I've been using o-scopes for over 30 years, and feel kind of lost without
one around.  For most of that time, they've been analog because that was the
only kind available.

For the last year, I've been using one of the cute little Tek LCD scopes,
and I love it.  But sometimes you have to remember that it's not really the
same thing as an oscilloscope.  It's really an A/D converter, some memory,
and a display.  Sometimes they're equivalent, and sometimes they're not.

For digital signals, there's no way an analog scope can compete with a
storage scope for utility and ease of use.  Digital signals tend to be
one-shot things, or else have long sequences that don't repeat very often.
Storage of one-shot events and the ability to set a trigger that causes a 1
mS sample to be taken 100 mS later are incomparably better than trying to
get the event to repeat often enough to make a visible picture on an analog
scope.

For analog signals, you have to CLEARLY understand the fact that you are
looking at the output of an A/D converter with no anti-aliasing filter in
front of it.

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.

> -----Original Message-----
> From: Wagner Lipnharski [mailto:wagner@USTR.NET]
> Sent: Friday, April 07, 2000 8:57 AM
> To: PICLIST@MITVMA.MIT.EDU
> Subject: Re: LCD Osciloscope
>
>
> LCD technology is basically slow, so for high frequencies they are
> forced to work with memory. The customer thinks it is an advantage to
> have memory or delayed display, but in true there is no other
> way to do
> that.  You can't possible "see" a 50 MHz signal in real time on a LCD
> screen.  Steve, to mess with your words, I would change the phrase "OK
> (specially lower frequencies)." to "OK (only in lower frequencies)"...
> :)  In the high frequency real time world there is nothing that can
> substitute (until now) the good and old CRT, I am wrong?
> Wagner.
>
> > "Kosmerchock, Steve" wrote:
> >
> > Mark,
> >
> > 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
> > the schematic in the back. You might beable to download it from
> > their website. If not let me know and I'll dig mine out and
> > make a copy and either EMAIL it or FAX it.
> >
> > Best regards,
> > Steve
> >
> > Steven Kosmerchock
> > Father/Student/Engineering Technician
> > www.geocities.com/researchtriangle/lab/6584
> >
> > "Great spirits have always encountered violent
> > oppposition from mediocre minds."--A.Einstein
> >
> > -----Original Message-----
> > From: mark templeman [mailto:marktempleman@FSMAIL.NET]
> > Sent: Thursday, April 06, 2000 2:11 PM
> > To: PICLIST@MITVMA.MIT.EDU
> > Subject: LCD Osciloscope
> >
> > Does anyone know of any circuits for a reasonable quality
> > Oscilloscope based around an LCD graphics display
> >
> > Regards
> >
> > Mark Templeman
>