[sdiy] oscilloscope considerations

[Theo]

There are some nice affordable hybrids out there.
Check on the Goldstar OS-3060.
I found one under $800 new, but that was a bargain.
Or check on the  Voltcraft scopes, good and real bang for the buck.

BTW, I found having a storage function very helpful when working with
slowly changing voltages, like EGG or LFO. Highly recommended.

Theo



From: harry <harrybissell at prodigy.net>

> RE: Analog vs Digital scopes
>
> Both have their place. If I could afford it, my first choice would be the
> Analog
> Digital Hybrid such as a Fluke Phillips model I use at work. It was in the
$10K
>
> range... a little too pricey for me.
>
> The big advantage is being able to see both the pure analog signal
(without all
> the
> fancy tricks) and then switch to digital.
>
> Digital scopes can Alias... the too-low sample rate can make signals
appear
> that
> do not exist... often fooling newbies (and experienced engineers alike) to
> think
> they are looking at (let's say) a 20KHz waveform when in reality its an
> undersampled
> 200KHz waveform.
>
> Another nasty digital trick is what happens when you view "noise" such as
white
>
> noise. The "all-frequency" content of this wave almost guarantees it will
alias
> and
> display trash !  Because you are sampling at a regular rate... you can get
> fooled easily
> into thinking you are seeing a periodic waveform, when you are not.
>
> That said... I'm considering a digital such as the low-end Tektronix
($1.5 - 3K
>
> price range).  I'm just afraid that the LCD display speed (slow) will
really
> piss
> me off.  I'm also afraid that the toy will break in a few years (like 3-5)
and
> be
> unrepairable due to lack of parts.  Older analog scopes can last 20 years,
> easily...
> until the CRT decays to the point of darkness  (the equivalent of having a
> slower
> and slower scope)
>
> Maybe those who have some more change might want to have two scopes. I've
been
> doing a quantizer lately... and the triggering on my analog scope sucks...
and
> two
> channels is not enough for my spoiled @ss !!!
>
> I'd say... If I had to have only one scope, It would be an ANALOG storage
> scope.
> I could live with that (even used...).  I'd go for no less than 60MHz for
DIY
> work
>
> H^) harry
>
> media at mail1.nai.net wrote:
>
> > I know many people on this list frequently suggest buying a used
> > oscilloscope from Ebay, Nuts & Volts, and a Ham flea-markets.  The Ham
flea
> > market might not be a bad idea for me since Newington is less than two
> > hours from here.  However, I'm considering buying a new scope for two
> > reasons.  Firstly, I'm not familiar with all of the makes and models,
and
> > do not know which features each model has, or its fair market price.
> > Secondly, I want to make sure that it is calibrated and working
properly,
> > as fixing an oscilloscope without an oscilloscope would seem impossible.
> > So waiting for a dealer to blow out an older model might be my best bet.
> >
> > Is there a FAQ or website that discusses features of various scopes??
The
> > manufacturer websites haven't been all that helpful as to what features
are
> > actually useful.  Nor could I find descriptions of scopes no longer
being
> > made.
> >
> > 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.
> >
> > There seem to be four types of digital scopes: digital scopes with LCD
> > displays (eg. Tektronix TDS210), digital scopes with CRT displays,
digital
> > scopes with CRT displays that claim to have an "analog" mode (eg.
BK5020),
> > and expensive scopes from Tektronics called Digital Phosphor
Oscilloscopes
> > (DPO) that have VGA color LCD displays that supposedly imitate the
display
> > characteristics of analogue scopes.  I cannot afford a DPO, but the
digital
> > scopes with either monochrome CRT or monochrome LCD screens seem
> > competitively priced.  Any ideas here??
> >
> > 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.
> >
> > 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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