11.3
FFT Processing Examples
Example: spectrum of the 9400A Probe Calibrator waveform.
I)
Connect the 9400A calibration signal (976.6 Hz, 1.0 V pp square
wave) to the channel 1 input.
2)
If you use a xlO probe, select Panel STATUS and adjust the Set Chl
Attenuator to )d0.
Set Channel i volts/div to 20 mV/div (for)dO probe), AC, 1
Set the Channel 1 offset to a value near 0.
3)
Select a time base of 1 msec/div.
4)
Adjust
the triggering conditions as follows: Chl, AC coupling,
normal;
trigger level about 0 div.
You should obtain a repetitive display of almost I0 periods of a
square wave, 5 divisions peak-to-peak.
5)
Turn on and Select Function E
6)
Redefine Function E as follows:
Function Class:
Display Type:
Transform Size:
Source Trace:
Window Type:
Multiplication Factor:
Additive Constant:
Zero Suppression:
Fourier Transform
Magnitude
1250
Chan 1
Rectangular
1.00
+0.00 div
ON
Notice that at the bottom of the menu page the effective number of
points, N = 1250, and the Nyquist frequency = 62.5 kHz are
displayed.
11-4
Fast Fourier Waveform Processing
Option (VP02, V 2.06FT)
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