User Manual

3.10 FFT Analysis Modes
96
Waveform Example
Transfer Function TRF
From the input and output signals, the transfer function (frequency characteristic) of a measurement
system can be obtained. It can also be displayed as a Nyquist plot.
Main uses:
• To inspect a filter’s frequency characteristic
• To inspect the stability of a feedback control system (using the Nyquist plot)
• To inspect the resonance characteristic of an object using an impulse hammer and pick-up sensor
See About the Functions "3.10.2 Analysis Mode Functions" (⇒ p. 102), "Linear Time-Invariant Systems" (⇒ p. 104)
Axis Display Type Description
X axis
Linear
Frequency is displayed with equal spacing
Display Range: DC to the top of the frequency range
Log
Frequency is displayed logarithmically
Display Range: 1/400
th
to 1/4000
th
(depending on the number of analysis
points) to the top of the frequency range
Nyquist display
Displays the real-number component of the input-output ratio.
Y axis
Lin-Mag
Displays the input-output ratio linearly (dimensionless units).
Log-Mag (logarithm)
Displays the input-output ratio as dB values.
Lin-Real
Displays the real-number component of the input-output ratio (dimensionless
units).
Lin-Imag
Displays the imaginary component of the input-output ratio (dimensionless
units).
Nyquist display
Displays the imaginary component of the input-output ratio.
Normal display
X axis: Log
Y axis: Lin-Mag
Normal display
X axis: Log
Y axis: Log-Mag
Normal display
X axis: Log
Y axis: Lin-Real
Normal display
X axis: Log
Y axis: Lin-Imag
Nyquist display