Math FFT
TDS1000/2000-Series Digital Oscilloscope User Manual 117
To set up the FFT displa y, follow these st eps:
1. Push the MATHMENU butt on.
2. Set the Operation optionto FFT.
3. Select the Ma th FFT Source channel.
In many cases, the oscilloscope can produce a useful FFT spectrum
even if the YT waveform is not triggered. This is especiallytrue if
your signal is periodic or random (noisy).
NOTE. Transient or burst waveforms should be triggered and
positioned as close as possible to ce nter screen.
Nyquist Frequency
The highest frequencythat any real-time digitizing oscilloscope can
measure without errors is one-half the sample rate. This frequency is
called the Nyquist frequency. Frequency information a bove the
Nyquist frequency is undersampled which causes FFT aliasing,
described on page 122.
The math function transforms the ce nter 2048 points of the
time-domain waveform intoan FFT spectrum. The resulting FFT
spectrum contains 1024 points that go from DC (0 Hz) to the Nyquist
frequency.