[sdiy] oscilloscope considerations

[Jim Patchell]

media at mail1.nai.net wrote:

> 
> Prices range from an Instek 5MHz analog scope for $235, to digital scopes
> costing over $16K!!  While I do not think I need a digital scope, that
> seems to be the way things are going, as a number of manufacturers no
> longer make analog scopes.  What is the real advantage of an analog scope??
> The problem with anything digital is not so much the price, but that it
> doesn't hold its value -- digital technology keeps getting faster and less
> expensive every year.

   When I purchased the scope I am using right now, I just purchased a 
cheap 20MHz analog scrope (from Jameco), I think I paid $400 for it, and 
it works perfectly fine.  At work, on my bench, I have a Tektronix 
TDS-724A, which is on the other end of the spectrum.  Now, the TDS-724A 
is a very nice scope, however, it do lie to me on a regular basis 
because it does alias.  The newer Tek scopes have a feature called 
digital phosphor, which really helps with this problem, but, even they 
ocasionally lie.  Personally, if I were you, get the scope you can 
afford.  I wish sometimes my $400 scope had certain features, like the 
ability to trigger on channel two, but to tell you the truth, I would 
rather be using my $400 scope debugging analog synths as opposed to the 
TDS-724A I have at work.

   This is one of the advantages of getting a used scope, however.  For 
the same amount of money, you can get all those nice features, which 
does have to weighed against the posibility you might have to sink more 
money into your new aquisition to bring it up to par.

> 
> Another consideration is bandwidth.  I'm thinking that 20MHz would be fast
> enough for sdiy, but I have heard many people say that 20MHz scopes should
> be avoided.  Why is that??   As far as digital scopes are concerned, sample
> rates also vary.  I would think the two would be related, but there doesn't
> seem to be a correlation in any of the specifications.  Also, there is no
> mention of resolution (ie. bit depth), which strikes me as very odd for an
> instrument that measures voltages against time.

   More bandwidth is good, get as much as you think you can afford.  
20MHz, in general, is more than adequate for Synth-DIY

> 
> 
> Most of the digital scopes include communications ports or have them
> available as options.  Is there any sort of standard data format for
> oscilloscopes, or are you stuck with the software available for one brand
> of scope??  Several of the digital scopes also have software plug-in
> modules that add features, such as FFT.  I think FFT could be very useful.
> However, considering that the computer hardware is already there, there
> seems to be a lack of acoustic analysis software compared to what available
> for the Techron and Goldline hardware.
> 
> Is there anything else I should consider??  Any brands I should avoid??
> 
> Finally, is there a dealer in the U.S. that anyone would recommend??  I've
> checked out Techni-Tool and Test Equipment Depot.  Tektronix also sells
> reconditioned units at a discount.
> 
> 
> THANX!! :)
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