when "break-out" boxes are not used at each end of the fiber optic link. The practice of connecting the fiber directly to the MODHUB usually leads to broken fibers. It's not clear if fiber problems causing reconfigurations would be caught by the Diagnostic Counters function.

The MODHUBS are usually fairly reliable, but nothing works forever....

This author has also seen LOTS of problems with field-terminated BNC connectors on coaxial cable cause similar problems. Also, many GE Mark V HMIs were shipped with two types of coaxial cables--one specifically for ARCnet and one for Ethernet (10BASE2). They have the same BNC connectors on each end, and the Ethernet cables work sometimes, then start having intermittent problems.... Make sure the coaxial cables are the right specification (per the Mk V Application Manual) AND that the BNC terminations are properly crimped and the shields are properly terminated under the crimp(s).

So, monitor the LEDs on the MODHUBs when you are experiencing the problems. And have someone come in to test the fiber optic cables.

Your site also probably has EX2000 exciter regulators, to which the StageLink is usually connected. This author has also seen problems with the comm card on the EX2000 AND with the BNC connectors on the coaxial cables connected to the EX2000 comm cards. But, if the problem is confined to the server connected to the StageLink via the MODHUBs, it's probably not this--unless the first termination after the MODHUB is at an EX2000....

Please write back and let us know what you find!

markvguy
 
G
Thanks for the troubleshooting tips. The problem turned out to be a degraded coax T connector on the HMI in question. That component was found when checking the seating and address dip switches on the PCI Arcnet card in the HMI. The condition of no "Stagelink" reconfigurations led us away from a Arcnet cable/connector/hardware problems, but as usual it wound up being hardware after all.

Greg Ponto
Lead Combustion Turbine Specialist
Elwood Operations
(815) 423-9883 x2232
Email: [email protected]
 
First of all: Thanks for the feedback--it's the most important part of this forum for everyone!

Second: Good catch!!!

Although the hardware is relatively usually trouble-free, it's also the easiest thing to check, and usually the first thing overlooked. Everybody, including this author, always assumes the worst when it comes to StageLink/ARCnet problems--probably because there isn't any method for troubleshooting StageLink ARCnet problems and it's not very well documented, either.

It's very easy with ANY control system to be just overwhelmed by the complexity of it--and to blame the control system for hardware problems. It's always best to make sure the hardware is working properly (screws are tight, crimps are good, devices (solenoids, pressure switches, limit switches, T/Cs, etc.) are working properly before diving into the SpeedTronic panel and its operation/configuration.

markvguy
 
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