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If I turn the panel that houses the slaves off then turn it back on I get differant results on what sends data back. Somtimes I get all four other times I may only get one, two or three of the slaves. I am using 9600 baud RS-485 to a RS-485 to RS- 232 converter. My HMI is Infilink with the KEPWare Server. Im am using OPC tags between the two. Any help would be great as I am running out of options

Try switching 1 of the slaves on at a time.
Also the order of switching on may be varied to determine if a specific slave is responsible.
If the slaves are configured to send on demand they may only activate data sending if changes occur. What is different? in the cases where only 1, 2 or 3 slaves are sending back. Are any other devices connected?

Hi there,

Make sure that you have the correct termination resistors on the first and last node. I could also be an good Idea to install Bias resistors (Pull-up/down resistors). This usually makes the communication stable.

/Patrick @ HMS