Symmetricom 5115A, Operation And Maintenance Manual

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5120A/5115A Operations and Maintenance Manual 49
5.4.1 Scaling the Frequency Difference Plot
The frequency difference plot can be scaled in the following ways:
„
Automatically scale the y axis to fit all data.
„
Display the y axis in fixed scale mode.
The x axis scale is 60 seconds per division and displays about nine minutes of data.
To scale the plot:
1. Press Freq Diff Plot (see “3.1.1 Navigation” on page 12).
2. Press Config Freq Diff .
„
To automatically scale the y axis, press Auto Scale Y Axis .
„
To manually scale it, press Fixed Scale Y Axis , then press one of the following:
•
Use Shift Up 1 Div and Shift Down 1 Div to shift (scroll) the data up or down
one division on the screen.
•
Use Increase Units/Div or Decrease Units/Div to increase or decrease the values
for each division on the plot.
•
Use Center Median to center the data’s median value.
5.4.2 Pausing or Resuming Updates
The frequency difference measurement display can be paused by pressing the Pause Updates
softkey. To resume updates, press the Resume Updates softkey. As with all data sets that can be
paused, the test set continues to collect data while updates are paused and presents the latest data
set when they are resumed.
5.5 Configuring the Frequency Counter
The PNTS collect data that measures the frequency of the Input signal using the Reference signal
as a reference. The test set continually computes and displays frequency averages for the Input
signal port for the last 1, 10, 100, and 1000 seconds. When set automatically, the
Reference
Frequency value may be displayed as “ not yet set” until data collection begins, then the frequency
of the Reference port signal is displayed.
In the internal reference mode of the 5120A-01, the Reference Frequency displays as Internal
indicating that the internal oscillators are used. In this mode, a message about the accuracy of
absolute frequency averages is displayed (and printed) below the frequency counter table. In the
extremely unlikely event of corrupt internal reference calibration information, the Reference
Frequency displays as “UNCALIBRATED”. If this occurs, the internal reference oscillators
should be calibrated as soon as possible. See
“8.1 5120A-01 Internal Reference” on page 72 for
information about calibration. For best frequency counter measurements with the 5120A-01, use
an external precision 10 MHz source connected to the Reference input.
The frequency counter table shows the following:
„
The average frequency of the Input signal.
„
Frequency averages which are continually updated. After 10 seconds, 1 and 10 second
averages are displayed, after 1000 seconds all four averages are available.