11/2/00 FFT (Optional) 11-7
FFT Zoom
You can view approximately 80 bars
of the FFT at once. When you are
zoomed out you will notice that each
bar represents several frequencies or
lines. Pressing the right
r
arrow
key moves to the next line. The cur-
sor will not move to the next bar
until it shows all of the lines repre-
sented by that bar of the graph.
The FFT zoom on the 824 allows you to view a representa-
tion of all 400 lines or a portion of the 400 lines on the dis-
play. This is called a display zoom.
The up
u
arrow key will zoom in the display by a factor of
2 to 8. This means that a zoom factor of 2 shows one half of
the 400 lines on the display. A zoom factor of 8 would show
one eighth of the 400 lines on the display. The down
d
ar-
row key zooms out to a full screen display of the FFT.
The zoom factor is shown graphically as a horizontal bar at
the bottom of the bargraph. The shorter the bar, the greater
the zoom.
The location of the zoom bar indicates the position of the
displayed area of the spectrum.
NOTE: When more than one frequency is
represented by a single bar, the largest
bar is represented on the display. As you
press the right and left arrow keys to
move the cursor across the display, you
will notice that the cursor does not move
until all of the frequencies represented by
that bar have been displayed.
Some examples of zoomed displays are shown below:
While zoomed, the display will scroll when the cursor nears
either the left or right edge of the display.
Bar shows one to one
zoom,
Cursor indicates 5 to 6
points on graph
meaning cursor
indicates one point on
graph
Cursor indicates 3
points on graph
Cursor indicates 2 points
on graph
Overall representation
of spectrum
Zoomed one to one
Zoomed two to oneZoomed three to one
(No zoom)
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