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Math FFT

TDS1000/2000-Series Digital Oscilloscope User Manual

117

To set up the FFT display, follow these steps:

1. Push the MATH MENU button.

2. Set the Operation option to FFT.

3. Select the Math FFT Source channel.

In many cases, the oscilloscope can produce a useful FFT spect rum

even if the YT waveform is not triggered. This is especially true if

your signal is periodic or random (noisy).

NOTE. Transient or burst wav eforms should be triggered and

positioned as close as possible to center screen.

Nyquist Frequency

The highest frequency that any real-time digitizing oscilloscope can

measure without errors is one-half the sample ra te. This frequency is

called the Nyquist frequency. Frequency information above the

Nyquist frequency is undersampled which causes FFT aliasing,

described on page 122.

The math function tra nsforms the center 2048 points of the

time-domain waveform into an FFT spectrum. The resulting FFT

spectrum contains 1024 points that go from DC (0 Hz) to the Nyquist

frequency.

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Tektronix TDS1000- Manuale Utente Pagina 135