10-9
IM 701240-01E
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App
Index
Waveform Computation
Explanation
This function displays the power spectrum of CH1 to CH16 and Math1 to Math7
waveforms.
Computation range: Start Point/End Point
By default, the measurement range is
±
5 divisions of the display frame on the time axis.
You can limit this range.
The concept of the computation range is analogous to the concept of the selectable
range of cursor display position in cursor measurement.
For details, see “Selectable Range of Cursor Position” in section 11.4.
Scaling
Set the upper and lower limits of the math waveform display.
Auto:
The upper and lower limits are set according to the computed result.
Manual:
The upper and lower limits can be set arbitrarily. The selectable range is
–9.9999E+30 to 9.9999E+30.
Unit
Unit can be set arbitrarily using up to four characters. The specified characters are
applied to the scale values.
Number of FFT Points
Select from 1000(1k), 2000(2k), 5000(5k), 10000(10k), 20000(20k), 50000(50k), and
100000(100k). Using the number of FFT points from the specified Start point, FFT is
performed and the power spectrum is displayed.
Note
If you set the number of FFT points to 50k or greater, only Math1 and Math2 can be used. In this
case, Math3 to Math8 cannot be used even in computations other than FFT.
Example 1)
Math1 = C1
×
C2, Math2 = PS-LOGMAG(M1), Math3 = C3
×
C4.
If the number of FFT points of Math1 to Math3 is 50 k, only Math1 and Math2 are
computed.
Example 2)
Math1 = C1, Math2 = C2, Math3: The number of FFT points is 50k
→
Computes only Math1 and Math2.
Time Window
Select from the three types listed below. For details on the time window, see page 2-42.
Rect (Rectangular): Best suited for transient signals that attenuate completely within the
time window.
Hanning:
Best suited for continuous and non-periodic signals.
FlatTop:
Best suited for improve the accuracy of the level even if the
frequency resolution is to be compromised.
10.3 Performing Power Spectrum Computation (FFT)