HP 54750A, User Manual, Page: 237 / 478

Increasing Measurement Accurac y
and Time-Interval Measurement
Increasing Measurement Accuracy
Markers
Y ou can measure a time interval manually using the markers in the
instrument. One advantage of using markers is that you can expand the time
base around the start and stop events of the time interval to be measured,
thus achieving more time resolution than with automatic measurements (you
are not limited by the memory depth). T o see the dierence , set up a pulse
generator for a pulse width of 100 ms and a rise time of 1 ns (or as small as
the pulse generator will allow). Then, measure the width both by using the
instrument's automatic measurement and by using the markers .
Channel-to-channel measurements
T o make channel-to-channel measurements , such as propagation delay , setup
time , or hold time , you must remove any systematic dierences in the delays
between the two acquisition channels and any associated probes or cables .
This is accomplished with the Calibrate and Skew keys (refer to Chapter 4 in
this manual).
Statistics
T o condently predict the reliability of a digital system, you must know
the statistics of its behavior . Singular measurements of setup time , hold
time , propagation delay and skew do not allow you to adequately predict
the probability of errors due to timing violations . However , a design
based on worst-case measurements can be too conservative . A worst-case
measurement does not show how frequently , or under what conditions , the
worst case will occur .
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