HP 54520 Series Service Manual page 22

Markers
Waveform Math
Fast Fourier
Transforms (FFT)
Chapter 1: General Information
Operating Characteristics
Time Base in Sequential Single-Shot
Used to view previously captured segments as defined in the time base menu. You can
exclude, select, or view individual segment numbers from any channel. Viewing options
include:
Normal Selection and viewing of any or all previously captured segments.
Average Averages and displays previously captured segments into a composite
waveform.
Envelope Displays the minimum and maximum voltages of all previously captured
segments.
Dual voltage and time markers are available. You can independently assign voltage markers to
channels, memories, or functions.
Four independent functions are provided for waveform math. The operators are +, —, X, vs,
magnify, inv (invert), int (integrate), and diff (differentiate), and FFT. You can use the
vertical channels or any of the waveform memories for waveform math. Sensitivity and offset
for these functions are adjusted independently.
Peak Search Peak search automatically snaps cursors to any two selected peaks located
anywhere in the displayed frequency span. You can select peaks from peak number 1 up
to peak number 99. Frequency and dBm are automatically displayed at the bottom of the
screen together with the difference in frequency between the two selected peaks. Peak
search saves time by eliminating the need to manually set cursors.
Channels or Memories FFTs can be executed on any of the oscilloscope input
channels, or on waveforms stored in any of four nonvolatile memories.
Variable Sensitivity and Offset Sensitivity and offset (vertical position) can be
controlled to display an optimum view of the spectrum. Sensitivity is calibrated in dB per
division; offset is calibrated in dBm.
Selectable Number of Points You can set the number of points the oscilloscope uses
to calculate the FFT, from 512 to 32,768 (in powers of 2). Increasing the number of
points improves frequency resolution at the expense of update speed. The point choices
available are dependant on the data being operated upon.
Horizontal Magnify Mode This mode allows you to specify the frequency that is
displayed at center screen, and magnify the frequency-domain display about that point.
Magnification increases as the number of time-record samples increases. At the
maximum of 32,768 points, magnification reduces the displayed frequency span to about
12% of that in the unmagnified display. Horizontal magnification allows you to zero in on
and expand desired portions of the frequency-domain display.
Center Frequency Control Enabling horizontal magnification allows you to set the
center of the display to a frequency of interest. The display is magnified about that point
so that you get a closer view.
Selectable Windows Three windows are selectable: Hanning, for best frequency
resolution and general purpose use; flattop, for best amplitude accuracy; and rectangular,
for single-shot signals such as transients and signals where there are an integral number
of cycles in the time record.
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