Date   : Sun, 24 Jan 2016 22:41:33 +0100
From   : rick@... (Rick Murray)
Subject: Troubleshooting the BBC Mirco

"Are these hand-held Oscilloscopes any good"

In the digital domain you need to have an ADC that can sample at least five 
times the speed of the signal you want to examine. The fastest clock rate 
on a Beeb is 8MHz (although the system runs at 1-2MHz). So you'll need a 
40MHz digital scope to correctly see the 8MHz, or a 10MHz one to trace the 
processor activity. While a digital scope ought to allow features not available 
on analogue models, such as taking a snapshot of the waveform for later 
analysis, in reality the quality of the acquisition circuit and the number
of data points stored mean that the ability to examine signals may be little
more than a gimmick on lower end devices.

I recently discussed oscilloscopes on my blog and something that came to 
mind was that a typical non specialist digital model will have an eight 
bit ADC. While you might think having 256 levels would be suitable accuracy,
it is technically insufficient for capturing a correct view of a simple audio
CD passed through a good DAC. CD audio is 16 bit, the scope is eight bit...
It seems to me that while analogue can be limiting and not offer fancy features, 
it is a fairly "what you see is what you get", while there are many varied 
ways in which a digital oscilloscope can blatantly lie to you. So with that
in mind in not sure any of the lower end portable models are worth considering
for anything more advanced than basic fault finding.
That's not to say that all D(S)Os are bad, I just think one needs to understand
how it works to understand it's limitations.


Best wishes,?

Rick.?