Chapter 7
path of least resistance. If the power supplies of all nodes use the same electrical
system and their ground wires connect at an earth ground, the ground connec-
tion might be quiet. Even here, though, motors, switches, and other electrically
noisy equipment can induce ground noise. If the nodes are in different build-
ings or using different power systems, the earth ground is likely to have higher
impedance, and ground currents from other sources might find their way intoFigure 7-14: A 100Ω resistor between each node and the ground wire limits the current
in the ground wire when two nodes’ grounds vary.