[time-nuts] Recording mains frequency/phase [WAS: No GPS satellites]

Philip Gladstone pjsg-timenuts at nospam.gladstonefamily.net
Fri Feb 27 15:46:35 UTC 2015


On 2/26/15 20:39, Charles Steinmetz wrote:
> ben wrote:
>
>> I'm going to have to build one of these. Assume you have some sort of
>> circuit that converts low-voltage AC from a transformer secondary to
>> a pulse train, start a timer, and count x amount of pulses?
>
> Here is a zero-cross detector designed for this purpose:
>
> <http://www.ko4bb.com/manuals/download.php?file=02_GPS_Timing/Simple_AC_Mains_Zero_Crossing_Detector.pdf>
>
>
> Most mains-nuts feed the ZCD pulse to the DCD line of a PC's RS232
> port and use the computer to time-stamp the crossings and append them
> to a file of such time stamps.
If we all did this, then I realize that we could identify the different 
power grids. However, I wonder if there is any interesting variation 
*within* a grid. As the electricity flows vary throughout the day, it 
seems possible that the phase difference between two people on the same 
grid would actually change (a bit).

Has anybody done this experiment?

Philip



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