Re: gEDA-user: basic anti-EMI design q

[Bob Paddock <bob.paddock@xxxxxxxxx>]

> As the ground is thought as a zero point, nothing can propagate through
> it.
> 
> Unless the ground has resistance or inductance, but then it's not a ground.

Dr. Howard Johnson's site and news letter has some interesting things to say
about "ground". http://www.sigcon.com .

http://www.sigcon.com/newsletter.htm is worth looking at.

This email came in on Friday, but I can not yet find it on his site,
or I would just post the link :

[hsdd]  High-Speed Digital Design Newsletter -  Reason for Ground Splits
From: "Dr. Howard Johnson"
  To: hsdd AT freelists.org
  Date: Friday 08:02:53 pm
   
               REASON FOR GROUND SPLITS

HIGH-SPEED DIGITAL DESIGN     -  online newsletter  -
Vol. 9  Issue 04

[snip]

Dr. Johnson replies:

  If you are not familiar with them already, check out
  these three background articles before proceeding:
  
     ADC Grounding   (predecessor to the article you
     mention)
     http://www.sigcon.com/Pubs/edn/adcgrounding.htm
     
     Multiple ADC Grounding   (which you already
     found)
     http://www.sigcon.com/Pubs/edn/multipleadc.htm
     
     Common-mode Ground Currents  (presents a terrific
     visualization of the problem)
     http://www.sigcon.com/Pubs/news/7_02.htm
[snip]
[End Newletter]

See also http://www.sigcon.com/pubsChron.htm :

* Visible Return Current   return current -- I may at last have found a way to demonstrate,
  in a direct (and dramatic) fashion, to any observer, where and how high-frequency current
  flows in a printed circuit board.

* Ground Bounce Calculations high-speed digital design formulas 
   [Why latches do strange things.]

* Ground/Power Planes   grounding, layer stack, power system -- At very high speeds, 
  bypass capacitance needs to be within less than 1/10 of a rising-edge-length in order to function effectively.

* Probing High-Speed Digital Designs   probes -- In high-speed system developments, the ubiquitous 10-pF 10:1 
  capacitive-input probe is no longer adequate. The two alternatives are the FET-input probe and the resistive-input probe.

Those are three of many years worth of tips.  I realize a furnace controller is not "High Speed" but electrons
still move darn fast... :-)