Dear sirs:

I have the next problem:

I have a Modbus Async Network, connected to a device that allow users to access the Modbus Objects trough a TCP/IP LAN, using a Human-Machine interface.

The Modbus Async network used to have 20 Modbus nodes, but i want to increase the number of nodes to 300. I need to know:

a) Will this increment impact the bandwidth of the LAN?
b) The band width of the LAN depends on the number of modbus objects being accesed at the same time or depends on the number of objects itself?
c) Maybe it has no impact at all or maybe it's a known or measurable rate?

I´ll appreciate your help and support.
Best regards.

 

First of all the data we read from PLC etc. is too light weight comapred to the voice,video or animations etc.So you need to be concerned about even 300 nodes talking on Ethernet.

Secondly in Modbus/TCP:

client asks for some data (a command is sent
to the PLC) and

server gives the asked data only (PLC sends at the most 120-122 Registers i.e. less than 256 bytes).

so the number of BW being used depends on the
objects being Read/Written and not on the total number of objects.

So as per my understanding you need not worry about your LAN getting loaded with data.

Would love to know if this answers your query or if some more angles are there in your question.

Regards,
Aditya