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Semantics

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Doug Fowler:

--- Quote from: Jonathan Johnson on October 15, 2013, 05:37:53 PM ---One term that is common in the audio industry, and an issue featured prominently in the "AC Power and Grounding" section of the forums, is ground loop hum.

It's really an unfortunate misnomer. The presence of a ground loop doesn't necessarily imply that there will be hum, and hum can be caused by currents on the ground even in systems with properly designed hub-and-spoke grounding systems. Of course, hum is more likely where there are loops than in hub-and-spoke systems.

It would be more precise to use the term ground current interference. Our goal is not necessarily to eliminate ground loops (in the physical topology), but to reduce ground currents and the problems they cause, typically by ensuring that ground voltage potentials between equipment is minimized. Often this means removing ground loops, but also important is ensuring that grounding conductors are of sufficient size that the conductor resistance is low enough to reduce those voltage differentials.

Probably a pointless rant, but using precise terminology helps people understand problems better, and better understanding leads to better solutions.

--- End quote ---

"Out of phase" vs. "Reverse Polarity".

John Roberts {JR}:

--- Quote from: Doug Fowler on October 16, 2013, 12:08:38 AM ---"Out of phase" vs. "Reverse Polarity".

--- End quote ---
Audio phase vs mains power phase.

JR

David J. Thomas:
Henry Ott provides an excellent reference in "Noise Reduction Techniques in Electronic Systems". It is a comprehensive look at the sources of EMI in electronic circuits and also provides valuable insights into the reduction/elimination of the noise interference to meet the applicable test standards. It is must-read for novice engineers and a great refresher for the more experienced designer. No EMC engineer or system design engineer worth his/her salt should be missing this volume on their bookshelf!

Kevin Graf:

--- Quote from: David J. Thomas on October 16, 2013, 10:57:08 AM ---Henry Ott provides an excellent reference in "Noise Reduction Techniques in Electronic Systems". It is a comprehensive look at the sources of EMI in electronic circuits and also provides valuable insights into the reduction/elimination of the noise interference to meet the applicable test standards. It is must-read for novice engineers and a great refresher for the more experienced designer. No EMC engineer or system design engineer worth his/her salt should be missing this volume on their bookshelf!

--- End quote ---

This Henry W. Ott 300 page book is from 1988:
"Noise Reduction Techniques in Electronic Systems,"2nd Edition, by Henry W. Ott, publisher: John Wiley & Sons, 1988, ISBN#: 0-471-85068-3.

His new 850 page book is:
"Electromagnetic Compatibility Engineering"
 by Henry W. Ott,
publisher: John Wiley & Sons, hardcover 872 pages, 566 figures, 65 tables.
Publication date: August 2009, ISBN#: 978-0-470-18930-6.

http://www.hottconsultants.com/EMCE_book_files/emce_book.html


John Roberts {JR}:

--- Quote from: Kevin Graf on October 16, 2013, 11:38:01 AM ---This Henry W. Ott 300 page book is from 1988:
"Noise Reduction Techniques in Electronic Systems,"2nd Edition, by Henry W. Ott, publisher: John Wiley & Sons, 1988, ISBN#: 0-471-85068-3.



--- End quote ---

My copy is C. 1976...

Bidding now starts at $2 million dollars..  ;D
=====
I recall seeing a few things in the '76 edition that seemed a little dated in light of the vast expansion of RF energy all around us today. The physics has not changed but the environment has a little. I suspect subsequent editions evolved over time to accommodate changing conditions. I doubt they seriously anticipated sending digital data over power lines, routine PFC for consumer products, etc. back then.   

The 2009 publication is surely up to date.
-------
I recall seeing an almost humorous reference in a very old acoustics text to a unit of absorption as being a "unit area open window".  These days an open window is a noise source.  ;D

JR

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