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A N A L Y S I S
F U N C T I O N S
A dynamic stability analysis can be performed with either the overlapping Allan (AVAR) or
overlapping Hadamard (HVAR) variance. The latter is more appropriate when there is
frequency drift in the data.
The resulting dynamic stability plot is saved as a *.tkf file with a filename entered in the Plot
Filename edit box (default DAVAR.TKF).
The plot options provide choices to put the Date and other information at the top of the page,
draw a Box around the page, and use multiple Colors for the 3D surface plot. For color
surface plots, the Grid control selects the grid type: 0=No Grid, 1=Full Grid, 2-9=# of x and y
mesh lines skipped.
The preferred Message Position is Top Right, where there is the most space. The character
sequence '\n' (backslash and lower case n) will insert a carriage return/line feed into the
message to allow a longer, more vertical format. The dynamic stability analysis options and
settings can be saved in the STABLE32.INI configuration file with the Save Config button,
recalled with the Read Config button, and restored to their default settings with the Reset
button.
Dynamic Stability Plot
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The dynamic stability plot is a 3D surface plot of ADEV or HDEV (log sigma) versus
averaging time (log tau or log averaging factor, AF) as a function of time (window #). Sigma
is calculated using fully overlapping samples at all possible averaging factors up to onequarter of the window size. In the axes orientation used, the tau scale is opposite to that
usually used (AF and tau increase toward the left), which is the convention for a dynamic
stability plot, and has the advantage of best showing the sigma-tau surface that usually has
lower sigma at longer tau. The y-axis and-z axis are labeled as log sigma and log AF
respectively, and a log-log grid is shown in the back x plane, while the linear x-axis is labeled
as window #. The dynamic stability plot includes annotations that show the sigma range, tau
range, window parameters, and time span. A plot title can be included at the top, a sub-title at
the bottom, and a message can be shown in any of 9 positions. Date, time, data analysis
limits, and data filename can be included at the top, and an optional plot label (e.g.
organization name) can be included at the bottom.
The dynamic stability 3D surface plot can be shown as a full red mesh or as a sigmadependent multicolor display with or without an adjustable-density mesh. The mesh density
also depends on the window and step sizes. For a large # of analysis windows, it is desirable
to use the grid control to reduce the number of mesh points shown (this does not affect the
underlying surface plot).
The dynamic overlapping Allan and Hadamard deviation calculations are performed from
phase data (after frequency to phase conversion, if necessary). All zero values (including the
first and last data points of an analysis window) are treated as gaps.
If all the data points within an analysis window are gaps, then there will be a corresponding
gap in the stability data, which is shown as having a sigma value at the bottom of the plot.
Thus, a group of missing data points will appear as a trough in the dynamic stability plot, and
will have z values equal to the minimum sigma value.
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