HP 54750A, User Manual, Page: 283 / 478

General Purpose Oscilloscope Menus
FFT Menu
Frequency measurements
For best frequency accuracy on peaks
1. In the Channel menu, set the Scaling for almost full scale deection.
2. Set the Span so that the signal of interest is near the horizontal center of the screen (not down at
dc), but high enough to avoid aliasing. The left edge of the screen is 0 Hz, or dc .
3. Select the Hanning window .
A higher number of points results in more accurate measurements, but also takes more computation
time . Depending on your application, you can balance between the need for accurac y and computation
speed of the FFT .
Frequency accuracy
The frequency accuracy is the sum of two terms . The rst term is supplied
because there are a limited number of frequency bins , and the measurement
is accurate to plus or minus half a bin. The second term is related to the
accuracy of the internal oscillator which generates the sample clock.
accur acy = 6
f r eq uency r esolution
2
+ 0: 007% 2 sig nal f r eq uency
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