Re: Calibrating a PG506 w/o Sampling System

Chuck Harris <cfharris@...>

I do the PG506 calibration on a tek 11801C. It reveals

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
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.


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