HP 54620A, Руководство пользователя и сервисное руководство

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To define the trigger mode
1
Press
Mode
.
2
Select the mode using the
Trigger Mode
softkeys.
You can select either Normal mode or Auto mode.
Trigger Mode
The trigger mode affects the way in which the analyzer searches for the
trigger. Figure 16 shows the conceptual representation of acquisition
memory. You can think of the trigger event as dividing acquisition memory
into a pre-trigger and post-trigger buffer. The position of the trigger event in
acquisition memory is defined by the time reference point and the delay
setting.
Acquisition Memory
Normal mode In Normal trigger mode, the analyzer has the same
behavior whether the acquisition was initiated by pressing Run/Stop or
Single. The analyzer begins filling the pre-trigger buffer with data. As
soon as that buffer is full, the analyzer will begin searching for the trigger
event, and will flash the trigger condition indicator on the status line to
indicate it is doing so. While searching for the trigger, the analyzer
overflows the pre-trigger buffer, with the first data put into the buffer
being the first pushed out (FIFO).
When the trigger event is found, the analyzer will fill the post-trigger
buffer and display the acquisition memory. If the acquisition was initiated
by
Run/Stop
, the process repeats.
Auto mode The analyzer fills the pre-trigger buffer, then searches for
the trigger event for a predetermined interval. This interval is a function
of the Time/Div setting, but is never less than 40 ms. If no trigger is
found, the analyzer forces a trigger and displays the data as though a
trigger had occurred.
Figure 16
Making Analyzer Measurements
To define the trigger mode
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