Danny Vacar wrote:
> Just wondering if you had some suggestions of manufacturers and models of
> Oscilloscopes which are not too expensive (i.e. less than US $400).
>   
I'm a big fan of eBay.  Of course, you have to know what you're looking 
for, and have to watch for bad sellers - although with several hundred 
transactions under my belt I think I've only been bitten once.

You need to know what scopes you like and what you don't.  This is more 
of a what are you familiar with and what do you need.  I'm a Tek fan 
myself and don't like HP/Agilent.   I know people who are the other way 
around (HP scopes work for them, Tek's don't).   You will also probably 
need to decide on whether you need a Digital Storage scope or can use 
analog one. 

A year or so ago I had an occasion to need my scope on the workbench.  I 
was needing to dermine the pulse width of a signal which only occured 
once a second (and which I now know is only about 150us in length).  
Took out my trusty old 20Mhz Tenma analog scope.  Fired it up, set the 
trigger up, turned off *ALL* the lights, cranked up the brightness all 
the way to hopefully charge the raster up enough for me to be able to 
see the pulse in the "afterglow" and watched the signal.   Wasn't able 
to get a reliable pulse width reading.  A guess, but not a reliable answer.
Knew it was time to buy a DSO.

So I went digging on ebay.   Browsed the Oscilloscope category, and 
selected digital and looked at all of the items.   For each I:

1) Dug around on the internet to get the real specs
2) Found a closeup picture of the front panel and/or found an 
instruction manual to make sure the operation made sense to me.
3) Made an educated guess.

I ended up buying a Tektronix 2230 a while back off of ebay for a couple 
hundred bucks.  and have been happy with it.  Looks like a couple of 
these have sold recently for around the same $200 or so.   This is a 
100Mhz DSO.   This is an older technology scope which is roughly at the 
age that I'm familiar with, so it was a logical choice for me.    There 
are a few warts (which I'll get to below).

I will say that I had basically moved the analog scope off of the bench 
since It was little use to me with digital work at the duty cycles I 
often work with (very brief events, occuring fairly rarely).  The DSO 
has let me see non-repetitive waveforms like never before.  I don't 
think I'll ever buy a non-DSO scope again.

The main "wart" with the 2230 is the fact that you can only go down to 
10us/div in chop mode and 5 us/div in alt mode when sampling.  This has 
to do with the maximum sample/storage rate.  However, this isn't that 
bad since when you turn on 10x, you really get about 1us/div in chop 
mode.   Plus, if the waveform is repetitive, you can go much better than 
the 5us/div.

I would buy another 2230 (and probably will).  I'm also wanting to get 
one of the small "lunchbox" TDS  units for when I travel to a client site.

-forrest
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