Shielded Twisted Pair subsea application

[ayman]

Hi,

Has anyone tested or is aware of a way to calculate the max length a 14 AWG, individually shielded twisted pair with drain wire and overall shield can communicate at at 38.4 kbps data rate? RE Smith says, 3 miles with #24 at 19.2 Kbps. I'm looking for a relationship between the AWG and cable lenght for one to one communication.

Thanks,
Ayman

[Jan Axelson]

You need to do the calculation for the whole interface, including the driver and receiver and any termination or other components. The RS-485 spec has a limit of 4000 ft. For a longer link you would need to consider cable capacitance and other factors. Offhand I don't know a reference for designing longer links using RS-485 or similar interfaces.

Jan