[SI-LIST] Re: si-list Digest V8 #298

Tom -

You're missing the part where he's using the logic channels on an MSO scope,
so all it cares about is High or Low.  He's obviously not trying to look at
risetimes, just raw edge timing.  In any case, all of the timing information
lives in the fundamental frequency, so even if it was analog acquisition
rather than digital, he could still get all the timing information at 500
MSa/s.

Regards,
Tom Zych
______________________________
Tom Zych
Chief Engineer
ASA Corp
phone: +1-413-596-5354
FAX:   +1-413-596-9686


> -----Original Message-----
> From: Tom Dagostino [mailto:tom@xxxxxxxxxxxxx] 
> Sent: Thursday 25 September 2008 11:55 AM
> To: 'Tom Zych'; si-list@xxxxxxxxxxxxx
> Subject: RE: [SI-LIST] Re: si-list Digest V8 #298
> 
> 
> It's the spectrum not the clock frequency that needs to be sampled.
> 
> Sampling a 220 MHz clock signal with a 500ms/sec digitizer 
> would not get what you really want.  Let's assume the 220MHz 
> signal is just a square wave clock. It's fundamental 
> frequency is 220 MHz.  The next frequency in the Fourier 
> series of a square wave is 3X the fundamental or 660MHz. Etc. 
> The actual spectrum of the 220MHz clock is dependent on the 
> risetime of the driver. The sampling rate of the digitizer 
> should be high enough to capture a bandwidth of 0.35/Trise.  
> At best a 500MS/sec digitizer can capture a 1.4nsec risetime. 
>  We don't see many ICs that are that slow anymore.
> 
> Tom Dagostino
> Teraspeed(R) Labs
> 13610 SW Harness Lane
> Beaverton, OR 97008
> 503-430-1065
> 503-430-1285 FAX
> tom@xxxxxxxxxxxxx
> www.teraspeed.com
> 
> Teraspeed Consulting Group LLC
> 121 North River Drive
> Narragansett, RI 02882
> 401-284-1827 
> 
> 
> -----Original Message-----
> From: si-list-bounce@xxxxxxxxxxxxx 
> [mailto:si-list-bounce@xxxxxxxxxxxxx] On Behalf Of Tom Zych
> Sent: Thursday, September 25, 2008 8:04 AM
> To: si-list@xxxxxxxxxxxxx
> Subject: [SI-LIST] Re: si-list Digest V8 #298
> 
> Nirmale -
> 
> First, the 6000-series have a maximum acquisition memory of 8 
> MPts.  To capture 50 msec would require a sample rate of no 
> more than 8M/50m or 160 MSa/s.  Since the signal you're 
> trying to capture is 220 MHz, Nyquist says that 160 MSa/s is 
> too slow by a factor of three - you would need to sample at 
> 500 MSa/s on the scope in order to properly capture the 
> signal.  In other words, it is not possible to capture 50 ms 
> of a 220 MHz signal in one acquisition with an MSO6104.
> 
> Second, I would ask why you believe you need to capture 50 ms 
> of continuous data versus e.g. 10 separate acquisitions of 5 
> ms each (which would allow you to sample at 1 GSa/s into that 
> 8 MPts of memory)?  We encounter customers every day who 
> believe they need to capture huge amounts of data all at 
> once, when in reality capturing it in smaller chunks and 
> combining the analysis results will give them everything they need.
> 
> Third, (and I apologize for a tad of commercialism here) 
> there are products like ASA's M1 Oscilloscope Tools software 
> that can acquire data from your scope and do all sorts of 
> analyses on it (including connecting to Matlab), as well as 
> help you to automate if this is something that you'll need to 
> be doing a lot.  Take a look at www.m1ot.com and let me know 
> if you have any questions.
> 
> Regards,
> Tom Zych
> ______________________________
> Tom Zych
> Chief Engineer
> ASA Corp
> phone: +1-413-596-5354
> FAX:   +1-413-596-9686
> 
> > From: "Nirmale G" <nirmale@xxxxxxxxxxxxxxx>
> > Subject: [SI-LIST] Data Acquisition through Oscilloscope.
> > Date: Wed, 24 Sep 2008 20:26:21 +0530
> > 
> > Hi All,
> > 
> > I have few questions on Agilent Oscilloscope (MSO6104A).
> > 
> > I need to capture 20 single ended I/O lines at 1.2V CMOS 
> logic level, 
> > toggling at 220 MHz from a test board.  I want to use the logic 
> > analyzer in MSO6104A (16 digital + 4 analog
> > ) to capture the data lines continuously. For this, I am
> > using the  IntuiLink Data Capture tool in Microsoft excel to 
> > capture this data via a USB interface from MSO.  But in 
> > MSO6104, at one time I can capture only 50,000 points of what 
> > is present on the screen of MSO. 
> > 
> > I request you to address my following queries:-
> > 
> > 1.       How I should use the MSO to capture more number of 
> > points when
> > compared to 50000.  Is there a way to continuous capture of data in 
> > excel sheet through which, I can capture the 220MHz signal 
> for a time 
> > period of 50msec.  I require this so that I have more data 
> to analyze 
> > offline in Matlab.  At present 50000 samples is very less for 
> > analysis.
> 
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