LeCroy DDA 7 Zi series, Руководство оператора

Страница: 143 / 544

Operator's Manual
WP700Zi-OM-E-RevA
142
For example,
x
acceleration can be entered as M/S2 for meters per second squared
x
volts seconds can be entered as V.S.
In some cases, the units entered may be converted to simple units. For example entering V.A will display W
(watts)
Rescaling Setup
1. Touch Math Math Setup on the menu bar.
2. Touch a math function trace tab F1 through Fx [The number of math traces available depends on the
software options loaded on your scope. See Specifications.]
3. Touch the single function button.
4. Touch inside the Source1 data entry field and select a source: channel, math trace, memory location.
5. Touch inside the Operator1 data entry field and select Rescale from the Functions category.
6. In the dialog on the right, touch the Rescale tab.
7. Touch inside the First multiply by: checkbox and enter a value for a , the multiplication factor.
8. Touch inside the then add: data entry field and enter a value for b , the additive constant.
9. Touch inside the Override units checkbox to disregard the source waveform's units.
Averaging Waveforms
Summed vs. Continuous Averaging
For Summed averaging, you specify the number of acquisitions to be averaged. The averaged data is updated at
regular intervals and presented on the screen.
On the other hand, Continuous averaging (the system default) helps to eliminate the effects of noise by
continuously acquiring new data and adding the new waveforms into the averaging buffer. 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.
Note: Continuous Averaging is accessible from the channel "Vertical Adjust" dialog under "Pre-Processing," and
from the math function menu.
Summed Averaging
Summed Averaging is the repeated addition, with equal weight, of successive source waveform records. If a
stable trigger is available, the resulting average has a random noise component lower than that of a single-shot
record. Whenever the maximum number of sweeps is reached, the averaging process stops.
An even larger number of records can be accumulated simply by changing the number in the dialog. However, the
other parameters must be left unchanged or a new averaging calculation will be started. You can pause the
averaging by changing the trigger mode from NORM/AUTO to STOP. 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)