Bob, I have to ask about the B-term. In the paper that Scott started this with I see that B was 4.45. But if I understand you correct Bt<1 even at 30days is normal? That would mean a B of <0.033?
Lars >Bob wrote: >In a conventional fit situation, you have < 30 days worth of data and the >“time constant” is > 30 days. Put another way bt <= 1 in the normal case. It is only when you go out to years that bt gets large. Bob >> On Nov 18, 2016, at 9:58 PM, Scott Stobbe <scott.j.sto...@gmail.com> wrote: > > Hi Lars, > > I agree with you, that if there is data out there, it isn't easy to find, > many thanks for sharing! > > Fitting to the full model had limited improvements, the b coefficient was > quite large making it essentially equal to the ln(x) function you fitted in > excel. It is attached as "Lars_FitToMil55310.png". > > So on further thought, the B term can't model a device aging even faster > than it should shortly after infancy. In the two extreme cases either B is > large and (Bt)>>1 so the be B term ends up just being an additive bias, or > B is small, and ln(x) is linearized (or slowed down) during the first bit > of time. > > You can approximated the MIL 55310 between two points in time as > > f(t2) - f(t1) = Aln(t2/t1) > > A = ( f(t2) - f(t1) )/ln(t2/t1) > > Looking at some of your plots it looks like between the end of year 1 and > year 10 you age from 20 ppb to 65 ppb, > > A ~ 20 > > The next plot "Lars_ForceAcoef", is a fit with the A coefficient forced to > be 2 and 20. The 20 doesn't end-up fitting well on this time scale. > > Looking at the data a little more, I wondered if the first 10 day are going > through some behavior that isn't representative of long-term aging, like > warm-up, retrace (I'm sure bob could name half a dozen more examples). So > the next two plots are fits of the 4 data points after day10, and seem to > fit well, "Lars_FitAfterDay10.png", "Lars_1Year.png". > > If you are willing to share the next month, we can add that to the fit. > > Cheers, > > On Fri, Nov 18, 2016 at 1:26 PM, Lars Walenius <lars.walen...@hotmail.com> > wrote: >> >> Hopefully someone can find the correct a and b for a*ln(bt+1) with > stable32 or matlab for this data set: >> Days ppb >> 2 2 >> 4 3.5 >> 7 4.65 >> 8 5.05 >> 9 5.22 >> 12 6.11 >> 13 6.19 >> 25 7.26 >> 32 7.92 > <Lars_1Year.png><Lars_FitAfterDay10.png><Lars_FitToMil55310.png><Lars_ForceAcoef.png>_______________________________________________ > 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. _______________________________________________ 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. _______________________________________________ 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.