Re: Calibrating a PG506 w/o Sampling System


Jim Ford
 

Right, John.  I've used both a 54120A and Tek CSA803, although upwards of 25 years ago, and they are quite similar.  I do prefer Tek scopes, and in this case, the modularity of the Tek beats the HP, with its somewhat cumbersome external triggering and sampling boxes.  OTOH, one could bring the boxes close to the DUT and leave the much bulkier scope box on the bench or in a rack.  I suppose one could do the same with the much more lithe Tek sampling head(s) and (a) extender(s).  Tek for time domain, and HPAK for frequency domain!   JimSent from my Verizon, Samsung Galaxy smartphone

-------- Original message --------From: "John Gord via groups.io" <johngord=verizon.net@groups.io> Date: 12/7/20 2:56 PM (GMT-08:00) To: TekScopes@groups.io Subject: Re: [TekScopes] Calibrating a PG506 w/o Sampling System Jim,The HP 54120A/54121A combination also gives very good sampling performance, and is sometimes easier to find at a good price.--John GordOn Mon, Dec  7, 2020 at 10:40 AM, Jim Ford wrote:>> Yeah, I believe that about the 7T11/7S11 pair, Chuck; I have a 7S12 and > a 7S11, with a couple of S-4 sampling heads and S-51 and S-53 for > triggering.  PITA to get them to display anything on the 7904!  At some > point, I will look for an 11800 series scope like the one I had at work > a few decades ago.  I don't remember any issues with triggering back > then.  And the SD-24 sampling head got top marks for pulse fidelity from > PicoSecond Pulse Labs (sold to Tek in 2014, IIRC) back then.  Just got > to run the purchase by the finance committee (my wife)!  She can't say > anything about the space it takes up; I have that covered with a 19-inch > rack next to my bench....> > Jim Ford> > ------ Original Message ------> From: "Chuck Harris" <cfharris@erols.com>> To: TekScopes@groups.io> Sent: 12/7/2020 9:32:49 AM> Subject: Re: [TekScopes] Calibrating a PG506 w/o Sampling System> > >I do the PG506 calibration on a tek 11801C.  It reveals> >all.> >> >But, using a 7104 will only make things worse, best not> >done. As Raymond says, a PG506 adjusted to a pretty> >waveform on a 7104 looks like something you could spear> >fish with on a 11801C.> >> >The 7T11/7S11 pair is supposed to be adequate with the> >proper sampling head, but I have never been able to get> >such a pair to work reliably.  It kind of drifts into> >a measurement, and drifts out.  I never found the problem> >to be worth investigating.  If someone wanted to, I am> >sure that my 7T11/7S11 pair could be had for a reasonable> >price... whatever that is these days.> >> >-Chuck Harris> >> >Raymond Domp Frank wrote:> >>  On Mon, Dec  7, 2020 at 05:17 PM, Jean-Paul wrote:> >>> >>>> >>>  From transient CAL of 2467B, I can say its a tricky and iterative> process, and> >>>  the correct gens and fixtures are essential.> >>>> >>>  You may get by with a 1 GHz digital scope but not the Chinese, HP, TEK or> >>>  Lecroy.> >>>> >>> >>  First of all: Unless the edge settings have been changed, it's probably> not necessary to adjust them because your work hasn't influenced them. I> certainly wouldn't touch them without the right equipment.> >>  OTOH, the transient response calibration of a PG506 is a very simple> adjustment, *if* you have the right equipment and perform the procedure> correctly: One capacitor for the positive edge (C1000) and one for the> negative edge (C940); optimize overshoot for both. That's it. Capacitor refs.> are for SM "Late Model": S/N B040000 up.> >>  However, since you're adjusting a rise/fall time <= 1 ns (that's spec, in> practice usually 700 ps or better), your 'scope (as a rule of thumb) needs to> have a rise time of at most 20% of that: 200 ps. That means a BW for a 'scope> with Gaussian behavior of at least 1750 MHz, about 1400 MHz with many digital> 'scopes.> >>  So, using a 1 GHz BW digital 'scope won't crack it: The edge may look fine> on it but probably will have serious overshoot, which you won't see on your> (too slow) 'scope.> >>  In practice, I'd consider 2.5 - 3 GHz to be the minimum BW required,> taking into account that actual rise/fall time of most units is about 700 ps.> >>> >>  Raymond> >>> >>> >>> >>> >>> >>> >> >> >> >> >> >

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