[geeks] Tektronix TDS 220

[Dave McGuire]

On July 15, Joshua D Boyd wrote:
> What do people think of these scopes?  I know the brand is well
> reguarded.   I liked it when I use it.

  The TDS series are pretty nice scopes all-around.  Very compact, nice
displays, decent feature set.  And well-built, of course...they're
Tektronix, after all.

> They cost quite a pretty penny, even used though.  Does Tektronix have
> any good models that are digital and dual trace, but perhaps a lesser
> Mhz?  I'm mainly interested in something more appropriate for audio
> work, which I'd imagine means that even 1Mhz is more than is strictly
> needed, but I wouldn't object to being able to use it for small
> digital electronics projects.

  Dual-trace vs. single...I haven't seen a single-trace scope (digital
or otherwise) in a very, very long time.  Even most (if not all) of
Tek's low-end cheapie analog scopes (like the 2200 series) are
dual-trace.

  Are you sure you want a digitizing scope?  That'll push the price WAY
up, and digitizing scopes aren't the best choice for many
applications.  For catching single-shot signals...catch an event and
then tear it apart over the next fifteen minutes...a digital scope is
the best [only] choice.  But for repetitive stuff an analog scope is
generally best.  An analog scope under digital control is even
better, which includes pretty much all analog scopes made within the
past fifteen years or so.

  My analog scope is a Tektronix 2465A.  Quad trace, dual timebase,
350MHz, absolutely *godlike* triggering capabilities...top of the line
a couple of years ago; I don't think they have any better analog
scopes even now except for the 2467.  Oh, and there's a "B" version of
my scope which is 400MHz instead of 350.

  My digitizing scope is an HP 54111D, dual trace, 500MHz GaAs-FET
front-end, remotely operable, will do 1GHz repetitive in single-trace
mode with an external pod.

  These two scopes are the absolute finest I've ever used or
seen...that's why I bent over backwards to get them. :) The newer
Tektronix "DPO" scopes are very nice, but way, way expensive.  Their
biggest deal seems to be their portability, which isn't an issue for
most of us.  My 2465A is *very* portable...it's small, very light, and
has a good handle.  The DPOs are just smaller...LCD display so they
don't need the depth for a CRT or the HV power supplies to drive it.

  For pure digital stuff, you might want a logic analyzer...Some people
call them "digital scopes", which I suppose isn't a horrid misnomer,
but this means the term "digital scope" can mean either "logic
analyzer" or "scope that digitizes and presents analog signals in the
digital domain"...the latter is obvious, the former typically has
eight or more channels that only distinguish between a "0" and a
"1"...for applications in which timing relationships between signals
(say, data bus transitions vs. RD/WR control lines for example) are
more important than the analog-ish characteristics of said signals
(rise time, ringing, etc).  Both Tektronix and HP make very good logic
analyzers..I use an HP 1631D, but the Tektronix 1240/1241 are both
very nice and available pretty cheaply these days.

        -Dave

-- 
Dave McGuire                  "Needing a calculator indicates that
St. Petersburg, FL              your .emacs file is incomplete." -Joshua Boyd