[time-nuts] Second FTS4060 shows Drift, is it me? Good Links
Tom Van Baak
tvb at leapsecond.com
Tue Feb 7 14:15:18 EST 2006
Brooke,
> For the last couple of weeks it has shown a parabolic plot like s/n
> 1227, although this time the polarity is opposite that of s/n 1227 which
> also showed drift, but that may be a setup difference. A plot of s/n
> 1227 is at: file:///C:/Webdocs/pdf/Cs_Drift0429.pdf
This plot has both blue and red dots; which is which?
The red dots look like you should draw a line though
them, not a parabola. The linear slope is approximately
+700ns/21days = +4e-13, a perfectly reasonable value
of the frequency error in a Cs standard.
I see nothing wrong with the 3 weeks red dot data.
Let it go another month or two and see if it shows
parabolic behavior (frequency drift) rather than just
linear (frequency offset).
> The equation for s/n 1013 is:
> y = 2.7943x2 - 302.64x + 8969.4 and the quality of fit is
> R2 = 0.9088. The x-axis is in days and the y-axis is in ns.
> The first derivative of the equation has a first term of 2 * 2.7943 * x
> ns/day or +5.3E-14 seconds/seconds drift rate.
> Today's plot is at: file:///C:/Webdocs/pdf/sn1013_850_Drift2.pdf
I'm not sure I follow your math here; and frequency
drift rates don't have units of "seconds/seconds".
My eye tells me your frequency error (phase slope)
the first few days is about -25ns/day (-3e-13). The
last few days it is +25ns/day (+3e-13). The net change
in frequency is 6e-13 over a 10 day span so your
frequency drift is about 6e-14/day.
This is odd. It's way too low to be free-running quartz
(say 1e-9 to 1e-12 per day); it's even too low for Rb
(about 1e-10 to 1e-11 per month). Yet it seems too
high to be a correctly working Cs.
Do you have simultaneous M12+ plots of both S/N
1227 and 1013?
/tvb
http://www.LeapSecond.com
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