Using SNMP to poll Logix PLC

Hi,
Recently a proficy historian server was installed which is receiving downtime information from a logix 5563 processor over OPC using RSLinx.I was not involved in the installation or set up so I don't have a lot of experience with the system.
Every now and again the server loses communication with the PLC. We have been informed that this is due to a feature of RS Linx. If a node drops off the network for even a split instant the communication is lost and communication must then be restored manually.
The problem is that many hours often pass before the lost communications is noticed and hence many hours of information is missed.
I was thinking that we could use something like SNMP (Simple Network Management Protocol) to poll the PLC and check that communications are healthy, if not then we could generate an email to send notification of lost communication. I appreciate that SNMP is based over TCP/IP but I came across the article that I have attached that briefly discusses the use of SNMP in process control over OPC server.
If anyone has any experience of something similar I would be grateful to hear about it.

Regards,
Donnacha

First, I would verify with Rockwell that what you have been told is in actual fact true. If you are being told this by the server company, then it might be a simple case of passing the buck.

If the issue is loss of communications at the server, you may want to consider another server. We distribute KepserverEX from Kepware. It offers both the Allen Bradley driver suite and the capability of SNMP. Here are links with more information:

http://www.eternity-sales.com/Kepware/kepserverex.htm
http://www.eternity-sales.com/Kepware/snmp.htm
http://www.eternity-sales.com/kepware/snmp_agent.htm

Other options you may want to review and consider are Redundancy Master and System Monitor:

http://www.eternity-sales.com/Kepware/redundancymaster.htm
http://www.eternity-sales.com/kepware/systemmonitor.htm

You can download a fully functional version of KepserverEX through the following link:

http://www.eternity-sales.com/Kepware/kepwaredownloads.htm

(as well as the Allen Bradley driver manual)

The software is run time restricted at 2 hours. A purchased license will remove the run time restriction. The time associated with development should be sufficient for testing to verify a reliable and consistent connection.

If you have any questions, feel free to pm or email through the link in my signature.

Disclosure - Eternity Sales is a Kepware Distributor.

Hi Stephen,
Many thanks for the reply and the suggested links. I will have a look through these over the coming days.
I am only getting involved in this project so I have not verified the reasons for loss of communications yet. It is quite infrequent but at the same time I would like to employ some form of network management system to raise an alert when the system has failed to prevent a large loss of data collection.
If anyone else has any experience on a similar project I would be grateful to gain any insight.

Best Regards,
Donnacha

Greetings, the ControlLogix controllers to in fact support SNMP and you can get traps from them indicating that the controllers has stopped processing or has rebooted etc.

If you are using Proficy then you have access to the IGS server. The Premium IGS license gives you access to the SNMP Manager driver. The Standard IGS license enables the Controllogix Ethernet driver. It will reconnect to the PLC when communications is lost, automatically.

Hi Fred,
Many thanks for that piece of information. I have checked and we have not IGS installed. It has been suggested by GE Fanuc that it may be a possible solution to cure the intermittent loss of communications problem. Should we opt for it I will try to enable the SNMP Manager and see if I can get it set up.

Best Regards,
Denis

In theory, any OPC client should work exactly the same with any OPC Server. That's the whole point of the OPC Data Access standard.

In practice, though, GE's OPC Client has not worked well with RSLinx Classic. Both companies point fingers at one another, and because they are competitors, neither one is eager to accept blame and make a change to their software. It's a game I won't play.

The claim that RSLinx Classic OPC requires a manual restart after every communication loss is ridiculous: tens of thousands of RSView32 installations that deal with disconnection and restarts of controllers would tend to disagree.

Yet here you are, with GE claiming you need a separate communications monitoring infrastructure.

If this were my system, I would cut out the issue by using GE's brand-labeled release of Kepware: the "IGS" suite. By all reports, Proficy and Cimplicity work better with Kepware than with RSLinx, and if you buy the software from one source they can't point fingers.

Hi Ken,
Many thanks for the advice. Much appreciated.

Regards,
Denis

Hello Denis, we may be help you with the part where you want to monitor the PLC over SNMP and send status information using SMS or email. We have a GSM/GPRS/Ethernet Gateway with an SNMP Client/Server interface. The gateway can be an SNMP manager or an agent, send/receive traps. It can further relay the information over a GSM/GPRS/Ethernet network by SMS or email.

http://www.protoconvert.com/RemoteMonitoring.aspx