Bruce, I hear what you say but the results seem to correlate quite well:-
1 tau, 3.0127e-009 adev(n=399998), 3.0127e-009 oadev(n=399998) 1 tau, 3.0257e-009 adev(n=199998), 3.0257e-009 oadev(n=199998) And using the first half of the data:- 1 tau, 3.0411e-009 adev(n=199998), 3.0411e-009 oadev(n=199998) So I'm trying to understand why this won't work. 73, Steve 2009/4/9 Bruce Griffiths <[email protected]>: > Steve > > It cant, it must be a matter of interpretation. > Perhaps it means something like: > > 1 tau means tau = 1x the interval between consecutive measurements. > 2 tau means tau = 2x the interval between consecutive measurements > > 100000 tau means tau = 100,000 x the interval between consecutive > measurements > > Bruce > > Steve Rooke wrote: >> Bruce, >> >> But how does that explain the output of Tom's adev1 program which >> still seems to give a a good measurement at tau = 1s? >> >> 73, >> Steve >> >> 2009/4/8 Bruce Griffiths <[email protected]>: >> >>> Steve >>> >>> If you delete every second measurement then your effective minimum >>> sampling time is now 2s and you can no longer calculate ADEV for tau< 2s. >>> You can still calculate ADEV for tau = 100,000 sec. >>> >>> If you delete all but the first 200,000 lines then you can calculated >>> ADEV for tau=1sec and up to tau= 25,000 sec with reasonable accuracy. >>> >>> You shouldn't lose sight of the fact that ADEV and OADEV are both >>> estimates of the Allan deviation. >>> >>> >>> Bruce >>> >>> Steve Rooke wrote: >>> >>>> Tom, >>>> >>>> I understand fully the points that you have made but I have obviously >>>> not made my point clear to all and i apologise for my poor >>>> communication skills. >>>> >>>> This is what I'm getting at: >>>> >>>> Using your adev1.exe from http://www.leapsecond.com/tools/adev1.htm >>>> and processing various forms of gps.dat from >>>> http://www.leapsecond.com/pages/gpsdo-sim/gps.dat.gz. >>>> >>>> C:\Documents and Settings\Steve Rooke\Desktop>adev1.exe 1 <gps.dat >>>> >>>> ** Sampling period: 1 s >>>> ** Phase data scale factor: 1.000e+000 >>>> ** Total phase samples: 400000 >>>> ** Normal and Overlapping Allan deviation: >>>> >>>> 1 tau, 3.0127e-009 adev(n=399998), 3.0127e-009 oadev(n=399998) >>>> 2 tau, 1.5110e-009 adev(n=199998), 1.5119e-009 oadev(n=399996) >>>> 5 tau, 6.2107e-010 adev(n=79998), 6.1983e-010 oadev(n=399990) >>>> 10 tau, 3.1578e-010 adev(n=39998), 3.1549e-010 oadev(n=399980) >>>> 20 tau, 1.6531e-010 adev(n=19998), 1.6534e-010 oadev(n=399960) >>>> 50 tau, 7.2513e-011 adev(n=7998), 7.3531e-011 oadev(n=399900) >>>> 100 tau, 4.0029e-011 adev(n=3998), 4.0618e-011 oadev(n=399800) >>>> 200 tau, 2.1512e-011 adev(n=1998), 2.1633e-011 oadev(n=399600) >>>> 500 tau, 9.2193e-012 adev(n=798), 9.1630e-012 oadev(n=399000) >>>> 1000 tau, 4.9719e-012 adev(n=398), 4.7750e-012 oadev(n=398000) >>>> 2000 tau, 2.6742e-012 adev(n=198), 2.5214e-012 oadev(n=396000) >>>> 5000 tau, 1.0010e-012 adev(n=78), 1.1032e-012 oadev(n=390000) >>>> 10000 tau, 6.1333e-013 adev(n=38), 6.1039e-013 oadev(n=380000) >>>> 20000 tau, 3.8162e-013 adev(n=18), 3.2913e-013 oadev(n=360000) >>>> 50000 tau, 1.0228e-013 adev(n=6), 1.5074e-013 oadev(n=300000) >>>> 100000 tau, 5.8577e-014 adev(n=2), 6.7597e-014 oadev(n=200000) >>>> >>>> So far, so good. Now I delete every even line in the file which leaves >>>> me with 200000 lines of data (400000 lines in original gps.dat file). >>>> (awk 'and(NR, 1) == 0 {print}' <gps.dat >gps1.dat) >>>> >>>> C:\Documents and Settings\Steve Rooke\Desktop>adev1.exe 1 <gps1.dat >>>> >>>> ** Sampling period: 1 s >>>> ** Phase data scale factor: 1.000e+000 >>>> ** Total phase samples: 200000 >>>> ** Normal and Overlapping Allan deviation: >>>> >>>> 1 tau, 3.0257e-009 adev(n=199998), 3.0257e-009 oadev(n=199998) >>>> 2 tau, 1.5373e-009 adev(n=99998), 1.5345e-009 oadev(n=199996) >>>> 5 tau, 6.3147e-010 adev(n=39998), 6.3057e-010 oadev(n=199990) >>>> 10 tau, 3.3140e-010 adev(n=19998), 3.3067e-010 oadev(n=199980) >>>> 20 tau, 1.7872e-010 adev(n=9998), 1.7810e-010 oadev(n=199960) >>>> 50 tau, 7.9428e-011 adev(n=3998), 8.1216e-011 oadev(n=199900) >>>> 100 tau, 4.2352e-011 adev(n=1998), 4.3265e-011 oadev(n=199800) >>>> 200 tau, 2.2001e-011 adev(n=998), 2.2593e-011 oadev(n=199600) >>>> 500 tau, 9.6853e-012 adev(n=398), 9.5441e-012 oadev(n=199000) >>>> 1000 tau, 5.0139e-012 adev(n=198), 5.0387e-012 oadev(n=198000) >>>> 2000 tau, 