Agilent Technologies 54657A, User Manual

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•
Cent Freq Allows centering of the FFT spectrum to the desired frequency.
Select and rotate the knob closest to the
Cursors
key to set the
center frequency to the desired value.
•
Freq Span
Sets the overall width of the FFT spectrum (left graticule to
right graticule). Select and rotate the knob closest to the
Cursors
key to set the center frequency to the desired value. See FFT
Measurement Hints (next page) for information on using frequency
span to magnify the display.
•
Move 0Hz To Left
Pressing this key changes the center frequency so that
the left most graticule represents 0 Hz.
•
Autoscale FFT
The Autoscale FFT softkey will automatically set Units/div
and Ref Levl to bring the FFT data on screen. Frequency Span is set to
maximum.
•
Window
Allows one of four windows to be selected. Select and rotate the
knob closest to the
Cursors
key to set the desired window. The
rectangular window is useful for transients signals and signals where
there are an integral number of cycles in the time record. The hanning
window is useful for frequency resolution and general purpose use. It
is good for resolving two frequencies that are close together or for
making frequency measurements. The flattop window is the best
window for making accurate amplitude measurements of frequency
peaks. The exponential window is the best window for transients
analysis.
•
Previous Menu Returns you to the previous softkey menu.
FFT spectrum (F2) is available for viewing, measurement, or storage.
9
The
Cursors
key contains two additional selections that can be
used to measure or move the FFT spectrum. Press
Cursors
,
then set the Source softkey to F2 .
Find Peaks
Pressing this key sets Vmarker1 and the start marker (f1) on the
peak with the highest amplitude and sets Vmarker2 and the stop marker (f2)
on the peak with the next highest amplitude. Marker values in dBV/dBm or
frequency (dependent on the active cursor)are automatically displayed at the
bottom of the oscilloscope screen. The difference in dBV/dBm (
∆
V) or
frequency (
∆
f) between the two peaks is also displayed.
Move f1 To Center
Pressing this key changes the center graticule (or center
frequency) to the current f1 marker frequency. If f1 cannot be found, a
message is displayed on the screen.
Operating the Measurement/Storage Module
FFT Measurement
2–11