RS-485 cable

The connection between MD485s is made with a CABLE2TP-L two-twisted-pair cable with shield and Santoprene jacket. Insulation colors of the twisted pair are red/black and green/white. One pair is used for the differential data (“A” connects to “A”; “B” connects to “B”), and one line of the other twisted pair is used for the signal ground (third connection on the MD485 terminal block). This is shown in RS-485 connections and grounding. The cable shield should be connected to a chassis or earth ground (NOT the signal ground).

When connecting to equipment that uses – and + terminal markings, the MD485 A terminal is connected to the – terminal and the MD485 B terminal is connected to the + terminal.

If an application requires both the maximum distance (4000 ft) and the highest data rate (115k) for the MD485, a better quality cable, such as a polyethylene data cable, is recommended.