10-9
IM 701210-06E
Waveform Computation
10
Explanation
This function displays the power spectrum of CH1 to CH16, DSP1 to DSP6 (optional),
and Math1 to Math7 waveforms.
Setting the 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 section 11.5, “Selectable Range of Cursor Position.”
Number of Computed Points: FFT Point
Select 1000 (1 k), 2000 (2 k), 5000 (5 k), 10000 (10 k), 20000 (20 k), 50000 (50 k), or
100000 (100 k).
Using the number of computing 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,
Math1 to Math3: The number of FFT points is 50k
→ Computes only Math1 and Math2.
Example 2) Math1: C1, Math2: C2, Math3: The number of FFT points is 50k
→ Computes only Math1 and Math2.
Selecting the Time Window
Select from the following four types.
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.
Exponential (window): The exponential window eliminates noise components from the
signal. It can be selected only when the user-defined
computation option is installed.
It is effective against frequency response test signals generated
through impulse excitation.
10.3 Displaying the Power Spectrum
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