MR8740、MR8741_user_manual_eng_20191016H.pdf - 第278页
12.4 Selecting Channels 266 Channel selection is the same for all funct ions. For the setting method, refer to "3.5 Input Channel Setting" (p.73) and "7.9 Setting Details of Mod- ules" (p.161). Scal…
12.3 Setting FFT Analysis Conditions
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11
Chapter 12 FFT Function
12
The following settings can be made on the Waveform screen.
Changes to the displayed analysis results become effective when the settings are changed.
• Available settings are frequency range, number of analysis points, type of win-
dow function, trigger mode and pre-triggering
• Available settings are analysis number, analysis mode, waveform color, analy-
sis channel and x/y axis display type
• Trigger settings (p.192)
(Note: If [Reference] is [From Memory], triggers cannot be set.)
12.3.11Setting and Changing Analysis Conditions on
the Waveform Screen
Trigger mode and Pre-trigger
Select the trigger mode and pre-triggering (same as fo
the Memory function).
Trigger Mode: Single, Repeat, Auto
Pre-trigger: Select from list
See: "8.2 Setting the Trigger Mode" (p.191)
"8.9 Pre-Trigger Settings" (p.204)
Number of Analysis Points
(p.251)
(1000, 2000, 5000, 10000)
Frequency Resolution (dur-
ing acquisition)
Select the frequency range (133
mHz to 8 MHz). (p.251)
FFT Window Function Type
(p.254)
Setting method
Use the mouse to move the flashing cursor
to each item, and select a setting from the
GUI displayed on the bottom right of the
screen.
Analysis
Numbe*(p.260)
Analysis Channel
Analysis
Mode
*Coupled with the [Analy-
sis] list at the [Status]
sheet of the Status screen.
Display types of X-axis (horizontal
axis) and Y-axis (vertical axis)
Setting details
To open the screen: Right-click and select [DISP] Waveform screen
Waveform Color
12.4 Selecting Channels
266
Channel selection is the same for all functions.
For the setting method, refer to "3.5 Input Channel Setting" (p.73) and "7.9 Setting Details of Mod-
ules" (p.161).
Scaling
The scaling setting allows values displayed on this instrument to match the actual values read directly on
a sound level meter or vibration meter.
Setting example: To display measurement data on this instrument so that it corresponds
to that on a sound level meter.
In a case where a sound level meter displays 93.5 dB and the overall value displayed on the Wave-
form screen of this instrument is -6-51 dB.
12.4 Selecting Channels
Without Scaling
With Scaling
54
1
2
3
Sound Level Meter
93.5
93.5
1 Select [Num].
2 Select [Ratio].
3 Move the flashing cursor to [Ratio], and
click [dB Scaling].
The dB Scaling dialog appears.
4 Enter the (overall) value “-6.51” displayed
on the instrument.
5 Enter the value "93.5" (from the sound
level meter) that you want to read
directly.
6 Click [Confirm] to perform scaling.
Scaling is performed automatically and the con-
version value is set in the conversion rate column.
See: "Overall Value" (p.A19)
0 dB reference differs depends on the physical quantity.
As an example for sound pressure, 20 Pa is 0 dB.
In dB scaling, the dB value can be directly read; howev-
er, it may not be possible to directly read instantaneous
values.
Read the written standards and other materials regard-
ing 0 dB references.
93.5
93.5
93.5
Overall:
-6.51dB
12.5 Setting Screen Displays
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Chapter 12 FFT Function
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Set the display method for FFT calculation results.
12.5 Setting Screen Displays
1
Select the display format.
Move the flashing cursor to the [Format] item.
Select the format of data to be displayed.
The display format depends on the input data selected for analysis.
*: The horizontal axis and vertical axis display the real parts and the
imaginary parts of calculation results, respectively.
2
Click [DISP] in the right-click menu to display the Wave-
form screen.
Single
Standard
The FFT calculation results are displayed in one screen.
If the calculations have multiple settings, waveforms are
overlaid.
Note: Depending on the analysis mode settings, analy-
sis No1 only may be preferentially displayed.
Dual Standard The FFT calculation results are displayed in two
screens.
If the calculations have multiple settings, waveforms are
displayed for each specified calculation.
Single Nyquist
*
If the analysis mode is linear spectrum, transfer function
or cross power spectrum, the FFT calculation result is
displayed in Nyquist display on one screen.
If the calculations have multiple settings, waveforms are
overlaid.
Dual Nyquist
*
If the analysis mode is linear spectrum, transfer function
or cross power spectrum, the FFT calculation result is
displayed in Nyquist display on two screens.
If the calculations have multiple settings, waveforms are
displayed for each specified calculation.
Running
spectrum
If the analysis mode is one of the following, analysis re-
sults are displayed three-dimensions: frequency, oscil-
lation and time.
(Linear spectrum, RMS spectrum, power spectrum,
power spectrum density, LPC analysis, transfer func-
tion, cross power spectrum, 1/1 octave analysis, 1/3 oc-
tave analysis)
If the calculations have multiple settings, No1 is prefer-
entially displayed.
Procedure
To open the screen: Right-click and select [STATUS] [Status] sheet
To use an existing memory waveform
for analysis
Select [From Memory]as the input data
source [Reference].
See: "12.3.2 Selecting the Data Source
for Analysis" (p.250)
To specify the analysis starting point
Specify the starting point on the memory
waveform.
See: "12.7.1 Analyzing after Specifying an
Analysis Starting Point" (p.273)
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