[SI-LIST] Re: Jitter measurement floor on different high bandwidth oscilloscopes
- From: Heyfitch <heyfitch@xxxxxxxx>
- To: steve weir <weirsi@xxxxxxxxxx>, si-list@xxxxxxxxxxxxx
- Date: Thu, 10 Jun 2010 11:09:25 -0500
Agilent's app note 1491 (5989-0553EN.pdf) illustrates the points Steve made
below. (Never mind that it is written by Agilent and naturally shows that
Agilent's solution is "far superior" to Tektronix' one.)
- Vadim
On Wed, Jun 9, 2010 at 11:49 PM, steve weir <weirsi@xxxxxxxxxx> wrote:
> Be wary of specifications and marketing hype and FUD. Modern scopes are
> very dependent on the signal processing: analog and especially digital.
> Where one vendor claims advantage in slew rate another claims advantage
> in noise floor. Overactive DSP algorithms have been seen in various
> scopes that create waveform artifacts that are not real. I've gone
> through considerable pain with customers whose scopes were lying to
> them, where we had to set-up experiments with better behaved instruments
> in order to get them to see the truth. You want to know that if you
> follow good measurement practice that what your scope tells you is
> faithful, and not a DSP induced fantasy.
>
> Claims are all find and good, but for the kind of money that you are
> spending, you owe it to yourself to have each vendor come in with their
> scopes and put them through paces with a clock / pulse generator that
> you supply in probing configurations that you set-up as representative
> of the type of work you expect to do.
>
> The other thing that you should take into careful account is that modern
> scopes represent an investment in probes that is often similar to the
> price of the scope itself. It is just as important to evaluate the
> probes: How they perform, do they meet your physical access needs, how
> much do replacement supplies cost for things like solder ins cost, what
> probes are you already invested as anything else about the scope.
>
> Steve.
> prasad wrote:
> > Hi every one....
> >
> > i am evaluating high bandwidth oscilloscopes (12GHz) from different
> > vendors. I was looking the data sheets of them. One of the
> > them(DSO91204A) has very good noise floor compared to others. Though
> > its a good thing for me but when it comes to the jitter measurements ,
> > the lowest jitter that can be measured on that is dependatnt on the
> > slew rate of the signal ,which is actually true(since the voltage
> > noise will have a second order effect on the timing of the signal).
> > But when i looked at one more vendor (SDA13Zi) the noise floor is poor
> > compared to other. In which case the lowest jitter that can be
> > measured (jitter measurement floor)should be higher than earlier. But
> > if you look at the datasheet, they have specified a fixed value for
> > this which is very less .
> > My question is , if the noise floor is high in the second box how
> > would the jitter measurement floor be less?
> > second one is , since the timing noise(jitter) is dependatnt on slew
> > rate, how a fixed value is given in datasheet?
> >
> >
> > please help me understand. Am i missing some other factor here?
> > Welcome all your suggestions and ideas...
> >
> >
> > thanks in advance...
> > prasad
> >
> > h
> >
> > On 09/06/2010, colin_warwick@xxxxxxxxxxx <colin_warwick@xxxxxxxxxxx>
> wrote:
> >
> >> (Note: I sent this info to Hermann off-list but he suggested it might be
> of
> >> general interest. Send flames to me, not Hermann, if it isn't.)
> >>
> >> In ADS the implementation is:
> >>
> >>
> >> "Fast" corner
> >> (a) the max values are selected for all the I-V data (Pullup, Pulldown,
> >> Power Clamp a Ground Clamp) and for the waveform data (Ramp, Rising
> Waveform
> >> and Falling Waveform), and
> >> (b) the min values are selected for all R, L, C, delay and TT data.
> >>
> >>
> >> "Slow" corner is the reverse obviously
> >> (a) the min values are selected for all the I-V data (Pullup, Pulldown,
> >> Power Clamp a Ground Clamp) and for the waveform data (Ramp, Rising
> Waveform
> >> and Falling Waveform), and
> >> (b) the max values are selected for all R, L, C, delay and TT data.
> >>
> >>
> >>
> >> -- Colin
> >>
> >> -----Original Message-----
> >> .
> >> .
> >> .
> >>
> >> Any feedback from the tool vendors how they implemented this selection ?
> >>
> >> Thanks and Regards
> >>
> >> Hermann
> >>
> >> EKH - EyeKnowHow
> >> Hermann Ruckerbauer
> >> www.EyeKnowHow.de
> >> Hermann.Ruckerbauer@xxxxxxxxxxxxx
> >> Veilchenstrasse 1
> >> 94554 Moos
> >> Tel.: +49 (0)9938 / 902 083
> >> Mobile: +49 (0)176 / 787 787 77
> >> Fax: +49 (0)3212 / 121 9008
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> >>
> >
> >
>
>
> --
> Steve Weir
> IPBLOX, LLC
> 150 N. Center St. #211
> Reno, NV 89501
> www.ipblox.com
>
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>
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