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OPERATION
from 10% of maximum
value to 90% of full value. Con-
as well as such triggering
parameters as slope, Icvel, and
versely, the fall time is defined as the time period required
single/continuous
mode. For example, if we know that fall
to fall from 90% of maximum
value to 10% of maximum
time is approximately
lOmsec, we might choose a saw
value.
pling duration
of 15msec, allowing
a certain amount of
margin for error. With a Emsec duration,
the maximum
number of samples we can take is 15,000, since the instru-
Assume we wish to analyze the fall time of a typical pulse
ment can sample at rates up to IMHz.
Above lOOkHz,
like the one shown in Figure 3-29. This pulse has a peak
however, the A/D converter operates with A-bit resolution
amplitude of lOV, and a duration of approximately
30msec.
instead of the lh-bit resolution
in effect for sampling rates
of 1OOkHz and less. Thus, if accuracy is a requirement,
wc
may wish to settle for 1,500 samples, which would give
To properly analyze the fall time, we must choose correct
us a IOfisec sampling
interval.
operating parameters such as sampling interval and rate,
Figure 3-29. Pulse Rise and Fall Times
3-49
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