Display Tools; Setting The Time Constant - Symmetricom 5120A Operation And Maintenance Manual

The table on the left displays the loaded test mask.
The pressed softkey is highlighted. The loaded mask has become the current mask.
4. Press Return.
5. Make sure the mask will be plotted. The topmost softkey in the test mask editor will read
Hide Mask if the mask is to be plotted. If it will not be plotted, the softkey is labeled
Show Mask. Press the Show Mask key to enable plotting the mask.
Test masks can be loaded and saved by right-clicking the plot. Select Test Mask > Save > Mask 3
in the popup menu to save the current mask as the third mask, for example. Test masks can also be
shown and hidden using this menu.

5.1.4 Display Tools

The Display Tools softkey available through the Config Phase Noise menu accesses a menu with
the following softkeys:
Pause Updates stops update of the data display. This softkey toggles to Resume Updates.
Take Snapshot displays a snapshot of the data to compare to data as it is being collected.
Snapshot data is plotted in white.
Hide Snapshot toggles with Show Snapshot to disable/enable plotting of the snapshot.
Integrated Phase Noise accesses a read-only table that displays integrated phase noise
with and without spurs. Each row shows integrated phase noise for one lower limit. As the
phase noise data set grows, additional rows appear for even lower limits. See
Tables"
includes phase noise out to 1 MHz.
Time Constant, described in detail in the following section.

5.1.4.1 Setting the Time Constant

The time constant determines the length of the running average used for (f) phase noise and Allan
deviation computations. Beginning with software revision 260 all test set models support
configuration of the time constant. One of four running averages can be selected: 1, 10, or 100
seconds, and infinite.
Note
Before software revision 260, the PNTS always employed an infinite running average. The infinite
time constant is the factory default setting in new software revisions. The current time constant
setting is displayed in the phase noise plot. The field is labeled Time Constant and can be found
below plotted data, in the bottom right corner.
The time constant can be changed using the (f) phase noise plot Display Tools sub-menu. It can
be changed before or during data collection. When set in Collecting state, the following will be
observed:
Allan deviation and (f) phase noise data set, its subsets and meta data such as integrated
phase noise, are cleared. They remain blank for a brief period - until measurements using
the new time constant become available.
Data sets in the phase and frequency difference plots and the frequency counter continue
to be maintained without interruption.
5120A/5115A Operations and Maintenance Manual
on page 15 for more information about read-only tables. Integrated phase noise
"3.3.2
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