[sdiy] How much DMM accuracy do you need?

[David Ingebretsen]

Thanks David. Point well taken. Necessity is the mother of invention. I
thend to think "in the box" far too often.

David

~~ -----Original Message-----
~~ From: David G. Dixon [mailto:dixon at interchange.ubc.ca]
~~ Sent: Wednesday, October 07, 2009 1:26 PM
~~ To: 'David Ingebretsen'; 'synth-diy'
~~ Subject: RE: [sdiy] How much DMM accuracy do you need?
~~ 
~~ > For guys like me who are
~~ > musically challenged (I know, a weird hobby for one with little musical
~~ > talent/skill) it's the best (maybe only) way to tune. For this, you
need a
~~ > high count meter that will give you sub-milivolt precision and accuracy
in
~~ > the +/- 5.0000 volt range.
~~ 
~~ Not true!  If you have a reasonably accurate CV keyboard and one other
~~ oscillator which can keep oscillating at the same frequency for more than
~~ five minutes at a time, then that's all you need to tune.  Well, that and
a
~~ scope with at least two channels.  Eliminate the relative motion of the
two
~~ waves on the scope at two different octaves in the low frequency range
~~ (100's of Hz), and you're tuned.  Repeat the performance in the high
~~ frequency range (1000's of Hz) and your HF trimmed.  This may require
some
~~ iteration.  The advantage of this method is that you end up tuning to
your
~~ keyboard, which may not be generating exactly 1V/octave, but will at
least
~~ drive your oscillator in tune.
~~ 
~~ (Bring on the flames...)