Newsgroups: alt.engineering.electrical
Subject: What is inside HUMplug-e

Anyone has experience on this HUMplug-e product ? 

Web page
http://www.21best.com/21_best/electronic/security/video/filters/for_sale_.html says:
" Simply plug your equipment through this, to cure it of Ground
Loops. Filters out unwanted voltage and current in the ground line
that cause ground loop hum while simultaneously maintaining a solid,
safe ground."

I have experience on many different way on solving ground loop 
loop problems in audio/vidoe systems. Practically every other
types of products listed on that page are known to me in details 
(I have used similar produicts, know what is inside such items, 
even manufactured some quite simlar products). I have written 
some material on ground loop solving to 
http://www.epanorama.net/documents/groundloop/index.html

How this HUMplug-e product works makes me wonder. 
Given the specifications (15A current) and a small 
size it can't be an isolation transformer. 
According the description it keeps the solid 
ground connection it just can't be a "cheater" plugs 
that just simply cuts ground connection (dangerous 
peactice that is not recommended). 

My quess that it does some magic on ground connection 
so that it stops/reduces the current that can flow on
normal ground loop case, but still lets the ground 
connection to be good enough for electrical safely. 
I am just wondering how this is done in such what that it 
works and meets the electrical code safey requirements. 
Anyone has experience on how this is implemented ? 
Some of my quesses would be those impklementation 
possibilities:
- some common mode coil type construction over all wires
- two parallel diodes (on different directions) wired 
  between input and output ground connections 
  (stops current when voltage difference is low but 
  will pass hort circuitfualt currents at low voltage drop)

Anyone commenting my quesses how this device works ?
Anyone has experience on this ?  
        

-- 
Tomi Engdahl (http://www.iki.fi/then/)
Take a look at my electronics web links and documents at 
http://www.epanorama.net/