I think you are confusing ground and neutral. Ground should never move off zero. But the neutral can be up to about 5 volts above ground.
On Thu, Dec 26, 2019 at 2:26 PM N <nicklas.karlsso...@gmail.com> wrote: > > 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 -- Chris Albertson Redondo Beach, California _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
