281
FFT Analysis Modes
Coherence Function
This function gives a measure of the correlation (coherence) between input and output signals.
Values obtained are between 0 and 1.
Main uses:
• To evaluate transfer functions
• In a system with multiple inputs, to inspect the effect of each input on the output
About the Functions, refer to “13.9.2 Analysis Mode Functions” (p. 289).
Axis
Display type
Description
X axis
Linear
Displays the frequency on a linear scale
Log
Displays the frequency on a logarithm scale
Y axis
Lin-Mag
Displays the causal relationship and degree of relationship between two input
signals, as a value between 0 and 1 (dimensionless units).
Waveform Example
Normal display
X axis: Log
Y axis: Lin-Mag
• With a single measurement, the coherence function gives a value of one for all frequencies. Spectrum
(frequency-domain) averaging should always be performed before measurement (analysis is not
available with time-domain averaging).
•
The coherence function has two general definition formulas. For the definition formulas, refer to “13.9.2
Analysis Mode Functions” (p. 289).
13
FFT
Function
Содержание MR8827
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