Graphic courtesy of NOAA
Delta Automation is prepared to assist any or all of our clients that were in the path of Harvey or may be in the path of Irma. Our stock of new and refurbished equipment is ready to go to get you or your clients equipment up and running as soon as possible.
Our field service team will be on alert to assist with any on-site needs as well. Please don’t hesitate to contact us via phone or email!
804 236 2800 or 1 888 PC DELTA Email: email@example.com
As with any addressable network, having duplicate addresses is an issue. On Modbus Plus networks, one of three things can occur. Modicon technical support disagrees on this subject but in my 30+ years of working with these networks all over the world, I have proven differently many, many times.
The first, and most likely event to occur, the node that is being added to a network with the same address, will simply not be allowed to join the network.
The second thing that may occur, the node that is being added to the network will displace the existing node with the same address, assuming its’ place upon the network.
The third thing that may occur, is that when connecting the new node to the network with an existing node address is that the two nodes alternate joining and dropping off of the network.
The second and third options are obviously not desirable results. For this reason ALWAYS be certain of what addresses are existing on any given network. Utilizing a network discovery tool such as MBPStat, should eliminate any dual addressing.
Very recently, while performing a quick troubleshooting procedure upon a Modbus Plus network, I found a unique situation. I knew that I had a duplicate address on my computers’ PCMCIA card. however the plant was down, with no equipment running , and I was just doing a quick error check after repairing an illegal splice on the network. I was located at the MB+ repeater between segments 3 and 4 of this network. I monitored segment 3 for errors, all was OK, then I monitored segment 4 for errors, again all was OK. I reconnected the cables back to the repeater and then went to the end of segment 4 to monitor the entire network for errors. I was surprised to see all “U”‘s on every node! Those familiar with MBPStat, know that this indicates the monitor cannot properly identify the nodes. I went back to the repeater and checked both segments individually, again, all was OK. It was then that I remembered that I was utilizing an already assigned node address. I suspected this may be the issue. I again reconnected the cables back to the repeater, went to the end of segment 4, reset the address to a non-assigned node address. Upon checking the network monitor, it now showed all nodes properly with no errors.This further illustrates the unusual results which may occur in the event of a dual node address.
This is even more reason to be aware of existing addresses when adding any nodes to a network!
From the day after Christmas on through fours days past the New Years holiday, two teams of Delta Engineers were busily working long 12+ hour days testing, repairing and certifying Modicon remote I/O and Modbus Plus networks during a plant holiday shutdown. This project included over a dozen production lines, each with both, remote I/O systems and ModBus Plus systems. Almost all of the Modbus Plus systems had multiple (up to 4) segments. This made for a total of 59 separate and individual certifications performed.
All of these systems had been experiencing issues and required repair. Many previously unknown issues and problems were found and repaired. Additionally, dozens of undocumented changes, modifications, replaced/updated equipment, spare connections and hidden splices were located, documented, and repaired where necessary.
Upon bringing the plants production lines back up, after being down for 10 days, all of the newly certified systems came up with no issues or errors.
Shown here is the collection of certification reports, one for each line and system, that were provided to the client. The documents show and detail the repairs, all of the test results and any recommendations for the network. These reports prove to be invaluable in times of additions, modifications or troubleshooting.
Call or email Delta Automation for more information or a quote on certifying your networks!
Modicon/Schneider customers utilizing the remote push button panels have been informed by the OEM that these items are no longer repairable.
We here at Delta Automation, Inc. still repair these items. We are able to replace the push buttons, lamps, switches etc., as well as repair any of the internal electronics. We service both the Modbus Plus units and the coaxial remote I/O units.
So if you have any of these unique very useful items, for which there is NO direct replacement, please contact us for repair.
Part numbers: MM-16MP-001, MM-32SD-000 or MM-32PR-000
ModBus Plus Dual Cable Phantom Errors
The advantages of utilizing the dual cable capability of the Modicon Modbus Plus system are to increase and maintain system uptime and availability. The dual-redundant nature of the system is virtually invisible to the user. Messages are transmitted on both a primary cable, (A) and a secondary cable, (B) simultaneously. The messages are received on both cables as well.
All message statistics are logged and attached to the message token. If any errors occur, the red error LED will illuminate at both the receiving and transmitting nodes/devices and the error log will indicate the type of error and upon which cable the error occurred.
A dual cable system can also have single cable nodes/devices connected to it. These nodes/devices and the network will function perfectly with the mixture of dual and single cable devices. Of course, the error LED on the transmitting node/device will illuminate if there is no cable B attached to a single cable device.
As long as the message is received on one of the cables, the users’ application will function as it normally would, keeping the application online.
This system greatly reduces the chances of a complete application failure due to a cable issue.
However, when monitoring, checking and testing these dual cable systems that also have single cable devices installed, using MBP Stat, it is very important to utilize a DUAL network interface card, such as an SA85-002 card. If single cable cards, such as an SA85-001 or a PCMCIA card are used, the error statistics reported by the single cable card to the MBP Stat program would be incorrect! The single cable card has no error routines for the dual cable, so it incorrectly reports any errors when the dual cable data is mixed with its’ single cable error routine.
If you must utilize a single cable network card when monitoring or testing a network, you can only check ONE cable at a time. The statistical information for a single cable will be correct.