[time-nuts] TEC party file format?

Tom Van Baak tvb at LeapSecond.com
Wed Jun 29 19:28:46 UTC 2011


Mark,

That will work fine. In your data I see 124 measurements taken
over half a minute and you're getting about 14 or 15 counts per
measurement, each one is about 1/4 second. Your PC-based
time-stamps allow you to mark the time of each measurement
(or compute interval between N measurements).

There's a hiccup at line 82 and 84 that you might want to debug.

If you subtract the first from the last point you get a nice result:
   delta counts: 1781 - 8 = 1773
   delta time: 29.578 seconds
which gives 59.94 Hz average frequency during that half minute.

If you write a couple lines of code you can take the data as it's
being collected, break it into, say, 1 minute or 10 minute chunks
and plot how frequency varies minute to minute.

To calculate time error, take the (presumably NTP sync'd) PC time
delta, multiply it by 60 to give the number of cycles you *ideally*
expect during that interval. Subtract that from the number of cycles
you *actually* count during the same interval and that's how many
cycles were gained or lost.

If you then plot that over time (especially over several days) you
will be impressed at how well the power company does keeping
TE within a few seconds of zero.

/tvb

----- Original Message ----- 
From: "Mark Spencer" <mspencer12345 at yahoo.ca>
To: "Discussion of precise time and frequency measurement" <time-nuts at febo.com>
Sent: Wednesday, June 29, 2011 9:55 AM
Subject: Re: [time-nuts] TEC party file format?


I thought I would try simply feeding a 60 Hz signal from the AC line into a 
counter in totalize mode and logging the output several times a second with time 
stamps. I'll be curious to see how accurate this is.

I've attached a small sample of the data.



----- Original Message ----
From: Tom Van Baak <tvb at LeapSecond.com>
To: Discussion of precise time and frequency measurement <time-nuts at febo.com>
Sent: Wed, June 29, 2011 7:53:43 AM
Subject: Re: [time-nuts] TEC party file format?

Chris,

Sounds good. Somebody that's interested or knows NTP (not me)
can be the first to set up a mains frequency timed PC, publish
fancy MRTG plots on the web, and watch the TEC test in July.

Realize this is all just for fun. TEC should have zero impact on
modern computer networks. The last system I worked with that
relied on 60 Hz power for timekeeping was a 70's PDP 11/34.

/tvb

----- Original Message ----- From: "Chris Albertson" <albertson.chris at gmail.com>
To: "Discussion of precise time and frequency measurement" <time-nuts at febo.com>
Sent: Tuesday, June 28, 2011 4:06 PM
Subject: Re: [time-nuts] TEC party file format?


The Linux or BSD pulse per second interface is general enough to work for this.
It does not care if the pulses are one per second or 100 per second, or 60.

Al it does it capture a timmer/counter when a pulse comes in. Then
fets a flag a user program can read that says "data available". The
user level programs reads the device ad gets the captured counter
value, the flag is reset. Very simple and very low overhead.

I think the counter units are nanoseconds



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