User manual

WaveSurfer 3000 Oscilloscopes

sweep: new average = (new data + 4 * old average)/(4 + 1) = 1/5 new data + 4/5 old average

In this way, for sweeps > 4 the importance of the old average begins to decrease exponentially.

NOTE: The number of sweeps used to compute the average is displayed at the bottom of the trace descriptor

box.

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.