🚀 go-pugleaf

RFI-EMI-GUY <Rhyolite@NETTALLY.COM> writes:

> David L. Jones wrote:
>> notme wrote:
>>> On Sun, 26 Jul 2009 05:22:31 -0700, David L. Jones wrote
>>> (in article <%TXam.45224$3m2.4738@newsfe06.iad>):
>>>
>>>> http://www.edn.com/blog/1700000170/post/1120046912.html
>>> So, it's not a phenomenon of that scope, but an example of how long
>>> ground clips can get you into trouble at high frequencies, regardless
>>> the tool at the other end of the probe.
>>
>> Nothing to do with the long clip lead on the end, as I
>> demonstrated. Regular issues with long ground clips at high
>> frequency is another problem entirely.
>> You can have the best and shortest ground clip possible and you'll
>> still get this effect, picked up by the probe coax.
>> And the latest video shows you don't even need the cable connected
>> at all to get a response.
>>
>> Enjoy.
>> Dave.
>
> Try with an older analog scope with a metal cabinet. I think you have
> uncovered a shielding weakness with the newer digital scopes. The
> resonant frequency is probably coincidental with the internal
> circuitry or groundplane geometry of the scope

I was thinking that. The IEEE standard for characterising ESD pulse
generators requires the whole scope to be put in a Faraday cage.


-- 

John Devereux