[sdiy] cute hand held scopes on eBay

[David Evans]

On 23 Feb 2012, at 17:45, Neil Johnson wrote:

[ out of order for clarity ]

> 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?
> 

Wow, that is terrible and nothing like what I've seen. Had I this experience I'd have not much good to say about the thing. However, this photo illustrates how bad it is for some!

> 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.
> 

I think that a "wiggly line" is a bit uncharitable. I've used it for frequency/period measurements and it's worked well for that.

> Try observing the reset pulse from the comparator in a sawtooth VCO.
> Its typically a few microseconds.

Yeah, that sort of thing might lead you into trouble.

> 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.
> 

Always good advice.