User Manual

3.4 Setting FFT Analysis Conditions
61
By specifying a setting factor (rate) to be applied to the input signal, the display
of data exceeding the resulting threshold can be emphasized. This feature is
useful for viewing waveforms that may otherwise be obscured by noise.
The reliability of phase spectrum values is poor when discrete Fourier transform
values are extremely small. For example, in the case of a pure sine wave, almost
all phase values at frequencies other than the input frequency result from calcu-
lation errors. By treating the maximum value of the power (or cross-power) spec-
trum of the input signal, P
max
, as a reference value, data that exceeds that value
multiplied by rate R can be displayed with emphasis.
3.4.7 Emphasizing Analysis Results (phase spectra
only)
10log P
max
[dB]
10log RP
max
[dB]
Power Spectrum
Phase Spectrum
Emphasis
Display
10log P
max
[dB]
10log RP
max
[dB]
Attenuation Rate and Value
Attenuation value: A [dB]
Attenuation rate: R
-A = 10log
10
R
1 x 10
-6
≤ R ≤ 1
0
≤ A ≤ 60
1
2
3
Operating Key Procedure
1
Enable the highlighting function.
CURSOR
Move the cursor to the [Highlight (phase)] item.
F1 to F8
Select whether to enable or disable the highlight-
ing function.
2
Set the attenuation rate or attenuation value.
To set an attenuation rate
CURSOR
Move the cursor to the [Attenuation ratio] item.
F1 to F8
Enter the attenuation rate.
To set an attenuation value [dB]
CURSOR
Move the cursor to the [(dB)] item.
F1 to F8
Enter the attenuation value.
Off Emphasis display disabled.(default setting)
On Emphasis display enabled.
Setting Phase Spectrum Highlighting
To open the screen: Press the SET key → Select with the SUB MENU keys →Status Settings screen
See Screen Layout (
⇒ p. 40)