[time-nuts] 60 Hz data

Hal Murray hmurray at megapathdsl.net
Thu Jun 30 09:36:03 UTC 2011

Tom's suggestion of using a modem control signal is a winner.

Here is a graph:
Hour 0 is the start of Jun 30 UTC, 5PM PDT.

It's gained almost 200 cycles over 9 hours.  There are enough wobbles in 
there that I think the data is good.  It will be interesting to see what the 
rest of a 24 hour slot looks like.

I'm in California.  Does anybody in the same power grid have data that looks 
similar?  (or different?)

Here is the same data plotted as frequency measured over 10 seconds.
There is a lot of noise.  I don't know how much is on the line and how much 
is jitter in the capture system.  (I'll have to think about that tomorrow.)

I'm sampling every 10 seconds.  If it picked up an extra cycle, the frequency 
would be 60.1 Hz.  There is one data point (about 4 hours) that's in that 


I'm using a wall wart transformer.  It's nominally 12V RMS but I measured 16V 
no load.  I used a couple of 1K resistors as a divider.

I'm using the Linux PPS stuff.
  [murray at jim 60Hz]$ cat /sys/class/pps/pps0/assert
  [murray at jim 60Hz]$ 
and a python hack to write stuff to a log file.

Here is a log file if anybody wants to play:

First two columns are MJD and seconds this day copied from NTP's log file 

3rd column is unix time stamp of most recent event.  4th column is number of 
events since ???

5th and 6th columns are delta time/count since the previous line (10 seconds 

55742     4.259  1309392004.255156 232038  10.014635    601
55742    14.270  1309392014.267448 232639  10.012292    601
55742    24.281  1309392024.279595 233240  10.012146    601
55742    34.291  1309392034.275325 233840   9.995730    600
55742    44.298  1309392044.287679 234441  10.012354    601
55742    54.309  1309392054.299189 235042  10.011509    601

The first graph uses columns 2 and 3.
The frequency graph uses columns 5 and 6.

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

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