[sdiy] How much DMM accuracy do you need?

[Dave Manley]

no flames! :-)

the xy scope method works great, but the
exact same process works by tuning for zero
beats between the reference and the vco
being tuned. no test equipment required.

David Ingebretsen wrote:
> 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...)