Current used to power device will cause some voltage drop in ground so grond potential at device will be higher. Ground potential will also vary with power used by device. This higher potential might cause a problem if there for example is digital communicatin between devices.
> A ground loop is then a single device is connected to ground more than > once. A good example is a motor driver. It might in a "power" > input called "+" and "-" with the minus side grounded to the AC mains > ground or a chassis frame ground. The in addition there is a > logic level control signal that is "signal" and "ground" wires. > This is a classic gound loop. > > How to break it? Use optical isolation on the signal. This places an > air-gap in the control signal. > > Most of the time the system is not so simple as the above but the > concept is the same, multiple ground connections are not good. Why? > Because in theory current can flow if you have a loop but can never > flow if there is not a closed loop. Then Ohm's law applies -- if > there is current flow there is voltage drop. If the voltage drops > across a gound then you have tow "grounds" that are not the same > voltage. This can be really serious if the motors are large. > > There are a number of conventions that work. but they all do the same > thing, they reduce the number of ground connects to one per "part" of > the system. > > All the rules try to do the same thing, connect nuetral to ground ONLY > at the building service entrance, use opto's on all signal lines. > It is all the same idea > > > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
