I have to communicate different modbus slaves (energy meters , breakers) with MQ PLC(master) in one loop.
These slaves will be of different manufacturer make.
Is there any chance of communication issue?

how did you get to be a senior systems engineer if you don't know the basics.
there are some strange qualifications out there!!

If all the devices conform to the Modbus Specification there should be no issue with devices from multiple manufacturers on the same Modbus RS485 communication network. While there is no way to guarantee that there is no chance of communications issues, it is unlikely to be caused by having devices from multiple manufacturers on this type of Master / Slave network. Communications issues are more likely to be caused by failure to follow the RS485 standard, lack of termination resistance, poor wiring, wrong configuration of the devices, etc.

Any scada, hmi involved? need more information Mahesh, G.

can check the data from different devices in Modscan software .. also take the list of data available from devices and also do confirm what type of data it is i.e it is holding register or otherwise.. then configure each point in plc.

RS485 can be configured with 2-wire or 4-wire configurations.4-wire offers better and robust communication with a feature called collision detection as well.

no matter the manufacture of the devices, it is important that support the same communication protocol.

I recommend 2 wire RS485, and port settings COMx , 8, N, 1.

Good luck!

No problems should happen as long as the master and slaves have common port settings and healthy physical connection(RS485 physical layer) between the master and slaves .
Things to remember:
PLC comm port should be configured as Master.

Energy meter.breakers shall be acting as Slave.

All the devices in the network including PLC should have common port settings.
Port settings include : Physical line RS485 , Transmission speed,Data format ( RTU/ASCII),Stop bit(1 or 2 bits), Parity (Even,Odd,None)

Maximum modbus devices on the network should not exceed 31.

Poll only valid slave address locations only . else communication glitches can happen resulting in reduced comm speed. Refer slave device manuals for finding valid address locations.

Make use of error codes reports in case of communication problems.
Examples of error reports are Illegal Function(01 hex),Illegal Data Address(02 hex)

I hope this will help

I think the system should work fine with if you configure the software correctly. Some time there are some impedance miss match when you are using multiple vendor device in the same daisy chain.

This can be rectified with using Pull Up and Pull down resistor with the RS485 master IC.

Please write if you need any more sugesstion.

Thanks

The only issues I can think of that hasn't been mentioned already is distance a good cable us still limited too 4000 ft. Also 2 wire vs 4 wire. I haven't seen a 4wire device that can't do 2 wire but I also haven't seen every device out there. Ter

The only issues I can think of that hasn't been mentioned already is distance a good cable us still limited too 4000 ft. Also 2 wire vs 4 wire. I haven't seen a 4wire device that can't do 2 wire but I also haven't seen every device out there. Ter