[sdiy] Pocket oscilloscope

[Andre Majorel]

On 2014-09-13 07:42 +0100, gordonjcp at gjcp.net wrote:

> If you're looking for an oscilloscope at a budget-sensitive
> price, pick up a nice old dual-trace analogue 'scope from
> someone near you.  Look on eBay, search "nearest first" and
> when you find one ask if they'll show you how to use it if you
> don't know how it works or if they'll let you try it out if
> you do know.
> 
> It'll cost about as much as a decent Chinese takeaway for a
> perfectly adequate 25MHz-ish 'scope that'll do everything you
> could possibly need.

Except deal with slow signals. How do you look at an LFO or EG
shape on an analogue scope ?

On recent digital scopes, saving traces is a simple job. On an
analogue scope, you first have to 1) take the camera out, 2) set
it up on the tripod, switch to macro, 3) disable the flash,
4) enable the remote, 5) frame the picture, 6) try to match
exposure and sweep rate (often impossible without uncalibrating)
and 7) find a good combination of ambient light and trace
luminosity. And of course you'd better write down the horizontal
and vertical settings because they won't be on the photo.

For me, the choice between a cheap analogue scope and a cheap
digital scope is far from being a no-brainer as it seems to be
for you.

> My HP quad-trace 100MHz DSO sits with a thick layer of dust on
> top and my Iwatsu 20MHz analogue is pretty much never switched
> off, even working on RF stuff...

I'm curious. In what ways is the HP worse than the Iwatsu ?

-- 
André Majorel http://www.teaser.fr/~amajorel/