I have a meter that transmits via MODBUS. However the PLC is located around 140 meters away, making cabling very expensive. Thus I was thinking of using a MODBUS to Lan convertor since both next to the meter and the PLC I have a data cabinet.

The convertor I'm thinking of buying is this:
http://cgi.ebay.co.uk/ws/eBayISAPI....akeTrack=true&ssPageName=VIP:watchlink:top:en

Do you think this would work?
My question is if I install a convertor next to the meter, would I require another convertor next to the PLC?

Thanks!

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You may or may not need another converter at the PLC.

I would get a pair of RS232 to RS485 converters.

--
Bob
http://ilbob.blogspot.com/

 

It might work. I didn't see any software for configuring it. That type of serial server is typically configured on both the serial side and the LAN side.

It's not an industrial serial server with its wall wart coax power plug but it might do the job of converting 232 or 485 to an Ethernet packet or vice versa. If it were me, I'd want to read the documentation first to see if I make heads or tails out of it. I don't read Chinese.

Would you need a serial server at the PLC end? It depends on what communications hardware port and communication capability the PLC has.

Modbus meters do not 'transmit' their data. A Modbus slave is silent unless spoken to.

The PLC would need to have Modbus master functionality so that the PLC's Modbus master can query the meter and ask for data. Some PLCs have Modbus, some don't. Some have Modbus RTU (infrequently Modbus ASCII) which talks on a serial (RS-232 or RS-485 port), others have Modbus/TCP which communicates over ethernet. Most can have a Modbus Master added with hardware/firmware if a Modbus master isn't included already.

Before you buy comm hardware like the serial server, you ought to investigate whether your PLC has a Modbus master.

By the way, an RJ-45 jack is not necessarily Ethernet, particularly on a PLC.

Nor does an Ethernet port necessarily mean that the Modbus protocol is supported.

 

Yes, for 150 meters you could even use spare cat5 pairs with rs485.

Regards
cww

 

We have a series of products called our TDS series. Using 2 of these, you can form a serial data tunnel using Ethernet pass the data to your PLC. At both ends, you will have either an RS-232 or RS-485 connection

For a RS-485 data tunnel, you will need 2 of TDS-715
http://www.icpdas-usa.com/tds_715.html