2.7994e-012 adev(n=98), 2.7090e-012 oadev(n=196000) >>>> 5000 tau, 1.4280e-012 adev(n=38), 1.2214e-012 oadev(n=190000) >>>> 10000 tau, 7.4881e-013 adev(n=18), 6.5814e-013 oadev(n=180000) >>>> 20000 tau, 7.6518e-013 adev(n=8), 3.7253e-013 oadev(n=160000) >>>> 50000 tau, 2.4698e-014 adev(n=2), 1.3539e-013 oadev(n=100000) >>>> >>>> Obviously we don't have enough data now for a measurement of 100000 >>>> tau but the results for the other tau are quite close, especially when >>>> there are sufficient data points. Now this is discontinuous data, >>>> exactly what I was trying to allude to. >>>> >>>> OK, so now I take only the top 200000 lines of the gps.dat file (head >>>> -200000 gps.dat >gps2.dat) >>>> >>>> C:\Documents and Settings\Steve Rooke\Desktop>adev1.exe 1 <gps2.dat >>>> >>>> ** Sampling period: 1 s >>>> ** Phase data scale factor: 1.000e+000 >>>> ** Total phase samples: 200000 >>>> ** Normal and Overlapping Allan deviation: >>>> >>>> 1 tau, 3.0411e-009 adev(n=199998), 3.0411e-009 oadev(n=199998) >>>> 2 tau, 1.4985e-009 adev(n=99998), 1.4999e-009 oadev(n=199996) >>>> 5 tau, 6.1964e-010 adev(n=39998), 6.2010e-010 oadev(n=199990) >>>> 10 tau, 3.1315e-010 adev(n=19998), 3.1339e-010 oadev(n=199980) >>>> 20 tau, 1.6499e-010 adev(n=9998), 1.6495e-010 oadev(n=199960) >>>> 50 tau, 7.1425e-011 adev(n=3998), 7.3416e-011 oadev(n=199900) >>>> 100 tau, 3.9940e-011 adev(n=1998), 4.0730e-011 oadev(n=199800) >>>> 200 tau, 2.1488e-011 adev(n=998), 2.1558e-011 oadev(n=199600) >>>> 500 tau, 8.4809e-012 adev(n=398), 9.0886e-012 oadev(n=199000) >>>> 1000 tau, 4.9223e-012 adev(n=198), 4.7104e-012 oadev(n=198000) >>>> 2000 tau, 2.4335e-012 adev(n=98), 2.4515e-012 oadev(n=196000) >>>> 5000 tau, 1.0308e-012 adev(n=38), 1.0861e-012 oadev(n=190000) >>>> 10000 tau, 5.9504e-013 adev(n=18), 6.1031e-013 oadev(n=180000) >>>> 20000 tau, 3.6277e-013 adev(n=8), 3.1994e-013 oadev(n=160000) >>>> 50000 tau, 1.0630e-013 adev(n=2), 1.6715e-013 oadev(n=100000) >>>> >>>> Is there any Linux tools for calculating adev as I'm having to run >>>> Windows in a VMware session? >>>> >>>> 73, >>>> Steve >>>> >>>> 2009/4/8 Tom Van Baak <[email protected]>: >>>> >>>> >>>>> Steve, >>>>> >>>>> You've asked a couple of questions. Let me start with this. >>>>> >>>>> It is true that if one were only interested in the performance >>>>> of a pendulum (or quartz or atomic) clock for averaging times >>>>> of one day that all you would need is a series of time error >>>>> (aka phase) measurements made about the same time once >>>>> a day (doesn't have to be that exact). After one week, you'd >>>>> have 7 error measurements (=6 frequency =5 stability points) >>>>> and this is adequate to calculate the ADEV for tau 1 day. >>>>> This alone allows you to rank your clock among all the other >>>>> pendulum clocks out there. Note also you get time error and >>>>> rate error from these few data points too. >>>>> >>>>> As another example, suppose you have a nice HP 10811A >>>>> oscillator and want to measure its drift rate. In this case you >>>>> could spend just 100 seconds and measure its frequency >>>>> once a day, or even once every couple of days. Do this for >>>>> a month and you'd have several dozen points. If you plot >>>>> these frequency measurements you will likely see that they >>>>> approximately fall on a line; the slope of the is the frequency >>>>> drift rate of the 10811. The general shape of the points, or >>>>> the fit of the line is a rough indication of how consistent the >>>>> drift rate is or if it's increasing or decreasing. >>>>> >>>>> Neither of these examples require a lot of data. Both of these >>>>> are real-world examples. >>>>> >>>>> OK so far? >>>>> >>>>> /tvb >>>>> >>>>> >>>>> >>>>> _______________________________________________ >>>>> time-nuts mailing list -- [email protected] >>>>> To unsubscribe, go to >>>>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>>>> and follow the instructions there. >>>>> >>>>> >>>>> >>>> >>>> >>>> >>> _______________________________________________ >>> time-nuts mailing list -- [email protected] >>> To unsubscribe, go to >>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>> and follow the instructions there. >>> >>> >> >> >> >> > > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > -- Steve Rooke - ZL3TUV & G8KVD & JAKDTTNW Omnium finis imminet _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
