[time-nuts] 60 Hz frequency and phase measurement

[jimlux]

On 7/3/19 8:56 AM, Tom Van Baak wrote:
> Bob,
> 
> Several of us do long-term measurement of mains frequency. We tend to 
> time-stamp cycles and then compute period or frequency, rather than 
> measuring frequency or period directly. Traditional counters in gated 
> frequency or time interval mode have dead time and this will skew results.
> 
> In my case I just run a 5 VAC wall-wart through a 10k resistor directly 
> to the input pin of a PIC. No scaling, no filtering, no opto, no ZCD, no 
> nothing. If I measure every cycle I get 155 million samples per month. 
> If I extract one cycle each second (decimate by 60) it's only 2.5 
> million samples a month. Many months there is not a single glitch in the 
> data in spite of all the FUD about power line noise. Once in a while a 
> month contains an extra or missing sample but the beauty of timestamp 
> data is that this can be detected and repaired as part of data 
> processing with no loss of phase.
> 
> Here's a page where Kevin (in New Mexico) and I (in Seattle) both used 
> picPET's to measure mains for a few days and then we compared the 
> results. Although thousands of miles apart, we're both on the same grid 
> so the agreement was astonishing. It was milliseconds in time and ADEV 
> down to e-8 over a day:
> 
> http://leapsecond.com/pages/mains-cv/
> 
> See also: http://leapsecond.com/pic/mains-adev-mdev-gnuplot-g4.png
> 
> /tvb


yes indeed

http://fnetpublic.utk.edu/anglecontour.html shows a pretty constant 
phase shift of tens of degrees.

(except Texas, because, after all, they're Texas)