Fluke Biomedical 190M - Manual (Page 39)

Using the Scope and Meter
Acquiring Waveforms
1
29
Using Mathematics Function Spectrum (FFT)
The Spectrum function shows the spectral content of the
input A, B, C or D waveform in the input trace color. It
performs an FFT (Fast Fourier Transform) to transform the
amplitude waveform from the time domain into the
frequency domain.
To reduce the effect of side-lobes (leakage) it is
recommended to use Auto windowing. This will
automatically adapt the part of the waveform that is
analyzed to a complete number of cycles
Selecting Hanning, Hamming or no windowing results in a
faster update, but also in more leakage.
Ensure that the entire waveform amplitude remains on the
screen.
To use the Spectrum function, do the following:
1
SCOPE
Display the SCOPE key labels.
2 F4 Open the Waveform Options
menu.
3
ENTER
Jump to Waveform: and select
Mathematics... to open the
Mathematics menu.
4
ENTER
Select Function: Spectrum.
5
ENTER
Select the source waveform for the
spectrum: Source : A, B, C or D
6
ENTER
Select Window: Auto (automatic
windowing), Hanning, Hamming,
or None (no windowing).
You will see a screen that looks like Figure 11.
Observe that the top right of the screen displays
SPECTRUM.
If it displays LOW AMPL a spectrum measurement cannot
be done as the waveform amplitude is too low.