Do I need a ground connection for the dataTaker RS485 network?
Yes, although RS485 is often called a two wire network, it is a voltage driven balanced (Two wire) network, the fact that it is voltage driven implies that a ground connection is required. The common mode range of an RS485 network is set in the standard as -7 to +12 VDC. When the dataTakers are powered from the same power supply and have a common ground, the system will work. Once you start powering the dataTakers from remote power supplies then the chances of exceeding the common mode range increase (Different power supplies can have different ground points). This can lead to degradation of the communications reliability and in extreme cases damage to the dataTaker. By connecting the dataTaker ground terminals together we ensure the common mode range is never exceeded. Good wiring practices should be used for all installation wiring, this includes low impedance ground connections between dataTakers connected to any common communications wiring. Appropriate communications cable (twiste
