Technical data

44 4000 X-Series Oscilloscopes Advanced Training Guide
3 Advanced Triggering, Search & Navigation, and Segmented Acquisition Labs
Estimate or use the scope’s timing cursors (X1 & X2) to measure the
width of one of the burst of pulses, and also measure the time from the
beginning of one burst of pulses to the beginning of the next burst of
pulses. You should find that the width of each burst is approximately
40 µs, and the time between bursts is approximately 50 µs.
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.
10 Press the [Run/Stop] front panel key to begin repetitive acquisitions
again.
11 Press the [Mode/Coupling] key in the Trigger section of the front panel.
12 Tap the Holdoff softkey twice to bring up the keypad; set to 45.000 µs.