<< Click to Display Table of Contents >> Navigation:  Instrument Connectivity > RS485/EIA485

 

RS485 this is a 2 wire connection and has a maximum cable length of 1.2 km and a maximum of 32 instrument connections.

 

Although this is normally a two wire connection some instruments use four wires.

Follow the instrument manufacturers instructions carefully, paying attention to shielding in electrically noisy environments.

Two wire converters will have connections marked 'A' or '-' and 'B' or '+'. These go to the corresponding connections on the instrument.

If the instrument has four connections you should use a converter with four connections.

If you are told by your instrument manufacturer that you can use a two wire converter, on the controller jumper the Transmit + (or B) to the Receive + (or B) and the Transmit - (or A) to the Receive - (or A). This leaves you with one '+' (or B) connection and one '-' (or A) connection to make to the converter.

Four wire converters will have two Transmit (sometimes 'send') and two Receive connections.

If your instrument has four connections read the RS422/EIA422 help

These  marked either '+' & '-' or 'A' & 'B' (or both)

If your instrument has two connections, on the converter jumper the Transmit + (or B) to the Receive + (or B) and the Transmit - (or A) to the Receive - (or A). This leaves you with one '+' (or B) connection and one '-' (or A) connection.