Re: [time-nuts] Xtal Oscillator Aging
At Sunday, October 23, 2005 9:21 PM, Tom Clark wrote: > Going in the other direction, the mechanical resonant frequency > changes with time because, as the xtal vibrates, microscopic cracks in > the structure of the quartz break apart. Running at high power makes > the crystal generate these microscopic faults at a faster rate; this > then causes the oscillator to have poorer long-term stability. When an > xtal is left vibrating (oscillating) in an undisturbed environment, > the rate of cracking of the quartz decreases, and the oscillator is > said to "age" to its final frequency. > But if you subject that same crystal to a mechanical jolt will force > some new cracks and re-start the aging "diffusion" process. Ditto > turning the oscillator on & off or a thermal shock can aggravate the > aging. Could someone confim or deny an idea I posted some weeks before about ageing is more predictable on free running oscillators than in disciplined ones?. I read about it in a Simetricomm datasheet some time ago, but I would like to know experimental or theoretical explanation for that (or the contrary). Best regards Luis Miguel ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Xtal Oscillator Aging
In message <[EMAIL PROTECTED]>, "Rick Karlquist" writes: >I am not aware of any vertical testing, although the burn racks >may have been vertical. The end application had random orientation >and no one reported any orientation dependence. Well, that answers my question then: I must have overlooked something in the paper. I'll read it again :-) -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 [EMAIL PROTECTED] | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Xtal Oscillator Aging
Poul-Henning Kamp wrote: > > But did you test it both in horizontal an vertical orientation ? > I am not aware of any vertical testing, although the burn racks may have been vertical. The end application had random orientation and no one reported any orientation dependence. Rick Karlquist ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Xtal Oscillator Aging
In message <[EMAIL PROTECTED]>, "Rick Karlquist" writes: >BTW, the intended application was as a card in a VXI cage, etc. >Many of those cages have the card in a vertical orientation. But did you test it both in horizontal an vertical orientation ? -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 [EMAIL PROTECTED] | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Xtal Oscillator Aging
Good question. The internal insulation is foam, which should preclude convection (which is the only process which is gravity/ orientation sensitive. External convection should have negligible effect. We used to test these things in environmental chambers with big fans blowing air around and with drafts of evaporated liquid nitrogen blowing directly against them. The oven is so bulletproof that nothing you can do externally has much effect, even on a transient basis. It's hard to believe how good this oven is if you haven't seen it yourself. The double integrator in the control loop is awesome. BTW, the intended application was as a card in a VXI cage, etc. Many of those cages have the card in a vertical orientation. Rick Karlquist Poul-Henning Kamp wrote: > In message <[EMAIL PROTECTED]>, "Richard > \(Ric > k\) Karlquist \(N6RK\)" writes: > > Richard, > > I've browsed the E1398 papers and was left with one question which > I couldn't immediately find an answer to: > > Is the cylindrical design meant for use in one orientation only > (axis orthogonal to temperature gradient/airflow) or can it be used > in any orientation ? > > It seems to me that if the axis is oriented vertically, the temperature > gradient problem would apply to this design too ? > > > -- > Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 > [EMAIL PROTECTED] | TCP/IP since RFC 956 > FreeBSD committer | BSD since 4.3-tahoe > Never attribute to malice what can adequately be explained by > incompetence. > > ___ > time-nuts mailing list > time-nuts@febo.com > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > > ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Xtal Oscillator Aging
In message <[EMAIL PROTECTED]>, "Richard \(Ric k\) Karlquist \(N6RK\)" writes: Richard, I've browsed the E1398 papers and was left with one question which I couldn't immediately find an answer to: Is the cylindrical design meant for use in one orientation only (axis orthogonal to temperature gradient/airflow) or can it be used in any orientation ? It seems to me that if the axis is oriented vertically, the temperature gradient problem would apply to this design too ? -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 [EMAIL PROTECTED] | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
RE: [time-nuts] Xtal Oscillator Aging
At 22.20 26/10/2005, you wrote: Hi, I posed this question to Jack Kusters, now retired from HP/Agilent. He and Charles Adams commercialized the SC-cut crystal for HP in the 10811A oscillator. He gave me permission to post his response on the reflector. Jim Johnson [EMAIL PROTECTED] Jim and Jack, thanks for the post. Details of the production technology are always fascinating, at least to me. Marco ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
