Teledyne Lecroy WaveSurfer 3000, Руководство оператора, Страница: 62 / 97

WaveSurfer 3000 Oscilloscopes
Set Up Averaging
To quickly set up Continuous Averaging (only), access the Channel setup dialog and enter the number of sweeps to
average in Averaging. The valid range is 1 to 1,000,000 sweeps.
To apply Continuous or Summed Averaging as a Math function:
1. Follow the usual steps to set up a math fuction , selecting Average from the Basic Math submenu.
2. On the Average right-hand dialog, choose Summed or Continuous .
3. Touch Sweeps and provide a value. The valid range is 1 to 1,000,000 sweeps.
FFT
For a large class of signals, you can gain greater insight by looking at spectral representation rather than time
description. Signals encountered in the frequency response of amplifiers, oscillator phase noise and those in
mechanical vibration analysis, for example, are easier to observe in the frequency domain.
If sampling is done at a rate fast enough to faithfully approximate the original waveform (usually five times the highest
frequency component in the signal), the resulting discrete data series will uniquely describe the analog signal. This is of
particular value when dealing with transient signals because, unlike FFT, conventional swept spectrum analyzers cannot
handle them.
Because of its versatility, FFT analysis has become a popular analysis tool. However, some care must be taken with it. In
most instances, incorrect positioning of the signal within the display grid will significantly alter the spectrum, producing
effects such as leakage and aliasing that distort the spectrum.
An effective way to reduce these effects is to maximize the acquisition record length. Record length directly conditions
the effective sampling rate of the oscilloscope and therefore determines the frequency resolution and span at which
spectral analysis can be carried out.
Set Up FFT
1. Follow the usual steps to set up a math function , selecting FFT from the Frequency Analysis submenu.
2. Open the FFT right-hand dialog.
3. Check the Suppress DC box to make the DC bin go to zero. Otherwise, leave it unchecked.
4. Choose an Output type .
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