What is the max cable length that is usable with the ADM101E?
General rule of thumb for RS-232 is 50ft/15m max cable length. It all depends on the capacitance of the cable and the data rate though – the lower the capacitance and the lower the data rate, the longer the cable can be.
The ADM101E is specced at 460kbit/s minimum at Rload = 3kOhm, Cload = 1nF. Therefore if their cable is 47pF/metre (typical value) you should be able to use a cable of up to 21m.
Or looking at it the other way, if using a 5m cable you need to ensure the cable is < 200pF/metre