[time-nuts] 60Hz zero-crossing

[Don Latham]

OK, I wasn't paying attention as the info passed by. 'Xactly how is this
huge signal introduced to the PC? I remember something about a voltage
divider off the hot side of the line, put on an input pin of the PC's
com port and then somehow timestamped and put on a data file. Howsat
done again? Sorry to be so lame, but I really wasn't paying attention.
Don

Chris Albertson
> On Sun, Jul 3, 2011 at 8:57 AM, Tom Van Baak <tvb at leapsecond.com> wrote:
>
>>
>> At first this sounds a bit bold. I mean, there's lots of noise on the
>> power
>> line. Sometimes horrible spikes and all that. Surely, at some point a
>> cheap counting circuit is going to be confused.
>
> What makes is easy are two things
> (1)  the huge amplitude of the signal to be measured.  It's 120 (or
> 240) volts.  This just completely swaps out anything like EMI.
> (2) the frequency is so low that software has no trouble looking at
> every cycle in real time
>
>
> Chris Albertson
> Redondo Beach, California
>
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-- 
"Neither the voice of authority nor the weight of reason and argument
are as significant as experiment, for thence comes quiet to the mind."
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"If you don't know what it is, don't poke it."
Ghost in the Shell


Dr. Don Latham AJ7LL
Six Mile Systems LLP
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