[time-nuts] EFC tracking

Hal Murray hmurray at megapathdsl.net
Sat Jun 26 15:40:01 UTC 2010

[voltage-to-frequency converter]

> I just had one of those duh! moments :) It does make the sampling a little
> more complicated as I'd have to take a number of samples and do something
> like a FFT to get the frequency, I think. My idea seemed just a simple way
> to just make a single, or limited number, of sample(s) and I have the data.
> Still, this is a good idea and I'll have a good thunk about it. 

How many bits of resolution do you want?

A FFT chops the energy into buckets.  To get smaller (narrower) buckets you 
need more samples.  But 16 bits is only 64K samples...  No big deal if you 
are working on a real PC but it probably won't fit into a tiny micro.

There is probably some simple way to move things around but I can't work it 
out on the fly.  It's something like use every Nth sample.  Your signal will 
get aliased down to the wrong place but since you know (roughly) where it is 
you can correct for that.  (Radar geeks to this sort of thing all the time.)

I'd look into something like scanning for zero crossings.

These are my opinions, not necessarily my employer's.  I hate spam.

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