The term ground
has been defined under VDE 0870 as the totality of the interconnected metal parts of an electrical device. Equipotential bonding
betweendifferent components, circuits and modules takes place via the interconnected metal parts - this can be the chassis or the housing. The ground forms the reference potential for all circuits and systems. In terms of circuitry, a distinction is made between signal
ground, chassis ground and ground.
Theground reference of the individual cables, circuits and modules is connected to each other via ground lines at a reference point. The current
flowing via ground can lead to small voltage drops between different ground points and to interference couplings. To ensure protection against contact with housings, ground is connected to earth via a protective earth conductor.