10-10
IM 701240-01E
Displaying the Overall Value (Only When Measure Is Set to ON)
If the channels (Math1 to Math8) on which power spectrum computation (PS) is selected
are in the middle of the automated measurement of waveform parameters (MEASURE:
ON) and Rms is ON, the screen shows “Rms = overall value.” For details on the
automated measurement of waveform parameters, see section 11.5.
The overall value is the total RMS value determined from the frequency spectrum
included in the signal. The overall value is determined by summing the power spectrum
of all frequencies and then taking the square root.
k
2
×
PS
0
+
Σ
PS
i
(Vrms)
Overall Value =
The k value varies depending on the selected time window as follows:
Time Window Type
k
Rect (Rectangular)
1
Hanning
1.5
Flattop
3.19693
Linear Scaling
When performing computation on a channel that has linear scaling set, the computation
is performed on the scaled value.
Notes on Power Spectrum Display
• The power spectrum cannot be computed, if the displayed record length is less than
number of computed points.
• The number of computed points, time window, Start Point, and End Point are common
to all computation channels.
• You cannot expand the FFT waveforms horizontally that would cause the number of
points to be 50 or less.
Notes on Computation
• Computation is not executed when you change Start Point or End Point while the
computation is stopped. Be sure to press Exec to perform the computation again. If
you do not, the waveform will not be displayed correctly when the screen is redrawn.
• Normally, computation is performed on the sampled data stored in the acquisition
memory. However, for waveforms that have been acquired in envelope mode,
computation is performed on the maximum/minimum values per acquisition interval.
Note
While computation is in progress,
is indicated at the upper left of the screen.
10.3 Performing Power Spectrum Computation (FFT)