RE: [time-nuts] Xtal Oscillator Aging
Hi, I posed this question to Jack Kusters, now retired from HP/Agilent. He and Charles Adams commercialized the SC-cut crystal for HP in the 10811A oscillator. He gave me permission to post his response on the reflector. Jim Johnson [EMAIL PROTECTED] === Hi Jim, In addition to everything Tom Clark said (I agree in general with his explanation), there is another aging mechanism associated with stress. When the crystal blank is manufactured, it is sawn, lapped, ground, etched, and otherwise abused. All of this produces stress in the blank. In addition, there are mounting stresses that arise because of the way the blank is mounted on its header, surface stresses that develop because the electrode material when evaporated and then condensed on the surface shrinks as it cools. All of these result in long-term aging as these stresses need to equilibrate out. In addition, there are other stress related mechanisms that may result in either long- or short- term aging. The quartz material is anisotropic, the mounts, electrode material are isotropic. So, lets assume that we've had the crystal at an elevated, constant temperature. Over a period of time, all stresses, material, mount, electrode, cracks, etc. equilibrate to their lowest energy level and it appears that aging has stopped. Now, take it down in temperature. The anisotropic quartz and the isotropic mount and electrode, have different contraction rates, so the overall system now has a new set of stresses. Let the unit come to full equilibrium at the new, lower temperature. Now take it up in temperature to where it was before. Now we see a whole new set of aging and stress relief. The only virtue is that aging due to cracks and material stress from manufacturing processes should be mostly gone, so the unit should come to equilibrium much faster. One further comment, glass sealed crystals are not necessarily the best way to seal a crystal. It takes heat from a source sufficiently elevated in temperature to melt the glass. This tends to cause contaminents to migrate from the area being sealed to a cooler spot in the package, usually the crystal. Contaminents come from gasses from the torch or from junk trapped in the glass. The cleanest mount one can do is a cold-weld seal under proper conditions. For example, the HP crystals were put into a vacuum furnace, heated to 300+ deg-C overnite at 10E-7 torr with the can stored next to the crystal. After reducing the temperature to about 80-84 deg-C, the crystal was frequency plated to within several parts in 10E7. After that, the mount was placed in the can, the temperature raised up to about 150 deg-C, stabilised in temperature and vacuum, then cold-welded. Done properly, there is essentially no contamination inside the crystal assembly, most of the other stresses are gone, and the typical HP SC-cut would reach an aging rate of better than 1E-7 per day, within the first 5 days. Best regards, Jack Kusters == -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Tom Clark, W3IWI Sent: Sunday, October 23, 2005 9:21 PM To: time-nuts@febo.com Subject: [time-nuts] Xtal Oscillator Aging Brooke (no relation) commented Hi Richard: > > It's my understanding that this optimization can be done by changing > the oscillator power level at the crystal. > > In the case of the 32768 Hz watch crystal, it must be run a very low > power and it has a very low aging rate when compared to higher > frequency crystals that are typically run at higher power levels. I > think this is related to the crystal throwing off atoms, so more power > means more acceleration and more atoms thrown off. > > Have Fun, > > Brooke Clarke, N6GCE It has nothing to do with "throwing off atoms". A Xtal is actually a mechanical oscillator, with the quartz slab vibrating (in either its fundamental mode, or on an odd overtone); quartz is a piezo-electric material so the voltage across the pins of the xtal has a direct connection to the mechanical vibration. When an xtal oscillator starts up, the associated amplifier generates noise, which then starts the xtal vibrating, which generates signal at the right frequency and a feedback loop is set up. When you crank up the power to the mechanical resonator, the signal increases with respect to the background noise (i.e. S/N gets better) which improves the short-term stability. Going in the other direction, the mechanical resonant frequency changes with time because, as the xtal vibrates, microscopic cracks in the structure of the quartz break apart. Running at high power makes the crystal generate these microscopic faults at a faster rate; this then causes the oscillator to have poorer long-term stability. When an xtal is lef
RE: [time-nuts] Xtal Oscillator Aging
