On Tue, 2006-04-18 at 11:11 -0300, Gerhard Fiedler wrote:
> Xiaofan Chen wrote:
> 
> > Yet I consider this scope (TDS220) and some other similar models
> > (TDS2xxx/3xxx) one of the worst scope I have ever used. 
> > 
> > I do not know the 1Gs/s is for real or not but it is much worse than the
> > old HP54600B I've used before. It is also much worse than the old
> > TDS3xx/4xx/5xx models. The screen is very slow. 
> 
> I have a TDS210 -- probably the most low-end of all these, but I have yet
> to have a problem with not seeing something due to slow screen. Of course,
> the "visual feel" of an LCD screen (TDS210/220) is a lot different compared
> to a CRT (HP54600B), but most of the time I capture the signal and then
> analyze it -- and the analysis usually is /much/ slower than the screen,
> and I least feel generally more comfortable looking at an LCD screen than
> at a CRT. (Besides of course the other advantages related to space, weight,
> energy consumption and ruggedness.)
> 
> Seriously, for me the screen seems to show what's there (or better said
> what the scope captures). I don't see what one would gain if it were
> faster... what are you missing? Or what do you mean when you say the screen
> is very slow?

Well, I guess it depends how you approach things.

You CAN'T use that scope like you would an analog CRT scope. If you do
you will be disappointed.

It takes a while to get used to a digital LCD type scope, but once you
do the benefits become apparent.

I regularly use an analog scope and a digital one like this one. Each
has it's place. There are times when an analog scope is the better
choice (you always have to be aware of aliasing and "fake" signals).
There are other times when a digital scope is FAR better (anything
one-shot, or "not often" shot stuff).

A good example is the injector pulses in a car at idle. These pulses are
very short in duration, yet spaced VERY far apart (relative to the pulse
width). Using an analog scope is "difficult" since the persistence of
most phosphors isn't enough for that sort of thing. Using a digital
scope results in much easier to obtain measurements.

OTOH, when you're dealing with a completely unknown signal you have to
be VERY careful when using a digital scope that you're not looking at an
aliased version of the signal.

Personally, I've used the TDS-210 extensively and once you understand
the limitations inherent to a digital scope, it is an amazing useful
beast, and so portable!

TTYL

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