ETN21 and V500 Barcode Reader connection

[valerio81 0]

Hi there, I try to explain my strange problem. In a machine we have a CJ1M PLC + ETN21 + SCU21 + many Digital I/O. 2 Omron Barcode Readers ( V500 ) are connected to SCU21. The first with standard RS232 ( less the 10 meters), the second using 2 RS232-485 converter ( galvanic separation included). We have other 2 barcode readers connected to a serialToEthernet server (Moxa) and the 2 serial ports of CPU connected to other 2 serialToEthernet server (Moxa). The plant was working good for 2 years but in the last 3 months we burnt 4 SCU21 input ( sometimes from first scanner, sometimes from the second one). We tried to put a input filter on PLC power supplier ( PA202), we tried to disconnect ground in the connector from cable coming from readers. The strange thing is that only the SCU21 have problem. We bought other 2 SCU21, we tried to keep one reader in one and the second in the other one. Actually we are thinking that the problem can be on ground coming to PLC power supplier ( and thinking that SCU21 is more sensible to net problems...) But we have last input avaiable on the SCU, we will try in this way, keeping floating tension on PLC power supplier. But we have also to think to a solution for the future if also this try goes wrong. I'm thinking to connect the 2 readers to other 2 serialToEthernet server (Moxa) and eliminate the SCU21. We actually have an ETN21 and we know that we can use sockets connection but...how can we do?? We still keep the hardware triggering to start barcode reading. But we never tried that before, is just a Send-Receive connection?? Any advide/suggestion/example? Thank you very much!! Valerio