[time-nuts] Meaning of GPSCon "Graph" terms

James Robbins jsrobbins at earthlink.net
Thu Apr 4 08:01:42 EDT 2013


I'm using GPSCon software on my Fury but I'm not clear as to the meaning of some of the terms which populate the "Graph" display?  

1.  At the top "EFC" graph (red), what do "ad=0m" and "sd=0m" mean?  Is "ad" Allan Deviation?  How do these numbers relate to the usual frequency scales we see of so many parts per billion or whatever?  Deviations from what? 

2.  At the lower "TI" graph (blue), what do "av=-0.12n" and  "sd=1.4n" mean?  I assume they are nanosecond averages, but are they averages over the entire reading period and what do they signify?

3.  The green scale numbers in the EFC graph show "432us", "6.5us" and "100ns".  What do these numbers mean?

4.  The "TI" scale shows "4.3ns to -3.1ns".  From what baseline are these the maximum excursions?  

5.  What is the meaning of "LPF -0.2ns"?

6.  Does the slope (up or down) of the gold line in the EFC section (general trend) indicate something?

7.  The "TI to GPS" box seems to show a time interval (e.g. 7.2E-10).  Is this an instantaneous reading or an average?  What is being compared to what?

8.  What does the "3.1e-005" along the left side of the EFC graph mean?

9.  Does this software provide Allan Deviation results?

Many thanks for the explanations.

Jim Robbins
N1JR
 




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