> I have some questions for those of you out there using TDS-220 scopes.
> What is the one shot sample rate like? And at what memory length? What
> is the width of the A/D sample and hold aperture? I use Fluke 99
> scopemeters around here for a lot of work and although basically good
> for a lot of measurements, they give me fits sometimes because of
> resolution, aliasing, and aperture width limitations.

Hi Frank,

As far as I'm concerned, the single shot rate is the only one that matters.
It _is_ 1GS/s single shot but memory length is quite short at 2500 samples
(for all measurements).

When DSO's first came out (many years ago now), I found the aliasing thing
to be a real problem. At the time I was working on a project that
multiplexed various AC waveforms together and the resultant envelope was
the bit I needed to measure. Not a chance. Every one of them aliased it out
to a few cycles. I thought at the time, that the way to prevent this was to
sample at the maximum rate all the time and for each displayed bit time,
draw a line from the max value to the min value. No more aliasing and a
similar display to that on a tube storage scope.
I should of patented it. Not for the money or anything. Just that I had to
wait about 10 years before Tek came out with the same idea with much
fanfare and a fancy marketing term. Oh well.

Anyway, the TDS-220 does this. If you have a 50MHz signal that turns on and
off every millisecond, on a 1ms/div timebase you get a shaded block where
that happens, rather than the aliased result.

IMHO, the Scopemeters aren't in the same league. This should be considered
a low cost bench scope that doesn't weigh much. (I'm not knocking them at
all. Different tools for different jobs). I've used some pretty expensive
instruments and for most practical purposes, this is up there. Where it
doesn't quite make it is the short memory length, it's lacking in the fancy
trigger options and the display isn't as versatile as a CRT.

Steve.

======================================================
  Very funny Scotty.  Now beam down my clothes.
======================================================
Steve Baldwin                Electronic Product Design
TLA Microsystems Ltd         Microcontroller Specialists
PO Box 15-680                email: steveb@kcbbs.gen.nz
New Lynn, Auckland           ph  +64 9 820-2221
New Zealand                  fax +64 9 820-1929
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