>It has nothing to do with "throwing off atoms". A Xtal is actually a This only happens in very low quality crystals that have impurities on the surface. >Going in the other direction, the mechanical resonant frequency >changes with time because, as the xtal vibrates, microscopic cracks in >the structure of the quartz break apart. Running at high power makes >the crystal generate these microscopic faults at a faster rate; this >then causes the oscillator to have poorer long-term stability. When an >xtal is left vibrating (oscillating) in an undisturbed environment, >the rate of cracking of the quartz decreases, and the oscillator is >said to "age" to its final frequency. The 10811 scientists agree that microscopic cracks are the main unresolved issue regarding crystal stability (there are many other possible issues, but they have been beat to death, at least in the top tier crystal fabs). OTOH, at HP we never saw any drive power related aging effects. The drive levels we used had some effect on the frequency (as shown in my E1938 paper) so we were limited because of that issue. Also, the g forces were so high that we couldn't go a lot higher without danger of losing the plating metallization. The effect on S/N ratio is such that you need a certain amount of drive to get a good noise floor at 10 kHz (which is only important in a minority of applications). Close in, the S/N ratio is determined by the quartz not the electronics, and running higher crystal drive doesn't help. It may even degrade short term stability. >But if you subject that same crystal to a mechanical jolt will force >some new cracks and re-start the aging "diffusion" process. Ditto >turning the oscillator on & off or a thermal shock can aggravate the >aging. At HP, we never saw any significant aging shift due to turning the oscillator on and off (while maintaining the oven at the same temperature). OTOH, it is definitely true that any oven temperature change will have a settling time effect on aging. >If the metal can or glass envelope around the xtal outgasses, some of >the resulting crud (a very scientific term!) from the envelope and >seal will deposit onto the quartz and also cause aging. For this >reason, only the cheapest crystals are housed in a metal can with a >solder seal; cold welding of the can is a much better procedure; and a >glass envelope is the best. Cheaper than cheap are the WW2 "FT243" Many decades ago, glass was the "gold standard". However, cold well metal cans have long since superceded glass. Rick Karlquist N6RK (formerly HP Santa Clara Division) ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Xtal Oscillator Aging
Brooke Clarke wrote: Hi Tom: This is the first I've heard about the cracks. Can you point me to some literature about it so I can do my homework. Thanks, Brooke Brooke -- My comment last nite was an attempted simplification/synthesis of Vig's topics --- here are some references: Vig is THE MAN WITH THE BIBLE <[1]http://www.ieee-uffc.org/freqcontrol/quartz/vig/vigtoc.htm>. Comments on the Quartz Crystal and how it works are in Section I at <[2]http://www.ieee-uffc.org/freqcontrol/quartz/vig/vigqrtz.htm>. Section III has relevant material on the aging process at <[3]http://www.ieee-uffc.org/freqcontrol/vigaging91/introduc.htm> Vig discusses all the mechanisms in <[4]http://www.ieee-uffc.org/freqcontrol/vigaging91/agingmec.htm#Aging %20Mechanisms.>. Note specially the sections on "Stress/Strain" , "Changes in the Quartz" and "Electrode Effects". Temperature effects on aging are discussed here: <[5]http://www.ieee-uffc.org/freqcontrol/vigaging91/temperat.htm#Tempe rature%20and%20Temperature-Cycling>. For a one-paragraph summary see the last paragraph of <[6]http://www.ieee-uffc.org/freqcontrol/quartz/vig/vigaging.htm> To back up my Power Level+S/N statements, see <[7]http://www.ieee-uffc.org/freqcontrol/quartz/vig/vignoise.htm> Vig's collected papers are $60 at <[8]http://www.stormingmedia.us/16/1688/A168823.html> There is also a good, old (1997, pre-Agilent) HP Application Note 200-2 which I found at <[9]http://my.ece.ucsb.edu/yorklab/Useful%20Stuff/Tutorials/QuartzCrys talOscillators.pdf> Agilent (post-HP) has a good discussion on Precision vs Accuracy, Aging etc at <[10]http://metrologyforum.tm.agilent.com/xtals.shtml>. Hope I didn't confuse people with my simplified, one paragraph explanations! 73, Tom Clark References Visible links 1. http://www.ieee-uffc.org/freqcontrol/quartz/vig/vigtoc.htm 2. http://www.ieee-uffc.org/freqcontrol/quartz/vig/vigqrtz.htm 3. http://www.ieee-uffc.org/freqcontrol/vigaging91/introduc.htm 4. http://www.ieee-uffc.org/freqcontrol/vigaging91/agingmec.htm#Aging%20Mechanisms. 5. http://www.ieee-uffc.org/freqcontrol/vigaging91/temperat.htm#Temperature%20and%20Temperature-Cycling 6. http://www.ieee-uffc.org/freqcontrol/quartz/vig/vigaging.htm 7. http://www.ieee-uffc.org/freqcontrol/quartz/vig/vignoise.htm 8. http://www.stormingmedia.us/16/1688/A168823.html 9. http://my.ece.ucsb.edu/yorklab/Useful%20Stuff/Tutorials/QuartzCrystalOscillators.pdf 10. http://metrologyforum.tm.agilent.com/xtals.shtml Hidden links: 11. http://www.precisionclock.com/ ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
