🚀 go-pugleaf

On Thu, 25 Jun 2009 22:22:29 +0200, Fred Bartoli <" "> wrote:

>Joerg a �crit :
>> Fred Bartoli wrote:
>>> John Larkin a �crit :
>>>> On Thu, 25 Jun 2009 16:31:09 +0800, TonyS <scarborofun@gmail.nspm.com>
>>>> wrote:
>>>>
>>>>> John Larkin wrote:
>>>>>> On Wed, 24 Jun 2009 21:42:07 -0700, <castlebravo242@att.net> wrote:
>>>>>>
>>>>>>> "David L. Jones" <altzone@gmail.com> wrote in message 
>>>>>>> news:h8B0m.53620$FI5.3564@newsfe12.iad...
>>>>>>>> Check out a rather unusual phenomenon you can see on your 
>>>>>>>> oscilloscope in my latest blog (#14):
>>>>>>>> http://www.alternatezone.com/eevblog/
>>>>>>>> See if you can get it to happen on your scope!
>>>>>>>> I'll offer a free subscription to my blog for the best screen 
>>>>>>>> shot posted :->
>>>>>>>>
>>>>>>>> Oh, and the probe doesn't have to be shorted either.
>>>>>>>>
>>>>>>>> Have fun.
>>>>>>>> Dave.
>>>>>>>> -- 
>>>>>>>> ================================================
>>>>>>>> Check out my Electronics Engineering Video Blog & Podcast:
>>>>>>>> http://www.alternatezone.com/eevblog/
>>>>>>>>
>>>>>>>>
>>>>>>> When I worked a Century Data we had a problem with our new reel to 
>>>>>>> reel vaccuum column tape drive when ever someone would walk by the 
>>>>>>> drive when it was reading it would get data errors. The problem 
>>>>>>> was that the shield on the cable from the heads to the preamp was 
>>>>>>> grounded on both ends.
>>>>>>>
>>>>>>> Bob
>>>>>> That's usually the best way to ground shields.
>>>>>>
>>>>>> John
>>>>>>
>>>>>>
>>>>> IIRC head signals mostly went via twisted pair. If they had a shield 
>>>>> as well we would certainly not ground them on both sides.
>>>>>
>>>>
>>>> You *want* large amounts of high-frequency common-mode noise?
>>>>
>>>
>>> Probably. Lots of people don't understand this and I've seen this kind 
>>> of mistake (opened shield) recommended in lots of highly regarded EMC 
>>> books.
>>>
>>> But that's really nice for us. (Joerg?)
>>>
>> 
>> Yeah! But shhht, don't spill the beans here, at least not until I am 
>> retired :-))
>> 
>
>I think I'll retired after you, but this kind of misconception is 
>sufficiently widely spread that we don't have to worry :-)

Yup. Once people get fixated on "ground loops" they are forever lost
to reason.

Ditto high-speed "return currents."

John