Re: [SI-LIST] : What speed scope should I consider?

Mark Randol (ryvw50@email.sps.mot.com)
Thu, 20 May 1999 14:27:55 -0700

Krull, Nick J wrote:
>
> General input: I've been using the TDS784C by Tek. Its 4Gs, 1Ghz
> bandwidth. I believe Tek may have a better
> model today(higher bandwidth). HP makes similar equipment. You can look at
> 300MHZ signals quite nicely with this gear. But, I would
> generally recommend obtaining the highest bandwidth(mainstream) scope you
> can afford. Given the direction of todays electronics,
> scopes may have the longevity of PC's.

Since they haven't been mentioned, LeCroy (http://www.lecroy.com)
also makes o-scopes that are definitely worth a look. The
triggering modes are at least as good as Tek's, and I just like
the control layout much better. Memory depth is very good. I
used to be of the opinion that if you wanted a scope you bought a
Tek, but I never really have liked the TDS series scopes. Too
many menus. LeCroy is on the top of my list now for that and
some other reasons.

> But several other things enter into the picture which at times are much more
> significant than the mathematics of the scope bandwidth.

Also consider memory depth. If you need to see something fast
while triggering on a slower event (like triggering on audio when
monitoring a data stream), there needs to be enough memory to
save all the points for both traces. Since the time base needs
to be longer for the slow channel, and the sample rate has to be
higher for the fast channel, you wind up with LOTS of data
points. Some scopes may have "uncoupled" time bases by now so
you can have a "fast" and "slow" channel and not need all the
extra memory, but I've not seen them.

Also consider "extra" functions. Many of the o-scopes available
now have everything from FFT's to advanced statistics and math.
Consider how you can interface to the instrument via computer and
whether the software you use has a driver available. How can the
data be exported? Binary files? Excel or CSV spreadsheets?
Graphical dumps to BMP or other formats? How much room does it
take on a bench (including mouse and trackball interfaces)? etc,
etc....

Oh, price can be important too :)

-- 
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Mark Randol, RF Measurements Engineer   | Motorola SPS, Inc.
(480)413-8052 Voice                     | M/S EL381
(480)413-4150 FAX                       | 2100 E. Elliot Road
ryvw50@email.sps.mot.com                | Tempe, AZ 85284
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