HP HP 54600B, User'S And Service Manual

Page: 39 / 183

To trigger on a complex waveform
The difficulty in viewing a complex waveform is triggering on the signal.
Figure 2-3 shows a complex waveform that is not synchronized with the
trigger.
The simplest trigger method is to trigger the oscilloscope on a sync pulse that
is associated with the waveform. See "To trigger the oscilloscope" on page
1–14. If there is no sync pulse, use the following procedure to trigger on a
periodic complex waveform.
1
Connect a signal to the oscilloscope.
2
Set the trigger level to the middle of the waveform.
3
Adjust the Holdoff knob to synchronize the trigger of the
oscilloscope with the complex waveform.
By setting the Holdoff to synchronize the trigger, the oscilloscope ignores the
trigger that results in figure 2-3, and waits for the trigger that results in figure
2-4. Also notice in figure 2-3 that the trigger is stable, but the waveform is
not synchronized with the trigger.
Holdoff operating hints
1 The advantage of digital holdoff is that it is a fixed number. As a result,
changing the time base settings does not affect the holdoff number; so, the
oscilloscope remains triggered. In contrast, the holdoff in analog oscilloscopes
is a function of the time base setting making it necessary to readjust the holdoff
each time you change the time base setting.
2 The rate of change of the holdoff adjustment knob depends on the time base
setting you have selected. If you need a lengthy holdoff setting, increase the
time/div setting on the time base, then make your coarse holdoff adjustment.
Now switch back to the original time/div setting and make the fine adjustment to
reach the exact amount you want.
Operating Your Oscilloscope
To trigger on a complex waveform
2–12