EMI Questions

Hi,
Trying to better understand some EMI concepts from reading Henry W. Ott's Electromagnetic Compatability Engineering published in 2009. From what I'm reading upto 100kHz freq signals its best to ground the shield on only one side, I got that, great stuff. Though then it gets a little more difficult, he goes into saying this on page 90 in .

"Usually, it is better to ground the shield at the source end, because that is the reference for the signal voltage. If the signal source is floating (not grounded), however, then it is better to ground the cable shield at the load end."

Alright, my designs are principally on aircraft. What exactly is the definition of a floating signal source? How do I know if I'm working with a floating signal source? I'm worried I've been doing my designs incorrectly, so any clarification on this subject would be greatly appreciated.

Thanks

Hi Rick,

I found this article that might be a little helpful to your question.

http://zone.ni.com/reference/en-XX/help/370466V-01/measfunds/floatsig/

Hope it helps.

Hello Rick!

To answer your question, a floating signal source is defined as a source that is not connected to a common ground. A concrete example is a battery. It has an isolated ground-reference point.

Good luck on your design.