[time-nuts] New 4 hints from Agilent?

jim_johnson at agilent.com jim_johnson at agilent.com
Tue Dec 14 16:45:33 EST 2004


Aging is a very complex issue and is caused by a lot
of things.  A helpful paper was written by Vig and
Meeker and I've grabbed couple of paragraphs from that
paper and have included them below.  In particular, for
the SC-cut crystal (HP/Agilent 10811), the aging is
reduced considerably over that of "cheap" crystals.
However, it does not go to zero and that is reflected
in the 10811 aging spec of 1E-7/year (continuous operation).
Also there are other things in the 10811 that age and
cause frequency shifts, other than the crystal.  Here
are the two paragraphs from Vig (the URL for this paper
is: http://www.ieee-uffc.org/freqcontrol/vigaging91/aging.htm#CONTENTS )


Proceedings of the 45th Annual Symposium on Frequency Control,
pp. 77-101, 1991

THE AGING OF BULK ACOUSTIC WAVE RESONATORS, FILTERS AND OSCILLATORS

John R. Vig and Thrygve R. Meeker


"The aging rates of typical commercially available crystal oscillators (in 1991) range from 5 to 10 ppm per year for an inexpensive clock oscillator, to 0.5 to 2 ppm per year for a TCXO, to 0.05 to 0.1 ppm per year for an OCXO. The highest precision OCXOs can age less than 0.01 ppm per year."

"These properties are probably the reason for the fact that the aging of the best long term aging AT-cut resonators with gold electrodes is about the same as that of the best SC-cut and BVA resonators, i.e., a few parts in 10^12 per day. That the initial aging of the best SC-cut resonators is better than that of the best AT-cuts [49,50] is probably due to the superior insensitivity of the SC-cut to some important types of stresses, such as the stresses due to the electrodes."

Jim W6SC


>-----Original Message-----
>From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com]On
>Behalf Of Brooke Clarke
>Sent: Tuesday, December 14, 2004 11:54 AM
>To: Discussion of precise time and frequency measurement
>Subject: [time-nuts] New 4 hints from Agilent?
>
>
>Hi:
>
>Agilent has AN1499 where they make the case that leaving a 
>counter on all the time improves the time base stability by 
>more than an order of magnitude, but the numbers shown on page 
>3 seem to indicate that it gets worse.  I expect that the 
>numbers are a typo.
>
>They also make the case that the counter should be calibrated 
>in place so that power is not cycled.
>http://cp.literature.agilent.com/litweb/pdf/5989-1592EN.pdf
>
>Have Fun,
>
>Brooke Clarke, N6GCE
>-- 
>w/Java http://www.PRC68.com
>w/o Java http://www.pacificsites.com/~brooke/PRC68COM.shtml
>http://www.precisionclock.com
>
>
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