Adding and Subtracting Waveforms
and 11402
allow the addition or subtraction of
waveforms without
The
for this lies in the manner
which
samples are taken and
by the mainframe.
plug-in
has
an
in
11401 or
ara taken simultaneously
each sampler. A channel from one plug-m unit maybe added to or subtracted
from that of another
unit
by virtue of this simultaneity.
Thus noise and other signals
to the trigger will be canceled when
in different plug-in units are
Signals
different
a
are sampled at different
times. Signals that are entirely repetitive and related to the
signal
maybe successfully added or
in spite of this. However, signals that
are not
or related to the trigger
not be sampled at the
and may not be displayed
Therefore it is preferable that
signals to
or
be
from different plug-in
common-mode rejection is obtained with a differential amplifier
in unit
hardware subtracts the signals at its two inputs, passing only
Even when using channels from different
compartments, the following
two problems limit the accuracy of
or differences:
waveform in memory is constantly
updated, and therefore
consists of
points that are “older” than others. Although
may
taken simultaneously,
is a chance that a correct sample may
replaced in memory with a newer value before the
is
and displayed.
2
Delay
between channels of different plug-m
due to
cable length
are normally removed by
the
and the
amplifier channel. Samples are still taken
simultaneously, but the display is manipulated to remove time
Signals correlated to the trigger signal
restored
to their
there is no way for signals unrelated
to the
to be corrected with this
technique.
rejection of signals unrelated to the
is not improved by
The solution to both problems is
averaging. The averaging
suppresses all signals and noise unrelated to
trigger.
