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12.8 FFT Analysis Modes
281
11
Chapte
r 12 FF
T Function
12
Waveform Example
Coherence Function
This function gives a measure of the correlation (coherence) between input and output signals. Val-
ues 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
See:
"12.8.2 Analysis Mode Functions" (p.289)
Axis
Display Type
Description
X axis
Linear
Frequency is displayed with equal spacing
Log
Frequency display of logarithm interval
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).
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 per-
formed before measurement (analysis is not available with time-domain aver-
aging).
• The coherence function has two general definition formulas. For the definition
Summary of Contents for MR8740
Page 2: ......
Page 12: ...Contents x ...
Page 26: ...Operating Precautions 14 ...
Page 128: ...5 5 Miscellaneous Printing Functions 116 ...
Page 196: ...7 12 Setting Output Waveform Parameters 184 ...
Page 234: ...9 5 Numerical Calculation Type and Description 222 ...
Page 248: ...10 3 Waveform Calculation Operators and Results 236 ...
Page 302: ...12 8 FFT Analysis Modes 290 ...
Page 316: ...13 6 Editor Command Details 304 ...
Page 416: ...Appendix 4 FFT Definitions A26 ...
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