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Re: An unusual Oscilloscope phenomenon


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I always call a probe shorted as in the video an "inductive pickup
loop" :-).

Of course, even when a probe isn't shorted it's an inductive pickup
loop too.

Tim.

Re: An unusual Oscilloscope phenomenon



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I'm afraid someone already got a patent on electrostatic discharge.

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Re: An unusual Oscilloscope phenomenon


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Podcast:http://www.alternatezone.com/eevblog /

Nice, love your accent. If it were winter here, I'd fire up my Tek 547
(since my Rigol is at a friend's).
But in summer, the 547 cancels the A/C so I don't use the 547...

Re: An unusual Oscilloscope phenomenon




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Hello:

Since you're into it, why don't you compare the refresh rate of digital vs
analog scopes?
Also known as the waveforms-per-second capability? It's something i'm very
curious about in practice, and also, do the digitals behave as the analogs
(like a low-pass filter) when you increase the freq of a wave-form or
suddenly start aliasing?

Thank you.
I really enjoy your blog

Best Regards
Steve Sousa


Re: An unusual Oscilloscope phenomenon



"Steve Sousa"
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**  Be like comparing chalk with cheese.

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**  Pretty meaningles with analogue scopes that show the input signal
continuously.


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** Digital scopes  SAMPLE  the signal, both in amplitude and time -  then
show you one screen's worth of SAMPLEs.

 Bit later they show you another one.

 Bit like tasing a pot of stew with your little finger.


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** The topic of  " aliens "  with DSOs is verboten among makers and fanatics
alike.

Plain fact is that you do not get to see what is actually coming down the
probe cable and you may well see stuff that is not there at all.

Bit of a worry,  really.


.....   Phil




Re: An unusual Oscilloscope phenomenon


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It's not only about waveforms-per-second, it's also about the capture and
display engine as well.
The manufactuers have various technologies (e.g. Tek Digital Phosphor) to
make their digital scopes have an "analog type" display and response, and
they work superbly. In fact they can be better than analog in many respects.
But that performance costs money, so you have to start paying around say the
$5K mark before you get a digital scope that really performs like an analog
one in terms of variable display intensity, response time, and capture
dead-time.
See here for more info:
http://www.tek.com/products/oscilloscopes/dpo_technology /
http://www.tek.com/Measurement/App_Notes/Technical_Briefs/55-13757/eng/55w-13757-0.pdf

Lower end scopes don't have these "analog like" display technologies, so
then "waveforms-per-second" is pretty much the basic benchmark. Modern
scopes are pretty darn good though, and even the low end cheap ones are
streets ahead of previous generation DSO's.
Those who haven't used a modern high end digital scope don't know how superb
they can really be.

With modern fast real-time deep memory scopes, aliasing is pretty much a
thing of the past.

Might make an interesting future blog...

Dave.

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Re: An unusual Oscilloscope phenomenon




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Is that an Agilent 6000 series scope I see in front of you?

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Re: An unusual Oscilloscope phenomenon


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http://www.tek.com/Measurement/App_Notes/Technical_Briefs/55-13757/eng/55w-13757-0.pdf
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It is indeed.
In fact, it's that exact same setup where I first found this issue,
debugging that actual design as you see there, probably only days before or
after that photo was taken.

Dave.

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Re: An unusual Oscilloscope phenomenon



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The waveforms-per-second depends on the sample rate, the length of the
acquisition memory and the throughput of the display system. Another
thing that limits the refreshrate is the refreshrate of the display.
The latter can be circumvented by adding several swaps into one
signal.

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That depends on the samplerate and the bandwidth. If the samplerate is
lower then the maximum bandwidth expect aliasing effects unless it is
a sampling oscilloscope.

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Re: An unusual Oscilloscope phenomenon



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                                                  ^^^^^ sweeps
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Re: An unusual Oscilloscope phenomenon


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After watching your video, for some reason I was reminded of Starbuck
Flying and his computer adventures.  Aren't you glad he doesn't have a
scope?

:D

Michael

Re: An unusual Oscilloscope phenomenon


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His schematic of the scope probe and scope input are oversimplified to
the point of incorrectness.  Also, he ignored the low-pass nature of
the oscilloscope input, which might contribute to the clean
"sinusoidal" waveform.


Re: An unusual Oscilloscope phenomenon


On Sun, 28 Jun 2009 12:45:41 -0700 (PDT), Richard Henry

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Scope vertical amps don't ring.

John


Re: An unusual Oscilloscope phenomenon


On Jun 28, 6:03A0%pm, John Larkin
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That was not my point.  The limited low-pass band of the input
amplifier and sampling circuit will either completely filter out
higher-frequency components, or will alias them down.  If you are
seeing a nice sinusoidal waveform on an oscillioscope whose
fundamental frequency is close to the frequency limit of the scope,
chck it with a higher-frequency device.


Re: An unusual Oscilloscope phenomenon


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I've seen the same (or similar) result with a higher bandwidth (300MHz)
scope, so the vertical bandwidth limit has nothing to do with it. The
TDS-220 is just the one I happened to have available at the time. I filmed
some comment on this extra stuff but it didn't make the cut.

Dave.

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Re: An unusual Oscilloscope phenomenon


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Do you still get the ringing if the nose of the probe is shorted to
the tip? I thought it was the inductance of the ground lead which
contributed mostly to the ringing.

Re: An unusual Oscilloscope phenomenon


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Yes.


Nope. As I've said, it works without the groud lead even attched, or even on
a bit of coax.

Dave.
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