The subsequent behavior depends on whether the acquisition was initiated
by pressing Single or Run:
•
Single—the analyzer will fill acquisition memory, stop, and display the
results.
•
Run—the analyzer will fill the pre-trigger buffer after drawing a trace.
When the pre-trigger buffer is full, the analyzer repeats the search for a
trigger. If no trigger is found, a free-running trace is displayed, much like
that of an oscilloscope on auto trigger.
In either Auto or Normal mode, the trigger may be missed completely under
certain conditions. This is because the analyzer will not recognize a trigger
event until the pre-trigger buffer is full. Suppose you set the Time/Div knob
to a slow sweep speed, such as 500 ms/div. If the trigger condition always
occurs before the analyzer has filled the pre-trigger buffer, the trigger will not
be found.
Some measurements you want to make will require you to take some action
in the circuit under test to cause the trigger event. Usually, these are
single-shot acquisitions, where you will use the Single key. If you use Normal
mode and wait for the trigger condition indicator to flash before causing the
action in the circuit, the analyzer will always find the trigger condition
correctly.
See chapter 4, “Ensuring Accurate Measurements,” for more information on
the acquisition process and the relationships between time base and sampling
rate.
Trigger Mode versus Trigger Type
The trigger mode (Auto or Normal) is independent of the trigger type (Edge,
Pattern, or Advanced). The mode setting applies for any trigger type.
Making Analyzer Measurements
To define the trigger mode
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