ODP: scope question

[Buck Buchanan]

At 07:44 PM 10/29/98 +1000, Merlin Zener wrote:
>Don Tillman wrote:
>> 
>>    From: Roman Sowa <rsowa at WizjaTV.pl>
>>    i'm about to buy Tek's TDS210 (60MHz, 1GS/s, LCD)
>>    anyone used this?
>>    is it reeeally good or just good?
>>    i don't want to spend too much ($1400) on a scope which is
>>    just not-bad
>> 
>
>One of the best things about it is the ability to directly
>read the DC volts, peak volts, RMS volts *and* frequency -
>all there on the screen!

Hi all,

I too was considering this exact scope and got to spend some time with it
when Tek brought their "product fair" here to work a few months ago.  I use
the high end Tek digital guys all day at work so I felt I had a good base
to compare against.  Here are a few of my general impressions.

Although it's software is a little different, if you're already Zen with
the TDS scopes, you won't have to relearn this one.

Here's the most important consideration (to me) about using a digital scope
for audio: The record length is relatively long (2500 samples).  2500 is
long enough so it "feels pretty analog" in the audio band - being, it runs
a "real" trace in real time.  However, there is no option to increase
record length.  One drawback here:  unlike ALL the other TDS scopes, this
new series doesn't display the current sample rate on the CRT.  Sure, it
*can* sample at 1GHz per channel but only at the highest time base setting
- as you slow down the timebase, the sample rate drops a lot!  If you're
not carefull, you can alias the front end get goofy results.  Wanna look at
the modulation envelope of a 20KHz signal AM'd by a 20Hz sine wave...
forget it..  The 20KHz is ganna alias at any time base slow enough to
observe the 20Hz envelope.  Absolutely, one needs to find out (It's in the
manual?...) what sample rate runs at what time base and paste a list on
your bench.  At slower time base settings for audio frequencies, it's not
ganna be sampling anywhere near 1GHz - 500KHz if you're lucky.  Personally,
I need to see more specs before I buy.  

Although I didn't get to play with it because the demo didn't have the
option installed, there is an FFT option which to me was the big selling
point.  The FFT board is $500 and also contains printer and computer port
stuff so you can ignore the communications board option.  FFT spectrum
analysis is why I originally got a woody over this box.

Yeah, it does take a bunch of simultanious measurements which is cool.
Also horizontal and vertical markers with deltas displayed.  Plus the
delayed time base interface is interesting (you get it triggering they way
you want it then move a window around the area you want to zoom in on).
Obviously, all the other stuff the makes digital scopes rad is there and
very usable.  Sure, there are menues and slight delays before changes take
place... but you get used to it.

Wow, didn't mean to write a book.  I didn't buy this box mostly because I
just can't afford it right now.  The most power per $ I've seen in a bench
top digital ever!  I would reccomend the FFT option if you do go for it.
But I still wouldn't want this on my bench without a decent analog right
next to it...

Take it easy and let me know how you like it if you get it!

Buck