2009/4/9 Bruce Griffiths <[email protected]>: > The sampling interval is indeed 1sec in the original data. > However, if you delete every second sample the sampling interval in the > resultant data is then 2 sec.
Doesn't that imply that the data point should correspond to the whole sampling period and not just half of it? 73, Steve >> OK, I'll have a go at compiling it as it is just a command line program. >> >> 73, >> Steve >> >> 2009/4/9 Bruce Griffiths <[email protected]>: >> >>> Steve >>> >>> Therein lies your problem. >>> adev1 defaults to a sampling interval of 1 sec. (read the C source code). >>> TvB's documentation explicitly states that you should supply the >>> sampling interval. (its a command line argument for adev1.c). >>> >>> adev1.c is a simple command line program that uses stdin and stdout so >>> porting it to a linux command line (non graphical) program should be >>> straightforward. >>> You can even use redirection and pipes should you need them. >>> >>> You can try porting it to Scilab which is free courtesy of the French >>> Government. >>> >>> >>> Bruce >>> >>> Steve Rooke wrote: >>> >>>> Bruce, >>>> >>>> I set nothing, as indicated in my text, I just delete data points, IE. >>>> a file of 400000 records now becomes 200000. I'm trying to get my head >>>> round this as the absolute requirement for continuous data seems >>>> unneeded. What you have to remember here is that the data set I'm >>>> working with consists of discrete measurements of the period of each >>>> pulse. If it was timestamps, then there would be problems. >>>> >>>> I don't know how much MATLAB costs but I would guess it is way out of my >>>> budget. >>>> >>>> 73, >>>> Steve >>>> >>>> 2009/4/9 Bruce Griffiths <[email protected]>: >>>> >>>> >>>>> Steve >>>>> >>>>> The data file doesn't include the time interval between samples so do >>>>> you set this in some way? >>>>> If so you need to set it to 1s for the unaltered data, to 2s when you >>>>> take every 2nd sample, and 1s when you take the first 200,000 samples. >>>>> >>>>> In principle you could use CANVAS (available on request from USNO - >>>>> however you may have to wait a few days while they decide whether to >>>>> grant your request.) for such analysis in Linux but you would then need >>>>> the Linux version of Matlab. >>>>> Or you could request that it be compiled for Linux - a fairly simple >>>>> task if one has the Linux version of Matlab. >>>>> >>>>> In principle you should be able to port the m source files to Scilab, >>>>> but there are some subtle differences between Scilab and Matlab so this >>>>> may take a while. >>>>> >>>>> 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 >>>>>>>> >>>>>>>> >>>>>>>> >>>>> INCORRECT!! >>>>> sampling period is now 2s. >>>>> >>>>> >>>>>>>> ** 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. >>>>> >>>>> >>>>> >>>> >>>> >>>> >>> _______________________________________________ >>> 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.
