Technical data

Using Trigger Holdoff to Synchronize Acquisitions/Display on Complex Signals A
Agilent InfiniiVision 7000B Series Oscilloscopes Evaluation Guide 73
We can now visually determine how often this signal repeats. But first,
notice that there appears to a narrow “gap” in every 2nd modulation. In
addition, we can see that one modulation has a slightly higher
peak-to-peak voltage than the next modulation. If you use the
oscilloscope’s timing cursors to measure the time between every 2nd
modulation, you will see that this signal repeats approximately every
420 µs.
To establish distinct trigger arm, disarm, and then re-arm points on a
complex signal such as this, there must be a large timing gap between
trigger events. We can create this timing gap by changing the trigger
level away from the 50% level. We can then set the trigger holdoff to a
value less than the repeat time of the signal to establish a stable trigger
point. Let’s try it.
10 Set the trigger level to the approximate 75% level by rotating the Trigger
Level knob until the trigger level is approximately 2.8 V.
11 Press [Mode/Coupling].
12 Press Holdoff; then, set the holdoff value to approximately 375 µs.
13 Press [Run/Stop] to begin repetitive acquisitions again.
The oscilloscope should now trigger on edge crossings of the carrier
signal at the 2.8 voltage level. Triggering will then be disarmed and then
re-armed 375 µs later, which should be during a large “gap” between
every 2nd modulation. The oscilloscope then triggers again on the next
edge crossing of the carrier signal at 2.8 V.