[time-nuts] Time Interval Measurement Hint

Tom Van Baak tvb at leapsecond.com
Tue Mar 8 14:28:19 EST 2005


Interesting clues.

What input triggering were you using for the SR 620
channels before and after the power cycle?

Do recall the approximate 4060 frequency offset
before and after power cycle?


----- Original Message -----
From: "Brooke Clarke" <brooke at pacific.net>
To: "Discussion of precise time and frequency measurement"
<time-nuts at febo.com>
Sent: Tuesday, March 08, 2005 10:51
Subject: [time-nuts] Time Interval Measurement Hint

> Hi:
> For a number of months I've been trying to get the C field set on a Cesium
standard.  This is a continuing learning experience.  In order to help in
setting the GPS elevation mask angle (now at 50 degrees) I started
monitoring a number of parameters, but now have stopped most of them except
for the standard deviation of the time interval.  I'm taking 1,000 readings
of the 1 PPS to Cesium standard 1 MHz zero crossing and the SR620 counter
provides not only the mean value but also the standard deviation.
> It turns out the the standard deviation is a great indicator that
everything is working correctly.  If this value gets to 40 nano seconds or
higher there's a problem.  Recently I tweaked the beam current on the
FTS4060 (open loop, center beam current, close loop) the green lock LED
turned on in a number of seconds, BUT the SDEV value was many hundreds of
ns!  Even after giving the FTS4060 overnight in the morning the SDEV was
still way high.  But unplugging the mains AC power for 15 seconds fixed the
problem, probably be resetting the micro computer.
> I highly recommend watching the SDEV value when making precision
> Have Fun,
> Brooke
> --
> w/Java http://www.PRC68.com
> w/o Java http://www.pacificsites.com/~brooke/PRC68COM.shtml
> http://www.precisionclock.com
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