B&K Precision 2552-2559 - Manual - Manual (Page 42)

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spectrum.
Hanning
Hamming
Better frequency, poorer
magnitude accuracy than
Rectangular. Hamming has
slightly better frequency
resolution than Hanning.
Sine, periodic, and
narrow-band random
noise. Asymmetric
transients or bursts.
Blackman Best magnitude, worst
frequency resolution.
Single frequency
waveforms, to find
higher order
harmonics.
Magnifying the FFT Spectrum
You can magnify and use cursors to take measurements on the FFT
spectrum. The oscilloscope includes an “FFT Zoom” option to magnify
horizontally, press this option button to select “1X”, “2X”, “5X” or “10X”.
Moreover, you also can turn the “Universal” knob to magnify FFT
waveform horizontally in a 1-2-5 step. To magnify vertically, turn the
“Volts/div” knob.
Measuring an FFT Spectrum Using Cursors
You can take two measurements on FFT spectrums: magnitude (in dB) and
frequency (in Hz). Magnitude is referenced to 0 dB, where 0 dB equals 1
Vrms. You can use the cursors to take measurements at any zoom factor.
Use horizontal cursors to measure amplitude and vertical cursors to
measure frequency.
If you input a sine signal to channel 1, follow these steps:
1. Measure FFT Amplitude
1. Input a sine signal to channel 1, and press the “AUTO”
button.
2. Press the “MATH” button to enter the “MATH” menu.
3. Press the “Operation” option button to select “FFT”.
4. Press the “Source” option button to select “CH1”.
5. Press CH1 button to display CH1 menu.
6. Turn the “Time/div” knob to adjust sampling rate (at least
double bigger than frequency of input signal).