[sdiy] cute hand held scopes on eBay

[Neil Johnson]

Steve Maietta wrote:
> Thise "sine" waves look bad yes, but that's at 500Khz..  So for RF, okay its not going to work.. But perhaps for synth use they do a "good enogh" job?  For tuning circuits, trimming waveshapes etc??

The pictures on the webpage Rich linked to are quite astounding.
Sure, it might show you a wiggly line, but I wouldn't trust it any
further than that.  Definitely not for making any measurements.

Try observing the reset pulse from the comparator in a sawtooth VCO.
Its typically a few microseconds.  Say, the ASM-1.... should sit at
the negative rail, then up to 0V for a few microseconds while the
capacitor discharges, then back to V-.  You *might* see something with
this toy.  You might not.  Or something that you can't say whether is
correct or not.

Heck, even that 500Hz square wave on the review site -- what's with
the over/undershoot?  Is that in the circuit, the probe, or the scope?

> good S-DIY bench/pocket tool?

Not in my opinion.  A waste of money, unless you want it for some
artistic purpose.
Better save up and get a decent analogue scope and decent probes.  Or
if you need to capture occasional events or need to dump out dataplots
to a printer or a PC get a decent DSO.

This issue has been discussed on the list several times over the
years.  Rigol and OWON seem quite popular.  Or be lucky on eBay or a
reseller for a second-hand Tektronix or HP/Agilent.

Cheers,
Neil
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