46
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
.
Figure 24
Using the scope’s trigger holdoff feature to synchronize on a burst of pulses.
Trigger Point
Next Valid Trigger Event
Holdoff Time
