Triggering 4
InfiniiVision 7000B Series Oscilloscopes User’s Guide 107
Trigger Holdoff
Trigger Holdoff Operating Hints
Holdoff keeps a trigger from occurring until after a certain amount of time
has passed since the last trigger. This feature is valuable when a waveform
crosses the trigger level multiple times during one period of the waveform.
Without holdoff, the oscilloscope could trigger on each of the crossings,
producing a confusing waveform. With holdoff set correctly, the
oscilloscope always triggers on the same crossing. The correct holdoff
setting is typically slightly less than one period. Set the holdoff to this
time to generate a unique trigger point. This action works even though
many waveform periods pass between triggers, because the holdoff circuit
operates on the input signal continuously.
Changing the time base settings does not affect the holdoff number. 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.
With Agilent’s MegaZoom technology, you can press [Stop], then pan and
zoom through the data to find where it repeats. Measure this time using
the cursors, then set the holdoff.
To set holdoff
1 Press the [Mode/Coupling] key; then, press the Holdoff softkey.
2 Turn the Entry knob to increase or decrease the trigger holdoff
time shown.
Holdoff sets the amount of time that the oscilloscope waits before
re- arming the trigger circuitry. Use Holdoff to stabilize the display of
complex waveforms.
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