Don Hyde wrote:
.....
>For instance, if you have a digital o-scope that stores 1000 samples, and
>you set up the horizontal display so that those 1000 samples represent 1 mS,
>then you are looking at an A/D converter that's running at 1M
>samples/second.  If you feed in a 1KHz sine wave, you will get a nice pretty
>sine wave with one cycle across the screen.  If you feed in a 1,001,000 Hz
>sine wave, you will get exactly the same picture on your screen, thanks to
>aliasing.

This is why, if you buy a d'scope, you want to look for one that has
a "glitch" or "envelope" feature, where you can push a button and quickly
see if aliasing is occurring. These features sample continuously at high
rate (say, 1 Msps) and display max/min over a period (say, 1 msec), rather
than just one sample every 1 msec.

Besides, with sampling, it's always a fun challenge to try to figure
out whether what you see is real or imaginary. [keeps those brain cells
clicking].
===================

Wagner Lipnharski wrote:
.....
  In the high frequency real time world there is nothing that can
>> substitute (until now) the good and old CRT, I am wrong?
>> Wagner.
>>

[Boy, you can always spot an old dyed-in-the-wool analog type].

Wagner, you're no doubt alluding to the fact that a sampling scope
would have to sample 10X or so per period of the "fastest" frequency
in a signal to produce a reasonably good "time-domain" reproduction.
Roughly speaking, the d-scope equivalent of a 100 Mhz a'scope would
have to sample at 500-1000 Msps. This is a real problem.

The difference is $800 -> $1000 for the a'scope and $5000 -> $10000+
for the equivalent d'scope. There are such things as sineX/X
reproduction of sampled signals which allow slightly slower sampling
rates, but the speed & complexity are still problems.

There are "CRT substitutes" today, from HP and Tek, etc, but they
sure ain't cheap.
================

Mark Templeman wrote:
.........
>> Does anyone know of any circuits for a reasonable quality
>> Oscilloscope based around an LCD graphics display

Steve Kosmerchock wrote:
....
>I know Velleman ( www.velleman.be ) makes a small O-SCOPE
>using a PIC16C65 and a 240x64 graphics LCD. I own one,
>works OK (especially lower frequencies). The users manual has
>

Jim Newton has references to this kind of project on Techref
somewhere. However, despite what Velleman and others call
"high-res" displays, their LCDs really have pretty poor
resolution for graphical data display. 128x64 pixels or so is
pretty bad, 320x128 is fair, but need to go higher (also more
$$$$) for good quality.

best regards,
- Dan Michaels
Oricom Technologies
http://www.sni.net/~oricom
==========================