[sdiy] frequency counter

[James Patchell]

I have been working off and on to build something to characterize 
VCO's...trouble is, I have not given it too much priority.  And it wouldn't 
be a frequency counter...more like a virtual strobe tuner...(I know, there 
are tons out there you can buy)...but my instrument would include a MIDI 
interface, and a DAC output and would enable my to write a program that 
runs on my PC to automate measuring the VCO tracking, of every note.  Right 
now, I generally just check OCTAVEs, usually C1, C2, C3, C4, C5, C6 and 
C7.  It is time consuming enough just to do that (I do it more than once to 
make sure I took correct readings the first time....repeatability in 
measurements in very important).  But, alas, it may be some time before I 
get around to doing this....I was even thinking of scrapping what I am 
doing right now an implementing it in a Spartan 3....but...nah....

At 12:29 PM 6/27/2004 +0000, harrybissell wrote:
>Ian Fritz wrote:
>
> > I won't argue with you, but could you just say what is wrong with using a
> > counter?  It's what I've always used, and it certainly *seems* to work.  In
> > what sense doesn't it work?
> >
> >
>
>I'm one of those who question the usefulness of the frequency counter. I use
>a musical tuner, sine wave generator, scope (lissajous)... and my ears as 
>a final
>
>QC check.
>
>I set the sine wave generator to a midrange reference frequency. Use the 
>Tuner to
>check
>the reference... then use the lissajous patterns to take it from there.  The
>lissajous patterns
>are very similar to a strobe tuner... it is a matter of pattern 
>recognition from
>then on.
>
>I think that freq counters are too hard to intrepret (sure they're OK for 
>A=440).
>And too
>slow to settle to reasonable precision.
>
>oh... and mine is broken :^P
>
>I would like a frequency counter to determine the linearity of an unknown VCO
>design... lissajous
>patterns don't help much.
>
>H^) harry

         -Jim
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