🚀 go-pugleaf

"David L. Jones" <altzone@gmail.com> wrote in message 
news:%TXam.45224$3m2.4738@newsfe06.iad...
> For those interested in my original blog on the oscilloscope probe/static 
> pickup phenomenon, you might be interested to read another blog commenting 
> on the issue:
> http://www.edn.com/blog/1700000170/post/1120046912.html
>
> All rather interesting discussion, so I quickly threw together another 
> blog (#20) showing the effect again using a regular coax cable, and also 
> busting the myth that it's the ground probe loop causing it.
> See my blog link below.
>
> Dave.
> -- 
> ---------------------------------------------
> Check out my Electronics Engineering Video Blog & Podcast:
> http://www.alternatezone.com/eevblog/
>
  Hi David,
 Just for kicks and another data point, put your 50 ohm termination directly 
on the scope
without any coax and try your chair movement. Then directly short your scope 
input
with a short wire and aluminum foil and repeat test.
                                   Thanks, Mike 

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. 

n. 

"notme" <notme@notme.org> wrote in message 
news:0001HW.C691CB63009FA4D0B08A39AF@news.eternal-september.org...
> 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.
>
> n.
>
 Well, I guess that depends, do you believe the experts or your lying eyes! 
:-)
                                                             Mike 

David L. Jones wrote:
> For those interested in my original blog on the oscilloscope
> probe/static pickup phenomenon, you might be interested to read
> another blog commenting on the issue:
> http://www.edn.com/blog/1700000170/post/1120046912.html
>
> All rather interesting discussion, so I quickly threw together
> another blog (#20) showing the effect again using a regular coax
> cable, and also busting the myth that it's the ground probe loop
> causing it. See my blog link below.

And for those who still can't get enough.
Blog 21 has more static goodness, this time with anti-static lab coat and a 
better oscilloscope.

Dave.

-- 
---------------------------------------------
Check out my Electronics Engineering Video Blog & Podcast:
http://www.alternatezone.com/eevblog/ 

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.
-- 
---------------------------------------------
Check out my Electronics Engineering Video Blog & Podcast:
http://www.alternatezone.com/eevblog/ 

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

-- 
Joe Leikhim K4SAT
"The RFI-EMI-GUY"�

"Use only Genuine Interocitor Parts" Tom Servo  ;-P

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

John Devereux wrote:
> 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.
> 
> 

It is possible that even an older style CRT scope might be susceptible 
given the opening for the CRT screen might be a sufficient aperture for 
the ESD pulse.

-- 
Joe Leikhim K4SAT
"The RFI-EMI-GUY"�

"Use only Genuine Interocitor Parts" Tom Servo  ;-P

On Jul 26, 8:22 am, "David L. Jones" <altz...@gmail.com> wrote:
> For those interested in my original blog on the oscilloscope probe/static
> pickup phenomenon, you might be interested to read another blog commenting
> on the issue:http://www.edn.com/blog/1700000170/post/1120046912.html
>
> All rather interesting discussion, so I quickly threw together another blog
> (#20) showing the effect again using a regular coax cable, and also busting
> the myth that it's the ground probe loop causing it.
> See my blog link below.
>
> Dave.
> --
> ---------------------------------------------
> Check out my Electronics Engineering Video Blog & Podcast:http://www.alternatezone.com/eevblog/

Dang!  Thanks for the EDN link Dave.  I like your video blogs, but
let's face it we all make mistakes once in a while.  The above link
was exactly my take on the effect the first time I saw it.  I've made
lotsa RF pickup probes by hanging loops of wire on the end of X10
'scope probes.  A one turn probe just has less inductance.  And you
should see 'about' the same voltage electro-statically.... without the
probe shorted.   Part of the problem with static discharge
measurements is reproducing the discharge.  It's hard to get the same
amount of charge each time.  I've used the piezo sparkers from butane
lighters to try and deliver high voltage sparks.  (less than ideal
sources.)  I still like my idea of changing the loop area and seeing
if the voltage decreases.

George H.

(I haven't seen your latest V-blogs.)

David L. Jones wrote:
> For those interested in my original blog on the oscilloscope probe/static 
> pickup phenomenon, you might be interested to read another blog commenting 
> on the issue:
> http://www.edn.com/blog/1700000170/post/1120046912.html
> 
> All rather interesting discussion, so I quickly threw together another blog 
> (#20) showing the effect again using a regular coax cable, and also busting 
> the myth that it's the ground probe loop causing it.
> See my blog link below.

Nifty! You've done a good job of proving your point.

-- 
    W
  . | ,. w ,   "Some people are alive only because
   \|/  \|/     it is illegal to kill them."    Perna condita delenda est
---^----^---------------------------------------------------------------

Fred Abse <excretatauris@invalid.invalid> wrote:

>On Wed, 29 Jul 2009 14:31:16 -0400, RFI-EMI-GUY wrote:
>
>> It is possible that even an older style CRT scope might be susceptible
>> given the opening for the CRT screen might be a sufficient aperture for
>> the ESD pulse.
>
>Tek used to offer an option on their high-end 'scopes, having extra
>bonding contacts around all the panels, and a mesh screen over the CRT
>face. My 7104 is like that.
>
>The old HP180 (lovely instrument, that was) came with a mesh CRT filter as
>standard. Wish I'd still got mine.

I don't think so. These are so old they fall apart. I once bought a
HP183 (up to 300MHz) but it turned out to be a pile of junk.

-- 
Failure does not prove something is impossible, failure simply
indicates you are not using the right tools...
                     "If it doesn't fit, use a bigger hammer!"
--------------------------------------------------------------