[time-nuts] 60Hz extra PPS: got one
bill at iaxs.net
Fri Aug 10 16:17:20 UTC 2012
Hal, do you have a resonant 60 Hz filter in the pickoff? The waveform
in Aug-09-a1 certainly had multiple zero crossings.
Remote-controlled tap changers can do things like that.
If I got the UTC offset right, that happened at about 2 PM local time,
when a big transformer tap could have been changed for more A/C load.
I expect you'd rather do things in software, but the mechanical
solution is to couple a synchronous motor to a flywheel marked with
60 Hz lines for photocell pickup. A precision 33 1/3 rpm turntable
with strobe markings would work very well.
From: Hal Murray
Sent: Friday, August 10, 2012 3:51 AM
Actually, there were 2 extra pulses.
Here is the PPS view:
(Samples every 10 seconds.)
Here is the audio view:
(16 bit audio, 8 KHz)
I noticed a couple of other fishy areas:
They didn't confuse the PPS collector.
I'm probably overlooking lots of similar glitches. I only noticed that pair
because the first one happened at the bottom of a cycle and that was big
enough to stand out. I noticed the second one because it was close enough
the first one.
Anybody got software to emulate a PLL? I'm looking for something that will
track a sine wave and tell me when it finds noise.
I haven't seen any of the ground problems in the last day or so. I don't
know if that is just luck or if upgrading to Fedora 17 fixed something. (Or
maybe I accidentally fixed something.)
These are my opinions. I hate spam.
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