Hioki Memory HiCorder MR6000, Instruction Manual, Page: 259 / 392

253
FFT Calculation Types
Coherence function
This function shows a ratio of components that have coherence with an input signal to whole
components of an output signal. Values ranges zero to one. A coherence function of one shows that
an input signal does not affect the frequency of an output signal.
Main uses:
• To analyze a transfer function
• To analyze effects of each input signal on an output signals for a multi-input system.
See “Calculation types and internal calculation formulas” (p. 254).
Axis Display type Description
Horizontal axis
(X-axis)
Linear Indicates a frequency on a linear scale.
Logarithmic Indicates a frequency on a logarithm scale.
Vertical axis
(Y-axis)
Amplitude
(linear)
Indicates a cause-and-effect relationship of relevance ratio between two
input signals, degree of which are presented by a numerical value that
ranges zero to one. (non-dimensional)
Examples of waveforms
Normal display
Horizontal axis: logarithmic
Vertical axis: amplitude (linear)
• A single measurement causes the coherence function to be one across the entire frequency
range. Always execute the averaging process of the FFT function before measurement.
• The coherence function has two general definition formulas. For the definition formulas, refer to
“Calculation types and internal calculation formulas” (p. 254).
FFT
Calculation Function
HIOKI MR6000A966-03