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X-Stream Operator’s Manual
WM-OM-E Rev I
217
The instrument resumes averaging when you change the trigger mode back to NORM/AUTO.
You can reset the accumulated average by pushing the CLEAR SWEEPS button or by changing an
acquisition parameter such as input gain, offset, coupling, trigger condition, timebase, or bandwidth
limit. The number of current averaged waveforms of the function, or its zoom, is shown in the
acquisition status dialog. When summed averaging is performed, the display is updated at a
reduced rate to increase the averaging speed (points and events per second).
Continuous Averaging
Continuous Averaging, the default setting, is the repeated addition, with unequal weight, of
successive source waveforms. It is particularly useful for reducing noise on signals that drift very
slowly in time or 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.
The formula for continuous averaging is
new average = (new data + weight * old average)/( 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:
Summary of Contents for DDA-3000A
Page 1: ...LECROY X STREAM OSCILLOSCOPES O P E R AT O R S M A N U A L SEPTEMBER 2006 ...
Page 18: ...16 WM OM E Rev I BLANK PAGE ...
Page 64: ...62 WM OM E Rev I icon in Channels dialog zooms one trace zooms all displayed traces ...
Page 80: ...78 WM OM E Rev I 4 Select a language 5 Click Next when the Wizard appears ...
Page 81: ...X Stream Operator s Manual WM OM E Rev I 79 6 Select Complete setup ...
Page 157: ...X Stream Operator s Manual WM OM E Rev I 155 ...
Page 170: ...168 WM OM E Rev I 5 Read the status information in line StatusDescription ...
Page 214: ...212 WM OM E Rev I Delay Parameter Find Range selected ...
Page 263: ...X Stream Operator s Manual WM OM E Rev I 261 ...
Page 284: ...282 WM OM E Rev I ...
Page 285: ...X Stream Operator s Manual WM OM E Rev I 283 Using a Surface Plot Excel Example 5 ...
Page 324: ...322 WM OM E Rev I ...