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3
Advanced Triggering, Search & Navigation, and Segmented Acquisition Labs
When we use the scope's default triggering condition, the scope triggers on
"any" random edge of this signal. In other words, sometimes the scope
triggers on the 1st edge of the burst, sometimes the 11th edge of the burst,
sometimes the 5th edge, etc. An ideal synchronization point would be to
set up the scope so that it always triggers on just the 1st edge of each
burst, rather than a random edge. We can do this using the scope's
"trigger holdoff" capability.
With trigger holdoff, we can instruct the scope to always arm triggering
during the signal idle- time between each burst of pulses. This way the
scope will always trigger on the next rising edge after arming, which will
always be the 1st edge in each burst. And ideal holdoff time to achieve
this would be a trigger holdoff time somewhere between 40 µs (width of
burst) and 50 µs (time between bursts). This may sound confusing, so let's
just do it and see what happens.
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Figure 24 Using the scope's trigger holdoff feature to synchronize on a burst of pulses.
You should now see a synchronized display as shown in
scope triggers on the 1st edge of a burst of pulses (center- screen) and
then disables triggering for 45.00 µs (holdoff time). During this holdoff
time, the scope ignores the 2nd, 3rd, 4th, etc., crossings, and then re- arms
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Press the [Run/Stop] front panel key to begin repetitive acquisitions
again.
Press the [Mode/Coupling] key in the Trigger section of the front panel.
Press the Holdoff softkey; then turn the Entry knob clockwise until the
holdoff value is set to approximately 45.000 µs.
Trigger Point
Next Valid Trigger Event
Holdoff Time
2000 X-Series Oscilloscopes Advanced Training Guide
Figure
24. The
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