Modbus communication in Freelance 2013
In one client location we have Freelance AC900FR controller.
We have DBBV/MOV(Double Block Bleed Valve/motor operated valve)) of M/s Auma Make. the DBBVs are connected to a Moxa Gateway on RS485 communication . This gateway is having 4 serial port to one side and one TCP/IP output to other side. Total 3 modbus segments are connected to three different port of Moxa Gateway. The IP address of Moxa is configured as a Modbus TCP/IP Master interface in freelance. I made one task list and I am polling the DBBV for data(valve monitoring) and writing commands(on and Off).
I am getting a very high communication delay while communicating to these DBBVs. If I give command the response is coming after 60-90 second later. though if same IP is used to check the communication through modbus simulation software(modscan - only one valve at a time). the valves are responding very quickly, i.e. within 1 second.
We called the DBBV vendor, Using their modbus master software the data is coming without any delay. in their software they can poll many devices together like our controller.
Can anybody tell what may be the reason for this much huge communiation delay.
I changed the sequence number in FBD program, the response improved. but after some time the response agiain got detoriated.
Kindly suggest the what may be the issue
How did you configure your Modbus block ? You can use an automatic request, or you can choose to send a trigger on your block for the request.
I had the same problem with my Modbus TCP/IP connection (with a panel 800). I think there was pertubations with the ethernet cable, and sometimes I had timeouts with the connexion (you can see it on Digivis or directly with your modbus block : the error output). It was just a few small cuts, but sometimes the response time was 1 minute or more, due to these timeouts.
For not beeing disturbed, I removed the automatic request mode, and used a trigger (every second for example), and now it's okay...
Sorry for my bad english)