On 5/23/11 3:40 PM, Eric Smith wrote:
Keep in mind
that a DSO is substantially a different instrument, not
simply a "more modern replacement for an analog oscilloscope". Many
people, some of whom really should know better, assume this because
that's the way things have generally worked with technology, with
digital stuff being perceived as "new" and anything analog perceived
as "old" or otherwise passe'. This is not completely so with DSOs.
They have significant limitations that one MUST be aware of in order
to use them effectively. If you don't know what you're doing with a
DSO, it will give you incorrect information.
Early DSOs certainly were not suitable replacements for analog scopes.
Modern DSOs, except perhaps for the very low-end ones, seem to me to be
suitable to replace analog scopes for nearly all uses. Perhaps there are
some limitations that I haven't encountered?
Display update rates and vertical bandwidth limitations can be issues
for high-speed stuff like laser hacking. Lack of vertical resolution (8
bits in many scopes) limits display of waveform detail. The "fade out"
effects of CRT phosphor in a fast analog recurrent sweep is useful for
some applications and tough to emulate, though Tek's "DPO" (Digital
Phosphor Oscilloscope) line did make a good stab at addressing that.
Ruggedness in extremely electrically unfriendly environments can also
be an issue. My friend Jon Singer (noted laser guy) regularly sees
trace curlicues, no joke, on his Tek 7104's display during test firings
of his lasers...I'm not at all confident of modern digital scopes'
ability to survive that sort of electrical pounding.
Some of these things are now being addressed by very high-end digital
scopes. So nowadays, you might be able to buy a digitizing scope for
about the price of a Porsche 911 that might approach the performance in
some of the above-mentioned areas of an analog scope that can be picked
up for a few hundred bucks, along with a spare. ;) In that situation,
it's pretty foolish to push for a digitizing oscilloscope just for the
sake of "going digital".
Note well that I'm not poo-pooing digitizing oscilloscopes. I have
several (Tek TDS3012, HP 54111D, a few LeCroy high-resolution scopes)
and I use them regularly. My intention here is to point out that they
are not always viable replacements for analog oscilloscopes...they're
fundamentally different pieces of test equipment, with different
strengths, weaknesses, and applications.
-Dave
--
Dave McGuire
Port Charlotte, FL