Using Fft Function - PeakTech 1240 Bedienungsanleitung

13. Using FFT function

The FFT (fast Fourier transform) math function mathematically converts a time-domain waveform into its
frequency components. It is very useful for analyzing the input signal on Oscilloscope. You can match these
frequencies with known system frequencies, such as system clocks, oscillators, or power supplies.
FFT in this oscilloscope can transform 2048 points of the time-domain signal into its frequency components
and the final frequency contains 1024 points ranging from 0Hz to Nyquist frequency.
Taking the FFT operation for example, the operation steps are as follows:
1. Press the Math button and call out the Math menu.
2. Press the H2 button and call out the FFT menu.
3. Press the F1 button to choose CH1 as the source.
4. Press F2 button, the windows item will display at the left of the screen, turn the M knob to select Window,
including Rectangle, Hamming, Hanning and Blackman.
5. Press F3 button to choose the Format, including dB, Vrms.
6. Press F4 button, the zoom window will display at the left of the screen, turn the M knob to zoom in or out
the wave of the multiple including ×1, ×2, ×5, ×10.
13.1. Selecting the FFT Window
The FFT feature provides four windows. Each one is a trade-off between frequency resolution and magnitude
accuracy. What you want to measure and your source signal characteristics help you to determine which
window to use. Use the following guidelines to select the best window.
Type
Rectangle
Description
This is the best type of window for resolving frequencies
that are very close to the same value but worst for
accurately measuring
frequencies. It is the best type for measuring the
frequency spectrum
measuring frequency components near DC.
Use rectangle for measuring transients or bursts where
the signal level before and after the event are nearly
equal. Also, use this window for equal-amplitude sine
waves with frequencies that are very close and for
broadband random noise with a relatively slow varying
spectrum.
the amplitude
of nonrepetitive signals
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Window
of those
and