In the second set it looks like the wrong input is being sampled at
times. Notice the offset is always the same. I have seen this happen a
lot with simple sampling programs. Even if this were real I doubt it
would cause false triggering of the clock. The pulse shown in the first
set would. When digital clocks are run off the power line they need
very good 60 Hz filtering as even a refrigerator coming on will cause
trouble.
David
On 9/1/12 3:31 PM, [email protected] wrote:
Perhaps a dumb question, but the wall wart is plugged into the wall, connected
directly to the grid? You aren't powering the wall wart through a UPS or some
type of inverter?
Tom
Sent from my HTC Inspire™ 4G on AT&T
----- Reply message -----
From: "Bill Hawkins" <[email protected]>
To: "'Discussion of precise time and frequency measurement'"
<[email protected]>
Subject: [time-nuts] 60 Hz line quirks, anybody recognize this stuff?
Date: Sat, Sep 1, 2012 11:42 am
Hal, where are you taking off the signal to the audio line?
At the low voltage wall wart or at the modem pin? - assuming
there's an isolation or dropping resistor.
I agree with others that the power company isn't doing this.
There would be inductive ringing. Can you confirm with another
wall wart going right to another audio channel? Or maybe a
real filament transformer instead of a wart.
Who knew you could find so much interesting stuff on the power
line . . .
Bill Hawkins
P.S. I think the mild flattening of the sinusoid peaks is
caused by saturation of the barely-enough-iron in the wart.
-----Original Message-----
From: [email protected] [mailto:[email protected]] On
Behalf Of Hal Murray
Sent: Saturday, September 01, 2012 1:35 AM
To: [email protected]
Subject: [time-nuts] 60 Hz line quirks, anybody recognize this stuff?
The context is using the 60 Hz line for timing.
I'm feeding 60 Hz from a wall wart transformer into a modem control signal
that the kernel PPS stuff watches. Mostly, it works as expected, but
occasionally, it picks or drops a cycle.
In order to understand what was going on, I fed the same signal into the
audio input and setup a job to capture the audio. Here is an example of a
pick:
http://www.megapathdsl.net/~hmurray/time-nuts/line/2012-Aug-09-a-pick.png
http://www.megapathdsl.net/~hmurray/time-nuts/line/2012-Aug-09-a0.png
http://www.megapathdsl.net/~hmurray/time-nuts/line/2012-Aug-09-a1.png
OK, that somewhat makes sense.
Something happened several days ago. I used to get picks/drops rarely, say
ballpark of 1 a month. Now I'm getting 10 or 20 per day. So I started
looking closer.
I'm now seeing stuff like this. I've got lots and lots of examples. I
added
a second PC with different hardware. It sees the same stuff.
Does anybody recognize this?
http://www.megapathdsl.net/~hmurray/time-nuts/line/2012-Sep-01-a0.png
http://www.megapathdsl.net/~hmurray/time-nuts/line/2012-Sep-01-b0.png
http://www.megapathdsl.net/~hmurray/time-nuts/line/2012-Sep-01-c0.png
http://www.megapathdsl.net/~hmurray/time-nuts/line/2012-Sep-01-d0.png
http://www.megapathdsl.net/~hmurray/time-nuts/line/2012-Sep-01-e0.png
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