AW: [sdiy] Looking for info on freq. counters (SDIY-compatible ;)

[Czech Martin]

One of my first things I soldered in life was a frequency counter
with some Intersil IC (man, I was 16 or so..., this IC was
so darn expensicve then, my hands were wet when I turned
the PSU on, and then the first digit appeared....).

It still works like a charm. Even the simplest counter can do period
time measurements, with that and a calculator you can tune
your vco's as fast and precise as you can.
Basically this means exchanging reference clock and gate input.

I can only recommend the microcontroller counter kit
from www.elv.de , which does automatical reciprocal measurement,
as long as this is more precise as direct counting.
Very nice and cheap kit.

{
The other question is if "mathematical" correct tuning is
desired and why, but this is another story...
}

btw.: does somebody know the frequency tolerance of 
our mains supply here in Europe? I think that the network
is very large, covering serval countries, this means
a very large "flywheel", so I expect the average frequency
to be very stable (another pll application, flywheel).
I heard that the TV line frequency is also very stable.
Would it be possible to derive a time standard from that?


m.c.

> -----Ursprüngliche Nachricht-----
> Von: patchell [mailto:patchell at silcom.com]
> Gesendet: Mittwoch, 5. September 2001 06:26
> An: l'es chupacabra
> Cc: synth-diy at dropmix.xs4all.nl
> Betreff: Re: [sdiy] Looking for info on freq. counters 
> (SDIY-compatible
> ;)
> 
> 
>     The problem with a standard frequency counter is the 
> amount of time it takes
> to make a measurement.  Let's say you want to measure 100Hz 
> to 0.1%.  To do
> this, it will take 10 seconds with a standard frequency 
> counter.  The reason for
> this, is that the 100 Hz clocks a counter, and to measure to 
> .1% you need 1000
> counts, which will take ten seconds to aquire.
> 
>     Fancier counters, which are smart, will measure the 
> period and then
> calculate the frequency by taking the reciprocal.  These can 
> be much faster.  At
> 100Hz, you can make a measurement every 10mSEC.  However, the 
> downside is that
> any phase jitter on the incoming signal will make the display 
> noisy.  So, a lot
> of the fancier counters also average over many 
> readings....anyway, it starts to
> get pretty complicated, and you trade one thing off of the other.
> 
>     After I got my Conn Strobe Tuner, tuning was so much 
> easier.  Like I said,
> you got an instant display of any change in pitch.  Tuning 
> was a snap with that
> thing....I really miss mine <sniff>.
> 
> l'es chupacabra wrote:
> 
> > Question - what are frequency counters good for if not 
> tuning/calibrating
> > VCO/LFOs?  I've seen statements like yours before and 
> always wondered.  I've
> > got to pick up a multimeter pretty soon and wondering if 
> it's worth it to
> > narrow the search to one that includes a freq. counter.
> >
> > Thanks,
> >
> > JP
> >
> > > Don't want to discourage you from getting a frequency 
> counter, but, your
> > > normal run of the mill frequency counter is probably not 
> the best thing to
> > > tune VCO's with.
> > >
> 
> --
>  -Jim
> ------------------------------------------------
> * Visit:http://www.silcom.com/~patchell/
> *-----------------------------------------------
> *I'm sure glad Merry Christmas comes just once a year
> * -Yogi Yorgensen
> ------------------------------------------------
> 
>