Operator's Manual
amplitude. The most recently acquired waveform has more weight than all the previously acquired ones:
the continuous average is dominated by the statistical fluctuations of the most recently acquired
waveform. The weight of ‘old' waveforms in the continuous average gradually tends to zero (following an
exponential rule) at a rate that decreases as the weight increases.
You determine the importance of new data vs. old data by assigning a weighting factor. Continuous
averaging allows you to make adjustments to a system under test and to see the results immediately.
The formula for continuous averaging is:
new average = (new data + weight * old average)/(weight + 1)
This is also the formula used to compute summed averaging. But by setting a "sweeps" value, you
establish a fixed weight that is assigned to the old average once the number of "sweeps" is reached. For
example, for a sweeps (weight) value of 4:
1
st
sweep (no old average yet): new average = (new data +0 * old average)/(0 + 1) = new data only
2
nd
sweep: new average = (new data + 1*old average)/(1 + 1) = 1/2 new data +1/2 old average
3
rd
sweep: new average = (new data + 2 * old average)/(2 + 1) = 1/3 new data + 2/3 old average
4
th
sweep: new average = (new data + 3 * old average)/(3 + 1) = 1/4 new data + 3/4 old average
5
th
sweep: new average = (new data + 4 * old average)/(4 + 1) = 1/5 new data + 4/5 old average
6
th
sweep: new average = (new data + 4 * old average)/(4 + 1) = 1/5 new data + 4/5 old average
7
th
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 will be displayed in the bottom line of the
trace descriptor label:
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.
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