Hioki 8847 - Setting the Frequency Range and Number of Analysis Points

13.3 Setting FFT Analysis Conditions
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13
Chapter 13 FFT Function
About the frequency range and number of analysis points ___________________
• The settings for the frequency range and number of analysis points determine
the input signal acquisition time and frequency resolution.
• The frequency range setting for the FFT function corresponds to the timebase
setting of the Memory function. Changing the frequency range also changes
the data sampling period.
See: "Relationship Between Frequency Range, Resolution and Number of Analysis
Points" (
 p.212)
• The cut-off frequency of the anti-aliasing filter is the same as the frequency
range setting.
See: "Relationship Between Frequency Range, Resolution and Number of Analysis
Points" (
 p.212)
• The set number of analysis points specifies the amount of data to be analyzed
with each measurement. Increasing the number of analysis points increases
the frequency resolution, but also increases the time required for calculations.
See: "Number of Analysis Points"( p.A17)
13.3.3 Setting the Frequency Range and Number of
Analysis Points
When using the external sampling to calculate:
Set the Sampling Clock to [External] (External sampling).
In this case, octave analysis, power spectrum density and LPC Analysis(power
spectrum density) are not available.
When the [Reference] is [From Memory], the frequency is automatically
set.
The setting cannot be changed.
To control sampling by an external signal,
select [External]
When the input data [Reference] is
[From Memory]
The frequency range is set automatically
when analysis is started.
1
Set the number of FFT analysis points.
Move the cursor to the [Sampling Point] item.
Select
See: "Number of Analysis Points"( p.A17)
2
Select the frequency range.
Move the cursor to the [Frequency Range] item.
Select
See: "Relationship Between Frequency Range, Resolution and Number of
Analysis Points" (
 p.212)
1000 (default setting), 2000, 5000, 10000
8 MHz(default setting), 4 MHz, 2 MHz, 800 kHz, 400 kHz, 200 kHz, 80
kHz, 40 kHz, 20 kHz, 8 kHz, 4 kHz , 2 kHz, 800 Hz, 400 Hz, 200 Hz, 80
Hz, 40 Hz, 20 Hz, 8 Hz, 4 Hz, 1.33 Hz, 800 mHz, 667 mHz, 400 mHz, 333
mHz, 133 mHz, External
Procedure
To open the screen: Press the STATUS key → [Status] sheet
See: To set from the Waveform screen (
 p.225)
Frequency Resolution
(during acquisition)
The resolution is affected by settings of
frequency range and the number of
analysis points. Not displayed for exter-
nal sampling.
2
1